Device and method for judging far-end position of catheter inserted into cavity of main body

Abstract

A device for determining a position of a distal end of a catheter inserted into a cavity of a body, the device comprising: a sensing unit having a fluid outlet for forming fluid communication with a proximal end of the catheter; a fluid chamber disposed in the sensing unit in fluid communication with the fluid outlet; the fluid injection valve is arranged on a fluid communication path between the fluid chamber and the fluid outlet, and when the near end of the catheter is in fluid communication with the fluid outlet and the far end of the catheter is inserted into the main body cavity to start the fluid injection valve, the fluid injection valve is opened for a preset time to release fluid injection with preset pressure and preset volume; the fluid injection enters the cavity of the main body from the fluid chamber through the conduit; a return pressure sensor in fluid communication with the fluid outlet for measuring a return pressure generated when a fluid bolus is released from the distal end of the catheter into the body cavity for a predetermined period of time; the microcontroller is in communication connection with the back pressure sensor and is configured to generate a back pressure curve from the measured back pressure, and the microcontroller is further configured to obtain characteristics of the generated back pressure curve and judge the position of the far end of the catheter according to the obtained characteristics; the first switch is arranged on the sensing unit and can be activated by a user to activate the fluid injection valve; and a first indicator disposed on the sensing unit for indicating if the microcontroller determines that the distal end of the catheter is located in the first predetermined body cavity.

Description

Technical Field

[0001] This application relates to an apparatus and method for determining the distal position of a catheter inserted into a body cavity, particularly for determining the distal position of a nasogastric catheter used for feeding patients via catheter. Background Technology

[0002] In medical settings, catheters are frequently inserted into parts of the body (whether human or animal) for various reasons. Clearly, catheters need to be correctly positioned to be effective. If the distal end of the catheter is inserted incorrectly, therapeutic agents delivered through the catheter will be delivered to the wrong part of the body and may cause harm.

[0003] A commonly used catheter is the nasogastric tube (NGT), which must be inserted through the nose and esophagus into the stomach for feeding patients who cannot eat normally. During NGT insertion, misdirection can occur, and the distal end of the NGT may end up in the lungs or pleural cavity instead of the stomach. Pouring liquid food into such an NGT can lead to pneumothorax, pneumonia, and / or feeding empyema. To prevent this, caregivers are currently instructed to aspirate from the inserted NGT and test its acidity to confirm whether the distal end of the NGT has entered the stomach, as aspirate from the stomach is significantly more acidic than aspirate from an endotracheal tube or lung. However, some patients are given proton pump inhibitors, which reduce stomach acid production. Aspirate from these patients is less acidic, so acidity testing cannot be used to confirm the distal NGT location in these patients or those unable to produce stomach aspirate. Although a chest X-ray can be used to determine the position of the distal end of the inserted NGT, it is neither feasible nor advisable to perform a chest X-ray before each catheter feeding.

[0004] To facilitate the determination of the distal location of the non-gastrointestinal tract (NGT), several systems have been developed that utilize one or more of various sensors and devices at the distal end of the NGT. These sensors and devices include ultrasonic transducers, pH sensors, contact pressure sensors, continuity monitors, fluid pressure sensors, microphones, vibrators, and waveform generators. However, introducing sensors into the body to determine the distal location of the NGT is not desirable, nor is it desirable to leave sensors in the body for extended periods. Furthermore, these sensors must be biologically robust and biocompatible to withstand corrosion from bodily fluids (such as stomach acid) or antibodies from the body's immune system, thus increasing the cost of these sensors. Summary of the Invention

[0005] This application discloses an apparatus and method for determining the distal position of a catheter inserted into a body cavity. It can be used to determine the position of the distal NGT before initiating catheter feeding. At no time will any part of the apparatus come into contact with the body. The disclosed apparatus and method do not introduce any sensors into the body and are compatible with commonly used standard catheters. The device is suitable for all patients, portable, quick to set up, and simple to operate. It allows for real-time bedside care and provides position confirmation within seconds. It avoids the mess and contamination problems associated with aspiration. The device is easy to clean and can be used on multiple patients without causing cross-contamination or generating any radiation, thus reducing costs and posing no health risks.

[0006] According to a first example aspect, an apparatus is provided for determining the position of a distal end of a catheter inserted into a body cavity. The apparatus includes: a sensing unit having a fluid outlet for fluid communication with a proximal end of the catheter; a fluid chamber disposed in the sensing unit and fluidly communicating with the fluid outlet; and a fluid bolus valve disposed in the fluid communication path between the fluid chamber and the fluid outlet. When the proximal end of the catheter is fluidly communicating with the fluid outlet and the distal end of the catheter is inserted into the body cavity, and the fluid bolus valve is activated, the fluid bolus valve opens within a predetermined time to release a fluid bolus with a predetermined pressure and a predetermined volume. The system comprises: a fluid injection valve (bolus) that injects fluid from a fluid chamber into a main body cavity through a conduit; a back pressure sensor, fluidly connected to a fluid outlet, for measuring back pressure generated when the fluid injection is released from the distal end of the conduit into the main body cavity within a predetermined time; a microcontroller communicatively connected to the back pressure sensor, configured to generate a back pressure curve from the measured back pressure, the microcontroller also configured to acquire features of the generated back pressure curve and determine the position of the distal end of the conduit based on the acquired features; a first switch on the sensing unit, which can be activated by the user to activate the fluid injection valve; and a first indicator on the sensing unit for indicating if the microcontroller determines that the distal end of the conduit is located in a first predetermined main body cavity.

[0007] The device may also include an alarm indicator mounted on the sensing unit, which can be activated by the microcontroller to issue an alarm if the microcontroller determines that the distal end of the catheter is not in the first predetermined body cavity.

[0008] The device may also include a second indicator disposed on the sensing unit for indicating if the microcontroller determines that the distal end of the catheter is located in the second predetermined body cavity.

[0009] The device may also include a second switch located on the sensing unit, which can be activated by the user to activate the fluid injection valve, and an alarm indicator can also be activated by the microcontroller to issue an alarm if the microcontroller determines that the distal end of the catheter is not in the second predetermined body cavity.

[0010] The device may also include a third indicator disposed on the sensing unit, which may be activated by the microcontroller to indicate that the position of the distal end of the catheter is unknown if the microcontroller determines that the distal end of the catheter is neither in the first predetermined body cavity nor in the second predetermined body cavity.

[0011] The fluid may be air, and the sensing unit also includes a fluid inlet, and the device also includes a pump disposed in an inter-fluid communication path between the fluid inlet and the fluid chamber for pumping ambient air into the fluid chamber.

[0012] The device may also include a chamber pressure sensor for determining the air in the fluid chamber, wherein the microcontroller is communicatively connected to the chamber pressure sensor and the pump, and the pump can be controlled by the microcontroller to maintain the chamber air pressure at a preset chamber air pressure.

[0013] The device may also include a filter disposed between the fluid inlet and the fluid chamber for filtering ambient air pumped into the fluid chamber.

[0014] The sensing unit may also include an exhaust port, wherein the fluid chamber is in fluid communication with the exhaust port via an exhaust valve configured to allow excess air to leave the fluid chamber when the chamber air pressure exceeds a predetermined safety pressure.

[0015] The device may also include a cartridge that can be attached to the sensing unit, the proximal end of a conduit being connected to the cartridge, the cartridge having a fluid channel therethrough to establish a fluid connection between the fluid outlet of the sensing unit and the proximal end of the conduit, wherein a valve is provided in the fluid channel to prevent fluid from flowing back from the conduit to the fluid outlet.

[0016] The device may also include a connecting conduit to establish a fluid connection between the cartridge and the proximal end of the conduit.

[0017] The microcontroller may communicate with the first switch and the fluid injection valve and be configured to control the activation of the fluid injection valve when the user activates the first switch.

[0018] The microcontroller may be further configured to compare the acquired features with predetermined features of a predetermined body cavity, and classify the location of the distal end of the catheter based on the predetermined features of the predetermined body cavity associated with the acquired features.

[0019] According to a second example aspect, a method is provided for determining the distal position of a catheter inserted into a body cavity, the method comprising the steps of: (a) releasing at least one fluid bolus having a predetermined pressure and a predetermined volume from a fluid chamber toward the proximal end of the catheter; (b) using a back pressure sensor to measure the back pressure generated when at least one fluid bolus is released from the distal end of the catheter into the body cavity within a predetermined time period; (c) using a microcontroller to generate a back pressure curve from the measured back pressure; (d) using the microcontroller to obtain characteristics of the generated back pressure curve; (e) using the microcontroller to determine the position of the distal end of the catheter based on the obtained characteristics; and (f) using an indicator to indicate the position of the distal end of the catheter.

[0020] If the location determined in step (d) is a predetermined first body cavity; step (e) may further include the microcontroller activating a first indicator to indicate that the distal end of the catheter is located in the predetermined first body cavity.

[0021] If the location determined in step (d) is a predetermined second body cavity, step (e) may further include the microcontroller activating a second indicator to indicate that the distal end of the catheter is located in the predetermined second body cavity.

[0022] If the location determined in step (d) is neither the predetermined first main cavity nor the predetermined second main cavity, step (e) may include the microcontroller activating a third indicator to indicate that the location of the distal end of the catheter is unknown.

[0023] The method may further include, if step (a) is performed by activating the first switch, and the position determined in step (d) is not the predetermined first body cavity, then the microcontroller activates an alarm indicator.

[0024] The method may further include, if the location determined in step (d) is neither a predetermined first main cavity nor a predetermined second main cavity, then the microcontroller activates an alarm indicator.

[0025] Step (a) may include releasing multiple fluid boluses to the proximal end of the catheter at predetermined time intervals, wherein step (b) includes measuring the back pressure generated when the multiple fluid boluses are released from the distal end of the catheter into the body cavity.

[0026] The fluid may be air, and the method may further include pumping ambient air into the fluid chamber to maintain the chamber air pressure of the air in the fluid chamber at a preset chamber air pressure.

[0027] The method may further include using a filter to filter ambient air pumped into the fluid chamber.

[0028] The method may further include allowing excess air to leave the fluid chamber through an exhaust valve when the chamber air pressure exceeds a predetermined safety pressure.

[0029] The method may further include, prior to step (a), providing a fluid-connected cartridge between the fluid outlet and the proximal end of the conduit to prevent fluid from flowing back from the conduit to the outlet using a valve provided in the cartridge.

[0030] The method may further include, prior to step (a), establishing a fluid connection between the cartridge and the proximal end of the catheter using a connecting catheter.

[0031] Step (e) may include comparing the obtained features with reference features of a predetermined body cavity, and classifying the location of the distal end of the catheter according to the predetermined body cavity associated with the reference features and the obtained features. Attached Figure Description

[0032] In order to enable the present invention to be fully understood and readily practiced, exemplary embodiments of the present invention will now be described by way of non-limiting examples, with reference to the accompanying drawings.

[0033] Figure 1 This is a perspective view of an exemplary embodiment, in which a catheter is connected to a device for determining the distal position of the catheter when it is inserted into the body cavity;

[0034] Figure 2 yes Figure 1 An exemplary component of the device before assembly and use; Figure 3 yes Figure 1 An exploded assembly diagram of the sensing unit in the device; Figure 4 It is a close-up perspective view of some components inside the sensing unit; Figure 5 This is a top view of the first exemplary top surface of the sensing unit; Figure 6 This is a top view of the second exemplary top surface of the sensing unit; Figure 7 This is a top view of the third exemplary top surface of the sensing unit; Figure 8 This is an exemplary back pressure curve obtained when the distal end of the catheter is in the stomach; Figure 9 This is the first exemplary back pressure curve obtained when the distal end of the catheter is in the esophagus; Figure 10 This is a second exemplary back pressure curve obtained when the distal end of the catheter is in the esophagus; Figure 11 This is a flowchart of an exemplary method for determining the distal position of a catheter when it is inserted into the body cavity; Figure 12 It is a schematic diagram of the fluid and signal paths of the device and method. Detailed Implementation

[0035] Reference Figures 1 to 12 Exemplary embodiments of the apparatus 100 and method 200 for determining the position of the distal end 301 of a catheter 300 inserted into a body cavity (not shown) are described, wherein the same reference numerals are used in the figures to refer to the same or similar components.

[0036] Generally speaking, such as Figure 1 and 2 As shown, the device 100 includes a sensing unit 10 having a fluid outlet 11 for establishing fluid communication with the proximal end 302 of the conduit 300. The sensing unit 10 is preferably easy to carry with one hand and may have a cuboid shape, with a housing 14 enclosing the various components therein, such as... Figure 3 As shown. In some embodiments of device 100, the proximal end 320 of conduit 300 may be directly connected to fluid outlet 11. Alternatively, in a preferred embodiment, for hygienic purposes, such as Figure 1 and 2 As shown, the device 100 may further include a cartridge 80 attachable to the sensing unit 10, to which the proximal end 302 of the conduit 300 can be connected. It is understood that the cartridge 80 has a fluid passage therethrough to establish a fluid connection between the fluid outlet 11 of the sensing unit 10 and the proximal end 302 of the conduit 300. A backflow prevention valve (not shown) is preferably provided in the fluid passage of the cartridge 80 to prevent fluid from flowing back from the conduit 300 to the fluid outlet 11. Alternatively (not shown), the backflow prevention valve may be located at the fluid outlet 11 of the sensing unit 10. When the device 100 includes the cartridge 80, the housing 14 of the device may include a cartridge receiver 48 configured to form a fluid seal with the cartridge 80 while allowing fluid to flow from the housing 14 to the cartridge 80. The outer casing 14 and the card holder 80 are preferably made of plastic materials, such as polycarbonate (PC), acrylonitrile butadiene styrene copolymer (ABS), or a mixture of PC and ABS.

[0037] The device 100 may also include an additional connecting catheter 90 to establish a fluid connection between the cartridge 80 and the proximal end 302 of the catheter 300. In a preferred embodiment, the connecting catheter 90 may have a nozzle 91 at its distal end for connection to the proximal end 802 of the catheter 300. Thus, when the catheter 300 is a nasogastric catheter for feeding a bedridden patient, for example, when the sensing unit 10 may be placed on a bedside table, the connecting catheter 90 will allow a fluid connection to be established between the sensing unit 10 and the proximal end 302 of the catheter 300, which is farther away and closer to the bedridden patient. By providing the connecting catheter 90 and cartridge 80 as low-cost consumables for single-patient use, the high-cost sensing unit 10 can be shared among multiple patients, each with their own set of cartridge 80 and connecting catheter 90, for example in a healthcare facility, thereby reducing patient costs.

[0038] In the device 100, the sensing unit 10 is provided with a fluid chamber 13, such as... Figure 3 As shown. Fluid chamber 13 is in fluid communication with fluid outlet 11. Fluid chamber 13 can be connected to fluid outlet 11 via chamber outlet conduit 13-2, for example, as shown. Figure 4 As shown. A fluid injection valve 17 is disposed on the fluid communication path between the fluid chamber 13 and the fluid outlet 11, as shown. Figure 4 As shown. The fluid injection valve 17 can be a solenoid valve, for example. When the fluid injection valve 17 is activated, it opens for a predetermined time period. This releases a fluid injection (not shown) from the fluid chamber 13 to the fluid outlet 11. The fluid injection has a predetermined pressure and a predetermined volume, which can be determined based on the fluid pressure in the fluid chamber 13 and the predetermined time period during which the fluid injection valve 17 is open. When the proximal end 302 of the conduit 300 is in fluid communication with the fluid outlet 11 and the distal end 301 of the conduit 300 is inserted into the main cavity, if the fluid injection valve 17 is open, the released fluid injection will enter the conduit 300 from the fluid chamber 13 and exit from the distal end 301 of the conduit 300 into the main cavity.

[0039] When fluid is injected from the distal end 301 of the conduit 300 into the main cavity, back pressure is generated in the conduit 300 due to resistance encountered from the main cavity. To measure this back pressure within a predetermined time period, a back pressure sensor 19 is provided in the sensing unit 10, which is in fluid communication with the fluid outlet 11 (e.g., through the back pressure sensor conduit 19-1, such as...). Figure 4 (As shown). The device 100 also includes a microcontroller 20 disposed in the sensing unit 10 and communicatively connected to the back pressure sensor 19. The microcontroller 20 is configured to generate a back pressure curve based on the back pressure measured over a predetermined time period.

[0040] Figure 8An example backpressure curve is shown when the distal end 301 of catheter 300 is confirmed to be in the patient’s stomach (the stomach being an example of a main cavity) and fluid is released from the fluid chamber 13. Figure 9 and Figure 10 Example back pressure curves are shown from two patients, where the distal end 301 of catheter 300 was identified in the esophagus of each patient, an example of another main cavity. As can be seen, the back pressure curves are when the main cavity is the esophagus. Figure 9 and Figure 10 Both have significant initial peaks, then drop sharply and tend to level off, which is similar to the back pressure curve when the main cavity is the stomach. Figure 8 Unlike the former, the latter does not have a distinct initial peak, but only a small and smooth decline, which then tends to level off.

[0041] Obviously, different patients will have different back pressure curves because the response of the body cavity will not be exactly the same for each person when fluid is injected into it. However, from the multiple back pressure curves obtained above, it was found that specific body cavities produce back pressure curves with specific characteristics, which are consistent across multiple patients, such as... Figure 9 and Figure 10 The similarity between them is shown. These specific features differ between different body cavities. These back pressure curve features can be extracted using methods such as signal processing as reference features specific to a pre-determined body cavity. Using device 100, back pressure curves have been obtained from different known body cavities of multiple patients, and subsequently, specific features of these back pressure curves have been obtained. In this way, reference features specific to a pre-determined body cavity have been obtained and can be used to determine the position of the distal end 301 of the catheter 300 in most patients. These reference features are stored in a data storage unit (not shown) communicatively connected to microcontroller 20 before using device 100. These reference features are stored when device 100 is configured specifically to detect whether the distal end 301 of catheter 300 is in one or more pre-determined body cavities.

[0042] In device 100, microcontroller 20 is configured to acquire features of the generated backpressure curve each time device 100 is used, and determine the position of the distal end 301 of catheter 300 based on the acquired features. To this end, microcontroller 20 may compare the features acquired during use of device 100 with stored reference features, and when the reference features are related to the acquired features, classify the position of the distal end 301 of catheter 300 as being within a pre-determined body cavity.

[0043] In embodiments where air is used as the fluid in device 100, chamber pressure sensor 16 is preferably connected to fluid chamber 13 in a fluid connection manner (e.g., via...). Figure 4The chamber pressure sensor conduit 16-1 is shown. In these embodiments, the sensing unit 10 also includes a fluid inlet 99 and a pump 97, the pump 97 being disposed in the fluid communication path between the fluid inlet 99 and the fluid chamber 13 (e.g., via...). Figure 4 The inlet conduit 99-1 and pump conduit 97-1 are shown. Ambient air can be drawn in through the fluid inlet 99 and pumped into the fluid chamber 13 using the pump 97. In these embodiments, the microcontroller 20 is communicatively connected to the chamber pressure sensor 16 and the pump 97. The pump 97 is controlled by the microcontroller 20 to maintain the chamber air pressure at a preset chamber air pressure. A filter (not shown) can be provided between the fluid inlet 99 and the fluid chamber 13 to filter the ambient air pumped into the fluid chamber 13, so that the fluid injection released into the main cavity contains clean air. More preferably, an exhaust port 95 can also be provided in the sensing unit 10, wherein the fluid chamber 13 is in fluid communication with the exhaust port 95 via an exhaust valve 94 (e.g., via...). Figure 4 The exhaust outlet conduit 95-1 and exhaust valve conduit 94-1 are shown. The exhaust valve 94 is communicatively connected to the microcontroller 20 and is configured to be activated by the microcontroller 20 to allow excess air to leave the fluid chamber 13 when the microcontroller 20 determines that the chamber air pressure (measured by the chamber pressure sensor 16) exceeds a predetermined safety pressure.

[0044] In all embodiments of device 100, a first switch 21 is disposed on sensing unit 10. The first switch 21 can be activated by a user to activate fluid injection valve 17. In a preferred embodiment, the first switch 22 may include a push-button switch disposed on the top surface 18 of the housing 14 of sensing unit 10, such as... Figure 1-3 As shown in Figures 5-7. In alternative embodiments, other types of switches (not shown) may be used. The first switch 21 is preferably connected to the microcontroller 20 so that when the first switch 21 is activated, the microcontroller 20 actuates the fluid injection valve 17 by opening it for a predetermined time period. Thus, the released fluid injection has a predetermined pressure and a predetermined volume. For example, the fluid injection may have a pressure range of 10 cmH2O to 100 cmH2O and a volume range of 0.1 ml to 10 ml. For embodiments using air as the fluid, this can be controlled by the microcontroller based on measurements from the chamber pressure sensor 16, the known size of the fluid outlet 11, and the predetermined time period during which the fluid injection valve 17 is open.

[0045] In all embodiments, in addition to the first switch 21, the first indicator 31 is also disposed on the sensing unit 10, and preferably also disposed on the top surface 18 of the housing 14, such as... Figure 1-3As shown in Figures 5-7, a first indicator 31 is connected to a microcontroller 20. During use of the device 100, after the first switch 21 is activated and fluid injection has been released into the body cavity, the microcontroller, as described above, determines the body cavity in which the distal end 301 of the catheter 300 is located based on the acquired characteristics of the generated back pressure curve. Also as described above, this may include the microcontroller 20 comparing the acquired characteristics with reference characteristics of a first predetermined body cavity (e.g., the stomach). These reference characteristics are stored prior to use of the device 100 in a data storage unit (not shown) communicatively connected to the microcontroller 20. These reference characteristics are stored when the device 100 is configured specifically to detect whether the distal end 301 of the catheter 300 is in the first predetermined body cavity. If the microcontroller 20 determines that the distal end 301 of the catheter 300 is indeed located in the first predetermined body cavity, the first indicator 31 is activated by the microcontroller 20 to provide this indication to the user, for example, by illuminating the indicator if the first indicator includes a light-emitting diode (LED).

[0046] In some embodiments, such as Figure 5-7 As shown, the device 100 may further include an alarm indicator 33 disposed on the sensing unit 10, and preferably also disposed on the top surface 18 of the housing 14. The alarm indicator 33 is connected to and can be activated by the microcontroller 20 to issue an alarm when the microcontroller 20 determines that the distal end 301 of the conduit 300 is not in the first predetermined body cavity, for example, if the alarm indicator 33 is an LED, then an alarm is issued by illuminating it.

[0047] In some embodiments, such as Figure 6 and 7 As shown, the device 100 may further include a second indicator 32 disposed on the sensing unit 10. In these embodiments, prior to use, the device 100 is configured to specifically detect whether the distal end 301 of the catheter 300 is in a first predetermined body cavity (e.g., the stomach) or whether the distal end 301 of the catheter 300 is in a second predetermined body cavity (e.g., the esophagus). This may include storing reference features of the first and second predetermined body cavities in the sensing unit 10 before using the device 100. The second indicator 32 is used to indicate whether the distal end 301 of the catheter 300 is in the second predetermined body cavity if the microcontroller 20 determines so based on features obtained when using the device 100. In this embodiment, if the microcontroller 20 detects that the distal end 301 of the catheter 300 is neither in the first nor the second predetermined body cavity, the microcontroller 20 may be configured to activate the alarm indicator 33 to issue an alarm.

[0048] exist Figure 7In a further embodiment shown, the device 100 may further include a second switch 22 disposed on the sensing unit 10, as well as a second indicator 32 and an alarm indicator 33. The second switch 22 is configured to be activated by a user to actuate the fluid injection valve 17 when the user wishes to determine whether the distal end 301 of the catheter 300 is in the second predetermined body cavity. In this embodiment, if the microcontroller 20 determines that the distal end 301 of the catheter 300 is not in the second predetermined body cavity after the second switch 22 is activated, the microcontroller 20 may be configured to activate the alarm indicator 33 to issue an alarm. If the distal end 301 is determined to be in the first predetermined body cavity, the first indicator 31 preferably also illuminates along with the alarm indicator 33. Similarly, if the user activates the first switch 21 to determine whether the distal end 301 of the catheter is in the first predetermined main body cavity, and the microcontroller 20 determines that it is in the second predetermined main body cavity, the microcontroller 20 can be configured to activate the alarm indicator 33 to issue an alarm after the first switch 21 is activated if the microcontroller 20 determines that the distal end 301 of the catheter 300 is not in the first predetermined main body cavity. In this embodiment, if the microcontroller 20 detects that the distal end 301 of the catheter 300 is neither in the first predetermined main body cavity nor in the second predetermined main body cavity after the first switch 21 or the second switch 22 is activated, the microcontroller 20 can be further configured to activate the alarm indicator 33 to issue an alarm.

[0049] exist Figures 1-3 and Figures 5-7 In the exemplary embodiment shown, the top surface 18 of the housing 14 may include a membrane switch panel 18, which provides a switch and indicator for the sensing unit 10. Thus, the switch and indicator are protected by a waterproof membrane of the membrane switch panel 18, which serves as the user interface of the device 100. Preferably, a power switch 29 is also provided on the top surface 18 of the housing 14 to turn on the sensing unit 10. However, in other embodiments, the first switch 21 may also be configured to function as a power switch in addition to activating the fluid injection valve 17. In the sensing unit 10, the microcontroller 20, valves 17 and 94, pressure sensors 16 and 19, and fluid pump 97 may be housed on a printed circuit board 40 provided within the housing 14, such as... Figure 3 and 4 As shown. Switches 21, 22, 29 and indicators 31, 32, 33 located on the top surface 18 of the housing 14 can be connected to the printed circuit board 40 for communication with the microcontroller 20.

[0050] Figure 11An exemplary embodiment of a method 200 for determining the position of the distal end 301 of a catheter 300 inserted into a body cavity is shown. Figure 13 shows a fluid passage and a signal passage, illustrating how fluid and signal flow through the various components of the device 100 when method 200 is performed. (Reference) Figure 11 Method 200 first includes releasing at least one fluid bolus with a predetermined pressure and predetermined volume from fluid chamber 13 to proximal end 302 of catheter 300 (201). This occurs when the user activates first switch 21. Next, method 200 includes using back pressure sensor 19 to measure the back pressure generated when at least one fluid bolus is released from distal end 301 of catheter 300 into the body cavity within a predetermined time period (202). Method 200 then includes using microcontroller 20 to generate a back pressure profile from the measured back pressure (203). Subsequently, method 200 includes using microcontroller 20 to acquire characteristics of the generated back pressure profile (204). Next, using microcontroller 20, the position of distal end 301 of catheter 300 is determined based on the acquired characteristics (205), and then the position of distal end 301 of catheter 300 is indicated using indicator 31 (206). It is worth noting that the indication position (206) includes issuing an alarm if it is determined that the distal end 301 of the catheter 300 is not in the device 100 but is configured for detection in a predetermined body cavity.

[0051] Using the device 100 and method 200 described above, the position of the distal end 301 of the catheter 300 can be quickly determined within seconds and indicated to the user. The device 100 provides a user-friendly, real-time determination of the position of the distal end 301 of the catheter 300 without the need for X-rays or aspiration when the catheter 300 is a nasogastric catheter. Thus, the patient is not exposed to any harmful radiation, and because none of the components of the device 100 come into contact with the patient during use, no additional foreign matter is introduced into the patient's body. Cross-contamination between patients is also avoided when the sensing unit 10 is shared, as the cartridge 80 and connecting catheter 90 are for single-patient use, and the sensing unit 10 does not come into contact with any fluid from the patient due to the anti-backflow valve provided in the cartridge 80. The device 100 can be configured to determine multiple different body cavities into which the catheter may be inserted by storing reference features of these multiple different body cavities for comparison with features obtained during use of the device 100, and providing necessary indicators to show when the distal end 301 of the catheter 300 is determined to be in a specific body cavity.

[0052] While exemplary embodiments of the invention have been described in the foregoing description, those skilled in the art will understand that many variations in design, construction, and / or operational details may be made without departing from the invention. It is understood that many further changes, modifications, and substitutions may be made to various aspects of the described embodiments, all falling within the spirit and scope of the appended claims.

[0053] In this specification and the following claims, unless the context otherwise requires, the words “comprising” and “including”, as well as variations such as “comprising” and “including”, shall be understood to imply inclusion of the said integer or group of integers or steps, but not to exclude any other integer or group of integers or steps.

Claims

1. A device for determining the distal position of a catheter inserted into a body cavity, the device comprising: The sensing unit has a fluid outlet for establishing fluid communication with the proximal end of the conduit; A fluid chamber is disposed in the sensing unit and is in fluid communication with the fluid outlet; A fluid injection valve is disposed in the fluid communication path between the fluid chamber and the fluid outlet, wherein when the proximal end of the conduit is in fluid communication with the fluid outlet and the distal end of the conduit is inserted into the main body cavity and the fluid injection valve is activated, the fluid injection valve is opened for a predetermined time period to release fluid injection, the fluid injection having a predetermined pressure and a predetermined volume, entering the main body cavity from the fluid chamber via the conduit; A back pressure sensor, in fluid communication with the fluid outlet, is used to measure the back pressure generated when the fluid is injected from the distal end of the conduit into the main body cavity within a predetermined time period; A microcontroller is communicatively connected to the back pressure sensor and configured to generate a back pressure curve based on the measured back pressure. The microcontroller is further configured to acquire features of the generated back pressure curve and determine the position of the distal end of the catheter based on the acquired features. The first switch, located on the sensing unit, can be activated by the user to start the fluid injection valve; as well as A first indicator, disposed on the sensing unit, is used to indicate the situation if the microcontroller determines that the distal end of the catheter is located in a first predetermined body cavity.

2. The device for determining the distal position of the catheter inserted into the main body cavity according to claim 1 further includes an alarm indicator disposed on the sensing unit, which can be activated by the microcontroller to issue an alarm when the microcontroller determines that the distal end of the catheter is not in the first predetermined main body cavity.

3. The device for determining the distal position of a catheter inserted into a body cavity according to claim 1 or claim 2, further comprising a second indicator disposed on the sensing unit for indicating the case where the microcontroller determines that the distal end of the catheter is located in a second predetermined body cavity.

4. The device for determining the distal position of the catheter inserted into the body cavity as described in claim 3 when claim 2 is attached, further comprising a second switch disposed on the sensing unit, which can be activated by a user to activate the fluid injection valve, and wherein the alarm indicator is further activating the microcontroller to issue an alarm when the microcontroller determines that the distal end of the catheter is not in the second predetermined body cavity.

5. The device for determining the distal position of a catheter inserted into a main body cavity according to claim 4 further includes a third indicator disposed on the sensing unit, which can be activated by the microcontroller, for indicating that the distal position of the catheter is unknown when the microcontroller determines that the distal end of the catheter is neither in the first predetermined main body cavity nor in the second predetermined main body cavity.

6. The apparatus for determining the distal position of a conduit inserted into a body cavity as described in any of the preceding claims, wherein the fluid is air, wherein the sensing unit further includes a fluid inlet, and wherein the apparatus for determining the distal position of a conduit inserted into a body cavity further includes a pump disposed in a fluid communication path between the fluid inlet and the fluid chamber for pumping ambient air into the fluid chamber.

7. The apparatus for determining the distal position of the catheter inserted into the body cavity according to claim 6, further comprising a chamber pressure sensor for determining the chamber air pressure of the air in the fluid chamber, wherein the microcontroller is communicatively connected to the chamber pressure sensor and the pump, and wherein the pump is controllable by the microcontroller to maintain the chamber air pressure at a preset chamber air pressure.

8. The device for determining the distal position of a conduit inserted into the body cavity according to claim 6 or claim 7, further comprising a filter disposed between the fluid inlet and the fluid chamber for filtering ambient air pumped into the fluid chamber.

9. The apparatus for determining the distal position of a catheter inserted into a body cavity according to any one of claims 6 to 8, wherein the sensing unit further includes an exhaust port, and wherein the fluid chamber is in fluid communication with the exhaust port via an exhaust valve configured to allow excess air to leave the fluid chamber when the air pressure in the chamber exceeds a predetermined safety pressure.

10. The apparatus for determining the distal position of a catheter inserted into a body cavity as claimed in any of the preceding claims, further comprising a cartridge attachable to the sensing unit and the proximal end of the catheter connectable to the cartridge, the cartridge having a fluid passage therethrough to establish a fluid connection between the fluid outlet of the sensing unit and the proximal end of the catheter, wherein a valve is disposed in the fluid passage to prevent fluid from flowing back from the catheter to the fluid outlet.

11. The apparatus for determining the distal position of a catheter inserted into a body cavity according to claim 10, further comprising a connecting catheter for establishing a fluid connection between the cartridge and the proximal end of the catheter.

12. The apparatus for determining the distal position of a catheter inserted into a body cavity as claimed in any of the preceding claims, wherein the microcontroller is communicatively connected to the first switch and the fluid injection valve, and is configured to control the activation of the fluid injection valve when the user activates the first switch.

13. The apparatus for determining the distal position of a catheter inserted into a body cavity as claimed in any of the preceding claims, wherein the microcontroller is further configured to compare the obtained features with predetermined features of a predetermined body cavity, and to classify the distal position of the catheter based on the predetermined features of the predetermined body cavity associated with the obtained features.

14. A method for determining the distal position of a catheter inserted into a body cavity, the method comprising the following steps: (g) Discharge at least one fluid bolus having a predetermined pressure and a predetermined volume from the fluid chamber toward the proximal end of the catheter; (h) Using a back pressure sensor, measure the back pressure generated when the at least one fluid injection is released from the distal end of the catheter into the body cavity within a predetermined time period; (i) Using a microcontroller, a back pressure curve is generated from the measured back pressure; (j) Using the microcontroller, the characteristics of the generated back pressure curve are obtained; (k) Using the microcontroller, determine the position of the distal end of the catheter based on the obtained features; as well as (l) Use an indicator to indicate the position of the distal end of the catheter.

15. The method for determining the distal position of a catheter inserted into a body cavity according to claim 14, wherein if the position determined in step (d) is a first predetermined body cavity; step (e) includes the microcontroller activating a first indicator to indicate that the distal end of the catheter is located in the first predetermined body cavity.

16. The method for determining the distal position of a catheter inserted into a body cavity according to claim 15, wherein if the position determined in step (d) is a second predetermined body cavity, step (e) includes the microcontroller activating a second indicator to indicate that the distal end of the catheter is located in the second predetermined body cavity.

17. The method for determining the distal position of a catheter inserted into a body cavity according to claim 16, wherein if the position determined in step (d) is neither the first predetermined body cavity nor the second predetermined body cavity, step (e) includes the microcontroller activating a third indicator to indicate that the distal position of the catheter is unknown.

18. The method for determining the distal position of a catheter inserted into a body cavity according to any one of claims 15 to 17, further comprising, if step (a) is performed by activating a first switch and the position determined in step (d) is not the first predetermined body cavity, then the microcontroller activates an alarm indicator.

19. The method for determining the distal position of a catheter inserted into a body cavity according to any one of claims 16 to 17, further comprising, if the position determined in step (d) is neither the first predetermined body cavity nor the second predetermined body cavity, then the microcontroller activates the alarm indicator.

20. The method for determining the distal position of a catheter inserted into a body cavity according to any one of claims 14 to 19, wherein step (a) comprises releasing a plurality of fluid boluses to the proximal end of the catheter at predetermined time intervals, and wherein step (b) comprises measuring the back pressure generated when the plurality of fluid boluses are released from the distal end of the catheter into the body cavity.

21. The method for determining the distal position of a catheter inserted into a body cavity according to any one of claims 14 to 20, wherein the fluid is air, and the method further comprises pumping ambient air into the fluid chamber to maintain the chamber air pressure of the air in the fluid chamber at a preset chamber air pressure.

22. The method for determining the distal position of the conduit inserted into the body cavity according to claim 21, further comprising filtering ambient air pumped into the fluid chamber using a filter.

23. The method for determining the distal position of the catheter inserted into the body cavity according to claim 21 or claim 22, further comprising allowing excess air to leave the fluid chamber through an exhaust valve when the air pressure in the chamber exceeds a predetermined safety pressure.

24. The method for determining the distal position of a catheter inserted into a body cavity according to any one of claims 13 to 23, further comprising, prior to step (a), providing a cassette fluidly connected between the fluid outlet and the proximal end of the catheter to use a valve provided in the cassette to prevent fluid from flowing back from the catheter to the outlet.

25. The method for determining the distal position of the catheter inserted into the body cavity according to claim 24, further comprising, prior to step (a), establishing a fluid connection between the cartridge and the proximal end of the catheter using a connecting catheter.

26. The method for determining the distal position of a catheter inserted into a body cavity according to any one of claims 13 to 25, wherein step (e) comprises comparing the obtained feature with a reference feature of a predetermined body cavity, and classifying the distal position of the catheter according to the predetermined body cavity of the reference feature associated with the obtained feature.

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