Method and apparatus for guiding medical care based on sensor data from the gastrointestinal tract

Abstract

To provide a method and an apparatus for guiding medical care based on sensor data from the gastrointestinal tract.SOLUTION: An apparatus includes: an elongated body having a length configured for insertion into the stomach of a subject; at least one pair of electrodes positionable for placement within the stomach; a controller which detects a change in conductivity or impedance of gastric contents measured between the pair of electrodes after it is in electrical communication with the electrodes and addition elements are inserted in the stomach orally or nasally through the elongated body, and determines placement of the elongated body in the subject; a display which determines a gastric residual volume (GRV) of the stomach contents based on the measured conductivity or impedance of the gastric contents, and provides real-time GRV data; and at least one sensor which is placed near along the length of the electrodes.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 164,488, filed May 20, 2015, U.S. Provisional Patent Application No. 62 / 258,329, filed November 20, 2015, U.S. Provisional Patent Application No. 62 / 185,697, filed June 28, 2015, and U.S. Provisional Patent Application No. 62 / 312,257, filed March 23, 2016, each of which is incorporated by reference in its entirety for all purposes.

[0002] The present invention relates to the measurement of gastric volume, gastric emptying, reflux and feeding tube positioning / monitoring. [Background technology]

[0003] All publications, patents, or patent applications cited in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

[0004] It is widely recognized that adequate nutrition is important for recovery from acute illness. Nutritional supplementation is often required for patients in intensive care units (ICUs), wards, and at home. According to Non-Patent Document 1, which is incorporated herein by reference in its entirety for all purposes, the results of 14 randomized trials showed that randomly selected ICU patients who received early (vs. delayed) enteral nutrition had a 41% lower mortality rate and 27% fewer infectious complications. According to Non-Patent Document 2, which is incorporated herein by reference in its entirety for all purposes, patients who received early enteral nutrition had a shorter ICU stay (4.7 days vs. 8.5 days), shorter ventilator time (3.0 days vs. 6.0 days), and reduced mortality (5.5% vs. 38.9%). According to non-patent literature 3, which is incorporated herein by reference in its entirety for all purposes, early enteral feeding is associated with a 20% reduction in ICU mortality and a 25% reduction in hospital mortality, but was accompanied by an 18% increase in the incidence of pneumonia. The Society of Critical Care Medicine (SCCM) and American Society of Parenteral and Enteral Nutrition (ASPEN) guidelines recommend early nutritional supplementation.

[0005] Although guidelines recommend early patient nutrition, many acute care patients are unable to become nutritionally supported, as evidenced by a study by Physicians for Disease Control and Prevention (2011) 4:1311-1323, which is incorporated herein by reference in its entirety for all purposes, showing that up to 62.8% of ICU patients show signs of intolerance to nutrition, which is subsequently associated with higher mortality (31% vs. 16%, p<0.001).

[0006] Clinicians fear feeding patients too quickly because of the risk of aspirating stomach contents into the lungs. Pulmonary aspiration is widespread and common in acute care patients. For example, 62% of elderly hospitalized patients aspirate, according to 5, which is incorporated herein by reference in its entirety for all purposes. Similarly, 38% of stroke patients aspirate, according to 6, which is incorporated herein by reference in its entirety for all purposes, and in more than two-thirds of these patients aspiration goes unnoticed by the clinicians treating them. Another study, 7, which is incorporated herein by reference in its entirety for all purposes, found that 50% of stroke or brain injury patients aspirate.

[0007] Aspiration of these stomach contents into the lungs can cause serious consequences such as chemical pneumonitis, pneumonia, and even death due to respiratory arrest. For example, according to "Pneumonia: A Guide to the Treatment of Stroke in Elderly Hospitals" (2009), which is incorporated herein by reference in its entirety for all purposes, aspiration pneumonia occurs in 19% of elderly hospitalized patients and 44% of nursing home patients. According to "Pneumonia: A Guide to the Treatment of Stroke in Elderly Hospitals" (2009), which is incorporated herein by reference in its entirety for all purposes, stroke patients who aspirate are 6.95 times more likely to develop pneumonia than those who do not aspirate. Because pneumonia and pneumonitis (caused by gastric juices and the presence of certain substances) are associated with similar clinical findings, pneumonitis (i.e., sterile inflammation) is often misdiagnosed as pneumonia. Furthermore, sterile pneumonitis can trigger the onset of pneumonia. Thus, according to "Pneumonia: A Guide to the Treatment of Stroke in Elderly Hospitals" (2009), which is incorporated herein by reference in its entirety for all purposes, 40% of cases of suspected pneumonia in nursing home residents are classified as pneumonitis based on definite or suspected aspiration events. According to non-patent literature 11, which is incorporated herein by reference in its entirety for all purposes, generally, a high mortality rate (>50%) is associated with aspiration pneumonia and pneumonitis.

[0008] Many acute care patients are at higher risk of developing complications from aspiration due to difficulty in swallowing, also known as dysphagia, impaired gag reflex, and / or immunodeficiency. These include patient populations such as the elderly, heavily sedated, and those with traumatic brain injury, brain tumors, or head and neck cancer. According to Non-Patent Document 11, the following are risk factors for aspiration: gastroesophageal acid reflux, physiological attacks with increasing age, cerebrovascular accidents, confusion, gastroparesis, endotracheal intubation, naso-oral intubation, enteral feeding, anesthesia, supine position, and seizures.

[0009] Among patients who are enterally fed by administration (continuous or intermittent) of a tube-feed formula into the stomach via an orogastric or (more commonly) nasogastric feeding tube, there is an increased risk of aspiration of gastric contents when gastric emptying into the small intestine is impaired. The most common cause of impaired or delayed gastric emptying is gastric ileus (i.e., gastric dysmotility). When patients are enterally fed by continuous administration of a tube-feed formula through a feeding tube, clinicians (nurses and doctors) typically prevent aspiration by periodic measurement of the "Gastric Residual Volume" or GRV. Typically, GRV is calculated by periodically connecting a large syringe to the "orogastric or nasogastric feeding tube" and aspirating to remove stomach contents, then measuring the volume of contents removed thereby. Enteral feeding is often temporarily stopped if the measured GRV is greater than some (arbitrarily determined) threshold (e.g., 200 mL or 300 mL).

[0010] This fear of aspiration leads clinicians to reduce the amount of food patients eat. For example, according to 12, which is incorporated herein by reference in its entirety for all purposes, less than 44% of ICU patients receive nutrition during the first 3-5 days after admission to the unit. According to 13, which is incorporated herein by reference in its entirety for all purposes, enteral nutrition in surgical ICU patients is initiated on average after 57.8 hours.

[0011] Gastric contents are normally acidic. When acidic gastric contents enter the esophagus, it can result in acid reflux symptoms such as heartburn, acid indigestion, and burning pain. If acid reflux progresses further up the esophagus, it can enter the trachea and lungs, resulting in pulmonary aspiration.

[0012] Thus, clinicians want to feed patients early, but are concerned that patients may be at risk for reflux. Unfortunately, there are no definitive indications to help clinicians determine whether a patient will develop or be at risk for reflux. Patient populations appear to be quite heterogeneous in whether patients develop reflux and what magnitude of reflux these patients develop. In one study by 14, which is incorporated herein by reference in its entirety for all purposes, 22 of 24 mechanically ventilated pediatric ICU patients (91%) demonstrated reflux. In this same study by 14, pneumonia patients demonstrated more episodes (6.5) and longer total reflux times (50 minutes) compared to non-pneumonia patients (1 episode, 3 minutes). In another study by Nind, 15 which is incorporated herein by reference in its entirety for all purposes, 6 of 11 mechanically ventilated adult ICU patients (55%) experienced 25 reflux episodes as measured by impedance monitoring. Nind further noted how significant the interpatient variability was, with one patient experiencing 13 reflux episodes and five patients experiencing reflux episodes. The incidence in the overall ICU population is likely to be higher, as Nind's study consisted of a "healthier" population already receiving enteral nutrition, and was recorded only 1 hour prior to feeding and 5 hours during nasogastric feeding. In another study by Solana, 16 (hereafter referred to as Solana), which is incorporated herein by reference in its entirety for all purposes, 30 of 36 (83%) mechanically ventilated ICU patients aged 1 month to 7 years experienced 338 reflux episodes, with a mean of 9.3 episodes per patient (SD 16, mean 2, range 1-79). Solana also described how impedance measurements revealed that 16 of the 338 episodes reached the upper pathway. The incidence is likely higher because no nutritional supplementation was administered during the time frame of the measurements. [Prior art documents] [Non-patent literature]

[0013] [Non-Patent Document 1] Heyland et al, “Review of ICU Early vs. Delayed Feeding Randomized Trials” JPEN,2003;27:355-73 [Non-Patent Document 2] Woo et al., “Early vs delayed enteral nutritI / On in critically ill medical patients.” Nutr Clin Pract. 2010 Apr:25(2):205-11, [Non-Patent Document 3] Artinian et al. “Effects of early enteral feeding on the outcome of critically ill mechanically ventilated medical patients.” Chest. 20(16 April 29(4 ):960-7 [Non-Patent Document 4] JC Moniejo. “Enteral nutritI / On-related gastrointestinal complicatI / Ons in critically ill patients: a multicenter study.” Crit Care Med. 1999 Aug;27(8): 1447-53, [Non-Patent Document 5] Murry et al.. “the significance of ACCUMULATED oropHaryngeal secretI / Ons and swallowing frequency in predicting aspiratI / On.” DyspHagia. 1996 Spring: 11(2):99-103 [Non-Patent Document 6] Daniels et al. “AspiratI / On in patients w ith acute stroke.” Arch PHys Med Rehabil. 1998 Jan;79( 1 ): 14-9

Non-Patent Document 7

Non-Patent Document 8

Non-Patent Document 9

Non-Patent Document 10

Non-Patent Document 11

[0014] Most commonly, feeding tubes are small bore (outer diameter 5Fr to 12Fr) plastic tubes. Very small bore tubes are inherently very flexible and therefore difficult to pass. Thus, very small tubes often have a fine wire stiffener or stylet placed in the lumen. The stiffening wire facilitates intubation and is removed once the tube is properly placed inside the stomach. Most commonly, feeding tubes are inserted through one of the nostrils. The tube is gradually advanced through the nasopharynx, oropharynx, hypopharynx, and esophagus, finally leading to placement of the distal end of the tube in the lumen of the stomach. Sometimes, the tube advances through the hypopharynx, through the pharynx, and into the trachea rather than into the esophagus. If the feeding tube has a wire stylet and advances all the way down the tracheobronchial tree and into the distal subsegmental bronchioles, it may then puncture the lung parenchyma and cause a pneumothorax or even a bronchopleural fistula. Introduction of a feeding tube into the airway (trachea, mainstream bronchi, or segmental bronchi) can result in catastrophic outcomes, including pneumonitis, pneumonia, or even death, even when the tube is not reinforced with a stylet or advanced into the distal tracheobronchial tree. Because clinicians are aware of the risks of inadvertently introducing a feeding tube into the airway, many institutions mandate radiographic confirmation that the tip of the feeding tube is properly placed in the stomach (or small intestine) before initiating tube feeding.

[0015] Enteral nutrition via a feeding tube allows patients to receive nutrition or provide supplemental nutrition when they are unable to take nutrition through the mouth and swallow safely. The current standard of care calls for regular monitoring of post-feeding gastric residual volume (GRV). GRV is the volume of residual gastric contents remaining in the stomach after a period of time has elapsed after feeding via a feeding tube. Of concern is that high GRV values ​​may indicate pulmonary aspiration, a serious problem that can lead to pneumonia with serious consequences. Typically, these GRV measurements are taken every 4-6 hours, and especially during the first few days of enteral nutrition to allow for acceptance of the feeding tube.

[0016] The current standard method of measuring GRV is via suction from a nasogastric tube. There are several problems with the current method of measuring GRV, including:

[0017] 1) Aspiration of contents to measure GRV is burdensome for nursing staff. Even for those skilled in the procedure, the entire procedure takes 5 minutes. This is repeated every 4-6 hours for each patient who requires GRV monitoring.

[0018] 2) Manual mechanical aspiration of gastric contents may increase the incidence of pulmonary aspiration.

[0019] 3) Manual means of measuring GRV, whether by syringe aspiration, low-wall aspiration, gravity drainage or other methods, lack standardization and introduce error into the measurement.

[0020] A solution that addresses these and other problems of measuring a patient's GRV is needed. [Means for solving the problem]

[0021] The present invention is a GRV measurement device and method for measuring gastric content volume by the introduction of at least one additive component that is dispersed and then changes a physical (chemical, electrical, thermal, mechanical, optical, etc.) property in the gastric contents to a measurable extent within the gastric contents. The degree of change in this physical property and / or the rate of return to a previous state can be used to measure the patient's GRV. The smaller the GRV, the greater the magnitude of the change is likely to be and the slower the rate of change of this physical property back to the baseline. The larger the GRV, the smaller the magnitude of the change is likely to be and the more rapid the rate of change of this physical property back to the baseline. The measured GRV can also be used to automatically or semi-automatically control the patient's feeding rate and / or amount and / or frequency to properly nourish the patient but prevent complications. The physical property(ies) can also be used to detect that the feeding catheter or tube is in the correct position (i.e., stomach vs. lungs or esophagus). It is noted that the term "GRV" refers to Gastric Residual Volume or Gastric Emptying or Gastric residual feed. Gastric emptying as an index of stomach volume, or gastric emptying rate, either of which indicates when a patient needs refilling. The embodiments of the GRV measuring device described herein are capable of measuring the residual volume of gastric contents, or gastric emptying or gastric refilling. In particular, the embodiments of the GRV measuring device described herein are capable of measuring the percentage of food in the stomach (food vs. gastric fluids), the amount of gastric contents remaining, and / or food remaining in the stomach.

[0022] One embodiment of a device for measuring remaining gastric content comprises an elongated tube defining at least one lumen therethrough, a medium having one or more GRV indicators in fluid communication with the at least one lumen, one or more sensors disposed at or near a distal end of the elongated tube, the one or more sensors configured to measure a change in a parameter of the GRV indicator, and a controller coupled to the one or more sensors, the controller measuring the GRV based on the change in the parameter of the GRV indicator.

[0023] In general use, such devices may be used to measure GRV by placing an elongated tube defining at least one lumen therethrough into a body lumen, introducing a medium having one or more GRV indicators through the at least one lumen, and sensing the one or more GRV indicators via one or more sensors located at or near the distal end of the elongated tube, The one or more GRV indicators are monitored for changes in a parameter of the GRV indicator, and the GRV of the stomach may be determined based on the change in the parameter of the GRV indicator.

[0024] Various exemplary embodiments will be described in detail below with reference to the accompanying drawings. [Brief description of the drawings]

[0025] [Figure 1A] FIG. 1A is a schematic diagram of a feeding tube attachment device according to an exemplary embodiment. [Figure 1B] FIG. 1B is a schematic diagram of a feeding tube attachment device according to an exemplary embodiment. [Figure 1C] FIG. 1C is a schematic diagram of a feeding tube attachment device according to an exemplary embodiment. [Diagram 2] FIG. 2 is a flow chart of an exemplary feeding tube attachment method and device. [Diagram 3]FIG. 3 is a schematic diagram of a user interface screen of the exemplary monitor of FIG. [Figure 4] FIG. 4 is a schematic diagram of a user interface screen of the exemplary monitor of FIG. [Diagram 5] FIG. 5 is a schematic diagram of a user interface screen of the exemplary monitor of FIG. [Figure 6] FIG. 6 is a schematic diagram of a feeding tube attachment device according to another exemplary embodiment. [Figure 7] FIG. 7 is a schematic diagram of a feeding tube attachment device according to another exemplary embodiment. [Figure 8] FIG. 8 is a schematic diagram of a gastric motility assessment device according to an exemplary embodiment. [Figure 9] FIG. 9 is a schematic diagram of a gastric content measurement device according to an exemplary embodiment. [Figure 10] FIG. 10 is a flow chart of an exemplary method and apparatus for measuring gastric residual volume. [Figure 11] FIG. 11 is a schematic diagram of a reflux monitoring device according to an exemplary embodiment. [Figure 12] FIG. 12 is a flow chart of an exemplary method and apparatus for reflux monitoring. [Figure 13] FIG. 13 is a schematic diagram of an exemplary impedance measurement conductive ink approach. [Figure 14A] FIG. 14A is a schematic diagram of an exemplary tube connector. [Figure 14B] FIG. 14B is a schematic diagram of an exemplary tube connector. [Figure 15] FIG. 15 is a schematic diagram of a user interface screen of the exemplary monitor of FIG. [Figure 16] FIG. 16 is a schematic diagram of a user interface screen of the exemplary monitor of FIG. [Figure 17] FIG. 17 is a flow chart of an exemplary algorithmic method and apparatus for determining the presence of reflux. [Figure 18]FIG. 18 is an impedance data chart showing a liquid backflow event. [Figure 19] FIG. 19 is an impedance data chart showing a gas backflow event. [Figure 20] FIG. 20 is an impedance data chart displaying swallowing incidents. [Figure 21] FIG. 21 is an impedance data chart displaying swallowing and liquid regurgitation events. [Figure 22A] FIG. 22A is a schematic diagram of an impedance and conductivity measurement device according to an exemplary embodiment. [Figure 22B] FIG. 22B is a schematic diagram of an impedance and conductivity measurement device according to an exemplary embodiment. [Figure 22C] FIG. 22C is a schematic diagram of an impedance and conductivity measurement device according to an exemplary embodiment. [Figure 22D] FIG. 22D is a schematic diagram of an impedance and conductivity measurement device according to an exemplary embodiment. [Figure 22E] FIG. 22E is a schematic diagram of an impedance and conductivity measurement device according to an exemplary embodiment. [Figure 23] FIG. 23 is a flow chart of an exemplary GRV measurement method and apparatus. [Figure 24] FIG. 24 is a flow chart of an exemplary method and apparatus for determining feeding tube position by impedance measurements. [Diagram 25] FIG. 25 is a flow chart of an exemplary method and apparatus for determining feeding tube position by local conductivity measurements. [Figure 26] FIG. 26 shows one embodiment of a GRV measurement device inside the human stomach. [Figure 27] FIG. 27 shows the stomach into which a substance containing a concentration of a GRV indicator is introduced. [Figure 28] FIG. 28 is a graph of the temperature of the stomach contents over time after a bolus of cold substance is introduced into the stomach. [Figure 29]FIG. 29 is a graph of the concentration or pH of the GRV indicator over time after introduction into the stomach. [Diagram 30] FIG. 30 is a graph of the temperature of the stomach contents over time as sensed by the sensors after multiple boluses of cold substance have been introduced into the stomach. [Diagram 31] FIG. 31 shows an embodiment of a GRV measurement device in which the sensor is outside the stomach. [Diagram 32] FIG. 32 shows one embodiment of a GRV measurement device in which sensors are placed along the length of a catheter or tube. [Diagram 33] FIG. 33 shows one embodiment of a GRV measurement device with sensors in various positions. [Diagram 34] FIG. 34 shows one embodiment of a GRV measurement device with sensors in various positions. [Diagram 35] FIG. 35 shows one embodiment of a GRV measurement device separate from the feeding tube. [Diagram 36] FIG. 36 illustrates one embodiment of a GRV measurement device in which the GRV measurement device is inserted through a feeding tube. [Figure 37] FIG. 37 shows how the sensors of the GRV measurement device can be placed in various locations relative to the feeding tube. [Figure 38] FIG. 38 shows how the sensors of the GRV measurement device can be placed in various locations relative to the feeding tube. [Figure 39] FIG. 39 illustrates one embodiment of the present invention where there is at least one transmitter and / or receiver that tracks the location of the device within the stomach and / or stomach contents. [Diagram 40] FIG. 40 illustrates one embodiment of the present invention where there is at least one transmitter and / or receiver that tracks the location of the device within the stomach and / or stomach contents. [Diagram 41] FIG. 39 illustrates one embodiment of the present invention where there is at least one transmitter and / or receiver that tracks the location of the device within the stomach and / or stomach contents. [Diagram 42] FIG. 42 shows one embodiment of a transdermal GRV measurement device. [Diagram 43] FIG. 43 shows one embodiment of a transdermal GRV measurement device. [Diagram 44] FIG. 44 shows one embodiment of a GRV measurement device using a percutaneous jejunostomy tube. [Diagram 45] FIG. 45 shows one embodiment of a GRV measurement device. [Figure 46] FIG. 46 shows one embodiment of a GRV measurement device. [Figure 47] FIG. 47 shows one embodiment of a GRV measurement device. [Figure 48] FIG. 48 shows one embodiment of a GRV measurement device. [Figure 49] FIG. 49 shows one embodiment of a GRV measurement device. [Figure 50] FIG. 50 shows one embodiment of a device based on the physical properties of the GRV and gastric penetration monitored continuously or intermittently. [Figure 51] FIG. 51 shows one embodiment of the device. [Figure 52] FIG. 52 is a block diagram of a data processing system that may be used in any embodiment of the present invention. [Figure 53] FIG. 53 shows another embodiment of the device. [Figure 54] FIG. 54 shows another embodiment of the device. [Figure 55] FIG. 55 shows the conductivity of various media as the percentage of gastric acid increases. [Figure 56] FIG. 56 shows the pH and conductivity at various anatomical locations in the pig. [Figure 57] FIG. 57 shows the conductivity and conductivity variation at various anatomical locations before and after nutritional supplementation. [Figure 58] FIG. 58 shows the conductivity and conductivity variation at various anatomical locations before and after nutritional supplementation. [Figure 59]FIG. 59 shows pH and pH variation at various anatomical locations. [Figure 60] FIG. 60 shows the pH and pH variations at various anatomical locations. [Figure 61] FIG. 61 shows the conductivity and pH before and after nutritional supplementation. [Figure 62] FIG. 62 shows one embodiment of a GRV measurement device having a retention balloon. [Figure 63] FIG. 63 shows a GRV measurement device with a pH sensor. [Figure 64] FIG. 64 shows a GRV measurement device with a pH sensor. [Figure 65] FIG. 65 shows a cross section of the feeding tube of the GRV measuring device. [Figure 66] FIG. 66 shows one embodiment of a GRV measurement device. [Figure 67] FIG. 67 shows one embodiment of a GRV measurement device. [Figure 68] FIG. 68 shows one embodiment of a GRV measurement device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] For ease of explanation, an exemplary embodiment is described below with reference to the accompanying drawings in the context of placing a feeding tube, assessing gastric motility and monitoring reflux in an acute care patient.

[0027] Below is a table of contents of some of the embodiments specifically mentioned in the detailed description.

[0028] I. Feeding Tube Placement Systems and Devices A. Using acoustic sensors to determine tube position B. Using a magnetic field sensor to determine the tube position II. Motility Measurement Systems and Devices A. Measuring Motility Using Acoustic Sensors B. Using a temperature sensor to measure the remaining amount of stomach contents C. Measuring remaining gastric contents using bioelectrical impedance D. Measuring Motility Using Impedance Sensors III. Backflow Measurement Systems and Devices A. Reflux Measurement System B. Feeding Tube Design C. Monitor cable design D. Suction and Feeding Pump Connector Design E. Monitor design IV. Impedance-Based Algorithm A. Collecting Data for the Algorithm B. Fluid Backflow Detection Algorithm C. Gas Reflux or Burp Detection Algorithm D. Swallowing Detection Algorithm E. Mixed State Detection Algorithm F. Smart Alarm Detection Algorithm V. Aspiration prevention interventions A. Prevention of aspiration by aspiration of gastric contents B. Preventing aspiration by adjusting the feeding pump C. Prevention of aspiration due to esophageal obstruction VI. Impedance-based local GRV measurement VII. Tube localization via impedance measurements VIII. Tube localization via local conductivity measurements

[0029] The present invention will be described more fully below with reference to the accompanying drawings, in which various embodiments are shown. However, the present invention can be embodied in many different forms and should not be construed as being limited to the example embodiments described in this document. These example embodiments are truly examples and are capable of numerous implementations and variations that do not require the details proposed in this document. It should also be emphasized that although details of alternative examples are described in this document, the list of such alternatives is not exhaustive. Moreover, consistency of details between various examples should not be construed as requiring such details. It is not feasible to list each possible variation for each feature described in this document. The language of the claims should be consulted in determining the requirements of the present invention.

[0030] In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. Like elements are numbered like throughout.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms include the plural forms as well, unless otherwise clearly indicated in the context. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as " / ".

[0032] It will be understood that the terms "first, second, third, etc." may be used in this document to describe various elements, components, regions, layers, and / or portions, but these elements, components, regions, layers, and / or portions should not be limited to these terms. Unless otherwise indicated in the text, these terms are used only to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion, for example, as a naming convention. Thus, a first element, component, region, layer, and / or portion discussed below in one section of the specification can be referred to as a second element, component, region, layer, and / or portion in another section of the specification or in the claims, without departing from the scope of the teachings of the present invention. Also, in some cases, the claims can refer to "first" and "second" to distinguish different claimed elements from each other, even if the specification does not use the terms "first", "second", etc.

[0033] The terms "comprise" and / or "comprising" or "include" and / or "including" as used herein are open-ended and inclusive of stated features, regions, integers, steps, operations, elements and / or components, but do not preface the presence or addition of one or more other features, regions, integers, steps, operations, elements, components and / or groups thereof.

[0034] When an element is referred to as being "connected" or "coupled" to or on another element, it is possible that it is directly connected or coupled to or on the other element, or that there are intervening elements present. Other words used to describe relationships between elements should be interpreted in an analogous manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). However, the term "contact" as used in this document refers to direct contact (i.e., touching), unless otherwise indicated in the context.

[0035] Spatial terms such as "below," "below," "below side," "on," "above," and the like may be used in this document for ease of description to describe the relationship of one element or feature to another element or feature as illustrated in the drawings. It will be understood that the spatial terms are intended to encompass various orientations of the device in use or operation in addition to the orientation depicted in the drawings. For example, if the device in the drawings is rotated, an element described as "below" or "below" another element or feature would then be oriented "above" the other element or feature. Thus, the term "below," as used in relation to a relative orientation, may include both an orientation above and below in the real world. The device may be oriented in another way (e.g., rotated 90 degrees or oriented in another way) without affecting the relationships described by the spatial terms.

[0036] Unless otherwise defined, all terms (including technical and scientific words) used in this document have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted to have a meaning consistent with their meaning in the context of the relevant art and / or this application, and will not be interpreted idealistically or overly formally unless expressly defined as such in this document.

[0037] Feeding tube placement system and device Determining the placement of a feeding tube is important in many clinical settings. For all patients receiving a feeding tube, it is critical that the tube be placed in the stomach and not the lungs. According to Thomas.et al, “ConfirmatI / On of nasogastric tube placement by colorimetric indicator detectI / On of carbon dI / Oxide: a preliminary report,” J Am Coll Nutr, 1988 Apr, 17(2)195-7 (hereinafter “Thomas”), which is incorporated herein by reference in its entirety, inadvertent insertion of feeding tubes into the trachea or pulmonary airways accounts for 0.3-15% of all insertions. Insertion of a feeding tube into the lungs is associated with a high risk of lung tissue perforation and pneumonia. The described embodiments are designed to ensure that the feeding tube is properly placed in the stomach and not in the trachea, bronchi or lungs.

[0038] The proposed embodiments may be utilized with all types of feeding tubes including many different sizes (e.g., ranging from 6Fr to 18Fr) and feeding tube types including, but not limited to, Levin feeding tubes, Salem Sump style feeding tubes, Dobhobb feeding tubes, Keofeed feeding tubes, small bore feeding tubes, pediatric feeding tubes, and nasojejunal feeding tubes.

[0039] Determining tube position using acoustic sensors In an exemplary embodiment for determining tube placement, a sensor that measures acoustic signals is used to determine where the tube is placed in the body. Acoustic sensors can measure vibrations of various frequency ranges and types, including but not limited to vibrations coupled to the audible frequency range (20-20,000 Hz). In an exemplary embodiment, a piezoelectric sensor is used to measure the acoustic signals. Numerous other exemplary sensors can be used to measure the acoustic signals, including but not limited to electrets, capacitors, piezoelectric crystals, piezoelectric ceramics, piezoelectric membranes, fiber optic microphones, or contact accelerometers. FIGS. 1A-1C illustrate an exemplary feeding tube device with an acoustic sensor. In this exemplary embodiment, a patient uses a feeding tube 102 to receive enteral nutrition into a stomach 103. Enteral nutrition is administered by an enteral feeding pump 116 and delivered via an enteral feeding pump tube 114 and a tube conductor 112. The feeding tube 102 incorporates an acoustic sensor 104. In an exemplary embodiment, the acoustic sensor 104 is located at the distal end of the tube. The acoustic sensor 104 may be designed to detect certain vibrations, such as audible, inaudible, or both audible and inaudible sounds. In an exemplary embodiment, the acoustic sensor 104 is connected through a wire disposed within a second lumen that runs the length of the feeding tube 102. In some embodiments, the wire is embedded in the wall of the feeding tube 102. In some embodiments, the acoustic sensor 104 and the wire are connected to a single separate component that is located within the main lumen of the feeding tube 102. The separate component is removed after the tube is inserted by pulling on the proximal end of the component. A hydrophilic coating may be applied to the inside of the tube to reduce internal friction, thus making removal of the component easier. A code or other unique identifier may be built into the component and / or the feeding tube 102, such that the unique identifier is received and validated by the monitor 110 to ensure that the same component and / or feeding tube 102 is not used on multiple patients. Use on multiple patients is unsafe and unhygienic.In an exemplary embodiment, the code may be a series of printed alphanumeric or machine-readable codes (by numbers or bar codes, or text displayed on a near-field communication device) belonging to the components and / or feeding tube that enter the monitor or controller 110 in an activation step. In another embodiment, the components and / or portions of the feeding tube 102 are disabled upon removal of the components and / or electrical connector 106, making it infeasible to reuse the components and / or feeding tube 102 with multiple patients. In all previously described embodiments, the wires may be connected to the electrical connector 106, which in turn is connected to the monitor 110 through a cable 108. In another embodiment, the sensors may be connected to the monitor through Wi-Fi, Blue tooth, wireless interface, cellular, or any other advantageous wireless network. In this document, unless the context dictates otherwise, the noun "monitor" refers to a computer. Such a computer may be configured to track the patient's condition, other patient data, medical equipment or devices used to assist the patient, etc. The monitor preferably, but can optionally include a display (e.g., a monitor screen) or other indicators (e.g., an audible sound) for the clinician. Although the described embodiments refer to a "monitor," this usage should not be used to limit the invention.

[0040] This exemplary embodiment includes an acoustic emitter 118. The acoustic emitter 118 is used to generate a sound that is then picked up by the acoustic sensor 104. The acoustic emitter 118 can use a piezoelectric transducer or other convenient mechanism to generate the desired sound. As used in this document, "sound" refers to any sound wave and is not limited to audible sounds. Thus, the sound emitted from the acoustic emitter 118 can be audible or inaudible (or both). The acoustic emitter 118 is connected to the electrical connector 106 by a wire 124. The acoustic emitter 118 can be designed such that a standard ECG pad is placed at the end of the acoustic emitter. Alternatively, the acoustic emitter 118 can be formed into an ECG pad and thus connected to a polarized ECG clip wire 124. The acoustic emitter 118 can be placed in close proximity to the stomach. In an exemplary embodiment, the acoustic emitter 118 can be placed on the abdomen just behind the left costal margin.

[0041] In an exemplary embodiment, the device also includes two electrode sensors. In this exemplary embodiment, the two electrode sensors are used to capture ECG data that can aid in the process of determining the location of the feeding tube. In this exemplary embodiment, the electrode sensors 120-122 are connected to the electrical connector 106 by wires 126-128. The electrode sensors are used to record cardiac patterns and interpret respiratory patterns. To determine cardiac patterns, the electrodes detect the electrical activity of the heart. When the electrical activity of the heart is displayed on an oscilloscope, monitor or paper chart display, it is called an electrocardiogram (EKG or ECG). As described by Geus et al., "Ambulatory measurement of respiratory sinus arrhythmia and respiratI / On rate", BI / Ological Psychology, vol. 41, no. 3, pp205-227, 1995 (hereinafter referred to as "de Geus"), the breathing pattern can be predicted from the ECG signal by detecting respiratory sinus arrhythmia (RSA), which is a modulation of the RR interval (i.e., the time between successive ECG R waves) (hereinafter referred to as ECG breathing pattern). In an exemplary embodiment in which another electrode is added to the device, another option of predicting the breathing pattern from the ECG signal is possible. In particular, according to Moody et al., "DerivatI / On of respiratory signals from multi-lead ECGs", Computers in CardI / Olgy, vol. 12, pp113-116, 1985 (hereinafter referred to as "Moody"), the breathing pattern can be predicted by examining the changes in the cardiac axis during breathing, which manifest themselves as changes in QRS amplitude, according to Moody et al., "DerivatI / On of respiratory signals from multi-lead ECGs", Computers in CardI / Olgy, vol. 12, pp113-116, 1985 (hereinafter referred to as "Moody"), the breathing pattern can be predicted by examining the changes in the cardiac axis during breathing, which manifest themselves as changes in QRS amplitude. In another exemplary embodiment, breathing patterns can be measured by impedance pneumotachography, where the impedance between two electrodes is measured. The impedance increases with inspiration and decreases with expiration. The electrode sensors 120-122 can be placed on the chest, arms, or other convenient or advantageous locations.In an exemplary embodiment, the acoustic emitter 118 can also function as an electrode sensor. For example, the same standard ECG pad can have both an acoustic emitter and an ECG conductive electrode attached thereto. Elements of the acoustic emitter and the ECG conductive electrode can be shared. For example, the ECG conductive electrode can also function as a housing for the acoustic emitter. This can eliminate the need for a second standalone electrode sensor in some situations. For example, using the acoustic emitter 118 as an electrode sensor can eliminate the need for the electrode sensor 122.

[0042] An exemplary process for using the device described in Figures 1A-1C is proposed in Figure 2. In a first step 201 of this exemplary process, the clinician inputs patient data into the monitor (also referred to in this document as the controller), as illustrated in the exemplary depiction of a monitor screen shown in Figure 3. Patient data such as name 302, ID number 304, gender 306, height 308 and weight 310 are entered into the monitor manually or via electronic data exchange. Optionally, the clinician can measure and enter into the monitor the distances between the nose, ears and navel. In step 202, the monitor calculates and displays a target distance for inserting the tube based on this patient data. This target distance indicates the length the tube must be inserted into the patient's body (e.g., measured from the patient's front teeth, lips or nose) and can be visually confirmed by reference to the measurement markings on the tube. The algorithm for calculating the target measurement can be based on nomograph data, as described in Cirgin Ellet et al., "Predicting the insertI / On Distance for Placing Gastric Tubes," Clin Nurs Res 2005 Feb;14(1):11-27 (hereinafter Cirgin Ellet), which is incorporated herein by reference in its entirety. The nomograph can be used to identify an appropriate target length of tube insertion that is determined to correspond with accurate positioning of the tube end in the patient's stomach.

[0043] When the tube is inserted into the patient an intermediate distance (e.g., the point where a particular distance marking on the tube is about to pass the nose or mouth), an insertion message 314 is displayed instructing the clinician to stop insertion. In an embodiment, this intermediate distance was calculated to be 25 cm. This intermediate distance is determined by the computer as a function of the confirmed target depth of tube insertion (e.g., by referencing a percentage of the confirmed target depth or a look-up table that pairs a range of tube insertion depths with the corresponding intermediate distances). The distance markings indicate the point at which the clinician should stop insertion to monitor for one or more signals consistent with a tube being inserted correctly or consistent with a tube being inserted incorrectly. The signals are generated by the patient, such as, for example, a heartbeat sound or breathing sounds. In this embodiment, the clinician can check the monitor to ensure that the tube is not in an improper part of the airway, such as through the glottic opening or through the vocal cords in the pharynx, airway or bronchi, and / or that the auscultated heart pattern is consistent with the correct location. Data indicating proper tube placement in the esophagus may include one or more of the following: 1) failure to detect characteristic sounds of air moving in the lower airways, such as in the pharynx, trachea, and / or bronchi ("auscultated lower airway pattern"); 2) detection of sounds produced by a beating heart within an appropriate range of intensity ("auscultated cardiac pattern"); 3) calculation of an appropriate distance between the acoustic sensor and the acoustic emitter.

[0044] In step 203, the clinician attaches two electrodes 118, 120 to the body, with electrode 118 ideally placed on the abdomen just behind the left costal margin and electrode 120 placed in an accessible location such as the shoulder. After attaching the two electrodes, the monitor will show message 316 if it is correctly receiving and processing the cardiac and respiratory signals. The clinician can then proceed to the third step and press a button at the start of tube placement, thus initiating the capture and analysis of acoustic signals by the monitor. In this embodiment, the monitor analyzes these acoustic signals in succession and detects three separate patterns, specifically the auscultated lower airway pattern combined with those placed in the pharynx, trachea and / or bronchi, the auscultated cardiac pattern and the acoustic pattern from the acoustic emitter.

[0045] In step 204, the clinician begins inserting the feeding tube 102 into the patient. Once the feeding tube 102 is inserted, the tube can enter the trachea 107, as shown in Figure 1A. As the tube is inserted, the acoustic sensor 104 captures acoustic signals and transmits this data back to the monitor.

[0046] In step 205, the monitor 110 analyzes these acoustic signals to determine whether they are indicative of auscultated lower airway patterns that are typically recorded when the acoustic sensor is located in the pharynx, trachea 107, or bronchi 109. According to Reichert et al., "Analysis of Respiratory Sounds: State of the Art," Clin Med Cir Respirat Plum Med, 2008 May 16;2:45-58 (hereinafter Reichert), which is incorporated herein by reference in its entirety, the frequency of tongue sounds auscultated from outside the body ranges from 50 to 2500 Hz. Reichert also describes how tracheal sounds can reach up to 4000 Hz. According to Earis et al., "Current methods used for computerized respiratory sound analysis" Eur Respir Rev 2000;10:77,586-590 (hereinafter "Earis"), which is incorporated herein by reference in its entirety, there are numerous advantageous algorithms and analyses for determining whether an acoustic signal is an auscultated lower airway pattern, including but not limited to Fourier transform, waveform, wavelet, and neural networks. A Fourier transform approach to detecting and analyzing respiratory sounds is described in Charbonneau et al., "Basic techniques for respiratory sound analysis" Eur Respir Rev 2000;10:77,625-635 (hereinafter "Charbonneau"), which is incorporated herein by reference in its entirety. In step 205, the monitor also analyzes the ECG signal to determine the ECG respiratory pattern, which can be accomplished by the exemplary approaches previously described for detecting RSA or QRS amplitude.

[0047] In an exemplary embodiment, the monitor may perform an analysis of whether the initially detected auscultated lower airway pattern matches the ECG breathing pattern generated from the electrodes, as shown in step 206. In an exemplary embodiment, this comparison may provide supplemental information that may help ensure that the auscultated lower airway pattern is detected in the sounds detected by the acoustic sensor. There are a number of exemplary approaches to determining whether there is a match between the auscultated lower airway pattern and the ECG breathing pattern. In an exemplary embodiment, the monitor performs an analysis of whether key or identifiable points of the auscultated lower airway pattern match key or identifiable points of the ECG breathing pattern. These key or identifiable points may be generated from specific aspects of inhalation and exhalation with respect to breathing and the timing of such key or identifiable points. For example, the key or identifiable points may be the timing of the peaks of the auscultated lower airway pattern and the timing of the peaks of the ECG breathing pattern. Similarly, the timing of the troughs of the auscultated lower airway pattern and the timing of the troughs of the ECG breathing pattern may be used as key or identifiable points. In an exemplary embodiment, one breathing pattern can be used as a starting point to determine whether the other breathing pattern is a match. For example, the ECG breathing pattern can be continuously measured to generate a baseline of key or identifiable points in the breathing pattern, and then the auscultated breathing pattern can be analyzed to determine the presence of corresponding or sufficient correlation of these key or identifiable points. This pattern matching can include one or more of data smoothing, time series analysis, cross-correlation analysis, convolution analysis, regression analysis, and neural networks. When the auscultated breathing pattern matches the ECG breathing pattern generated from the continuously measured ECG signal, the match of the two patterns can be significant because the auscultated breathing pattern is more likely to be a valid breathing pattern indicative of being located in the pharynx, trachea, and / or bronchi.If the two patterns (i.e., the ECG breathing pattern and the auscultated breathing pattern) match or correlate to a sufficient degree, then the acoustic sensor is highly likely to be located within the lower airway, such as the pharynx, trachea, or bronchi.

[0048] The results of this breathing pattern analysis are displayed on the monitor as shown in step 207. If the result is negative, the monitor displays a message that the feeding tube is not placed in the trachea or bronchi. When auscultatory lower airway pattern is detected (e.g., a match or significant correlation with ECG breathing pattern is detected), the monitor displays a visual and / or audio alarm to alert the clinician that the tube may be placed in the lower airway, such as the pharynx, trachea, or bronchi. At that time, the clinician may stop inserting the tube and withdraw the tube.

[0049] In step 208, the acoustic sensor detects the auscultatory cardiac pattern as the feeding tube is inserted. The heart emits a strong signal, i.e., a signal that is loud and travels a significant distance within the body, allowing immediate detection of tube insertion into the body. The spectrum for capturing the auscultatory cardiac pattern is generally defined as the range of 20-100 Hz according to Reichert. According to Debbal et al., “Computerized heart sound analysis” Comput BI / Ol Med. 2008 Feb;38(2):263-80, Epub 207 Nov 26 (hereinafter “Debbal”), which is incorporated herein by reference in its entirety, there are numerous advantageous methods for analyzing heart sounds to determine the auscultatory cardiac pattern, including, but not limited to, Fourier transform and wavelet transform.

[0050] Once the monitor detects an auscultatory cardiac pattern, in an exemplary embodiment, the monitor will then perform an analysis to determine whether the auscultatory cardiac pattern matches the electrode-generated ECG cardiac pattern, as shown in step 209. In this exemplary embodiment, this comparison can provide supplemental information that can help confirm that an auscultatory cardiac pattern has been detected. Numerous processing steps may be required to perform this pattern matching, including, but not limited to, data smoothing, time series analysis, cross-correlation analysis, convolution analysis, regression analysis, and neural networks. When the detected heart sound pattern matches a continuously measured, known ECG-based, electrode-generated cardiac pattern, a match of the two patterns is significant because that pattern is more likely to be the current heart sound pattern.

[0051] As shown in FIG. 1b, the clinician inserts the feeding tube 102 down the esophagus 101 so that the acoustic sensor 104 moves in close proximity to the heart 111. As the feeding tube 102 passes the entire length of the esophagus moving towards the stomach 103, the monitor 110 continuously measures the intensity of the heart sounds. As the feeding tube 102 moves closer to the heart 111 during this passage, the heart sounds should increase in intensity, or amplitude. Conversely, as the feeding tube 102 moves past the heart and closer to the entrance to the stomach 103, the heart sounds should decrease in intensity, or amplitude. The increasing or decreasing intensity in the measured auscultatory cardiac pattern is analyzed to determine the approximate location of the feeding tube, e.g., the location of the feeding tube relative to the patient's heart. The auscultatory cardiac pattern measurements are analyzed over time to determine if they match a similar pattern of increasing or decreasing intensity, as shown in step 210. A number of processing steps may be required to perform this pattern matching, including, but not limited to, data smoothing, time series analysis, cross-correlation analysis, convolution analysis, regression analysis, and neural networks. For example, the maximum amplitude of the auscultated cardiac pattern is identified and plotted against time. These points are then analyzed to identify an almost continuous increase in amplitude to a maximum amplitude and / or an almost continuous decrease in amplitude from a maximum amplitude. In step 211, the results of this analysis are shown on the monitor as a message describing the status of the analysis and a chart showing the intensity of the auscultated cardiac pattern over time.

[0052] In step 212, the monitor analyzes the acoustic signal coming from the acoustic emitter 118 and captured by the acoustic sensor 104 to calculate the distance between the acoustic emitter and the acoustic sensor. The acoustic signal can take a number of exemplary forms, including but not limited to an acoustic pulse, a continuous variable tone, and can be emitted at various audible, ultrasonic, or other advantageous frequencies. By knowing the exact timing to initiate the acoustic signal from the acoustic emitter and the timing of the signal being received by the acoustic sensor, the monitor can perform a calculation to measure the distance between the acoustic emitter and the acoustic sensor. For example, when a pulse is emitted by the acoustic emitter 118 at time t1 and received by the acoustic sensor 118 at time t2, in an exemplary embodiment, the distance x=(t1-t2)xv, where v is the speed of sound passing through the patient (v is determined through calibration, i.e., tested on the patient from a known distance, or determined from empirical data). Thus, this process provides the distance between the acoustic sensor 104 and the acoustic emitter 118. In step 213, the monitor displays the status of the distance calculations and a chart showing these distance calculations over time. In one embodiment, a distance derived from the distance between the acoustic sensor 104 and the acoustic emitter 118 (e.g., the distance remaining until the end of the feeding tube insertion) may be displayed.

[0053] In an exemplary embodiment, the clinician stops the insertion and checks the monitor after inserting the tube approximately halfway into the patient, as shown in FIG. 1b. The purpose of checking the monitor is to determine if any of the summary data indicates that the tube is located in the trachea or bronchi, or if the tube appears to be correctly located in the esophagus, as shown in step 214. In this example, the clinician stops the insertion based on markings on the tube near an entry point, such as the nose or mouth, indicating that the tube has been inserted 25 cm. Other exemplary markings and insertion distances may be utilized depending on or calculated based on the depth of the target identified, or otherwise calculated as a function of patient data (size, age, sex, etc.). The clinician can check the monitor to see if there is an indication that the tip of the tube is located in the pharynx, trachea, or bronchi. The clinician can also check the monitor to see if there is an increasing intensity of the auscultatory cardiac pattern, which is an indication that the tube is gradually moving down the esophagus and near the heart. The absence of an auscultated lower airway pattern combined with an increase in the intensity of the auscultated cardiac pattern indicates that the tube is properly descending the esophagus and advancing towards the stomach. The clinician can also check the monitor to see if the distance between the acoustic sensor and the acoustic emitter is decreasing during insertion. This decrease in distance indicates that the tube is gradually descending the esophagus and not coiling back up in the mouth. The combination of the absence of an auscultated lower airway pattern, an increase in the intensity of the auscultated cardiac pattern, and a decreasing distance between the acoustic sensor and the acoustic emitter provides a strong indication that the tube is properly descending the esophagus and advancing towards the stomach. Any combination of an auscultated lower airway pattern, an indication that the intensity of the auscultated cardiac pattern does not increase with tube insertion, and no evidence of a decrease in the distance between the acoustic sensor and the acoustic emitter indicates that the tube is not properly descending the esophagus and advancing towards the stomach and may be in the trachea or bronchi or coiled up.After reviewing these data, the clinician can then decide whether to proceed with tube insertion, remove and reinsert the feeding tube, or take other actions such as taking an x-ray to confirm tube position.

[0054] In FIG. 1c, the acoustic sensor 104 is shown in the stomach 103 and is located closer to the acoustic emitter 118. After the clinician inserts the tube 102 to the recommended insertion location, the clinician can check the monitor to see the distance between the acoustic emitter 118 and the acoustic sensor 104. The clinician can then compare this calculated distance with a visual identification of where the acoustic emitter 118 is physically located on the patient and assess whether that distance is consistent with the feeding tube 102 being correctly placed in the stomach 103 and not in the trachea and bronchi 109. As the feeding tube 1012 progresses toward and into the stomach, the calculated distance between the acoustic emitter 118 and the acoustic sensor 104 should decrease.

[0055] In step 215, the clinician reviews the summary information and inputs into the monitor the distance marking on the tube. This distance marking corresponds to the furthest point the tube has been inserted into the patient. The monitor then compares the input tube distance to the recommended insertion distance calculated in step 202. When the difference between the two insertion distances is above a predefined threshold, the monitor will display a message that the tube insertion distance is insufficient for proper placement in the stomach. When the difference between the two insertion distances is below a predefined threshold, the monitor will display a message that the tube insertion distance is insufficient. In an exemplary embodiment, the tube distance difference threshold is 5 cm; in another embodiment, the difference threshold is 10% of the identified target depth.

[0056] FIG. 4 shows an example of a monitor screen when all evaluations indicate that the tube is correctly placed in the stomach. The most prominent indication on the screen is status indicator 401, which displays a green color, meaning that the tube is correctly placed. When the monitor algorithm calculations indicate that the tube is not correctly placed or when there is not enough information to determine if the tube is correctly placed, status indicator 401 displays a yellow color. When the monitor algorithm calculations indicate that the tube is located in the trachea or bronchi, status indicator 401 displays a red color. Additionally, text status indicator 402 communicates the status of tube placement. In the scenario of FIG. 4, text status indicator 402 displays the message "TUBE CORRECTLY PLACED". Heart and respiratory signal indicator 403 displays the message "HEART AND RESPIRATOR CONNECTED", indicating that the heart and respiratory signals from the electrodes are being captured correctly. Tracheal and lung sound signal indicator 404 displays the message "TRACHEA / LUNG SOUND NOT DETECTED", indicating that the acoustic sensor and monitor are not currently detecting any tracheal or lung sounds, and therefore, indicating that the tip of the feeding tube is not in the trachea or lungs. Heart passage indicator 405 displays the message "Tip Passing Heart in Esophagus" indicating that the acoustic sensor and monitor have detected a pattern where the tip of the tube passes by the heart as it passes through the esophagus. The indication of the tip of the tube passing by the heart as it passes down the esophagus is further confirmation that the tip of the tube is not located in the trachea or bronchi. Acoustic emitter distance indicator 406 displays the message "Tip 3cm from Acoustic Emitter" indicating that the acoustic sensor is located 3cm from the acoustic emitter. An indication that the acoustic sensor is located a short distance from the acoustic emitter, which should be located behind the left costal margin, is further confirmation that the tip of the tube is located in the stomach and not in the trachea or bronchi. Tube insertion indicator 407 displays the message "Tube Insertion 45cm Sufficient" indicating that the entered tube insertion distance is sufficient for the tube to be properly placed in the stomach.Once the clinician is satisfied that the data displayed on the monitor is sufficient to confirm that the tube has been properly placed in the stomach, the clinician can then submit the electronic medical record by pressing button 409.

[0057] The clinician has the option to review more detailed data on the monitor. By pressing the data chart view button 408, the clinician can view more detailed information in chart format. FIG. 5 illustrates this optional view of viewing data in chart format. For example, the clinician can review the heart sound intensity chart 501 to see a time-based plot of the heart sound intensity data. If the feeding tube is passing correctly through the esophagus, this will be indicated by an auscultatory heart pattern that increases as the tip of the tube approaches the heart and decreases as it passes the heart on its path toward the stomach. The clinician can also view (e.g., graphically) the distance of the tip of the feeding tube over time, which should generally be noted as the tube is inserted, the distance of the tip of the tube from the sound emitter decreases. Alternatively, the clinician can review the heart sound intensity against the measured distance of the feeding tube tip. In this example, the measured distance of the feeding tube tip may be displayed along the x-axis and the heart sound intensity may be displayed along the y-axis. The clinician can repeatedly sample the heart sound intensity at the same distance by inserting and withdrawing the feeding tube.

[0058] After inserting the tube, the clinician can look at the monitor to see an update of the distance between the acoustic sensor and the acoustic emitter, which can be important to determine if the tube has moved during treatment and if the tube insertion needs adjustment.

[0059] In an exemplary embodiment, a clinician can use the same monitor for multiple patients. In this embodiment, the monitor associates a unique ID with each feeding tube. If a feeding tube is disconnected and later reconnected, the monitor can utilize the feeding tube's unique ID to combine all data already entered and measured from that feeding tube. Thus, a clinician can insert feeding tubes in multiple patients using one monitor and, if necessary, reconnect the monitor to the tube and evaluate the tube's position without having to re-enter any patient data. Patient data history is stored so that any patient data already entered can be evaluated and combined with any new feeding tubes.

[0060] FIG. 6 illustrates another embodiment of the device for measuring the position of the feeding tube. In this exemplary embodiment, two acoustic emitters 601 and 602 are used to measure the distance from the acoustic sensor to the acoustic emitters. The acoustic emitters 601 and 602 are connected to a rigid member 603. The rigid member 603 is connected to an electrical connector 106 via a wire 604. The two acoustic emitters 601 and 602 act as electrodes to capture cardiac and respiratory signals. The distance between the acoustic sensor 104 and the acoustic emitters 601 and 602 can be calculated in the same manner as previously described elsewhere in this document. Thus, at each instance in time, the distance between the acoustic sensor 104 and the acoustic emitter 601 is known, and the distance between the acoustic sensor 104 and the acoustic emitter 602 is known. Furthermore, the distance between the acoustic emitter 601 and the acoustic emitter 602 is known, since they are fixedly positioned on the rigid member 603. These three distances form a triangle, whereby by knowing the length of each side of the triangle, it is possible to calculate the angle of this triangle and therefore determine the position of the acoustic sensor. With an acoustic emitter (e.g., just one of 601 and 602) at a certain distance from an acoustic sensor, it is possible to determine the position of the acoustic sensor (e.g., determined to be on a point on the surface of an imaginary three-dimensional sphere with the placement of the acoustic sensor at its center). In this exemplary embodiment with two acoustic emitters, it is possible to determine the position of the acoustic sensor as being on a point on the perimeter of an imaginary two-dimensional circle 605. This level of accuracy can be advantageous in determining the position of the acoustic sensor 104. For example, when the two acoustic emitters 601 and 602 are placed vertically, the imaginary circle on which the acoustic sensor 104 is determined to be located will be horizontal. Thus, the vertical position of the acoustic sensor 104 can be accurately determined even when its horizontal position is determined by this calculation to be on a horizontal imaginary circle. The use of three acoustic sensors (not shown in FIG. 6) arranged in a triangle and spaced apart at known intervals (i.e., not arranged in a straight line) allows for greater accuracy in determining the location of the acoustic sensors. Triangulation is used to calculate a point in space related to the locations of the three acoustic emitters.For example, for each of the three acoustic emitters, a sphere can be measured with its center at the corresponding acoustic emitter, and the radius of the sphere represents the distance measured between the acoustic emitter and the acoustic sensor and the surface of the sphere represents the possible positions of the acoustic sensor. The intersection of these three measured spheres can be determined as the position of the acoustic sensor. Another method is to use each two of the three acoustic sensors to calculate the possible placements along a corresponding imaginary circle. The intersection of these three imaginary circles would correspond to the measured position of the acoustic sensor 104.

[0061] FIG. 7 illustrates another embodiment of the device for determining the position of the feeding tube. In this exemplary embodiment, the device uses a mobile device 701 (shown as 701a, 701b, 701c, each in a different position). The mobile device 701 can take the form of a cell phone, tablet, or other significant mobile device. In this embodiment, the mobile device 701 communicates with the monitor using a wireless connection. A tip component 707 is placed at the tip of the feeding tube and in this embodiment is used to sense an acoustic signal from the mobile device 701. In the exemplary embodiment, the mobile device 701 continuously emits an acoustic signal. In this embodiment, the tip component 707 is an acoustic sensor 104. The signal received by the tip component 707 is used by the monitor 110 to calculate the distance between the tip component 707 and the mobile device 701.

[0062] An exemplary process is to move the mobile device 701 while the tip component 707 receives an acoustic signal. At a first position, the mobile device 701a is a first distance calculated from the tip component 707, where the distance can be visualized as a radius of a first sphere 702 (with the mobile device 701a at the center) and the location of the tip component 707 is somewhere on the surface of the first sphere 702. At a second position, the mobile device 701b is a second distance calculated from the tip component 707, where the distance can be visualized as a radius of a second sphere 703 (with the mobile device 701b at the center) and the location of the tip component 707 is somewhere on the surface of the second sphere 703. At a third position, the mobile device 701c is a third distance calculated from the tip component 707, where the distance can be visualized as a radius of a third sphere 704 (with the mobile device 701c at the center) and the location of the tip component 707 is somewhere on the surface of the third sphere 704. If we assume that the acoustic sensor does not move between the three positions, then the intersection point 705 where the three spheres intersect with each other is the position of the tip component 707 in three-dimensional space. Wikipedia, “Trilaterati / on” Wikiedia Web. 3 March 2015, Web.<http: / / en.wikipedia.org / wiki / Trilaterati / on> This method is called trilateration as described by Gregorio C. To measure this intersection 705, it is first necessary to measure the position of the mobile device 701 at each location relative to the other locations.

[0063] In an exemplary embodiment, the position of each location relative to other locations can be measured using an accelerometer and gyroscope included in the mobile device 701. The accelerometer and gyroscope allow the location, orientation and velocity of the mobile device to be calculated. In an exemplary embodiment, the mobile device emits an acoustic signal at 20 Hz, i.e., 20 times per second, and therefore continuously calculates the relative location 20 times per second. Other exemplary frequencies for emitting acoustic signals and calculating the relative location can also be used.

[0064] In an exemplary embodiment, the accuracy of measuring the relative position of the mobile device 701 can be increased by using supplemental reference points. In an exemplary embodiment, a known visual fiducial 706 can be used. In this embodiment, a camera built into the mobile device 701 can be used to view the visual fiducial 706. An exemplary form of this visual fiducial 706 can be a two-dimensional rectangle with one side measuring 2 cm and another side measuring 4 cm that is attached to the patient's body. Another exemplary form of this visual fiducial 706 is a high-contrast two-dimensional marker of known size that is attached to the patient's body and lacks reflection and / or rotational symmetry. Other forms and sizes can be used. Since the form and size are known, an algorithm in the acoustic emitter 701 can analyze the data from the camera and calculate the distance from the visual fiducial 706 to the mobile device 701 based on the characteristics of the visual fiducial 706, such as the diameter of the disk calculated compared to the known diameter and the shape of the disk compared to the known shape.

[0065] In an exemplary embodiment, the relative position of the tip component 707 is communicated to the clinician via an augmented reality interface on a screen included in the mobile device 701. Augmented reality is defined as seeing data into what appears in the field of view of a camera. In this embodiment, the clinician looks at the screen of the mobile device 701 and sees what appears to be a real-time video broadcast of the patient. The clinician first swings the mobile device 701 in front of the patient, then backwards and side to side to calculate the relative position of the tip component 707. A visual display of the patient's body on the screen shows a transparency effect, creating the illusion that the tip component 707 can be seen inside the patient's body. An exemplary embodiment of this transparency effect can be within the thin line of the tip component 707, and the patient's body has an algorithm that creates the appearance of a surface, so that it appears as if one is looking underneath the patient's body. Thus, the clinician can see the position of the tip component 707 relative to the patient's anatomy and can determine that the tip component 707 is correctly located in the stomach and not, conversely, in the trachea or bronchi. In an exemplary embodiment, the algorithmically generated appearance simulates visual displays of organs such as the stomach, lungs and heart to assist the clinician in determining the position of the acoustic sensors.

[0066] B. Measuring Tube Position Using a Magnetic Field Sensor In an exemplary embodiment, an alternative (or supplemental) device may be used in a similar process already described for the mobile device 701 and the tip component 707. This alternative (supplemental) device includes a magnetic field sensor or magnetometer built into the mobile device 701. The magnetometer may measure the strength of the magnetic field around the mobile device 701. In an exemplary embodiment, the tip component 707 may include a magnetic material with a known magnetic moment. In another embodiment, the tip component 707 is comprised of coiled wire that generates a known magnetic moment with the input of a known electrical signal. In an exemplary embodiment, the clinician also swings the mobile device 701 forward first, then backward, and from side to side on the patient. Instead of measuring the distance between the mobile device 701 and the tip component 707 based on the transit time of the acoustic signal propagating therebetween, the distance is instead calculated based on the strength of the magnetic field measured from the magnetic material inside the tip component 707. A measure of the distance (measured in meters) from the mobile device 701 to the tip component 707 can be calculated using the following exemplary equation 1:

[0067]

number

[0068] In this equation, μ0 denotes the permeability constant (4π×10-7 Tm / A), μ is the magnetic moment of the magnetic material of the tip component 707, and B is the magnetic field (measured in Tesla). The clinician can also view an augmented reality visual representation of the tip component 707 with respect to the patient's body on the screen of the mobile device 701. In an exemplary embodiment, the accuracy of measuring the relative position of the mobile device 701 can also be increased by using known visual references, as described above.

[0069] II. Motility Measurement Systems and Devices Determining whether a patient can tolerate enteral feeding is crucial to providing effective treatment and preventing devastating complications. Determining whether a patient has sufficient gastric motility can indicate whether enteral feeding will be tolerated. Normal gastric motility can be defined as regular or irregular gastric peristalsis that propels stomach contents into the small intestine. FIG. 8 illustrates an example of this peristaltic movement. In FIG. 8, peristaltic waves 801 are illustrated moving through the stomach. According to Ehrlein et al., “Gastrointestinal Motility” Class Tutorial, Technische Univeresitat Munhen, 2014 (hereinafter Ehrlein), which is incorporated herein by reference in its entirety, these peristaltic waves 801 move food through the stomach, through the pyloric sphincter 803, and out into the duodenum. During peristaltic wave 801 movement, the internal muscles of the stomach 103 contract, pushing food from the proximal stomach towards the pyloric sphincter 803 at the distal end of the stomach. In addition to peristalsis 801, the stomach generally contracts, thus shrinking the overall size of the stomach, thereby moving food 802 towards the pyloric sphincter 803; this phenomenon is called tonic contractions. The peristaltic waves 801 and tonic contractions encourage food to be further broken down and therefore digested. Food that has been broken down to the point where it is rather liquid is referred to as gastric chyme 805. The peristaltic waves 801 move this gastric chyme 805 more easily through the pyloric sphincter 803 towards the duodenum, whereas the larger undigested pieces of food are pushed back into the stomach 103 by an action called retropulsion. Understanding gastric motility can be beneficial to clinicians in a number of ways. First, if a patient has good motility, there is less risk that the patient will regurgitate stomach contents into the lungs. Second, good motility suggests that clinicians can speed up the patient's nutritional intake levels, which potentially aids recovery. Some embodiments provide a meaningful way to measure motility.

[0070] A. Measuring Motility Using Acoustic Sensors In an exemplary embodiment, an acoustic sensor is used to measure gastric motility. The acoustic sensor 104 can be placed at the distal end of the feeding tube 102 as shown in FIG. 8. The acoustic sensor 104 can measure various frequency ranges and types of vibrations, including but not limited to vibrations coupled to the audible frequency range (20-20,000 Hz). In an exemplary embodiment, a piezoelectric sensor is used to measure the acoustic signal. A number of other exemplary sensors can be used to measure the acoustic signal, including but not limited to electrets, capacitors, piezoelectric crystals, piezoelectric ceramics, piezoelectric membranes, fiber optic microphones, or contact accelerometers. The vibrations measured by the acoustic sensor 104 can come from a number of sources, including but not limited to peristalsis, gas bubbles, flatulence, and sounds from nearby organs, such as the lungs, heart, or small intestine. A bowel sound analysis study by Watson et al., “PHonoenterograpHy: the recording and analysis Of bowel sounds” Gut. 1967 Feb;88-94 (hereinafter “Watson”), which is incorporated herein by reference in its entirety, revealed that bowel sounds increase in intensity during a meal and remain at elevated intensity for two or more hours after a meal. Bowel sounds are complex with a mixture of tones, often a series of closely coupled sounds in the frequency range 150-5000 Hz.

[0071] A number of vibration sources can be detected. In a study by Campbell et al., "Surface vibration analysis (SVA): a new non-invasive monitor of gastrointestinal activity," Gut, 1989 Jan;30(1):39-45 (hereinafter "Campbell"), the entire contents of which are incorporated herein by reference, Campbell quantified these bowel sounds, measuring vibrations in the frequency range of 40-10,000 Hz with a piezoelectric sensor. Specific patterns of bowel sounds can be associated with fasting and postprandial states, where food is digested and therefore manipulated to be measured as well.

[0072] In one embodiment, the acoustic sensor detected vibrations combined with peristaltic wave motion. In this exemplary embodiment, the acoustic sensor 104 may be a piezoelectric-based accelerometer. Additionally (or alternatively), the accelerometer may measure motion (e.g., the physical motion of the accelerometer itself), such as peristaltic waves 801 moving down the stomach 103. For example, peristaltic waves 801 may be detected by detecting a pattern having a frequency of one to three contractions per minute, as shown in FIG.

[0073] A positive indication of gastric motility (e.g., 1-3 contractions / waves per minute) should be correlated to patients who are tolerating enteral feeding and therefore with sufficient sensitivity. Conversely, a negative indication of motility (e.g., less than 1 contraction / wave per minute) can help identify patients who are not tolerating enteral feeding, allowing clinicians to adjust treatment and monitor patients more closely.

[0074] To ensure that the acoustic sensor 104 is functioning correctly, the monitor can periodically monitor other body sounds as a means of ensuring that the device is functioning correctly. If the cardiac muscular tissue patterns are periodically captured correctly, this indicates that the acoustic sensor is functioning correctly, and therefore can be inferred to also capture accurately the vibration measurements of stomach motility. In another embodiment, the monitor periodically captures an acoustic signal from the acoustic emitter 118 to ensure that the acoustic sensor 104 is functioning correctly.

[0075] In an exemplary embodiment, the acoustic sensor measures vibrations coupled to oscillating gas bubbles in the small intestine. In this exemplary embodiment, the acoustic sensor 104 can be a piezoelectric-based accelerometer. According to Liu et al., “Oscillating Gas Bubbles as the Origin of Bowel Sounds: A Combined Acoustic and Imaging Study” Chin J PHysI / Ol. 2010 Aug 31:53(4):245-53 (hereinafter “Liu”), which is incorporated herein by reference in its entirety, there is evidence that these gas bubbles are continuously present in the small intestine. The bubbles can be identified by their oscillation frequency. Also, the size of the bubbles can be measured by the measured frequency. The size of the bubbles can change as they move through the different sized structures of the small intestine. In one embodiment, the bubble patterns and frequencies are analyzed to assess gastrointestinal motility and other gastric functions. Analysis of gas bubbles in the small intestine can be combined with analysis of peristaltic waves in the gastric environment or other sensor data to assess overall gastrointestinal motility.

[0076] In an exemplary embodiment, various gastric motility measurements can be added and used to measure the effectiveness of the enteral feeding type and amount. In an exemplary embodiment, the patient's condition is also a factor in measuring the effectiveness of the enteral feeding type and amount. By collecting data on the patient's condition, it may be possible to guide the enteral feeding type and amount and / or obtain optimal gastrointestinal motility for each patient's condition. Conversely, analyzing these data can provide insight as to which enteral feeding type and amount should not be used for a particular patient's condition.

[0077] B. Measuring remaining stomach contents using a temperature sensor It is standard care in hospitals to measure the gastric residual volume of patients receiving enteral nutrition. This procedure is referred to as measuring the gastric residual volume (GRV). Gastric residual volume is usually measured by attaching a large syringe to the proximal opening of the feeding tube and aspirating all of the gastric contents into the syringe. A low gastric residual volume indicates that the patient is tolerating enteral nutrition and has adequate gastric motility. A high gastric residual volume indicates that the patient is not tolerating enteral nutrition and does not have adequate gastric motility. McClave et al., “Guidelines for the provisI / On and assessment of nutritI / On Support therapy in adult critically ill patient,” JPEN J Parenter Enteral Nutr. 2009, which is incorporated herein by reference in its entirety. According to McClave, May-June:33(3)277-316, high gastric volume is defined as 250 mL. Clinicians can receive high gastric residual volume measurements and adjust the patient's treatment accordingly, such as decreasing the feeding tube feeding rate, prescribing prokinetic drugs, or elevating the head of the bed. However, high gastric residual volume does not always correspond to a gastric motility problem. In some cases, a gastric residual volume of 250 mL or more may be required to trigger gastric emptying into the small intestine by the stomach, and thus a gastric residual volume of 250 mL or more may be part of normal digestion. Also, these gastric residual volume measurements are often performed every four hours in the treatment of acutely ill patients receiving enteral nutrition. Thus, this procedure takes away from the clinician time that could otherwise be used to treat the patient. The procedure is also often unsanitary, due to the removal and reinsertion of gastric contents.

[0078] In an exemplary embodiment, the GRV is measured using an indicator dilution technique. The indicator dilution technique is well known and widely used in medicine, scientific research, and industry to measure fluid (gas or liquid) volume or flow rate. As described in Schoeller “Indicator Dilution / On Methods” Quality of the Body Cell Mass. Serono Symposia USA 2000, pp55-67 (hereinafter “Schoeller”), which is incorporated herein by reference in its entirety, the indicator dilution method of measuring volume (or flow rate) is based on the law of conservation of mass. A known amount of tracer (indicator) is added to a pool of tracer to produce a solution after equilibration in which the final concentration of indicator is equal to the amount of indicator added divided by the pool volume. If volume is the desired readout, then the following equation reasserts: Volume (pool size) = Tracer dose / concentration of tracer.

[0079] The validity of the indicator dilution technique relies on four assumptions. First, the indicator mixes rapidly and thoroughly with the fluid in the pool. Second, after mixing is ceased, the concentration of the indicator is uniform within the pool volume. Third, the indicator is distributed only into the pool volume of interest. Fourth, the tracer is stable (over the period required for measurement).

[0080] While these assumptions are often valid in vitro, when applying indicator dilution techniques in vivo (e.g., in medical applications), typically some or even all of the assumptions are not entirely sufficient. Thus, in medical (or other in vivo biological) applications, indicator dilution methods are rarely completely accurate. Nevertheless, these methods are often accurate enough to be clinically useful. Furthermore, as discussed below, it may be possible to partially adjust for systematic errors in the measurements by incorporating empirically derived coefficients into the final equations used to convert the measured signal into clinically useful information.

[0081] Indicators are often chemicals that are easily detectable by using appropriate analytical means. Examples include radiolabeled compounds (e.g., tritium-labeled water), stable isotope-labeled compounds (e.g., 13C-labeled glucose), dyes (e.g., indocyanine green dye), or easily detected chemical entities (e.g., Li + cations, polyethylene glycol).

[0082] GRV was measured using an indicator dilution technique. In a laboratory gastric model, Hurwitz, “Measuring gastric volume by dye dilution”, Gut 1981 Feb;22(2):85-93 (hereafter “Hurwitz”), which is incorporated herein by reference in its entirety, demonstrated that it was possible to measure “gastric” volume using phenol red dye dilution. Later, Hardy et al., “Determining gastric contents during general anaesthesia;evaluatI / On of two methods”, Can J Anaesth, 1987 Sep;34(5):474-7 (hereafter “Hardy”), which is incorporated herein by reference in its entirety, demonstrated GRV measurement in patients using polyethylene glycol (PEG) as a tracer and turbidimetry as a means of measuring PEG concentration. These authors showed that GRV measured by indicator dilution technique was not significantly different from GRV measured by aspiration of gastric contents (via a Levin nasogastric tube).

[0083] Temperature may also be an effective tracer. For example, cardiac output (i.e., blood flow through the heart) is commonly measured in clinical practice by injecting a known amount of cold saline into the venous side of the blood circulation and detecting the resulting change in pulmonary artery blood temperature. In an exemplary embodiment, gastric residual volume is determined by measuring the temperature of the gastric contents before and after the control. In this embodiment, a temperature sensor is placed at the distal end of the feeding tube, which can be connected to the monitor via a wire. The monitor 110 is capable of performing continuous temperature measurements of the gastric contents. The device is similar to that of FIG. 8, but instead of the acoustic sensor 104 placed at the distal end, a temperature sensor or thermistor is used. Of course, combinations of sensors, such as those described herein and other sensors, can be used, and such combinations should be considered within the scope of the present invention. The monitor can then control and introduce a known amount of fluid through the feeding tube and into the stomach, which in an exemplary embodiment can be 50 mL of distilled water cooled to a temperature of 1° C. It is significant to use water as a control because acute care patients require hydration and water is a safe substance. The temperature sensor can then continuously measure the change in temperature of the stomach contents after introducing this control of cooling water. In an exemplary embodiment, the GRV can be calculated using the following equation: GRV=k1×k2×V injectate (T before -T injectate ) / (T before -T after )

[0084] In this equation, V injectate is the volume of cold water that is pumped into the stomach through the feeding tube. before is the temperature of the stomach contents before the injection of the aliquot of cold water. T injectate is the temperature of the cold injectate. T afteris the temperature of the stomach contents after injection of the indicator. k1 is a dimensionless constant that depends on the specific heat of the water contents, the density of water, the specific heat of the stomach contents, and the density of the stomach contents. k2 is a dimensionless constant that accounts for the dead space volume of the feeding tube and possibly other unmeasured sources of system error. In an exemplary embodiment, the rate of temperature change that occurs through the stomach contents can be used to calculate the GRV. The calculation of the temperature change rate can add information that improves the calculation of the GRV or provides other insight that may prove helpful to the clinician. The type of stomach environment and stomach contents results in significant mixing as part of digestion, and the measured temperature change subsequently reflects the entire stomach contents. Other factors that can be used to calculate the GRV include the enteral feeding rate, the rate of gastric emptying, and medications that may be introduced into the stomach environment. Because there are unaccounted for factors that may affect the accuracy of the calculation of the remaining volume of stomach contents, the algorithm also provides a probability measure that is combined with the volume calculation to help the clinician understand the relative certainty of the GRV calculation.

[0085] In another embodiment, according to Soulsby et al, "Measurements of gastric emptying during continuous nasogastric infusI / On of liquid Teed: electric impedance tomograpHy versus gamma scintigrapHy." Clin Nutr. 2006 Aug;25(4):671-80 (hereinafter, Soulsby), which is incorporated herein by reference in its entirety, gastric residual volume can be measured in some circumstances by measuring the change in impedance of an alternating current applied to the abdominal region by electrodes. In the approach described by Soulsby, 16 electrodes (ECG pads) are affixed in a circumferential pattern around the abdomen. The change in impedance is measured by passing a sinusoidal alternating current (50-100 kHz: 1-10 mA) between one pair of electrodes on the abdomen and measuring the voltage drop between the electrodes on another pair. In the approach described by Soulsby, impedance is measured from all possible combinations of pairs of electrodes and a unique algorithm generates an impedance versus time curve. The system is "calibrated" by introducing a 100 mL bolus of tube feeding into the stomach. The conductivity of the calibration bolus of tube feeding formula is increased by dissolving 17 g / 100 mL of salt (NaCl) in the formula prior to introduction into the stomach.

[0086] An approach similar to that of Soulsby is described by McClelland et al. "Epigastric impedance: a non-invasive method for the assessment of gastric emptying and motility." Gut. 1985 Jun;26(6):607-14 (hereinafter "McClelland"), which is incorporated herein by reference in its entirety. There is also a similar method described by Sullon et al, "Measurement of gastric emptying rates by radI / Oactive isotope scanning and epigastric impedance." Lancet. 1985 Apr 20: 1(8434):898-9008 (hereinafter "Sutton"), which is incorporated herein by reference in its entirety. The approach described by McClelland and Sutton is similar to the approach described above, except that only four electrodes are used (two in the anterior upper abdomen and two in corresponding positions on the back). The system described by McClelland and Sutton uses "standard" impedance electrocardiograph equipment for signal generation and detection, but with appropriate low-pass filtering to eliminate interference from the cardiac signal. In the approach described by McClelland and Sutton, gastric volume is not measured; rather, the impedance-based system is designed only to measure small changes in gastric volume after a test meal as a function of time. Thus, the primary readout is the half-time of gastric emptying (t 1 / 2 ).

[0087] In one embodiment, the GRV monitor device can use the electrode placement strategy described by McClelland and Sutton, as shown in FIG. 9. In an exemplary embodiment, multiple electrodes are placed on the abdomen. Here, four electrodes 118, 120, 902, and 904 are placed on the abdomen. An AC current is driven through the patient's body between electrodes 118 and 902. The voltage between electrodes 120 and 904 can also be measured. The voltage measurement is filtered to reflect only changes within the frequency range of the AC current between electrodes 118 and 902. The voltage measurement includes an impedance measurement whose amplitude depends in part on the GRV. The electrodes can have multiple functions. For example, electrode 118 can serve as a front electrode to record an ECG signal during tube placement and input an AC current for subsequent impedance measurements. Electrode 118 can be placed at the angle between the left costal margin (of the thorax) and the xiphoid process of the sternum (breastbone). Similarly, electrode 120 can also serve as an anterior electrode to record ECG signals and measure voltage for impedance measurements. Electrode 120 can be placed just behind the left costal margin at a location that is approximately four finger widths (approximately 4-5 cm) to the left of the midline. In this embodiment, electrode 902 can be placed on the patient's posterior and input an alternating current for subsequent impedance measurements. Electrode 904 can also be placed on the patient's posterior and measure a voltage with electrode 120 for impedance measurements. In another embodiment, the same electrode placement strategy can be used, except that instead of placing a pair of electrodes on the posterior, these electrodes are placed on the distal end of the feeding tube and connected by wire (or conductive ink) to an appropriate fitting on the proximal end of the tube. In this exemplary embodiment, electrode 120 on the anterior abdominal wall and electrode 910 on the feeding tube can input or "inject" an alternating current (50-100 kHz: 1-10 mA) into the patient. A second electrode 912 at the distal end of the feeding tube and electrode 118 on the anterior abdominal wall are each capable of receiving an alternating current from electrodes 120 and 910, respectively.By detecting the voltage and current between the two electrodes, it is possible to measure the impedance of the stomach contents between the two electrodes as well as other relevant tissues (e.g., fat, muscle, and skin). In an exemplary embodiment, the patient is electrically isolated from the external environment during this procedure.

[0088] An exemplary process for utilizing the device described in FIG. 10 to measure GRV via impedance is shown in FIG. 10. In a first step 1001 of this exemplary process, a clinician places electrodes on the abdomen and inserts a feeding tube. In step 1002, the feeding type and infusion rate are entered into the monitor 110. In step 1003, the clinician confirms via the monitor 110 that the patient is prescribed an acid suppressing medication. In step 1004, the system is calibrated by first completely emptying the stomach (by aspiration of contents through the feeding tube). Thereafter, impedance is measured with GRV=0. A known volume (e.g., 50 mL) of tube feeding formula is then injected into the stomach via the feeding tube and impedance is measured again (e.g., at GRV=50 mL). For greater accuracy, a three-point calibration can be achieved by injecting a second bolus of tube feeding formula (e.g., another 50 mL aliquot) and recording impedance again. In step 1005, impedance measurement is initiated via the monitor 110. In step 1006, nutritional intake is initiated via the enteral feeding pump 116. In step 1007, the monitor 110 displays the GRV measurement. In step 1008, an audible and / or visual alarm is initiated if the GRV exceeds a defined threshold. This defined GRV measurement threshold can be customized by the monitor 110 settings configuration and may include a default configuration based on the patient's gender, height, weight, nutrition type, fluid restriction, and propofol rate. In step 1009, the monitor 110 can display whether peristalsis is detected. Knowing whether peristalsis is detected helps the clinician determine if the nutrition is tolerated. Peristalsis can be detected by the described embodiments or by other advantageous means. In step 1010, a probability is calculated to determine if the GRV measurement is correctly captured and analyzed. This probability is based on many factors, including but not limited to the GRV measurement, the trend of the GRV measurement, the nutrition type and infusion rate, the acid suppressant drug prescription, the calibration results, and peristalsis detection.The results of this probability calculation can be displayed on the monitor 110. In step 1011, the clinician can decide to perform an optional additional calibration. In this optional calibration, impedance measurements are recorded via the monitor 110. The stomach is then completely emptied by aspirating the contents through the feeding tube. The clinician then manually measures the volume of aspirated gastric contents. The clinician then enters the manually measured volume of gastric contents into the monitor 110. The monitor 110 then uses the manually measured volume to calibrate the ongoing GRV measurement. In step 1012, the GRV measurement results are entered into the EMR system.

[0089] In an exemplary embodiment, a conductivity sensor can be placed at the distal end of the feeding tube. In an exemplary embodiment, the conductivity sensor can take the form of an electrode 910. The conductivity sensor can be utilized to determine the conductivity (the inverse of resistivity) of the stomach contents. This conductance measurement aids in the estimation of GRV because the estimation of GRV utilizing impedance measurements in the upper abdomen (see FIG. 10) depends on the conductivity of the stomach contents and other structures (e.g., skin, muscle tissue, adipose tissue) being probed by the impedance measurement electrodes. The stomach contains relatively conductive material, and as GRV increases, the measured impedance decreases. An increase in the conductivity of the stomach contents also causes a decrease in the measured impedance. By measuring the conductivity, this confounding variable can be factored out of the estimation of GRV. By extension, the measurement of GRV via impedance depends on the difference in impedance of the stomach contents and these other structures (e.g., skin, muscle tissue, adipose tissue). When the ionic strength of the tube-fed formula is low, the impedance difference between the gastric contents and other structures in the upper thoracic region of interest is insufficient to provide a reliable signal for estimating GRV. In the laboratory, this problem can be easily solved by adding a large amount (e.g., 9 g / L: 154 mEq / L) of sodium chloride (NaCl, table salt) to a standard tube-fed formula, ensuring that the ionic strength of the tube-fed formula is sufficient to provide a good impedance signal for estimation of GRV. However, in clinical practice, many patients have low levels of sodium ions (Na + ) or chloride ion (Cl - It is not advisable to add large amounts of sodium chloride to tube-fed formulas administered to patients because the patient cannot tolerate a large sodium chloride load. Some commercially available tube-fed formulas contain high concentrations of Na + and potassium ion (K + ) and therefore have sufficient ionic strength to allow reliable estimation of GRV using epigastric impedance techniques. One such formulation is Osmolite 1.2, which has a Na of 58 mEq / L. + and K of 46 mEq / L +Other commercially available tube feeding formulas contain relatively low concentrations of Na + and K + Because they contain sodium, they may not have sufficient ionic strength to allow reliable estimation of GRV using epigastric impedance techniques. An example of this type of tube feeding formula is Nutrihep, which has a Na of 7 mEq / L. + and K of 33 mEq / L + The ionic strength (and therefore conductivity) of the gastric contents depends not only on the ionic composition of the tube-fed formula, but also on the contribution of ions (H + , K + , C1 - ) secretion. It is therefore desirable to continuously monitor the conductivity of the stomach contents in order to determine whether the stomach contents at any given time have a suitable composition for determining the GRV. Furthermore, because calibration of the epigastric impedance monitoring system (by injecting a known amount of tube-fed formula into the stomach) is performed only intermittently, and the rate and composition of gastric secretion of ions can change on a minute-by-minute basis, it is useful to continuously adjust the GRV calibration setting to take into account measured changes in the conductivity of the stomach contents (relative to the value measured at the time of calibration).

[0090] D. Measuring Motility Using Impedance Sensors In an exemplary embodiment, an impedance sensor such as that described herein to measure reflux in the esophagus can be used in the stomach to measure the patient's motility. In one embodiment, this measurement can function in the same way as an impedance sensor in the esophagus. Two sensors in the stomach, food and gastric secretions, will typically have lower impedance readings than if food / secretion were not straddling the sensor. By measuring the pattern of impedance resulting from food entering the stomach and emptying into the small intestine, data can be created that can be interpreted as a measurement of motility. The timing, duration, sequence, and other measurements from the impedance sensor can be interpreted and correlated with either normal or abnormal motility. In an exemplary embodiment, measurements from the impedance sensor can be correlated with peristaltic waves in the stomach, which are a normal function of digestion. This information can be used by clinicians to modify nutritional delivery or potentially initiate other types of care. If the algorithm determines there is abnormal motility, nutritional levels can be automatically reduced to prevent the risk of aspiration. In another example, abnormal motility can cause aspiration of stomach contents.

[0091] This intragastric impedance sensor data can also be combined with esophageal sensor data so that the combination of motility and reflux data can automatically reduce feeding levels, trigger alarms, trigger suction, trigger balloons, etc. Conversely, the sensor data can cause an increase in feeding levels if the algorithm determines that the patient has good motility, does not have reflux, and is tolerating nutrition.

[0092] III. Backflow Measurement Systems and Devices Some embodiments relate to methods and devices for addressing reflux events in the esophagus, and more particularly, to determining the onset of a reflux event and taking therapeutic action.

[0093] A. Reflux Measurement System An exemplary device for monitoring reflux and providing some protection from aspiration is shown in FIG. 11. In this exemplary embodiment, a patient receives enteral nutrition using a feeding tube 102 into the stomach 103. The enteral nutrition is delivered via an enteral feeding pump tube 114 and a tube connector 112 and administered by an enteral feeding pump 116. The feeding tube 102 includes impedance sensors 1101-1108 located on the outside of the tube 102 and along the portion of the tube located in the esophagus 101. In the exemplary embodiment, there are eight impedance sensors 1101-1108 that include conductive electrodes to measure the impedance between two different sensors. If reflux extends to two sensors, the electrical impedance between the two sensors is reduced. This measured impedance difference is captured by the monitor 110 via the cable 108 and the electrical connector 106 that connects the impedance sensors 1101-1108 on the feeding tube 102 to the monitor 110. In certain situations, the patient may be at risk for immediate aspiration, so in an exemplary embodiment, the stomach contents are aspirated to prevent them from being aspirated. In this embodiment, suction is accomplished via a suction tube 1109 that is connected to the feeding tube 102 via a tube connector 112. The suction tube 1109 is connected to wall suction 1110 that passes through a monitor 110. The monitor 110 includes a valve that controls the level of suction from the wall suction 1110 that is applied to the suction tube 1109.

[0094] An exemplary process for using the device described in FIG. 11 is shown in FIG. 12. The first step 1201 of this exemplary process is to insert the feeding tube 102 into the patient. This can be accomplished by standard methods for inserting a feeding tube. In step 1202, the feeding tube 102 is connected to the monitor via cable 108, to wall suction 1110 via suction tube 1109 and tube connector 112, and to the enteral feeding pump 116 via enteral feeding pump tube 114. In step 1203, the enteral feeding pump 116 is started and enteral nutrition begins to flow through the enteral feeding pump tube 114 and through the tube connector 112 to the feeding tube 102. In step 1204, the monitor 110 continuously measures impedance data from the impedance sensors 1101-1108 on the feeding tube 102. In step 1205, the monitor 110 continuously analyzes changes in the impedance data to determine whether the changes correlate to a pattern indicative of reflux or swallowing. If the pattern is recognized as reflux, then suction can be initiated in step 1206. This suction is initiated by the monitor 110 opening a valve that allows wall suction through the suction tube 1109 and feed to the feeding tube 102 through the tube connector 112.

[0095] B. Feeding Tube Design An exemplary embodiment of a device that captures data in a reflux monitoring system is a feeding tube. In this embodiment, the feeding tube can be any related feeding tube used in acute care or used to provide enteral nutrition to a patient. In one exemplary embodiment, the feeding tube is size 14 Fr. and has an outside diameter of 4.7 mm. Other exemplary embodiments can include other feeding tube sizes, including but not limited to 10 Fr., 16 Fr., and 18 Fr. In an exemplary embodiment, the tube is in the form of a Levin feeding tube. This is a non-sterile standard Levin type feeding tube for nasogastric or orogastric insertion. Other exemplary embodiments can include other feeding tube configurations, including but not limited to Salem Sump style feeding tubes, Dobhoff feeding tubes, Keofeed feeding tubes, microporous feeding tubes, pediatric feeding tubes, and nasojejunal tubes. In one exemplary embodiment, the feeding tube is 48 inches (122 cm) long. Other exemplary embodiments can include other feeding tube lengths.

[0096] In an exemplary embodiment, the feeding tube is made from polyurethane. In another exemplary embodiment, the feeding tube is made from PVC. In another exemplary embodiment, the feeding tube is made from silicone. Other exemplary embodiments may include other feeding tube materials.

[0097] In an exemplary embodiment, the feeding tube has holes at the distal end of the tube to allow enteral nutrition to enter the gastric environment or to allow suction to remove stomach contents. These holes may be of different numbers, sizes and shapes and may further include a hole at the tip of the feeding tube.

[0098] In an exemplary embodiment, the tube includes radiopaque material to confirm placement within the stomach 103 and esophagus 101 using an x-ray. In an exemplary embodiment, radiopaque markings can be placed at 30 cm, 40 cm, 50 cm, and 60 cm from the distal end. Other exemplary embodiments can include other placements of radiopaque markings or include radiopaque material in the tube material. In an exemplary embodiment, the radiopaque material is placed along the length of the feeding tube, potentially incorporated into the feeding tube via a tube extrusion process. In another exemplary embodiment, an impedance sensor could potentially serve as the radiopaque marking. Other radiopaque materials and placements can be used. These radiopaque markings can be used in combination with other techniques to determine tube placement. For example, if a nomogram recommends a depth of 50 cm from the nose and the tube is inserted this distance, a plain x-ray film is more likely to show that the feeding tube is in the correct position. It is desirable for the impedance sensor to be sufficiently radiopaque to be visible on a plain x-ray film, e.g., a routine chest x-ray. Generally, correct position is defined as when all impedance sensors are located in the thoracic region of the esophagus, i.e., the sensor closest to the feet is above (and above) the stomach.

[0099] In an exemplary embodiment, it is desirable for half of the sensor to be on the carina (a distinct landmark on a chest x-ray) and the other half of the sensor to be below (lower) the carina but still above the diaphragm. A potentially accurate way to measure the degree of reflux is to measure based on the location of the carina. This device and method allows for reporting of the height of the reflux event not relative to the feeding tube, but rather relative to a fixed part of the body, e.g., the carina. In this exemplary embodiment, the feeding tubes have radiopaque markers that are numbered or otherwise distinguishable from one another. For example, the most distal sensor (closest to the foot) can be one bar. The next sensor can be two bars, so the most proximal (sixth sensor) can be six bars. After insertion to the recommended depth (using an acoustic sensor, nomogram, or other method), a simple x-ray may be taken. The acoustic sensor and its use described elsewhere herein may be implemented as all or part of the sensor 1111. The monitor then prompts the user to input the number of bars of the impedance sensor that are closest to and below the carina. The carina may be a preferred reference point since it is easily identified by most clinicians and is located approximately midway up the rib cage, thus representing approximately the halfway point of the esophagus. Once sensor information is input (as described above), the monitor can report whether reflux is occurring "below" or "above" the carina. Thus, instead of (or in addition to) reporting the height of reflux relative to the feeding tube, e.g., approximately 10 cm, the height report will relate to the approximate midpoint of the esophagus, with higher reflux, i.e., above the carina, being more extensive.

[0100] Another embodiment for verifying the position of the feeding tube is to measure the insertion of the tube relative to the location of the lower esophageal sphincter (LES). In an exemplary embodiment, a small balloon is incorporated into the feeding tube. This is similar in concept to an endotracheal tube. After inserting the feeding tube into the stomach, a high volume (e.g., 100 mL) low pressure balloon is inflated at or near the distal end of the tube. After inflation with 100 mL of air using a standard syringe, the tube is gently pulled until pressure is created by the balloon hitting the LES. It may be desirable for the balloon to be 10 or 15 cm from the tip of the feeding tube so that when resistance is met, the tube is taped in place, the tip of the feeding tube is known to be in the stomach, and the tube is permitted to administer food and medications to the stomach. Using this approach, it is desirable for the most distal (closest to the tip) impedance sensor to be located 5-10 cm from the area of ​​the balloon closest to the head. At the end of feeding tube placement, the balloon is deflated (i.e., removing the air) and the feeding tube is taped, sutured, or secured to the nose in the example of nasal insertion. This method and apparatus can precisely locate the LES and, more specifically, the length of the passageway from the tube insertion point (e.g., mouth or nose) to the LES. This approach can alleviate the need to confirm tube placement with an x-ray because feedback knowing the tube is located proximal to the LES can also be used to confirm that it is not in the lungs or coiled up in the stomach given the known length of the tube proximal to the balloon.

[0101] In an exemplary embodiment, the tube includes tube length markings or other indicia that indicate the length from the distal end of the tube and thus are used by the clinician to determine the length of tube to insert into the patient. For example, the tube length markings start at 25 cm from the distal end and go up to 85 cm in 5 cm increments. These tube length markings allow the clinician to determine how far the tube has been inserted into the patient. Other exemplary embodiments may include other tube markings.

[0102] An exemplary feeding tube may utilize sensors to measure potential reflux in a patient. In one embodiment, impedance sensors, which generally include a sensor material that is conductive, may be utilized to measure the impedance between two different sensors. In one example, as shown in FIG. 11, a bolus 1112 of stomach contents travels backwards down the esophagus 101 while simultaneously contacting multiple impedance sensors 1102, 1103, and 1104. The impedance between each adjacent pair of impedance sensors may be measured continuously. In an exemplary embodiment, this continuous measurement is performed at a frequency of 50 Hz. Other advantageous frequencies may be used for normal operation of the product. When the bolus 1112 straddles the two sensors 1102 and 1103, the electrical impedance between the two sensors 1102 and 1103 is reduced. This measurement of impedance between the two sensors may be referred to as measuring channel impedance. Additionally, in this example, the bolus 1112 straddles the sensors 1103 and 1104, reducing the impedance in this additional channel. In an exemplary embodiment, the impedance sensors 1101-1108 are spaced 2 cm apart. Other exemplary embodiments may include other spatial locations of the sensors. In an exemplary embodiment, the feeding tube 102 includes six channels, and therefore eight impedance sensors located approximately 25 cm to 50 cm from the distal end, i.e., sensor 1101 is located at 30 cm, sensor 1102 is located at 32 cm, sensor 1103 is located at 34 cm, sensor 1104 is located at 36 cm, sensor 1105 is located at 41 cm, sensor 1106 is located at 41 cm, sensor 1107 is located at 43 cm, sensor 1108 is located at 45 cm, and sensor 1109 is located at 47 cm from the distal end. These locations are taken as the location of the gastroesophageal junction, or LES, and are located approximately 25 cm from the distal end. Other exemplary embodiments may include other total numbers of impedance sensors and other locations of the sensors.

[0103] In one exemplary embodiment, the sensor 1111 can be implemented as a pH sensor 1111 placed at 0 cm or proximal, 0-5 cm, or 0-15 cm, at the distal end of the feeding tube as shown in FIG. 11. The pH sensor 1111 may be used to measure the pH of the stomach contents. In an exemplary embodiment, this pH sensor 1111 is used in conjunction with a medication to determine if the patient can tolerate enteral feeding. In this embodiment, the feeding tube can measure the pH change before and after administration of the medication.

[0104] The pH sensor 1111 can be placed at other locations along the feeding tube. One exemplary embodiment is to place the pH sensor 1111 approximately 25 cm from the distal end and use the sensor to measure pH and determine if reflux is present. This pH information can augment the impedance information or can be used independently. In an exemplary embodiment, if the pH drops at the same time that the impedance sensor measures a drop in impedance, the pH drop can be taken as additional evidence proving that reflux is present. Additionally, the pH sensor 1111 can provide a pH of the potential reflux that helps determine the relative acidity of the reflux. The acidity level can be used in determining the appropriate level of care. For example, reflux at a low pH can be more harmful to the esophagus and lungs, so specific treatments can be initiated, such as prescribing acid suppressants, prescribing prokinetics, or further elevating the head of the bed.

[0105] In an exemplary embodiment, the pH sensor 1111 meets the following specifications: The pH sensor material is made of antimony. The pH sensor 1111 can measure and display pH to at least one decimal point, i.e., xx. The sensor accuracy (offset) of the initial pH measurement may have a margin error of ±0.3. Subsequent pH measurements may have an accuracy of ±0.1. The pH sensor 1111 may have an internal reference for ease of use. The useful life of the pH sensor 1111 may be three days.

[0106] In an exemplary embodiment, the impedance sensor can take the form of metal rings that are applied to the feeding tube to measure the impedance between the metal rings. An exemplary material for these sensors may be stainless steel, although other exemplary metal materials that meet the impedance measurement requirements can be used. Impedance sensors that use metal rings, particularly stainless steel, can have a similar design to those provided in the Sandhill Scientific ZepHr catheters used to measure reflux to aid in the diagnosis of gastroesophageal reflux disease (GERD) (see http: / / www.sandhillsci.com / index.pHp?activePage=reflux$page=zprobes), but sized to wrap around a feeding tube of sizes 10-18 Fr.

[0107] In an exemplary embodiment, a metal ring is incorporated into the feeding tube 102 to measure the impedance of a patient receiving enteral nutrition. An exemplary embodiment for integrating a metal ring can be to create a feeding tube with two lumens. The main lumen is utilized to deliver food to the stomach and apply suction to remove stomach contents. The second lumen is utilized to route wires that connect to the metal ring to help complete the impedance measurement circuit. In this embodiment, the metal ring is attached by bending it onto the outside of the feeding tube, staying in place by friction, bonding via an adhesive material, or some exemplary combination. These metal rings can substantially wrap around, partially wrap around, or wrap the entire circumference of the feeding tube. In this embodiment, each wire that is brought out through the lumen is brought out through a hole in the feeding tube at each location of the metal ring and soldered to the metal ring. Exemplary embodiments can include various sizes, shapes, and different locations for the lumens to adequately connect the metal rings.

[0108] In an exemplary embodiment, the proximal end of the feeding tube has an electrical connector that connects the wires in the second lumen to a cable that allows connection to a controller or monitor. The electrical connector can connect these wires in a variety of ways.

[0109] In an exemplary embodiment, electrical connector 106 connects wires attached to sensors 1101-1110 to a cable 108 that connects to monitor 110. In an exemplary embodiment, this cable 108 is 2m long, although other exemplary lengths may be used. In an exemplary embodiment, this cable 108 has an RJ-45 connector on the end that connects to monitor 110, although other exemplary connectors may be used.

[0110] In an exemplary embodiment, as shown in FIG. 13, conductive ink is utilized as the sensors 1101-1110 instead of metal rings. In an exemplary embodiment, the wires 1301-1308 that connect to the sensors 1101-1108 are instead formed from conductive ink. Many different types of conductive inks can effectively collect this data. In an exemplary embodiment, the conductive ink used is AGCL-675 silver / silver chloride ink provided by a company called Conductive Compound. In these embodiments, the conductive ink is printed or applied directly to the surface of the feeding tube. In one exemplary embodiment, the conductive ink wires 1301-1308 and sensors 1101-1108 are applied to the thin film 1310-1311 by a printing process. The conductive ink can be applied by other exemplary processes such as pad, pen, inkjet, laser, screen printing, nano-based processes, and other processes that may be advantageous. An exemplary pattern for printing the conductive ink wires 1301-1308 and sensors 1101-1108 is designed so that the wires or sensors do not overlap on the printed thin film 1310-1311 surface. An exemplary design can be composed of different layers of ink and dielectric. One exemplary embodiment is to print these different layers as part of a printing process. An exemplary printing process is to first print the dielectric material in a pattern that matches the wiring pattern. In this exemplary process, if the design specifies sensors 1101-1108, the dielectric is not printed. In this exemplary process, the conductive ink wires 1301-1308 are printed on top of the dielectric pattern. In this exemplary process, the sensors 1101-1108 are printed on the thin film 1310-1311 so as to contact the conductive ink wires 1301-1308. In this exemplary process, an adhesive material is then printed on top of the wires 1301-1308 and sensors 1101-1108.

[0111] In an exemplary process, the conductive ink wires 1301-1308 and sensors 1101-1108 are affixed to the feeding tube 102 via a combination of pressure and heat. In this exemplary process, a specific mold is created for the size of the tube 102 to which the conductive ink will be applied. The conductive ink film 1310-1311 and tube 102 are placed into the mold and then heat is applied to activate the adhesive material. The mold also applies pressure, forcing the conductive ink onto the tube 12. After this process, the film 1310-1311 is removed from the tube 102, leaving only the printed conductive ink and dielectric material on the tube 102. The resulting tube 102 includes multiple sensors 1101-1108 affixed to the tube and exposed to the outside through openings in the dielectric material. Each of the multiple sensors 1101-1108 is connected to a corresponding one of the conductive ink wires 1301-1308 and is also affixed to the outer surface of the tube, but is insulated from the outside environment from a dielectric material.

[0112] The size and shape of the conductive ink sensors can take many exemplary forms. In one exemplary embodiment, the sensors 1101-1108 are in the form of a rectangle that covers a portion of the circumference of the tube 102, as shown in FIG. 13. Other exemplary shapes, such as squares, ovals, circles, etc., can be used. In FIG. 13, an exemplary approach to connect the sensors 1101-1108 to the monitor 110 is via conductive ink wires 1301-1308 that traverse the tube from the sensors 1101-1108 to the electrical connector 106. An exemplary pattern of the conductive ink wires 1301-1308 runs parallel to the length of the membranes 1310-1311 and connects to the sensors 1101-1108 via right angles. There could be other exemplary patterns for efficiently printing the conductive ink wires 1301-1308 on each sensor 1101-1108. An exemplary thickness of the conductive ink wires is about 0.020 inches, although other thicknesses could be used.

[0113] The size and shape of the membranes 1310-1311, conductive ink wires 1301-1308 and sensors 1101-1108 are printed and the number of sensors 1101-1108 printed will vary depending on the size of the tube 102, the location of the sensors 1101-1108 to capture the sensor data, and the number of sensors 1101-1108 needed to capture the data. An exemplary size and shape is shown in FIG. 13 where two conductive ink membranes 1310-1311 may be used to capture the required sensor data. In this exemplary embodiment, the tube 102 with the conductive membranes 1310-1311 applied is a 14 Fr. Levin tube with an outer diameter of 4.67 mm (3 / 16 inch) and a length of 122 cm (48 inches). In this exemplary embodiment, each of the membranes 1310-1311 can cover an arc of 120 degrees when placed in a 14 Fr. tube with a membrane width equal to 4.92 mm (0.193 inches). The first membrane 1310 can be 50 cm (19.66 inches) long and the second membrane 1311 can be 62 cm (24.41 inches) long. Each membrane can include four impedance sensors, allowing for data collection of three sensor channels, with two adjacent sensors being able to form a channel.

[0114] The positioning of each membrane 1310-1311 depends on factors such as the length and area of ​​the tube being monitored. In this exemplary embodiment, the proximal ends of both membranes 1310-1311 can be positioned starting 90 cm from the distal end of the feeding tube. In this exemplary embodiment, each membrane 1310-1311 can be positioned at a 180 degree angle relative to the other membrane so that they effectively cover opposite sides of the tube. This embodiment should allow for efficient capture of data and optimal positioning of the membranes 1310-1311 for ease of manufacturing.

[0115] In this embodiment, the first sensor 1101 may be placed approximately 30 cm from the distal end. This location should be advantageous since the lower esophageal sphincter is located approximately 25 cm from the distal end. Thus, reflux is measured starting 5 cm above the lower esophageal sphincter. By comparison, the clinical diagnosis of GERD is reflux reaching 5 cm above the lower esophageal sphincter. In this embodiment, each impedance sensor is placed approximately 2 cm from each other.

[0116] The membranes 1310-1311 are located at 90 cm into the proximal end of the tube 102, near which the membranes 1310-1311 are located. A conductive ink can be designed and applied to facilitate connection to the electrical connector 106 and cable 108. The conductivity sensors 1101-1108 and wires 1301-1308 must be connected to the electrical connector 106, which is part of the cable 108 that in turn is connected to the monitor 110. A specially designed conductive ink pattern would facilitate connecting the conductive ink wires 1301-1308 to this electrical connector 106. In an exemplary embodiment, the electrical connector 106 has conductive connection points along the inner diameter that, when placed on the outer diameter of the tube 102, make electrical contact with the conductive ink pattern and complete the electrical circuit.

[0117] C. Monitor Cable Design In an exemplary embodiment, a cable 108 is used to connect the monitor 110 to the feeding tube 102. In this exemplary embodiment, this cable 108 is approximately 2m long. At one end of the cable 108, a female RJ-45 connector can be connected to a male RJ-45 from the electrical connector 106. At the other end of the cable, the male RJ-45 can be directly connected to the monitor 110. The cable 108 can have protective materials suitable for a clinical setting, such as being resistant to body fluids. The cable 108 is meant to be reusable.

[0118] D. Suction and Enteral Feeding Pump Design The tube connector 112 connects the feeding tube 102 to a tube that leads to the enteral feeding pump 116 and wall suction 1110. In an exemplary embodiment, the feeding tube 102 is used to deliver enteral nutrition and to allow for suction of stomach contents. In the exemplary embodiment shown in FIG. 14a, the bottom 1402 of the connector 112 can be connected to the feeding tube 102. The right side 1404 of the connector 112 connects to the feeding pump tube 114 that leads to the enteral feeding pump 116. The left side 1410 of the connector 112 connects to the suction tube 1109 that leads to the wall suction 1110. Enteral nutrition travels from the enteral feeding pump 116 down the enteral feeding pump tube 114 to the tube connector 112 and then into the feeding tube 102. The particular path of the enteral nutrition in the connector 112 is that the enteral nutrition enters the connector 112 at point 1412, and as the nutrition passes through corner 1406, some of the tubing may go to the left side 1410 of the connector, but the nutrition is blocked by the valve 1408, which is closed. The enteral nutrition blocked by the valve 1408 returns to the bottom 1402 through point 1416. The valve 1408 can take many exemplary forms with the important operating criteria being that when suction is applied, the valve is pulled open, but when fluid tries to force into the valve, it remains closed under a large pressure difference between the suction and the enteral nutrition pump. Many typical valves can meet these criteria, such as the umbrella valve shown in Figures 14A and 14B, including but not limited to butterfly valves, Belleville valves, and duckbill valves. In some examples, a deformable suction force may be created on the side of the vacuum pump that collapses due to the pressure difference between the suction force and atmospheric pressure. This deformable region may allow the check valve to open in a deformed state or may allow for less stiffness.

[0119] In the exemplary embodiment shown in FIG. 14A, suction can be applied to remove stomach contents. Wall suction 1110 is controlled in the monitor 110 to an on or off setting. After suction is turned on, valve 1408 opens, allowing for the suction and removal of all stomach contents. These stomach contents are sucked up into the lumen of the feeding tube 102 in a retrograde motion and into the connector 112. Once in the connector 112, these stomach contents first pass point 1418. They are then pulled to the left side 1410 and pass point 1420. They then continue around the valve 1408, past point 1422, and into a collection trap at the wall suction 1110 or monitor 110. In this view, valve 1408 is in an open position due to the suction force. When suction is on, any tube feed that may be coming from the enteral feeding pump can also be sucked into the suction tube 1109. Specifically, the tube feed enters the right side 1404 and passes through point 1412. Suction then pulls all or part of the tube 1406 around corner 1406, through point 1414, and continues around valve 1408 and through point 1424. This tube-fed suction is intermittent so is not harmful to the patient and allows the clinician to decide to stop or change the rate of administration of the tube feed. This connector 112 is designed to attach to the feeding tube 102 and is therefore disposable along with the tube.

[0120] E. Monitor design The monitor 110 can include a computer (e.g., a controller) and a display. The computer can be programmed (e.g., has access to software programs) to monitor the patient's condition by receiving sensor data as described herein, and to initiate and control operation of the device as described herein (e.g., providing commands or other signals to servos, pumps, voltage supplies, etc.). The monitor 110 can include a user interface for inputting data and commands into the monitor 110, such as a touch screen display, a mouse, a track pad, a keyboard, a microphone and voice recognition software, buttons, etc.

[0121] "Computer" refers to one or more devices and / or one or more systems capable of accepting structured input, processing the structured input according to predetermined rules, and producing a processed result as output. Examples of computers include fixed and / or portable computers; computers with single processors, multiple processors, or multi-core processors that may or may not operate in parallel; general-purpose computers; supercomputers; mainframes; workstations; microcomputers; controllers; servers; clients; interactive televisions; web appliances; telecommunications devices with Internet access; hybrid combination computers and interactive televisions; portable computers; tablet personal computers (PCs); personal digital assistants (PDAs); mobile phones; application specific hardware (DSPs), field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific instruction set processors (ASIPs), chips, chips, or chip sets for emulating computers and / or software; system-on-chips (SoCs), or multiprocessor systems-on-chips (MPSoCs), etc.

[0122] "Software" refers to predetermined rules for operating a computer that are stored on a computer-readable medium. Examples of software can include code segments, instructions, applets, pre-compiled code, compiled code, interpreted code, computer programs, and programmed logic.

[0123] "Computer-readable medium" refers to any storage device used to store data accessible by a computer. Examples of computer-readable media include magnetic hard disks; floppy disks; optical disks such as CD-ROMs and DVDs; magnetic tape; flash removable memory; memory chips; and other types of media capable of storing machine-readable instructions.

[0124] A "computer system" refers to a system having one or more computers, each of which may include a computer-readable medium embodying software that operates the computer. Examples of computer systems include a distributed computer system that processes information via computer systems linked by a network, and two or more computer systems connected to each other via a network to transmit and / or receive information between the computer systems, and / or one or more systems that receive data, process the data according to one or more stored software programs, and generate results, and that may typically include input, output, memory, arithmetic, logic, and control units.

[0125] A "network" refers to a number of computers and related devices that may be connected by communication facilities. A network may include permanent connections such as cables or temporary connections such as those made through telephone or other communication links. A network may further include wired connections (e.g., coaxial cable, twisted pair, optical fiber, wave guide, etc.) and / or wireless connections (e.g., radio frequency waveforms, free space optical waveforms, acoustic waveforms, etc.). Examples of networks include the Internet, such as the Internet, intranets, local area networks (LANs), wide area networks (WANs), and combinations of networks such as the Internet and intranets. Exemplary networks may operate on any of a number of protocols, such as Internet Protocol (IP), Asynchronous Transfer Mode (ATM), and / or Synchronous Optical Network (SONET), User Datagram Protocol (UDP), IEEE 802.x, etc.

[0126] The monitor 110 can perform several functions: For example, the monitor 110 can function to analyze reflux data, present a summary to the clinician in a simple and intuitive manner, analyze reflux data in real time, and initiate automatic aspiration if warranted.

[0127] The specific design of the monitor and display may also differ from existing GERD related products that use impedance sensors. Physical design requirements may include a display and pole mount connector that is useful in an ICU or acute care setting. Data display may include both an overview of reflux and aspiration events as well as the ability to view the raw data captured by the sensor. For the reflux event summary, the data may be presented in text and / or graphical form as presented in the exemplary embodiment shown in FIG. 15. In this exemplary embodiment, viewing a specific period when impedance data was collected may be set by input 1502 to the last 3, 6, 12, or 24 hour period. In this exemplary embodiment, text may be presented as a summary of the number of reflux and aspiration events over the past 24 hours and the range of reflux event heights. For example, display 1504 indicates the number of times aspiration was triggered. The total number of reflux events in the last 24 hours is displayed in display 1506, as well as an overview of how many reflux events reached a particular height. The total number of swallowing events during a 24 hour period is shown on display 1508 and the number of burping events is shown on display 1510. An option to provide further information regarding the patient history is to have an arrow next to the number of events indicating whether the incidence of reflux is increasing (up arrow) or decreasing (down arrow).

[0128] In graphical form, time may be represented on the x-axis, as shown in display 1512, and reflux height may be represented on the y-axis, as shown in display 1514. A summary of impedance data determined to be a reflux event is represented by an arrow, such as in display 1516, positioned at the time of the reflux event on the x-axis, and with the reflux height represented as the length of the arrow along the y-axis. Aspiration events may also be recorded on the y-axis, as in display 1518. Aspiration events or high levels of reflux may be indicated by a visual alarm condition, such as a red circle in display 1520. Areas of display 1520 may also be used to communicate non-alarm conditions, such as a green colored circle indicating that all measurements represent a normal or safe condition. Similarly, low levels of reflux or other combinations of measurements may be represented by a yellow colored circle indicating caution. Swallowing events may be displayed, as in display 1522, and burping events may be displayed, as in display 1524. The monitor allows scrolling through periods and zooming in on a particular period (zooming in on the selected period) to view in more detail. The monitor may also allow for the entry of other relevant data, such as when a bolus delivery occurred, when there was a relevant event such as saliva ingestion / vomiting, or when certain gastrointestinal related medications were ingested, when a bolus delivery occurred. These additional data can help put the impedance data in a better context and aid the clinician in understanding the patient's condition. In addition to the impedance data, the display can show a summary view of current and historical pH data for both the esophageal and gastric pH sensors.

[0129] In an exemplary embodiment, the monitor 110 may provide access to an interface that allows for setting preferences for the monitor 110 and the feeding tube 102, as shown in FIG. 16. For example, setting preferences may include actions such as determining whether to monitor swallowing, such as via input 1602. Setting also includes determining whether an alarm should be initiated, as well as what type of alarm, such as via input 1602. Other alarm settings include the threshold at which an alarm is initiated, such as via input 1606, and the volume of the alarm, such as via input 1610. The volume can be adjusted, as can the volume of the alarm, such as via input 1606. Setting also includes configuring an automatic aspiration threshold, such as via input 1608. For example, the threshold may be configured to be automated, which is a combination of factors, or factors such as reflux measured as greater than 10 cm, greater than 15 cm, or greater than 5 cm for more than 20 minutes, specifically.

[0130] In an exemplary embodiment, the detailed impedance and pH data is recorded to a storage medium for later analysis. This storage medium may be a flash card or something that is easy to access and transfer to a PC for further analysis. Via the offline PC, the clinician can view the detailed impedance data that has been collected since the measurement was initiated. Viewing the data offline on the PC, the clinician can enter the reflux event into the monitor 110 to add and store with other noted reflux events.

[0131] In an exemplary embodiment, the monitor form factor may be a small LCD or similar display suitable for reading. The monitor diagonal is a minimum of 3.5 inches with a minimum resolution of 320x480 pixels. The monitor may have a flat bottom so it can be placed on a shelf. A clamp accessory allows it to be connected to a rolling IV type pole.

[0132] The monitor 110 can operate on wall current and have a battery backup that includes a replaceable battery. In another exemplary embodiment, the monitor 110 can have a battery backup that includes an internal rechargeable battery.

[0133] In an exemplary embodiment, hardware buttons are designed to facilitate both acquisition and review of information. These buttons can facilitate capture of events such as feeding, reflux, vomiting, feeding intolerance, and medication administration events. These buttons also have standard inputs for navigating and selecting items within the monitor's UI. The buttons and monitor's user interface can allow for entry of patient name and medical record number.

[0134] In an exemplary embodiment, the screen is touch-enabled, allowing direct interaction with the software user interface via touch gestures on the screen. The monitor also has a combination of touch screen and hardware button interaction.

[0135] In an exemplary embodiment, the electronics of the monitor can be integrated into the electrical connector 106, the tube connector 112, or an alternative device such as a cloud-based computing device. In an exemplary embodiment, the electrical connector 106 can have all the electronics built into its package. This includes all the processing, memory, and data connections. In this scenario, the processing of the impedance data can occur in the electrical connector 106. The output of this processing can then be managed in multiple ways. For example, if during the processing of the impedance data an algorithm needs to be initialized to determine automatic suction, a solenoid valve can be integrated directly into the electrical connector 106 to initiate suction. In this embodiment, the electrical connector 106 is no longer a disposable portion of the tube, but instead is reusable. Another way that the data can be managed is by viewing summary data on an alternative device. This alternative device can be a PC, a cell phone, a tablet, an enteral feeding pump, a modular patient monitor, or other device where summary data can be viewed. All the setup and management functions for the feeding tube 102 previously described as occurring on the monitor 110 can instead be accomplished through the alternative device.

[0136] In this embodiment, power can be provided to the electrical connector 106 to power the electronics. One option is to have a power cord that connects the electrical connector 106 to a wall outlet. This power cord can advantageously be attached to the suction tube 1109. Alternatively, power can be harvested from a number of potentially advantageous mechanisms such as piezoelectric, thermoelectric, solar cell, battery technology, in combination with low voltage processing and memory technology. Thermoelectric, solar cell, battery technology, etc. In one exemplary embodiment, the battery can be a standard battery located within the electrical connector 106.

[0137] IV. Impedance-Based Algorithm A. Data Collection for Algorithms An exemplary device utilizes eight impedance sensors, consisting of two thin films with four impedance sensors, as shown in FIG. 13. These impedance sensors are placed approximately 2 cm apart. Two impedance sensors form one channel for data collection. Thus, there are three channels out of four impedance sensors. Impedance is always measured between two sensors in each channel. An exemplary process for collecting data from these impedance sensors is shown in FIG. 17.

[0138] The first step 1702 in this process is to capture data from all impedance channels. The data collected from the impedance sensors is a measurement of ohms between two sensors. The sensors are not necessarily adjacent along the feeding tube. Thus, in the exemplary device, eight impedance sensors collect data as six channels. This data takes into account factors such as slight changes in the esophageal environment, which naturally result in small variations in normal conditions within the esophagus. These small changes can be considered noise from an interpretation standpoint, so the raw data must be smoothed in step 1704 in order to be processed by the algorithm. Smoothing, a form of filtering, is the process of removing these small changes in the data so that the data can be more easily processed by algorithms that determine patterns associated with specific conditions such as liquid reflux, gas reflux (burping), swallowing, or any combination. There are many exemplary techniques for data smoothing that can be utilized in this embodiment, including, but not limited to, moving average, least squares, exponential smoothing, and LOESS / LOWESS regression. The output of this smoothing step is to create an impedance measurement that can be used by the algorithm.

[0139] In an exemplary embodiment, the impedance data smoothing is calculated using an exponential moving average, as represented by the following formula: B t =αxI t +(1-α)xBt-1

[0140] The coefficient α represents the degree of weighting reduction. The coefficient α is a constant smoothing coefficient, and the higher the α value, the sooner older impedance measurements are discounted. The variable I t is the impedance measurement at any time t. The variable B t is the impedance measurement obtained after data smoothing at any time t.

[0141] Thereafter, in step 1706, the impedance measurements may be analyzed to provide information regarding the patient's condition. In an exemplary embodiment, the derivative of the impedance function above may be calculated to provide an indication of the sign of a change in the impedance measurements. One exemplary method for calculating the derivative of the function Bt is according to the following equation (2) using Leibniz notation:

[0142]

number

[0143] The derivative of the impedance can provide additional information that is useful in understanding how quickly the impedance measurement is falling and therefore whether a fluid reflux event may be occurring. It can also indicate whether the impedance has reached a minimum or maximum value.

[0144] In another exemplary embodiment, the above B t The second derivative of the function can be calculated to provide an indication of when the impedance reaches a minimum relative to a maximum. The shorter the time to reach the lowest impedance measurement, the better indicative of a reflux event, and may indicate a stronger or faster reflux event that could potentially put the patient at risk for aspiration.

[0145] One exemplary method for calculating the second derivative of a function B is to use the following equation (3) using Leibniz notation:

[0146]

number

[0147] In an exemplary embodiment, the percent change in impedance measurement is calculated to determine if there is an increasing or decreasing trend in impedance. One exemplary method for calculating the impedance change rate is as follows:

[0148]

number

[0149] In this exemplary embodiment, factor n, which indicates the start time for calculating the summation, and factor m, which indicates the end time for calculating the summation, can be determined by many advantageous means. In one exemplary embodiment, the period of n or m can be calculated based on when the sign changes in the percent change calculation. In another exemplary embodiment, the factor can be calculated based on the second derivative of the impedance measurement, since the second derivative refers to when the impedance measurement reaches a local minimum. In another exemplary embodiment, factor n can be a fixed difference with factor m, where the values ​​of the impedance measurement at time n and m are compared. If a predetermined threshold based on the difference in the impedance measurements at time n and m is exceeded, n is set as the start period of the summation. For example, the difference between time n and m can be set as a fixed number, such as (m-5) seconds. If the ratio of the resulting impedance measurements at time m over time n is 0.75, then time n is set as the start point of the summation.

[0150] After the change in impedance has been calculated for each channel, this change data is compared across all eight channels in step 1708. For example, the time interval of any change in baseline impedance in one channel is compared to the time interval of baseline impedance change in the other channels.

[0151] The changes in baseline impedance measurements for each channel are continuously processed by an algorithm to determine if the impedance changes meet a definition of a condition, such as liquid reflux, gas reflux (burp), swallowing, or any combination. If the algorithm determines that the condition definition is met, this information is then displayed on a monitor in step 1710, indicated as an alert, or processed by the algorithm to determine further action, and can be acted upon in a number of ways.

[0152] B. Algorithm for detecting fluid reflux The use of impedance sensors to measure reflux is well established with products used to diagnose gastroesophageal reflux disease (GERD). The measurement principle of impedance sensors is that the impedance measured between two adjacent sensors decreases as reflux passes through these two sensors. The impedance data collected from the two sensors is defined as a channel. As described by Zerbib. Frank el al. “Normal Values ​​of PHaryngeal and EsopHageal Twenty-four-Hour pH Impedance in Individuals on and off Therapy and Inierobserver Reproducibility.” Clin Gasimenterol Hepatol. 2013 Apr;11(4):366-72 (hereinafter “Zerbib”), which is incorporated herein by reference in its entirety, liquid reflux is generally defined as a retrograde 50% drop in the measured impedance in at least two adjacent channels. This definition of reflux is based on relatively healthy patients diagnosed with GERD. Zerbib also explains how only impedance drops lasting 3 seconds or longer are counted.

[0153] An exemplary liquid reflux manifestation is shown in FIG. 18. In this figure, the x-axis represents time and the y-axis represents the impedance measurements for each channel 1801-1806. In this exemplary embodiment, the six channels represent the eight impedance sensors 1101-1108. Specifically, channel 1 1801 represents the impedance measurements for impedance sensors 1101 and 1102. Similarly, channel 2 1802 represents the impedance measurements for sensors 1102 and 1103, channel 3 1803 represents sensors 1103 and 1104, channel 4 1804 represents sensors 1105 and 1106, channel 5 1805 represents sensors 1106 and 1107, and channel 6 1806 represents sensors 1107 and 1108. As impedance is measured in channel 1 1801 at time 1 1810, the impedance measurement begins to drop. The impedance measurement for channel 1 1801 reaches a minimum at time 2 1812. If the difference in impedance between time 1 1810 and time 2 1812 is greater than 50%, it may indicate that reflux has been detected in channel 1 1801. A similar pattern of impedance measurement drops is seen in channels 2 1802, 3 1803, and 4 1804. Because the time of the impedance drops is delayed in each successive channel, it may indicate that reflux has moved back up the esophagus over time and is now present at locations 1801-1804 in channels 1-4. At time 3 1814 in channel 1 1801, the impedance measurement begins to increase. This increase and leveling out of the impedance measurement may mean that reflux is no longer present at the location of channel 1 1801. This increase in impedance measurement begins first in channel 4 1804 and then continues in channels 3, 2, and 1 1803-1801. This shows that the reflux reached a maximum height at the location of channel 4 1804 and then began to descend in an antegrade motion through the locations of channels 3, 2 and 1. Figure 18 shows a typical reflux event, where the reflux is seen to travel retrogradely up the esophagus and then antegrade back into the stomach.

[0154] The same impedance measurement principles can be applied to measure reflux in acute patients, although algorithms may need to be adjusted to take into account the unique parameters and conditions of acute patients.

[0155] For example, in an acute care environment, the focus is on protecting the patient from the imminent threat of reflux, potentially leading to aspiration of gastric contents. This immediate threat contrasts with the existing use of impedance measurements and algorithms to diagnose GERD, which are non-real-time analyses that take hours or days after collecting all impedance data from the patient. Thus, measurements that would trigger an alarm or aspiration event in an acute care setting may be at a lower threshold to ensure the patient is safe. For example, in an exemplary embodiment, liquid reflux may be defined as a retrograde 30% drop in measured impedance from the combination of two distal sensors compared to at least the next one or two proximal sensors. This definition may improve how potential reflux events are captured and processed in the algorithm.

[0156] This definition can also account for the fact that many acute care patients take acid suppressing medications such as proton pump inhibitors and H2 blockers, which will result in an overall higher pH value in the acute care patient. This higher pH fluid is typically not as conductive as a lower pH fluid, potentially resulting in a smaller impedance change. The level of impedance may change over time given the changes in materials in the gastric environment. Various medications, foods, and the changing condition of the acute care patient may also affect the impedance measurement.

[0157] A key difference in how existing impedance measurement systems work in identifying GERD is that the data is analyzed offline, hours or days after a reflux event has already occurred, and is not processed in real time. Thus, current algorithms designed for GERD diagnosis are defined to identify the entire reflux episode from reflux onset to end. The emphasis in GERD diagnosis is to ensure that the data is accurate in diagnosing the GERD condition and to drive decisions regarding medication use, such as acid suppressants, and diet. In contrast, in an acute care setting, data must be processed in real time, and the decision to initiate an alarm or suction must be made quickly to reduce the risk of aspiration. Thus, in an acute care setting, the emphasis is on determining whether reflux has potentially started in each channel, and not waiting to determine whether it has ended. These are key differences between state-of-the-art impedance measurement systems and the proposed embodiment.

[0158] Given the importance of determining whether reflux has begun, in an exemplary embodiment, it may be beneficial to use a probability analysis to determine the relative probability that reflux has begun. For example, impedance measurements that show a larger impedance drop over time may be assigned a higher probability. This may be done in a stepped manner such that the larger the drop in impedance measurement, the higher the assigned probability. In contrast, smaller impedance drops may be assigned a lower probability. This probability analysis may also take into account measurements from multiple sensors. For example, as shown in FIG. 18, when there is a progression of lower impedance measurements starting from the distal channel and continuing to the more proximal channels, it is possible to strongly assign a higher probability to measurements from each channel, since data from multiple channels reinforces the definition that a reflux event has occurred. In contrast, if only the proximal impedance channel shows a suddenly low impedance measurement and other adjacent impedance channels do not indicate reflux, the measurements may be assigned a lower probability.

[0159] C. Gas Reflux or Burp Detection Algorithm Similar devices and methods of use can also be used to detect gas reflux, often referred to as burping or eructation. In the proposed embodiment, air or burping gas can be discriminated because burps are very poor conductors and therefore typically cause an impedance increase (e.g., from 4000 to 5500) versus the impedance decrease caused by a much more conductive liquid (e.g., from 4000 to 2000). Gas reflux is traditionally defined as a rapid (3Kohm / s) increase in impedance >5Kohm occurring simultaneously in at least two impedance channels, as described by Zerbib. An example of gas reflux is shown in FIG. 19.

[0160] In this diagram, the x-axis represents time and the y-axis represents the impedance measurements for each channel 1801-1806. In this exemplary embodiment, the six channels represent the eight impedance sensors 1101-1108. When impedance is measured at time 1 1910 on channel 1 1801, the impedance measurement increases very quickly. At time 2 1912, the impedance measurement then drops very quickly. The impedance measurements for channels 2-6 1802-1806 also increase and decrease at time 1 1910 and time 2 1912, respectively. This pattern can signify a burp event, as the impedance rises very quickly and simultaneously across each channel, representing gas from a burp rapidly regurgitating back up the esophagus.

[0161] Detecting gas reflux in a patient can be beneficial by allowing detection of patients with gas-forming bacteria in the stomach or small intestine. This can be an indicator of non-resident bacterial overgrowth that causes other symptoms (e.g., bloating) and signs (e.g., diarrhea). Burping is a sign of tube-feeding intolerance. Thus, patients who exhibit excessive burping may require different treatments depending on the clinician. Treatment may generally follow measures for tube-feeding intolerance, such as reducing tube feeding, elevating the head of the bed, and administering prokinetic drugs.

[0162] D. Swallowing Detection Algorithm The same device for measuring reflux is also capable of detecting, recording and reporting swallowing events. Swallowing is the antegrade movement of conductive material such as saliva, food and drink down the esophagus. Typical swallowing impedance measurement data is shown in Figure 20.

[0163] In this diagram, the x-axis represents time and the y-axis represents the impedance measurements for each channel 1801-1806. In this exemplary embodiment, the six channels represent the eight impedance sensors 1101-1108. The impedance measurement for channel 6 1806 begins to drop at time 1 2010. The first change in impedance measurement comes from proximal channel 6, indicating that bolus material, such as food or liquid, is moving antegrade from the oropharynx down the esophagus. The impedance measurement for channel 6 1806 reaches a minimum at time 2 2012. If the difference in impedance between time 1 2010 and time 2 2012 is greater than 50%, it can indicate that bolus material has been detected in channel 6 1806. A similar pattern of drop in impedance measurements is seen for channels 5 1805, 4 1804, 3 1803, 2 1802, and 1 1801. Since the impedance drop is delayed in time for each successive channel, it can mean that the bolus material is moving antegrade down the esophagus over time and is present in all six channels 1801-1806 successively. At time 3 2014, in channel 6 1806, the impedance measurement begins to increase. This increase continues to time 4 2016, and then the impedance measurement levels off. This increase and leveling off of the impedance measurement can mean that the bolus material is no longer present at the location of channel 6 1806. This increase in impedance measurement starts first in channel 6 1806, then continues with channels 5, 4, 3, 2, and 1 1805-1801. This means that the bolus material is moving from channel 6 1806 and falling in a motion antegrade and through the locations of channels 5, 4, 3, 2, and 1 1805-1801. FIG. 20 illustrates a typical bolus swallowing event, in which the bolus material is seen moving antegrade down the esophagus and into the stomach.

[0164] Understanding the frequency and pattern of swallowing can be useful to clinicians. For example, it can be a sign that they are becoming more conscious. This can be important for patients who are sedated in the ICU, where the level of sedation and consciousness needs to be closely monitored to titrate the administration of sedative medication. If a patient requires paralysis, for example, due to life-threatening hypoxemia, the frequency of swallowing can also be used to titrate the administration of paralytic medication, e.g., ciscalicurium, rocuronium, since the onset of swallowing reveals the wear-off of the desired paralysis. In another example, patients after traumatic brain injury or after severe stroke may be in a coma and also have swallowing disorders. Seeing the resumption of swallowing or an increase in frequency can be an important clue to clinicians that the patient is recovering neurological function. In contrast, the inability to resume such swallowing can be a potential sign that the brain injury is not improving.

[0165] E. Mixed State Detection Algorithm The algorithm needs to account for mixed condition scenarios. For example, a patient who is swallowing may also be regurgitating gastric contents at the same time. An example of an impedance measurement showing both swallowing and regurgitation is shown in Figure 21.

[0166] In this diagram, the x-axis represents time and the y-axis represents the impedance measurements for each channel 1801-1806. In this exemplary embodiment, the six channels represent the eight impedance sensors 1101-1108. The impedance measurement for channel 6 1806 begins to drop at time 2110 and begins to plateau at time 3 2114. The first change in impedance measurement comes from proximal channel 6, signifying a swallow; that is, the bolus material is moving antegrade, from the oropharynx down the esophagus. At time 2112, the impedance measured for channel 1 1801 begins to drop and then plateaus at time 4 1116. The change in channel 1 1801 signifies the presence of reflux. Channels 5 1805 and 4 1804 also indicate a swallowing event. Channels 2 1802 and 3 1803 indicate the presence of reflux. FIG. 21 shows a combined event where swallowing and regurgitation occur at approximately the same time.

[0167] Swallowing measurements can potentially mask reflux events, therefore it is important to ensure that reflux is accurately assessed in these mixed conditions as patients may be at risk for aspiration.

[0168] Another example of a mixed condition is a combination of liquid and gas reflux, or mixed reflux. This mixed reflux can be measured as gas reflux occurring just before or during liquid reflux measurements. In an exemplary embodiment, additional algorithms can be created to correlate gas reflux with liquid reflux. For example, if there is a pattern where gas reflux occurs before liquid reflux, intervention could potentially be initiated before liquid reflux is measured. Another exemplary embodiment is the correlation of swallowing and liquid reflux. The lack of swallowing measurements can indicate that the patient is at higher risk for aspiration. Thus, intervention could be initiated early or quickly, based on alternative interpretations of potential reflux.

[0169] F. Algorithm for Smart Alarms Alarms can be useful to warn of potential aspiration based on reflux and other measurements. The device has the option to turn on one or multiple alarms. For example, an alarm can be triggered for any reflux event. However, this can lead to "alarm fatigue" in patients with multiple small reflux episodes. It is therefore desirable to allow customization of alarms based on clinician preferences for a particular patient. For example, it may be desirable to set thresholds to trigger an alarm if any of the following conditions are met: 1) any reflux event of at least 10 cm in excursion / height, 2) the presence of at least five reflux episodes less than 10 cm in height over a 6-hour period, 3) the continuous presence (for at least 15 minutes) of conductive material (possibly liquid) over the sensor closest to the head, 4) rapid detection of impedance drop in multiple channels.

[0170] There are options for visual alarm only, audio alarm only, or a combination of visual and audio alarm. The visual alarm can be configured with a flashing red light that is part of the user interface, as shown in Figure 15. There is an option that allows customization of the sound level of the audio alarm. Additionally, there are options for various levels of alarm based on the nature of the reflux. For example, it may be desirable to have a visual alarm only for non-worrisome reflux events, such as those less than 5 cm in height. However, if a reflux event between 10-15 cm in height is observed, this may trigger the addition of an audible alarm. The system is also capable of allowing step escalation of the alarm volume. For example, if the "alarm silence" button is not enabled to indicate that the alarm is sounding, the alarm volume can be step escalated over 5 minutes to maximum volume. The alarm status can also be wirelessly transmitted, for example, to a nurse's station, cell phone, PC, enteral feeding pump, modular patient monitor, or other device. In addition to the use of reflux frequency and height, the alarm trigger threshold can also take into account data such as pH data, nutritional supplementation levels, levels of exercise, and the patient's specific data, i.e. medical condition, age, weight, etc.

[0171] V. Aspiration Prevention Interventions There are several approaches to preventing aspiration in enterally fed patients, including "passive" and "active" systems.

[0172] Passive systems simply provide information to the clinician and rely solely on the clinician's response to this information to modify patient management. In one example, the feeding tube continuously records the presence of conductive material (e.g., gaseous contents) in the esophagus and a pattern of retrograde bolus movement consistent with reflux of gastric contents is observed. These data are displayed on a monitor. If the clinician has concerns about these data, patient management can be modified. Some common responses include, but are not limited to, one or more of the following: 1) temporarily halting or reducing the rate / volume of tube feed; 2) initial administration of a prokinetic agent, e.g., erythromycin or meiroclopramide, to promote gastric emptying; 3) increasing the height of the head of the bed to use gravity to minimize upward displacement of refluxed gastric contents; e.g., 30-45 degrees; 4) switching the feeding tube from a gastric tube (nasogastric or orogastric) to the gastric pylorus, ideally distal to the ligament of Treitz; 5) manually aspirating gastric contents.

[0173] After one or more of these interventions, the clinician can determine whether they have achieved a reduction in the frequency of reflux and / or superior deviation of the enteral feeding tube and can also determine whether a bolus is present in the esophagus.

[0174] While there are many benefits to passive systems, in many clinical situations there are substantial incremental benefits from active systems. In addition to sharing the data collection capabilities of passive systems, active systems have at least one automatic intervention. This automatic intervention has the advantage of being performed immediately if certain criteria are met. In an exemplary embodiment, impedance data is captured and then analyzed by an algorithm to determine if certain criteria are met. In one exemplary embodiment, the criteria is reflux detected in the highest impedance channel, indicating a high probability of a potential aspiration event. In another exemplary embodiment, the criteria is the occurrence of reflux events in lower channels over a certain period of time, potentially indicating a higher likelihood of a potential aspiration event. Many exemplary data and criteria can be used to initiate a proactive intervention process.

[0175] In one exemplary active system, once the criteria are met, the computer 110 can automatically aspirate stomach contents and initiate a process (e.g., control an appropriate pump) to assist in preventing stomach contents from being aspiration. In another exemplary active system, once the criteria are met, the feeding pump can be automatically turned off by the computer so that no additional nutrients are introduced into the stomach, reducing the potential aspiration of stomach contents. In another exemplary active system, the computer can automatically create an obstruction in the esophagus to assist in preventing stomach contents from being aspiration.

[0176] A. Preventing aspiration by suctioning gastric contents Applying suction to the feeding tube removes stomach contents and reduces material present in the stomach and esophagus that can potentially be inhaled into the lungs, thus preventing or minimizing subsequent aspiration. The general concept is a device and system as shown in FIG. 11 that monitors reflux. When a certain frequency or upward deviation of reflux is measured, or when a certain level of bolus is present in the esophagus, suction is applied transiently (e.g., for 3 minutes) to the feeding tube to remove most or all of the stomach contents. In an exemplary embodiment, it may be desirable to set thresholds to initiate automatic suction if any of the following conditions are met: 1) any reflux event of at least 10 cm in excursion / height, 2) the presence of at least 5 reflux episodes less than 10 cm in height over a 6-hour period, 3) the continuous presence (for at least 15 minutes) of conductive material (possibly liquid) over the sensor closest to the head, 4) rapid detection of impedance drop in multiple channels.

[0177] In an exemplary embodiment, the auto-suction product, as shown in FIG. 16, consists of a feeding tube for reflux detection, connectors for attaching enteral feeding tubes and suction tubes, a monitor with auto-suction or control capabilities, and includes a software component with customizable options to manage the process.

[0178] In one exemplary embodiment, the feeding tube / impedance catheter has a dedicated suction lumen. In devices that include a dedicated suction lumen, one lumen can be accessed for the delivery of enteral nutritional fluids and medications, while the other lumen is connected to the suction device of the monitor.

[0179] In an exemplary embodiment, a shared lumen exists so that space within the tube is not wasted with a lumen for suction that is never needed. In a feeding tube with a shared lumen, an exemplary connector is attached to the proximal side of the feeding tube and has two connections or ports as shown in FIG. 14. One port is connected to an enteral feeding tube where a bolus dose can be administered or via an infusion pump. The other port is connected to a tube that is connected to a device that provides suction provided by a monitor with built in suction power or is provided by standard hospital wall suction where the monitor has control of the suction.

[0180] Automation of the feeding infusion pump can be envisaged to reduce or temporarily stop the infusion of tube feeding during suction, but this is not necessary as the temporary vacuum is more than sufficient to reduce the gastric contents. The infusion rate of food is generally 1.5 ml / min or less. Thus, even without stopping feeding, the addition of gastric contents achieved in a short time is minimal. In addition, it may be beneficial not to stop tube feeding for patients at high risk of hypoglycemia, for example, insulin patients who may become hypoglycemic if feeding is completely stopped.

[0181] The monitor's automatic suction system has several embodiments. In one embodiment, the monitor includes its own vacuum source, for example, internal to the monitor. This must be capable of generating a negative pressure of 50-150 mmHg. In this embodiment, a plastic tube is connected from the "patient side" connector on the monitor to the suction port of the feeding tube connector. For ease of use, this tubing can be connected to an electronic connection device for the feeding tube, and the tubing is used for infusion of the nutritional solution, and thus a single device contains up to three functional groups: wiring, supply tubing, and suction tubing. If the monitor selects a particular trigger criterion, the vacuum system will turn on for a transitional period, for example, three minutes, to remove all or most of the stomach contents. An alarm can be issued to notify the clinician that such an intervention has occurred. If additional trigger criteria are detected, the system will automatically reset so that suction is added, and upon detection of the additional trigger criteria, additional suction will be applied. A lockout can be set, if necessary, such that the device must wait at least 15 minutes between suction events to minimize potential damage to the stomach mucosa (lining).

[0182] In a preferred embodiment, the system is powered by externally provided suction, for example, the hospital wall suction, as shown in Figure 11. In this embodiment, the monitor controls a two-way normally closed solenoid valve. In this embodiment, plastic tubing connects from the hospital's stationary wall suction regulator (which reduces maximum pressure to approximately 150 mmHg and allows manual adjustment of the suction pressure), passes through the monitor, and then connects to the suction port of the feeding tube connector, as shown in Figure 14. For ease of use, this tubing can be connected to the tube electronics connection device and the tubing used for feeding infusion, so that a single device contains up to three functional groups: wiring, supply tubing, and suction tubing.

[0183] If the monitor detects a particular trigger criterion, the solenoid valve is energized for a transient time (e.g., 3 minutes) which results in an opening to allow an external vacuum source to be connected to the tubing connected to the patient's feeding tube to remove all or most of the gastric contents. An alarm can be generated to notify the clinician that such an intervention has taken place. If additional trigger criteria are detected, the system can be automatically reset so that additional suction is performed by reactivating the solenoid valve. A lockout can be set, if necessary, so that the device must wait at least 15 minutes between suction events.

[0184] Whether suction is performed internally or externally, a disposable suction trap is required for routine use during a suction event. For example, a disposable suction trap can be placed between the feeding tube connector 112 and the monitor 110.

[0185] The valve mechanism can be located in multiple locations. For example, the valve that opens and closes the suction can be located on the actual monitor. Another embodiment is to place the valve on the head of the feeding tube. This allows the enteral feeding pump tube and suction infusion to be attached directly to the feeding tube. In one exemplary embodiment, the valve can be connected via a wire that flows back to the monitor and is controlled via the monitor. In another exemplary embodiment, the control of the valve can be built directly into the valve assembly. In this embodiment, there may not be a physically separate monitor. The monitor functionality is essentially integrated into the connector component. This includes functions such as monitoring impedance measurements, valve control for suction, alarm initiation, and settings management.

[0186] There are many criteria for triggering aspiration. In one exemplary embodiment, a higher frequency of reflux events will trigger aspiration regardless of the height of this reflux event. For example, one event of 5 cm height may not initiate aspiration, but five of these events over a 30 minute period may trigger aspiration. In another exemplary embodiment, an upper excursion of reflux reaching, for example, 10 or 15 cm will trigger aspiration even if there is only one such event. Alternatively, a single event of reflux rising above the carina may trigger aspiration. The rate at which reflux is detected in each channel may also trigger aspiration. For example, a high rate of reflux, such as one channel per second (2 cm / s) starting with the distal channel, may initiate aspiration upon detection of reflux in each successive channel. This high rate of detected reflux means that aspiration may occur soon and therefore the patient is at high risk. The size of the reflux, or bolus, may also trigger aspiration. For example, a bolus spanning two channels, thus 4 cm, may trigger aspiration if measured in the more proximal channel closer to the tracheal opening 107. This may also be customized based on patient factors. For example, in another exemplary embodiment, in a patient three days post-operatively from a lung transplant, if any reflux is detected, e.g., only one event of 5 cm height, it may be desirable to suction the feeding tube. In another exemplary embodiment, the monitor can calculate a risk factor based on multiple inputs, such as the number of refluxes in a period of time, the severity of those refluxes, the percentage of reflux retrograde, the number of swallows in the period of time, and the number of burps in the period of time. For example, each reflux may be assigned a numerical severity based on its extent, the speed of retrograde motion, and the volume of reflux. A risk factor can be calculated from these severity using a sliding weight function. This weight function can place the greatest weight on the severity of the most recent reflux with a decreasing weight depending on the severity of reflux that occurred earlier. The risk factor can be calculated as the sum of the weighted severity of each reflux. If the risk factor is above a certain threshold, suction can be initiated.The weighting and severity functions may be designed to generate a risk factor that exceeds a default threshold for rapid and extensive regurgitation occurring in real time. Other events such as swallowing and aspiration may be assigned a negative severity, resulting in a decreased risk factor. The clinician may display this risk factor on the monitor. Examples of displayed risk factors include, but are not limited to, colored indicators, risk factors plotted over time, and bar graphs.

[0187] Suction is typically applied routinely to the gastric tube as either continuous low suction (e.g., 30-50 mmHg) or intermittent high suction (e.g., 150 mmHg). It is generally desired to minimize continuous suction with high suction to avoid damage to the gastric mucosa (i.e., stomach lining). Thus, the default setting may require 3 minutes of suction, but this can be modified based on the clinician's wishes. Additionally, the suction duration can be expanded based on the recorded data. For example, if reflux is still very active after 3 minutes of suction, the monitor can (in addition to warning and alerting the caregiver) apply constant suction (up to 30 minutes) until reflux ceases. Additionally, it is also possible for the monitor to vary the suction power. For example, for a monitor with an internal vacuum source, the system can be customized to apply low vacuum pressure (e.g., 50 mmHg) for 3 minutes in the case of less worrisome reflux (e.g., 3 events in 1 hour x 5 cm height), but for extremely worrisome reflux (e.g., 2 events x 15 cm height), full strength suction (e.g., 150 mmHg) is applied. Similarly, if the monitor is controlling suction, an exemplary valve can be opened partway to initiate low vacuum pressure (e.g., 50 mmHg), but must be fully opened to initiate full vacuum pressure (e.g., 150 mmHg). In other exemplary embodiments, there can be variations of this change from low vacuum pressure to full strength vacuum pressure. For example, for the first minute, the monitor can initiate full strength vacuum pressure, but then ramp down to low vacuum pressure for the remaining 2 minutes. In another exemplary embodiment, the monitor can initiate full strength vacuum pressure until the level of reflux has decreased to a sufficient point.

[0188] To help clinicians understand the inhalation event, there may also be an option to tell the clinician how many inhalation interventions were induced over a period of time, e.g., 6 or 24 hours. This report includes detailed information about measurements before, during and after the inhalation event.

[0189] In a setting where reflux of gastric contents can be monitored and passive or active interventions can be triggered, there is no need for routine manual measurement of gastric residual volume (GRV). This could reduce the workload of nurses, as measuring GRV is a time-consuming task. Currently, there is no way to detect if a patient is presenting with reflux, so attempts are being made to identify patients at high risk for reflux and aspiration.

[0190] In an exemplary embodiment, the algorithm can be adjusted to reflect how the head of bed angle affects the measurement of reflux and the potential risk of aspiration. Lower head angles are common in acute patients. Guidelines recommend that acute patients have a head of bed angle of 30° or greater. Often these patients slide down in bed with an effective angle of less than 30°. Because many patients are not monitored as closely, their effective angle is often less than 30°. The particular sensor location of any measured reflux and the time the patient has been refluxing can affect when to initiate suction. In an exemplary embodiment, because patients often have a lower effective head of bed angle and can more easily regurgitate and aspirate stomach contents, the lower proximal location of reflux and the shorter reflux time are utilized to initiate automatic suction. For example, reflux is measured at a sensor location of 5 cm. A location approximately 5 cm above the LES can be specified to initiate suction. In another example, reflux measured for 5 minutes at 5 cm above the LES can be identified to initiate suction.

[0191] The ability to detect reflux and aspirated gastric contents may even allow for a lower bed head than is now routinely prescribed for the lack of these useful tools. This lower bed head may provide many benefits. In some patients with head trauma, it is beneficial to have a lower head angle to aid in the patient's recovery. It may also be feasible that a lower head angle may help prevent subglottic secretions containing oropharyngeal bacteria from colonizing the trachea 107 and increasing the risk of aspiration pneumonia. In each case, the product's aspiration capability may reduce the patient's risk of aspirating gastric contents and potentially developing aspiration pneumonia.

[0192] Acute care patients with feeding tubes may be susceptible to reflux because the feeding tube passes through the LES, sometimes compromising the effectiveness of the LES in preventing stomach contents from entering the esophagus. Thus, reflux may be detected more frequently in distal channels, such as 5 cm above the LES. In an exemplary embodiment, suction may be initiated only if reflux reaches the higher proximal channels, since reflux may be more prevalent in the lower distal channels.

[0193] B. Preventing aspiration by adjusting the enteral feeding pump The data provided by the impedance sensor can be used to adjust the supply level. For example, if a patient is experiencing reflux above a predetermined level, the enteral feeding pump may be instructed to reduce the supply level, for example, from 80 ml / hr to 40 ml / hr. This reduction in supply may allow the patient to digest more nutrition and prevent more severe episodes of reflux that would increase the risk of aspiration. In this example, a smart feeding tube is connected to the enteral feeding pump, allowing a direct connection to acquire and process impedance data and subsequently modify the delivery of nutrition. Alarms can also be added to the device to contact the clinician in the event of any reflux events and reduced supply levels.

[0194] Many clinicians initiate feedings at a very low rate due to fears of reflux and aspiration of gastric contents. A system such as the one described above allows the clinician to more reliably initiate feedings at a higher rate, knowing that if any clinically significant reflux is detected, the feeding rate can be automatically reduced and / or the gastric contents will be automatically removed by suction. This allows the acute care patient to receive more nutrition and recover more quickly and effectively, while at the same time protecting against potential aspiration of gastric contents.

[0195] C. Prevention of aspiration due to esophageal obstruction Another exemplary embodiment prevents aspiration by automatically initiating an occlusion in the esophagus in response to impedance sensor data that can prevent stomach contents from traveling up the esophagus to the tracheal opening 107. A balloon device is placed between the LES and the trachea 107 and automatically inflates based on the sensor data. If the sensors 1101-1108 indicate that the patient is at high enough risk of aspiration, the monitor can control a pump to pump air into the balloon, inflating it. The inflated balloon creates a barrier in the esophagus 101, preventing reflux from reaching the trachea 107 and potentially into the lungs. This same approach can also be used to prevent vomiting upon detection of a risk of vomiting by the monitor. The balloon mechanism must inflate quickly enough to block reflux. An algorithm for determining when to inflate can accommodate the rate of inflation. The balloon material and level of inflation are designed to accomplish the purpose without injuring the esophagus 101. After inflation, the balloon can ideally be used again. The monitor can display information about the balloon during deployment. When such a severe reflux or emesis event occurs, an alarm can be activated to alert the clinician, who can then potentially direct his or her attention to the patient. Once the balloon is inflated, gastric contents can be automatically removed by suction, as described elsewhere herein.

[0196] It should be emphasized that the embodiments disclosed herein are not mutually exclusive and may be used with each other in whole or in part, and it is not practical to provide a separate description for each feature of the possible combinations of the embodiments described herein, and therefore, certain combinations of features according to the present invention may be described in connection with separate embodiments in this disclosure. Some embodiments utilize sensors to assist the clinician in correctly placing the feeding tube in the patient. Such embodiments may reduce the time and expense of confirming the placement (e.g., via x-ray). These embodiments allow the clinician to insert the feeding tube and provide timely feedback to indicate whether the insertion is correctly placed or if the feeding tube is not in the correct position, such as in the lumen of the trachea or the bronchus. Some embodiments provide feedback indicating that enteral feeding is being tolerated or, if appropriate, alerting the clinician that enteral feeding is not being tolerated. Gastric residual volume may be measured automatically via sensors, which may reduce the burden on the clinician associated with manual or other labor-intensive measurements. Some embodiments assess gastric motility, which is a clinical readout that helps the clinician determine whether the patient can tolerate enteral feeding. According to other embodiments, reflux in the esophagus can be monitored to provide both a warning to the clinician and an automatic suction capability to remove stomach contents and the risk of aspiration. While exemplary embodiments have been specifically shown and described, it will be understood by those skilled in the art that changes may be made in form and detail without departing from the spirit and scope of the appended claims.

[0197] VI. Impedance-based local GRV assessment In an exemplary embodiment, the GRV is measured using a sensor placed at the distal end of the feeding tube. The GRV sensor may be comprised of two or more electrodes. When these electrodes are placed in the patient's stomach, they measure the impedance of nearby tissues and fluids. This impedance measurement depends on the conductivity and distribution of the tissues and fluids surrounding the electrodes. Gastric chyme typically has a high conductivity relative to the stomach or other surrounding tissues, so the impedance measured by these electrodes will drop when the stomach volume increases due to an increase in the amount of gastric chyme. This decrease in impedance may occur due to the creation of a larger path width between the electrodes created by the gastric chyme. If the GRV sensor is comprised of just two electrodes, this is called a bipolar impedance sensor / measurement. With two electrodes, the impedance can be measured by injecting a current between the two electrodes and measuring the resulting voltage on the same two electrodes simultaneously. These two electrodes act as both the current source and voltage sensing electrodes simultaneously. If the GRV sensor is comprised of three electrodes, this is called a tripolar impedance sensor / measurement. With three electrodes, impedance can be measured by injecting a current between the common and source electrodes. A voltage is measured between the sense and common electrodes. The common electrode functions as both a source and sense electrode simultaneously. If the GRV sensor is configured with four electrodes, this is called a tetrapolar impedance sensor / measurement. With four electrodes, impedance can be measured by injecting a current between two source electrodes and a voltage can be measured between two sense electrodes. In some embodiments, impedance can also be measured by applying a voltage to the source electrode and measuring the resulting current on the sense electrode in bipolar, tripolar and tetrapolar impedance measurement configurations. Two or more electrodes can be grouped together to form a single electrode. For example, two or more electrodes on a conductivity sensor can function as a single electrode for the GRV sensor by electrically connecting these electrodes, such as external to the patient, such as in a monitor.

[0198] In an exemplary embodiment, a conductivity sensor may be placed at the distal end of the feeding tube along with the GRV sensor. The conductivity sensor may be utilized to determine the conductivity (the inverse of resistivity) of the stomach contents. The conductivity sensor functions much like an impedance sensor, but is intended only for the intrinsic measurement of electrical conductivity of a relatively well-known volume of tissue or liquid. In contrast, the impedance measurement of the GRV sensor is a reading of the extrinsic properties of electrical conductivity of a volume of liquid and tissue whose conductivity and distribution are unknown. Like the GRV sensor, the conductivity sensor may be configured with two, three, or four electrodes. If the conductivity sensor is configured with just two electrodes, this is referred to as a bipolar conductivity sensor / measurement. With two electrodes, the conductivity can be measured by injecting a current between the two electrodes and measuring the resulting voltage at the two same electrodes at the same time. These two electrodes act as both the current source and voltage sensing electrodes. If the conductivity sensor is configured with three electrodes, this is referred to as a tripolar conductivity sensor / measurement. With three electrodes, the conductivity can be measured by injecting a current between the common and source electrodes. A voltage is measured between the sense and common electrodes. The common electrode functions simultaneously as both a source and a sense electrode. If the conductivity sensor is constructed of four electrodes, this is called a tetrapolar conductivity sensor / measurement. With four electrodes, the conductivity can be measured by injecting a current between the two source electrodes and a voltage can be measured between the two sense electrodes. In some embodiments, the conductivity can also be measured by applying a voltage to the source electrode and measuring the resulting current on the sense electrode in bipolar, tripolar, and tetrapolar conductivity measurement configurations.

[0199] FIG. 22A shows an exemplary embodiment of a tetrapolar conductivity sensor at the distal end of the feeding tube 102. It consists of source electrodes 2201 and 2202 and two sense electrodes 2203 and 2204. The electrodes 2201 and 2202 are in a bipolar conductivity measurement configuration that injects current and sense voltage simultaneously as shown in FIG. 22E. This conductivity measurement can be useful in estimating GRV because estimation of GRV using measurements of epigastric impedance (see FIG. 10) depends on the conductivity of the stomach contents and other structures (e.g., skin, muscle tissue, adipose tissue) and their volume in the epigastric region interrogated by the impedance measurement electrodes of the GRV sensor. The stomach contains relatively conductive material, and as GRV increases, the measured impedance decreases. An increase in the conductivity of the stomach contents also causes a decrease in the measured impedance. By measuring the conductivity, this confounding impedance variable can be factored out of the estimate of GRV. By extension, measurement of GRV via impedance depends on the difference in impedance of the stomach contents and these other structures. If the ionic strength of the enteral nutrition formula is too low, the impedance difference between the gastric contents and other structures in the upper abdominal region of interest is insufficient to provide a reliable signal for estimating GRV. In the laboratory, this problem can be easily solved by adding a large amount (e.g., 9 g / L, 154 mEq / L) of sodium chloride (NaCl, table salt) to the standard enteral nutrition formula, ensuring that the ionic strength of the enteral nutrition formula is sufficient to provide a good impedance signal for estimation of GRV. However, in clinical practice, many patients have high levels of sodium ions (Na + ) or chloride ion (Cl - It is not recommended to add large amounts of sodium chloride to enteral formulas administered to patients because patients cannot tolerate large amounts of sodium chloride. Some commercially available enteral formulas contain high concentrations of Na + and potassium ion (K + ) and therefore have sufficient ionic strength to allow reliable estimation of GRV using epigastric impedance methodology. One such formulation is Osmolite 1.2, which has a NaCl content of 58 mEq / L. +and K of 46 mEq / L. + Other commercially available enteral formulas contain relatively low concentrations of Na + and K + and therefore may not have sufficient ionic strength to allow reliable estimation of GRV using epigastric impedance methodology. One example of this type of enteral nutrition formula is Nutrihep, which has a Na of 7 mEq / L. + and K of 33 mEq / L. + The ionic strength (and therefore conductivity) of the stomach contents depends not only on the ionic composition of the enteral formula, but also on the ionic (H + , K + , Cl - ) secretion. It may therefore be desirable to continuously monitor the conductivity of the stomach contents to determine whether the stomach contents at any given time have a suitable composition for determining the GRV. Furthermore, because calibration of the epigastric impedance monitoring system (by injecting a known amount of enteral feeding formula into the stomach) is only performed intermittently, and the gastric secretion rate and composition of ions can change on a minute-by-minute basis, it is useful to continuously adjust the GRV calibration setting to take into account the measured gastric content conductivity (changes relative to the value measured at the time of calibration).

[0200] In an exemplary embodiment, the impedance calculation is based on the following exemplary number 5 by Jaakko Malmivuo & Robert Plonsey, “BI / Oelectromagnelism - Principles and Applications of BI / Oelectric and BI / Omagnetic Fields”. Oxford University Press. New York. 1995, 25.3.3 (hereinafter “Malmivuo”), which is incorporated herein by reference in its entirety:

[0201]

number

[0202] In the above exemplary equations, there is an assumption that the stomach and tissue outside the stomach are essentially parallel resistors. In the exemplary embodiment, there is an assumption that the impedance of the surrounding tissue (Zi) is constant.

[0203] In this exemplary embodiment, the gastric impedance (Z J ) perpendicular to the current flow as a function of its conductivity (σ), length (l) and cross-sectional area (A). In this exemplary embodiment, a representative equation for the stomach impedance Z may be:

[0204]

number

[0205] Combining these equations results in the following exemplary equation for measuring impedance:

[0206]

number

[0207] In this exemplary formula, the measured impedance varies with the area, length, and conductivity of the stomach. In this exemplary embodiment, there is an assumption that the tissue impedance is constant and the length is known. Taking into account the change in measured impedance due to the change in conductivity, it is possible to use this model to calculate the change in stomach area.

[0208] FIG. 22A shows an exemplary embodiment of a GRV sensor consisting of two electrodes 2208 and 2209 in a bipolar impedance measurement configuration. The electrodes of the conductivity sensor may also be coupled together to form a single electrode for the GRV sensor. In this case, FIG. 22A shows a GRV sensor consisting of three electrodes 2201-2204, 2208, 2209 in a tripolar impedance measurement configuration. FIG. 22B shows an exemplary embodiment of a GRV sensor consisting of two electrodes in a bipolar impedance measurement configuration. The electrodes of the conductivity sensor are coupled together to form a single electrode for the GRV sensor. FIG. 22C shows an exemplary embodiment of a GRV sensor consisting of two source electrodes 2202 and 2205 and two sense electrodes 2206 and 2201 in a tripolar impedance measurement configuration. FIG. 22D shows an exemplary embodiment of a quadripolar impedance measurement configuration. The four electrodes of the conductivity sensor, 2201-2204, are connected together to form one source electrode for the GRV sensor. The other source electrode is 2205. The sense electrodes in FIG. 22D are 2206 and 2207. FIG. 22E shows an embodiment of a GRV sensor consisting of four electrodes in a tetrapolar impedance measurement configuration. The conductivity sensor in this embodiment consists of only two electrodes 2201 and 2202 to simultaneously inject current and sense voltage forming a bipolar conductivity measurement configuration. To measure the GRV, the source electrodes are 2205 and 2202 and the sense electrodes are 2206 and 2201. These embodiments are merely examples and do not limit the scope of the invention. Many other embodiments of the electrodes forming the GRV sensor and the conductivity sensor are possible in bipolar, tripolar or tetrapolar modes, with or without a common electrode.

[0209] An exemplary process for utilizing the apparatus described in FIG. 22 is described in FIG. 23. In the first step of this exemplary process 2301, the clinician connects the feeding tube 102 to the monitor 110. In step 2302, the clinician inserts the feeding tube. In step 2303, the clinician positions the feeding tube so that the GRV sensor is located in the patient's stomach. In step 2304, the monitor tests to ensure that the electrodes of the GRV and conductivity sensor are in good contact with the patient, either by touching tissue, being immersed in a conductive fluid such as gastric chyme, or a combination of both. In step 2305, the monitor begins a GRV measurement to establish a baseline measurement. In step 2306, this baseline measurement can be compared to a model to estimate the patient's GRV. The model can accept patient information such as gender, age, weight, height, etc. to help make the impedance measurement from the GRV sensor more accurate. In step 2307, the monitor takes a conductivity measurement with the conductivity sensor at the distal end of the feeding tube. Since the distal end of the feeding tube should be immersed in gastric chyme, the conductivity measurement should reflect the inherent electrical conductivity of the chyme. In step 2308, the clinician measures the GRV by suction and inputs it into the monitor. The clinician may have measured the GRV by suction prior to inserting the instrumented feeding tube. In this case, the clinician may input the time and date when the aspirated GRV measurement was taken. Alternatively, the monitor may obtain this data through a data exchange with the electronic medical record. The monitor estimates the GRV from the model data, the conductivity measurement, and the previous GRV measurement (the aspirated GRV measurement or a previous measurement by the monitor). Finally, in step 2310, the monitor displays the raw GRV measurement to the clinician. In addition to the live GRV estimate, the monitor may also display the monitor's confidence in the live GRV measurement and a trend of previous GRV measurements.

[0210] In an exemplary embodiment, conductivity can be a useful indicator for estimating GRV. In this embodiment, the remaining volume of stomach contents is determined by measuring the conductivity of the stomach contents before and after the injection of a control bolus. In this embodiment, a conductivity sensor is placed at the distal end of the feeding tube. Such a conductivity sensor can consist of two or more electrodes that can be connected to a monitor via wires. The monitor 110 can perform continuous conductivity measurements of the stomach contents. In this embodiment, a combination of sensors, such as the sensors disclosed herein and other sensors, can be used, and such combinations should be considered within the scope of the various embodiments described herein. The monitor can then control a known amount of fluid that is introduced into the stomach through the feeding tube, which in an exemplary embodiment can be 50 mL of distilled water. Since acute patients need fluids and water is a safe substance, it can be advantageous to use water as a control. The conductivity sensor can then continuously measure the change in conductivity of the stomach contents after the introduction of this control bolus of distilled water.

[0211] VII. Tube Localization via Impedance Measurement An exemplary embodiment for determining the position of the feeding tube is to measure the impedance between one or more impedance sensors on the feeding tube and a reference sensor. The impedance sensors on the feeding tube 102 may be electrodes. The reference sensor may be an electrode patch adhered to the patient's skin approximately four finger widths (approximately 4-5 cm) to the left of the navel. In this exemplary embodiment, there are two or more source patches attached to the patient's skin that are driven by an alternating current. For example, one source patch may be placed on the right side of the patient's neck and another source patch may be placed 1 cm to the left of the reference sensor. These source patches may be electrodes attached to the patient's skin. The impedance sensors on the feeding tube, the reference sensor, and the source patches are connected to a monitor. As the feeding tube is inserted into the patient's esophagus, the distance between the impedance sensor on the feeding tube and the reference sensor decreases and the measured impedance also decreases. The impedance between each impedance sensor on the feeding tube and the reference sensor is measured in ohms by the monitor. Each of these measured impedances may be referred to as a position channel.

[0212] The distance between all impedance sensors on the feeding tube is known. The difference between each of these location channels can be related to the known distance between the impedance sensors. For example, a calibration factor can be calculated for each location in the body and / or between each pair of two different impedance sensors by dividing the measured difference between the two location channels in ohms by the distance in centimeters between the impedance sensors associated with the two location channels. The calibration factor can vary due to the surrounding anatomical structures. When two impedance sensors enter an area with relatively low resistivity, they will have a low difference in their location channel. Similarly, when two impedance sensors are in an area with relatively high resistivity, their impedances will have a greater difference in their location channel. As an example, there may be a high resistance gas in the patient's stomach. When the two electrodes enter this gas, the calibration factor between these two electrodes increases.

[0213] The impedance between the impedance sensor on the feeding tube and the reference sensor may change due to breathing, the patient's heart, beating, or other physiological processes. In this exemplary embodiment, the location channel is filtered to include only frequencies lower than the patient's heart and breathing rates. The amount that the breathing and / or cardiac rhythm affects the location channel can also be used to indicate location. Although the impedance sensor on the feeding tube is close to the heart and / or lungs, the amplitude of the change in the location channel resulting from the heart and / or lungs is high. Close to the diaphragm or in the stomach, the change in the location channel due to the heart and / or lungs is lower. When the clinician inserts the tube through the nose and into the esophagus and / or stomach, the amplitude of the cardiac and / or respiratory artifacts will be seen to rise and / or fall. If these characteristic patterns are not seen, this may indicate that the feeding tube is not in the esophagus but in the lower airway.

[0214] The location of the impedance sensor within the patient's body can be consistently monitored by the monitor 110. This location information can be used to detect if the feeding tube has moved through time. The feeding tube may move into the esophagus, move too low in the stomach, or move past the pyloric sphincter. An alarm can sound to detect if the feeding tube has moved outside of a pre-set range. This will indicate to the clinician that the position of the feeding tube may need to be adjusted to return it to the proper position.

[0215] An exemplary process for using the described device is shown in FIG. 24. In step 2401, patient data including name, ID number, sex, height, and weight can be entered into the monitor manually or by electronic data interchange. In step 2402, a target distance for tube insertion can be calculated. For example, a nomogram proposed by Cirgin Ellett can be used to calculate the target distance from the entered patient data. In step 2403, a source patch and / or reference sensor is attached to the patient's skin. In step 2404, the feeding tube 102 is partially inserted into the patient. In step 2405, the monitor analyzes the location channel from each impedance sensor on the feeding tube and calculates a calibration factor. This calibration factor is used to convert the location channel to units of distance such as centimeters. In step 2406, the monitor uses the conversion factor and / or respiratory artifact to determine its location relative to the lungs, heart, LES, stomach, etc. In step 2407, the monitor calculates the probability that the feeding tube is in the lower airway or stomach from the location channel data, the conversion factor, the respiratory artifact, and / or the cardiac artifact. In step 2408, the current status of the feeding tube is displayed to the clinician. Step 2409 is reached when the clinician has inserted the feeding tube a certain distance. This distance can be calculated from the patient data entered in step 2401 or based on a target distance already calculated from step 2402. Or it can be a fixed distance. In one exemplary process, this distance is 25 cm. In step 2409, the monitor presents a report including a summary or chart of the tube insertion progress. Information in the report can include a numerical readout of the position channel, calibration factor, respiratory artifact, and / or cardiac artifact, respectively. Each of these variables is plotted against time and displayed on the chart. Similarly, the monitor can calculate an estimated position from all these variables. The calibration factor, respiratory artifact, and / or cardiac artifact may be further plotted on the chart with respect to the estimated distance. Once the target insertion is reached, step 2410 is reached.Either automatically or at the clinician's command, the monitor submits an EMR. In step 2411, the feeding tube is in the stomach and at the target distance and the enteral feeding pump begins delivering nutrition.

[0216] VIII. Tube location by local conductivity measurements Conductivity measurements from the conductivity sensors 2201-2204 at the distal end of the feeding tube 102 in FIGS. 22A-22E may also be used to determine placement of the feeding tube. The conductivity sensor can identify the tissue it is in contact with because each tissue has a different conductivity. Conductivity at two or more frequencies may be measured to help further determine the identity of the tissue. The lower airway is filled with air, lined with mucus, and opened up by connective tissue, i.e., tracheal cartilage. Air and / or connective tissue are poor conductors of conductivity. Furthermore, because the lower airway is opened up by connective tissue, the conductivity sensor will be away from the tracheal or bronchial walls and will only be exposed to air. This effect can be accentuated by placing the conductivity sensor in the recess of the feeding tube. This ensures that the conductivity sensor will read the low conductivity of air when it is in the lower airway. The esophagus is a virtual space lined with smooth muscle. While the feeding tube is in the esophagus, the walls close around the tube and make electrical contact with the conductivity sensor. If the conductivity measurement is within the range of smooth muscle tissue, this indicates that the feeding tube is likely in the esophagus. While the feeding tube is in the stomach, the conductivity sensor measures a high conductivity of the gastric chyme. This high conductivity indicates that the conductivity sensor is positioned in the stomach. The pattern of conductivity over time can also indicate tissue touching the conductivity meter. If the feeding tube was in the lower airway, it may move in and out, making electrical contact with the tube wall. This may create a characteristic conductivity pattern that indicates it is in the lungs. Similarly, in the esophagus, muscles may stretch and contract. This changes the conductivity of the muscle, changing the pressure on the conductivity sensor. This may create a conductivity pattern in time that indicates it is in the esophagus.

[0217] An exemplary process of using a conductivity sensor to aid in tube placement is shown in FIG. 25. In step 2501, a clinician inserts a feeding tube equipped with a conductivity sensor into a patient. In step 2502, the monitor 110 measures the conductivity at one or more frequencies. In step 2503, the monitor analyzes the conductivity and / or pattern of conductivity changes. In step 2504, the monitor correlates these conductivity values ​​and / or patterns to the expected conductivity and / or conductivity patterns of various tissues that the feeding tube may contact during correct or incorrect use. In step 2505, the monitor calculates the probability that the conductivity sensor is in contact with a particular tissue. Finally, in step 2506, the monitor displays the conductivity information and / or the detected tissue to the clinician. If the monitor detects that the conductivity sensor is in the lower airway with a probability above a certain threshold, it alerts the physician to remove and reinsert the feeding tube.

[0218] 26 shows an embodiment of a GRV measuring device in a human stomach. The GRV measuring device 2608 in this embodiment is a catheter or tube that includes at least one lumen. The GRV measuring device also includes a sensor or sensors 2610 in this embodiment at or near the distal end of the GRV measuring device. The lumen can be used to feed the patient and / or introduce a GRV indicator into the stomach 2602. The stomach contents 2604 include gastric secretions, nutrients previously present in the stomach, nutrients added to the stomach via the GRV measuring device, etc., and any GRV indicators used to determine the GRV of the stomach.

[0219] GRV indicators may include a substance with a higher or lower temperature than the stomach contents, a substance with a higher or lower pH than the stomach contents, a substance with a higher or lower O2 concentration than the stomach contents, a substance with a higher or lower CO2 concentration than the stomach contents, a substance with a higher or lower ion (e.g., magnesium) concentration than the stomach contents, a substance with a higher or lower glucose concentration than the stomach contents, a substance with a higher or lower viscosity than the stomach contents. Additional GRV and / or stomach entry indicators include electrical properties (conductance, resistance, current generation based on acid levels, impedance, etc.) that increase or decrease depending on the ratio of gastric acid to tube feeding into the stomach. Other GRV indicators are possible, some are described in other embodiments herein.

[0220] The GRV indicator can be introduced into the stomach contents 2604 via the lumen of the GRV measuring device 2608. A sensor or sensors 2610 can then measure the change in a property of the stomach contents to determine the remaining volume of the stomach, i.e., the GRV.

[0221] For example, if a substance at a higher or lower temperature than the stomach contents is introduced into the stomach, the sensor(s) can measure the magnitude of change in the stomach contents and / or the rate of change of the temperature of the stomach contents to determine the GRV. Both the rate of initial change and the rate of change to the pre-introduction state can be measured, and the magnitude of change can also be measured. Generally, the change from maximum change to the pre-introduction level is the slowest change and easier to measure, but either change can be measured. After the GRV indicator is introduced and the maximum level of the GRV indicator is measured, the rate of change of the indicator or the slope of the temperature vs. time curve can be measured. A relatively steeper slope indicates a higher GRV. A relatively shallower slope indicates a lower GRV. The same can be done with concentration and other GRV indicator types. For example, if the GRV indicator is glucose, the sensor(s) measure the glucose concentration in the stomach contents and the change in concentration over time.

[0222] Alternatively, a bolus of a substance of constant temperature (or concentration etc. depending on the GRV indicator) can be introduced into the stomach and the temperature (or concentration etc.) of the gastric contents measured as soon as the contents have had an opportunity to mix. The relatively immediate magnitude of the change in temperature or concentration can also be an indication of the GRV of the stomach. The lower the GRV, the greater the effect that the introduction of the GRV indicator will have on the gastric contents. The higher the GRV, the smaller the effect and consequently the smaller the magnitude of the measured change in the GRV indicator.

[0223] Another embodiment of the GRV measuring device includes a temperature change mechanism as part of the device. In this embodiment, the temperature of the stomach contents can be altered by either a heating element or a cooling element. For example, the GRV measuring device 2608 can include a heating element (not shown) that heats the stomach contents. The change in temperature is measured over time and the rate and / or magnitude of the temperature change is measured, so that the heat and / or cold of the stomach contents can be used to determine the GRV of the stomach.

[0224] Another variation of this embodiment of the GRV measurement device measured pH instead of temperature: a substance of constant pH (higher or lower than the stomach contents) can be introduced into the stomach and the change in pH measured over time to determine the GRV of the stomach.

[0225] A controller (not shown) can be used as part of the GRV measurement device to record and / or interpret various levels of the GRV indicator measured by the intragastric sensor. The controller can also use the GRV information to control the amount / rate / frequency / content of delivery.

[0226] 27 shows a stomach in which a substance containing a concentration of a GRV indicator was introduced into the stomach contents and the concentration was measured over time. In this embodiment, the sensor(s) measure concentration instead of temperature. For example, the GRV indicator 2702 in this embodiment could be glucose or magnesium, or any other suitable substance whose concentration can be measured.

[0227] 28 shows a graph of the temperature of the stomach contents over time as sensed by the sensor and recorded and / or interpreted by the controller after a bolus of cooling liquid is introduced into the stomach. The magnitude of the temperature drop and the slope of the gradual temperature rise back to normal can be used together or separately to determine the GRV of the stomach.

[0228] 29 shows a similar graph for the introduction of a GRV indicator where the concentration or pH is measured. After the GRV indicator is introduced into the stomach, the concentration or pH rises and then gradually returns to normal over time. Again, the magnitude of the change in concentration or pH of the GRV indicator in the stomach and the slope of the return to normal can be used together or separately to determine the GRV of the stomach.

[0229] 30 shows a graph of the temperature of the stomach contents over time as sensed by a sensor and recorded and / or interpreted by a controller after multiple boluses of cold liquid are introduced into the stomach. Note that in this example, the magnitude and / or slope of the graph after each bolus may be utilized by the controller in addition to the overall magnitude and slope of the bolus. Multiple boluses may also be used in conjunction with other GRV indicators.

[0230] 31 shows an embodiment of a GRV measuring device in which the sensor 3102 is outside the stomach, and preferably outside the patient's body. This embodiment is limited to GRV indicators that can pass through tissue, such as temperature, radiation, sound waves, magnetic substances, etc.

[0231] FIG. 32 shows an embodiment of a GRV measuring device in which the sensor 3202 is positioned along the length of the catheter or tube. In this embodiment, the GRV indicator can measure at different locations in the stomach to provide more information about the GRV. For example, assuming the patient is upright and the stomach contents are at the fundus of the stomach, the reading of the GRV indicator at the more proximal end of the GRV measuring device will be much lower, or even almost zero, and the reading at the distal end of the device will change over time as the GRV indicator is introduced and diluted by the stomach contents. Depending on the different GRV indicator readings at different locations along the GRV measuring device, more information about the amount of contents in the stomach can be obtained. For example, the device can determine that the stomach is almost half full, etc.

[0232] Also, Figures 33 and 34 show embodiments of the GRV measuring device with the sensor(s) in different locations. Figure 33 shows a sensor 3302 on the outside of the tube / catheter. Note that in any of the embodiments herein, the sensor(s) may run radially around the tube / catheter or may be on one or more sides of the catheter / tube. This and other embodiments also allow a separate feeding tube to be inserted through the GRV measuring device (not shown). This may be desirable if a standard feeding tube is being used. It is also possible to insert the GRV measuring device into a patient's body with a feeding tube already in place. This is advantageous if it is not known at the time of placement of the feeding tube that a GRV measuring device will be used.

[0233] 34 shows a sensor 3402 embedded in the wall of the GRV measurement device. This embodiment offers the advantage of a smooth transition on both the outside and inside of the GRV measurement device. Note that the sensor in any of the embodiments may be at any location along the length of the GRV measurement device.

[0234] FIG. 35 shows an embodiment of a GRV measuring device separate from the feeding tube. In this embodiment, the feeding tube 3506 may be inserted into the patient separately from the GRV measuring device 3502. The GRV measuring device in this embodiment may or may not have a lumen. Since the patient is fed through a separate tube, the size of the GRV measuring device can be very small and can be inserted along the feeding tube. In fact, the GRV measuring device in this embodiment can be of similar dimensions (0.5 mm or less, or 1.0 mm or less, or 2.0 mm or less) as a guidewire with a sensor 3504 at its distal end or along its length. In this embodiment, the GRV indicator can be introduced through the separate feeding tube.

[0235] FIG. 36 shows a GRV measuring device similar to FIG. 35, but in this figure, the GRV measuring device is inserted through the feeding tube. This configuration has the advantage that it is easily inserted after the feeding tube is already in place. In this embodiment and any embodiment, the GRV measuring device can be introduced periodically before or after the GRV indicator is introduced into the stomach. In this way, the extra volume of the GRV measuring device does not significantly interfere with the feeding process through the feeding tube. Alternatively, the GRV measuring device may be small enough so as not to adversely affect the flow of nutrients or other substances through the feeding tube.

[0236] Figures 37 and 38 show how the sensor of the GRV measuring device can be placed in various locations relative to the feeding tube. This helps to obtain a cleaner measurement after the introduction of the GRV indicator. For example, if a heated substance is introduced through the feeding tube, it is advantageous to place the sensor of the GRV measuring device a certain distance away from the exit of the feeding tube, both to protect the sensor from extreme heat, but also to obtain a cleaner temperature reading. The further the sensor is from the source of introduction of the GRV indicator, the more mixing of stomach contents will occur.

[0237] Alternatively, a sensor can be placed in the feeding tube as the GRV indicator is introduced through it to obtain a baseline value of temperature / concentration / pH etc. of the GRV indicator. The sensor can then be moved into the stomach contents to obtain changing readings that are used to determine the GRV. Alternatively, the GRV measuring device can have sensors along its length that accomplish the same thing. There may be other advantages to moving the GRV measuring device during the measurement process. By measuring the GRV indicator at various locations in the stomach and / or stomach contents, more information about the stomach contents can be obtained.

[0238] FIG. 38 shows a sensor 3802 of a GRV measuring device at the pylorus 3804. In this embodiment, stomach volume is estimated by direct measurement of input (enteral nutritional material) and output (pyloric passage). The amount of material entering and passing through the pylorus can be measured by volumetric flowmeter, or Doppler ultrasound, or optical, or any other suitable technique. In one embodiment, after a magnetic material is introduced into the stomach, the movement of the material induces a current to flow through the pyloric passage, which can be measured within the pylorus or outside the patient's body.

[0239] It should be noted that in any of the embodiments herein, the GRV measurement device may be outside the feeding tube, inside the feeding tube, integrated into the tube, or completely separate from the feeding tube.

[0240] Other embodiments of the invention are shown in Figures 39-41. In these embodiments, the GRV measuring device is also used to place a device, or a feeding tube, inside the stomach to ensure proper feeding and GRV measurement. In these embodiments, a transmitter 3902 emits a signal 3904 that is detected by a position receiver 3906. The transmitter may be separate from the sensor, as shown in other embodiments, but both may be present in the GRV measuring device (note that no sensor is shown in Figures 39-41). The position receivers may be external to the body, as shown in Figures 39 and 40. Or they may be part of the GRV measuring device, as shown in Figure 41. The transmitted signal may be an audio signal, an ultrasound signal, a pressure signal, or any other suitable signal. Alternatively or in addition, any of the pH, temperature, or GRV indicator signals may be used. The position receiver receives the signal through the tissue, as shown in Figures 39 and 40, or after the reflected signal 4102 bounces off the stomach walls and possibly the stomach contents, as shown in Figure 41. The embodiment of the GRV measurement device of Figure 41 includes a transmitter and position receiver on a device within the stomach.

[0241] Also, Figures 39 and 40 show the transmitter in the empty portion of the stomach and in the stomach contents, respectively. The signals received when the transmitter is in these two different locations are very different and are useful for locating the tip of the feeding tube. The transmitter may be at the tip of the feeding tube and / or at other locations relative to the tip of the feeding tube.

[0242] 42 and 43 also show an embodiment of a GRV measuring device used percutaneously. For example, the GRV measuring device can be used as or with a Percutaneous Endoscopic Gastrostomy (PEG) tube. In this situation, a feeding tube passes through the patient's abdomen and directly into the stomach to feed the patient. Shown here is a PEG tube 4202 passing through the skin 4208, fat 4206 and muscle 4204 into the stomach wall with the tip of the PEC tube in the stomach. The GRV measuring device may be incorporated into the PEG tube or may be separate as shown here. A GRV measuring device 4212 is used here through the inside of the PEG tube. In this and other embodiments, the GRV measuring device is connected to a controller to record and interpret measurements detected by the sensors.

[0243] In this and other embodiments, the GRV measuring device may remain in the stomach during feeding and may be introduced periodically when measurements are needed. A restrictor 4210 may be used to control the flow of nutrients into the stomach. The restriction enzyme may be controlled by a controller in a feedback loop so that nutrients are only introduced when the GRV is below a certain level. Nutrients may also be automatically restricted when the GRV is above a certain level. These levels may be preset, set by the controller, or adjusted as needed. This type of feedback control also allows for bolus delivery versus a continuous delivery which is more physiologically representative.

[0244] Figure 43 is similar to Figure 42, except that the entry point for the GRV measurement device is between the patient and the resistor. This allows for easier use of the resistor when the GRV measurement device is in place.

[0245] It should be noted that the embodiments of Figures 42 and 43 can be used with standard PEG tubes, or the GRV measuring device can be incorporated into the PEG tube.

[0246] 44 shows an embodiment of the GRV measurement device for use with a jejunostomy tube. In this embodiment, the feeding tube enters the intestine instead of the stomach. As with other embodiments herein, the GRV measurement device can be used with a standard jejunostomy tube or can be incorporated into the jejunostomy tube.

[0247] 45-49 show detailed embodiments of a GRV measuring device. FIG. 45 shows an embodiment of a GRV measuring device integrated into a feeding tube. The device shaft 4502 includes a sensor or sensors 4504, a measurement communication line 4506. The measurement communication line may be a metal wire or may be a feeding lumen 4508. The sensor 4504 measures the temperature, pH, concentration, etc. of the GRV indicator in the stomach after the indicator has been introduced through the device or produced by the device. For example, a fluid at or below body temperature can be introduced into the stomach via the lumen 4508. The magnitude of the temperature change in the stomach is measured by the sensor 4504, as is the rate of return to normal temperature. This information is transferred along the communication line 4506 and back along the shaft 4502 to the controller. The controller can control the feed supply by user input or automatically in response to the controller's stomach volume analysis.

[0248] It should be noted that the sensor 4504 can be placed anywhere along the length of the device. Also, note that the sensor may be placed inside (within the lumen 4508) or outside the device, or both. Having separate sensors on both the inside and outside of the device allows for measurement of the uningested GRV indicator entering the stomach (sensor inside) and the change in the GRV indicator over time (external sensor). These sensors may be the same sensor that measures both inside and outside the device. It should also be noted that there may be a barrier or insulator between the sensor and the inside of the device or the outside of the device. This allows the sensor to measure the GRV indicator either inside the device or outside the device without being contaminated.

[0249] Alternatively, the GRV measurement device may cool the stomach contents using a cooling element (not shown) and measure the magnitude and rate of the resulting temperature change to determine stomach volume.

[0250] In another example, the pH of the stomach contents can be measured to determine stomach volume. A substance of known pH (which may be the food substance itself) is introduced into the stomach and the sensor measures the change in pH and the rate of return to normal pH. That information is sent back to the controller, which can determine stomach volume.

[0251] In another embodiment, the GRV measuring device can use more than one GRV indicator. For example, both temperature and pH can be used. In this example, measurements of one GRV indicator can be used to confirm measurements of the other GRV indicator to obtain more accurate results. Additionally, measurements can be taken at different locations to ensure gastric content mixing and / or improve accuracy. Other GRV indicators can be combined in a similar manner.

[0252] FIG. 46 shows another embodiment of a GRV measuring device. This embodiment is designed to be used with, along, or through the lumen of a feeding tube. This embodiment is relatively small in diameter (0.5 mm or less, or 1.0 mm or less, or 2.0 mm or less) so as not to substantially impede the flow of nutrients to the patient through the feeding tube, or is not difficult to insert into the patient along the feeding tube. The shaft 4602 is preferably relatively rigid, similar to a guidewire, and incorporates signal communication from a sensor 4604. The shaft 4602 can be made of a metal, such as stainless steel or other suitable material. In this embodiment, the GRV indicator can be introduced through a separate feeding tube. Note that this and other embodiments can be placed in the stomach before or after the feeding tube is placed in the stomach.

[0253] Also, Figures 47-49 show another embodiment of a GRV measuring device that can be used with a feeding tube after the feeding tube has already been inserted. This embodiment is designed to go on the outside of the feeding tube and includes a relatively rigid shaft 4708, a sheath 4704, a sensor 4702, and a slit 4706. The shaft 4708 may be made of a similar material to the shaft 4602 of Figure 46. The sheath 4704 is thin enough that it can easily slide over the feeding tube, but stiff enough so that it does not collapse. A variety of polymers and other materials can be used. To introduce this embodiment, the sheath 4704 is placed on the outside of the proximal end of the feeding tube using the slit 4706 after the feeding tube is already in place. The GRV measuring device is then slid down the outside of the feeding tube into the patient's stomach using the relatively rigid shaft 4708.

[0254] FIG. 48 shows this embodiment of a GRV measurement device after the GRV measurement device has been placed over a feeding tube 4802.

[0255] FIG. 49 is a cross-sectional view of this embodiment of the GRV measurement device.

[0256] FIG. 50 shows an embodiment of a device based on physical characteristics where GRV and penetration into the stomach are monitored continuously or intermittently. In this embodiment, the GRV indicator can be inherent to the feed or meal itself without the need for additives. In this embodiment, the GRV indicator can be a physical property such as pH or electrical resistance, impedance or conductance. In this embodiment, the physical property can be monitored over time and changes that occur as the meal empties from the stomach are recorded. As the meal leaves the stomach and the relative concentration of gastric fluids increases, the physical property changes in a measurable way. In one embodiment, the physical property is pH, where the pH decreases as the meal leaves the stomach and gastric secretions represent more than those remaining in the stomach. When the pH reaches a low enough level, the device can alert the user that the meal has left the stomach and the patient is ready for another bolus. In another embodiment, the physical property is resistance or impedance. The meal delivered to the patient can be formulated to have a high resistance or impedance such that a subsequent decrease indicates an increase in the concentration of gastric secretions. Conductance can be the opposite but increases as the meal leaves the stomach.

[0257] In yet another embodiment, the sensor may be comprised of a circuit that is driven by acid. For example, two leads may be introduced into the stomach made of different metals (in a preferred embodiment, these are copper and magnesium). In the presence of acid, these metals act like the terminals of a battery and generate a current. This current may be recorded continuously or intermittently to report stomach emptying based on an increase in the concentration of acid. The same electrodes may also be used to sense electrical parameters of the stomach (impedance, conductance, resistance, etc.) to provide further information to increase the sensitivity and specificity of the measurement. Each of these measurements of physical properties of the stomach may be used alone or in combination to report that the sensor (and thus the tip of the tube or catheter) is in the stomach and not the lungs. Ideally, two or more parameters (current due to pH, acid, impedance / conductance, etc.) are measured to improve the accuracy of the measurement. This is important as the incidence of tube placement in the lungs is as high as 20% and initiation of tube feeding with the tip in the lungs can be fatal. In this embodiment, the sensor may be incorporated into the catheter / tube itself or may be a separate component that screws inside an existing feeding catheter / tube to provide a spot reading regarding the location of the tip of the tube. In this ideal embodiment, the sensor is integrated into the catheter / tube to provide a signal indicating when the catheter / tube is in the stomach (not the lungs) and then the GRV to aid in optimal feeding. In an ideal embodiment, feeding may similarly be via a closed loop system that automatically selects the GRV and delivers a tube feed when appropriate, based on each patient's programmed nutritional goals. In this embodiment, a target volume for tube feeding may be set for each time period and a maximum volume may be programmed.

[0258] FIG. 50 shows a patient with a GRV measuring device 5006 placed in the stomach 5002. Note the proximity of the lungs 5004 and why it is important to verify placement of the GRV measuring device in the stomach and not the lungs. The GRV is measured as described herein. A controller 5008 tracks the GRV intermittently or continuously via connector 5010 and uses this information to control the patient's feeding via a valve or restrictor 5014 using connector 5012. A source 5016 is connected to the feeding tube and the volume, volume, frequency and contents of the feeding are controlled by the controller 5008. The GRV indicator may be inherent to the feeding, added to the feeding or added separately from the feeding. The controller may collect measurements of the GRV indicator in the feeding tube just before the feed is released into the stomach and in the stomach contents over time. This would result in a GRV indicator being displayed on the controller just before the mixer is started, resulting in an accurate GRV.

[0259] FIG. 51 shows an embodiment of a GRV measuring device that uses gastric acid in the stomach to generate a type of battery that generates a measurable current that is measured and analyzed by a controller. The measured current is indicative of the GRV of the stomach. The GRV measuring device shaft 5102 includes wires 5108 and 5110 that connect to two different electrodes. The electrodes in this embodiment are made of dissimilar metals such as aluminum and copper, although other dissimilar metals may be used. In this embodiment, a current is generated by the fluid in the stomach that is measured and analyzed by the controller to determine the GRV.

[0260] In another embodiment, the impedance of the gastric fluid is measured instead of the current. The impedance indicates the ratio of gastric acid to feed and provides an estimate of the GRV. This embodiment would appear similar to the embodiment shown in FIG. 51, except that the electrodes are preferably the same metal rather than dissimilar metals. The controller generates a voltage and measures the resulting current to determine the impedance of the fluid in the stomach. In this embodiment, a voltage is generated by the controller, a current is passed through the gastric fluid, and the resistance is measured and analyzed by the controller to determine the GRV.

[0261] It uses the different electrical properties of stomach and gastric acid in the feed. GRV can be assessed by conductivity, current, impedance, capacitance, electrical resistance, etc. AC and / or DC signals can be used to make these measurements. Several possible embodiments are envisaged.

[0262] For example, in one embodiment, an additive liquid element (water, saline, etc.) is introduced by a source that is significantly lower or significantly greater than the nominal contents temperature. Temperature measurements can be recorded by sensors at one or more locations in the contents mixture. In one embodiment, the rate of change of temperature over a period of time is indicative of the stomach volume. In one embodiment, the temperature obtained from the mixture after a set time is indicative of the stomach volume. In one embodiment, a physical thermal element provides a sudden temperature change. This element can heat or cool the stomach contents upon quick contact with the element.

[0263] In one embodiment, an additive element is introduced that changes the viscosity of the contents. The resulting change in viscosity is indicative of the stomach volume. In one embodiment, an additive component, glucose, is introduced. The resulting change in the concentration of glucose is indicative of the stomach volume. In one embodiment, a coloring element, such as methylene blue, is introduced and the resulting concentration is used to indicate the stomach volume. In one embodiment, an additive component is introduced that changes the pH value of the stomach contents. The rate of change or the resulting pH value is indicative of the stomach volume. In one embodiment, an additive element is introduced that changes the electrical conductivity of the contents. In one embodiment, an additive element is introduced that changes the refractive index, opacity, absorptivity, luminosity or color of the contents. In one embodiment, an additive element is introduced that changes the specific gravity of the contents.

[0264] In one embodiment, an additive component that changes the content is introduced and measured by a method of titration. In one embodiment, the additive component solidifies the content. In one embodiment, the additive component changes the electrical conductivity of the content. In one embodiment, the additive component causes the content to change optical opacity or color.

[0265] In one embodiment, pressure is induced by introducing additional material into the intragastric space. This material may be air, saline, water, or other. In one embodiment, pressure may be induced by inflation of a balloon. In one embodiment, the pressure response is measured internally. In one embodiment, pressure is measured externally using a pressure gauge around the abdomen. This pressure difference before and after introduction indicates volume.

[0266] In one embodiment, an acoustic source is used to generate standing waves in the stomach space. The resulting pressure pattern is indicative of the dimensions of the medium, in this case the stomach contents. In one embodiment, the acoustic source is external and an acoustic or pressure sensor is used internally. In one embodiment, both the light source and the sensor are internal. In one embodiment, the source is internal and the pressure or acoustic properties can be measured externally. In one embodiment, both the light source and the sensor are external. The acoustic source can be a point source or an array of transducers that generate a range of frequencies and amplitudes. The acoustic or pressure sensor can be a single measurement point or an array of sensors.

[0267] In one embodiment, the flow rate of material is measured directly at the pylorus passage. Gastric volume is estimated by direct measurement of input (enteral nutritional material) and blood loss (pylorus passage). In one embodiment, the amount of material entering and passing through the pylorus is measured with a volumetric flow meter. In one embodiment, Doppler ultrasound is used to measure a measure of fluid movement. In one embodiment, after a magnetic material is introduced into the stomach, the movement of the material induces an electric current as it passes through the pylorus passage. In one embodiment, an optical system is used to measure the flow rate.

[0268] In one embodiment, the autonomous device navigates through the stomach to ensure that all of the stomach contents are aspirated.

[0269] Data Processing System Example FIG. 52 is a block diagram of a data processing system that may be used with any embodiment of the present invention. For example, system 5200 may be used as part of the controller / monitor disclosed herein. It is noted that while FIG. 52 illustrates various components of a computer system, it is not intended to represent a particular architecture or manner of interconnecting the components, and such details are not germane to the present invention. It will also be understood that network computers, handheld computers, mobile devices, tablets, mobile phones, and other data processing systems having fewer components or perhaps more components may also be used with the present invention.

[0270] As shown in Figure 52, computer system 52(H) is in the form of a data processing system and includes one or more microprocessors 5203 and a bus or interconnect 5202 coupled to ROM 527, volatile RAM 5205, and non-volatile memory 5206. The microprocessor 5203 is connected to a cache memory 5204. The bus 5202 interconnects these various components to each other and interconnects these components 5203, 5205, 5205, and 5206 to a display controller and display device 5208 and input / output (I / O) devices 5210, which may be a mouse, keyboard, modem, network interface, printer, and other devices known in the art.

[0271] Typically, input / output devices 5210 are connected to the system via an input / output controller 5209. Volatile RAM 5205 is typically implemented as dynamic RAM (DRAM), which requires continuous power to refresh or maintain the data in the memory. Non-volatile memory 5206 is typically a magnetic hard drive, a magnetic optical drive, an optical drive, or a DVDRAM, or other type of memory system that maintains data even after power is removed from the system. Non-volatile memory is usually also random access memory, although this is not required.

[0272] Note that while FIG. 52 shows the non-volatile memory to be a local device directly coupled to the remaining components in the data processing system, the present invention may utilize non-volatile memory remote from the system. A network storage device coupled to the data processing system via a network interface, such as a modem or Ethernet interface. Bus 5202 may include one or more buses connected to each other through various bridges, controllers, and / or adapters, as is known in the art. In one embodiment, I / O controller 5209 includes a USB (Universal Serial Bus) adapter for controlling USB peripherals. Alternatively, I / O controller 5209 may include an IEEE 1394 adapter (also known as a FireWire adapter) for controlling FireWire devices.

[0273] Some portions of the preceding detailed descriptions are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the method used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities.

[0274] It should be borne in mind, however, that all of these and similar terms are to be understood as relating to the appropriate physical quantities and are merely convenient labels applied to these quantities. As is apparent from the above discussion, unless otherwise noted, discussions utilizing such terms in the following claims refer to operations and processes of a computer system or similar electronic computing device that convert, manipulate and transform data represented as physical (electronic) quantities in the computer system's registers and memories to other data similarly represented as physical quantities in the computer system's memory or registers or other such information storage, transmission or display devices.

[0275] The techniques illustrated in the figures may be implemented using code and data stored and executed on one or more electronic devices that store and communicate code and data (internal to and / or with other electronic devices over a network) using non-transitory computer-readable storage media (e.g., magnetic disks; optical disks; random access memory; read-only memory; flash memory devices; phase change memory) and transitory computer-readable storage media (e.g., electrical, optical, acoustic or other forms of propagated signals, such as carrier waves, infrared signals, digital signals, etc.).

[0276] The processes or methods illustrated in the previous figures may be performed by processing logic that includes hardware (e.g., circuitry, dedicated logic, etc.). It may include firmware, software (e.g., embodied on a non-transitory computer-readable medium), or a combination of both. Although the processes or methods are described above in terms of some sequential operations, it should be understood that some of the described operations may be performed in a different order. Additionally, some operations may be performed in parallel rather than sequentially.

[0277] 53 and 54 show an embodiment of a GRV measurement device that ensures correct gastric tube placement and measures and reports gastric residual volume by measuring electrical conductivity in the respiratory and gastric systems. Placement in the respiratory system indicates improper placement and alerts the user to replace the device.

[0278] Various tissues and fluids have different conductivities based primarily on the concentration of ions. Acidic solutions, such as stomach acid, are highly ion-concentrated and therefore highly conductive. Common nutrients delivered via stomach tubes, such as milk and Ensure, are slightly acidic and therefore slightly conductive.

[0279] Conductivity can be measured by passing an alternating current (AC) through a material and measuring the voltage. Using Ohm's law, the conductivity can be calculated. The frequency of the AC current can be varied depending on the conductivity of the solution. Higher frequencies can be used for high conductivity measurements to minimize polarization effects (ions move towards the poles and block the measurement). Lower frequencies can be used for low conductivity measurements to minimize the effects of cable capacitance (power loss in the cable).

[0280] Conductivity can be measured using a conductivity meter such as the HM Digital AP-2 AquaPro Water Quality Conductivity Tester or the HM Digital ECG-3 Conductivity Tester.

[0281] FIG. 53 shows one embodiment of a GRV measurement device that measures conductance. The catheter 5302 also functions as a feeding tube and has an opening 5308 through which the feed and / or GRV indicator can flow. Only the distal end of the catheter / feeding tube is shown here. The distal electrode 5304 measures conductance. The proximal electrode 5312 also measures conductance. There may be one, two or more sets of conductance electrodes along the catheter. Electrical connections such as wires run from the electrodes through the length of the catheter to the proximal end (not shown) and finally to a conductivity meter. A pH sensor or sensor 5310 may also be present on the catheter to aid in catheter placement and GRV measurement.

[0282] FIG. 54 shows one embodiment of a GRV measurement device that measures conductance. A catheter wire / elongated member 5402 is designed for use through or with a feeding tube. Here, only the distal end of the member is shown. A distal electrode 5404 measures conductance. A proximal electrode 5412 also measures conductance. There may be one or more pairs of conductance electrodes along the member. Electrical connections such as wires run from the electrodes through the length of the member to the proximal end (not shown) and ultimately to a conductivity meter. A pH sensor or sensor 5410 may be present on the member to aid in positioning the member and feeding tube and measuring the GRV.

[0283] The pH sensor or electrode may consist of an internal reference and an external counter electrode. Conductance electrodes are preferably present in pairs, one being the output signal and the other being the input signal. There may be multiple pairs in a GRV measurement device. The two "pairs" of electrodes may consist of only three electrodes with one electrode acting on each pair, for example electrodes 1 and 2 may be used in the first pair and 2 and 3 in the second pair. Types of pH electrodes that may be used include antimony, glass, and / or ISFET (ion sensitive field effect transistor) pH electrodes.

[0284] The length of the GRV measurement device may be from about 25 inches to about 40 inches. The outer diameter of the GRV measurement device may range from about 0.02 inches to about 0.20 inches. The GRV measurement device may be made from any suitable material including polymers, silicones, etc. The GRV measurement device may be arranged in one, two or more lumens, concentrically arranged to accommodate the various lumens and electronics required. In some embodiments of the GRV measurement device, the electrode pairs are positioned 6 inches from each other, although the electrodes may be closer or farther apart from each other.

[0285] Table 1 below shows the results of measuring the conductance of water, simulated gastric acid, and Ensure Plus, a common feed. It can be seen that the conductivity of gastric acid is far higher than that of water, ensuring a positive result.

[0286] [Table 1]

[0287] FIG. 55 shows that conductivity increases with increasing percentage of gastric acid in various media.

[0288] Similar results have been found in the digestive and respiratory systems of pigs, see Table 2 below, demonstrating that conductivity can be used to determine placement of GRV measuring devices and / or feeding tubes.

[0289] [Table 2]

[0290] FIG. 56 shows pH and conductivity at various anatomical locations in a pig. This graph shows that using a combination of conductivity and pH improves the ability to identify the location of the sensor. For example, the pH of the esophagus and the pH of the lungs are similar here. However, the pH of the esophagus or lungs is significantly different than the pH of the stomach. The conductivity of the esophagus is different from the conductivity of the lungs. By using both the pH and conductivity measurements at any given location, and / or the changes in the pH and conductivity measurements at any given location, the location of the sensor on the GRV measurement device can be determined. This allows one to identify when the GRV measurement device happens to be in the esophagus, or in the stomach, and when it is in the lungs.

[0291] Figures 57 and 58 show the conductivity and conductivity oscillations at various locations in the human anatomy before and after eating.

[0292] Human subjects were initially in a fasting state. A GRV measuring device was inserted into the esophagus and then into the stomach. Subjects were given three bottles of almond milk over a two-hour period and conductivity measurements were taken throughout the experiment. The results are shown in Figure 57.

[0293] The conductivity of air is 0 μβ. When the GRM measuring device was inserted into the esophagus, the conductivity increased significantly. When the device entered the stomach, the conductivity increased further. Figure 57 shows that the conductivity decreased after each feeding and then increased again as the liquid was digested.

[0294] FIG. 58 shows a portion of the graph shown in FIG. 57 enlarged. Data was recorded at a sample rate of 1 Hz (1 reading / second). The increased resolution of this graph reveals 22 seconds of vibration that may be associated with peristalsis of the esophagus, stomach, and intestines. The amplitude of the vibration is plotted at the bottom of the graph in FIG. 57. As the stomach fills, the amplitude of the vibration decreases. As the meal is diluted with stomach acid and conductivity increases, the magnitude of the vibration increases. Then, as the meal is digested, the magnitude of the vibration decreases again. FIG. 57 illustrates this trend, as the range of oscillation increases before power is applied and decreases after power is applied. The position of the GRV measuring device and the GRV can be determined by measuring the conductivity and / or the magnitude of the conductive vibration.

[0295] Figures 59 and 60 show the pH and pH oscillations while the GRV measuring device is moved from the esophagus to the stomach of a fasting human.

[0296] The GRV measuring device is inserted through the esophagus into the stomach. The pH reading decreases upon entering the stomach.

[0297] Figure 60 shows an expanded portion of the graph shown in Figure 59. The pH measurements are shown to oscillate in a similar manner to the conductivity measurements.

[0298] FIG. 61 shows both conductivity and pH measurements from a GRV measurement device during feeding. The pH increases during feeding. The conductivity simultaneously decreases, reducing the variability between sensors. Not visible in this graph is digestion, which occurs as the stomach empties. The pH decreases and the conductivity increases. As the stomach becomes full due to its homogenous contents, there is less variability in the measurements. As food is digested, variability increases as peristalsis increases and as the sensor moves between liquid and air pocket regions.

[0299] By measuring both pH and conductivity, the various digestion steps can be detected using algorithms that take into account the average and variability of pH and conductivity.

[0300] For example, the percentage of food during feeding can be calculated by applying empirically measured functions of pH and conductivity vs. food % (food (food + gastric fluids)). For a known amount of a known type of food delivered at any given time, the pre- and post-meal content can be calculated as follows: Before volume * before food percent + before food volume = after volume * after food percent Immediately before and after eating, the following conditions must be met: After volume = before volume + feeding volume Therefore, the initial equation can be written as: Volume before*percent food before+volume fed=(volume before+volume fed)*percent food after And this equation can be written as an equation with all the information needed to calculate the amount before eating: Before Volume = Fed Volume * ((After Food Percent-1) / (Before Food Percent-After Food Percent)) Now that we know the total weight before and after feeding, and the amount of food before and after feeding, we can also calculate the amount of food before and after feeding: Previous food volume = Previous volume * Previous food percent Food volume after = volume after * percent food after

[0301] In an exemplary embodiment, measurement techniques using conductivity, as well as conductivity combined with pH, ​​can be combined with an embodiment that measures impedance of local tissues and fluids. In this exemplary embodiment, the GRV is calculated using an impedance approach. The GRV is also calculated using the conductivity approach described and explained in Figs. 53-61. The calculations resulting from the impedance approach and the conductivity approach are then compared to each other via an algorithm. The exemplary algorithm calculates the difference in the calculations of the points and the difference in the calculations over time to determine if they are in agreement to determine an output that indicates whether the calculations are within a determined tolerance of agreement or they are not in agreement or are insufficient. The calculations can be combined or smoothed by the algorithm using exemplary techniques that can be utilized in this embodiment, including but not limited to moving averages, least squares, exponential smoothing, and LOESS / LOWESS regression. If the calculations are in agreement, this can be indicated to the controller, potentially indicating high confidence in the GRV and / or gastric emptying calculations.

[0302] In an exemplary device, a common set of electrodes can be used to measure both impedance and conductivity. FIG. 22E shows an embodiment of a GRV sensor consisting of four electrodes in a tetrapolar impedance measurement configuration. To measure GRV, the source electrodes are 2205 and 2202 and the sense electrodes are 2206 and 2201. The conductivity sensor in this embodiment uses two electrodes 2201 and 2202 to simultaneously inject or introduce a current and a sense voltage forming a bipolar conductivity measurement configuration. In an exemplary embodiment, the conductivity sensor can be configured with four electrodes. Electrodes 2201 and 2202 measure the conductivity at the distal tip, and electrodes 2205 and 2206 measure the conductivity closer to the tube. This configuration is similar to FIG. 53, where electrode 5304 is equivalent to electrodes 2201 and 2202, and electrode 5312 is equivalent to electrodes 2205 and 2206. Each combination of electrodes simultaneously injects a current and a sense voltage forming a bipolar conductivity measurement configuration.

[0303] In exemplary embodiments, the electrodes of FIG. 22e and FIG. 53 can be applied to the lubricant via a conductive ink. Many different types of conductive inks can effectively collect this data. In exemplary embodiments, the conductive ink used is AGCL-675 silver / silver chloride ink provided by a company called Conductive Compound. In these embodiments, the conductive ink is printed or otherwise applied directly to the surface of the feed tube.

[0304] In an exemplary embodiment, pH is also calculated and used by an exemplary algorithm along with impedance-based and conductivity-based calculations of the GRV, which combines the pH measurement with the impedance and conductivity GRV measurements to determine a combined measurement or index of the GRV.

[0305] Some embodiments of the GRV measurement device can include a feeding tube kink detection mechanism to detect if the feeding tube is kinked, and also detect if the tube is kinked after placement.

[0306] Some embodiments of the GRV measurement device can include a retention mechanism, such as a retention balloon, to hold the feeding tube in place after placement. The retention mechanism is movable relative to the feeding opening of the feeding tube e to adjust for different size stomachs, etc. The retention mechanism, such as a balloon, can be long or only on one side of the feeding tube with a portion of the balloon in the esophagus. If the sealing mechanism is a balloon, the balloon can be compliant or non-compliant. The balloon can be a low pressure balloon. FIG. 62 shows an embodiment of a GRV measurement device with a retention balloon 6202.

[0307] Some embodiments of the GRV measurement device can include the ability to test if the supply tube is bent or kinked. In one embodiment, the controller can introduce pressurized fluid (gas or liquid) into the lumen of the supply tube and measure the pressure required for the liquid to flow through the lumen. A baseline pressure can be sensed on the unbent supply tube to determine the unbound pressure range. As the tube bends or kinks, the pressure required increases. The controller can measure and track this pressure over time and can determine the condition of the supply tube based on absolute pressure, relative pressure, change in pressure, or the slope of the change in pressure over time.

[0308] Bends or kinks in the feeding tube can also be measured electronically, for example, by measuring the proximity of the electrodes to each other. If the electrodes are closer together than the spacing along the feed tube, then a kink or slight bend is likely to be present in the lubricant. This can be done by measuring the impedance and conductance between the electrodes. The pair of electrodes can be changed by the controller to determine the proximity of the GRV versus the electrodes. Alternatively, the same electrode pair may be used.

[0309] See, for example, Figures 63 and 64. Figure 63 shows a GRV measurement device having a pH sensor 6302, an opening (for feeding) 6304, and electrodes 6306 including electrodes 1, 2, 3, 4, 5, 6, 7 and 8. To determine the conductance / impedance at the electrode pairs, electrode pairs 1 and 2, 3 and 4, 5 and 6, and 7 and 8 are used as pairs during feeding and placement of the feed tube. However, different electrode pairs can also be used. For example, electrode 1 and electrode 6 can be used as a pair. The distance between electrodes 1 and 6 can be determined via the conductance / impedance. If the device is relatively straight, the distance between electrodes 1 and 6 is Z. The Z shown in Figure 64 * If the distance becomes too short, such as , the controller will sound an alarm / alarm or automatically attempt an untwisting procedure to attempt to untangle the tubing. Note that kink detection may include any electrode pair and the relative distance of the pair. For example, the conductance / impedance between the original electrode pair will not change in the presence of a kink, but the conductance / impedance between the more distant electrode pair may change. This combination can indicate a bent / kinked situation.

[0310] The ECG signal can also be detected by electrodes on the GRV measurement device to determine the location of the tip or other areas, which can be used to aid in placement of the feeding tube and also to detect kinks.

[0311] The electrodes may also be used to detect the electrical state of the stomach muscles, for example, myoelectric signals may be detected to determine tube placement and tube kinking.

[0312] Anatomical pressure can also be measured using a GRV measurement device. Anatomical pressure can be measured via the lumen of the feeding tube and / or via a balloon or pressure sensor on or within the feeding tube to determine placement within the anatomy.

[0313] The GRV measurement device can be straightened or stiffened during or after placement by occluding the supply lumen with a balloon, balloon or other mechanism. The lumen of the supply tube may then be pressurized to make it more rigid. Alternatively, a balloon can extend into the supply lumen, or into another lumen, or outside the supply tube to stiffen / straighten the tube.

[0314] A variable durometer feed tube can also be used to prevent kinking and aid in placement. For example, the feed tube of the GRV measurement device can be softer towards the stomach end.

[0315] A guide sheath can be used over the supply tube portion of the GRV measurement device to control the durometer of the supply tube during placement and after installation or to release the tube. The guide sheath may be slidable over the supply tube to change the relative stiffness of different sections along the length of the tube.

[0316] A guide stylet is used inside the lumen of the feeding tube portion of the GRV measurement device to control the durometer of the feeding tube during and after placement or to anchor the tube. The guide stylet may be slidable within the lumen of the feeding tube to change the relative stiffness of different sections along the length of the tube.

[0317] The GRV measurement device may include a sheath or lumen that houses a camera or esophageal scope for viewing tube placement.

[0318] It is also desirable to prevent biofilm and / or bacterial buildup on and in at least the feeding tube portion of the GRV measurement device. This can be accomplished by using antimicrobial coal or by impregnating the device material with an antimicrobial material. For example, the feeding tube portion can be made of a material impregnated with silver or coated with silver or other antimicrobial material. The coating material may be present only on the inside of the feeding lumen.

[0319] In an exemplary embodiment, the electrodes and wires of Figures 13, 22e and 53 can be applied to the lubricant via a silver-containing conductive ink, such as AGCL-675 silver / silver chloride ink provided by a company called Conductive Compounds. In this embodiment, the silver-impregnated conductive ink can be sufficient to provide an antimicrobial effect.

[0320] UV, or other wavelengths, can be used with light inside the lumen of the feeding tube to disinfect the lumen. For example, a fiber optic can be inserted into the feeding tube lumen and UV light can be shined into the lumen between feeds. This can be done manually or automatically. The fiber optic can be inserted between feeds, removed between feeds, or left in place between feeds.

[0321] The lumen of the feeding tube can be flushed during feeding with saline, antibacterial flush or other suitable flush. The flushing fluid either enters the stomach or circulates (introduced into the lumen and removed from the lumen) so that no or only a small amount of the flushing fluid enters the stomach. The introduction and removal of the flushing fluid may both be through a single lumen or through two or more lumens. For example, the flushing fluid may be introduced and then pushed out or pushed out with another fluid (liquid or gas). Alternatively, the flushing fluid may be introduced through one lumen and withdrawn through another lumen. For example, the feeding opening may be sealed or blocked from the flushing fluid using a balloon, sealing mechanism, valve, etc. FIG. 65 illustrates a cross section of a feeding tube of a GRV measurement device having a flush introduction lumen 6502 and a flush withdrawal lumen 6504. During feeding, the feeding opening can be closed and flushing fluid can be introduced through the lumen 6502. Lumen 6502 is in fluid communication with lumen 6504 over the occluded supply opening so that flushing fluid can be collected via lumen 6504. This flushing process may be performed manually or automatically by a controller between supplies.

[0322] Simple manufacture and reduced cost of the GRV measurement device is also desirable. The electrical connections for the electrodes may be via wires, or conductive ink printed on the tube shaft. The connections may be on the outside of the shaft, embedded in the wall of the shaft, or embedded in the lumen of the shaft. In one embodiment, the electrical wires are between the concentric tubes of the feed tube shaft. In this configuration, they may be fixed in place or may float freely in the space between the tubes.

[0323] 66 shows an embodiment of a GRV measurement device having an outer tube 6602, an inner tube 6604, and an electrical wire 6606. The electrical wire is between the inner and outer tubes and connects to a controller at one end and to an electrode and / or pH sensor at the other end.

[0324] 67 shows an embodiment of a GRV measurement device having a wire (or wires) 6702 within a supply lumen 6704. In this embodiment, the wire or other electrical connection is inside the supply lumen and may also be used to sterilize the supply lumen.

[0325] Figure 68 shows an embodiment of a GRV measurement device having nested tubes, each with one or more electrodes / sensors. In this embodiment, electrical connections, i.e., wires, may pass between the tubing, similar to the embodiment shown in Figure 66. Electrodes 6802 may be placed at or near the distal tip of each tube.

[0326] Alternatively, the electrical connection can be made with wires or braids embedded or co-extruded into the feeding tube tubing. For easier and lower cost manufacturing, conductive polymers can be used for the electrodes.

[0327] The pH measuring device may be a separate device such as a guidewire or stylus with a pH sensor at its tip, which is used only for placement of the tube and then removed for feeding as needed, so that wiring for the pH sensor does not need to be incorporated into the feeding tube.

[0328] A pH measurement can be obtained by using two electrode rings of dissimilar metals by measuring the electron flow between the two electrodes.

[0329] A balloon or other spacer may be incorporated into the GRV measurement device at or near the electrode to prevent the electrode from contacting the stomach wall.

[0330] Neuromodulation can be used to induce contractions in cases where the stomach is slow to mobilize (gas paralysis). Electrodes or other electrodes can be used for this by activating them in turn to stimulate the stomach / intestinal / esophageal walls. The optimal frequency at or near the frequency of the natural peristaltic waves will be.

[0331] All of the embodiments disclosed herein can use an automatic feedback loop to automatically provide the appropriate amount of feed to the patient based on the GRV measurement. The GRV measurement system can be audible or of other type. It can alert when the amount of food in the stomach is unacceptable. The water supply line can incorporate a pump, flow system, pressure system or other system to help clear the water supply line if a clog occurs in the water supply line. A clog detector can be incorporated into the system. [Explanation of symbols]

[0332] 102 Feeding Tube 110 Monitor 112 Connector 116 Enteral Feeding Pump

Claims

[Claim 1] an elongate body having a length configured for insertion into a stomach of a subject; at least one sensor disposed along the elongate body and positionable for placement within a stomach; a plurality of additional sensors disposed at a plurality of locations along the elongate body, the plurality of additional sensors being configured to be disposed within an esophagus when the at least one sensor is positioned within the stomach; and a controller in electrical communication with the at least one sensor, the controller configured to detect changes in conductivity or impedance of stomach contents measured by the sensor, the controller in electrical communication with the plurality of additional sensors, the controller further configured to monitor a reflux signal indicative of a reflux event, the controller further configured to determine a position of the elongate body within the subject's body based on positioning signals received from the at least one sensor and two or more of the plurality of additional sensors, the controller further configured to identify a position of the elongate body including within the lungs based on the positioning signals further including a respiratory artifact.

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