Method and apparatus for accessing and monitoring the gastrointestinal tract

Abstract

Methods and devices for accessing and monitoring the gastrointestinal tract are disclosed.SOLUTION: One variation of a delivery system may generally include a gastric access device having a length. One or more sensors may be positioned along the length and a controller may be in communication with the one or more sensors. The controller may be configured to receive signals from the one or more sensors relating to a parameter of fluid in the stomach of the subject. Further, the controller may be configured to determine a gastric residual volume (GRV) based on the signal and to control a rate of the feed or formulation introduced into the stomach such that the GRV is maintained at a stable level.SELECTED DRAWING: Figure 18

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 256,834, filed October 18, 2021, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to feeding tube placement / monitoring, gastric volume measurement, gastric emptying, and gastric reflux detection and management, and management of patient care.

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

[0004] Enteral feeding through a feeding tube allows a patient to receive nutrition when they are unable to receive nutrition through their mouth and swallow safely, or to provide supplemental nutrition.

[0005] Additionally, placing a gastric tube (nasogastric or orogastric, also referred to herein as an NG tube or feeding tube) presents challenges. NG tubes can be inadvertently placed in the trachea instead of the esophagus, potentially resulting in complications or even death. A solution is also needed to accurately place an NG tube in the gastrointestinal tract (i.e., esophagus, stomach, or intestines) rather than the trachea or lungs.

[0006] It is also important to track the patient's eating status to ensure that the patient does not under- or over-eat. Note that the term "GRV" as used herein may refer to gastric residual volume or gastric emptying or gastric residual supply or gastric motility or gastric status.

[0007] It is also important to prevent, identify, and manage gastric reflux during enteral feeding, as reflux can be introduced into the lungs, causing serious medical complications. Summary of the Invention

[0008] Disclosed herein are embodiments of gastric access devices that improve the ability to reliably access the GI tract and avoid inadvertent entry into a patient's trachea / lungs. The embodiments include one or more sensor types for determining whether the device is in the GI tract or trachea / lungs. Some sensor types, such as impedance / conductivity sensors, pH sensors, ECG (electrocardiogram) sensors, pressure sensors, etc., positively identify the GI tract. Some sensor types, such as temperature sensors, humidity sensors, O2 sensors, CO2 sensors, flow sensors, acoustic sensors, pressure sensors, etc., positively identify the trachea / lungs. Some of these sensors can identify both. A combination of sensors, where at least one of the sensors positively identifies the GI tract and at least one of the sensors positively identifies the trachea / lungs, can be used to properly locate the device within the GI tract (or trachea / lungs). Alternatively, two different sensor types that positively identify the GI tract can be used to properly locate the device. Alternatively, two different sensor types that positively identify the trachea / lungs can be used to properly locate the device.

[0009] In some embodiments, only one sensor type is required to properly locate the device. In some embodiments, two sensor types are available to properly locate the device. In some embodiments, three sensor types are available to properly locate the device. Not all available sensor types will be used with all patients in all environments.

[0010] One or more of any sensor type may be used along the length of the gastric access device. In some embodiments, two or more sensors are placed on or along the gastric access device so that at least one sensor is at a functional location. For example, two or more temperature sensors may be present along the gastric access device so that at least one temperature sensor is in a position to measure the surrounding fluid and does not contact tissue as the device advances. For example, two or more temperature sensors may be placed at two or more locations circumferentially around the device. Alternatively or additionally, two or more temperature sensors may be placed at two or more locations along the length of the device.

[0011] A device monitor / controller can analyze signals from one or more types of sensors to determine the device's location. Some signal types may provide more confidence than others and may override other signal types. Some signal types may take longer to analyze and may act as confirmatory or disconfirmatory signals to previous signals. The monitor may receive signals from sensors continuously, intermittently, or on demand. Some signal types may be received and analyzed essentially in real time, while some signal types may take longer to receive and analyze.

[0012] Some embodiments of the gastric access device include the ability to monitor gastric residual volume or gastric emptying. Some embodiments include the ability to control the delivery rate and / or volume based on gastric residual volume or gastric emptying.

[0013] Some embodiments of the gastric access device include preventing, identifying, and / or managing gastric reflux.

[0014] In some embodiments, the sensor types may also be used to monitor the patient. For example, a temperature sensor may be used to locate the device and monitor the patient's temperature after the device is in place. An impedance / conductivity sensor may be used to determine the location of the device, identify reflux, and / or monitor gastric residual volume or gastric emptying over time after the device is in place. An ECG sensor may be used for placement and may also be used to monitor the patient's ECG after the device is in place. The ECG sensor, impedance / conductivity sensor, and / or other sensors may use the same or different electrodes.

[0015] One variation of a feeding system may generally include a gastric access device having a length, one or more sensors positioned along the length, and a controller in communication with the one or more sensors, the controller configured to receive signals from the one or more sensors related to parameters of fluid in the subject's stomach. The controller may be further configured to determine a gastric residual volume (GRV) based on the signals and to control a rate of feeding or compound introduced into the stomach such that the GRV is maintained at a stable level.

[0016] One variation of a method for managing delivery of a feed or compound into a subject's stomach may generally include contacting fluid in the subject's stomach via one or more sensors positioned along the length of a gastric access device, receiving signals from the one or more sensors into a controller in communication with the one or more sensors, the signals related to a parameter of the fluid, determining a gastric residual volume (GRV) based on the signals, and controlling a rate of the feed or compound introduced into the stomach such that the GRV is maintained at a steady level. [Brief explanation of the drawings]

[0017] Various exemplary embodiments are described in detail below with reference to the following drawings.

[0018] [Figure 1]1 illustrates an embodiment of a gastric access device in place within the human anatomy. [Figure 2] 10 illustrates the relative conductivity sensed by an impedance or conductivity sensor incorporated into a gastric access device in different regions of the anatomy. [Figure 3] 1 shows readings from a gastric access device with two temperature sensors. [Figure 4] 1 shows readings from a gastric access device with two temperature sensors. [Figure 5] 1 shows a gastric access device being advanced through the trachea and into the lungs. [Figure 6] 1 shows a gastric access device placed in a patient's stomach. [Figure 7] 10 shows a flow chart outlining the functionality of a controller in communication with a gastric access device having impedance / conductivity sensor(s) and temperature sensor(s). [Figure 8] 10 shows a gastric access device feeding tube with the sensor in close proximity to the heart. [Figure 9] 1 illustrates an embodiment of a gastric access device having an ECG sensor integrated into the nose, nostril, mouth, or face patch. [Figure 10] 10 shows a flowchart outlining the functionality of a controller in communication with a gastric access device having impedance / conductivity sensor(s) and ECG sensor(s). [Figure 11A] 1 illustrates an embodiment of a portion of a gastric access device. [Figure 11B] 1 illustrates an embodiment of a portion of a gastric access device. [Figure 12] 1 illustrates an embodiment of a portion of a gastric access device. [Figure 13] 1 illustrates an embodiment of a portion of a gastric access device. [Figure 14] 1 illustrates details of a monitor of some embodiments. [Figure 15A] 1 illustrates an embodiment of a gastric access device that includes tissue sensing electrode(s) for sensing tissue impedance / conductivity. [Figure 15B] 1 illustrates an embodiment of a gastric access device that includes tissue sensing electrode(s) for sensing tissue impedance / conductivity. [Figure 16A] 1 illustrates an embodiment of a gastric access device including tissue electrode(s) / sensor(s) as well as a reflux sensor. [Figure 16B] 1 illustrates an embodiment of a gastric access device including tissue electrode(s) / sensor(s) as well as a reflux sensor. [Figure 16C] 1 illustrates an embodiment of a gastric access device including tissue electrode(s) / sensor(s) as well as a reflux sensor. [Figure 17] 16B illustrates the embodiment shown in FIG. 16A with the addition of an expandable member and suction tube. [Figure 18] 18 shows the embodiment shown in FIG. 17 in place within the anatomy. [Figure 19] 13 shows an embodiment in which the suction tube is located next to the main device shaft of the gastric access device. [Figure 20] 1 illustrates an embodiment of a gastric access device designed to locate and pass through the pyloric sphincter to allow delivery within a patient's intestine. [Figure 21A] 10 illustrates an embodiment for measuring / determining intraperitoneal pressure via a feeding tube. [Figure 21B] 10 illustrates an embodiment for measuring / determining intraperitoneal pressure via a feeding tube. [Figure 21C] 10 illustrates an embodiment for measuring / determining intraperitoneal pressure via a feeding tube. [Figure 22A] 10 illustrates an embodiment for measuring / determining IAP (intra-abdominal pressure) via a feeding tube. [Figure 22B] 10 illustrates an embodiment for measuring / determining IAP (intra-abdominal pressure) via a feeding tube. [Figure 22C] 10 illustrates an embodiment for measuring / determining IAP (intra-abdominal pressure) via a feeding tube. [Figure 23] 1 illustrates another embodiment of a gastric access device system that may be used to measure / determine IAP. [Figure 24] 10 illustrates an embodiment of a gastric access device that may be used to detect bending and / or twisting of the device. [Figure 25] 10 illustrates an embodiment of a gastric access device that may be used to detect bending and / or twisting of the device.

[0019] [Figure 26] 1 illustrates some of the anatomical landmarks that may be used when placing a gastric access device. [Figure 27] 10 illustrates an embodiment in which the temperature sensor can use the same electrodes as the impedance / conductivity electrodes. [Figure 28A] 1 shows the gastric access device within a scale showing the approximate lengths of different sections of the anatomy. [Figure 28B] 1 illustrates an example of placement of a gastric access device in a child. [Figure 29A] 10 provides details regarding an embodiment using one electrode for two or more sensors. [Figure 29B] 10 provides details regarding an embodiment using one electrode for two or more sensors. [Figure 30A] 1 shows an embodiment of an anti-clogging mechanism. [Figure 30B] 1 shows an embodiment of an anti-clogging mechanism. [Figure 30C] 1 shows an embodiment of an anti-clogging mechanism. [Figure 30D] 1 shows an embodiment of an anti-clogging mechanism. [Figure 30E] 1 shows an embodiment of an anti-clogging mechanism. [Figure 31] 1 shows an example of a gastric access device, showing potential locations for electrode pairs (impedance / conductivity sensors) as well as temperature sensors. [Figure 32] 1 shows a graph illustrating signature signals from various sensors on a gastric access device as the device is advanced and retracted through the digestive system. [Figure 33]FIG. 1 is a block diagram of a data processing system that may be used with any embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] For ease of explanation, exemplary embodiments are described below with reference to the drawings in relation to placing a feeding tube, assessing gastric volume / emptying, and preventing / identifying / managing / monitoring gastric reflux in a patient.

[0021] FIG. 1 shows an embodiment of a gastric access device in place within the human anatomy. The anatomy includes the esophagus 102, stomach 104, trachea 106, lungs 108, and heart 110. A gastric access device 112 is shown advanced through the esophagus into the stomach. The gastric access device may include one, two, three, or more types of sensors to aid in accessing the stomach or other areas of the gastric tract, assess gastric residual volume or gastric emptying, and prevent, identify, and / or manage reflux during feeding. The gastric access device may include a lumen for introducing a feed into the patient's stomach. Alternatively, the gastric access device may be used in conjunction with (inside or along) a feeding tube.

[0022] In FIG. 1 , two types of sensors are shown: Type 1 is shown at 114 and Type 2 is shown at 116. In some embodiments, sensor Type 1 may be a pair or multiple electrodes for sensing impedance or conductivity. Type 2 sensor may be a temperature sensor. Other types of sensors include moisture sensors, pressure sensors, chemical sensors, ECG sensors, EGG (electrogastrogram) sensors, pH sensors, optical sensors, etc. For example, a pressure or moisture sensor may be used to detect pressure or moisture fluctuations associated with breathing and thus determine when the device is endotracheal / intrapulmonary.

[0023] The sensors may be used to assist in device placement, or to assess gastric emptying / contents, or to prevent, identify, and / or manage reflux, or for any two or more of these purposes. For example, some embodiments of gastric access devices include at least one impedance sensor for measuring the impedance of the environment surrounding the sensor and at least one temperature sensor. The impedance sensor(s) may be used for device placement and / or monitoring gastric emptying and / or reflux, while the temperature sensor(s) may be used for device placement and possibly for ongoing patient temperature monitoring.

[0024] One or more temperature sensors may be used for device placement by sensing the relatively small temperature fluctuations caused by breathing ambient air that is at a different temperature than the body's temperature. For example, room temperature air is typically cooler than body temperature. If the gastric access device is accidentally advanced into the trachea instead of the esophagus, the temperature sensor(s) on the gastric access device will detect the temperature fluctuations associated with breathing. These temperature fluctuations are not present when the gastric access device is properly placed in the gastric system, i.e., the esophagus, stomach, or intestine.

[0025] A temperature sensor on the gastric access device transmits a temperature signal from the sensor to a controller via leads within the gastric access device. This temperature signal exhibits breathing-related fluctuations when the gastric access device is placed incorrectly in the trachea or lungs. This is important because it is a dangerous mistake that could result in complications or even death if a supply is subsequently accidentally introduced into the lungs.

[0026] The embodiment of FIG. 1 may include, for example, two or more impedance sensors 114 and two or more temperature sensors 116. The impedance sensors may be used for device placement and / or to measure gastric residual volume (GRV) / gastric emptying and / or reflux. Details of embodiments including GRV / gastric emptying using impedance or other sensors are included in U.S. Patent Application Publication No. 2017-0071502, filed November 23, 2018; U.S. Patent Application Publication No. 2016-0331298, filed July 28, 2017; and U.S. Patent Application Publication No. 2016-0078195, filed November 13, 2016, each of which is incorporated herein by reference in its entirety. A temperature sensor may be used to confirm device placement or, in certain circumstances, serve as a primary placement indicator.

[0027] Figure 2 shows the relative conductivity sensed by an impedance or conductivity sensor integrated into a gastric access device in different regions of the anatomy. The conductivity of the stomach is significantly higher than that of the lungs. As the gastric access device advances through the nose or mouth into the esophagus and possibly into the stomach, the conductivity / impedance sensor(s) can identify when the distal tip of the device is in the stomach by this increase in conductivity (or decrease in impedance) due to contact with the fluid contents of the stomach, which generally have a higher conductivity (lower impedance) than the environment or fluid of the esophagus. This sensing is also real-time or very rapid, on the order of less than one second or a few (1-4) seconds. However, there may be situations where this change in impedance / conductance is less clear, or where the impedance / conductance sensor on the gastric access device may sense areas of high conductivity in the trachea or lungs, such as when the sensor is embedded in mucus or rests against tissue.

[0028] A secondary sensing system may be utilized to confirm that the gastric access device is positioned in the stomach and not the lungs or trachea. For example, one or more temperature sensors may be used on the gastric access device to sense temperature fluctuations or the lack of temperature fluctuations caused by breathing. If temperature fluctuations associated with breathing are detected, the device is likely in the trachea or lungs and should be retracted. If temperature fluctuations associated with breathing are not detected and the impedance sensor(s) indicate high conductivity / low impedance, the device is likely in the stomach. Temperature fluctuations associated with breathing are likely to have a frequency associated with breathing, for example: 6 weeks: 30-40 breaths / minute 6 months: 25-40 breaths / min 3 years old: 20-30 breaths / min 6 years old: 18-25 breaths / min 10 years old: 17-23 breaths / min ·Adult: 12~18 breaths / min Elderly people aged 65 and over: 12-28 breaths / min Elderly people over 80: 10-30 breaths / min

[0029] The controller may incorporate a frequency filter to filter out these or other respiratory frequencies in order to separate respiration-related temperature fluctuations from the temperature signal over time.

[0030] These frequencies can be used by the controller / monitor to determine whether temperature fluctuations are related to breathing. This signal may need to be analyzed over two or more breaths, and as a result, may take longer for the controller to analyze than the impedance / conductance signal. Determining whether the temperature signal represents a breath may take 8-15 seconds or 10-20 seconds. As a result, the temperature reading can be used as a secondary indicator of device placement (confirming the impedance sensor placement index). The user may be prompted by the device to pause the advancement of the device while this confirmation is performed.

[0031] Figures 3 and 4 show readings from a gastric access device having two temperature sensors, one sensor 18 cm from the distal tip of the device and one sensor 40 cm from the distal tip of the device. Figure 3 shows temperature readings when the device is placed in the patient's esophagus or stomach. Figure 4 shows temperature readings when the device is placed in the patient's trachea or lungs. In some embodiments, at least one temperature sensor may be designed to be positioned in the trachea when the device tip is in the patient's lungs.

[0032] FIG. 4 illustrates temperature fluctuations in the temperature signal associated with breathing, which are not shown in FIG. 3. If the temperature sensor is in contact with or embedded in tissue, temperature fluctuations may not be detected even if they are present in the environment around the tissue. This is shown in the top graph of FIG. 4. As the device advances into the lung, the distal-most sensor becomes somewhat embedded in the tissue, and the temperature signal flattens out. A second, more proximal temperature sensor clearly exhibits temperature fluctuations in the bottom graph of FIG. 4. Due to this phenomenon, two or more temperature sensors may be beneficial, with the controller looking for temperature fluctuations associated with breathing from at least one of the temperature sensors. The temperature sensor (or any sensors) may also be placed at different locations on the device, both along its length and / or around its circumference. For example, temperature sensors may be placed 180 degrees apart from each other around the radius and / or along the length of the gastric access device.

[0033] In some embodiments, a temperature sensor is used to sense the temperature at the time and location where the device first enters the body. The temperature sensor can sense temperature fluctuations due to breathing in the patient's throat as the device is inserted. These fluctuations may cease when the device passes the junction between the trachea and esophagus. Because this is a relatively short distance into the patient (i.e., approximately 5-15 cm), a flattening of temperature fluctuations over this distance may be an indicator that the device is properly propagating down the esophagus relative to the trachea. This flattening or disappearance of temperature fluctuations over this relatively short distance into the patient is a further indicator that the device is properly placed. Alternatively, a lack of flattening of temperature fluctuations or an increase in the magnitude of temperature fluctuations as the device advances is an indication that the device is being advanced into the trachea. The distance beyond the lips that the device has advanced may be automatically determined by the system by utilizing dimensional markings or landmarks along the entire length of the device shaft and a camera or other detection mechanism at the lips / device entry point.

[0034] In some embodiments, one or more temperature sensors on the feeding tube can sense the ambient temperature before the tube is inserted into the patient. In some embodiments, the ambient temperature may be measured continuously or intermittently over time using a temperature sensor outside the patient, such as an ambient temperature sensor integrated into the controller or an ambient temperature sensor at the proximal end of the feeding tube that remains outside the patient. The ambient temperature sensor may also be remote from both the feeding tube and the controller but in communication with the controller. The ambient temperature may be used to determine the patient's relative temperature at different locations within the anatomy by comparing the temperature sensed by the sensor on the feeding tube to the ambient temperature. In this way, relative temperature can be measured at different locations along the feeding tube and within the anatomy. An average temperature may also be used by looking at a damped temperature signal. An average or damped temperature signal may not show the same variation in temperature in the lungs or lack of variation in temperature in the esophagus, but if the ambient temperature is lower than body temperature, the average temperature in the lungs will be lower than the average temperature in the esophagus. By monitoring the average / decaying temperature at one point, two points, or along the feeding tube as the device advances, the controller can determine approximately where the device is within the anatomy. Different signals at different locations along the length of the feeding tube provide temperature information (either average temperature or temperature fluctuations) that can indicate whether that segment of the feeding tube is over the pharynx, trachea, esophagus, lungs, stomach, intestines, or against tissue. Other sensors, such as impedance / conductivity sensors, may be used to help identify location. For example, if temperature sensors are measuring body temperature and not temperature fluctuations, the portion of the feeding tube with these sensors may be in the stomach or in contact with tissue. A conductivity / impedance sensor can distinguish between the two. ECG, pH, or other sensor types could also be used.

[0035] FIG. 5 shows a gastric access device being advanced through the trachea and into the lungs. This is an undesirable situation, and embodiments of the gastric access device identify this as such. The impedance / conductivity sensors do not sense the significant increase in conductivity shown in the graph of FIG. 2. Additionally, the temperature sensors detect temperature fluctuations associated with breathing, as shown in FIG. 4. These signals are received by the controller / monitor 502 via a wired or wireless connection 508 connected to the gastric access device 112 via a hub 510. The sensors on the access device 112 are electrically connected to the hub 510 via leads within the device 112 that extend from the various sensors to the hub 510. The monitor 502 is also connected to a feeding pump 504 via a wired or wireless connection 506 to control the patient's feeding via a feeding lumen of the device 112 or via a separate feeding tube. The monitor interprets one or more of these signals to indicate that the device is not properly positioned and needs to be retracted.

[0036] Figure 6 shows a gastric access device placed in a patient's stomach. In this situation, the impedance / conductivity sensor(s) indicate high conductivity and the temperature sensor does not indicate breathing-related temperature fluctuations. The monitor interprets one or more of these signals to indicate that the device is properly placed in the stomach.

[0037] 7 shows a flowchart outlining the functionality of a controller in communication with a gastric access device having impedance / conductivity sensor(s) and temperature sensor(s). Box 702 represents the controller instructing the user to advance the device into the patient. As the device advances, the controller receives signals from sensors integrated into the gastric access device. The controller may continue to instruct the user to advance the device until the impedance / conductivity sensors sense high conductivity or low impedance, or until the temperature sensor(s) detect temperature fluctuations associated with breathing.

[0038] If the temperature sensor is past the RGJ (respiratory-gastric junction) and the controller receives a signal from the temperature sensor indicating temperature fluctuations associated with respiration, as shown in box 714, the controller will indicate to the user that the device is likely in the trachea or lungs and instruct the user to retract the device, as shown in box 716.

[0039] If the sensor initially senses high conductivity during device advancement, as shown in box 704, it is possible that the gastric access device is in the stomach and the sensor is sensing stomach contents. The controller may indicate that the device is in the stomach, or the controller may ask the user to pause for a few seconds by displaying or playing a pause signal so that temperature sensor signal data can be collected to determine whether there are any breathing-related fluctuations detected by the temperature sensor. If these fluctuations are detected, as shown in box 706, if the temperature sensor passes through the RGJ, the controller may determine that the access device may be in the lungs and instruct the user to retract the device, as shown in box 708. If no temperature fluctuations are detected, as shown by box 710, the controller may confirm that the device is properly placed in the stomach, as shown in box 712.

[0040] In addition to, or instead of, the impedance / conductivity and temperature sensors, other sensors may be used to determine the location of the gastric access device within the anatomy. For example, one or more electrocardiogram (ECG) sensors can be used to determine whether the gastric access device is above or below the heart. If the device is below the heart, it is unlikely to be in the lungs or trachea and therefore more likely to be in the stomach. FIG. 8 shows the relative anatomical structures of the lungs 108, heart 110, and stomach 104. Note that the stomach is below the heart, while the lungs are above or around the level of the heart. Some embodiments of gastric access devices may include an ECG sensor 802 in addition to the impedance sensor 804. These sensors, like other sensors on gastric access devices disclosed herein, have leads or wires extending along the length of the device to connect the device to the device hub 510. The device hub is electrically connected to a monitor that receives signals from the various sensors. In some embodiments, both sensor types utilize the same electrodes.

[0041] The ECG sensor senses the electrical activity of the heart, including a signal that includes, for example, a P zone, a Q zone, an R zone, an S zone, a T zone, a U zone, an origin of the signal, etc. The signal has a magnitude and a frequency, and various zones may include peaks of various positive and negative magnitudes. The gastric access device may have two or more ECG sensors, such as sensor 804, on the device itself. Alternatively, the gastric access device may have one or more ECG sensors, and the system may include an external ECG sensor 806. The external ECG sensor also electrically communicates with the monitor, either wired or wirelessly. As the gastric access device advances, the ECG signal may be continuously received by the monitor. Because the ECG sensor is sensing the electrical activity of the heart, the signal changes as the sensor traverses the esophagus, passes through the heart, and heads toward the stomach. These changes may be in magnitude or direction (positive or negative) of one or more of the zones of the ECG signal. This change may vary depending on the location of the ECG sensor within the system. For example, a system with one ECG sensor on the feeding tube and one on the sternum may exhibit different changes than a system with two or three ECG sensors on the feeding tube. The changes may vary depending on the system configuration, but the changes are detectable by the controller for a given system configuration due to changes in the relative location of at least one or more of the ECG sensors (the sensor(s) on the feeding tube) with respect to the heart as the sensors pass by the heart.

[0042] FIG. 8 shows a gastric access device feeding tube as the sensor approaches the level of the heart. At this point, it may still be unclear from the ECG sensor measurements whether the access device is in the esophagus or the lungs. However, as the device advances down the esophagus, the ECG readings change to a signature indicating that the device is passing through and / or past the heart. For example, the ECG signal may invert, or certain zones of the ECG may invert, or the signal magnitude may change, or certain zones of the ECG may change magnitude. When the controller senses this signature, it determines that the gastric access device is in the stomach below the heart. An external ECG sensor 806 may or may not be present.

[0043] The ECG sensor may be used in conjunction with any other sensors, including impedance / conductivity sensors and / or temperature or other sensors, to assist in locating the gastric access device within the stomach. Any of the sensor types may share the same electrodes with other sensor types.

[0044] 9 shows an embodiment of a gastric access device with an ECG sensor integrated into the nose or nostril or mouth or face patch 902. The sensor can be placed outside the nose, inside the nose, outside the mouth, inside the mouth, or elsewhere on the face. The sensor can be integrated into the feeding tube of the gastric access device itself, for example, as part of a tape that holds the device in place.

[0045] 10 shows a flowchart outlining the functionality of a controller in communication with a gastric access device having impedance / conductivity sensor(s) and ECG sensor(s). Box 1002 represents the controller instructing the user to advance the device into the patient. As the device advances, the controller receives signals from sensors integrated into the gastric access device. The controller may continue to instruct the user to advance the device until the impedance / conductivity sensors sense high conductivity or low impedance, or until the ECG sensors detect a change in the ECG signal(s) indicating the device has passed under the heart.

[0046] If the controller receives a signal from the ECG sensor indicating that the device is below the heart, as shown in box 1014, the controller may indicate to the user that the device is likely in the stomach. Alternatively, or additionally, the controller may use a signal from the conductivity sensor to confirm placement. If the controller does not receive a signal from the impedance sensor(s) on the device indicating high conductivity or low impedance, as shown in box 1016, the controller may indicate to the user that the device is likely not in the stomach and to withdraw the device, as shown in box 1018. However, if the impedance sensor(s) on the device receive a signal indicating high conductivity or low impedance, as shown in box 1020, the controller indicates to the user that the device is likely in the stomach, as shown in box 1022.

[0047] If, during advancement of the device, the sensor initially senses high conductivity, as shown in box 1004, the gastric access device may be in the stomach. The controller may indicate that the device is in the stomach, and / or the controller may analyze the ECG sensor signal data to determine whether an ECG signal signature indicates that the device has passed the heart. If this signature is detected, as shown in box 1006, the controller determines and communicates that the access device is likely in the stomach, as shown in box 1008. If, as shown by box 1010, the ECG sensor signal signature indicates that the device has not passed under the heart, the controller may indicate that the device may not be in the stomach, and may indicate that the device should be retracted and re-advanced, as shown in box 1012.

[0048] Steps 1006 and 1014 (and similarly, step 704 in FIG. 7 ), which indicate that the ECG signal indicates that the device is under the heart, may include a substep of checking to ensure that the end of the feeding tube has not deviated, causing an inaccurate signal signature. This can be done by checking the impedance / conductivity between different sensors or different electrode pairs to see if they are closer to each other than if the feeding tube were relatively straight. For example, the controller may quickly check whether there is an abnormally high conductivity between the most distal impedance sensor and the next closest impedance sensor. The controller may then check whether there is an abnormally high conductivity between the most distal impedance sensor and the impedance sensor that is one sensor further away than the closest impedance sensor. If there is no abnormally high conductivity between the two impedance sensors on the feeding tube, the tube is likely not deviated, and the ECG signal signature can be trusted.

[0049] While the flowcharts illustrate the flow of an embodiment having two types of sensors, where one type of sensor can confirm or query device placement based on the other type of sensor, it should be understood that gastric access device embodiments can incorporate one, two, three, or more types of sensors. The sensors may operate independently or in concert, as shown in the flowcharts herein, for example, with a particular patient type or in a particular environment. Additionally, not all sensors are used for all patients. For example, a device embodiment may include three types of sensors, such as a temperature sensor, an impedance / conductance sensor, and an ECG sensor. One, two, or three types of sensors may be used for different patients and / or different environments. For example, three sensors may be used for most patients, but in a warm room, the temperature sensor may not be used. As another example, an ECG sensor may not be used for patients with known arrhythmias. In some embodiments, there are two types of sensors so that one or two types can be used for the majority of patients and environments. In some embodiments, there are two or more types of sensors for placement confirmation redundancy.

[0050] FIGS. 11A, 11B, 12, and 13 show some embodiments of a gastric access device. FIG. 11A shows the main device shaft 1102, feeding pump connector 1104, and monitor connector 1106. FIG. 11B is an enlarged view of the cross section of FIG. 11A within the oval outline. FIG. 11B includes electrodes 1108, with any pair of electrodes representing an impedance / conductivity sensor. The pairs of electrodes that make up a sensor need not be adjacent to each other. Also shown is a temperature sensor, such as a thermistor or thermocouple 1110, as well as an opening 1112 that allows feed to exit the device. FIG. 11B also shows exemplary distances in mm of some of the various sensors from the tip of the device. FIG. 11B shows a device with two temperature sensors 1110, circumferentially 180 degrees from each other and at different points along the length of the device. FIG. 12 shows four temperature sensors 1110, circumferentially opposite each other by 180 degrees at two different locations along the length of the device. While two locations are shown here, temperature sensors may be included in one or more locations. FIG. 13 shows a temperature sensor 1110 that wraps 360 degrees around the device, completely surrounding it. These and other embodiments allow the temperature sensor to sense fluctuations associated with breathing when the device is in the lungs so that the device's controller can instruct the user to retract the device. As shown in FIG. 4, having temperature sensors in two or more locations (circumferentially, longitudinally, or both) can help detect temperature fluctuations due to breathing in more situations. In some embodiments, the temperature sensors are circumferentially placed more than 90 degrees from each other. In some embodiments, the temperature sensors are circumferentially placed more than 45 degrees from each other. In some embodiments, at least two temperature sensors are circumferentially placed in one location. In some embodiments, at least three temperature sensors are circumferentially placed in one location. In some embodiments, at least four temperature sensors are circumferentially placed in one location. In some embodiments, at least two temperature sensors are circumferentially placed along the length of the device.In some embodiments, at least three temperature sensors are placed circumferentially along the length of the device. In some embodiments, at least four temperature sensors are placed circumferentially along the length of the device. Other configurations are also envisioned. For example, the temperature sensors may be within the monitor, with a fluid path extending from the sensors to the supply tube. Sensors other than temperature sensors may also be placed.

[0051] One or more temperature sensors may be placed so that they are in the trachea when the distal tip of the device is in the lungs. For example, the sensor may be placed approximately 250-350 mm from the distal tip. Alternatively, the sensor may be placed approximately 200-400 mm from the distal tip. Alternatively, the sensor may be placed approximately 100-150 mm from the distal tip for smaller patients. Alternatively, the sensor may be placed approximately 100-200 mm from the distal tip.

[0052] In some embodiments, one or more temperature sensors may be placed on the exterior of the gastric access device. In some embodiments, one or more temperature sensors may be placed entirely within the wall of the gastric access device. In some embodiments, one or more temperature sensors may be placed within the wall of the gastric access device such that the temperature sensor is exposed to the exterior of the device.

[0053] The ECG sensor and / or temperature sensor may be separate from the impedance / conductance sensor or may utilize some or all of the same electrodes. In embodiments where the same electrodes are used, different types of sensing (i.e., temperature, ECG, and impedance / conductance) may alternate with the same electrode or may be used at different locations or times during the procedure or with different patients. Different or the same leads may be used for different functions of a single electrode. Any of the sensors may utilize electrodes that completely surround the device or that only partially surround the device.

[0054] FIG. 14 shows details of the monitor 502 of some embodiments. One or more display areas can display information to the user. For example, shown here are a tube placement display area 1402, a real-time delivery rate display area 1404, and a delivery rate or delivery rate trend over time area 1406. Other display areas can include GRV / gastric emptying trend over time, real-time GRV / gastric emptying, instructions for placement (e.g., "back out," "pause," "continue," etc.), warning indications, gastric reflux inputs such as warnings to avoid, reflux event identification, management, etc. Audible prompts and / or alerts can also be played. Control buttons 1408 can include a power button, a settings button, etc., and can be physical or touchscreen buttons.

[0055] The placement display area 1402 may include a graphical representation of anatomical structures, including the esophagus, stomach, and lungs / trachea. This display may include colors indicating correct placement, questionable placement, and incorrect placement. For example, if one or more types of sensors sense that the device is in the stomach, the stomach may flash or show green. If one or more types of sensors sense that the device is in the lungs, the lungs may flash or show red. If neither the stomach nor the lungs are sensed by any type of sensor, the esophagus may flash green or another color to indicate to the user to continue advancing. The distance the device has traveled within the patient may be incorporated into the placement assessment. In some embodiments, the controller communicates with a sensor, such as an optical sensor, that automatically measures the length of the device within the patient. If there are conflicting signals from the sensor types, or from any one sensor type, the corresponding area of ​​the body may flash or show orange.

[0056] Further information may be displayed elsewhere on the monitor. In some embodiments, the body region indicator may flash and then change to a solid state once the information is confirmed. For example, if the device is advanced into the stomach and the impedance sensor senses a higher conductivity, the stomach shape may flash green (or otherwise indicate to the user to pause advancement of the device, or to pause before the user or controller begins eating), indicating that the controller has preliminarily determined that the device is in the stomach. The controller may then continue to collect temperature sensor data for several to several seconds. If this data indicates that the device is not likely in the lungs (no fluctuations associated with breathing), the stomach shape may change to a solid green instead of flashing green (or the pause indicator may disappear), allowing the user to begin eating or continue advancing the device.

[0057] Alternatively, if the temperature sensor indicates that there is a temperature fluctuation, the stomach shape may change to orange or red, indicating possible presence of the lungs. Additionally or alternatively, the lungs may turn red or orange in this scenario. The controller may indicate to the user to retract the device and / or prevent the delivery function from being initiated.

[0058] The pause for collecting temperature data may be at least 1 second, at least 3 seconds, at least 5 seconds, at least 7 seconds, at least 10 seconds, at least 15 seconds, etc. The pause may be in the form of an indicator to the user not to advance the device and / or not to initiate feeding through the device. The pause may cause the controller to prevent initiation of feeding through the device until the pause has ended and the stomach has been positively identified and confirmed.

[0059] Other possible indicators that may be shown on a display and / or played audibly and / or felt (such as a vibration) include:

[0060] -Pause

[0061] -pause for x seconds

[0062] - Pause until an indicator (visual, audible, tactile) tells you to move the device forward or backward

[0063] -Move the device back x (cm)

[0064] -Move the device forward x (cm)

[0065] - Move the device back x (cm) and pause

[0066] - Move the device forward x (cm) and pause

[0067] - Move the device back x (cm) and then forward again

[0068] In some embodiments, the indwelling display 1416 and / or other displays are alternatively or additionally located on the feeding tube 1412 and / or on a remote device 1418, such as a cell phone, tablet, computer, server, electronic medical record, etc. In some embodiments, the controller functionality is contained entirely or partially within the remote display. For example, some embodiments of the device may not include a monitor housing 1410, but may include a stand-alone feeding tube 1412 with a display 1416. This smaller display may increase portability and may incorporate all or part of the monitor / controller functionality. Part of the monitor functionality may be incorporated into the remote electronic device 1418. A feeding input line 1414 is also shown. The monitor housing 1410 may include a docking area to which a feeding tube may be docked such that when the feeding tube is docked within the monitor, the feeding tube may operate with the indwelling display 1416 or with the full monitor display contained by the housing 1410.

[0069] Other display areas not shown here may include data views, such as a temperature data view and / or an ECG data view showing graphs of signals from certain types of sensors. Other display areas may include reflux information, including risk, event, management, and contextual (i.e., historical) information and trends.

[0070] The delivery rate may depend on sensed GRV / gastric emptying and may be controlled automatically, semi-automatically, or manually by a controller. Semi-automatic control may involve automatically controlling smaller adjustments but prompting the user for larger adjustments.

[0071] 15A and 15B show an embodiment of a gastric access device that includes tissue sensing electrode(s) 1502 for sensing tissue impedance / conductivity when in contact with tissue. These sensors may be used to identify the location of the LES (lower esophageal sphincter), UES (upper esophageal sphincter), and / or pyloric sphincter or other regions of the anatomy. Sphincter regions tend to have a smaller diameter than the tissue surrounding them, making them easier to identify with a contact sensor. They may be identified by sensing tissue contact with the electrodes of the gastric access device around the circumference of the device. In other words, two or more electrodes may be positioned around the circumference of the device to determine tissue contact between the electrodes (e.g., when the sensor is within a reduced diameter region of the anatomy).

[0072] In some embodiments, the diameter of the device shaft may be larger at the location of the tissue sensing electrodes than in other regions of the device, hi some embodiments, the diameter of the device shaft at the location of the tissue sensing electrodes may be expandable and / or retractable, such as a cage or balloon, to increase tissue contact.

[0073] FIG. 15B shows a cross-sectional view of the device of FIG. 15A. Note that the tissue electrode 1502 may protrude outside the outer shaft 1504 of the device to increase the likelihood that the electrode will contact tissue. In some embodiments, the protruding electrodes may be retractable or may be made to protrude different distances from the shaft of the device. There may be one, two, three, or more electrodes around the circumference of the device at any one or more locations along the shaft. Also shown here is an electrode lead 1506 housed within the outer shaft 1504. The location of the LES, UES, and / or pyloric sphincter can be identified by the level of tissue contact (how many circumferential electrodes are in contact with tissue) as well as the length of the device inside the patient.

[0074] For example, the UES can be identified when the sensor is approximately 15-20 cm inside the body (measured from the incisors). The LES can be identified when the sensor is approximately 30-50 cm inside the body. The pyloric sphincter can be identified when the sensor is approximately 50-100 cm inside the body. These measurement targets can be narrowed by considering the patient's size. Note that different tissue electrodes / sensors may be used along the length of the device shaft to identify different regions of the anatomy. The diameter or distance the tissue electrode protrudes from the shaft can also be used to determine which sphincter the electrode is sensing.

[0075] This embodiment may or may not include impedance / conductance electrodes 1108 as well as temperature sensors 1110. In some embodiments, electrodes 1502 may be used to determine GRV / gastric emptying or device placement in addition to sensing tissue impedance / conductivity.

[0076] Some embodiments of the gastric access device include the ability to avoid reflux events, sense reflux events or device movement, and manage reflux events by, for example, aspirating refluxed material from the patient. The same sensors used for positioning may be used for this, or other sensors may be used.

[0077] 16A, 16B, and 16C show an embodiment of a gastric access device that includes tissue electrode(s) / sensor(s) 1502 and reflux sensor(s) 1602. One or more reflux sensors can be located in a more proximal region of the shaft to sense gastric reflux in the esophagus above the LES. These sensors are designed to detect gastric reflux after the device is placed in a patient. They are positioned so that one or more are present in the esophagus after the device is placed. They may be impedance / conductivity sensing electrodes or may be pH or other sensors. There may be one or more electrodes around the circumference of the shaft of the device, anywhere along the shaft.

[0078] When the reflux sensor is in the presence of reflux fluid, its conductivity increases and its impedance decreases. Because it may be advantageous to avoid contact between the reflux sensor and esophageal tissue, the reflux sensor 1602 may be placed within a recess 1604 in the device's outer shaft. This is shown in cross-section in FIG. 16C. A cross-section of the tissue sensor region is shown in FIG. 16B. Multiple reflux sensors along the length of the device's shaft can help identify the extent of reflux, i.e., how far from the esophagus it is, whether reflux is progressing, regressing, and / or whether there is a risk of aspiration. Alternatively, the reflux sensor may be relatively flush with the outer surface of the device's shaft or may protrude slightly outward therefrom.

[0079] FIG. 17 illustrates the embodiment shown in FIG. 16A with the addition of an expandable member 1702 and a suction tube 1704. A reflux sensor 1706 may be used to identify the presence of reflux, as described above. When reflux is sensed, or when reflux is sensed and determined to be a risk, the controller may expand the expandable member, which may be an inflatable balloon or other mechanism, and apply suction to the suction tube to remove reflux from the esophagus. The reflux sensor can sense when reflux has been removed, and the size of the expandable member can be reduced and suction can be stopped. These actions may be performed manually based on an alert or automatically by the controller.

[0080] Some embodiments may include a suction tube 1704 without an expandable member 1702. In these embodiments, the suction level may need to be controlled to prevent stomach contents from being aspirated into the esophagus. The suction tube can be located anywhere at or above the LES. In some embodiments, the suction tube may be moved along the shaft to precisely localize the suction. This placement of the suction tube may be determined by the level of reflux, which may be determined by signals from multiple reflux sensors along the length of the shaft of the device.

[0081] Figure 18 shows the embodiment shown in Figure 17 in place within the anatomy. A tissue sensor 1502 may aid in placement of the device. For example, a physician can locate the LES, allowing the physician to know when the opening of the device has passed the LES and is therefore in the stomach and in position for feeding. The expandable member 1702 is shown just above the LES, and the reflux sensor 1706 is shown in the esophagus. The suction tube 1704 is shown here further up the esophagus, but may be higher or lower within the esophagus.

[0082] The suction lumen of the suction tube is connected to a suction device 1802. The suction device 1802 may be a pump, a valve that controls wall suction, or another suction mechanism. The suction line 1804 may or may not pass through the hub 510.

[0083] Figure 18 shows a suction tube concentric with the main device shaft of the gastric access device. Figure 19 shows another embodiment in which the suction tube 1902 is next to the main device shaft of the gastric access device or along one side of the device. In some embodiments, the suction tube may be a separate device that can be introduced and removed separately from the gastric access device main shaft. Alternatively, it may be placed through the lumen of the gastric access device or may be part of but external to the shaft of the gastric access device.

[0084] In some embodiments, reflux suction is initiated and / or continued based on a signal from the reflux sensor indicating reflux is present in the esophagus. In some embodiments, the controller / monitor may be programmed to periodically apply a small amount of suction to the suction device to remove any reflux, which may or may not be present, and / or test for reflux. This periodic application of suction may occur whether or not reflux is sensed. The expandable member may or may not be expanded for these periodic suction events. By performing periodic suction events, the system can effectively eliminate reflux risk without relying on detecting reflux. Preferably, these periodically scheduled reflux suction events apply a sufficiently low level of suction so that stomach contents are not aspirated in embodiments where the expandable member is not present or expanded. If reflux is sensed (either in the anatomy or in the suction tubing or elsewhere) or collected during a periodically scheduled reflux suction event, the controller may be programmed to increase or extend the suction event to ensure all reflux is aspirated. The controller may also trigger expansion of the expansion member if the reflux suction event is increased in level or prolonged in suction.

[0085] Embodiments that include periodically scheduled reflux suction events may not include a reflux sensor on the device. However, they may include other reflux sensors to determine whether reflux is being suctioned from the body. For example, a reflux sensor may be present on the outside of the device, in the controller, waste container, suction line, hub, etc. Periodically scheduled reflux suction events may be scheduled every 5 minutes, every 10 minutes, every 30 minutes, every 60 minutes, every 5-30 minutes, every 30-60 minutes, or any other suitable time frame. The schedule may be user-scheduled. The interval may vary depending on past reflux events. For example, scheduled reflux suction events may become more frequent if reflux is detected more than once or twice. This variation may be manual or automatic.

[0086] In some embodiments, a low level of suction can be used continuously or semi-continuously. In these embodiments, the expansion member does not need to be expanded during continuous suction so that the esophagus is not blocked for an extended period of time. This continuous mode can be activated during feeding, all the time, or as a result of one or more reflux events.

[0087] In some embodiments, the expansion member may be expanded to block the esophagus for a longer period of time, essentially acting as an artificial LES to prevent reflux.

[0088] The embodiments shown herein, such as those shown in FIGS. 15-20, may or may not include additional GRV sensors, such as those shown in FIGS. 11A, 11B, 12 and 13.

[0089] FIG. 20 illustrates an embodiment of a gastric access device designed to locate and traverse the pyloric sphincter to enable delivery within a patient's intestine. A tissue sensing sensor 1502 is shown in the region of the pyloric sphincter 2002. The electrodes of the tissue sensing sensor can sense the pyloric sphincter as well as their sensing of the LES. Because these areas of the anatomy are smaller in diameter than the surrounding tissue, the tissue sensing electrodes can sense tissue contact by sensing an increase in conductivity or a decrease in resistance between the electrodes when the electrodes are in direct contact with tissue. This contact can occur between any single or multiple pairs of electrodes located circumferentially around the device shaft. Because more electrodes around the circumference of the device shaft are in contact with tissue within these smaller diameter areas, the tissue contact sensor / electrode signal can identify these areas by a change in the sensor signal as the device passes through this area.

[0090] In some embodiments, placement of the device at or beyond the pyloric sphincter may be identified or confirmed by other methods. These same methods may also be used to place the device within the stomach. For example, a pH sensor may determine whether the access device is in the post-pyloric or other location. Various sensors disclosed herein may be used to pick up specific signatures, such as pH fluctuations, absolute or relative temperature, peristalsis, impedance / conductivity, etc. An ECG sensor may be used to determine an ECG signal that changes as the electrodes on the device move through the anatomy. For example, the ECG signal may change as the device passes the patient's midline. A bright or otherwise detectable light may be used on the device that can be sensed through the skin and identify that the distal end of the device is in the intestine. Electrodes on the device may be used to sense proximity to one another via impedance, conductivity, or other methods, which may indicate when the device is in a tight curve, i.e., when one portion along the length of the device is relatively close to another portion along the length of the device. See, for example, the embodiments disclosed in Figures 24 and 35. A force or pressure sensor may be used to assess the curvature of the device and determine whether it is within a curved portion of the intestine.

[0091] In some embodiments, navigating the gastric access device up to and / or beyond the pyloric sphincter may be aided by implementation of different device tip shapes and / or designs, such as a pigtail tip, a weighted tip, or an articulating tip. The articulating tip may have a circumferential impedance sensor thereon to sense tissue contact on one or more sides of the tip. The tip may be navigated away from tissue contact to locate the pyloric opening. Some embodiments may include a vibrating end or a rotating end to locate the pyloric opening.

[0092] Some embodiments of the system may include the ability to infuse fluid through the lumen of the device, which serves to prevent the distal end of the device from becoming embedded in tissue and also serves to reinforce the device during advancement. The pressure of the fluid exiting the device may be controlled so as not to damage the tissue but high enough to serve its purpose. Fluid may exit the device via a distal-facing opening, one or more side opening(s), and / or other opening configurations.

[0093] Any of these tip shapes and / or techniques may be included within the feeding tube, or within a stylet passing through the lumen of the feeding tube, or adjacent to the feeding tube to guide the feeding tube over the stylet to access the small intestine via the pylorus. The stylet may or may not be removed after placement.

[0094] Some embodiments may include direct visualization, such as with a camera or fiber optics, to determine and / or confirm placement of the device within the desired anatomy.

[0095] Some embodiments may include the ability to distinguish between the esophagus and the trachea by sensing the amount of air / gas drawn into the device when a vacuum is drawn through the lumen of the device. The ability to draw air / gas into the device is greater in the trachea than in the esophagus. To avoid the device contacting tissue when the vacuum is drawn, one or more small puffs of air or fluid may be introduced through the device before the vacuum is drawn. Alternatively or additionally, openings around the circumference of the shaft of the device may be used.

[0096] Some embodiments can use electrodes to measure myoelectric activity, which can be used to aid in placing the device in the desired location.

[0097] Any of the embodiments disclosed herein may automatically aspirate reflux from the patient's esophagus based on detection of reflux or based on a reflux aspiration schedule.

[0098] Sensors incorporated into gastric access devices can collect data continuously, intermittently, on demand, or only at specific times, such as when confirmation of placement is required.

[0099] The devices disclosed herein include a nasogastric tube with sensors configured to aid in placement of the tube in the stomach and prevent accidental placement in the trachea or lungs. These sensors may include a temperature sensor for sensing respiratory variations and an impedance / conductivity sensor for sensing the stomach. These sensors may alternatively include temperature, impedance / conductivity, and ECG. These sensors may alternatively include any two of temperature, impedance / conductivity, pressure, humidity, pH, and ECG. These sensors may alternatively include any three of temperature, impedance / conductivity, pressure, humidity, pH, and ECG.

[0100] An electrogastrogram (EGG) may also be used to identify the location of the gastric access device within the stomach. The EGG sensor may be different from other sensor types or may use the same electrodes as, for example, an ECG sensor and / or an impedance / conductivity sensor.

[0101] In some embodiments, electromagnetic sensors may be used in addition to other sensors for placement.

[0102] Although the embodiments disclosed herein discuss accessing the GI tract and avoiding the trachea / lungs, the same concepts can be used to locate the trachea / lungs and avoid the GI tract.

[0103] FIGS. 21A-21C illustrate an embodiment for measuring / determining intra-abdominal pressure via a feeding tube. FIG. 21A illustrates a gastric access device, or alternatively, a conventional feeding tube within the stomach. FIG. 21B illustrates a column 2102 of air or other fluid being introduced into the lumen of the tube. As the column of fluid is introduced, the controller measures the pressure within the lumen. The pressure increases as the fluid fills the lumen. At the point when a portion of the gas / fluid or bubbles 2104 exit the lumen of the gastric access device / feeding tube, the pressure drops sharply, indicating that the pressure within the column of fluid has exceeded the pressure of the fluid in the stomach. The pressure of the fluid in the stomach is identical to or correlates with the patient's intra-abdominal pressure (IAP). Thus, the controller can derive the patient's IAP by monitoring the pressure of the column of fluid as it is introduced into the lumen of the gastric access device / feeding tube. The fluid may be air or another gas, or may be water or another liquid. The fluid column may be solid or discontinuous. The IAP measurement sequence may be performed by the controller periodically, either before or after feeding. Because the stomach has more fluid in it after a meal, this may be a preferred time to measure IAP. IAP measurements may also be performed manually by physically monitoring blood pressure on a gauge, similar to a blood pressure cuff.

[0104] In some embodiments, a gas bubble similar to gas bubble 2104 may be used to measure pressure fluctuations, which can help confirm placement of the device in either the esophagus or trachea.

[0105] 22A-22C show another embodiment for measuring / determining IAP via a feeding tube. FIG. 22A shows a gastric access device, or alternatively, a conventional feeding tube within the stomach. The stomach may contain air / gas 2202. This embodiment involves removing as much air / gas 2202 as needed by suction. As shown in FIG. 22B, the stomach is filled with liquid or other means. This air / gas reduction step may or may not be necessary to obtain an accurate IAP measurement. Then, as shown in FIG. 22C, a column of fluid (preferably liquid) 2204 is introduced into the lumen of the tube. By measuring the pressure of the column of fluid, an indicator of the fluid pressure within the stomach, and therefore IAP, can be measured. These steps may be performed by a controller, manually, or both.

[0106] FIG. 23 shows another embodiment of a GRV measurement system that can be used to measure / determine IAP. This embodiment includes a bladder 2302, which may be a balloon or other pressure-sensitive bladder. Inflation / deflation of the bladder occurs via a lumen 2304. Lumen 2304 may also be used to monitor the pressure within the balloon / bladder. This pressure is an indicator of IAP. Inflation / deflation and pressure measurements may be performed automatically or on command by a controller. Measurements may be performed automatically periodically and / or before and / or after delivery.

[0107] Some embodiments of the gastric access device may include the ability to test whether the feeding tube is bent or kinked. In one embodiment, the controller can introduce pressurized fluid (gas or liquid) into the lumen of the feeding tube and measure the pressure required for the fluid to flow through the lumen. A baseline pressure may be sensed on the unkinked feeding tube to determine the unkinked pressure range. As the tube bends or kinks, the required pressure increases. The controller can measure and track this pressure over time and determine the condition of the feeding tube based on absolute pressure, relative pressure, change in pressure, or the gradient of change in pressure over time.

[0108] Bends or kinks in the feeding tube may also be measured electronically, for example, by measuring the proximity of the electrodes to each other. If the electrodes are closer to each other than their spacing along the feeding tube, a kink or tight bend is likely present in the tube. This can be done by measuring the impedance and / or conductance between the electrodes. The electrode pairs may be changed by the controller to determine the proximity of the electrodes. Alternatively, the same electrode pairs may be used.

[0109] See, for example, Figures 24 and 25. Figure 24 shows a gastric access device with a pH, temperature, impedance, or other sensor 2402, an opening (for feeding) 2404, and electrodes 2406, including electrodes 1, 2, 3, 4, 5, 6, 7, and 8. 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 feeding tube to determine the conductance / impedance across the electrode pairs. However, different electrode pairs can also be used. For example, electrodes 1 and 6 may be used as a pair. The distance between electrodes 1 and 6 can be determined via conductance / impedance. When the device is relatively straight, the distance between electrodes 1 and 6 is Z. If the distance becomes shorter, such as Z' shown in Figure 25, the controller can either sound an alarm / alert or automatically attempt an untwisting maneuver to attempt to untwist the tube. Alternatively, this condition may indicate that the device is within the patient's intestine. Note that the detection of bending may involve any electrode pair and the pair's relative distance from each other. For example, the conductance / impedance between the original electrode pair may not change in the presence of bending / twisting, but the conductance / impedance between electrode pairs that are further apart may change. The combination may indicate a bending / twisting condition.

[0110] In some embodiments, the bending / twisting of the device may be so extreme that two electrodes on the device touch each other, shorting the signal. This information may be used to assess the twisting.

[0111] In some embodiments, a piezoelectric member can be incorporated into the device to determine the orientation of the device (including whether the device is bent / twisted) by monitoring changes in the electrical properties of the piezoelectric member.

[0112] In some embodiments, one or more strain gauges may be used to assess the twisting / bending of the device.

[0113] In some embodiments, one or more accelerometers may be used to determine the orientation of various portions of the device. In some embodiments, a weighted tip may be used to determine the orientation of the tip of the device.

[0114] In some embodiments, one or more pressure sensors are used for device placement. For example, the pressure exerted on the device in the stomach may be higher than the pressure in the esophagus. In embodiments with two or more pressure sensors, no difference between two pressure readings can indicate one pressure sensor is in the stomach and one pressure sensor is in the esophagus. Two similar pressure readings can indicate that the device is kinked in the esophagus.

[0115] In some embodiments, conductive fluid injection may be used to assess bending / kinking of the device. After placement, conductive fluid can be injected into the patient's mouth. In situations where the device is not bent back onto itself within the anatomy, the electrodes will read increased conductivity signals first by the more proximal electrodes, then progressively more distal electrodes. If the device is bent back onto itself, the distal electrodes may signal increased conductivity in random order before some of the more proximal electrodes. Similarly, the device can perform similar assessments using temperature sensors and hot or cold liquids.

[0116] Some embodiments incorporate automatic air insufflation to reduce twisting of the device. The controller automatically injects a stream or puff of air through the device as it is being inserted. This air or gas serves to stiffen the device and prevent twisting during insertion. This process may occur automatically during the entire insertion process, or only after resistance is perceived, or after the device is a set distance within the patient.

[0117] In some embodiments, alternatively or in addition to using a stylet, pressurized air or fluid may be used within the lumen of the device to stiffen it.

[0118] In some embodiments, the device may be automatically oscillated or rotated during insertion to prevent twisting.

[0119] In some embodiments, the distal tip may have a corkscrew shape and may be rotated during insertion.

[0120] Some embodiments may include a balloon or other expandable member to prevent accidental removal of the device once it is in place. The gastric access device may have a balloon that is inflated against the gastroesophageal junction after insertion into the stomach to prevent back-rolling or inadvertent withdrawal into the esophagus.

[0121] Any of the embodiments that include the ability to determine device bend / torsion may also be used to assess the shape of the device within the anatomy, in other words, these embodiments may be used for device shape modeling in general, in addition to bend / torsion detection.

[0122] Figure 26 illustrates some of the anatomical landmarks that may be used when placing a gastric access device. The entrance 2602 may be the patient's nostril or lips. The respiratory-gastric junction (RGJ) 2604 is the junction of the trachea and esophagus. The lower esophageal sphincter (LES) 2610 is at the lower end of the esophagus before the junction with the stomach. The pylorus 2612 is at the transition between the stomach and the intestine. The trachea 2606 indicates the junction of the trachea with the bronchial branches of the lungs. The bronchus 2608 indicates the estimated maximum depth of incorrect feeding tube insertion. Shown below are some estimated length ranges for infants and adults for various lengths.

[0123] [Table 1]

[0124] Based on these lengths, the gastric access device can be designed to have the correct type of sensor in the appropriate anatomy during placement and ongoing use.

[0125] Figure 27 shows a device similar to that shown in Figure 13. In this embodiment, a temperature sensor 1110, such as a thermocouple, can use the same electrodes as the impedance / conductivity electrodes 1108. ECG and / or other signals can also be obtained from the same electrodes. Figure 13 shows one example embodiment of one embodiment of a gastric access device, but the location and spacing and number of sensors / electrodes may vary. Each electrode can utilize the same or different leads for different functions performed by the electrode.

[0126] Figure 28A shows the gastric access device shown in Figure 27 to a scale showing the approximate lengths of different sections of the anatomy. Dimensions vary greatly with age and individual and may be narrower or wider than this scale, but this diagram provides a visual scale for both the anatomy and the gastric access device.

[0127] Figure 28B shows an example of gastric access device placement in a child. In this example, there are five impedance sensors (Z1-Z5) and two temperature sensors (T1 and T2) at different device locations / insertion depths, providing real-time mapping of device location. Electrode pairs Z3 and Z5 also include a thermocouple bonded to one of the electrodes in each pair of electrodes Z3 and Z5 to measure temperature. Sensed measurements are relayed to and processed by the controller to classify the anatomical location of the device. The device also includes an internal sensor in the feeding / medication lumen, which allows for direct sampling of the enteral formulation being introduced. The expected placement of the gastric access device for feeding is as follows: Z1-Z3 are located within the stomach, Z4 is located 1-4 cm proximal to the lower esophageal sphincter (LES), and Z5 is located in the esophagus, more proximal than Z4. For placement guidance and confirmation, the controller provides continuous visual feedback to the operator regarding the location of the distal portion of the device.

[0128] In some embodiments, it is generally desirable to have one temperature sensor as close as possible to the distal tip of the device, without being so close to the distal tip that it overlies the tissue during advancement. This distal-most temperature sensor aids in device placement. As the device advances, the distal-most temperature sensor senses temperature fluctuations or lower temperatures associated with breathing ambient air while the sensor is above the RGJ. As the device advances further, the temperature fluctuations should plateau, or if the device advances into the esophagus, the average temperature will increase. However, if the device undesirably advances into the trachea, the distal-most temperature sensor will continue to sense temperature fluctuations and / or temperatures lower than body temperature as it advances into the trachea. This undesirable advancement triggers the system's controller to alert the user and instruct them to retract the device.

[0129] In some cases, the gastric access device may undesirably be in the trachea, but the most distal temperature sensor may be above the tissue and therefore not sense temperature fluctuations or temperatures below body temperature. A second, more proximal temperature sensor is placed to sense temperature fluctuations or temperatures below body temperature if the device is misplaced in the trachea. The more proximal temperature sensor is desirably placed along the length of the device so as to advance past the RGJ before the distal end of the device passes too far into the bronchi.

[0130] Although two temperature sensors are shown here, there may be fewer or more temperature sensors along the device. In some embodiments, each electrode on the device is capable of sensing impedance / conductivity, temperature, ECG, and possibly other parameters. The function of the different electrodes may be controlled by a controller. The sensed parameters may alternate throughout placement and use, or the sensed parameters may be related to the size of the patient or the length of the anatomy.

[0131] For example, a gastric access device may include 10 pairs of electrodes. The patient may be a tall adult. Based on the patient's height or other measurements, the electrodes along the device may be assigned appropriate functions so that there are at least a distal-most temperature sensor and a proximal-most temperature sensor that will enable the device to sense temperature fluctuations and / or average temperature within the trachea or esophagus while the device is introduced into the patient. In some embodiments, the proximal temperature sensor is positioned so that it passes through the RGJ before advancing too deeply into the bronchi. In some embodiments, the distal-most temperature sensor is proximal to the distal-most electrode pair. In some embodiments, the distal-most temperature sensor is incorporated into the distal-most electrode pair.

[0132] Additional electrodes may be proximal to the most proximally used electrode. These electrodes may be useful for taller or larger patients, but not for shorter or smaller patients. In this way, the same device can be used for patients of different sizes and anatomies.

[0133] Temperature, impedance / conductance, ECG, pH, and other sensors disclosed herein may also be used along the length of the device to sense any type of placement, including post-pyloric placement. For example, the device may have electrodes along a significant portion of its length, allowing the controller to receive sensor signals from all parts of the anatomy in which the device is located as the device advances or after it has advanced. The controller may create temperature maps, impedance / conductivity maps, ECG maps, pH maps, combined parameter maps, etc., whose signatures can be analyzed to determine the likely location of each electrode within the anatomy. This allows the user to know where the catheter tip is, delivery openings, etc.

[0134] 29A and 29B show details regarding an embodiment using a single electrode for two or more sensors. These figures show an arrangement in which a pair of electrodes can sense both impedance or conductance and temperature. Sharing electrodes in this manner saves cost and space and allows for a smaller device. An impedance / conductance electrode 1108 is shown, as well as a temperature sensor 1110, which in these embodiments is one of the impedance / conductance electrodes that is essentially a conductive (i.e., metallic) band. This can be achieved by connecting the impedance / conductance electrode 1108 to a controller via lead 2902 and the temperature sensor thermocouple to the controller via lead 2904. While these figures show separate pairs of leads for the different sensors, it is envisioned that leads may be shared between sensors in some embodiments.

[0135] The leads generally extend along the length of the device, as shown in Figure 29A. For illustrative purposes, Figure 29B shows an electrical diagram representing these connections, as well as some of the associated functionality of the controller. Lead 2902 connects the metal band or electrode to the impedance / conductivity logic area 2906 of the controller. Lead 2904 connects the metal band or electrode to the temperature logic area 2908 of the controller. These two logic areas are connected to a switch 2910, which allows the controller to switch between measuring conductivity / impedance or temperature using the same electrode or electrodes.

[0136] Switch 2910 may connect other logic / sensing areas such as ECG, pH, etc., which may use overlapping electrodes, as with temperature and conductivity / impedance here. In the case of pH sensing, a reference material is incorporated into the system to determine pH using electrodes. The ECG and pH sensors can use the same leads as the impedance / conductivity sensors.

[0137] In some embodiments, no physical or logical switches are required, and the functionality of the various leads / electrodes is driven by logic within the controller. Sensing two different parameters using the same electrodes can even overlap in time; for example, the controller can simultaneously sense both temperature and impedance from the same electrode. The controller can essentially simultaneously sense temperature, impedance, and ECG, if the sampling rate allows. For example, the sampling rate can be greater than 5 samples / second. Or, for example, the sampling rate can be greater than 10 samples / second. Or, for example, the sampling rate can be greater than 20 samples / second. Or, for example, the sampling rate can be greater than 100 samples / second.

[0138] Another advantage of using a 360 degree or substantially 360 degree conductive band for these types of sensors is that:

[0139] Each impedance / conductivity sensor (typically composed of two electrode rings, but may be composed of one, two, or more electrode rings) attempts to measure the path of minimum impedance or maximum conductivity between the two rings. This means that the impedance / conductivity sensor simultaneously senses 360 degrees around the circumference of the rings. For example, if the two rings of the impedance / conductivity sensor are positioned up against the stomach wall, the stomach wall tissue will only contact one side of the feeding tube and therefore one side of the electrode rings. The sensor will sense the high conductivity / low impedance of this contact, even if most of the circumference of the rings is not in contact with the high conductivity / low impedance environment. In other words, an impedance / conductivity sensor using 360-degree rings is essentially a spot sensor.

[0140] In contrast, each temperature sensor may consist of a thermocouple coupled to a 360-degree electrode or conductive ring. Because of this coupling, the thermocouple essentially senses the average temperature around the ring. In situations where the supply tube, and therefore the temperature sensor, is pressed up against the tissue, the temperature sensor senses the average temperature of the environment surrounding the tissue as well as the remainder of the circumference of the ring. This allows the temperature sensor to sense breathing in the respiratory system even when the supply tube is against the wall of the respiratory system, avoiding false negatives. In other words, a temperature sensor using a 360-degree ring is essentially an environment-average sensor.

[0141] By using the same electrodes for both sensor types, the system can sense both tissue contact (by switching to conductivity / impedance sensing) and the thermal environment (by switching to temperature sensing). The controller may switch back and forth between the two depending on the current need and / or location of any particular sensor.

[0142] The controller may determine impedance by measuring the voltage drop (amplitude of the periodic voltage signal) across the electrode pair when a constant amplitude AC current is applied. For example, the AC current may be 30 kHz, 100 μA peak-to-peak. Temperature measurements can be obtained using a copper / constantan thermocouple (Type T) thermally coupled to one electrode ring. This design solution provides 360-degree sensing to facilitate acquisition of true impedance and temperature measurements, even with intermittent tissue contact or other confounding factors. Sensor locations are designed to accurately classify the anatomical location of the device based on each sensor's measurements of the local environment. Gastric access devices can be of different lengths to allow optimal sensor spacing based on the clinical nose-ear-midumbilicus (NEMU) method, which is commonly used to determine insertion length to ensure optimal final positioning of the sensor within the patient's upper gastrointestinal tract (GI). Impedance and temperature data can be delivered to the controller in real time via a secondary non-fluid-contact lumen. The sensor data may be analyzed by the controller for two different functions: placement (during device insertion or for periodic monitoring of position) and gastric status (to determine GRV gastric emptying during eating, etc.).

[0143] The placement function may use a simultaneous two-part analysis to classify device location: (1) a time series temperature pattern recognition function, and (2) an impedance threshold classifier (ITC) to identify device tip placement within the esophagus, stomach, or respiratory system, or other locations.

[0144] The temperature pattern recognition function can assess the temperature data from sensors T1 and T2 at a rate of approximately 5 Hz to detect airway misplacement through the identification and classification of successive local maxima and minima (LMM). When the temperature pattern recognition function recognizes a pattern of LMMs representing two respiratory cycles (typically occurring within 2-4 seconds in infants and longer in adults), a positive determination of airway misplacement can be determined.

[0145] Concurrently with or interspersed with temperature analysis, the placement function continuously or intermittently assesses impedance measurements along the device. Impedance measurements in the stomach are generally significantly lower than those in the esophagus. In some embodiments, a single threshold of 350 Ω is sufficient to distinguish between the stomach and the esophagus. In some embodiments, the threshold classifier that defines location is based on impedance measurements from at least two of the three distal sensors. This provides a robust approach to ensure proper placement even in the presence of confounding factors, including intermittent tissue contact or air bubbles within the stomach.

[0146] [Table 2]

[0147] Note that although a cutoff of 350Ω is shown here, it may be in the range of approximately 350Ω to 400Ω. Alternatively, the cutoff may be in the range of approximately 350Ω to 450Ω. Alternatively, the cutoff may be in the range of approximately 350Ω to 500Ω. Alternatively, the cutoff may be in the range of approximately 350Ω to 650Ω. Alternatively, the cutoff may be in the range of approximately 300Ω to 400Ω.

[0148] The gastric status function calculates the patient's real-time gastric content composition based on (1) impedance measurements of the patient's empty stomach before any feeding (measurements may be taken using one or more of the most distal electrode pairs), (2) impedance measurements of the compound being delivered (sensed using an internal sensor within the device lumen), (3) real-time average impedance values ​​within the stomach (sensed using one or more of the more distal electrode pairs), and (4) selection of an appropriate calibration curve from a library. Shifts in gastric content composition pattern characteristics may be evaluated over 4-, 8-, 12-, and 24-hour windows using both time series and latent variable trend analysis to provide automated feedback on gastric status. Different status categories may include: 1) feeding optimized; 2) low risk of feeding intolerance (pre-feed if calorie goals are not met); and 3) high risk of feeding intolerance (reduce feeding if clinical signs of feeding intolerance are present).

[0149] Placement and gastric status function outputs are visually displayed on the controller to provide real-time feedback to clinical staff. The reusable, pole-mounted controller includes a user interface display, may be powered by a standard outlet, and may contain an internal battery capable of supporting 12 or more hours of continuous function. For initial device placement, the operator may receive the following notifications: (1) ORANGE ESOPHAGUS: "The distal tip of the device is in the esophagus. Continue advancing." (2) RED LUNGS: "The distal tip of the device has entered the airway. Please withdraw." (3) GREEN STOMACH: "The distal tip of the device is properly placed in the stomach." Once correct gastric placement is achieved, the controller's gastric status function continuously monitors changes in digestion and provides automatic feedback on how best to optimize feeding: 1) feeding optimized; 2) low risk of feeding intolerance (expedite feeding); and 3) high risk of feeding intolerance (reduce feeding).

[0150] In some cases, a user may introduce medication through the feeding lumen of the feeding tube. This medication may be in the form of crushed pills or other bulky substances. The feeding lumen of the feeding tube can often become blocked by the added medication and can be difficult to unblock. An anti-clogging mechanism may be used in conjunction with the gastric access device or any feeding tube to prevent large particles of medication from entering the feeding tube.

[0151] FIG. 30A illustrates a drug introducer accessory that can be used with any feeding tube. Drug crusher 3002 includes a rotating segment 3006 and a sheath 3008. A drug 3004, such as a tablet, is introduced into a cavity within rotating segment 3006. Teeth or another crushing mechanism (not shown) communicate with the cavity. To prevent the drug from exiting the accessory, the sheath can be rotated after the tablet enters the cavity. The two rotating segments are then rotated relative to each other to crush the drug, resulting in particles small enough to enter the feeding lumen of the feeding tube without clogging the feeding tube. The crushing mechanism can be similar to that of a pepper grinder. In some embodiments, the crushing action can be a ratcheting action, similar to a pepper grinder, where the drug is crushed only when the segments are rotated in one direction and not when the segments are rotated in the opposite direction.

[0152] The comminution accessory 3002 is connected to a feeding tube or gastric access device, as shown in FIG. 30B.

[0153] Figure 30C shows another embodiment of an anti-clogging mechanism. This introducer accessory 3010 includes a limiter, filter, or cutter to prevent large chunks of drug from entering the supply tube. The filter may be in the form of a wire mesh or cross 3012, as shown in Figure 30C. The wire filter may be made from 0.003 inch diameter stainless steel wire or the like. Figure 30D shows an embodiment of an introducer accessory 3010 that includes a constriction 3014. The constriction essentially completely prevents drug chunks from entering the supply tube. If the drug chunks in the supply are larger than the diameter of the constriction 3014, they will not be introduced into the supply tube. The constriction 3014 has a diameter smaller than the diameter of the supply lumen of the supply tube.

[0154] Other embodiments of the anti-clogging mechanism may include sharp blades to cut off larger chunks of drug that are forced through the opening.

[0155] The introducer accessory 3010 is connected to a feeding tube or gastric access device, as shown in FIG. 30E.

[0156] The controller of any of the embodiments disclosed herein may include the ability to analyze and / or display contextual data. For example, reflux history may be collected, analyzed, displayed, and used to automatically control the controller. For example, patients with a higher incidence of reflux may require more frequent or continuous suction events. The controller may determine a reflux suction schedule and / or suction level taking into account the extent and / or frequency of reflux events. Contextual reflux information may also determine whether the expandable member is expanded during a suction event. Contextual feedback, GRV, and placement information may also be used in this manner.

[0157] In some embodiments, the gastric access device can sense passive electrical signals generated in the stomach wall using electrodes along the device. These signals can be used to assess gastric health, such as peristalsis.

[0158] GRV / gastric emptying may be tracked by the system over time by introducing an additive element having a measurable parameter, the parameter being at a level different from the level of gastric contents. The parameter level is sensed by a sensor on the feeding tube, and changes are analyzed over time to determine GRV / gastric emptying. For example, a fluid having a lower conductivity than that of the gastric contents (e.g., feed) may be introduced into the stomach as a bolus, as multiple boluses, or continuously or over time. The sensor along the gastric access device may be a conductivity / impedance sensor, which can sense the conductivity / impedance along the device over time to determine GRV / gastric emptying. Other parameters, such as temperature, pH, chemical content, and optical parameters, may also be used.

[0159] In some embodiments, a sensor also resides inside the additive element delivery lumen of the device, which may be the feeding lumen or a separate lumen. The sensor(s) may measure the additive parameter before the additive is added to the stomach so that the additive parameter level is known before the additive is introduced into the stomach. This allows the controller to more accurately determine GRV / gastric emptying. For example, in the conductivity / impedance example above, a pair of electrodes may reside inside the feeding lumen of the device and measure the conductivity / impedance of the additive (which may be the feed) just before the additive enters the stomach. The electrodes may be flush with the inner surface of the feeding lumen. This measurement may be incorporated into the GRV / gastric emptying analysis so that the change in the parameter due to stomach contents can be accurately determined. This inner lumen sensor may be considered a "calibration sensor."

[0160] In some embodiments, the controller switches to a delivery mode to monitor the GRV after sensing a delivery or liquid in the delivery lumen of the device.

[0161] When the gastric access device is in feeding mode, the gastric access device can place itself in different states, such as feeding optimization, low risk of feeding intolerance (pre-feeding if calorie goal is not achieved), and 3) high risk of feeding intolerance (reduced feeding if clinical signs of intolerance exist). In some embodiments, the gastric access device may be capable of measuring the % concentration of food to gastric fluid in the stomach based on measuring parameters of the additive (in this case, food) over time. These embodiments may include a calibration sensor.

[0162] In some embodiments, gastrointestinal health can be assessed by providing a bolus of an additive element and tracking GRV / gastric emptying immediately after the bolus. The GRV / gastric emptying profile can be used to determine the health of a particular patient by comparing the profile to profiles of healthy and unhealthy individuals and / or populations. For example, an additive bolus containing a high level of glucose can be used and GRV / gastric emptying monitored after the bolus. Other indicators, such as blood glucose levels, can also be monitored.

[0163] In some embodiments, GRV (or gastric emptying) is monitored over time, and feeding is stopped, started, increased, or decreased as a result of changes in GRV or GRV threshold over time. For example, if GRV is decreasing, this may be an indicator that the patient can tolerate more food, and feeding rate and / or volume may be increased or initiated. If GRV is increasing, this may be an indicator that the patient is not tolerating the feeding rate, and feeding rate and / or volume may be decreased or stopped. Feeding rate and / or volume may be increased, decreased, stopped, or started based on GRV trend and / or GRV threshold.

[0164] The delivery rate and / or volume may be varied by varying the speed of the delivery pump, by closing the delivery source, or by opening the delivery source, either intermittently, or over a period of time, or until the user starts or stops the delivery again. Closing or opening the food source can be done via a valve in-line with the delivery line of the food.

[0165] In this way, an optimal feeding rate and / or volume can be achieved. The feeding rate target may be a feeding rate at which the GRV remains relatively stable and does not appreciably increase or decrease over time. This rate may be different at different times of the day, when the patient is awake, asleep, etc. The feeding rate may be determined by the change in GRV at any given time. In this way, food tolerance may be determined specifically for each patient and for a single patient at different times and in different circumstances.

[0166] Estimating the feeding rate to achieve a stable or constant GRV over time can be accomplished by measuring the impedance of an empty stomach as well as knowing or measuring the impedance of the formulation. For example, if the measured impedance on an empty stomach is about 200-300 ohms and the impedance of the introduced formula is 800 ohms, the target impedance can be the approximate average between these two numbers, or about 500-550 ohms. The target impedance can also be lower or higher than the average between the two measurements.

[0167] In situations where bolus feeding, or intermittent feeding, or even steady feeding via a peristaltic pump is used, the impedance in the stomach may oscillate or fluctuate during feeding. In these situations, the target impedance for achieving a stable GRV over time may have upper and lower limits that achieve a stable GRV averaged over a period of time.

[0168] The target impedance may need to be adjusted based on the water consumed.

[0169] In some embodiments, the patient may be intentionally placed in a fasting state over time. The system can be recalibrated to match the impedance (and potentially temperature) to the fasting state, which may change over time due to biofilm buildup or other factors. This new fasting state impedance (and / or temperature) reading can be used to determine GRV (or core body temperature).

[0170] In some embodiments, the type of feed may be changed based on monitoring of GRV or other parameters. For example, multiple food reservoirs may be accessible by the system. The food reservoirs may differ in terms of protein, fat, calorie, and / or carbohydrate content / density / ratio. A patient may tolerate certain types of food better than others, or may tolerate different types of food at different times of the day, or while asleep, awake, etc. For example, if GRV is increasing over time, the system may switch to a feed lower in fat and / or protein to potentially increase digestion rate. Changing feed type can be used separately or in conjunction with changing feed rate as described above.

[0171] In some embodiments, a fourth component, such as water or another liquid, may be adjustable in the feed. This fourth component may be capable of adjusting the impedance / conductivity of the feed as well as the temperature of the feed. For example, at least four components, namely, fat, carbohydrate, protein, and liquid, may be controlled in the feed, potentially using separate reservoirs. The liquid may be non-nutritive or nutritive. In some embodiments, the amount or ratio of liquid components delivered in the feed may be determined by urine sodium concentration, blood sodium concentration, or other factors. In some embodiments, the amount or ratio of carbohydrates delivered in the feed may be determined based on urine glucose levels, blood glucose levels, urine ketone levels, or other factors.

[0172] In some embodiments, a proprietary pump is integrated into the system with a known volumetric delivery rate. In some embodiments, volumetric delivery rates from other third-party pumps are entered and / or stored in the memory of the system's controller so that the supply delivery rate is accurate.

[0173] In some embodiments, a bolus of feed is used to determine gastric emptying / GRV. The bolus may be a known volume with a known indicator parameter value. Changes in the measured indicator parameters (conductivity, pH, temperature, etc.) over the following minutes allow the controller to obtain an accurate measurement of GRV based on these changes, i.e., the magnitude of the change as well as the change over time, the shape of the curve representing the change over time, etc.

[0174] In any of the embodiments disclosed herein, the controller may slow or stop delivery and may provide an alert when backflow is detected, the GRV increases or exceeds a threshold, or the device moves from its appropriate location.

[0175] In some embodiments, the temperature measured by a temperature sensor along the device is used for one or more purposes. The temperature reading may be used to determine when a feed is administered through the feeding tube. The feed is generally at room temperature, a temperature lower than the subject's body, and therefore the temperature sensor detects a decrease in temperature after a bolus of feed is administered. The temperature sensor may also detect a temperature lower than body temperature over time during a constant feed. Fluctuations in temperature readings may be associated with feeding events and used to distinguish feeding events from feeding tube displacement events, as determined by an impedance / conductivity sensor. For example, an impedance sensor may sense an increase in impedance either when the feeding tube is displaced or when a bolus is administered through the feeding tube. Readings from the temperature sensor can distinguish between the two conditions: the temperature is reduced during a feeding event and is generally not reduced, or reduced to a lesser extent, during a displacement event.

[0176] Some embodiments may include the ability to "ignore" temperature changes during a eating event for the purposes of measuring a patient's temperature. For example, temperature readings may be suspended immediately after a eating event. This may be done automatically based on a detected sudden drop in temperature associated with the eating event, or by the user inputting the eating event into the controller, for example, by pressing an on-screen button labeled "Simulated Eating." The suspension may last for a fixed period of time, e.g., about five minutes, or may continue until the user presses an "End" button, or until the controller determines that the temperature readings are sufficiently close to where they were before the eating event, based on the actual temperature measured, the slope of the temperature curve over time, or a different analysis. Some embodiments may account for offsets in the measured temperature due to continued eating when determining body temperature. Changes in impedance / conductivity readings on various sensors may also be incorporated into these analyses.

[0177] Some embodiments may incorporate a pause in delivery to determine core body temperature to minimize the effect of delivery temperature on core body temperature readings. For example, the controller may control the pump to pause delivery for a preset, random, or manually set period long enough for the temperature sensor to sense core body temperature and not be affected by the added delivery temperature. This period may be about 5 minutes, or about 10 minutes, or some other time frame. Alternatively or additionally, the controller may sense stabilization of the temperature curve after delivery is stopped to determine that the temperature sensor is sensing core body temperature and that the sensed temperature is no longer affected by the delivery temperature.

[0178] Some embodiments include multiple temperature sensors along the length of the device. The change in temperature due to added feed may be different at different times as sensed by different temperature sensors along the length of the device. For example, a distal temperature sensor (further inside the stomach) may take longer to recover to body temperature than a more proximal temperature sensor. This difference may also be factored into any analysis performed by the controller to determine core body temperature, eating discrimination, device removal, etc.

[0179] FIG. 31 shows an example of a gastric access device, showing potential locations for electrode pairs (impedance / conductivity sensors) and temperature sensors. A feeding tube with distal tip 3118, opening 3120, electrode pair 3110, electrode pair 3108, electrode pair 3106, electrode pair 3104, electrode pair 3102, temperature sensor 3112, temperature sensor 3114, and temperature sensor 3116 are shown, along with the distance from the distal tip 3118. Different distances may be contemplated. Electrode pairs 3110, 3108, 3106 and temperature sensors 3112 and 3114 are designed to reside in the stomach when the device is properly positioned for gastric feeding. Electrode pairs 3104, 3102 and temperature sensor 3116 are designed to reside in the esophagus when the device is properly positioned for gastric feeding. Note that temperature sensors 3112 and 3114 are on different sides of the feeding tube so that they can be used to sense respiratory temperature fluctuations to determine device placement. Having the temperature sensors on different sides of the feeding tube prevents both from pressing against the tissue during or after placement.

[0180] Some embodiments of the gastric access device include the ability to place the device and / or feeding tube in the small intestine for feeding. This involves navigating the device beyond the pylorus. The device's controller has the ability to identify whether the device is post-pyloric or folded back on itself in the stomach. The device's controller can analyze signals from sensors along the device and identify different signals or signatures for these two situations, as well as other situations. For example, the description associated with FIGS. 24 and 25 describes the system's ability to identify when the device is folded back on itself. In addition, signals from various sensors along the device produce different signatures in different parts of the anatomy. The combination of these different signals, along with the depth of the device within the anatomy, may be used to reliably identify where the device is within the anatomy and whether it is kinked or folded back on itself.

[0181] FIG. 32 shows a graph illustrating signature signals from various sensors on a gastric access device as the device is advanced and retracted through the digestive system. As the device advances through the esophagus and into the stomach, the impedance signals from the more distal electrode pairs are very low and relatively flat. However, the impedance signals from the more proximal electrode pairs exhibit significant amplitude oscillations, likely due to peristalsis. This combination of signals from the various electrode pairs or sensors is used by the controller as a signature to identify where the device is located within the anatomy, along with the distance it has advanced into the digestive system. For example, the signature as the device passes from the stomach through the pylorus and into the small intestine is shown here as different from the stomach signature, with slightly higher impedance readings from the distal two electrode pairs and less variation in the signals from the more proximal electrode pairs. The signature depends on electrode / sensor placement as well as other factors and may differ for different gastric access device configurations and designs.

[0182] Note that the signature may identify other events in addition to device location, including water consumption, feeding events, reflux events, peristalsis, GRV, digestion rate, digestive health, device migration, device bending, device failure, etc.

[0183] Some embodiments of the gastric access device can monitor core body temperature, eliminating the need for an esophageal temperature probe. The temperature sensed by a standard esophageal temperature probe can vary significantly depending on placement. Temperature can be affected by the temperature of the air in the lungs when the probe is proximal to the lungs. The gastric access devices disclosed herein can be placed more consistently and deeper within the anatomy to obtain more consistent and accurate core body temperatures. The gastric access device controller can account for temperature effects from added formulations to achieve a true core body temperature by ignoring the temperature sensed during a feeding event or by accounting for the impact of the feeding event on the measured temperature. This correction can be achieved automatically by pausing core temperature data collection during feeding or by using a correction factor to account for temperature changes caused by feeding. Alternatively, this correction may be achieved by manually pausing temperature sensing during a feeding event. Core temperature can be measured using a temperature sensor located just above the LES, at the LES, or just below the LES to avoid impact of the feeding event on the reading. The device can use signals from temperature sensors at two or more locations along the device. The gastric access system may also have an internal temperature sensor to measure the temperature of the compound passing through the feeding tube to account for the compound's effect on core body temperature.

[0184] In some embodiments of the gastric access device, the device can detect when the patient is swallowing. This may be done by a controller monitoring the propagation of an impedance signal from a more proximal sensor to a more distal sensor in the device. As the patient swallows, tissue first contacts the more proximal sensor and then propagates to the more distal sensor. This tissue contact changes the impedance, and the propagation of the signal through the sensors can be identified as a signature signal indicative of swallowing. This signature can be used to monitor swallowing during or after the device is in place. For example, in some cases, the patient is asked to sip water while the device is in place. Monitoring whether the device is detecting the patient swallowing can help determine whether the device is properly placed. It can also assess the patient's swallowing health.

[0185] Whether the patient is awake or unconscious can affect the movement of the gastric access device through the esophagus and stomach during and after placement. When the patient is awake, the device may move more within the esophagus, and as a result, temperature readings may be more variable than in an unconscious patient. In embodiments where temperature readings are collected to detect respiratory variations and therefore whether the device has moved closer to the lungs, the threshold for variation may be different for conscious and unconscious patients. For example, the range of acceptable or "no movement" temperature variations may be greater in conscious patients than in unconscious patients.

[0186] In some embodiments, the patient's angle or position may be considered or determined to obtain the most accurate measurement of GRV. For example, the head angle may be input into or sensed by the system to take the patient angle into account. In some embodiments, the patient is placed in a left-side current position or other position to obtain a more accurate reading or reference reading.

[0187] In some embodiments, external electrodes (on the abdominal skin surface) may be used in conjunction with electrodes on the gastric access device inside the digestive system monitor to assess gastric contractions.

[0188] Any of the embodiments of the gastric access device disclosed herein may incorporate a stylet or guidewire instead of, or in addition to, a feeding tube. The stylet or guidewire may be used through a lumen of the feeding tube, including the feeding lumen or a different lumen, or may be used along the feeding tube. In embodiments in which a stylet is used along the feeding tube, the feeding tube may include one or more external guides along its length. For example, the feeding tube may have a loop or ring near its distal tip to hold the guidewire / stylet near the distal tip of the feeding tube during placement. This is similar to the "rapid exchange" designs used with angioplasty catheters and guidewires.

[0189] Any of the embodiments disclosed herein may be used in other applications, such as any application in which a body cavity is accessed. For example, the technology may be applied to vascular catheters, urinary catheters, cardiac catheters, other catheters, peritoneal access devices, endotracheal tubes, endotracheal access devices, etc.

[0190] Any of the features in any of the embodiments disclosed herein may be combined with any of the other features and used in any of the embodiments disclosed herein.

[0191] Data Processing System Example Figure 33 is a block diagram of a data processing system that may be used with any embodiment of the present invention. For example, system 3300 may be used as part of the controller / monitor disclosed herein. Note that while Figure 33 illustrates various components of a computer system, it is not intended to represent any particular architecture or manner of interconnecting the components, as such details are not germane to the present invention. It is also 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.

[0192] 33, computer system 3300, which is in the form of a data processing system, includes a bus or interconnect 3302 coupled to one or more microprocessors 3303 and ROM 3307, volatile RAM 3305, and non-volatile memory 3306. Microprocessor 3303 is coupled to cache memory 3304. Bus 3302 interconnects these various components together and also interconnects these components 3303, 3307, 3305, and 3306 to display controllers and display devices 3308, and input / output (I / O) devices 3310, which may be a mouse, keyboard, modem, network interface, printer, and other devices well known in the art.

[0193] Typically, input / output devices 3310 are coupled to the system via an input / output controller 3309. Volatile RAM 3305 is typically implemented as dynamic RAM (DRAM), which requires continuous power to refresh or maintain data in memory. Non-volatile memory 3306 is typically a magnetic hard drive, magneto-optical drive, optical drive, or DVDRAM, or other type of memory system that retains data even after power is removed from the system. Typically, non-volatile memory is also random access memory, although this is not required.

[0194] While Figure 33 illustrates the non-volatile memory as a local device directly coupled to the remaining components in the data processing system, the present invention may utilize a non-network interface that is remote from the system, such as a network storage device coupled to the data processing system through a volatile memory such as a modem or Ethernet interface. Bus 3302 may include one or more buses connected to each other through various bridges, controllers, and / or adapters, as is well known in the art. In one embodiment, I / O controller 3309 includes a Universal Serial Bus (USB) adapter for controlling USB peripherals. Alternatively, I / O controller 3309 may include an IEEE-1394 adapter, also known as a FireWire adapter, for controlling FireWire devices.

[0195] 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 means 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.

[0196] It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. As is apparent from the above description, unless otherwise indicated, throughout this description, descriptions utilizing terms such as those set forth in the claims that follow will be understood to refer to the actions and processes of a computer system or similar electronic computing device that manipulate and convert data represented as physical (electronic) quantities in the computer system's registers and memory into other data that are similarly represented as physical quantities in the computer system's memory or registers or other such information storage, transmission, or display device.

[0197] The techniques shown in the figures may be implemented using code and data stored and executed on one or more electronic devices that use computer-readable media, such as 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 transmission media (e.g., electrical, optical, acoustic, or other forms of propagated signals, such as carrier waves, infrared signals, digital signals, etc.) to store and communicate (internally and / or with other electronic devices over a network) the code and data.

[0198] The processes or methods illustrated in the foregoing figures may be performed by processing logic comprising hardware (e.g., circuitry, dedicated logic, etc.), firmware, software (e.g., embodied on a non-transitory computer-readable medium), or a combination of both. While the processes or methods are described above with some sequential operations, it should be understood that some of the described operations may occur in a different order. Furthermore, some operations may be performed in parallel rather than sequentially.

[0199] All embodiments disclosed herein may incorporate features from other embodiments disclosed herein.

Claims

1. 1. A supply system comprising: a gastric access device having a length; one or more sensors positioned along the length; a controller in communication with the one or more sensors, the controller configured to receive signals from the one or more sensors related to parameters of fluid in the stomach of the subject; The controller is further configured to determine a gastric residual volume (GRV) based on the signal and to control the rate at which a feed or formulation is introduced into the stomach so that the GRV is maintained at a stable level.

2. The system of claim 1 , wherein the one or more sensors include an impedance sensor or a conductivity sensor.

3. The system of claim 1 , wherein the parameters of the fluid in the stomach are modifiable through the introduction of additives into the stomach.

4. The system of claim 3 , wherein the additive comprises a quantity of a feed or a formulation.

5. The system of claim 1 , wherein the parameter comprises an impedance or a conductivity of the fluid in the stomach.

6. 10. The system of claim 1, wherein the controller is configured to control the rate at which the feed or formulation is introduced such that the GRV is maintained below a predetermined upper limit.

7. 7. The system of claim 6, wherein the controller is configured to control the rate at which the feed or formulation is introduced such that the GRV is maintained above a predetermined lower limit.

8. The system of claim 1 , wherein the one or more sensors are configured to measure backflow of the fluid.

9. The system of claim 1 , further comprising one or more additional sensors positioned along the length and configured to measure backflow of the fluid.

10. The system of claim 8 , wherein the controller is further configured to reduce the velocity when backflow of the fluid is detected.

11. The system of claim 1 further comprising one or more temperature sensors positioned along the length.

12. The system of claim 11 , wherein the one or more temperature sensors are positionable along the length to sense a core body temperature of the subject.

13. 12. The system of claim 11, wherein the controller is further configured to start or stop the rate at which the feed or formulation is introduced based on the temperature received from the one or more temperature sensors.

14. The system of claim 1 , further comprising a temperature sensor in communication with the controller for measuring the subject's core body temperature.

15. 15. The system of claim 14, wherein the controller is further configured to pause or stop the introduction of the feeding into the stomach when the temperature sensor measures the core body temperature of the subject.

16. 1. A method of managing delivery of a feed or formulation into the stomach of a subject, comprising: contacting fluid within the subject's stomach via one or more sensors positioned along a length of the gastric access device; receiving a signal from the one or more sensors to a controller in communication with the one or more sensors, the signal related to a parameter of the fluid; determining gastric residual volume (GRV) based on the signal; and controlling the rate at which the feed or compound is introduced into the stomach so that the GRV is maintained at a constant level.

17. 17. The method of claim 16, wherein contacting the fluid comprises contacting the fluid with one or more impedance or conductivity sensors.

18. The method of claim 16 , wherein receiving the signal comprises receiving an impedance or conductivity signal into the controller.

19. 17. The method of claim 16, wherein controlling the rate comprises controlling the rate at which the feed or formulation is introduced such that the GRV is maintained below a predetermined upper limit.

20. 20. The method of claim 19, wherein controlling the rate comprises controlling the rate at which the feed or formulation is introduced such that the GRV is maintained above a predetermined lower limit.

21. The method of claim 16 , further comprising measuring backflow of the fluid via the one or more sensors.

22. 17. The method of claim 16, further comprising measuring backflow of the fluid via one or more additional sensors positioned along the length.

23. The method of claim 16 , wherein the controller is further configured to reduce the velocity when backflow of the fluid is detected.

24. The method of claim 16 , wherein receiving the signal further comprises receiving a temperature from one or more temperature sensors positioned along the length.

25. 25. The method of claim 24, wherein receiving the temperature comprises receiving a core body temperature of the subject.

26. 25. The method of claim 24, further comprising starting or stopping the rate of the feed or formulation being introduced based on the temperature received from the one or more temperature sensors.

27. 25. The method of claim 24, further comprising pausing or stopping the feeding from being introduced into the stomach while the one or more temperature sensors are measuring the subject's core body temperature.

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