WO2023186303A1

WO2023186303A1 - A feeding device and method for determining a location of a feeding tube

Info

Publication number: WO2023186303A1
Application number: PCT/EP2022/058541
Authority: WO
Inventors: Sencha Arvid VAN KINDEREN; Stefanus Hendrikus Hubertina GRASSERE; Bram Zuijderduin; Duncan STANTON; Annamarie STANTON; Bert VISSER; Hendrik Hartholt
Original assignee: N.V. Nutricia
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2023-10-05

Abstract

Described is a feeding device, feeding system and method for determining a location of a feeding tube. In particular, the invention relates to a feeding device and method determining a location of a distal end of the feeding tube based on a pressure correlation between respective pressures measured by a distal end pressure sensor and another pressure sensor located further to a proximal end of the tube.

Description

A feeding device and method for determining a location of a feeding tube

The invention relates to a feeding device, feeding system and method for determining a location of a feeding tube. In particular, the invention relates to a feeding device and method for determining a location of a distal end of the feeding tube based on a pressure correlation between respective pressures measured by a distal end pressure sensor and another pressure sensor located further to the proximal end of the tube.

Feeding devices, particularly for enteral feeding of a patient, comprise a feeding tube that is inserted into the stomach of the patient, in order to provide a nutrition into the stomach of the patient. Such tubes are usually placed via the nasogastric route, through the nose of the patient (nasogastric tube) and stay there for a few days up to several weeks. It is important that the tube is placed correctly, in order to avoid enteral nutrition to enter a different part of the patient besides the stomach. Particularly, it is important that the tube is not misplaced, for example, into the lungs or bronchia of the patient. Once the tube is placed it is important to check the correct position of the tube each time before feeding is started, as to confirm the tube is not dislocated, for example, the distal end of the tube lying in the oesophagus or the small intestine.

The correct placement of a feeding tube is usually confirmed using x-ray techniques, so that an x-ray image can be captured showing the stomach and the distal end of the feeding tube in the correct position. Alternatively or additionally, aspirates gastric acid from the stomach can be pulled through the tube using a syringe and measuring the pH value of the gastric fluid (usually pH <= 5.5).

However, x-ray techniques are expensive, time intensive and further potentially dangerous to the patient due to the exposure of radiation multiple times during enteral feeding. Moreover, a wrong interpretation by a non-trained carer may also be disadvantageous in case of x-ray techniques as well as pulling gastric fluid from the stomach and performing a pH measurement.

It is therefore an object of the invention to provide a feeding device and method for reliably determining a location of a feeding tube in a patient in an efficient and cost- effective manner. This object is solved by a feeding device with the features of claim 1, a method with the features of claim 9, and a feeding system with the features of claim 13.

Preferred embodiments are defined by the dependent claims.

According to a first exemplary aspect to better understand the present disclosure, a feeding device comprises a feeding tube for inserting into a patient and having at least one lumen extending from a distal end to a proximal end of the tube, a first pressure sensor disposed in proximity to the distal end of the feeding tube and configured to measure a pressure acting on the tube, a second pressure sensor disposed in the feeding tube and configured to measure a pressure acting on the tube, wherein the second pressure sensor is further away from the distal end of the tube in a longitudinal direction of the tube than the first pressure sensor, and a controller.

The feeding device relies on pressure signals (pressure values) derived from sensors located in the feeding tube, particularly at its distal end as well as further to the proximal end of the tube. Thus, the patient and carer (or clinician) are relieved from capturing x-ray images each time the correct location of the feeding tube is to be confirmed. Likewise, no gastric fluid is to be removed from the stomach (pulled through the feeding tube), which increases the comfort of the patient. The use of pressure sensors is also cost and time effective compared to the employment of x- ray technology. Furthermore, since the first and second pressure sensors form part of the feeding tube, a periodic (or continuous) confirmation of the location of the feeding tube can be performed. This allows confirming the location of the tube during insertion into the patient as well as checking whether the feeding tube has moved over time, although it was initially correctly placed with its distal end in the stomach. For instance, due to peristalsis of the oesophagus, the stomach and/or the small intestine or movement of the patient the feeding tube may move, so that its distal end may not be located in the stomach, but in the oesophagus or small intestine, which can lead to discomfort of the patient due to nutrition being fed to the oesophagus (aspiration) or small intestine instead of the stomach. In the present disclosure, reference is made to the distal end of the feeding tube, since this usually has a feeding tube opening, i.e., an opening in the tube to the lumen, through which the nutrition flows out and (preferably) into the stomach. As an example, the tube can be cut, so that the lumen opens at the distal end of the tube. It is to be understood that the opening in the feeding tube may not be at the very distal end of the tube, but can be provided at a small distance therefrom. Thus, any reference to the distal end and the determination of its location in the patient's body is interchangeable with the feeding tube opening and determination of the location of this opening.

In order to determine a correct placement of the feeding tube in the stomach of the patient, the controller is configured to receive a signal from the first pressure sensor and the second pressure sensor, calculate a pressure correlation between a respective pressure measured by the first and second pressure sensors based on the received signals, and determine a location of the distal end of the tube in the patient based on the calculated pressure correlation. Due to the respective location of the first and second pressure sensors along the longitudinal direction of the feeding tube the first and second pressure sensors will measure the same or a different pressure depending on their location within the patient. For instance, while a pressure in the oesophagus, stomach and small intestine is most likely different with respect to one another, a pressure in the trachea, bronchia and lungs is most likely distinctive and unambiguous. By contemplating a pressure correlation between the pressures measured by the first and second sensors, it can easily be derived whether the distal end of the feeding tube is located within the stomach, i.e. the feeding tube is correctly placed.

It is not necessary to achieve any particular skills for operating the feeding device, i.e., no particular skills are needed for reading and interpretation of the sensor values, since the controller determines an indication of a correct or incorrect location of the distal end of the feeding tube. For instance, there is no need for the patient or carer to operate particular instruments (e.g., for pulling gastric fluid from the stomach) or to operate particular devices, such as x-ray, ultrasound or the like.

In an implementation variant, the controller can be configured to calculate the pressure correlation by calculating an absolute pressure value of the first pressure sensor and an absolute pressure value of the second pressure sensor at the same measurement time. The controller can then determine the location of the distal end to be a stomach of the patient, if the absolute pressure values of the first and second pressure sensors are approximately equal and the pressure signals from the first and second pressure sensors indicate inverse pressures at the first and second pressure sensors. For instance, the pressure measured by the first sensor can be a positive pressure and the pressure measured by the second sensor can be a negative pressure of approximately same value as the positive pressure of the first sensor. Approximately the same or approximately equal in the present disclosure means that the respective values are equal or vary in the range of +/- 10%, preferably in the range of +/- 5 %. For instance, if the absolute value of the first sensor is 15 mmHg, the absolute value of the second sensor can be between 13.5 % and 16.5%, preferably between 14.25% and 15.75%. It is to be understood that the pressure value of the second pressure sensor can be negative. Likewise, at the same measurement time means approximately at the same time, i.e. within a time window of -0.5 to +0.5 seconds. Moreover, there can be an overall difference of 10 mmHg between the oesophagus and an empty stomach, particularly, if the stomach is empty.

In case the feeding tube is correctly placed in the patient, i.e. the distal end of the tube is located in the stomach, the breathing of the patient will induce an inverse pressure pattern in the stomach and the oesophagus, which are usually separated by the diaphragm. Thus, if the first pressure sensor is located with the distal end of the tube in the stomach, while the second pressure sensor is located in the oesophagus, the pressure signals measured by these sensors will indicate absolute pressures of approximately the same value at the same measurement time, but of opposite algebraic sign. This is particularly relevant when natural ventilation is present. Mechanical ventilation of a person may lead to different results.

Alternatively, the controller may determine that the absolute pressure values of the first and second pressure sensors are not the same, but a pressure difference can be calculated. If, however, the pressure profiles of the first and second pressure sensors show inverse pressure patterns having different amplitudes, the controller can still determine that the distal end of the tube is located in the stomach, while the second pressure sensor is located in the oesophagus.

It is to be understood that, for any of the implementation variants described herein, the distance between the first and second pressure sensor along the longitudinal direction of the feeding tube has to be sufficient for the first sensor to be placed in the stomach and the second sensor to be placed in the oesophagus. For instance, a distance between the first and second pressure sensors can be between 3 to 50 cm, preferably between 8 and 25 cm for adults. For infants and neonatal patients this distance is to be chosen shorter as the organs are smaller.

Alternatively or additionally, the second pressure sensor may not be a single sensor, but a plurality of sensors disposed along the tube. For instance, all sensors (including the first and any of the second sensors) can be arranged along the tube beginning at any portion of the tube and ending at the distal end of the tube (with the first pressure sensor). Thus, the first pressure sensor and one or more of the "second" pressure sensors can be located in the stomach, while the next sensor along the tube towards the proximal end will be arranged in the oesophagus. The controller can still determine the inverse pressure profiles of the first pressure sensor and one of the second pressure sensors, in order to determine a correct placement of the feeding tube. This can be confirmed by calculating a pressure correlation between the first pressure sensor and the "second" pressure sensor/s, which should all be located in the stomach, and of which the latter should have a pressure profile approximately equal to the pressure profile of the first pressure sensor.

In another implementation variant, the controller can be configured to calculate the pressure correlation by determining (or calculating) a pressure difference between the respective pressure measured by the first and second pressure sensors. Thus, a simple subtraction of the pressure values (or the absolute pressure values) measured by the first and second pressure sensors can be calculated.

Alternatively or additionally, the controller can be configured to calculate the pressure correlation by determining (or calculating) a frequency of pressure peaks measured by the first or second pressure sensor. In other words, the controller can be configured to identify two or more pressure peaks of the pressure measured by the first or second pressure sensor and derive the frequency of these pressure peaks. For instance, the frequency can be defined by the time period between two subsequent pressure peaks, i.e. pairwise subsequent pressure peaks.

Also alternatively or additionally, the controller can be configured to calculate the pressure correlation by determining a time lag between a pressure peak measured by the first pressure sensor and a pressure peak measured by the second pressure sensor. Thus, a timely correlation is determined between pressure peaks of the first and second sensors. Preferably, such timely correlation can be based on respective pressure peaks of the first pressure sensor and the second pressure sensor directly following one another, i.e. without a further pressure peak within the determined time lag. Of course, it is further possible that only pressure peaks of same algebraic sign are considered.

Further alternatively or additionally, the controller can be configured to calculate the pressure correlation by determining a sudden and unexpected value of at least one of the first and second pressure sensors. For instance, if one or both of the pressure sensor deliver a value that is above or below a threshold, a dislocation of the tube can be identified.

In any case, the controller can be configured to determine the location of the distal end based on the determined pressure difference, and/or the determined frequency, and/or the determined time lag. In other words, the pressure correlation takes into consideration the pressure difference and/or the frequency of pressure peaks of one or both sensors and/or the time lag between pressure peaks of both sensors.

In a further implementation variant, the controller can be configured to determine the location of the distal end to be a stomach of the patient, if the time lag is less than a threshold value or zero and the pressure difference is less than a threshold value or zero, while the pressure signals of the first and second pressure sensors indicate inverse pressures. This pressure correlation corresponds to the above implementation variant identifying a breathing pattern due to inverse pressure profiles derivable from the oesophagus and stomach.

In yet a further implementation variant, the controller can be configured to determine the location of the distal end to be a stomach of the patient, if the pressure difference is above a threshold value, wherein preferably the pressure measured by the first pressure sensor is greater than the pressure measured by the second pressure sensor. There is usually a pressure difference between the oesophagus and stomach, particularly if the stomach is empty. For instance, the pressure in the stomach can be greater than in the oesophagus. As an example only, the pressure difference can be between 5 to 20 mmHg, preferably 7 and 13 mmHg, and most preferably 10 mmHg.

In a further implementation variant, the controller can be configured to determine the location of the distal end to be a stomach of the patient, if the frequency of pressure peaks of the first pressure sensor is about 2.0 to 3.7 peaks per minute, preferably 2.5 to 3.2 peaks per minute. For instance, the stomach of a patient usually contracts frequently, particularly if the stomach is full (e.g., after feeding). Such stomach contractions can be identified by the regular pressure peaks, i.e. via the frequency of pressure peaks of the first pressure sensor.

In another implementation variant, the controller can be configured to determine the location of the distal end to be an oesophagus of the patient, if the time lag is greater than a threshold value, wherein the threshold value is between 0.5 and 20 seconds, and preferably between 1 and 8 seconds. In other words, pressure peaks can be identified at the second pressure sensor and shortly after at the first pressure sensor, if both pressure sensors are arranged in the oesophagus and the patient swallows. The peristalsis of the oesophagus, particularly between the upper and lower oesophageal sphincter, moves towards the stomach, so that each pressure sensor will output a pressure signal identifying a pressure peak with a time delay (time lag) depending on the swallow pattern in the oesophagus.

It is to be understood that the time lag depends on the distance between the first and second pressure sensor or in case of more than two sensors, the distance between each adjacent pair of sensors. For instance, a usual velocity of the peristalsis in the oesophagus is approximately 3 to 4 cm/s. Having a preferred distance between the first and second pressure sensors of 10 to 25 cm, the time lag of the pressure peaks of the first and second sensors is approximately 2.5 to 8 seconds.

Furthermore, the controller can be configured to determine the location of the distal end to be the stomach of the patient, if the time lag is greater than the above-described threshold value, and a pressure drop at the first pressure sensor can be identified shortly before the pressure peak of the first pressure sensor used for calculating the time lag. The swallow pattern along the oesophagus may be identified by pressure peaks usually starting from a baseline, while the pressure in the stomach decreases before having a flattened pressure peak when the peristalsis arrives at the lower oesophageal sphincter.

Thus, a pressure correlation between the second and first pressure sensor due to a swallowing of the patient can be used to determine the location of the distal end to be the oesophagus or the stomach.

In yet another implementation variant, the controller can be configured to determine the location of the distal end to be a lung (or trachea or bronchia) of the patient, if the pressure difference is less than a threshold value and the pressure peaks of the first and second pressure sensors are both of a positive value or are both of a negative value, wherein preferably the threshold value is between 0.5 and 6 mmHg and most preferably between 0.5 and 2 mmHg. Specifically, if the pressure peaks are measured at approximately the same time and the respective pressure values are both positive or both negative, it is very likely that the feeding tube has been placed into the trachea, bronchia or lung, which are all fluidly connected to one another. Thus, during inhale and exhale the pressure measured by the first and second sensors will be of approximately the same value and will both be negative or positive, respectively. In a further implementation variant, the feeding device can further comprise at least one wire electrically connecting the first pressure sensor and/or the second pressure sensor with the controller. Alternatively or additionally, the feeding device can further comprise at least one optical fibre optically connecting the first pressure sensor and/or the second pressure sensor with the controller. The wire and/or optical fibre can be embedded in the material of the tube, so that the wire is protected by the tube material. It is to be understood that the first and second pressure sensor can be connected to the controller by a respective wire/fibre or by a single wire/fibre.

In another implementation variant, the feeding device can further comprise a second lumen fluidly connecting the first pressure sensor and/or the second pressure sensor with an ambient atmosphere of the feeding device. This allows the first and/or second pressure sensor to operate relative to an ambient atmospheric pressure.

For instance, the first and/or second pressure sensor can be a differential pressure sensor, one side of which is in fluid communication with the ambient atmosphere via the second lumen. The opposite side of the pressure sensor can face an outer circumference of the feeding tube, i.e. can face the patient's tissue surrounding the feeding tube, such as the oesophagus, stomach, trachea, etc.. Thus, a pressure in a void inside the patient can act onto the differential pressure sensor and the ambient atmosphere via the second lumen. This allows accurate measurement of all sensors in the feeding tube with respect to the same base pressure, i.e. the ambient atmospheric pressure.

In yet another implementation variant, the first and/or second pressure sensor is at least partially enclosed in a housing having a greater rigidity than the feeding tube. Such pressure sensor provides better protection of the actual sensing element and avoids bending stress from the tube influencing the pressure measurement, for example, by bending the pressure sensor/element itself.

In a further implementation variant, the feeding device can further comprise a feeding pump configured to pump a nutrition into the first lumen at or near the proximal end. The feeding pump can be connected to the first lumen via a usual connector, such as a Luer-lock connector or an ENFit-connector (according to ISO80369-3). Optionally, a reservoir can be connected via a giving set, which is connected to the feeding tube via an ENFit connector. To move the nutrition product from the reservoir to the patient, a pump insert is part of the giving set. The pump insert is placed in the pump to start pumping. According to a second exemplary aspect to better understand the present disclosure, a method for determining a location of a feeding tube comprises at least the following steps:

- inserting a feeding tube into a patient, wherein the feeding tube has at least one lumen extending from a distal end to a proximal end of the tube;

- receiving a signal from a first pressure sensor disposed in proximity to the distal end of the feeding tube;

- receiving a signal from a second pressure sensor disposed in the feeding tube and configured to measure a pressure acting on the tube, wherein the second pressure sensor is further away from the distal end of the tube in a longitudinal direction of the tube than the first pressure sensor; and

- calculating a pressure correlation between a respective pressure measured by the first and second pressure sensors based on the received signals; and

- determining a location of the distal end of the tube in the patient based on the calculated pressure correlation.

The method can be performed by employing a feeding device, for example, the feeding device of the first aspect or one of its implementation variants.

In an implementation variant, said calculating the pressure correlation can comprise calculating an absolute pressure value of the first pressure sensor and an absolute pressure value of the second pressure sensor at the same measurement time, and said determining the location can comprise determining the location of the distal end to be a stomach of the patient, if the absolute pressure values of the first and second pressure sensors are approximately equal and the pressure signals from the first and second pressure sensors indicate inverse pressures at the first and second pressure sensors. Thus, the method allows identifying a breathing pattern due to inverted pressure profiles measured in the stomach and the oesophagus, i.e. on both sides of the diaphragm of the patient.

In a further implementation variant, said calculating the pressure correlation can comprise one or more of: - determining a pressure difference between the respective pressure measured by the first and second pressure sensors,

- determining a frequency of pressure peaks measured by the first or second pressure sensor, and - determining a time lag between a pressure peak measured by the first pressure sensor and a pressure peak measured by the second pressure sensor.

In this case, said determining the location can comprise determining the location of the distal end based on the determined pressure difference, and/or determined fre- quency, and/or determined time lag.

Furthermore, said determining the location can then comprise:

- determining the location of the distal end to be a stomach of the patient, if the time lag is less than a threshold value or zero and the pressure difference is less than a threshold value or zero, while the pressure signals of the first and second pressure sensors indicate inverse pressures,

- determining the location of the distal end to be a stomach of the patient, if the pressure difference is above a threshold value, wherein preferably the pressure measured by the first pressure sensor is greater than the pressure measured by the second pressure sensor, - determining the location of the distal end to be a stomach of the patient, if the frequency of pressure peaks of the first pressure sensor is about 2.0 to 3.7 peaks per minute, preferably 2.5 to 3.2 peaks per minute,

- determining the location of the distal end to be an oesophagus of the patient, if the time lag is greater than a threshold value, wherein the threshold value is between 0.5 and 20 seconds, and preferably between 1 and 8 seconds, or

- determining the location of the distal end to be a lung of the patient, if the pressure difference is less than a threshold value and the pressure peaks of the first and second pressure sensors are both of a positive value or are both of a negative value, wherein preferably the threshold value is between 1 and 6 mmHg and more preferably between 1 and 2 mmHg.

According to a second exemplary aspect to better understand the present disclosure, a feeding system comprises a feeding device according to the first aspect or one of its implementation variants, and an output device in communication with the feeding device and configured to provide an output signal indicating the determined location of the distal end of the tube.

For instance, the output device can be configured to provide a visual and/or audible signal about the location of the distal end of the feeding tube. The output device can indicate that the distal end of the feeding tube is placed in a portion of the respiratory system, the oesophagus or the stomach according to the determination of the controller of the feeding device.

Thus, even an untrained patient or carer can interpret the results from the controller once the feeding tube is placed, for example, through the nose and oesophagus (nasogastric tube), while the output device indicates whether the tube is located in the trachea or oesophagus and later in the stomach based on the pressure correlation identified by the controller of the feeding device. After correctly placing the feeding tube, the patient or carer can regularly identify via the output device whether the distal end of the tube is still located in the stomach. Alternatively or additionally, the output device may output an alarm, if the pressure correlation indicates a change of location of the distal end of the tube, such as being moved towards the small intestine or the oesophagus, or having been pulled into the oesophagus.

As an example only, the output device can be a small device, so that it is mobile and easy to use. For instance, a mobile telephone, tablet or similar computing device can be used to implement the output device. Of course, such computing device can also include a controller acting as the controller of the feeding device.

In an implementation variant, the feeding device, particularly the feeding tube, can further include another sensor configured to measure of pH value of the surrounding fluid. For instance, such pH sensor can be located at the distal end of the tube.

Based on the measured pH value, the location of the distal end in the stomach of the patient can be confirmed. This allows increasing the reliability of the feeding device.

In another implementation variant, the feeding device, particularly the first and/or second pressure sensor, can be configured to change an output signal if light and/or sound acts on the sensor. The controller can further be configured to determine a change of the pressure signal received from the first and/or second pressure sensor over a short period of time. This time period can be initiated by a user of the feeding device, for instance, when applying light or sound or (electro / mechanical) oscillations from outside of the patient, or automatically. As an example only, the output device may be equipped with a light emitting device and/or a sound emitting device, so that the feeding system, and particularly the controller, can be made aware of when light and/or sound is emitted from outside of the patient. If the controller determines a slight increase or decrease of the pressure value received from the first and/or second pressure sensor at the time light and/or sound has been emitted to- wards the patient, a pressure correlation can be determined. The user of such system at the output device and/or the controller can then identify the pressure difference, in order to confirm correct or incorrect location of the distal end of the feeding tube. For example, the user can hold the light and/or sound emitting device at a location of the abdominal wall corresponding to (close to) the stomach, so that light and/or sound impacts the first and/or second pressure sensor.

The present disclosure is not restricted to the aspects and variants in the described form and order. Specifically, the description of aspects and variants is not to be understood as a specific limiting grouping of features. It is to be understood that the present disclosure also covers combinations of the aspects and variants not explicitly described. Thus, each variant or optional feature can be combined with any other aspect, variant, optional feature or even combinations thereof.

Preferred embodiments of the invention are now explained in greater detail with reference to the enclosed schematic drawings, in which

Figure 1 schematically illustrates internal organs of a patient;

Figure 2 schematically illustrates a feeding device;

Figure 3 schematically illustrates a distal end of a feeding tube;

Figure 4 schematically illustrates a pressure correlation between spaced apart pressure sensors during swallowing;

Figure 5 schematically illustrates a flow diagram of a method identifying a proper feeding tube location, according to a breathing pattern;

Figure 6 schematically illustrates a flow diagram of a method determining a pressure correlation and proper feeding tube location; and

Figure 7 schematically illustrates a feeding system.

Figure 1 schematically illustrates internal organs of a patient 1, particularly organs of the respiratory system and the digestive tract. For enteral feeding a feeding tube should be placed with its distal end in a stomach 2, which can be reached through an oesophagus 3, for example via the nose (not shown) of the patient. Downwards the stomach 2 begins the duodenum 4 where the intestines start. When feeding through the stomach 2, the distal end of the feeding tube should not be placed in the duodenum 4, since the nutrition is made for stomach feeding, i.e. it should first be digested by the stomach 2 and not the intestine 4. Likewise, nutrition should not be fed into the oesophagus 3, since it may reflux towards the pharynx and throat of the patient 1 instead of being digested by the stomach 2. Both can be very uncomfortable for the patient 1. Furthermore, the nose is also connected to the respiratory system, particularly the trachea 5 and the lung 6. Thus, when placing the feeding tube through the nose, the tube may enter the trachea 5 instead of the oesophagus 3. This situation should be avoided, since providing nutrition through the feeding tube into the trachea 5 or lung 6 can be very dangerous for the patient. Figure 2 schematically illustrates an exemplary feeding device 50 for a better understanding of the present disclosure. The illustrated feeding device 50 comprises a feeding tube 100 to be inserted into the patient 1. The feeding tube 100 has at least one lumen 120 (Figure3) extending from a distal end 110 to a proximal end 105 of the tube 100. It is to be noted that the proximal end 105 may not end as illustrated in Figure 2, but can extend further along a longitudinal direction of the tube 100, even up to the controller 150.

The feeding device 50 further comprises a first pressure sensor 131 disposed in proximity to the distal end 110 of the feeding tube 100. The first pressure sensor 131 should be placed as close to the distal end 110 of the feeding tube 100 as possible, in order to measure a pressure in the direct surrounding of the distal end 110. The pressure sensor 131 is configured to measure a pressure acting on the tube 100 at a location corresponding to the first pressure sensor 131.

Furthermore, the feeding device 50 comprises a second pressure sensor 132 disposed in the feeding tube 100. The second pressure sensor 132 is located further away from the distal end 110 in a longitudinal direction of the tube 100 than the first pressure sensor 131. The second pressure sensor 132 is also configured to measure a pressure acting on the tube 100 at a location corresponding to the second pressure sensor 132.

Additional sensors can also be present along the tube 100 in the direction to the proximal end, which are not illustrated for clarity reasons.

The feeding device 50 can further comprise the controller 150 that is configured to receive a signal from the first pressure sensor 131 and a second pressure sensor 132. Based on these pressure signals the controller 150 calculates a pressure correlation of the respective pressure measured by the first and second pressure sensors 131, 132. The pressure correlation is then used by the controller 150 to determine a location of the distal end 110 of the tube 100 in the patient 1.

For example, the first and/or second pressure sensor 131, 132 can be connected with the controller 150 via at least one wire 135 or optical fibre 135. This wire or fi- bre 135 provides for an electrical or optical connection between the pressure sensor 131, 132 and the controller 150, respectively. Thus, the controller 150 can read pressure signals of each of the pressure sensors 131, 132 at any time.

Figure 3 schematically illustrates a distal end 110 of a feeding tube 100 in more detail. The portion of the feeding tube 100 illustrated in Figure 3 can be from the feed- ing tube 100 illustrated in Figure 2, so that the description of elements already explained with respect to Figure 2 are omitted. It is to be noted that the wire or fibre 135 has been omitted in Figure 3 for clarity reasons.

It is to be understood that the opening of the lumen 120 in the tube 100 is illustrated at the distal end 110 of the tube as one example only. The distal end 110 of the feeding tube 100 can be closed, while an opening (not illustrated) into the lumen 120 is formed at a lateral side of the tube 100. This allows nutrition to flow out of the tube 100 at a lateral side. In case a lateral opening is provided in the feeding tube 100 into lumen 120, the first pressure sensor 131 can be disposed in proximity to the lateral opening (instead of at the distal end 110. The first pressure sensor 131 should be placed as close to the opening of lumen 120 in the feeding tube 100 as possible, in order to measure a pressure in the direct surrounding of the opening.

The feeding device 50, particularly the feeding tube 100, can further comprise a second lumen 125 fluidly connecting the first and/or second pressure sensor 131, 132 with an ambient atmosphere of the feeding device 50. For instance, the second lu- men 125 may extend in a longitudinal direction of the tube 100 up to the controller 150 or at least to a portion of the tube 100 that will not be inserted into the patient 1.

This allows employing a differential pressure sensor as the first and/or second pressure sensor 131, 132. One side of such differential pressure sensor is in fluid commu- nication with the ambient atmosphere via the second lumen 125. In order to avoid the pressure of a void in the patient 1 to act on the pressure sensor/s 131, 132 from the second lumen 125, the second lumen 125 is closed at the distal end 110 of the tube 100, for example, at/with the first pressure sensor. The first lumen 120, on the other hand, has an open end at the distal end 110 of the tube 100. This allows feeding the patient 1 with nutrition through the first lumen 120.

The pressure correlation calculated by the controller 150 can reflect various natural pressures induced by the organs of the patient 1. A first example is illustrated with respect to Figure 4, which schematically illustrates a pressure correlation along an oesophagus 3 during swallowing. The oesophagus 3 includes (from top to bottom, i.e. from throat to stomach) the pharynx 11, the upper oesophageal sphincter 12, a junction of striated and smooth muscles 13, and the lower oesophageal sphincter 14 closing the entry into the stomach 2 (the stomach 2 is not illustrated in Figure 4).

Once the patient 1 swallows, the peristalsis (associated moving constriction of the oesophagus 3 due to muscle contractions) moves from top to bottom of the oesophagus 3. For instance, a bolus of food or salvia travels through the pharynx 11 in less than one second, as the pharyngeal peristalsis is very fast (up to 40 cm/s). The travel time of food or salvia through the oesophagus 3 is about 5 to 6 seconds (for an adult), with a velocity of the peristalsis of approximately 3 to 4 cm/s. As illustrated in Figure 4, such swallowing induces a pressure peak "moving" along an item placed in the oesophagus 3. If pressure sensors, such as the first and second pressure sensors 131, 132, are located in the oesophagus 3, pressure peaks can be measured at different locations along the oesophagus 3 as illustrated. At the lower oesophageal sphincter 14 as well as the stomach 3, the measured pressure decreases (drops) before reaching the pressure peak due to the opening of the lower oesophageal sphincter 14 (i.e. allowing a fluid communication between oesophagus and stomach). Thus, if the feeding tube 100 is arranged in the oesophagus 3, particularly the distal end 110 of the tube 100 still being located in the oesophagus 3, a pressure correlation can be calculated by the controller 150 based on the time lag (time difference between the pressure peaks of the pressure signals of the second pressure sensor 132 and (later) of the first pressure sensor 131). Likewise, if the distal end 110 of the tube 100 and, hence, the first pressure sensor 131 is located inside of the stomach 2, the controller 150 can identify the pressure decrease before reaching a pressure peak, while the pressure peak takes place after the time lag with respect to the pressure peak of the second pressure sensor 132 that is arranged in the oesophagus 3. The controller 150 can then calculate a pressure correlation that indicates the distal end 110 to be located in the stomach 2. A further exemplary pressure correlation will now be explained with respect to Figure 5, which schematically illustrates a flow diagram of a method identifying a proper feeding tube location, according to a breathing pattern. First, in step 210 it is confirmed whether the sensors 131, 132 are connected to the controller 150 and are functional. If they are not, the process ends. For instance, corresponding feedback can be provided to the user, including a failure message output to the user, to indicate malfunction of the feeding device 50.

Otherwise, both pressure sensors 131, 132 are initialized in step 222. Thereafter, a pressure signal is acquired in steps 224 to 228, for example, at a predefined sam- pling rate. As an example only, sampling can take place for about 10 to 30 seconds at a sampling rate frequency of 0.1 to 0.5 Hz. The pressure signal of each sensor 131, 132 can be transmitted to the controller 150, which receives such pressure signals at step 220. Thereafter, the controller 150 can calculate a pressure correlation based on the received signals. As an example only, in step 230, a frequency of pressure peaks of the first pressure sensor 131 as well as the second pressure sensor 132 can be derived from the signals received at step 220. In corresponding steps 235 a frequency can be compared to an expected frequency. For instance, a breathing of the patient 1 will induce a repeated pressure change in the stomach as well as the oesophagus 3, since both or- gans are close to the diaphragm and lungs 6 of the patient 1 and will be moved during breathing. Likewise, stomach contractions of a full stomach 2 take place regularly, so that a certain frequency of pressure peaks can be expected.

If no expected frequency is found, the controller 150 can determine that the tube 100 is incorrectly placed in step 238. For instance, the controller 150 can be config- ured to output a further feedback, such as an alarm or similar visual and/or audible signal.

If in step 235 an expected frequency is found, an optional signal conditioning can take place in step 240. For instance, an outlier selection, moving average, or bandpass filter may be applied. Also optionally, a trend analysis (e.g., a pattern recognition) can be performed by the controller 150 in steps 250 for each received pressure signal. Such trend analysis may include monitoring of the pressure value over time, particularly pressure peaks, duration of pressure peaks, a frequency of pressure peaks, etc.. Such trend analysis allows classifying the pressure signals, such as breathing, feeding, digesting, etc.. Thereafter, in step 260, a pressure correlation between respective pressures measured by the first and second pressure sensors 131, 132 is calculated. For example, the received and further processed pressure signals are compared to one another. This may include identification of certain patterns, which can be identified based on the trend analysis of step 250. Such patterns may be compared to one another (e.g., in step 260). As an example only, the pressure correlation may include calculating an absolute pressure value of the first and second sensors 131, 132 at the same measurement time, and a comparison of the absolute pressure values, particularly, whether both absolute pressure values are approximately equal. If, as illustrated in step 250 of Figure 5, the pressure signals from the first and second pressure sensors 131, 132 indicate inverse pressures at the first and second pressure sensors, inverse or reversed patterns may be identified in step 270. Since such inverse pressure patterns usually take place during breathing, the controller 150, in step 280, can determine a correct placement of the tube 100, particularly its distal end 110 being located in the stomach 2, while a portion of the tube 100 including the second pressure sensor 132 is located in the oesophagus 3.

Turning now to Figure 6, a flow diagram is schematically illustrated showing a method of determining a pressure correlation and proper feeding tube location. For instance, as in the method of Figure 5 pressure signals from the first and second pressure sensors 131, 132 may be received in step 220, for example at the controller 150.

To the left in Figure 6, a rather simple relative pressure correlation is calculated, by selecting and analysing samples in step 305, and measure or calculate a relative pressure difference between both sensors 131, 132 in step 307. Such pressure differ- ence may then be output in step 309 and can be analysed in step 320. For example, the relative pressure difference can be used to identify that the tube 100 is located incorrectly, such as in the trachea 5 or lungs 6 of the patient 1, if the pressure difference is approximately zero. On the other hand, a pressure difference of a certain level, such as approximately 10 mmHg is present between the oesophagus 3 and the stomach 2. Thus, the location of the first pressure sensor 131 in the stomach 2 and the second pressure sensor 132 in the oesophagus 3, and hence a correct location of the tube 100, can be identified.

Another pressure correlation may indicate a breathing pattern, a swallowing pattern or contractions of the stomach 2. In any case, a frequency of pressure peaks of the first and/or second pressure sensor 131, 132 is analysed in step 312, and particular samples of the received pressure signal are selected and analysed in step 314. Thereafter, in step 316, the pressure signals of the distal end sensor 131 and the proximal sensor 132, or vice versa, can be compared, in order to identify a breathing pattern and swallowing pattern. While the breathing pattern will have inverse pressure peaks in the oesophagus 3 and the stomach 2 due to the movement of the dia- phragm, the swallowing will induce a pressure as explained with respect to Figure 4.

Likewise, in step 316 pressure peaks can be compared to one another for any sensor located in the stomach 2, which indicates stomach contractions during digestion.

Thus, in step 318, a corresponding rhythmic pattern can be identified and provided to the controller 150 for analysing in step 320. This analysis may include weighing of the derived rhythmic patterns or pressure difference, for example, based on a preset or trained model. In any case, controller 150 can identify an incorrect tube placement in step 238 or a correct tube placement in step 280.

Figure 7 schematically illustrates a feeding system 75 that can comprise a feeding device 50, such as the device 50 illustrated in Figures 2 and 3. Such feeding device 50 can comprise the feeding tube 100 inserted into the patient 1 and a controller 150.

In addition, an output device 180 may form part of the feeding system 75. The output device 180 can include a display and/or speaker (not illustrated), in order to provide a visual and/or audible output to the patient 1 or a carer 185 (or clinician or the like). The controller 150 can be in communication 170 with the output device 180, in order to inform the patient 1 or carer 185 about the location of the distal end 110 of the tube 100. Such communication 170 can be a wireless communication (e.g., Bluetooth, WLAN, etc.) or a wired communication (USB, LAN, etc.).

Furthermore, based on the pressure correlation and determination of the location of the distal end 110, a visual and/or audible signal can be output at output device 180 indicating such location. This output indication can include specifying that the tube 100 is dislocated in the trachea 5 and/or lung 6, that the distal end 110 is dislocated in the oesophagus 3 or the duodenum 4, or that the distal end 110 is correctly located in the stomach 2. The feeding system 75 can further comprise a feeding pump 121 configured to pump nutrition into the first lumen 120 of the tube 100. Such pump 121 can be integrated into a device holding the controller 150 and/or can be integrated into the output device 180. Furthermore, the controller 150 can also be integrated into the output device 180 with or without the optional pump 121.

Moreover, the data output by the controller 150 can further be transmitted to an external device 190. Such external device 190 may be connected to the output device 180 and/or the controller 150 via a network. The external device 190 may be configured to analyse and/or store the data calculated and determined by the controller 150. The device 190 may be used by a doctor or clinic or developer of feeding devices 50, in order to monitor the patient 1 as well as the feeding device 50.

The above description of the drawings is to be understood as providing only exem- plary embodiments of the present invention and shall not limit the invention to these particular embodiments.

Claims

1. A feeding device (50) comprising: a feeding tube (100) for inserting into a patient (1) and having at least one lumen (120) extending from a distal end (110) to a proximal end (105) of the tube (100); a first pressure sensor (131) disposed in proximity to the distal end (110) of the feeding tube (100) and configured to measure a pressure acting on the tube (100); a second pressure sensor (132) disposed in the feeding tube (100) and configured to measure a pressure acting on the tube, wherein the second pressure sensor (132) is further away from the distal end (110) of the tube (100) in a longitudinal direction of the tube (100) than the first pressure sensor (131); and a controller (150) configured to:

- receive a signal from the first pressure sensor (131) and the second pressure sensor (132),

- calculate a pressure correlation between a respective pressure measured by the first and second pressure sensors (131, 132) based on the received signals, and

- determine a location of the distal end (110) of the tube (100) in the patient (1) based on the calculated pressure correlation.

2. The feeding device (50) according to claim 1, wherein the controller (150) is configured to:

- calculate the pressure correlation by calculating an absolute pressure value of the first pressure sensor (131) and an absolute pressure value of the second pressure sensor (132) at the same measurement time, and

- determine the location of the distal end (110) to be a stomach (2) of the patient (1), if the absolute pressure values of the first and second pressure sensors (131, 132) are approximately equal and the pressure signals from the first and second pressure sensors (131, 132) indicate inverse pressures at the first and second pressure sensors.

3. The feeding device (50) according to claim 1, wherein the controller (150) is configured to calculate the pressure correlation by:

- determining a pressure difference between the respective pressure measured by the first and⁴second pressure sensors (131, 132), and/or - determining a frequency of pressure peaks measured by the first or second pressure sensor (131, 132), and/or

- determining a time lag between a pressure peak measured by the first pressure sensor (131) and a pressure peak measured by the second pressure sensor (132), wherein the controller (150) is configured to determine the location of the distal end (110) based on the determined pressure difference, and/or determined frequency, and/or determined time lag.

4. The feeding device (50) according to claim 3, wherein the controller (150) is configured to:

- determine the location of the distal end (110) to be a stomach (2) of the patient (1), if the time lag is less than a threshold value or zero and the pressure difference is less than a threshold value or zero, while the pressure signals of the first and second pressure sensors indicate inverse pressures, - determine the location of the distal end (110) to be a stomach (2) of the patient (1), if the pressure difference is above a threshold value, wherein preferably the pressure measured by the first pressure sensor (131) is greater than the pressure measured by the second pressure sensor (132),

- determine the location of the distal end (110) to be a stomach (2) of the pa- tient (1), if the frequency of pressure peaks of the first pressure sensor (131) is about 2.0 to 3.7 peaks per minute, preferably 2.5 to 3.2 peaks per minute,

- determine the location of the distal end (110) to be an oesophagus (3) of the patient (1), if the time lag is greater than a threshold value, wherein the threshold value is between 0.5 and 20 seconds, and preferably between 1 and 8 seconds, or

- determine the location of the distal end (110) to be a lung (6) of the patient (1), if the pressure difference is less than a threshold value and the pressure peaks of the first and second pressure sensors (131, 132) are both of a positive value or are both of a negative value, wherein preferably the threshold value is between 1 and 6 mmHg and most preferably between 1 and 2 mmHg.

5. The feeding device (50) according to one of claims 1 to 4, further comprising: at least one wire (135) electrically connecting the first pressure sensor (131) and/or the second pressure sensor (132) with the controller (150), and/or at least one optical fibre (135) optically connecting the first pressure sensor (131) and/or the second pressure sensor (132) with the controller (150).

6. The feeding device (50) according to one of claims 1 to 5, further comprising: a second lumen (125) fluidly connecting the first pressure sensor (131) and/or the second pressure sensor (132) with an ambient atmosphere of the feeding device (50), wherein preferably the first and/or second pressure sensor (131, 132) is a dif- ferential pressure sensor, one side of which is in fluid communication with the ambient atmosphere via the second lumen (125).

7. The feeding device (50) according to one of claims 1 to 6, wherein the first and/or second pressure sensor (131, 132) is at least partially enclosed in a housing (133) having a greater rigidity than the feeding tube (100). 8. The feeding device (50), further comprising: a feeding pump (121) configured to pump a nutrition into the first lumen (120) at or near the proximal end (105).

9. A method for determining a location of a feeding tube (100), the method comprising: inserting a feeding tube (100) into a patient (1), wherein the feeding tube

(100) has at least one lumen (120) extending from a distal end (110) to a proximal end (105) of the tube (100); receiving (220) a signal from a first pressure sensor (131) disposed in proximity to the distal end (110) of the feeding tube (100); receiving (220) a signal from a second pressure sensor (132) disposed in the feeding tube (100) and configured to measure a pressure acting on the tube, wherein the second pressure sensor (132) is further away from the distal end (110) of the tube (100) in a longitudinal direction of the tube (100) than the first pressure sensor (131); and calculating (260, 309, 318) a pressure correlation between a respective pressure measured by the first and second pressure sensors (131, 132) based on the received signals; and determining (270, 320) a location of the distal end (110) of the tube (100) in the patient (1) based on the calculated pressure correlation. 10. The method according to claim 9, wherein calculating a pressure correlation comprises calculating an absolute pressure value of the first pressure sensor (131) and an absolute pressure value of the second pressure sensor (132) at the same measurement time, and wherein determining the location comprises determining the location of the distal end (110) to be a stomach (2) of the patient (1), if the absolute pressure values of the first and second pressure sensors (131, 132) are approximately equal and the pressure signals from the first and second pressure sensors (131, 132) indicate inverse pressures at the first and second pressure sensors.

11. The method according to claim 9 or 10, wherein calculating the pressure correlation comprises

- determining a pressure difference between the respective pressure measured by the first and second pressure sensors (131, 132), and/or - determining a frequency of pressure peaks measured by the first or second pressure sensor (131, 132), and/or

- determining a time lag between a pressure peak measured by the first pressure sensor (131) and a pressure peak measured by the second pressure sensor (132), wherein determining the location comprises determining the location of the distal end (110) based on the determined pressure difference, and/or determined frequency, and/or determined time lag.

12. The method according to claim 11, wherein determining the location comprises: - determining the location of the distal end (110) to be a stomach (2) of the patient (1), if the time lag is less than a threshold value or zero and the pressure difference is less than a threshold value or zero, while the pressure signals of the first and second pressure sensors indicate inverse pressures,

- determining the location of the distal end (110) to be a stomach (2) of the patient (1), if the pressure difference is above a threshold value, wherein preferably the pressure measured by the first pressure sensor (131) is greater than the pressure measured by the second pressure sensor (132),

- determining the location of the distal end (110) to be a stomach (2) of the patient (1), if the frequency of pressure peaks of the first pressure sensor (131) is about 2.0 to 3.7 peaks per minute, preferably 2.5 to 3.2 peaks per minute,

- determining the location of the distal end (110) to be an oesophagus (3) of the patient (1), if the time lag is greater than a threshold value, wherein the threshold value is between 0.5 and 20 seconds, and preferably between 1 and 8 seconds, or - determining the location of the distal end (110) to be a lung (6) of the patient (1), if the pressure difference is less than a threshold value and the pressure peaks of the first and second pressure sensors (131, 132) are both of a positive value or are both of a negative value, wherein preferably the threshold value is between 1 and 6 mmHg and most preferably between 1 and 2 mmHg.

13. A feeding system (75), comprising: a feeding device (50) according to one of claims 1 to 8; and an output device (180) in communication with the feeding device (50) and configured to provide an output signal indicating the determined location of the distal end (110) of the tube (100).