A transcutaneous blood gas monitor calibration device and method

Abstract

The application discloses a transcutaneous blood gas monitor calibration device and method, wherein the calibration device comprises: a gas-liquid equilibrium module, comprising a balance chamber loaded with a balance solution, wherein an exhaust port communicating with the atmosphere is arranged on the balance chamber, and an electrode interface covered by a waterproof and air-permeable film is arranged at the bottom of the balance chamber; a standard gas module, which is communicated with the balance chamber and is used for conveying standard gas with a set oxygen concentration and a set carbon dioxide concentration into the balance solution; a constant temperature control module, which is used for realizing temperature control of the balance chamber; and a measurement module, comprising a temperature measurement probe arranged at the electrode interface and an air pressure sensor arranged in the atmosphere. The application can effectively simulate the human subcutaneous tissue liquid gas diffusion scene and the constant temperature physiological environment, greatly reduces the difference between the calibration working condition and the real use scene in clinic, thereby realizing the multi-parameter collaborative calibration of the transcutaneous blood gas monitor, and greatly improving the calibration accuracy of the transcutaneous blood gas monitor.

Description

Technical Field

[0001] This invention relates to a calibration device and method for a transcutaneous blood gas monitor, belonging to the field of medical device testing technology. Background Technology

[0002] Transcutaneous blood gas monitoring involves heating electrodes placed on the skin surface to dilate local capillaries, increase skin permeability, and increase blood flow. This arterializes the capillaries, allowing gas in the blood vessels to diffuse through the vessel walls and interstitial spaces, layer by layer, into the electrodes. Ultimately, the transcutaneous oxygen partial pressure and transcutaneous carbon dioxide partial pressure (tcpO2 and tcpCO2) in the subcutaneous tissue are measured. It is widely used for neonatal oxygen therapy, mechanical ventilation of premature infants, and blood gas monitoring in children with shock and hypoperfusion.

[0003] A percutaneous blood gas monitor typically consists of a probe, a main unit, and connecting lines. The probe contains a sensor that is attached to the skin surface to detect tcpO2 and tcpCO2. The main unit has a built-in temperature limiter, signal processing system, microprocessor, and display. The connecting lines are mainly responsible for transmitting signals between the probe and the main unit.

[0004] For the calibration testing of transcutaneous blood gas analyzers, existing technologies often involve placing the detection electrode in a measuring gas chamber and measuring the partial pressure by inputting standard gases of different concentrations. For example, existing patent CN 201911311294.9 provides a transcutaneous partial pressure analyzer calibration device and method. On one hand, by installing the electrode under test on a foam material, the heating temperature of the electrode probe is measured by an internal sensor, thereby calculating the difference between the maximum temperature and the control temperature and the temperature fluctuation, thus evaluating the temperature performance of the transcutaneous partial pressure analyzer. On the other hand, by installing the electrode under test in a mixing gas chamber and heating standard gases of different concentrations before introducing them into the mixing gas chamber, the measurement data results of the device under test are recorded and compared to calculate the indication error and nonlinearity error.

[0005] While the above calibration method takes into account the influence of gas temperature and concentration on gas partial pressure, the pure gas phase environment used differs greatly from the real clinical scenario of fluid-gas coexistence in human subcutaneous tissue, making it difficult to guarantee the calibration accuracy of the percutaneous blood gas monitor. Furthermore, separating electrode probe temperature measurement and partial pressure measurement into two modules fails to fully consider the influence of factors such as percutaneous monitoring electrode temperature and gas diffusion characteristics, making it impossible to achieve simultaneous and accurate calibration of multiple parameters such as electrode temperature, gas-liquid balance process, and repeatability. Summary of the Invention

[0006] Purpose of the invention: To address the problems existing in the prior art, the present invention provides a transcutaneous blood gas monitor calibration device and method, which can effectively complete the multi-parameter collaborative calibration of the transcutaneous blood gas monitor in the case of fluid and gas diffusion in human subcutaneous tissue, thereby accurately and efficiently completing the calibration of the transcutaneous blood gas monitor.

[0007] Technical solution: To achieve the above objectives, the present invention provides a transcutaneous blood gas monitor calibration device, comprising:

[0008] A gas-liquid balance module includes a balance chamber containing a balance solution, an exhaust port connected to the atmospheric environment on the balance chamber, and an electrode interface covered with a waterproof and breathable membrane at the bottom of the balance chamber for electrode installation of a transcutaneous blood gas monitor.

[0009] The standard gas module, which is connected to the equilibrium chamber, is used to deliver standard gases with set oxygen and carbon dioxide concentrations into the equilibrium solution.

[0010] Thermostatic control module is used to control the temperature of the equilibrium chamber;

[0011] The measurement module includes a temperature probe located at the electrode interface and a pressure sensor located in the atmospheric environment.

[0012] Specifically, the equilibrium solution is venous blood or a buffer solution, and the standard gas is a standard substance of nitrogen-carbon dioxide and oxygen mixture or a standard gas mixture generated by a precision gas mixing system.

[0013] Specifically, the exhaust ports are located at the top of the balance chamber, and the bottom side of the balance chamber is provided with an air inlet for connecting to the standard gas module. Both the exhaust ports and the air inlets are provided with waterproof and breathable membranes.

[0014] Specifically, the constant temperature control module includes a liquid circulation channel filled with circulating liquid, an electric heater, a temperature sensor, and a liquid circulation pump. The liquid circulation channel is distributed around or spirally distributed within the equilibrium chamber. The electric heater is used to heat the circulating liquid in the liquid circulation channel, the temperature sensor is used to monitor the temperature of the circulating liquid in the liquid circulation channel, and the liquid circulation pump is used to realize the circulation flow of the circulating liquid in the liquid circulation channel.

[0015] Furthermore, the calibration device also includes a humidity control module, and the standard gas module is connected to the equilibrium chamber through the humidity control module to realize humidity control of the standard gas.

[0016] Specifically, the humidity control module includes a humidification chamber filled with pure water, and the standard gas generated by the standard gas module flows through the humidification chamber, is saturated with water vapor by water bubbling, and then enters the balance chamber.

[0017] Furthermore, the measurement module also includes a humidity sensor for collecting and balancing the relative humidity of indoor gases.

[0018] Furthermore, the balance chamber is also provided with a hollow fiber layer made of waterproof and breathable material.

[0019] Furthermore, the present invention also provides a calibration method based on the above-mentioned transcutaneous blood gas monitor calibration device, comprising the following steps:

[0020] The set amount of equilibration solution is filled into the equilibration chamber, and the electrodes of the transcutaneous blood gas monitor are installed at the electrode interface.

[0021] Temperature control of the equilibrium chamber is achieved through a constant temperature control module;

[0022] The standard gas module delivers standard gases with set oxygen and carbon dioxide concentrations into the equilibrium solution to achieve gas partial pressure balance between the liquid and the gas.

[0023] After gas-liquid balance is achieved, data is collected through the measurement module, thereby realizing multi-parameter collaborative calibration of the transcutaneous blood gas monitor.

[0024] Specifically, the multi-parameter collaborative calibration includes one or more of the following items:

[0025] ①Cumulative duration of electrode temperature exceeding limit:

[0026] Set the electrode temperature of the percutaneous blood gas monitor. After the electrode temperature reaches the set value, collect the electrode temperature at set time intervals through the temperature probe. Within the observation window from when the electrode temperature reaches the set value, count the cumulative time for the measured temperature to exceed the set temperature and reach the limit threshold. This is the cumulative time for the electrode temperature to exceed the limit.

[0027] ②Indication error and repeatability:

[0028] The electrode temperature and equilibrium chamber temperature of the transcutaneous blood gas monitor are set. After the temperature reaches the set value, standard gases with set oxygen and carbon dioxide concentrations are introduced into the equilibrium chamber. After the transcutaneous blood gas monitor readings stabilize and remain stable for no less than the set time, the transcutaneous blood gas monitor readings are continuously collected and recorded n times. Then, the absolute error or relative error of the readings is calculated based on the average value of the n measurements and the standard value of the gas partial pressure in the equilibrium chamber as a characterization of the reading error. The relative standard deviation is also calculated as a characterization of repeatability. The standard value of the gas partial pressure in the equilibrium chamber is calculated based on the atmospheric pressure measured by the barometer and the oxygen and carbon dioxide concentrations in the standard gas.

[0029] ③ Linearity plus hysteresis:

[0030] Set the electrode temperature and equilibrium chamber temperature of the transcutaneous blood gas analyzer. After the temperature reaches the set value, introduce the first set of standard gases into the equilibrium chamber. After the transcutaneous blood gas analyzer reading stabilizes and remains stable for at least the set time, continuously collect and record the transcutaneous blood gas analyzer readings m times. Switch to introducing the second set of standard gases. After the transcutaneous blood gas analyzer reading stabilizes and remains stable for at least the set time, continuously collect and record the transcutaneous blood gas analyzer readings m times. Switch back to introducing the first set of standard gases. After the transcutaneous blood gas analyzer reading stabilizes and remains stable for at least the set time, continuously collect and record the transcutaneous blood gas analyzer readings m times. Calculate the linearity plus hysteresis based on the average value of the transcutaneous blood gas analyzer readings during the first introduction of the first set of standard gases, the average value of the transcutaneous blood gas analyzer readings during the second introduction of the second set of standard gases, and the average value of the transcutaneous blood gas analyzer readings during the second introduction of the first set of standard gases.

[0031] Beneficial effects: This invention abandons the traditional pure gas phase calibration mode, effectively simulates the liquid-gas diffusion scenario in human subcutaneous tissue through a gas-liquid balance module, and achieves a constant temperature physiological environment through a constant temperature control module. Thus, under controlled conditions (such as temperature and air pressure), the gas partial pressure balance between liquid and gas is achieved, thereby enabling multi-parameter collaborative calibration of the transcutaneous blood gas monitor. This provides a scientific, standardized, and repeatable calibration method for the transcutaneous blood gas monitor, thus providing important guarantees for the quality performance and safety of use of the transcutaneous blood gas monitor. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the transcutaneous blood gas monitoring calibration device in an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the gas-liquid balance module in an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram of the control module in an embodiment of the present invention.

[0035] The diagram includes: 1. Standard gas module, 2. Humidification chamber, 21. Pure water, 3. Equilibrium chamber, 31. Equilibrium solution, 32. Exhaust port, 33. Air inlet, 34. Mounting port, 35. Electrode interface, 36. Waterproof and breathable membrane, 37. Hollow fiber layer, 4. Liquid circulation channel, 5. Temperature probe, 6. Humidity sensor, 7. Pressure sensor. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0037] Reference Figure 1 This invention provides a transcutaneous blood gas monitor calibration device, mainly comprising:

[0038] The gas-liquid balance module includes a balance chamber 3 containing a balance solution 31, an exhaust port 32 connected to the atmospheric environment on the balance chamber 3, and an electrode interface 35 covered with a waterproof and breathable membrane 36 at the bottom of the balance chamber 3 for electrode installation of a transcutaneous blood gas monitor.

[0039] Standard gas module 1, which is connected to equilibrium chamber 3, is used to deliver standard gases with set oxygen and carbon dioxide concentrations into equilibrium solution 31.

[0040] The constant temperature control module is used to control the temperature of the balance chamber 3;

[0041] The measurement module includes a temperature probe 5 located at the electrode interface 35 and a pressure sensor 7 located in the atmospheric environment.

[0042] This invention utilizes the gas tension method (i.e., the equilibrium of gas partial pressures between liquid and gas) to fully dissolve a standard gas mixture in a liquid sample, effectively simulating the fluid-gas diffusion scenario in human subcutaneous tissue. This provides a reliable testing scenario for the multi-parameter collaborative calibration of transcutaneous blood gas analyzers. The gas partial pressure refers to the pressure of CO2 and O2 in the gaseous phase in both liquid and gaseous environments. This invention utilizes a gas mixture of known composition flowing through a liquid sample to achieve the same gas partial pressure in both the liquid sample and the gas mixture. The partial pressure in the liquid is then detected using the electrodes of a transcutaneous blood gas analyzer, and compared with the gas partial pressure in the gas mixture to achieve accuracy analysis.

[0043] Specifically, the equilibration solution 31 may be venous blood (drawn from healthy volunteers into a collection tube containing heparin anticoagulant and stored in a 4°C refrigerator) or a buffer solution (such as a phosphate solution containing a buffer enhancer, hemoglobin buffer, and perfluorocarbon emulsion).

[0044] For example, refer to Figure 2 The balance chamber 3 adopts a cylindrical structure with a length of 5 cm and a diameter of 3 cm, thereby performing an equivalent simulation of the human arm structure; one side of the balance chamber 3 is provided with a detachable end cap, and the bottom of the end cap is provided with an air inlet 33 for connecting to the standard gas module 1; the top of the balance chamber 3 is provided with an exhaust port 32 for connecting to the atmospheric environment, and both the air inlet 33 and the exhaust port 32 are provided with waterproof and breathable membranes to prevent liquid from flowing out of the balance chamber 3.

[0045] This invention ensures that the pressure at the gas-liquid interface remains consistent with atmospheric pressure through an exhaust port 32 connected to the atmospheric environment (and also ensures the stability of the waterproof and breathable membrane). Based on the concentration of gas standard substances and atmospheric pressure data, standard values ​​for tcpO2 and tcpCO2 are calculated and then compared with the measured values ​​displayed by a transcutaneous blood gas analyzer to achieve partial pressure calibration. In simple terms, without considering the influence of gas humidity and electrode temperature, the calculation method for the standard values ​​of gas partial pressure is as follows:

[0046] tcpCO2= FCO2×pTotal, tcpO2 = FO2×pTotal (1),

[0047] Where tcpCO2 and tcpO2 represent the standard values ​​of transdermal carbon dioxide partial pressure and transdermal oxygen partial pressure, respectively, which are the standard values ​​of CO2 and O2 partial pressure in the equilibrium gas. FCO2 and FO2 are the concentrations of CO2 and O2 in the standard gas, respectively, and pTotal is the atmospheric pressure in the environment.

[0048] Specifically, the constant temperature control module is a constant temperature water circulation system, which includes a liquid circulation channel 4 filled with circulating liquid (such as pure water), an electric heater, a temperature sensor, and a liquid circulation pump. The liquid circulation channel 4 is spirally distributed in the equilibrium chamber 3, thereby achieving temperature control of the equilibrium solution 31 in the equilibrium chamber 3 through heat conduction. The electric heater is used to heat the circulating liquid in the liquid circulation channel 4, the temperature sensor is used to monitor the temperature of the circulating liquid in the liquid circulation channel 4 to achieve precise control of the heating temperature, and the liquid circulation pump is used to realize the circulation flow of the circulating liquid in the liquid circulation channel 4, thereby achieving constant temperature control of the equilibrium chamber 3 and effectively simulating the physiological temperature of 37°C of the human arm.

[0049] The reason for strictly controlling the equilibrium temperature in equilibrium chamber 3 is that the partial pressure of gases can change significantly with temperature. For example, the change in tcpO2 can reach 7% / ℃, and the change in tcpCO2 can reach 4% / ℃. Therefore, in order to ensure the accuracy and repeatability of the calibration work, it is necessary to achieve constant temperature control of the equilibrium environment.

[0050] In other embodiments, the constant temperature control module can also employ constant temperature blocks or spiral channels distributed around the balance chamber 3, or other heating devices can be used to achieve temperature control. Furthermore, insulation material can be added to the outside of the balance chamber 3 to reduce the impact of heat dissipation. To ensure that the ambient temperature inside the balance chamber 3 reaches the set value, the ambient temperature inside the balance chamber 3 can be indirectly reflected by the temperature change of the circulating fluid. Alternatively, multiple temperature sensors can be installed inside the balance chamber 3 to monitor the ambient temperature in real time, thereby achieving precise control of the ambient temperature.

[0051] Specifically, the standard gas can be selected from a nitrogen-carbon dioxide and oxygen mixed gas standard substance or a standard gas mixture generated by a precision gas mixing system. During testing, a mixed gas representing the blood gas values ​​of patients with respiratory alkalosis, normal blood, and respiratory acidosis can be selected as the standard gas, such as: 3% CO2 / 25% O2, 6.6% CO2 / 17% O2, or 12% CO2 / 7.5% O2.

[0052] For example, the standard gas module 1 includes a standard gas cylinder storing standard gas and a flow controller. The standard gas cylinder is connected to the balance chamber 3 through the flow controller to realize the output flow control of the standard gas.

[0053] Furthermore, the calibration device also includes a humidity control module. The standard gas module 1 is connected to the balance chamber 3 through the humidity control module to realize the humidity control of the standard gas and reduce the liquid loss caused by the gas being discharged through the exhaust port 32 during the gas-liquid mixing process in the balance chamber 3, which carries away water vapor.

[0054] For example, the humidity control module includes a humidification chamber 2 filled with pure water 21. The humidification chamber 2 adopts a cylindrical structure with a length of 2 cm and a diameter of 1 cm. The standard gas module 1 is connected to the balance chamber 3 through the humidification chamber 2, so that the standard gas flows through water bubbles to saturate the water vapor before entering the balance chamber 3.

[0055] In some embodiments, the standard gas module 1 may further include a gas heater for preheating the standard gas mixture to (37.0±0.1) °C, thereby ensuring that the standard gas is saturated with water vapor through water bubbling at the same temperature and pressure. Furthermore, the humidity control module may also employ other humidification devices such as atomizing humidifiers to achieve humidity control.

[0056] To determine the effect of water vapor pressure on gas partial pressure, the measurement module also includes a humidity sensor 6 for collecting the relative humidity of the equilibrium gas within the equilibrium chamber 3. Based on the temperature and humidity data, the water vapor pressure is calculated, thus eliminating its influence on gas partial pressure in the calculation, resulting in more accurate calibration results. Preferably, the top of the equilibrium chamber 3 is provided with a mounting port 34 for mounting and fixing the humidity sensor 6.

[0057] Furthermore, the equilibrium chamber 3 is also provided with a hollow fiber layer 37 made of waterproof and breathable material (for example, attached to the inner wall). The hollow fiber layer 37 can help trap gas, increase the residence time of gas in the solution, thereby accelerating the gas diffusion process in the solution, greatly reducing the equilibrium time between liquid and gas, and improving detection efficiency.

[0058] Furthermore, the calibration device also includes a control module, which is connected to the standard gas module 1, the constant temperature control module and the measurement module for signal transmission. It is used to collect data from the above modules and control the temperature and humidity parameters during the equilibration process, thereby enabling data storage and transmission.

[0059] For example, refer to Figure 3 The control module includes a signal conditioning unit, an analog-to-digital converter, a main controller, a power management unit, and a communication unit. The signal conditioning unit is electrically connected to each sensor (such as temperature probe 5, humidity sensor 6, and barometric pressure sensor 7) to condition relevant signals. The analog-to-digital converter converts analog signals into digital signals and transmits them to the main controller. The main controller communicates with the user terminal via the communication unit to receive calibration parameters and send calibration data in real time. The power management unit provides the necessary power to each unit. Furthermore, the main controller is electrically connected to the standard gas module 1 and the constant temperature control module, thereby enabling parameter control.

[0060] Furthermore, the present invention also provides a calibration method based on the above-mentioned transcutaneous blood gas monitor calibration device, comprising the following steps:

[0061] (1) Load a certain amount of pure water 21 into the humidification chamber 2, load a certain amount of equilibrium solution 31 into the equilibrium chamber 3, and fix the electrode at the electrode interface 35.

[0062] (2) Turn on the constant temperature control module to maintain the equilibrium solution 31 in the equilibrium chamber 3 at the set temperature (e.g., 37°C).

[0063] (3) The standard gas flow rate is controlled by the standard gas module 1 so that it enters the humidification chamber 2 at the same temperature and pressure and is saturated with water vapor by water bubbling;

[0064] (4) A standard gas saturated with water vapor enters the equilibrium chamber 3 and is bubbled through the equilibrium solution 31 for a period of time to achieve complete gas partial pressure equilibrium between the liquid and the gas.

[0065] (5) After gas-liquid equilibrium is reached, excess gas is discharged from exhaust port 32. After temperature and tension equilibrium, the sample is diffusely contacted by electrode interface 35 for the accuracy test of transcutaneous partial pressure. At this time, data is collected through the measurement module, thereby realizing multi-parameter collaborative calibration of the transcutaneous blood gas monitor.

[0066] It is important to note that the solution transfer should be completed quickly during loading to avoid air contamination. In other embodiments, standard gas can be introduced into the equilibration chamber 3 in advance to prevent air from entering the equilibration chamber 3. Of course, after gas-liquid equilibrium is achieved, excess gas will be discharged from the equilibration chamber 3, so no additional gas will enter the equilibration sample. Alternatively, the exhaust port 32 can be sealed after the gas intake is stopped to prevent any contamination of the equilibration sample by the air inside the chamber.

[0067] Specifically, the multi-parameter collaborative calibration includes one or more of the following items:

[0068] ①Cumulative duration of electrode temperature exceeding limit:

[0069] Set the electrode temperature of the percutaneous blood gas monitor (e.g., 43℃). Once the electrode temperature reaches the set value (usually within 1 minute), collect the electrode temperature at 0.1-second intervals using temperature probe 5. Within the observation window (e.g., 30 minutes) after the electrode temperature reaches the set value, calculate the cumulative time for the measured temperature to exceed the set temperature threshold (e.g., 0.6℃), i.e., the cumulative time for the electrode temperature to exceed the limit. The specific calculation is as follows:

[0070] (2),

[0071] In the formula, The cumulative duration (s) of electrode temperature exceeding the limit. The electrode temperature setting (°C) for the transcutaneous blood gas monitor. The electrode temperature (°C) measured by temperature probe 5 at the kth sampling point. 1800 represents the observation start time (s) and 1800 represents the observation window duration (s). The function is an indicator function: when the condition in parentheses is true, the function takes the value of 1; when the condition is false, the function takes the value of 0; 0.6 is the electrode temperature overshoot threshold (°C).

[0072] According to formula (2), the calculation is achieved through discrete sampling as follows:

[0073] (3),

[0074] In the formula, The sampling interval for the temperature recorder. ; The total number of sampling points is N = 1800 / 0.1 = 18000.

[0075] Transcutaneous blood gas monitoring relies on heated electrodes to arterialize skin capillaries, making temperature control a primary safety indicator. Abnormal electrode temperature can directly cause skin burns, with premature infants, low-birth-weight infants, and patients in shock with low perfusion having even lower skin tolerance. However, during continuous electrode heating, measuring the instantaneous temperature overshoot peak is insufficient to reflect the risk of burns. Furthermore, extensive testing has revealed that due to the heat dissipation of the electrode contact surface, the actual measured instantaneous temperature fluctuates significantly and changes rapidly, making it difficult to accurately capture the momentary changes in electrode temperature. Therefore, this invention abandons the simple "temperature overshoot" indicator and adopts the "cumulative duration of electrode temperature exceeding the limit" indicator, statistically counting the total number of seconds the temperature exceeds the limited threshold within the observation window. This measurement is more accurate and better reflects clinical safety risks.

[0076] To accurately measure electrode temperature, the temperature probe 5 preferably uses a thermocouple with a more sensitive response and a wider range of operation instead of a digital thermometer for temperature measurement.

[0077] ②Indication error and repeatability:

[0078] Set the electrode temperature of the transcutaneous blood gas analyzer (e.g., 43℃) and the temperature of the equilibrium chamber 3 (e.g., 37℃). After the temperature reaches the set value, introduce a standard gas mixture into the equilibrium chamber 3 and control the gas flow rate to be 10mL / min to 20mL / min. After the transcutaneous blood gas analyzer reading stabilizes and remains stable for at least 10 minutes, continuously collect and record the transcutaneous blood gas analyzer reading n times. Calculate the absolute error of the reading according to formula (4) or the relative error of the reading according to formula (5) as a representation of the reading error; calculate the relative standard deviation according to formula (6) as a representation of repeatability.

[0079] (4),

[0080] (5),

[0081] (6),

[0082] In the formula, The absolute error of the indicated value (mmHg) The relative error of the indicated value (%) The average value (mmHg) of n measurements taken by the transcutaneous blood gas monitor. The standard value of gas partial pressure (mmHg) in equilibrium chamber 3. The value represents the relative standard deviation (%). The value (mmHg) is the i-th measurement from the transcutaneous blood gas monitor, and n is the number of measurements, such as n=6.

[0083] The transcutaneous blood gas monitor readings include transcutaneous oxygen partial pressure and transcutaneous carbon dioxide partial pressure. The calculation method for the standard values ​​of gas partial pressures in equilibrium chamber 3 is as follows:

[0084] tcpCO2= FCO2(pTotal –RH / 100 × pH2O) (7),

[0085] tcpO2 = FO2(pTotal –RH / 100 × pH2O) (8),

[0086] pH2O = 10 (0.0244T + 0.7655) + 0.4 (9),

[0087] Where tcpCO2 and tcpO2 represent the standard values ​​of transdermal carbon dioxide partial pressure and transdermal oxygen partial pressure, respectively, that is, the standard values ​​of CO2 and O2 partial pressure in the equilibrium gas (mmHg), FCO2 and FO2 are the concentrations (mole fractions) of CO2 and O2 in the standard gas, respectively, pTotal is the atmospheric pressure in the environment (mmHg), RH is the actual relative humidity of the mixed gas after equilibrium, pH2O is the water vapor pressure (mmHg) at the equilibrium temperature, which can be calculated by formula (9), T represents the equilibrium temperature (°C), and pH2O is calculated to be about 47 mmHg at 37°C.

[0088] Furthermore, considering the effect of electrode heating, the calculated standard value of partial pressure (i.e., the transdermal gas partial pressure at 37°C) can be adjusted using the following formula, where T... s The set electrode temperature (°C):

[0089] tcpCO2(T s = tcpCO2(37℃) ×10 –0.019(Ts –37) (10)

[0090] tcpO2(T s = tcpO2(37℃) ×10 –0.019(Ts –37) (11).

[0091] ③ Linearity plus hysteresis:

[0092] Set the electrode temperature of the percutaneous blood gas monitor (e.g., 43℃) and the temperature of the equilibrium chamber 3 (e.g., 37℃). After the temperature reaches the set value, introduce a standard gas mixture into the equilibrium chamber 3. Select two sets of standard gas mixtures: the first set is a gas with high oxygen and low carbon dioxide concentration, and the second set is a gas with low oxygen and high carbon dioxide concentration.

[0093] Introduce the first set of standard gases into the equilibrium chamber 3, controlling the gas flow rate to 10 mL / min to 20 mL / min; after the transcutaneous blood gas monitor reading stabilizes and remains stable for at least 10 min, continuously collect and record the transcutaneous blood gas monitor reading 3 times. Switch to the second set of standard gases, keeping the gas flow rate constant; after the transcutaneous blood gas monitor reading stabilizes and remains stable for at least 10 min, continuously collect and record the transcutaneous blood gas monitor reading 3 times. Switch back to the first set of standard gases, maintaining the same gas flow rate; after the transcutaneous blood gas monitor reading stabilizes and remains stable for at least 10 min, continuously collect and record the transcutaneous blood gas monitor reading 3 times. Calculate the transcutaneous partial pressure linearity plus hysteresis according to formula (12):

[0094] (12)

[0095] In the formula, Add hysteresis (mmHg) to linearity; The average value (mmHg) of three transcutaneous blood gas monitor readings for the first time the first group of gases was introduced. The value is the average of three readings (mmHg) from the transcutaneous blood gas monitor in Group 2. The average value (mmHg) of three transcutaneous blood gas monitor readings after the first group of gases was introduced again. The concentration (%) of the components in the first group of standard gas mixtures; The concentration (%) of the components in the second group of standard gas mixtures.

[0096] In theory, gas partial pressure is linearly related to gas concentration. That is, no matter how many times the same concentration of standard gas is introduced, the measured gas partial pressure should be consistent. However, due to the hysteresis characteristic of the transcutaneous blood gas monitor, the actual measured gas partial pressure values ​​are not consistent. Therefore, it is necessary to test and calibrate this hysteresis characteristic to ensure that the instrument measurement error does not exceed the set range.

[0097] For formula (12), the linearity of the transcutaneous oxygen partial pressure plus hysteresis is calculated by substituting the oxygen concentration data; the linearity of the transcutaneous carbon dioxide partial pressure plus hysteresis is calculated by substituting the carbon dioxide concentration data; when calculating the linearity plus hysteresis corresponding to the second group of gases, the expression on the upper right side of formula (12) is used; when calculating the linearity plus hysteresis corresponding to the first group of gases for the return test, the expression on the lower right side of formula (12) is used.

[0098] The multi-parameter collaborative calibration is not limited to the above-mentioned indicators. In other embodiments, other indicators (such as temperature overshoot and temperature fluctuation value) can also be used to evaluate and calibrate the temperature performance and partial pressure detection performance of the transcutaneous blood gas monitor.

[0099] This invention abandons the traditional pure gas phase calibration mode. It completely replicates the clinical subcutaneous fluid-gas diffusion scenario through a human body equivalent cavity, pre-saturated humidification, and full-area constant temperature water circulation. It simultaneously eliminates system interference caused by fluctuations in gas pressure, water vapor pressure, and temperature. It can simultaneously complete the coordinated calibration of multiple parameters such as TCPO2, TCPCO2, and electrode temperature, which greatly improves calibration accuracy and detection efficiency. It is compatible with different models of transcutaneous blood gas monitors and solves the problem of the inability to effectively trace the TCPO2 and TCPCO2 values ​​of transcutaneous blood gas monitors. It effectively fills the gap in the field of transcutaneous blood gas monitor calibration technology.

[0100] The above-described specific embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Various modifications, substitutions, and improvements made by those skilled in the art to the technical solutions of the present invention based on the provided textual description and drawings, without departing from the design concept and spirit of the present invention, should all fall within the scope of protection of the present invention.

Claims

1. A calibration device for a transcutaneous blood gas monitor, characterized in that, include: A gas-liquid balance module includes a balance chamber containing a balance solution, an exhaust port connected to the atmospheric environment on the balance chamber, and an electrode interface covered with a waterproof and breathable membrane at the bottom of the balance chamber for electrode installation of a transcutaneous blood gas monitor. The standard gas module, which is connected to the equilibrium chamber, is used to deliver standard gases with set oxygen and carbon dioxide concentrations into the equilibrium solution. Thermostatic control module is used to control the temperature of the equilibrium chamber; The measurement module includes a temperature probe located at the electrode interface and a pressure sensor located in the atmospheric environment.

2. The transcutaneous blood gas monitoring calibration device according to claim 1, characterized in that, The equilibrium solution is venous blood or a buffer solution, and the standard gas is a standard substance of nitrogen, carbon dioxide and oxygen or a standard gas mixture generated by a precision gas mixing system.

3. The transcutaneous blood gas monitoring calibration device according to claim 1, characterized in that, The exhaust ports are located at the top of the balance chamber, and the bottom side of the balance chamber is provided with an air inlet for connecting to the standard gas module. Both the exhaust ports and the air inlets are provided with waterproof and breathable membranes.

4. The transcutaneous blood gas monitoring calibration device according to claim 1, characterized in that, The constant temperature control module includes a liquid circulation channel filled with circulating fluid, an electric heater, a temperature sensor, and a liquid circulation pump. The liquid circulation channel is distributed around or spirally distributed within the equilibrium chamber. The electric heater is used to heat the circulating fluid in the liquid circulation channel, the temperature sensor is used to monitor the temperature of the circulating fluid in the liquid circulation channel, and the liquid circulation pump is used to realize the circulation flow of the circulating fluid in the liquid circulation channel.

5. The transcutaneous blood gas monitoring calibration device according to claim 1, characterized in that, It also includes a humidity control module, which connects the standard gas module to the equilibrium chamber to control the humidity of the standard gas.

6. The transcutaneous blood gas monitoring calibration device according to claim 5, characterized in that, The humidity control module includes a humidification chamber filled with pure water. The standard gas generated by the standard gas module flows through the humidification chamber and is saturated with water vapor by water bubbling before entering the balance chamber.

7. The transcutaneous blood gas monitoring calibration device according to claim 1, characterized in that, The measurement module also includes a humidity sensor for collecting and balancing the relative humidity of indoor gases.

8. The transcutaneous blood gas monitoring calibration device according to claim 1, characterized in that, The balance chamber is also equipped with a hollow fiber layer made of waterproof and breathable material.

9. A calibration method based on the transcutaneous blood gas monitor calibration device according to claim 1, characterized in that, Includes the following steps: The set amount of equilibration solution is filled into the equilibration chamber, and the electrodes of the transcutaneous blood gas monitor are installed at the electrode interface. Temperature control of the equilibrium chamber is achieved through a constant temperature control module; The standard gas module delivers standard gases with set oxygen and carbon dioxide concentrations into the equilibrium solution to achieve gas partial pressure balance between the liquid and the gas. After gas-liquid balance is achieved, data is collected through the measurement module, thereby realizing multi-parameter collaborative calibration of the transcutaneous blood gas monitor.

10. The calibration method according to claim 9, characterized in that, The multi-parameter collaborative calibration includes one or more of the following items: ①Cumulative duration of electrode temperature exceeding limit: Set the electrode temperature of the percutaneous blood gas monitor. After the electrode temperature reaches the set value, collect the electrode temperature at set time intervals through the temperature probe. Within the observation window from when the electrode temperature reaches the set value, count the cumulative time for the measured temperature to exceed the set temperature and reach the limit threshold. This is the cumulative time for the electrode temperature to exceed the limit. ②Indication error and repeatability: The electrode temperature and equilibrium chamber temperature of the transcutaneous blood gas monitor are set. After the temperature reaches the set value, standard gases with set oxygen and carbon dioxide concentrations are introduced into the equilibrium chamber. After the transcutaneous blood gas monitor readings stabilize and remain stable for no less than the set time, the transcutaneous blood gas monitor readings are continuously collected and recorded n times. Then, the absolute error or relative error of the readings is calculated based on the average value of the n measurements and the standard value of the gas partial pressure in the equilibrium chamber as a characterization of the reading error. The relative standard deviation is also calculated as a characterization of repeatability. The standard value of the gas partial pressure in the equilibrium chamber is calculated based on the atmospheric pressure measured by the barometer and the oxygen and carbon dioxide concentrations in the standard gas. ③ Linearity plus hysteresis: Set the electrode temperature and equilibrium chamber temperature of the transcutaneous blood gas analyzer. After the temperature reaches the set value, introduce the first set of standard gases into the equilibrium chamber. After the transcutaneous blood gas analyzer reading stabilizes and remains stable for at least the set time, continuously collect and record the transcutaneous blood gas analyzer readings m times. Switch to introducing the second set of standard gases. After the transcutaneous blood gas analyzer reading stabilizes and remains stable for at least the set time, continuously collect and record the transcutaneous blood gas analyzer readings m times. Switch back to introducing the first set of standard gases. After the transcutaneous blood gas analyzer reading stabilizes and remains stable for at least the set time, continuously collect and record the transcutaneous blood gas analyzer readings m times. Calculate the linearity plus hysteresis based on the average value of the transcutaneous blood gas analyzer readings during the first introduction of the first set of standard gases, the average value of the transcutaneous blood gas analyzer readings during the second introduction of the second set of standard gases, and the average value of the transcutaneous blood gas analyzer readings during the second introduction of the first set of standard gases.

Images