A method and apparatus for detecting functional residual gas volume in animals

Abstract

This invention relates to the fields of biomedical engineering and animal physiological testing technology, specifically a method and device for detecting functional residual capacity (FRC) in animals. The method includes constructing a measurable airway circuit, which connects the animal's lungs to an airway of known volume in a sealed manner, forming a sealed container with a smaller volume measurement range. By injecting a quantitative amount of gas into this sealed container and measuring the pressure change inside the sealed container, the volume of the sealed container can be directly calculated, thus accurately obtaining the FRC result of the small animal.

Description

Technical Field

[0001] This invention relates to the fields of biomedical engineering and animal physiological testing technology, specifically a method and device for detecting functional residual gas volume in animals. Background Technology

[0002] Functional residual capacity (FRC), as a key indicator reflecting the static mechanical properties of the animal respiratory system, is the amount of gas remaining in the lungs at the end of a quiet expiration. Its detection results are of great significance for studying animal respiratory physiology, the mechanisms of lung diseases (such as small animal disease models of asthma, pulmonary fibrosis, and chronic obstructive pulmonary disease), and drug evaluation.

[0003] Currently, existing animal FRC detection methods and related devices have many shortcomings: First, although plethysmography is a commonly used method, it indirectly calculates the animal's lung volume by detecting pressure changes in a closed plethysmography chamber. When the animal is too small (such as a mouse), the pressure fluctuation signal is weak, making it difficult to guarantee data accuracy. In addition, when an animal transitions from mechanical ventilation to spontaneous breathing, due to moderate to deep anesthesia, it needs to wait for a period of time before it can breathe spontaneously, and the weak pressure fluctuation signal can easily lead to asphyxiation and death. Second, nitrogen flushing devices have long detection times, and the animal's respiratory rate is fast (up to 80-120 breaths / minute in mice). Existing gas collection and analysis modules cannot meet the high-frequency sampling requirements, and key data are easily missed. Third, radiographic imaging devices are not only expensive but also require specialized radiation protection equipment, are complex to operate, and pose radiation safety hazards, making them difficult to promote and apply in routine laboratories.

[0004] Therefore, there is an urgent need for an animal functional residual gas detection device that has high detection accuracy, is easy to operate, and can achieve real-time dynamic monitoring, in order to solve the above-mentioned problems in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for detecting functional residual capacity in animals, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for detecting functional residual capacity in animals, comprising the following steps:

[0008] A measurable airway circuit is constructed to obtain the airway circuit volume in its initial state; appropriate lengths of silicone tubing are selected and connected sequentially to the necessary test equipment, including a volumetric recording box, an animal ventilator, a quantitative injection device, and a pressure sensor; the necessary test equipment is controlled and operated through a control host.

[0009] Animal preparation: Select experimental animals of appropriate weight, anesthetize them and perform endotracheal intubation to connect their lungs to the airway circuit, and close the volume plethysmography box to keep the experimental animals in a closed environment.

[0010] By recording changes in gas pressure inside the plethysmography chamber, the animal's respiratory cycle can be marked, and the end-expiratory time point of the animal can be identified.

[0011] At the end of the animal's expiration time, close the inspiratory and expiratory valves of the animal ventilator and detect the current gas pressure in the airway circuit;

[0012] Inject a measured amount of gas into the airway circuit;

[0013] After injecting a fixed amount of gas, the change in gas pressure within the airway circuit is detected.

[0014] The total volume change within the airway circuit is calculated based on Boyle's law, and then the functional residual capacity of the animal is calculated.

[0015] Reactivate the inspiratory and expiratory valves of the animal ventilator to restore normal breathing in the experimental animal.

[0016] Preferably, the method for obtaining the airway circuit volume in the initial state is as follows: calculate the pipe volume based on the length and diameter of the silicone tube.

[0017] Preferably, the method for obtaining the airway circuit volume in the initial state is as follows:

[0018] Close the breathing valve of the animal ventilator to ensure that all ports of the airway circuit are sealed.

[0019] Detect the gas pressure in the airway circuit under initial conditions;

[0020] Control the metered injection device to inject a metered amount of gas into the airway circuit;

[0021] Detect the change in gas pressure within the airway circuit after a quantitative amount of gas is injected;

[0022] The airway circuit volume in the initial state is calculated based on Boyle's law.

[0023] Preferably, after the experimental animal recovers to a normal respiratory rate, the control console automatically repeats the functional residual capacity (FRC) detection, and the average value of multiple measurements is taken as the final FRC measurement value of the experimental animal.

[0024] An animal functional residual volume detection device based on the above detection method includes: a plethysmography box, which is connected to the inspiratory valve and expiratory valve of an animal ventilator, the output end of a micro-injection pump, and the sensing end of a gas pressure sensor in a signal conditioner via a sealed ventilation pipe. The animal ventilator, the micro-injection pump, and the signal conditioner are connected to the host of the control console via electrical cables.

[0025] Preferably, the signal conditioner is equipped with a volumetric plethysmography chamber pressure sensor, an airway pressure sensor, and a processing module; the volumetric plethysmography chamber pressure sensor is used to monitor and provide feedback on changes in gas pressure inside the volumetric plethysmography chamber, and the airway pressure sensor is used to monitor and provide feedback on changes in gas pressure within the airway circuit connected to the lungs of the experimental animal.

[0026] Preferably, the volumetric recording chamber is hermetically connected to the signal conditioner via a volumetric recording chamber pipe; the proximal end of the volumetric recording chamber pipe passes through an air hole on the side wall of the volumetric recording chamber and enters the interior of the volumetric recording chamber, and the distal end of the volumetric recording chamber pipe is hermetically connected to the sensing end of the volumetric recording chamber pressure sensor in the signal conditioner.

[0027] Preferably, the volumetric recording box is closedly connected to the signal conditioner, the microinfusion pump, and the animal respiratory ventilator via an inhalation tube and an exhalation tube, respectively.

[0028] The proximal ends of the inhalation tube and the exhalation tube pass through the air holes on the side wall of the plethysmography chamber and enter the interior of the plethysmography chamber, where they converge to form a Y-shaped tube. The proximal end of the Y-shaped tube can be directly inserted into the airway of the experimental animal and communicate with the lungs of the experimental animal.

[0029] The distal end of the exhalation tubing is sealed to the exhalation valve of the animal ventilator.

[0030] The distal end of the inhalation tubing is divided into three branches. One branch is sealed to the inhalation valve of the animal ventilator. The second branch at the distal end of the inhalation tubing is sealed to the sensing end of the airway pressure sensor in the signal conditioner. The last branch at the distal end of the inhalation tubing is sealed to the output end of the micro-injection pump.

[0031] Preferably, the body scanning box tubing, the inhalation tubing, and the exhalation tubing are made of silicone material, and the interfaces between the tubing and between the tubing and the instrument are detachable and sealed.

[0032] Preferably, the body scanning chamber pressure sensor and the airway pressure sensor are silicon micro-pressure sensors.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. Accurate measurement: Precisely measures the amount of gas remaining in the lungs of an animal at the end of a calm exhalation;

[0035] The animal's lungs are considered as a closed container. By injecting a fixed amount of gas into this container and measuring the pressure change inside, the volume of the container can be directly calculated. This direct measurement is therefore quite accurate. At the end of a calm exhalation, the airway pressure is 0. At this point, the software controls the animal's ventilator to close the valve, sealing the airway. Simultaneously, the software controls a micro-infusion pump to inject a fixed amount of gas into the airway, causing a pressure change. Boyle's law is then used to accurately calculate the amount of gas remaining in the lungs at this time.

[0036] 2. High detection accuracy: The pressure sensor uses a silicon micro-pressure sensor with an accuracy of 0.05% and temperature compensation, which can accurately measure minute pressure changes; the data acquisition card has a 16-bit width and a synchronous sampling frequency of up to 200KHz, which can accurately measure minute pressure change signals; the inspiratory and expiratory valves of the animal ventilator use high-frequency solenoid valves with a maximum operating frequency of 150 times / second, which can quickly close the airway when the FRC test is started, further improving the accuracy of FRC calculation;

[0037] 3. Easy to operate and animal-friendly: The entire testing process is automatically controlled by software. During the testing process, only simple operations such as animal anesthesia and tracheal intubation and test initiation are required. No complicated equipment debugging is required, which lowers the operating threshold.

[0038] Typically, after initiating FRC measurement, the software identifies the end of expiration based on the inspiratory volume signal obtained from the plethysmography chamber, then closes the inspiratory and expiratory valves of the animal ventilator, waiting for the animal to exhibit spontaneous breathing signals. The animal's inspiratory volume is indirectly calculated by detecting pressure changes in the closed plethysmography chamber, and simultaneously, the animal's functional residual capacity (FRC) is indirectly calculated using Boyle's law by detecting the airway pressure (i.e., intrapulmonary pressure) at the end of inspiration. This method has two drawbacks: First, the animal's inspiratory volume is obtained indirectly and cannot accurately reflect the animal's inspiratory volume; second, when the animal is sealed, due to moderate to deep anesthesia, it is necessary to wait for a period of time for spontaneous breathing to occur, and the air pressure fluctuation signal is weak, resulting in large measurement errors and easily leading to animal asphyxiation and death.

[0039] The nitrogen flushing method has a long detection time. Smaller animals have a smaller inhalation volume, and the gas flushing time is longer. Existing gas control, acquisition and analysis modules have difficulty accurately controlling the inhalation and measurement of nitrogen, resulting in a large measurement error.

[0040] Radiographic imaging can accurately measure the functional residual gas of animals through tomographic scanning, but the equipment is expensive, requires specialized radiation protection equipment, is complex to operate, and poses radiation safety hazards, making it difficult to promote its application in conventional laboratories. Attached Figure Description

[0041] Figure 1 A flowchart illustrating the steps of a method for detecting functional residual capacity in animals;

[0042] Figure 2 This is a connection block diagram of an animal functional residual gas volume detection device.

[0043] In the diagram: 1. Pulse recording chamber; 2. Animal ventilator; 3. Signal conditioner; 4. Control console; 5. Microinfusion pump; 6. Pulse recording chamber pressure sensor; 7. Airway pressure sensor; 8. Processing module; 9. Pulse recording chamber tubing; 10. Inspiratory tubing; 11. Exhalation tubing; 12. Laboratory animal. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Furthermore, elements in this invention are referred to as being "fixed to" or "set on" another element, which may be directly on the other element or may also include an intervening element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or may also include an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementations.

[0046] According to Boyle's law, when the temperature and mass of a gas are constant, the product of its volume and pressure is constant, that is: (in (for constants)

[0047] When the volume of gas changes The change, before and after the change, satisfies the following equation:

[0048]

[0049] Note: Among them , The pressure and volume before the change, , This represents the change after the change.

[0050] From the aforementioned formula, we can see that:

[0051]

[0052] but ;(because Much larger ).

[0053] The above formula shows that volume change With pressure changes They are directly proportional.

[0054] In existing technologies, using pressure changes in a plethysmography chamber as a parameter for measuring functional residual capacity is an indirect measurement: the pressure changes in the plethysmography chamber originate from the compression of gas inside the chamber by the thoracic cavity during animal respiration, rather than directly testing changes in the animal's lung volume; and since animals vary in size and there are individual differences, the results of indirect measurements are often less accurate.

[0055] When conducting functional residual capacity (FRC) tests on animals, it is necessary to connect the animal's lungs to the breathing valves of the animal ventilator by inserting a tube into the animal's airway, thus artificially constructing an airway circuit. Whether measured in advance or calculated based on the length and diameter of the tube, the volume of this airway circuit can be considered a known parameter.

[0056] Assume the volume of a certain section of the airway circuit is During animal respiration, the total volume of the animal's lungs plus the airway environment is... When the animal is at the end of exhalation At this time, there is no airflow in the lungs and airways, and the intrapulmonary pressure equals the airway pressure. If, in the aforementioned airway environment, a metered gas injection is artificially controlled, for example, the injected metered gas volume is... At this time, the slight change in pressure within the airway is ,pass This allows us to calculate the total volume of the animal's lungs plus airway after injecting a fixed amount of gas. Using the changed total volume Subtract the known airway volume It is the functional residual capacity (FRC) of an animal at the end of a calm exhalation.

[0057] The airway volume is much smaller than that of the plethysmography chamber, so the pressure changes caused by the injection of a small amount of gas will be much more significant. At the same time, because the airway can be directly connected to the animal's lungs through intubation, testing the pressure changes in the airway is equivalent to directly testing the pressure changes in the animal's lungs, which is much more accurate than testing the pressure changes in the plethysmography chamber.

[0058] Based on the above improvement ideas, such as Figures 1-2As shown, the present invention provides a method and apparatus for detecting animal functional residual capacity. Instead of using the volume increment and pressure increment of the plethysmography chamber as calculation parameters, it uses the volume increment and pressure increment of the airway circuit directly connected to the animal's lungs as parameters to calculate the animal's functional residual capacity, changing the detection method of animal functional residual capacity from indirect testing to direct testing.

[0059] Specifically, mice are used as experimental animals, such as Figure 1 As shown, the present invention provides a method for detecting functional residual capacity in animals, comprising the following steps:

[0060] S1. Construct a measurable airway circuit to obtain the airway circuit volume in the initial state;

[0061] Select appropriate lengths of silicone tubing and connect them sequentially to the necessary testing equipment, such as a volumetric recording chamber, animal ventilator, quantitative injection device, pressure sensor, etc.

[0062] Ensure that the airway circuit is in a sealed connection state;

[0063] When the animal is not in place, the volume of the recorded airway circuit is Volumetric recording box volume ;

[0064] There are two methods for calculating the airway circuit volume in the initial state:

[0065] Method 1: Calculate the pipe volume based on the length and diameter of the silicone tube. ;

[0066] The second method: Close the breathing valve of the animal ventilator to ensure that all ports of the airway circuit are sealed; check the gas pressure in the airway circuit under initial conditions. Control the metered injection device to inject a metered amount of gas into the airway circuit. ; Detect the change in gas pressure within the airway circuit after injecting a fixed amount of gas. ; Calculate according to Boyle's law ;

[0067] S2. Animal preparation:

[0068] Select experimental animals of appropriate weight, perform endotracheal intubation after anesthesia to connect their lungs with the airway circuit, and close the volume plethysmography box to make it airtight.

[0069] For example, in this embodiment, SPF-grade mice weighing 17-25g can be selected, anesthetized (e.g., sodium pentobarbital, dose of 75mg / kg), and after the mice are in a state of deep anesthesia (no limb reflexes, stable breathing), they are placed in a plethysmography chamber, and the silicone tube pre-installed in the plethysmography chamber is inserted into the mouse's airway. The plethysmography chamber is then closed to create a sealed environment. The breathing valve of the animal ventilator is connected to the animal's lungs through the airway circuit to ensure that the animal can breathe normally in the sealed space of the plethysmography chamber.

[0070] Use the control host to control the opening and closing of the breathing valve of the animal ventilator;

[0071] S3. Mark the animal's respiratory cycle and identify the end-expiratory time point:

[0072] After placing the animals, the volume change of the plethysmography chamber was calculated by detecting the changes in gas pressure inside the chamber during the mouse's respiration. and the change in flow rate within the recording box ;

[0073] Based on the change in flow velocity inside the recording box Record the respiratory cycle of mice. It also identifies the end of expiration time point (end of expiration in mice) for each respiratory cycle. ;

[0074] S4. Close the inspiratory and expiratory valves of the animal ventilator at the end of the animal's expiration time and check the gas pressure in the airway circuit.

[0075] At the end of expiration in mice ( At any moment, quickly close the inhalation and exhalation valves to ensure that the volumetric recording box and the internal airway circuit are completely sealed.

[0076] At this time, the gas pressure in the airway circuit fed back by the pressure sensor is At this point, there is no gas flow in the mouse's lungs and respiratory tract, and the intrapulmonary pressure is equal to the airway pressure. ;

[0077] S5. Inject a measured amount of gas into the airway circuit;

[0078] The metered injection device is used to inject a metered amount of gas into the airway circuit; the injection volume... ;

[0079] For example, in this embodiment, injecting a quantitative gas into the mouse can be... Different injection volumes are selected based on the body size of the animal being tested;

[0080] S6. After injecting a fixed amount of gas, detect the change in gas pressure in the airway circuit.

[0081] After the gas injection is complete, close the output of the metering injection device, detect the pressure signal change value fed back by the pressure sensor associated with the airway circuit, and calculate... ;

[0082] In this embodiment, the change in minute pressure values ​​within the lungs of mice after injecting 0.1 ml of gas is studied.

[0083] S7. Calculate the total volume change in the airway circuit according to Boyle's law, and then calculate the animal functional residual capacity (FRC).

[0084] According to the formula Calculate the total volume of the lungs and airway tubing at the end of expiration in mice. ;

[0085] Calculate the functional residual capacity of mice ;

[0086] S8. Reopen the inspiratory and expiratory valves of the animal ventilator to restore normal breathing in the experimental animal;

[0087] By controlling the host to open the breathing valve of the animal ventilator, the output end of the quantitative injection device is kept closed, so that the experimental animal can resume normal breathing.

[0088] S9. Repeat S3 to S8, and take the average value after multiple measurements.

[0089] For example, in this embodiment, after a 10-second interval, once the mouse’s breathing returns to a normal frequency, the console program automatically repeats the functional residual capacity (FRC) measurement, repeating the measurement a total of 5 times. Finally, the average of the 5 measurements is taken as the final FRC measurement value for this mouse.

[0090] Based on the above detection method, the present invention also provides a device for detecting functional residual capacity in animals. For example... Figure 2 As shown, the device includes a volumetric recording box 1, which is an airtight empty box structure with several air holes on the side wall that can be sealed with rubber stoppers as needed. Through these air holes, the volumetric recording box 1 is connected to the inspiratory and expiratory valves of the animal ventilator 2, the output end of the micro-infusion pump 5, and the sensing end of the gas pressure sensor in the signal conditioner 3 via sealed ventilation pipes. The animal ventilator 2, the micro-infusion pump 5, and the signal conditioner 3 are connected to the main unit of the control console 4 via electrical cables.

[0091] The plethysmography chamber 1 is used to place the anesthetized experimental animals 12 and provide them with a relatively closed breathing space. The experimental animals 12 are often small to medium-sized animals, and it is difficult to determine their respiratory cycle if they are not placed in a closed environment. Different volume models of plethysmography chamber 1 are selected according to the different species of experimental animals 12, and the volume specifications of the plethysmography chamber 1 should be adapted to the body size of the experimental animals 12.

[0092] Animal ventilator 2 is used to provide gas to maintain normal breathing for laboratory animals 12 under anesthesia, and to control the amount and cycle of respiratory gas input; the product model of animal ventilator 2 should be adapted to the body size and weight of laboratory animals 12.

[0093] Currently, there are various models of animal ventilators on the market. These ventilators typically include functional modules such as an inspiratory valve, expiratory valve, flow rate regulating valve, air pump, and microprocessor control circuit. The main working principle of an animal ventilator is as follows: the inspiratory and expiratory valves are high-frequency solenoid valves, which alternately open and close to switch the animal between inhalation and exhalation. The flow rate regulating valve adjusts the inspiratory airflow rate to a suitable value. The air pump provides compressed gas to the ventilator. The microprocessor control circuit can receive user input parameters to control the adjustment of the respiratory rate and respiratory ratio.

[0094] The signal conditioner 3 is equipped with a volume plethysmography chamber pressure sensor 6, an airway pressure sensor 7, and a processing module 8. The volume plethysmography chamber pressure sensor 6 is used to monitor and provide feedback on the gas pressure changes inside the volume plethysmography chamber 1, and the airway pressure sensor 7 is used to monitor and provide feedback on the gas pressure changes inside the airway circuit connected to the lungs of the experimental animal 12.

[0095] The volumetric plethysmography chamber pressure sensor 6 and the airway pressure sensor 7 can be silicon micro-pressure sensors. The airway pressure sensor 7, which is used to detect the airway circuit pressure of the experimental animal 12, has a measurement range of 5.6 kPa and an accuracy of 0.05%. The volumetric plethysmography chamber pressure sensor 6, which is used to detect the gas pressure inside the volumetric plethysmography chamber 1, has a measurement range of 1 kPa and an accuracy of 0.05%.

[0096] Processing module 8 includes a signal amplification module and a data acquisition module. The signal amplification module is connected to the body contouring chamber pressure sensor 6 and the airway pressure sensor 7 to amplify the weak signals from the sensors. The data acquisition module performs analog-to-digital conversion of the amplified signals and transmits them to the control console 4 via a USB interface. The bit width of the analog-to-digital conversion is 16 bits, and the maximum sampling frequency of a single channel can reach 200K / s, allowing for the simultaneous acquisition of multiple signals.

[0097] The control console 4 is used to receive data information fed back by the processing module 8 in the signal conditioner 3, process and record the data information, and send control commands to the animal ventilator 2 and the micro-infusion pump 5 based on the data processing results.

[0098] The key to this invention is how to construct a measurable airway circuit between the animal placed inside the plethysmography chamber 1 and external equipment. In the embodiments of this application, necessary air vents are formed on the side wall of the plethysmography chamber 1. The interior of the plethysmography chamber 1 is connected to the outside world through a silicone tube passing through the air vents. The silicone tube has a certain degree of elasticity; when the silicone tube passes through the air vents, the rest of the plethysmography chamber 1 is in a sealed state except for the internal channel of the silicone tube. The following description further describes the construction of a measurable animal airway circuit, using the interior of the plethysmography chamber 1 as the proximal end and the exterior of the plethysmography chamber 1 as the distal end.

[0099] The volumetric recording chamber 1 is sealed to the signal conditioner 3 through the volumetric recording chamber pipe 9; the proximal end of the volumetric recording chamber pipe 9 passes through the air hole on the side wall of the volumetric recording chamber 1 and enters the interior of the volumetric recording chamber 1, and the distal end of the volumetric recording chamber pipe 9 is sealed to the sensing end of the volumetric recording chamber pressure sensor 6 in the signal conditioner 3.

[0100] The volumetric recording chamber 1 is sealed to the signal conditioner 3, the microinfusion pump 5, and the animal ventilator 2 via the inhalation tube 10 and the exhalation tube 11, respectively. The proximal ends of the inhalation tube 10 and the exhalation tube 11 pass through the air holes on the side wall of the volumetric recording chamber 1 and enter the interior of the volumetric recording chamber 1. They converge inside the volumetric recording chamber 1 to form a Y-shaped tube. The proximal end of the Y-shaped tube can be directly inserted into the airway of the experimental animal 12 and communicate with the lungs of the experimental animal 12.

[0101] In this application, the junction of the inspiratory tube 10 and the expiratory tube 11 is located inside the plethysmography chamber 1. During the testing process, the animal's limbs reflex to the intubation tube under deep anesthesia, and the animal's throat will involuntarily push the breathing tube out of the chamber, causing the tube to shift. Placing the junction of the Y-shaped tubes inside the plethysmography chamber 1 makes it difficult for the animal to completely push the tube out of the chamber, ensuring a more stable respiratory and circulatory pathway during the test.

[0102] The distal end of the expiratory tubing 11 is sealed to the expiratory valve of the animal ventilator 2. The distal end of the inspiratory tubing 10 branches into three paths, one of which is sealed to the inspiratory valve of the animal ventilator 2. When the inspiratory and expiratory valves of the animal ventilator 2 are working, the animal ventilator 2, inspiratory tubing 10, and expiratory tubing 11 form a complete respiratory airway circulation pathway with the lungs of the experimental animal 12. The second branch at the distal end of the inspiratory tubing 10 is sealed to the sensing end of the airway pressure sensor 7 in the signal conditioner 3. That is, the airway pressure sensor 7 monitors and provides feedback on the gas pressure changes in the airway circuit that directly connects to the lungs of the experimental animal 12. The last branch at the distal end of the inspiratory tubing 10 is sealed to the output end of the micro-infusion pump 5. The body plethysmography chamber tubing 9, inspiratory tubing 10, and expiratory tubing 11 are made of silicone material, and the interfaces between the tubing and between the tubing and the instruments are detachable and sealed for adaptation.

[0103] The inhalation tube 10 and the expiratory tube 11 constitute the airway circuit. It is understandable that the airway circuit may vary depending on factors such as the experimental site, the size of the experimental animal, and the testing equipment.

[0104] The micro-injection pump 5 has a detachable syringe containing a metered amount of gas. The output of the micro-injection pump 5 is sealed to the inhalation tubing 10, and the control terminal of the micro-injection pump 5 is electrically connected to the control console 4. It is used to inject a metered amount of gas into the inhalation tubing 10, which is the airway circuit of the experimental animal 12. The micro-injection pump 5 can be an ISPLab01-Pro model manufactured by Duko Industrial Technology (Shanghai) Co., Ltd. This model can securely hold syringes of different sizes and includes an RS232 communication interface, enabling it to receive control parameters transmitted from the control console 4 and precisely change the flow rate and total volume of the injected gas through an automated program.

[0105] Unlike existing technologies, in the embodiments of this application, a micro-injection pump 5 is added to the animal's airway circuit. The gas pressure parameter inside the plethysmography chamber 1 is no longer directly involved in the calculation of the animal's respiratory volume, but is used as a comparison parameter during the animal's respiratory cycle to identify the time point for initiating FRC measurement in the animal's quiet end-expiratory state. The parameters directly involved in the calculation of the animal's respiratory volume are the volume of gas quantitatively injected into the micro-injection pump 5 and the tubing volume of the airway circuit, which is smaller than the volume of the plethysmography chamber 1. Because the airway circuit can directly connect to the lungs of the animal being tested, the improved measurement method can greatly improve the measurement accuracy of functional residual capacity (FRC) in animals at the quiet end-expiratory state.

[0106] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0107] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for detecting functional residual capacity in animals, characterized in that, Includes the following steps: A measurable airway circuit is constructed to obtain the airway circuit volume in its initial state; appropriate lengths of silicone tubing are selected and connected sequentially to the necessary test equipment, including a volumetric recording box, an animal ventilator, a quantitative injection device, and a pressure sensor; the necessary test equipment is controlled and operated through a control host. Animal preparation: Select experimental animals of appropriate weight, anesthetize them and perform endotracheal intubation to connect their lungs to the airway circuit, and close the volume plethysmography box to keep the experimental animals in a closed environment. By recording changes in gas pressure inside the plethysmography chamber, the animal's respiratory cycle can be marked, and the end-expiratory time point of the animal can be identified. At the end of the animal's expiration time, close the inspiratory and expiratory valves of the animal ventilator and detect the current gas pressure in the airway circuit; Inject a measured amount of gas into the airway circuit; After injecting a fixed amount of gas, the change in gas pressure within the airway circuit is detected. The total volume change within the airway circuit is calculated based on Boyle's law, and then the functional residual capacity of the animal is calculated. Reactivate the inspiratory and expiratory valves of the animal ventilator to restore normal breathing in the experimental animal.

2. The detection method according to claim 1, characterized in that, The method for obtaining the airway circuit volume in the initial state is as follows: calculate the pipe volume based on the length and diameter of the silicone tube.

3. The detection method according to claim 1, characterized in that, The method for obtaining the airway circuit volume in the initial state is as follows: Close the breathing valve of the animal ventilator to ensure that all ports of the airway circuit are sealed. Detect the gas pressure in the airway circuit under initial conditions; Control the metered injection device to inject a metered amount of gas into the airway circuit; Detect the change in gas pressure within the airway circuit after a quantitative amount of gas is injected; The airway circuit volume in the initial state is calculated based on Boyle's law.

4. The detection method according to claim 1, characterized in that, After the experimental animals regained their normal respiratory rate, the control console automatically repeated the functional residual capacity (FRC) detection, and the average value of multiple measurements was taken as the final FRC measurement value of the experimental animals.

5. An animal functional residual capacity detection device according to claim 1, characterized in that, include: The volumetric recording box (1) is connected to the inhalation valve and expiration valve of the animal ventilator (2), the output end of the micro-injection pump (5), and the sensing end of the gas pressure sensor in the signal conditioner (3) through a sealed ventilation pipe. The animal ventilator (2), the micro-injection pump (5), and the signal conditioner (3) are connected to the host of the control console (4) through circuit cables.

6. The detection device according to claim 5, characterized in that, The signal conditioner (3) is equipped with a volumetric plethysmography chamber pressure sensor (6), an airway pressure sensor (7), and a processing module (8). The volumetric plethysmography chamber pressure sensor (6) is used to monitor and feedback the gas pressure changes inside the volumetric plethysmography chamber (1), and the airway pressure sensor (7) is used to monitor and feedback the gas pressure changes in the airway circuit connected to the lungs of the experimental animal (12).

7. The detection device according to claim 6, characterized in that, The volumetric recording box (1) is sealed to the signal conditioner (3) through the volumetric recording box pipe (9); the proximal end of the volumetric recording box pipe (9) passes through the air hole on the side wall of the volumetric recording box (1) and enters the interior of the volumetric recording box (1); the distal end of the volumetric recording box pipe (9) is sealed to the sensing end of the volumetric recording box pressure sensor (6) in the signal conditioner (3).

8. The detection device according to claim 7, characterized in that, The volumetric recording box (1) is connected in a sealed manner to the signal conditioner (3), the micro-injection pump (5) and the animal ventilator (2) through the inhalation tube (10) and the exhalation tube (11), respectively. The proximal ends of the inhalation tube (10) and the exhalation tube (11) pass through the air holes on the side wall of the volumetric recording box (1) and enter the interior of the volumetric recording box (1), and converge inside the volumetric recording box (1) to form a Y-shaped tube. The proximal end of the Y-shaped tube can be directly inserted into the airway of the experimental animal (12) and communicate with the lungs of the experimental animal (12). The distal end of the exhalation conduit (11) is sealed to the exhalation valve of the animal ventilator (2); The distal end of the inhalation conduit (10) is divided into three branches, one of which is sealed to the inhalation valve of the animal ventilator (2); the second branch at the distal end of the inhalation conduit (10) is sealed to the sensing end of the airway pressure sensor (7) in the signal conditioner (3); and the last branch at the distal end of the inhalation conduit (10) is sealed to the output end of the micro-injection pump (5).

9. The detection device according to claim 8, characterized in that, The body tracing box tube (9), the inhalation tube (10) and the exhalation tube (11) are made of silicone material, and the interfaces between the tubes and between the tubes and the instruments are detachable and sealed.

10. The detection device according to claim 9, characterized in that, The body scanning chamber pressure sensor (6) and the airway pressure sensor (7) are silicon micro-pressure sensors.

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