Feeding tube system placed inside subject's body

Abstract

To provide apparatus for accessing and monitoring the gastrointestinal tract.SOLUTION: A feeding tube system according to one aspect may generally comprise a gastric access device having a longitudinal portion, a controller in communication with the gastric access device, one or more impedance or conductivity sensors positioned along the longitudinal portion, and one or more temperature sensors positioned along the longitudinal portion. The controller may be configured to receive a first signal associated with the impedance or conductivity sensors and a second signal associated with respiration, and to determine whether placement of the gastric access device is within the stomach of a subject.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to the placement / monitoring of feeding tubes as well as gastric volume measurement, gastric emptying, and gastric reflux detection and management. 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]

[0002] Enteral nutrition is provided through a feeding tube when a patient is unable to take nutrition by mouth, cannot swallow safely, or to provide supplemental nutrition.

[0003] Placing a gastric tube (also referred to here as a nasogastric tube or feeding tube) also presents challenges. Complications and even death can occur if the NG tube is accidentally placed in the trachea instead of the esophagus. Solutions are also needed to accurately place the NG tube in the gastrointestinal tract (i.e., esophagus, stomach, or intestines) rather than the trachea or lungs.

[0004] It is also important to understand the patient's nutritional status to prevent under-nutrition or over-nutrition. As used herein, the term "GRV" refers to gastric residual volume, gastric emptying, gastric residual food, gastric motility, or gastric status. Summary of the Invention [Problem to be solved by the invention]

[0005] Preventing, identifying, and managing gastric reflux is also important with enteral feeding, as reflux can enter the lungs and cause serious complications. [Means for solving the problem]

[0006] Disclosed herein are embodiments of gastric access devices that improve the ability to confidently access the GI tract and avoid inadvertent entry into a patient's trachea / lungs. The embodiments include one or more sensor types to determine whether the device is in the GI tract or the trachea / lungs. Some sensor types positively identify the GI (gastrointestinal) tract, such as impedance / conductivity sensors, pH sensors, ECG (electrocardiogram) sensors, and pressure sensors. Other sensor types positively identify the trachea / lungs, such as temperature sensors, humidity sensors, O2 sensors, CO2 sensors, flow sensors, acoustic sensors, and pressure sensors. Some of these sensors identify both. To properly position the device in the GI tract (or trachea / lungs), a combination of sensors can be used, including at least one sensor that positively identifies the GI tract and at least one sensor that positively identifies the trachea / lungs. Alternatively, two different sensor types that positively identify the GI tract can be used to properly position the device. Alternatively, two different sensor types that positively identify the trachea or lungs can be used to properly position the device.

[0007] In some embodiments, only one sensor type is required to properly position the device. In some embodiments, two sensor types are available to properly position the device. In some embodiments, three sensor types are available to properly position the device. Not all available sensor types are available for all patients in all environments.

[0008] One or more of any sensor type can be used along the length of the gastric access device. In some embodiments, two or more sensors are positioned on or along the gastric access device so that at least one sensor is in a functional position. For example, two or more temperature sensors can be positioned along the gastric access device so that at least one temperature sensor is in a position to measure the surrounding fluid and not impinge on tissue as the gastric access device advances. For example, two or more temperature sensors can be positioned at multiple locations around the circumference of the device. Alternatively, or in addition, two or more temperature sensors can be positioned at two or more locations along the length of the device.

[0009] The device monitor / controller may analyze signals from one or more types of sensors to determine the device's location. Some types of signals may be more reliable than others and may be prioritized over others. Some types of signals may take longer to analyze, may be corroborative of previous signals, or may not be corroborative. The monitor may receive signals from sensors continuously, intermittently, or on an as-needed basis. Some types of signals may be received and analyzed essentially in real time, while others may take longer to receive and analyze.

[0010] Some embodiments of the gastric access device include the ability to monitor gastric volume or gastric emptying, and in some embodiments, the ability to control the delivery rate and / or delivery amount based on gastric volume or gastric emptying.

[0011] Some embodiments of the gastric access device include preventing, identifying and / or managing gastric reflux.

[0012] In some embodiments, sensor types can also be used for patient monitoring. For example, a temperature sensor can be used to determine the location of the device and to monitor the patient's temperature once the device is placed. An impedance / conductivity sensor can be used to determine the location of the device, check for reflux, and / or monitor gastric residual volume and emptying over time after the device is placed. An ECG sensor can be used during device placement and to monitor the patient's ECG after the device is placed. The ECG sensor, impedance / conductivity sensor, and / or other sensors can use the same or different electrodes.

[0013] In one embodiment, a feeding tube system generally includes a gastric access device having a longitudinal portion, a controller in communication with the gastric access device, and one or more impedance or conductivity sensors disposed along the longitudinal portion, with at least one impedance or conductivity sensor disposed at or proximate to a distal end of the longitudinal portion. Each of the one or more impedance or conductivity sensors is in communication with the controller, which is configured to receive a first signal and verify that the first signal is indicative of an impedance or conductivity level of a fluid within the subject's body in contact with the one or more impedance or conductivity sensors. Additionally, one or more temperature sensors may be disposed along the longitudinal portion and in communication with the controller, which is further configured to receive a second signal and verify that the second signal is associated with respiration and indicative of a temperature level of an environment within the subject's body in contact with the one or more temperature sensors. The controller may further be configured to receive the first and second signals and determine whether the gastric access device is within the subject's stomach.

[0014] In one embodiment, a method of placing a device within a subject's stomach may generally include sensing an impedance or conductivity level of a fluid within the subject's body with one or more impedance or conductivity sensors positioned along a length of the gastric access device as the gastric access device contacts the fluid as it advances within the subject's body. Additionally, the method may include sensing a temperature level of an environment within the subject's body associated with respiration with one or more temperature sensors positioned along the length, receiving a first signal from the one or more impedance or conductivity sensors and a second signal from the one or more temperature sensors into a controller in communication with the gastric access device, and determining, by the controller, when the first signal is indicative of fluid within the stomach and the second signal is indicative of the absence of a temperature signal of the environment within the subject's body associated with respiration.

[0015] In another embodiment, the feeding tube system may generally include a gastric access device having a longitudinal portion, a controller in communication with the gastric access device, and one or more impedance or conductivity sensors disposed along the longitudinal portion, with at least one impedance or conductivity sensor disposed at or proximate to the distal end of the longitudinal portion. Each of the one or more impedance or conductivity sensors is in communication with the controller, the controller configured to receive a first signal and confirm that the first signal is indicative of an impedance or conductivity level of an environment within the subject's body in contact with the one or more impedance or conductivity sensors. Additionally, one or more temperature sensors are disposed along the longitudinal portion and in communication with the controller, the controller further configured to receive a second signal and confirm that the second signal is indicative of a temperature level within the subject's body associated with respiration in the region in contact with the one or more temperature sensors. The controller may further be configured to indicate pausing advancement of the gastric access device into the subject's body until the second signal indicates the absence of a temperature level within the region associated with respiration.

[0016] In another embodiment, a method for placing a device in a subject's stomach generally includes detecting an impedance or conductivity level of an environment within the subject's body using one or more impedance or conductivity sensors positioned along a longitudinal portion of the gastric access device as the gastric access device contacts fluid as it advances within the subject's body, and detecting a temperature level within the subject's body in a region associated with respiration using one or more temperature sensors positioned along the longitudinal portion. Additionally, the method may include receiving a first signal from the one or more impedance or conductivity sensors and a second signal from the one or more temperature sensors into a controller in communication with the gastric access device, and pausing advancement of the gastric access device into the subject until the second signal indicates an absence of a temperature level in the region associated with respiration. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 illustrates a gastric access device according to one embodiment at a location in human anatomy. [Figure 2] FIG. 2 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] FIG. 3 is a graph showing measurements from a gastric access device equipped with two temperature sensors. [Figure 4] FIG. 4 is a graph showing measurements from a gastric access device equipped with two temperature sensors. [Figure 5] FIG. 5 illustrates how the gastric access device passes through the trachea and into the lungs. [Figure 6] FIG. 6 illustrates a gastric access device placed in a patient's stomach. [Figure 7] FIG. 7 is a flow chart illustrating the functionality of a controller communicating with a gastric access device including one or more impedance / conductivity sensors and one or more temperature sensors. [Figure 8] FIG. 8 illustrates an embodiment of the feeding tube of the gastric access device when the sensor is approaching the heart. [Figure 9] FIG. 9 illustrates a gastric access device according to one embodiment incorporating an ECG sensor in a nasal, nostril, mouth or facial patch. [Figure 10] FIG. 10 is a flow chart illustrating the functionality of a controller communicating with a gastric access device including one or more impedance / conductivity sensors and one or more ECG sensors. [Figure 11AB] 11A-11B illustrate some embodiments of gastric access devices. [Figure 12] FIG. 12 illustrates several embodiments of a gastric access device. [Figure 13] FIG. 13 illustrates several embodiments of a gastric access device. [Figure 14] FIG. 14 illustrates details of a monitor according to some embodiments. [Figure 15A] FIG. 15A illustrates a gastric access device according to one embodiment including one or more tissue sensing electrodes for sensing tissue impedance / conductivity. [Figure 15B] FIG. 15B illustrates a gastric access device according to one embodiment including one or more tissue sensing electrodes for sensing tissue impedance / conductivity. [Figure 16A] FIG. 16A illustrates a gastric access device according to one embodiment including one or more tissue electrodes / one or more sensors and one or more reflux sensors. [Figure 16B] FIG. 16B illustrates a gastric access device according to one embodiment including one or more tissue electrodes / one or more sensors and one or more reflux sensors. [Figure 16C] FIG. 16C illustrates a gastric access device according to one embodiment including one or more tissue electrodes / one or more sensors and one or more reflux sensors. [Figure 17]FIG. 17 shows the embodiment shown in FIG. 16A with the addition of an expandable member and suction tube. [Figure 18] FIG. 18 shows the embodiment shown in FIG. 17 in anatomical placement. [Figure 19] FIG. 19 illustrates an embodiment in which the suction tube is located next to the main device shaft of the gastric access device. [Figure 20] FIG. 20 illustrates a gastric access device configured to locate and traverse the pyloric sphincter to allow nutritional delivery within a patient's intestine, according to one embodiment. [Figure 21A] FIG. 21A illustrates one embodiment for measuring / determining intraperitoneal pressure via a feeding tube. [Figure 21B] FIG. 21B illustrates one embodiment for measuring / determining intraperitoneal pressure via a feeding tube. [Figure 21C] FIG. 21C illustrates one embodiment for measuring / determining intraperitoneal pressure via a feeding tube. [Figure 22A] FIG. 22A illustrates one embodiment for measuring / determining IAP (intra-abdominal pressure) via a feeding tube. [Figure 22B] FIG. 22B illustrates one embodiment for measuring / determining IAP (intra-abdominal pressure) via a feeding tube. [Figure 22C] FIG. 22C illustrates one embodiment for measuring / determining IAP (intra-abdominal pressure) via a feeding tube. [Figure 23] FIG. 23 illustrates another embodiment of a gastric access device system that can be used to measure / determine IAP. [Figure 24] FIG. 24 illustrates a gastric access device according to one embodiment that can be used to detect bending and / or kinking of the gastric access device. [Figure 25] FIG. 25 illustrates a gastric access device according to one embodiment that can be used to detect bending and / or kinking of the gastric access device. [Figure 26]FIG. 26 illustrates some of the anatomical landmarks used in placing a gastric access device. [Figure 27] FIG. 27 shows an embodiment where the temperature sensor uses the same electrodes as the impedance / conductivity electrodes. [Figure 28A] FIG. 28A illustrates a gastric access device in scale showing the approximate lengths of different portions of the anatomy. [Figure 28B] FIG. 28B illustrates an example of placement of a gastric access device within a child. [Figure 29A] FIG. 29A shows details regarding an embodiment using one electrode for multiple sensors. [Figure 29B] FIG. 29B shows details regarding an embodiment using one electrode for multiple sensors. [Figure 30A] FIG. 30A illustrates an embodiment of an anti-clogging mechanism. [Figure 30B] FIG. 30B illustrates an embodiment of an anti-clogging mechanism. [Figure 30C] FIG. 30C illustrates an embodiment of an anti-clogging mechanism. [Figure 30D] FIG. 30D illustrates an embodiment of an anti-clogging mechanism. [Figure 30E] FIG. 30E illustrates an embodiment of an anti-clogging mechanism. [Figure 31] FIG. 31 is a block diagram illustrating a data processing system that may be used in any embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Various exemplary embodiments are described in detail with reference to the following figures.

[0019] For ease of explanation, exemplary embodiments are described below with reference to the figures in the context of placing a feeding tube, assessing gastric volume / emptiness, and preventing / identifying / managing / monitoring gastric reflux in a patient.

[0020] FIG. 1 illustrates a gastric access device according to one embodiment at a given location in the anatomy of a human body. Anatomical structures include an esophagus 102, a stomach 104, a trachea 106, lungs 108, and a 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 assist in accessing the stomach or other areas of the gastric tract, as well as to assess gastric volume or emptying during feedings, and to prevent, identify, and / or manage reflux. The gastric access device may include a lumen for introducing nutrition into the patient's stomach. Alternatively, the gastric access device may be used in conjunction with (inside or alongside) a feeding tube.

[0021] FIG. 1 shows two types of sensors: Type 1, designated 114, and Type 2, designated 116. In some embodiments, Type 1 sensors are a pair of electrodes or multiple electrodes for detecting impedance or conductivity. Type 2 sensors are temperature sensors. Other types of sensors include humidity sensors, pressure sensors, chemical sensors, ECG sensors, EGG (Electrogastrogram) sensors, pH sensors, and optical sensors. For example, pressure and humidity sensors can be used to detect pressure and humidity fluctuations associated with breathing, thereby determining when the device is in the trachea / lungs.

[0022] The sensors may be used to assist in device placement, to assess gastric emptying and contents, 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 that measures the impedance of the environment surrounding the sensor and at least one temperature sensor. The one or more impedance sensors may be used for device placement, monitoring gastric emptying, reflux, etc., while the one or more temperature sensors may be used for device placement and, in some cases, continuous monitoring of the patient's temperature.

[0023] One or more temperature sensors can be used for device placement by detecting the relatively small temperature fluctuations that occur when breathing in ambient air at a temperature different from body temperature. For example, room temperature air is typically cooler than body temperature. If a gastric access device is accidentally advanced into the trachea instead of the esophagus, one or more temperature sensors in the gastric access device will detect temperature changes associated with breathing. These temperature fluctuations do not occur when the gastric access device is positioned in the gastric system, i.e., the esophagus, stomach, or intestine.

[0024] 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 will exhibit fluctuations associated with breathing if the gastric access device is misplaced in the trachea or lungs. This is important because this is a dangerous error and could result in complications or even death if the feeding supply is subsequently misplaced in the lungs.

[0025] The embodiment of FIG. 1 may include, for example, two or more impedance sensors 114 and two or more temperature sensors 116. Impedance sensors can be used for device placement, gastric residual volume (GRV) / gastric emptying measurement, and reflux measurement. Details of embodiments including GRV / gastric emptying using impedance sensors or other sensors are included in U.S. Patent Application Publication No. 2017-0071502, filed November 23, 2016; U.S. Patent Application Publication No. 2016-0331298, filed July 28, 2016; and U.S. Patent Application Publication No. 2018-0078195, filed November 13, 2017, each of which is incorporated by reference herein in its entirety. Temperature sensors can also be used to confirm device placement and, in some circumstances, as a primary indicator of placement.

[0026] Figure 2 illustrates the relative conductivity detected by impedance or conductivity sensors integrated into a gastric access device in different regions of the anatomy. The stomach is characterized by a higher conductivity than the lungs. As the gastric access device advances through the nose or mouth into the esophagus and possibly into the stomach, one or more conductivity / impedance sensors can identify the entry of the device's distal tip into the stomach by an increase in conductivity (or decrease in impedance) due to contact with the stomach's fluid contents, which generally have a higher conductivity (lower impedance) than the esophageal environment and fluid. This detection also occurs fairly quickly, in real time—on the order of less than a second or a few seconds (1-4 seconds). However, there may be situations where such changes in impedance / conductivity are not apparent, or where the impedance / conductivity sensors on the gastric access device detect highly conductive regions in the trachea or lungs, for example, when the sensor is buried in mucus or encounters tissue.

[0027] A secondary detection system can 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 can be used on the gastric access device to detect temperature fluctuations, or the lack of temperature fluctuations, caused by breathing. If a temperature change associated with breathing is detected, the device is likely in the trachea or lungs and should be retracted. If a temperature change associated with breathing is not detected and one or more impedance sensors indicate high conductivity / low impedance, the device is likely in the stomach. Temperature fluctuations associated with breathing are likely to have frequencies associated with breathing, for example.

[0028] Six weeks after birth: 30 to 40 breaths per minute 6 months: 25 to 40 breaths per minute 3 years: 20 to 30 breaths per minute 6 years: 18 to 25 breaths per minute 10 years: 17 to 23 breaths per minute Adults: 12 to 18 times / min Elderly people aged 65 and over: 12 to 28 breaths per minute Elderly people aged 80 and over: 10 to 30 breaths per minute The controller may incorporate a frequency filter to filter out these or other respiratory frequencies in order to separate temperature fluctuations associated with breathing from the temperature signal over time.

[0029] The controller / monitor can use these frequencies to determine whether the temperature fluctuations are associated with breathing. This signal must be analyzed over multiple breaths, which can result in a longer analysis time for the controller than the impedance / conductance signal. Determining whether the temperature signal represents breathing can take 8-15 seconds or 10-20 seconds. As a result, the temperature measurement can be used as a secondary indicator of device placement, a confirmation of placement via the impedance sensor indicator. The user may be prompted by the device to pause the advancement of the device while this confirmation is performed.

[0030] Figures 3 and 4 show measurements from a gastric access device equipped with 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 measurements when the device is placed in a patient's esophagus or stomach. Figure 4 shows temperature measurements when the device is placed in a patient's trachea or lungs. In some embodiments, at least one temperature sensor may be configured to be placed in the trachea when the tip of the device is in the patient's lungs.

[0031] Figure 4 illustrates temperature signal variations associated with breathing, which are not present in Figure 3. Temperature sensors that are in contact with or embedded in tissue may not detect temperature variations in the surrounding tissue environment. This is shown in the top graph of Figure 4. As the device is advanced into the lungs, the distal-most sensor becomes embedded in the tissue, resulting in a flat temperature signal. A second, more proximal temperature sensor clearly exhibits temperature variations in the bottom graph of Figure 4. Because of this phenomenon, two or more temperature sensors are useful, and the controller looks for temperature variations associated with breathing from at least one of the temperature sensors. Additionally, the temperature sensors (or any sensors) may be positioned at different locations along the length and / or circumference of the device. For example, the temperature sensors may be positioned radially, 180 degrees apart, and / or along the length of the gastric access device.

[0032] In some embodiments, a temperature sensor is used to detect the temperature at and when the device first enters the body. The temperature sensor may detect temperature fluctuations due to breathing in the patient's throat as the device is inserted. These fluctuations may cease as the device passes the junction between the trachea and esophagus. Because this distance is relatively short (approximately 5-15 cm) into the patient's body, a flattening of the temperature fluctuations over this distance can be an indication that the device is properly propagating down the esophagus and trachea. Thus, a flattening or disappearance of the temperature fluctuations over a relatively short distance into the patient's body is an additional indication that the device is correctly placed. Alternatively, a failure of the temperature fluctuations to flatten out or an increase in the magnitude of the temperature fluctuations as the device is advanced indicates that the device is advancing into the trachea. The distance beyond the lips that the device has advanced may be automatically determined by the system using dimensional markings or indicators along the length of the device shaft and a camera or other detection mechanism at the lips / device entrance.

[0033] 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's body. In some embodiments, the ambient temperature can be measured continuously or intermittently over time using a temperature sensor external to the patient's body, such as an ambient temperature sensor built into the controller or an ambient temperature sensor at the proximal end of the feeding tube that remains outside the patient's body. The ambient temperature sensor can be remote from both the feeding tube and the controller but in communication with the controller. The ambient temperature can be used to determine the patient's relative temperature at different anatomical locations by comparing the temperature sensed by the sensor on the feeding tube to the ambient temperature. In this manner, relative temperatures can be measured at different anatomical locations along the feeding tube. An average temperature can also be determined by looking at the attenuated temperature signal. While the average or attenuated temperature signal may not show the same variations in lung temperature or esophageal temperature, if the ambient temperature is lower than body temperature, the average lung temperature will be lower than the esophageal temperature. By monitoring the average / decaying temperature at one or two points or along the feeding tube as the device advances, the controller can determine approximately where the device is located in the anatomy. Different signals at different points along the length of the feeding tube provide temperature information (either average temperature or temperature fluctuations) and can indicate whether the feeding tube segment is in the pharynx, trachea, esophagus, lungs, stomach, intestine, or in contact with tissue. Other sensors, such as impedance / conductivity sensors, can also be used to assist in location determination. For example, if temperature sensors are measuring body temperature and there is no temperature fluctuation, the feeding tube segment with these sensors may be in the stomach or in contact with tissue. A conductivity / impedance sensor may be able to distinguish between these two. Other sensor types, such as ECG or pH, can also be used.

[0034] FIG. 5 illustrates how the gastric access device may be passing through the trachea and into the lungs. This is an undesirable situation and is identified as such in embodiments of the gastric access device. The impedance / conductivity sensor is unable to detect the significant increase in conductivity shown in the graph of FIG. 2. Additionally, the temperature sensor detects 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, which is 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 run from the various sensors to the hub 510. The monitor 502 may also be connected to a feeding pump 504 via a wired or wireless connection 506 to control the patient's nutrition through the feeding lumen of the device 112 or through a separate feeding tube. The monitor interprets one or more of these signals to indicate that the device is not properly positioned and should be retracted.

[0035] 6 illustrates a gastric access device positioned within a patient's stomach. In this situation, the impedance / conductivity sensor indicates high conductivity and one or more temperature sensors indicate the absence of temperature fluctuations associated with breathing. A monitor interprets one or more of these signals to indicate proper placement of the device within the stomach.

[0036] 7 is a flow chart outlining the functionality of a controller communicating with a gastric access device equipped with one or more impedance / conductivity sensors and one or more temperature sensors. 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 can continue to instruct the user to advance the device until the impedance / conductivity sensors detect high or low impedance, or until one or more temperature sensors detect temperature fluctuations associated with breathing.

[0037] If the control unit receives a signal from the temperature sensor indicating temperature fluctuations associated with breathing, as shown in box 714, once the temperature sensor has passed the Respiratory-Gastric Junction (RGJ), the control unit 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.

[0038] If the sensor initially detects high conductivity during device advancement, as shown in box 704, the gastric access device may be in the stomach and the sensor may be detecting stomach contents. The controller may indicate that the device is in the stomach or may display or play a pause signal, prompting the user to pause for a few seconds to collect temperature sensor signal data and determine whether there are any breathing-related fluctuations detected by the temperature sensor. If these fluctuations are detected once the temperature sensor is past the RGJ, as shown in box 706, the controller may determine that the access device may be entering the lungs and may instruct the user to retract the device, as shown in box 708. If no temperature fluctuations are detected, as shown in box 710, the controller may confirm that the device is properly positioned in the stomach, as shown in box 712.

[0039] In addition to or instead of the impedance / conductivity sensors and temperature sensors, other sensors can 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 likely not in the lungs or trachea and is therefore likely in the stomach. FIG. 8 illustrates the relative anatomy of the lungs 108, heart 110, and stomach 104. Note that the stomach is below the heart, while the lungs are above or at 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 in gastric access devices disclosed herein, have leads or wires extending along the length of the device, connecting 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.

[0040] The ECG sensor detects cardiac electrical activity, 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, and an origin of the signal. The signal has a magnitude and a frequency, and the various zones may include peaks of various positive and negative magnitudes. The gastric access device may include two or more ECG sensors within the device itself, such as sensor 804. Alternatively, the gastric access device may include one or more ECG sensors, and the system may include an external ECG sensor 806. The external ECG sensor is also electrically connected to the monitor via a wire or wirelessly. As the gastric access device advances, an ECG signal is continuously received by the monitor. Because the ECG sensor detects cardiac electrical activity, the signal changes as the sensor moves down the esophagus, past the heart, and toward the stomach. These changes may be the magnitude or direction (positive or negative) of one or more zones of the ECG signal. The changes 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 ECG on the sternum may exhibit a different change than a system with two or three ECG sensors on the feeding tube. This change may vary depending on the system configuration, but for a given system configuration, the change will be detected by the controller because the relative position of at least one of the ECG sensors (the sensor on the feeding tube) changes as the sensors pass through the heart.

[0041] FIG. 8 shows an embodiment of a feeding tube in a gastric access device as the sensor approaches heart level. At this point, it is still unclear from the ECG sensor readings whether the access device is in the esophagus or the lungs. However, as the device is advanced down the esophagus, the ECG readings change to indicate that the device is passing through the heart. For example, the ECG signal may invert, certain zones of the ECG may invert, the signal may change in magnitude, or certain zones of the ECG may change in magnitude. Once the controller detects this signature, it is determined that the gastric access device is in the stomach below the heart. An external ECG sensor 806 may be present or absent.

[0042] ECG sensors can be used in conjunction with other sensors, such as impedance / conductivity sensors and temperature sensors, to assist in confirming the position of the gastric access device within the stomach. Either sensor type can share the same electrodes with other sensor types.

[0043] 9 shows a gastric access device according to one embodiment that incorporates an ECG sensor into a nasal or nostril or mouth or facial patch 902. The sensor can be placed on the outside of the nose, inside the nose, outside of the mouth, inside the mouth, or elsewhere on the face. The sensor may also be incorporated into the feeding tube of the gastric access device itself, for example, as part of the tape that holds the device in place.

[0044] 10 is a flowchart outlining the functionality of a controller communicating with a gastric access device equipped with one or more impedance / conductivity sensors and one or more ECG sensors. 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 can continue to instruct the user to advance the device until either the impedance / conductivity sensors detect high or low impedance, or one or more ECG sensors detect a change in the ECG signal indicating the device has passed beneath the heart.

[0045] 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 can indicate to the user that the device is likely in the stomach. Alternatively, or in addition, the controller can use signals from the conductivity sensors to confirm placement. If the controller does not receive a signal indicating high conductivity or low impedance from one or more impedance sensors on the device, as shown in box 1016, the device is likely not in the stomach, and the controller can instruct the user to retract the device, as shown in box 1018. However, if the controller receives a signal indicating high conductivity or low impedance from one or more impedance sensors on the device, as shown in box 1020, the controller can indicate to the user that the device is likely in the stomach, as shown in box 1022.

[0046] If the sensor initially detects high conductivity during device advancement, 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 may determine and communicate that the access device is likely in the stomach, as shown in box 1008. If the ECG sensor signal signature indicates that the device has not passed under the heart, as shown in box 1010, the controller may indicate that the device is likely not in the stomach and may indicate retracting and re-advancing the device, as shown in box 1012.

[0047] 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 verifying that the end of the feeding tube has not deviated, resulting in an inaccurate signal signature. This can be done by verifying the impedance / conductivity between different sensors or different pairs of electrodes and determining whether the different sensors or different pairs of electrodes are closer to each other than when the feeding tube is relatively straight. For example, the controller can quickly verify whether there is an abnormally high conductivity between the distal-most impedance sensor and the next-closest impedance sensor. The controller can then verify whether there is an abnormally high conductivity between the distal-most impedance sensor and an impedance sensor one sensor further away from the proximal-most impedance sensor, etc. If there is no abnormally high conductivity between two impedance sensors on the feeding tube, the feeding tube is likely not deviated, and the ECG signal signature is reliable.

[0048] While the preceding flowcharts have illustrated the flow of an embodiment with two sensors, it should be understood that one sensor can confirm or question device placement based on the other sensors, and that gastric access device embodiments can incorporate one, two, three, or more sensors. The sensors may operate independently, for example, for a particular patient type or environment, or they may operate in concert, as in the flowcharts presented herein. Additionally, not all sensors may be used for all patients. For example, device embodiments may include three sensors: a temperature sensor, an impedance / conductance sensor, and an ECG sensor. One, two, or three sensors may be used for different patients and environments. For example, three sensors may be used for most patients, but the temperature sensor may not be used in a warm room. As another example, an ECG sensor may not be used for patients with arrhythmias. In some embodiments, two sensors are provided, allowing for the use of one or two sensors for the majority of patients and environments. In some embodiments, more than two sensors are provided for placement verification redundancy.

[0049] Figures 11A, 11B, 12, and 13 illustrate several embodiments of gastric access devices. Figure 11A shows a main device shaft 1102, a feeding pump connector 1104, and a monitor connector 1106. Figure 11B is an enlarged view of the portion within the oval outline in Figure 11A. Figure 11B includes electrodes 1108, and any pair of electrodes represents an impedance / conductivity sensor. The pairs of electrodes that make up a sensor do not need to be adjacent to each other. Also shown is a temperature sensor 1110, such as a thermistor or thermocouple, as well as an opening 1112 through which the feeding stream exits the device. Figure 11B also illustrates example distances from the tip of the device to various sensors. Figure 11B illustrates a device with two temperature sensors 1110 circumferentially 180 degrees apart and at different points along the length of the device. Figure 12 illustrates four temperature sensors 1110, circumferentially 180 degrees apart at two different locations along the length of the device. Although two locations are shown, one or more temperature sensors may be placed in one or more locations. FIG. 13 shows temperature sensors 1110 positioned to completely surround the device 360 ​​degrees. In these and other embodiments, the temperature sensors detect breathing-related fluctuations when the device is in the lungs, and the device's controls can instruct the user to retract the device. As shown in FIG. 4, having temperature sensors at multiple locations (circumferentially, longitudinally, or both) helps detect breathing-related temperature fluctuations in more situations. In some embodiments, the temperature sensors are circumferentially spaced more than 90 degrees apart. In some embodiments, the temperature sensors are circumferentially spaced more than 45 degrees apart. In some embodiments, at least two temperature sensors are positioned at one circumferential location. In some embodiments, at least three temperature sensors are positioned at one circumferential location. In some embodiments, at least four temperature sensors are positioned at one circumferential location. In some embodiments, at least two temperature sensors are positioned circumferentially along the length of the device.In some embodiments, at least three temperature sensors are circumferentially positioned along the length of the device. In some embodiments, at least four temperature sensors are circumferentially positioned along the length of the device. Other configurations are also contemplated. For example, a temperature sensor can be located on the monitor, providing a fluid path from the sensor to the feeding tube. Other sensors besides temperature sensors can be similarly positioned.

[0050] One or more temperature sensors can be positioned in the trachea when the distal tip of the device is in the lung. For example, the sensors can be positioned approximately 250-350 cm from the distal tip. Alternatively, the sensors can be positioned approximately 200-400 cm from the distal tip. Alternatively, for smaller patients, the sensors can be positioned approximately 100-150 cm from the distal tip. Alternatively, the sensors can be positioned approximately 100-200 cm from the distal tip.

[0051] In some embodiments, one or more temperature sensors can be located on the exterior of the gastric access device. In some embodiments, one or more temperature sensors can be located entirely within the wall of the gastric access device. In some embodiments, one or more temperature sensors can be located within the wall of the gastric access device such that the temperature sensor is exposed to the exterior of the device.

[0052] The ECG and / or temperature sensors may be separate from the impedance / conductance sensors or may utilize some or all of the same electrodes. In embodiments using the same electrodes, different types of sensing (temperature, ECG, impedance / conductance, etc.) may be used alternately on the same electrode, at different locations or times during the procedure, or on different patients. Different or the same leads may be used for different functions of an electrode. Either sensor may use electrodes that completely or only partially surround the device.

[0053] 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 are a tube placement display area 1402, a real-time nutritional delivery rate display area 1404, and a nutritional delivery rate over time or nutritional delivery rate trend area 1406. Other display areas can include GRV / gastric emptying trend over time, real-time GRV / gastric emptying, placement instructions (e.g., "back out," "pause," "continue," etc.), and gastric reflux inputs such as warning indications, warnings for prevention, reflux event identification, and management. Audio prompts and / or warnings can also be provided. Control buttons 1408 can include a power button, a settings button, etc., and can be physical or touch-sensitive.

[0054] The placement display area 1402 may include a graphical representation of the 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 sensors detect the device in the stomach, the stomach may flash or appear green. If one or more sensors detect the device in the lungs, the lungs may flash or appear red. If neither the stomach nor the lungs are detected by the sensors, the esophagus may flash green or another color to indicate the user should continue moving forward. The distance traveled by the device within the patient can be incorporated into the placement assessment. In some embodiments, the controller communicates with sensors, such as optical sensors, that automatically measure the length of the device within the patient. If signals from multiple sensor types are conflicting, or if signals from any one sensor type are conflicting, the corresponding body part may flash or appear orange.

[0055] Further information may be displayed elsewhere on the monitor. In some embodiments, once the information is confirmed, the body region indicator may flash and then remain solid. For example, if the device enters the stomach and the impedance sensor detects high conductivity, the stomach shape may flash green (or indicate to the user to pause advancement of the device, or indicate that the user or the controller should pause before initiating nutrition delivery), indicating that the controller has preliminarily determined that the device is in the stomach. The controller may then continue to collect temperature sensor data over the next few to tens of seconds. If this data determines that the device is likely not in the lungs (no fluctuations associated with breathing), the stomach shape may become solid green instead of flashing green (or the pause indication may disappear), and the user may initiate nutrition delivery or continue advancing the device.

[0056] Alternatively, if the temperature sensor detects a temperature fluctuation, the stomach shape may turn orange or red to indicate possible lung entry. Additionally or alternatively, the lungs may turn red or orange in this scenario. The controller may instruct the user to retract the device or prevent the nutrition delivery function from being initiated.

[0057] The pause for collecting temperature data can 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 can be in the form of instructing the user not to advance the device and / or not to initiate nutrition delivery through the device. The pause can cause the controller to prevent the device from initiating nutrition delivery until the pause ends and the stomach is positively identified and confirmed.

[0058] Indicators that are displayed on the screen or indicated by sound or touch (vibration, etc.) include: -Pause -pause for x seconds - Pause until an indicator (visual, audible, tactile) tells you to move the device forward or backward -xcm retract device -Device xcm advance -xcm retract and pause device -xcm advance device and pause - Move the device back xcm, then move it forward again, etc.

[0059] In some embodiments, the position display 1416 and / or other displays are alternatively or additionally provided 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 control functions are included, fully or partially, in 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 small display may be fully portable and incorporate all or part of the monitor / control functions. Part of the monitor functions may be incorporated into the remote electronic device 1418. Also shown is a feeding input line 1414. The monitor housing 1410 may include a docking area into which the feeding tube may be docked so that when the feeding tube is docked to the monitor, the feeding tube may operate with the position display 1416 or with the full monitor display included in the housing 1410.

[0060] Other display areas include data views such as a temperature data view or an ECG data view that graphs signals from sensors. Other display areas include flow-through information such as risk, event, management, contextual (i.e., historical) information, and trends.

[0061] The rate of nutritional delivery depends on the detected GRV / gastric emptying and may be controlled automatically, semi-automatically, or manually by the control unit, where semi-automatic control means that small adjustments are made automatically and major adjustments are prompted by the user.

[0062] 15A and 15B illustrate a gastric access device according to one embodiment including one or more tissue sensing electrodes 1502 for sensing tissue impedance / conductivity upon contact with tissue. These sensors can be used to locate the lower esophageal sphincter (LES), upper esophageal sphincter (UES), and / or pyloric sphincter, or other regions of the anatomy. Sphincters tend to be easier to identify with contact sensors because of their small diameter compared to the surrounding tissue. These can be identified by sensing tissue contact with electrodes around the periphery of the gastric access device. That is, two or more electrodes may be placed around the periphery of the device to determine tissue contact between the electrodes (e.g., when the sensor is within a small diameter region of the anatomy).

[0063] 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, and in some embodiments, the diameter of the device shaft at the location of the tissue sensing electrodes may be expandable and / or contractible like a cage or balloon to increase contact with the tissue.

[0064] FIG. 15B is 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, increasing the likelihood of the electrode contacting tissue. In some embodiments, the protruding electrodes may be retractable or may protrude different distances from the shaft of the device. One, two, three, or more electrodes may be provided around the periphery of the device at one or more locations along the shaft. Also shown is an electrode lead 1506 enclosed within the outer shaft 1504. The location of the LES, UES, and / or pyloric sphincter is determined by the degree of tissue contact (how many electrodes around the periphery are in contact with tissue) and the length of the device within the patient.

[0065] For example, if the sensor is inserted 15-20 cm into the body (measured from the incisors), it can identify the UES. If the sensor is inserted 30-50 cm into the body, it can identify the LES. If the sensor is inserted 50-100 cm into the body, it can identify the pyloric sphincter. These measurements can be narrowed down based on the patient's size. Different tissue electrodes / sensors can be used along the length of the device shaft to identify different anatomical tissue regions. The diameter, or the distance the tissue electrode protrudes from the shaft, can also determine which sphincter the electrode is sensing.

[0066] 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.

[0067] Some embodiments of the gastric access device include the ability to avoid reflux events, detect reflux events or device movement, and manage reflux events, for example, by aspirating refluxed material from the patient, using the same sensors used for positioning or other sensors.

[0068] 16A and 16B illustrate a gastric access device according to one embodiment including one or more tissue electrodes / sensors 1502 and one or more reflux sensors 1602. One or more reflux sensors are positioned more proximally on the shaft and can detect gastric reflux in the esophagus above the LES. These sensors are configured to detect gastric reflux after the device is placed in the patient. These sensors are positioned so that one or more reside within the esophagus after the device is placed. These sensors may be impedance / conductivity sensing electrodes, pH sensors, or other sensors. There may be one or more electrodes on the circumference of the device shaft at any location along the shaft.

[0069] When the reflux sensor is in the presence of reflux fluid, its conductivity increases and its impedance decreases. Because it is advantageous to avoid contact between the reflux sensor and esophageal tissue, the reflux sensor 1602 may be positioned in 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 area is shown in FIG. 16B. Multiple reflux sensors along the length of the device's shaft may help determine the extent of reflux, i.e., how far up the esophagus, whether reflux is progressing, receding, and / or whether there is a risk of aspiration. Alternatively, the reflux sensor may be relatively flush with or slightly protrude from the outer surface of the device's shaft.

[0070] FIG. 17 adds an expandable member 1702 and a suction tube 1704 to the embodiment shown in FIG. 16A. A reflux sensor 1706 may be used to identify the presence of reflux, as described above. If reflux is detected, or if reflux is detected and deemed a risk, the controller may expand the expandable member, such as an inflatable balloon or other mechanism, and suction the suction tube to clear the reflux from the esophagus. The reflux sensor may detect that reflux has cleared and shrink the expandable member to stop suction. These actions may be performed manually based on an alert or automatically by the controller.

[0071] Some embodiments may include a suction tube 1704 without an expandable member 1702. In these embodiments, the level of suction must be controlled to prevent stomach contents from being aspirated into the esophagus. The suction tube can be placed anywhere above or below the LES. In some embodiments, the suction tube can be moved along the shaft to precisely position the suction. This suction tube positioning may be determined by the level of reflux, as determined by signals from multiple reflux sensors along the length of the device's shaft.

[0072] Figure 18 illustrates the embodiment shown in Figure 17 positioned in anatomy. A tissue sensor 1502 can aid in device placement. For example, by locating the LES, a physician can know when the device opening has passed through the LES and into the stomach, positioning the device 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 in the esophagus.

[0073] 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 suction on the wall, or other suction mechanism. The suction line 1804 may or may not pass through the hub 510.

[0074] Figure 18 shows the main device shaft of a gastric access device and its concentric suction tube. Figure 19 shows another embodiment in which the suction tube 1902 is located 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 main shaft of the gastric access device. Alternatively, the suction tube may be positioned through the lumen of the gastric access device or may be part of, but external to, the shaft of the gastric access device.

[0075] In some embodiments, reflux suction is initiated and / or continued based on a signal from the reflux sensor indicating the presence of reflux 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 clear any reflux that may or may not be present and / or test for reflux. Such periodic suction is performed regardless of whether reflux is detected. The expandable member may or may not be expanded during such periodic suction. By applying periodic suction, the risk of reflux can be effectively eliminated without relying on reflux detection. Preferably, these regularly scheduled reflux suction events, in embodiments where the expandable member is not present or expanded, apply a sufficiently low level of suction so that stomach contents are not aspirated. If reflux is detected (in the anatomy, in the suction tubing, or elsewhere) or collected during a regularly 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 expandable member if the suction level of a reflux suction event is increased or extended.

[0076] Embodiments that include regularly scheduled reflux suction events may not include a reflux sensor on the device. However, other reflux sensors may be included to determine whether reflux is being suctioned out of the body. For example, a reflux sensor may be present on the outside of the body, in the control unit, waste receptacle, suction line, or hub. Regularly scheduled reflux suction events may be scheduled every 5 minutes, 10 minutes, 30 minutes, 60 minutes, or every 5-30 minutes, 30-60 minutes, or any other suitable time frame. The schedule can be freely set by the user. The interval may vary depending on past reflux events. For example, if reflux is detected more than once or twice, scheduled reflux suction events may become more frequent. This change can be made manually or automatically.

[0077] In some embodiments, a low level of suction can be used continuously or semi-continuously. In these embodiments, the expansion member may not expand during continuous suction to prevent prolonged blockage of the esophagus. This continuous mode can be activated during feeding, all the time, or as a result of one or more reflux events.

[0078] In some embodiments, the expansion member can be expanded to block the esophagus for a longer period of time, essentially acting as an artificial LES to prevent reflux.

[0079] 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.

[0080] FIG. 20 illustrates a gastric access device, according to one embodiment, configured to locate and traverse the pyloric sphincter to enable nutritional delivery within a patient's intestine. A tissue detection sensor 1502 is shown in the region of the pyloric sphincter 2002. The tissue detection sensor's electrodes can sense the pyloric sphincter, as well as the LES. Because these regions of tissue have a smaller diameter than the surrounding tissue, the tissue detection electrodes can detect tissue contact by detecting 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 a single or multiple pairs of electrodes circumferentially positioned around the device shaft. In these smaller diameter regions, more electrodes around the device shaft are in contact with tissue, and therefore the tissue contact sensor / electrode signal can identify these regions by a change in the sensor signal as the device passes through the region.

[0081] In some embodiments, placement of the device at or past the pyloric sphincter can be identified or confirmed by other methods. The same methods can also be used to position the device within the stomach. For example, a pH sensor can determine whether the access device is in the post-pyloric or other location. The various sensors described herein can be used to detect specific signatures, such as pH fluctuations, absolute or relative temperature, peristalsis, and impedance / conductivity. An ECG sensor can be used to measure ECG signals that change as electrodes on the device move through the anatomy. For example, the ECG signal may change as the device passes through the patient's midline. The device may use a bright light detectable through the skin or other detectable light to identify when the distal end of the device is in the intestine. Electrodes on the device can be used to detect proximity to each other by impedance, conductivity, or other methods. This can indicate when the device is making a sharp 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. Force or pressure sensors can also be used to assess the curvature of the device and determine whether it is in a curved section of the intestine.

[0082] Some embodiments may include direct visualization, such as a camera or fiber optics, to determine and / or confirm placement of the device in the desired anatomy.

[0083] Some embodiments may include the ability to distinguish between the esophagus and the trachea by detecting the amount of air / gas drawn into the device when a vacuum is applied 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 prevent the device from contacting tissue when a vacuum is applied, one or more small boluses of air can be introduced into the device before applying a vacuum. Alternatively or additionally, openings on the circumference of the shaft of the device can be used.

[0084] In some embodiments, electrodes can be used to measure myoelectric activity, which may be used to assist in placing the device at the desired location.

[0085] 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.

[0086] Sensors built into the gastric access device can collect data continuously, intermittently, on demand, or only at specific times, such as when confirmation of placement is required.

[0087] The devices disclosed herein include nasogastric tubes with sensors configured to avoid accidental placement of the tube in the trachea or lungs and to assist in stomach placement. These sensors include a temperature sensor for detecting respiratory fluctuations and an impedance / conductivity sensor for detecting 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.

[0088] An electrogastrogram (EGG) may be used to identify the location of the gastric access device within the stomach. EGG sensors may be different from other sensor types or may use the same electrodes as, for example, ECG sensors or impedance / conductivity sensors.

[0089] In some embodiments, electromagnetic sensors can be used in addition to other sensors for positioning.

[0090] Although the embodiments disclosed herein describe 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.

[0091] FIGS. 21A-21C illustrate one embodiment for measuring / determining intra-abdominal pressure via a feeding tube. FIG. 21A shows a gastric access device, or alternatively, a conventional feeding tube within the stomach. FIG. 21B shows 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. As the fluid fills the lumen, the pressure increases. When a portion of the gas / fluid, or bubble 2104, exits the lumen of the gastric access device / feeding tube, the pressure suddenly drops, indicating that the pressure within the column of fluid has overcome the pressure within the stomach fluid. The pressure of the fluid within the stomach is identical to, or correlates with, the patient's intra-abdominal pressure (IAP). Therefore, the controller can derive the patient's IAP by monitoring the pressure as the column of fluid is introduced into the lumen of the gastric access device / feeding tube. The fluid may be air or other gas, or water or other liquid. The column of fluid may be solid or intermittent. The IAP measurement sequence may be periodically performed by the controller. The IAP measurement sequence may be performed before or after feeding. This is the preferred time to measure IAP after feeding, as the stomach contains more fluid. IAP measurements may also be performed manually by physically viewing the pressure on a gauge similar to a blood pressure cuff.

[0092] In some embodiments, bubbles similar to bubble 2104 can be used to measure pressure fluctuations to help confirm placement of the device in either the esophagus or trachea.

[0093] FIGS. 22A-22C illustrate another embodiment for measuring / determining IAP via a feeding tube. FIG. 22A shows a stomach access device, or alternatively, a conventional feeding tube within the stomach. The stomach may contain air / gas 2202. In this embodiment, the air / gas 2202 is removed by suction as needed. As shown in FIG. 22B, the stomach is filled with a liquid or other fluid. This air / gas reduction step may or may not be necessary to obtain an accurate IAP measurement. As shown in FIG. 22C, a column 2204 of fluid, preferably liquid, is then introduced into the lumen of the tube. The pressure of the fluid column can then be measured to determine the fluid pressure within the stomach, an indicator of IAP. These steps may be performed by a controller, manually, or both.

[0094] 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 can be a balloon or other pressure-sensitive bladder. Inflation / deflation of the bladder is accomplished via a lumen 2304. Lumen 2304 can also be used to monitor the pressure within the balloon / bladder, which is an indicator of IAP. The inflation / deflation and pressure measurements are performed automatically or on command by a controller. Measurements can be performed automatically periodically and / or before and / or after feeding.

[0095] Some embodiments of the gastric access device may include the ability to test for kinks or bends in the feeding tube. In one embodiment, the controller may introduce pressurized fluid (gas or liquid) into the lumen of the feeding tube and measure the pressure required to move the fluid through the lumen. The baseline pressure of the unbent feeding tube can be sensed to determine the kinked pressure range. As the tube bends or kinks, higher pressures are required. 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 slope of the change in pressure over time.

[0096] Bends or kinks in the feeding tube can also be measured electronically, such as by measuring the proximity of the electrodes to one another. If the electrodes are closer together than the spacing along the feeding tube, there may be a kink or tight bend in the tube. This can be done by measuring the impedance and / or conductance between the electrodes. The electrode pairs can be changed by the controller to determine electrode proximity. Alternatively, the same electrode pairs can be used.

[0097] See, for example, FIGS. 24 and 25. FIG. 24 shows a gastric access device having a pH, temperature, 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 or placement of a feeding tube to measure conductance / impedance across the electrode pairs. However, different electrode pairs can also be used. For example, electrode 1 and electrode 6 can be used as a pair. The distance between electrode 1 and electrode 6 can be determined by the conductance / impedance. When the device is relatively straight, the distance between electrode 1 and electrode 6 is Z. However, if the distance decreases to Z' as shown in FIG. 25, the controller can sound an alarm / alarm or automatically attempt a de-kinking procedure to untangle the tube. Alternatively, this condition can indicate that the device is within the patient's intestine. Note that bending detection can involve any pair of electrodes and their relative distance. For example, a bend / kink may not change the conductance / impedance of the original electrode pair, but the conductance / impedance of a more distant electrode pair may change. This combination may indicate a bend / kink condition.

[0098] In some embodiments, the device may be bent / kinked so much that two electrodes on the device touch each other, shorting out the signal. This information can be used to assess the kink.

[0099] In some embodiments, a piezoelectric member is incorporated into the device, and the orientation of the device (including whether it is bent / kinked or not) can be determined by monitoring changes in the electrical properties of the piezoelectric member.

[0100] In some embodiments, one or more strain gauges can be used to assess the kinking / bending of the device.

[0101] In some embodiments, one or more accelerometers may be used to determine the orientation of various portions of the device, hi some embodiments, a weighted tip may be used to determine the orientation of the tip of the device.

[0102] In some embodiments, one or more pressure sensors are used to position the device. For example, the pressure exerted on the device in the stomach is higher than the pressure exerted in the esophagus. In embodiments with two or more pressure sensors, if there is no difference between two pressure measurements, this may indicate that one pressure sensor is in the stomach and one pressure sensor is in the esophagus. Two similar pressure measurements may indicate that the device is kinked in the esophagus.

[0103] In some embodiments, the injection of a conductive fluid can be used to assess bending / kinking of the device. After placement, the conductive fluid may be injected into the patient's mouth. When the device is not folded back into the anatomy, the electrodes will read an increasing conductivity signal, starting with the more proximal electrodes and gradually progressing to the more distal electrodes. When the device is folded back into the anatomy, the distal electrodes may signal an increase in conductivity out of sequence before the more proximal electrodes signal an increase in conductivity. Similarly, the device can use a temperature sensor and hot or cold liquids to perform a similar assessment.

[0104] Some embodiments incorporate automatic inflation to reduce kinking of the device. The controller automatically injects a stream or puff of air into the device as it is inserted. This air or gas acts to stiffen the device and prevent kinking during insertion. This process may occur automatically throughout the entire insertion process, or only when resistance is encountered, or when the device has reached a certain distance inside the patient.

[0105] In some embodiments, instead of or in addition to using a stylet, the device can be stiffened using pressurized air or fluid within the lumen of the device.

[0106] In some embodiments, the device may be automatically vibrated or rotated during insertion to prevent kinking.

[0107] In some embodiments, the distal tip has a corkscrew shape and can be rotated during insertion.

[0108] Some embodiments may include a balloon or other expandable member to prevent accidental withdrawal of the device after it has been placed. Gastric access devices may also include a balloon that can be inflated against the gastroesophageal junction after insertion into the stomach to prevent rolling back into the esophagus and inadvertent withdrawal.

[0109] Any of the embodiments that include the ability to determine device bend / kink can also be used to assess the shape of the device within the anatomy, i.e., these embodiments can be used for general device shape modeling in addition to bend / kink detection.

[0110] Figure 26 illustrates some of the anatomical landmarks used in placing a gastric access device. The entrance 2602 may be the patient's nostrils or lips. The respiratory-gastric junction (RGJ) 2604 is the junction of the trachea and esophagus. The lower esophageal sphincter (LES) 2610 is the lower end of the esophagus, just before its junction with the stomach. The pylorus 2612 is the junction between the stomach and the intestine. The trachea 2606 indicates the junction of the trachea with the bifurcation of the bronchi in the lungs. The bronchi 2608 indicate the estimated maximum depth of a feeding tube in case of misplacement. Below are approximate lengths for infants and adults for various lengths:

[0111] [Table 1] Based on these lengths, the gastric access device can be designed to have the appropriate type of sensor in the appropriate anatomy during placement and ongoing use.

[0112] FIG. 27 shows a device similar to that shown in FIG. 13. In this embodiment, a temperature sensor 1110, such as a thermocouple, may use the same electrodes as the impedance / conductivity electrodes 1108. ECG and other signals may also be obtained from the same electrodes. While FIG. 13 shows an example of a gastric access device according to one embodiment, the location, spacing, and number of sensors / electrodes may vary. Each electrode may use the same or different leads depending on its function.

[0113] Figure 28A shows the gastric access device shown in Figure 27 to a scale that indicates the approximate lengths of different parts of the anatomy. While dimensions vary greatly with age and individual, and may be narrower or wider than this scale, this diagram provides a visual scale for both the anatomy and the gastric access device.

[0114] FIG. 28B illustrates an example of gastric access device placement within a child. In this example, five impedance sensors (Z1-Z5) and two temperature sensors (T1, T2) are placed at different device locations / insertion depths to map the device's location in real time. Electrode pairs Z3 and Z5 also include thermocouples bonded to one electrode of each electrode pair Z3 and Z5 to measure temperature. The sensed measurements are relayed to and processed by the controller, which classifies the device's anatomical location. The device also includes an internal sensor in the feeding / medication lumen to directly sample the enteral nutrition being delivered. The expected placement of the gastric access device for feeding is as follows: Z1-Z3 are positioned within the stomach, Z4 is positioned 1-4 cm proximal to the lower esophageal sphincter (LES), and Z5 is positioned proximal to Z4 within the esophagus. For placement guidance and confirmation, the controller provides continuous visual feedback to the operator regarding the location of the distal portion of the device.

[0115] In some embodiments, it is desirable to place one temperature sensor as close to the distal tip of the device as possible, but not so close that the temperature sensor would typically impinge on tissue during advancement. This distal-most temperature sensor aids in device placement. As the device is advanced, the distal-most temperature sensor detects temperature fluctuations associated with breathing ambient air or a lower temperature while the sensor is over the RGJ. As the device is advanced further into the esophagus, the temperature fluctuations should plateau or the average temperature should increase. However, if the device is advanced into the trachea, which is undesirable, the distal-most temperature sensor will continue to detect temperature fluctuations or a temperature lower than body temperature even after advancing into the trachea. This undesirable advancement causes the system's controller to issue a warning to the user and instruct the user to retract the device.

[0116] In some instances, the gastric access device may be undesirably positioned within the trachea, but the distal-most temperature sensor is in intimate contact with tissue and will not detect temperature fluctuations or temperatures below body temperature. The second, more proximal temperature sensor is positioned to detect temperature fluctuations or temperatures below body temperature if the device is misplaced within the trachea. The more proximal temperature sensors are preferably positioned along the length of the device so that the distal end of the device passes through the RGJ before passing too far into the bronchi.

[0117] Although two temperature sensors are shown here, fewer or more temperature sensors may be positioned along the device. In some embodiments, each electrode on the device is capable of sensing impedance / conductivity, temperature, ECG, and possibly other parameters. The functionality of the different electrodes may be controlled by a controller. The sensed parameters may alternate between placement and use, or the sensed parameters may be linked to the patient's size or anatomical length.

[0118] 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 and other measurements, the electrodes along the device may be assigned appropriate functions, thereby providing at least a distal-most temperature sensor and a proximal temperature sensor to detect temperature fluctuations and / or average temperature in the trachea and esophagus while the device is introduced into the patient. In some embodiments, the proximal temperature sensor is positioned to pass through the RGJ before the distal-most temperature sensor advances too far into the bronchus. In some embodiments, the distal-most temperature sensor is proximal to the distal-most pair of electrodes. In some embodiments, the distal-most temperature sensor is integrated into the distal-most pair of electrodes.

[0119] Additional electrodes may be provided proximal to the most proximal electrode. These electrodes may be useful for taller or heavier individuals, but not for shorter or less muscular individuals. In this way, the same device can be used for patients with different body types and anatomies.

[0120] Additionally, temperature, impedance / conductance, ECG, pH, and other sensors disclosed herein can be used along the length of the device to detect any type of placement, including post-pyloric placement. For example, the device may have electrodes along a substantial portion of its length, allowing the controller to receive sensor signals from all parts of the anatomical region where the device is placed, both during and after advancement. The controller can generate temperature maps, impedance / conductivity maps, ECG maps, pH maps, combined parameter maps, and the like, and analyze these signatures to determine the location of each electrode within the anatomical tissue. This allows the user to determine the location of the catheter tip, feeding openings, and the like.

[0121] FIGS. 29A and 29B show details of an embodiment using a single electrode for multiple sensors. These figures show a pair of electrodes configured to sense both impedance or conductance and temperature. This sharing of electrodes reduces cost, space, and allows for a more compact device. Shown are an impedance / conductivity electrode 1108 and a temperature sensor 1110, which in these embodiments is one of the impedance / conductivity electrodes and is an inherently conductive (i.e., metallic) band. This can be achieved by connecting the impedance / conductance electrode 1108 to the 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, sharing of leads between two or more sensors is contemplated in some embodiments.

[0122] As shown in Figure 29A, the leads generally run along the length of the device. For illustrative purposes, Figure 29B is an electrical diagram showing these connections and some of the relevant functionality of the control unit. Lead 2902 connects the metal band or electrode to impedance / conductivity logic area 2906 of the control unit. Lead 2904 connects the metal band or electrode to temperature logic area 2908 of the control unit. These two logic areas are connected to switch 2910, which allows the control unit to switch between measuring conductivity / impedance or temperature using the same electrode or electrodes.

[0123] The switch 2910 may connect other logic / sensing domains, such as ECG and pH, where overlapping electrodes may be used, as with temperature and conductivity / impedance. In the case of pH sensing, a standard would be incorporated into the system to measure pH using electrodes. The ECG and pH sensors may use the same leads as the impedance / conductivity sensors.

[0124] 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 on the same electrode may also overlap in time. For example, the controller may sense both temperature and impedance from the same electrode simultaneously. The controller may sense temperature, impedance, and ECG substantially simultaneously, if the sampling rate allows. For example, the sampling rate may be greater than 5 samples / second. Alternatively, for example, the sampling rate may be greater than 10 samples / second. Alternatively, for example, the sampling rate may be greater than 20 samples / second. Alternatively, for example, the sampling rate may be greater than 100 samples / second.

[0125] Another advantage of using a 360 degree, or nearly 360 degree, conductive band for these types of sensors is the following:

[0126] Each sensor's impedance / conductivity sensor (typically consisting of two electrode rings, but may consist 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 rings. For example, when the two rings of the impedance / conductivity sensor are in contact with the stomach wall, the stomach wall tissue is only in contact with one side of the feeding tube—that is, one side of the electrode rings. The sensor senses the high conductivity / low impedance of this contact with the stomach wall tissue, even though 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.

[0127] Alternatively, each temperature sensor may be a thermocouple bonded to a 360-degree electrode or conductive ring. This bonding effectively means that the thermocouple senses the average temperature around the circumference of the ring. When the feeding tube, or temperature sensor, is pressed against the tissue, the temperature sensor senses the average temperature of the tissue and the surrounding environment around the rest of the ring. This allows the temperature sensor to detect breathing in the respiratory system even when the feeding tube is pressed against the wall of the respiratory system, avoiding false positives. Thus, a temperature sensor using a 360-degree ring is essentially an environment-averaging sensor.

[0128] By using the same electrodes for both types of sensors, the system can sense both tissue contact (switching to conductivity / impedance sensing) and the thermal environment (switching to temperature sensing), and the controller can switch between the two depending on the current need and the location of the particular sensor.

[0129] The control unit can 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 can be 30 kHz and 100 μA (peak-to-peak). Temperature measurements can be obtained using a copper / constantan thermocouple (type T) thermally bonded to one of the electrode rings. This design solution allows for 360-degree sensing, facilitating true impedance and temperature measurements, even in the presence of intermittent tissue contact and other confounding factors. The sensor locations are designed to accurately classify the device's anatomical location based on each sensor's measurement of the local environment. The gastric access device can be designed with different lengths to ensure optimal sensor spacing, based on the clinical nose-ear-middle-lower (NEMU) method, which is commonly used to determine insertion depth to ensure optimal final placement of the sensor within the patient's upper gastrointestinal (GI) tract. Impedance and temperature data can be delivered to the control unit in real time via a secondary, non-fluid-contacting lumen. The sensor data may be analyzed by the controller for two different functions: placement (monitoring the device's position upon insertion or periodically) and gastric status (determining, for example, GRV gastric emptying during feeding).

[0130] The placement function uses two simultaneous analyses 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, respiratory system, etc.

[0131] The thermal pattern recognition function evaluates the temperature data from sensors T1 and T2 at a rate of approximately 5 Hz and is able to detect misplacement of the device within the airway by identifying and classifying successive local maxima and minima (LMMs). Once the thermal pattern recognition function recognizes a pattern in the LMMs representative of two respiratory cycles (typically occurring within 2-4 seconds in infants and longer in adults), a positive determination of airway misplacement is made.

[0132] Simultaneously with or in parallel to temperature analysis, the placement function continuously or intermittently evaluates impedance measurements along the device. Typically, impedance measurements in the stomach are 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 that can ensure proper placement even in the presence of confounding factors such as intermittent tissue contact or gas bubbles in the stomach.

[0133] [Table 2] Note that although a 350 Ω cutoff is shown, the cutoff may be in the range of approximately 350 Ω to 400 Ω. Alternatively, the cutoff may be in the range of approximately 350 Ω to 450 Ω. Alternatively, the cutoff may be in the range of approximately 350 Ω to 500 Ω. Alternatively, the cutoff may be in the range of approximately 350 Ω to 650 Ω. Alternatively, the cutoff may be in the range of approximately 300 Ω to 400 Ω.

[0134] The gastric status function calculates the patient's real-time gastric content composition based on: (1) impedance measurement of the patient's empty stomach before feeding (this measurement can be performed using one or more distal-most electrode pairs); (2) impedance measurement of the compounded drug (sensed using an internal sensor in the device lumen); (3) real-time average impedance value in the stomach (sensed using one or more distal-most electrode pairs); and (4) selection of an appropriate calibration curve from a library. Changes in gastric content composition pattern characteristics can be evaluated using both time series and latent variable trend analysis over 4-, 8-, 12-, and 24-hour windows to provide automatic feedback on gastric status. Different status categories include: 1) optimized feeding; 2) low risk of feeding intolerance (progress feeding if calorie goals are not met); and 3) high risk of feeding intolerance (reduce feeding if clinical signs of feeding intolerance are present).

[0135] The placement and gastric status functional outputs are visually displayed on the control unit, providing real-time feedback to clinical staff. The reusable, pole-mounted control unit includes a user interface display, can be powered from a standard outlet, and can include an internal battery supporting over 12 hours of continuous function. For initial device placement, the operator receives notifications such as: (1) orange esophagus: "Device distal tip is in the esophagus. Continue advancement." (2) red lung: "Device distal tip is in the airway. Retract." (3) green stomach: "Device distal tip is properly positioned in the stomach." Once the stomach is properly positioned, the gastric status function on the control unit continuously monitors digestive changes and automatically provides feedback on optimal feeding strategies: 1) optimized feeding; 2) low risk of feeding intolerance (advance feeding); or 3) high risk of feeding intolerance (reduce feeding).

[0136] In some cases, users may introduce medications through the feeding lumen of a feeding tube. This medication may be in the form of crushed tablets or other bulky substances. The feeding lumen of a feeding tube can often become blocked by the added medication, making it difficult to unblock. An anti-clogging mechanism can be used in conjunction with a gastric access device or any feeding tube to prevent large particles of medication from entering the feeding tube.

[0137] FIG. 30A illustrates a medication delivery attachment that can be used with any feeding tube. Medication grinder 3002 includes a rotating segment 3006 and a sheath 3008. Medication 3004, such as a tablet, is introduced into a cavity within rotating segment 3006. Teeth or other grinding mechanisms (not shown) communicate with the cavity. Rotating the sheath after the tablet enters the cavity prevents the medication from leaving the attachment. The two rotating segments subsequently rotate relative to one another to grind the medication into particles large enough to enter the feeding lumen of the feeding tube without clogging the feeding tube. The grinding mechanism may resemble a pepper grinder. In some embodiments, the grinding action may be a ratcheting action, whereby the medication is ground only when the segments are rotated in one direction and not when rotated in the opposite direction, again similar to a pepper grinder.

[0138] As shown in FIG. 30B, the grinder attachment 3002 is connected to a feeding tube or gastric access device.

[0139] FIG. 30C illustrates another example of an anti-clogging mechanism. This introducer attachment 3010 includes a limiter, filter, cutter, or the like to prevent large boluses of medication from entering the feeding tube. As shown in FIG. 30C, the filter may be in the form of a wire mesh or cloth 3012. A wire filter may be made of stainless steel wire having a diameter of 0.003 inches (approximately 76.2 μm). FIG. 30D illustrates an introducer attachment 3010 including a constriction 3014 according to one embodiment. This constriction prevents boluses of medication from entering the feeding tube. If the boluses of medication within the feeding tube are larger than the diameter of the constriction 3014, they will not be introduced into the feeding tube. The constriction 3014 has a diameter smaller than the diameter of the feeding tube's feeding lumen.

[0140] Other embodiments of the anti-clogging mechanism may include sharp blades to cut off any large chunks of medication that are extruded through the opening.

[0141] As shown in FIG. 30E, the introducer attachment 3010 is connected to a feeding tube or gastric access device.

[0142] 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 utilized for automated control of the controller. For example, patients with high 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 severity and / or frequency of reflux events. Contextual reflux information may also determine whether the expandable member is expanded during a suction event. Contextual nutrition, GRV, and positioning information may also be used in this manner.

[0143] In some embodiments, the gastric access device can use electrodes along the device to sense passive electrical signals generated in the stomach wall. These signals can be used to assess gastric health, such as peristalsis.

[0144] GRV / gastric emptying can be tracked over time by the system by introducing an additional element with a measurable parameter. In this case, the parameter is at a different level from the level of stomach contents. The parameter level is sensed by a sensor in the feeding tube, and its changes are analyzed over time to determine GRV / gastric emptying. For example, a fluid with a lower conductivity than the stomach contents (e.g., a nutritional feed) can be introduced into the stomach in a single bolus, multiple times, continuously, or over time. The sensor along the gastric access device can be a conductivity / impedance sensor, and the conductivity / impedance along the device can be sensed over time to determine GRV / gastric emptying. Other parameters, such as temperature, pH, chemical content, and optical parameters, can also be used.

[0145] In some embodiments, a sensor is also present within the additive component delivery lumen of the device (which may be the feeding lumen or a separate lumen). This one or more sensors may measure a parameter of the additive prior to its addition to the stomach, thereby allowing the additive parameter level to be known before it 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 be present within the feeding lumen of the device to measure the conductivity / impedance of the additive (which may be the feeding lumen) just before it 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 to accurately determine the change in the parameter due to GRV / gastric contents. This inner lumen sensor may be considered a "calibration sensor."

[0146] In some embodiments, the controller switches to a feeding mode to monitor GRV upon detecting a feeding supply or liquid in the feeding lumen of the device.

[0147] When the gastric access device is in feeding mode, it can be in different states: 1) feeding is optimized; 2) there is a low risk of feeding intolerance (if calorie goals are not being met, feed is increased); or 3) there is a high risk of feeding intolerance (if clinical signs of intolerance are present, feed is decreased). In some embodiments, the gastric access device can measure the % food-to-gastric fluid concentration in the stomach over time based on measuring a parameter of the additive (in this case, food). These embodiments may include a calibration sensor.

[0148] In some embodiments, digestive health can be assessed by providing a bolus of additives and tracking GRV / gastric emptying immediately after the bolus. The GRV / gastric emptying profile can be compared to profiles of healthy and unhealthy individuals and / or populations to determine the health status of a particular patient. For example, a bolus containing a high concentration of glucose can be used and GRV / gastric emptying after the bolus can be monitored. Other indicators, such as blood glucose levels, can also be monitored.

[0149] 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.

[0150] Data Processing System Example FIG. 31 is a block diagram illustrating a data processing system that can be used in any embodiment of the present invention. For example, system 3100 may be used as part of the controller / monitor disclosed herein. While FIG. 31 illustrates various components of a computer system, it is not intended to represent a particular architecture or manner of interconnecting the components, and therefore such details are not relevant to the present invention. It will also be understood that network computers, handheld computers, mobile devices, tablets, mobile phones, and other data processing systems having fewer components, or perhaps more components, may also be used in conjunction with the present invention.

[0151] As shown in Figure 31, computer system 3100, which is one embodiment of a data processing system, includes a bus or interconnect 3102 coupled to one or more microprocessors 3103 and ROM 3107, volatile RAM 3105, and non-volatile memory 3106. Microprocessor 3103 is coupled to cache memory 3104. Bus 3102 interconnects these various components and also interconnects these components 3103, 3107, 3105, 3106 to display controllers and display devices 3108, as well as input / output (I / O) devices 3110, which may be mice, keyboards, modems, network interfaces, printers, and other devices known in the art.

[0152] Typically, input / output devices 3110 are coupled to the system via input / output controller 3109. Volatile RAM 3105 is typically implemented as dynamic RAM (DRAM), which requires continuous power to refresh or maintain data in memory. Non-volatile memory 3106 is typically a magnetic hard drive, magneto-optical drive, optical drive, or DVD-RAM or other type of memory system that retains data after power is removed from the system. Typically, non-volatile memory will also be random access memory, although this is not required.

[0153] While FIG. 31 illustrates the non-volatile memory as a local device directly coupled to the remaining components of the data processing system, the present invention may also utilize non-volatile memory that is remote from the system; for example, it may utilize a network storage device coupled to the data processing system via a network interface, such as a modem or Ethernet interface. Bus 3102 may include one or more buses connected to each other through various bridges, controllers, and / or adapters, as is known in the art. In one embodiment, I / O controller 3109 includes a USB (Universal Serial Bus) adapter for controlling USB peripherals. Alternatively, I / O controller 3109 may include an IEEE-1394 adapter, also known as a FireWire® adapter, for controlling FireWire® devices.

[0154] 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.

[0155] 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 clear from the above discussion, unless specifically stated otherwise, throughout this specification and in the following claims, discussions utilizing terms such as those set forth in the claims will be understood to refer to the acts and processes of a computer system or similar electronic computing device that manipulate and transform data represented as physical (electronic) quantities in the computer system's registers and memory into other data similarly represented as physical quantities in the computer system's memory or registers, or other such information storage, transmission, or display device.

[0156] The illustrated techniques may be implemented using code and data stored in and executed by one or more electronic devices. Such electronic devices may store and communicate (internally and / or with other electronic devices over a network) the code and data using 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 transient computer-readable transmission media (e.g., electrical, optical, acoustical, or other forms of propagated signals—carrier waves, infrared signals, digital signals, etc.).

[0157] The processes or methods depicted in the foregoing figures may be performed by processing logic comprised of 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 in terms of several sequential operations, it should be understood that some of the described operations may be performed in a different order. Furthermore, some operations may be performed in parallel rather than sequentially.

[0158] All embodiments disclosed herein may incorporate features of other embodiments disclosed herein.

Claims

1. a gastric access device having a longitudinal portion; a controller in communication with the gastric access device; one or more impedance or conductivity sensors disposed along the longitudinal portion, at least one impedance or conductivity sensor disposed at or proximate to a distal end of the longitudinal portion, each of the one or more impedance or conductivity sensors in communication with the controller, the controller configured to receive a first signal indicative of an impedance level or a conductivity level of a fluid within the subject's body in contact with the one or more impedance or conductivity sensors; one or more temperature sensors disposed along the longitudinal portion and in communication with the controller, the controller being further configured to receive a second signal associated with respiration and indicative of a temperature level of an environment within the subject's body in contact with the one or more temperature sensors; Equipped with A feeding tube system, wherein the control unit is configured to receive the first signal, detect whether or not there is a fluctuation in the second signal, and determine whether the gastric access device is positioned in the stomach of the subject based on both the first signal and the second signal.

2. the at least one impedance or conductivity sensor, and the one or more The system of claim 1 , wherein at least one of the temperature sensors comprises a common electrode.

3. The system of claim 2 , wherein the common electrode surrounds a periphery of the gastric access device.

4. The system of claim 1 , wherein the one or more temperature sensors include at least one sensor located at or proximate to the distal end of the longitudinal portion.

5. The system of claim 4 , further comprising at least one second temperature sensor disposed along the longitudinal portion and proximal to the at least one sensor.

6. The system of claim 1 , wherein the control unit is further configured to receive the second signal and detect fluctuations in the temperature level due to the respiration.

7. The system of claim 1 , wherein the control unit is further configured to receive the second signal and determine an average value of the temperature level due to the respiration.

8. The system of claim 1 , wherein the second signal is indicative of the temperature level of air associated with breathing within the subject.

9. The system of claim 1 , wherein at least one of the one or more temperature sensors is configured to sense an ambient temperature outside the subject.

10. The system of claim 9 , wherein the controller is further configured to compare the second signal to the ambient temperature.

11. The system of claim 1 , wherein the control unit is further configured to monitor gastric conditions within the stomach.

12. The system of claim 11 , wherein the control unit is configured to determine a volume of gastric residue in the stomach.

13. The system of claim 11 , wherein the control unit is configured to detect gastric reflux.

14. The system of claim 1 , wherein the first signal is indicative of the impedance or conductivity level of the fluid in the stomach.

15. 15. The system of claim 14, wherein the controller is configured to confirm placement within the stomach when the first signal exhibits a higher conductivity or lower impedance than the impedance or conductivity of an esophageal environment.

16. 10. The system of claim 1, wherein the gastric access device is sized for placement distal to the pylorus of the stomach.

17. 10. The system of claim 1, wherein the impedance or conductivity sensor includes electrodes, and the controller is further configured to monitor for dislodgment or bending of the longitudinal portion based on a comparison of a signal between two of the electrodes.

18. The system of claim 1 , wherein the control unit is further configured to indicate a pause in advancement of the gastric access device into the subject.

19. 20. The system of claim 18, wherein the control is further configured to indicate the pause for at least one second.

20. 10. The system of claim 1, further comprising an anti-clogging mechanism positioned proximate the opening of the gastric access device.

21. The system of claim 1 , wherein the one or more temperature sensors are at least two temperature sensors each positioned circumferentially opposite one another along the longitudinal portion.

22. 22. The system of claim 21, wherein the two temperature sensors are positioned circumferentially 180 degrees apart along the longitudinal portion.

23. The system of claim 1 , wherein the one or more temperature sensors are at least two temperature sensors each positioned at a different location from one another along the longitudinal portion.

24. The system of claim 1 , wherein the one or more temperature sensors are at least two temperature sensors each positioned circumferentially opposite one another at different locations along the longitudinal portion.

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