Determination of gas exchange device performance

Abstract

A method for determining a performance of a gas exchange device (110) is disclosed. Based on a carbon dioxide concentration and a flow rate of an exhaust gas, a flow rate of carbon dioxide transferred to a gas flow through the gas exchange device is determined g Based on the flow rate of carbon dioxide transferred to the gas flow and a reference flow rate, the performance of the gas exchange device is determined, wherein the reference flow rate is based on a model describing the flow rate of carbon dioxide transferred to the gas flow as a function of at least one of: a blood flow rate through the gas exchange device, a flow rate of the gas flow, a carbon dioxide concentration in an inlet gas, a carbon dioxide partial pressure in the blood before gas exchange, a hemoglobin concentration in the blood, a pH value of the blood.

Description

Technical Field

[0001] This invention relates to methods and systems for performing gas exchange in a patient's circulatory system using a gas exchange device. More particularly, this disclosure relates to techniques for determining the performance of such a gas exchange device. Background Technology

[0002] Gas exchange in the blood is a physical process in which gases move across membranes (such as the blood-air barrier in the alveoli of a mammalian lung) to allow oxygen to be absorbed by the blood and to release carbon dioxide from the blood.

[0003] In cases of respiratory failure or bypass, external gas exchange devices can be used to support or replace a patient's lung function. Gas exchange devices typically use purge gas to oxygenate the blood and allow carbon dioxide to be released from the blood.

[0004] The performance of gas exchange devices is crucial for patient safety and effective medical care. Insufficient oxygen uptake or carbon dioxide release can rapidly lead to dangerous conditions that jeopardize patient health and safety. A commonly monitored parameter is blood oxygen uptake, which can be estimated as the difference between the oxygen content of the incoming purge gas and the oxygen content of the outgoing exhaust gas (i.e., the oxygen flow rate before and after gas exchange). However, measuring oxygen content, especially at the relatively high concentrations typically used for purge gases, can be technically challenging and requires oxygen sensors capable of discerning minute changes in oxygen levels to accurately assess gas exchange efficiency.

[0005] Therefore, there is a need for improved and alternative technologies for monitoring and determining the performance of gas exchange devices. Summary of the Invention

[0006] In view of this, this disclosure provides an improved or alternative technique having the features set forth in the independent claims.

[0007] Therefore, according to a first aspect, a method is provided for determining the performance of a gas exchange device coupled to a patient's circulatory system to transfer one or more blood gases between blood in the circulatory system and an airflow passing through the gas exchange device, the airflow entering the gas exchange device as an inlet gas and exiting the gas exchange device as an outlet gas. The method includes determining the flow rate of carbon dioxide (CO2) transferred to the airflow based on the CO2 concentration in the outlet gas, the flow rate of CO2 in the inlet gas, and the flow rate of the outlet gas. The performance of the gas exchange device can be determined based on the CO2 flow rate transferred to the airflow and a reference flow rate. The reference flow rate is based on a model that describes the CO2 flow rate transferred to the airflow as a function of at least one of the following: the blood flow rate through the gas exchange device, the airflow flow rate through the gas exchange device, the CO2 concentration in the inlet gas, the partial pressure of CO2 in the blood before gas exchange, the hemoglobin concentration in the blood, and the pH value of the blood. The pH value of the blood can refer to the pH value of the blood before gas exchange or the pH value of the blood after gas exchange.

[0008] According to a second aspect, a system is provided, comprising: a gas exchange device for transferring blood gases between blood in a patient's circulatory system and an airflow passing through the gas exchange device, wherein the airflow enters the gas exchange device as an inlet gas and exits the gas exchange device as an outlet gas; and a CO2 sensor configured to generate sensor data indicating the CO2 concentration in the outlet gas. A control unit is provided to determine the CO2 flow rate transferred to the airflow based on the CO2 concentration in the outlet gas, the CO2 flow rate in the inlet gas, and the flow rate of the outlet gas, and to determine the performance of the gas exchange device based on the CO2 flow rate transferred to the airflow and a reference flow rate. The reference flow rate is based on a model that describes the CO2 flow rate transferred to the airflow as a function of at least one of the following: the blood flow rate through the gas exchange device, the airflow flow rate through the gas exchange device, the CO2 concentration in the inlet gas, the partial pressure of CO2 in the blood before gas exchange, the hemoglobin concentration in the blood, and the pH value of the blood.

[0009] According to a third aspect, a system is provided, including a gas exchange device for transferring blood gases between blood in a patient's circulatory system and a gas flow passing through the gas exchange device, wherein the gas flow enters the gas exchange device as an inlet gas and exits the gas exchange device as an outlet gas. The system further includes a gas supply module configured to generate a first signal indicating the CO2 flow rate in the inlet gas (if any); and an exhaust module configured to generate a second signal indicating the CO2 flow rate in the exhaust gas. A control unit is provided to receive and process the first and second signals to determine the CO2 flow rate transferred to the gas flow based on the difference between the CO2 flow rate in the exhaust gas and the CO2 flow rate in the inlet gas. The CO2 flow rate transferred to the gas flow can be used in conjunction with a reference flow rate to determine the performance of the gas exchange device. The reference flow rate can be based on at least one of the following: blood flow rate through the gas exchange device, gas flow rate through the gas exchange device, CO2 concentration in the inlet gas, CO2 partial pressure in the blood before gas exchange, hemoglobin concentration in the blood, and pH value of the blood.

[0010] In the above aspects, the CO2 flow rate transferred to the gas flow is compared with a reference flow rate that can be derived from the model to obtain information about the performance of the gas exchanger. The reference flow rate can, for example, describe an ideal situation, such as the expected CO2 flow rate transferred assuming the gas exchanger is in its original, undamaged state. Therefore, the reference flow rate can effectively reflect the performance of a new or unused gas exchanger operating at 100% capacity. The efficiency of the device can be assessed by comparing the actual CO2 flow rate from the gas exchanger with the flow rate at 100% capacity. The flow rate at 100% capacity can be determined based on one or more of the parameters mentioned above, such as the blood flow rate and / or gas flow rate through the gas exchanger. Changes in device efficiency, such as the degree to which device efficiency decreases or recovers over time, can be quantitatively determined by comparing the actual CO2 flow rate with a baseline corresponding to the performance of a new gas exchanger. Efficiency typically reflects the gas transfer capacity of a membrane, which tends to decrease over time due to blood clot buildup, increased diffusion resistance deposition, and condensation of water vapor inside the membrane, which can clog the fibers. Temporary recovery can be observed if blood clots dissolve or condensate is removed.

[0011] Comparing the actual CO2 flow rate transferred to the gas stream with the expected CO2 flow rate not only highlights the degradation or recovery of the device's functional capacity but also helps assess its current operational adequacy relative to the device's initial performance standards. Furthermore, trends in the gas exchange rate between the blood and gas streams can be monitored and evaluated. If the monitored parameters fall outside acceptable limits, it indicates the need for replacement or operator intervention.

[0012] Reference flow rates can be obtained in various ways, typically as a function of one or more parameters or variables describing the operating conditions of the gas exchanger. This can be referred to as a model or mathematical model and can be designed in various ways. The set of parameters can be combined with a set of constants or weights specific to the gas exchanger model design used. As mentioned above, variables can include one or more of the following: blood flow rate through the gas exchanger, gas flow rate through the gas exchanger, CO2 concentration in the inlet gas, CO2 partial pressure in the blood before gas exchange, hemoglobin concentration in the blood, and pH value of the blood. When determining the reference flow rate for CO2, one or more of these variables can be provided as input to the model to reflect the specific operating conditions of the gas exchanger.

[0013] The constants can be determined based on experimental data, preferably data relating to gas exchange devices of the same or similar design. For example, the constants can relate to the permeability of the membrane separating blood from the purge gas, indicating how easily gases such as CO2 and O2 pass through the membrane. These constants can also relate to the effective area of ​​the membrane where gas exchange occurs, and the flow distribution of blood through the device. In other examples, the constants can relate to operating parameters that affect the efficiency of gas exchange, such as the heating of the membrane or the purge gas.

[0014] Therefore, a reference CO2 flow rate can be calculated based on the type of gas exchange device and one or more operating parameters of the gas exchange device, wherein the type of gas exchange device determines which model (or constant) to use, and the operating parameters(s) serve as inputs to the model. In some examples, the reference CO2 flow rate is determined based on a combination of at least two parameters, such as the blood flow rate through the gas exchange device (also referred to as “blood flow”) and the gas flow rate supplied to the gas exchange device (also referred to as “purge gas flow”). Alternatively, or additionally, the reference CO2 flow rate can be determined based on the blood flow and CO2 partial pressure of the blood before gas exchange, and / or the blood flow rate and the hemoglobin concentration in the blood. Further combinations of models and specific examples are discussed in the detailed description of the accompanying drawings.

[0015] It should be understood that the model describing the relationship between the reference flow rate and parameters (such as blood flow rate through the gas exchanger, gas flow rate through the gas exchanger, CO2 concentration in the inlet gas, CO2 partial pressure in the blood before gas exchange, hemoglobin concentration in the blood, and pH value of the blood, or one or more of these) can include or be implemented as a data structure, such as a lookup table, dataset, or other reference value library. In this case, one or more of the aforementioned parameters can be used as keywords or indexes to retrieve the corresponding reference flow rate from the data structure. Therefore, in some examples, the reference flow rate can be obtained through data retrieval rather than calculation.

[0016] In one example, the reference flow rate is determined based on the blood flow rate passing through the gas exchange device. In another example, the reference flow rate is determined based on a combination of the gas flow rate or blood flow rate and the airflow passing through the gas exchange device.

[0017] The exhaust module may include a CO2 sensor for generating sensor data indicating the CO2 concentration in the exhaust gas. This concentration can be used, along with the total flow rate of the exhaust gas, to determine the CO2 flow rate in the exhaust gas. The exhaust module may be configured to determine the total flow rate of the exhaust gas using direct or indirect measurements, as will be outlined below.

[0018] Determining the total flow rate of the exhaust gas can be challenging. Performing direct flow measurement at the outlet of a gas exchanger carries the risk of missing leaks, such as gas escaping through emergency outlets commonly found in many gas exchangers. Furthermore, the outflow is prone to becoming saturated with water vapor, which can condense and limit the accuracy of flow measurement. Therefore, in some examples, a method based on oxygen mass balance has been proposed to determine the flow rate, where it is assumed that the amount of oxygen leaving the gas exchanger corresponds to the difference between the amount of oxygen supplied to the gas exchanger and the amount of oxygen absorbed by the blood during the gas exchange. The amount of oxygen absorbed by the blood can be determined by comparing the oxygen content in the blood after the gas exchange with the oxygen content in the blood before the gas exchange, based on blood sensor data. The amount of oxygen remaining in the gas flow after the gas exchange can be determined by subtracting the amount of oxygen absorbed by the blood from the amount of oxygen supplied to the gas exchanger. By combining the oxygen content in the exhaust gas with the oxygen concentration in the exhaust gas, the total flow rate of the exhaust gas can be determined without directly measuring the flow rate using, for example, a flow meter.

[0019] Therefore, determining the CO2 flow rate in the exhaust gas, as an example, may include: The oxygen uptake of the blood is determined based on blood flow rate and the difference between the oxygen concentration in the blood leaving the gas exchange device and the oxygen concentration in the blood entering the gas exchange device. The oxygen flow rate in the exhaust gas is determined based on the difference between the oxygen flow rate in the inlet gas and the oxygen uptake in the blood. The flow rate of the exhaust gas is determined based on the oxygen flow rate and oxygen concentration in the exhaust gas.

[0020] However, it should be noted that alternative methods exist for determining the exhaust gas flow rate. In some examples, a flow sensor can be used to measure the flow rate, either placed at the gas outlet, integrated into the gas exchanger, or positioned further away from the gas exchanger and connected to it via a pipe. In some examples, the flow rate can be measured by determining the inlet gas flow rate and adjusting the humidity intake in the gas exchanger. These methods may be useful for verifying the flow rate obtained through the balancing method, thus serving as a valid integrity check.

[0021] Typically, the CO2 flow rate from a gas exchanger is determined by measuring the CO2 concentration in the exhaust gas and multiplying it by the total exhaust gas flow rate. This method can be called exhaust gas measurement. However, an alternative or supplementary method involves blood gas measurement. This method determines the CO2 flow rate by comparing the CO2 content in the blood before and after gas exchange. Specifically, this method involves calculating the difference between the CO2 content in the blood entering and leaving the gas exchanger, and then multiplying that difference by the blood flow rate. Blood gas measurement can be used as a standalone method or to supplement exhaust gas measurement results to verify their accuracy, and can be performed intermittently or continuously.

[0022] Therefore, in some cases, the CO2 flow rate released from or transferred into the gas stream based on blood gas measurements (i.e., "blood gas-based flow rate") can be compared with the CO2 flow rate transferred into the gas stream based on exhaust gas measurements (i.e., "gas flow-based flow rate") as a "completeness check" of the accuracy of the exhaust gas measurements. While exhaust gas measurements are generally considered more accurate than blood gas measurements, a significant discrepancy between the two methods may indicate a problem. The blood gas-based CO2 flow rate and the gas flow-based CO2 flow rate can be compared, for example, by examining the difference or quotient between them. If this difference or quotient exceeds a predetermined threshold, an error condition can be identified. This error condition can trigger alarms, warnings, or error signals, potentially requiring operator intervention.

[0023] It should be understood that CO2 can be transported in the blood in three main forms: dissolved CO2, bicarbonate (…), and… CO2 consists of carbamate compounds. Typically, about 30% of all CO2 is transported as carbamate compounds, and 60% is produced by red blood cells. Ion transport, approximately 10% of which is dissolved in plasma, occurs during blood-gas exchange in the lungs. Ions play an important role. When blood reaches the lungs, Ions are converted into CO2, which can be exhaled from the body through respiration. In the context of this disclosure, the term "CO2 concentration" generally refers to the total concentration of CO2 present in the blood, i.e., all three of the aforementioned main forms, while the term "partial pressure of CO2" generally refers to the concentration of dissolved CO2. Partial pressure of CO2 is often used in clinical practice to assess gas exchange efficiency.

[0024] In the above example, some parameters used to determine the CO2 flow rate transferred to the gas stream can be predetermined or known based on system settings, while other parameters can be retrieved from sensor data. The blood flow through the gas exchanger can be measured using an ultrasonic flow sensor or based on known parameters determined by system settings, such as the pumping rate of the pump used to circulate blood through the system. Furthermore, the oxygen concentration in the inlet gas and the total flow rate of the inlet gas can be determined based on the inlet gas supply settings, such as the gas mixer used to supply the required purge gas to the gas exchanger.

[0025] In some examples, the gas supply module is configured to provide information about the CO2 flow rate in the inlet gas. The gas supply module may, for example, include a gas agitator or mixer capable of operating to deliver a specific concentration of oxygen and / or CO2 at a specific flow rate. Therefore, the concentration and flow rate of oxygen and / or CO2 may be known or predetermined based on the operating settings of the gas supply module and used as inputs to the control unit when determining the performance of the gas exchange device, as described above. In other examples, the gas supply module includes one or more sensors, such as a flow sensor, an oxygen concentration sensor, or a CO2 concentration sensor, for generating information that can be used to determine the CO2 flow rate in the inlet gas.

[0026] However, the oxygen and / or CO2 content in the blood after and before gas exchange, as well as the oxygen and / or CO2 concentration in the exhaust gas, can also be obtained from sensor data. Therefore, it should be understood that, depending on the specific configuration of the system, various sensors can be configured to measure oxygen and / or CO2 content, such as partial pressure. In some configurations, one or more of these sensors can be directly integrated into the gas exchange unit, while in others, they can be designed as separate components connected to the gas exchange unit. Each of these sensors can be communicatively linked to the control unit to transmit sensor signals for processing. The control unit can use these signals to perform the discussed calculations and determinations and input the data into a model used to predict reference CO2 flow rates.

[0027] In the context of this disclosure, the terms "flow" or "flow rate" generally refer to how gas or blood passes through a system. Flow rate can refer to the total flow rate of gas supplied to or discharged from a gas exchanger, or the flow rate of a specific component of a gas such as O2 or CO2. Flow rate is generally understood as a term describing the amount of fluid moving through a given cross-sectional area per unit time and can be measured in terms of volume or mass. The former can be called volumetric flow rate and describes how much volume of fluid passes through a given area in a given time period. In SI systems, volumetric flow rate is typically expressed in cubic meters per second (m³ / s). 3 Volumetric flow rate is expressed as liters per minute (L / min). However, in the context of this disclosure, flow rate is typically expressed as liters per minute (L / min). Therefore, volumetric flow rate generally describes how many liters of fluid (such as oxygen or blood) are supplied to (or discharged from) a gas exchanger per minute. Alternatively, flow rate can be measured as mass flow rate, which describes the mass of fluid (such as oxygen or blood) passing through a given area in a specific time period. Therefore, mass flow rate can be expressed as kilograms per second (kg / s). Mass flow rate can be particularly useful when gas density may change under varying conditions, as it provides a measurement independent of temperature and pressure. It should be understood that volumetric flow rate is proportional to mass flow rate, and therefore volumetric flow rate can be converted to mass flow rate at a given gas temperature and pressure (and vice versa).

[0028] Standard cubic centimeters per minute (SCCM) is an example of a unit that can be used to quantify fluid flow rate and can be understood as the mass flow rate of one cubic centimeter per minute of a gas with a defined density under certain temperature and pressure standard conditions. Standard conditions may vary from regulatory authority to regulatory authority, but in one example, standard conditions may correspond to a temperature of 0°C and a pressure of 1.013 bar.

[0029] Furthermore, in discussing the oxygen content in blood, it should be noted that the oxygen content in blood usually refers to the total concentration of oxygen carried in the bloodstream. Oxygen typically exists in blood in two main forms: bound to hemoglobin and dissolved directly in plasma. It should be understood that other forms may also exist, but these two forms tend to account for the majority of the oxygen content. Generally, most of the oxygen transported in the blood is bound to hemoglobin (often referred to as "saturation"), while a small portion of the oxygen in the blood is dissolved in plasma (often referred to as "partial pressure"). Therefore, oxygen concentration usually refers to the total concentration of oxygen described by oxygen saturation, hemoglobin concentration, oxygen partial pressure, and constants. Oxygen concentration can be expressed as the volume of oxygen per unit volume of blood (such as milliliters of oxygen per deciliter of blood) or the mass of oxygen per unit volume of blood (such as millimoles of oxygen per deciliter of blood).

[0030] The oxygen concentration or partial pressure in the inlet and outlet gases is typically measured as a percentage of the total gas mixture. For example, medical oxygen supplied to a gas exchange device may have a concentration ranging from approximately 21% (corresponding to the concentration in air) to 100%, depending on clinical needs. Percentages are usually described as volume ratios, such as liters of oxygen per liter of total gas. However, in some examples, concentration may also be expressed as a mole fraction (the number of moles of oxygen per mole of the gas mixture) or the amount of substance oxygen per unit volume of the gas mixture.

[0031] Pre-exchange blood typically refers to blood that has already circulated through the body and delivered oxygen to the tissues. Therefore, this blood may have a higher carbon dioxide concentration. Pre-exchange blood can also be called pre-oxygenated blood, deoxygenated blood, or venous blood. Anoxic blood can be supplied to gas exchange devices for oxygen enrichment and / or carbon dioxide removal.

[0032] Post-gas exchange blood, also known as oxygenated blood, oxygenated blood, or arterial blood, can be understood as blood that has undergone gas exchange in a gas exchange device, where oxygen can be supplied to the blood and / or carbon dioxide can be removed from the blood. Oxygenated blood can be returned to the patient to supply oxygen to the tissues.

[0033] As mentioned above, the oxygen content in blood can refer to the total concentration of oxygen carried by the bloodstream, described by saturation, hemoglobin concentration, oxygen partial pressure, and a constant. Therefore, sensor data can indicate both the saturation and the oxygen partial pressure in oxygen-rich and oxygen-deficient blood. By taking into account saturation, hemoglobin concentration, and partial pressure, the total concentration or amount of oxygen absorbed by the blood during gas exchange can be determined with relatively high accuracy.

[0034] Alternatively, or additionally, for anoxic or incompletely oxygen-saturated blood, its saturation can be determined based on the partial pressure of oxygen. This is based on the established relationship between the partial pressure of oxygen and saturation. Therefore, by measuring the partial pressure of oxygen in anoxic blood, this relationship can be used to estimate oxygen saturation without directly measuring the oxygen saturation level. However, it should be noted that the relationship between saturation and partial pressure of oxygen can be affected by other parameters, such as pH, partial pressure of carbon dioxide, and 2,3-DPG levels. These parameters can be considered to further refine the estimation of saturation.

[0035] Other features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only with reference to the accompanying drawings. Attached Figure Description

[0036] The above and other objects, features, and advantages of this disclosure will be better understood through the following exemplary and non-limiting detailed description, with reference to the accompanying drawings. The same reference numerals will be used for similar elements.

[0037] Figure 1 A system according to an example is shown, including a gas exchange device coupled to an external circuit.

[0038] Figure 2 The figure illustrates a system based on an example, showing various sensors used to retrieve observation data from the system.

[0039] Figure 3 This is a flowchart of an example of a method for determining the performance of a gas exchange device.

[0040] Figure 4 This is a flowchart of another example of this method, in which the total flow rate of the exhaust gas is determined.

[0041] As shown in the figure, for illustrative purposes, the dimensions of the components and features may be exaggerated; therefore, the dimensions of these components and areas are provided to illustrate the general structure of the example. Detailed Implementation

[0042] Figure 1 A system 100 for exchanging blood with one or more gases within the circulatory system of a patient 10 is illustrated by way of example. The system 100 includes a gas exchange device 110 for transferring blood gases between blood and a gas flow, wherein blood circulates in an external circuit 105, and the gas flow enters the gas exchange device 110 as an inlet gas via an inlet 112 and exits the gas exchange device 110 as an outlet gas via an outlet 114. The gas flow supplied to the gas exchange device 110 may also be referred to as a purge gas.

[0043] Examples of system 100 according to this disclosure include a cardiopulmonary bypass machine (cardiopulmonary bypass machine) that provides circulatory and respiratory support in the operating room when the heart stops for surgery. Other examples include extracorporeal membrane oxygenation (ECMO) devices that provide circulatory and respiratory support in the intensive care unit, and extracorporeal CO2 removal (ECCO2R) devices that remove excess carbon dioxide from the blood.

[0044] The gas exchange device 110 is configured to facilitate gas exchange between the patient's blood and the gas stream passing through it. The gas exchange device 110 is generally configured to allow oxygen to enter the blood from the gas stream, thereby oxygenating the blood, and to allow CO2 to be released from the blood and enter the gas stream. It should be understood that other types of gases and substances can also be exchanged in a similar manner, including anesthetics and nitric oxide.

[0045] The gas exchange device 110, which may also be referred to as an oxygenator in some examples, may include a gas zone 117 and a blood zone 118 separated by a permeable membrane 119. Blood in the external circuit 105 can be circulated through the blood zone 118 via the circulation unit 107, while the gas flow can pass through the gas zone 117 via a gas inlet 112 and a gas outlet 114. Due to the partial pressure gradient or concentration difference between the components of the gas flow and their corresponding components in the blood, a component can pass from the gas zone 117 through the membrane 119 into the blood zone 118, and vice versa. In particular, oxygen can pass from the gas zone 117 through the membrane 119 to the blood zone 118, thus oxygenating anoxic blood into oxygenated blood. Conversely, CO2 can pass from the blood zone 118 through the membrane 119 to the gas zone 117, thereby removing CO2 from the blood flow. This can be referred to as the CO2 flow rate transferred to the gas flow.

[0046] Several types of membranes 119 can also be used. In one example, the gas exchange device 110 includes a hollow fiber membrane, wherein blood flows in a blood zone 118 inside the fiber, and a gas mixture flows in a gas zone 117 outside the fiber. The exchange of oxygen and CO2 can occur through the membrane formed by the hollow fiber walls. However, in Figure 1 In the example shown, membrane 119 is schematically shown as a sheet.

[0047] Depending on the specific type of system 100, the circulation unit 107 may include, for example, a roller pump or a centrifugal pump. A roller pump typically includes a rotating roller that compresses a flexible tube or membrane. As the roller rotates, it squeezes the tube, creating a pulsating blood flow. A centrifugal pump, on the other hand, utilizes a rapidly rotating impeller to generate centrifugal force that pushes the blood outward to create a substantially continuous blood flow. Centrifugal pumps have been observed to reduce the risk of hemolysis (i.e., red blood cell breakdown) and improve patient comfort.

[0048] The oxygen or CO2 transfer capacity (i.e., the amount of oxygen supplied to the bloodstream or CO2 removed from the bloodstream per unit time) depends particularly on the blood flow rate, the gas flow rate, the gas flow composition, and the condition of the gas exchange device 110 itself. Specifically, the gas transfer capacity of the membrane 119 decreases over time due to blood clot buildup, increased diffusion resistance deposition, and water vapor condensation inside the membrane 119, which blocks the hollow fibers. Therefore, a gas exchange device 110 that cannot oxygenate the blood to a satisfactory level can be considered to be in a deteriorated or malfunctioning state.

[0049] The airflow can be provided by, for example, a gas supply module including a gas mixer 130. The gas mixer 130 typically includes multiple inlets 132, 134, which are configured to receive medical gases from respective gas sources (not shown). Figure 1In the example shown, the gas mixer 130 includes a first inlet 132 for a medical oxygen flow P1 and a second inlet 134 for a medical air flow P2. However, it should be understood that more inlets may be provided, and the gas mixer 130 may be used to supply other types of gases, such as carbon dioxide, nitric oxide, or anesthetics.

[0050] Medical oxygen can be supplied to the gas mixer 130 from an oxygen source, which can be an oxygen outlet of a central medical gas system in the hospital facility, a pressurized cylinder, or any other type of oxygen source suitable for delivering oxygen for medical applications. Similarly, air can be supplied from a pressurized air outlet of a central medical gas system in the hospital facility, a pressurized cylinder, or obtained from and pressurized ambient air.

[0051] The gases received at inlets 132 and 134 can be mixed into a purge gas mixture via a valve device (uniformly denoted by reference numeral 135) and supplied as inlet gas to gas inlet 112 of the gas exchange device 110. Valve device 135 can be configured to adjust the oxygen concentration and inlet gas flow rate according to patient needs, thereby allowing healthcare professionals to control the oxygen level delivered to the patient. Valve device 135 can be electronically controlled and, in some examples, configured to utilize sensor inputs to achieve accurate gas composition and flow rate.

[0052] Therefore, the gas mixer 130 can be operated to deliver oxygen of a specific concentration (100%) at a specific flow rate (such as 4 liters per minute). Thus, the concentration and flow rate of oxygen can be known or predetermined by the operation settings of the gas mixer 130 and are used as inputs in determining the performance of the gas exchange device 110, as discussed below.

[0053] exist Figure 1 In the example shown, an emergency outlet 116 is provided in the gas zone 117 of the gas exchanger 110. The emergency outlet 116 forms an additional outlet, i.e., an outlet other than the "main" outlet 114 discussed above, and is used to protect the gas exchanger 110 and the patient 10 from damage or injury due to overpressure in the event that the main outlet 114 is blocked or clogged. The emergency outlet 116 can be arranged to be normally open, thereby allowing exhaust gas to pass freely during operation of the gas exchanger 110. Therefore, the total flow of exhaust gas can be divided into two streams: a first stream through the gas outlet 114 and a second stream through the emergency outlet 116.

[0054] One or more sensors can be configured to generate sensor data that indicates, for example, characteristics of blood, such as the blood flow rate Q through the gas exchange device 110. bThe parameters include hemoglobin concentration (Hb), blood oxygen saturation, or blood pH, as well as blood gases such as CO2 and oxygen before and after gas exchange. Additionally, one or more sensors can be arranged to measure the characteristics of the airflow (i.e., inlet and / or outlet gas). One or more of these sensors can be implemented in the gas supply and / or exhaust modules as described above, configured to generate a signal indicating the CO2 flow rate in the exhaust gas. Examples of the measured airflow characteristics may include the airflow rate Q. s The sensors measure CO2 partial pressure and oxygen concentration, pressure, temperature, and humidity levels before and after gas exchange. Several examples of these sensors and the use of the data generated by them will be referenced below. Figures 2 to 4 Let's have a discussion.

[0055] Figure 2 System 100 is shown as an example, and its configuration method can be compared with... Figure 1 The system 100 is similar. Therefore, during the operation of the system 100, the anoxic blood in the external circuit 105 is supplied to the blood zone 118 of the gas exchange device 110, where the anoxic blood is oxygenated by the airflow through the gas zone 117 of the gas exchange device 110.

[0056] The efficiency of the gas exchange device 110 in oxidizing blood and removing CO2 is crucial to patient safety and the effectiveness of medical treatment. Insufficient oxygen intake or inadequate CO2 removal can rapidly lead to dangerous conditions, endangering the patient's health and safety.

[0057] Therefore, sensors can be configured to monitor various characteristics of the system. The sensor outputs can be relayed to control unit 140, which can be configured to analyze the data to evaluate the efficiency of the gas exchange device 110 in removing CO2 from the patient's blood. This efficiency or performance can be determined by calculating the CO2 flow rate transferred to the gas stream and comparing it to a reference flow rate obtained from a model. Figure 3 and Figure 4 Examples of this method are described in more detail.

[0058] Figure 2 The exemplary system 100 includes a CO2 sensor 121 and an oxygen sensor 124, respectively arranged to measure the CO2 concentration F in the exhaust gas leaving the gas exchange device 110 at the gas outlet 114. e CO2 and oxygen concentration F e O2 and CO2 sensors 121 and oxygen sensor 124 can be included, for example, in the exhaust module as described above. However, additional or alternative sensors, either separately or included in the gas supply module or exhaust module, can also be provided. System 100 may, for example, include a function to measure the purge gas flow rate Q at inlet 112 supplied to gas exchange device 110. sA flow sensor is used to measure the flow rate Q of the exhaust gas leaving the gas exchanger through outlet 114. e The flow sensor, and the oxygen concentration F of the purge gas supplied to the gas exchange unit 110. s O2 oxygen sensor.

[0059] System 100 also includes one or more sensors for measuring blood characteristics (such as blood gases and flow rate) circulating through gas exchange device 110. In this example, oxygen sensor 122 is arranged to measure the oxygen saturation S of the blood supplied to gas exchange device 110. v O2 and / or oxygen partial pressure p v O2 (Additionally, or alternatively, a sensor may be provided to measure the oxygen saturation S of the blood leaving the gas exchange device 110) a O2), CO2 sensor 125 is arranged to measure the partial pressure of carbon dioxide p in the blood supplied to the gas exchange device. v CO2, and flow sensor 127 is used to measure blood flow Q. b In other examples, sensors can be set up to measure the hemoglobin concentration (Hb) and / or pH of the blood supplied to the gas exchange device.

[0060] One or more sensors can also be configured to measure the characteristics of blood after gas exchange, such as one or more sensors 123, for measuring the oxygen saturation S of blood leaving the gas exchange device 110. a O2, oxygen partial pressure p a O2 or hemoglobin concentration Hb. One or more sensors 126 can also be set to measure the partial pressure of carbon dioxide p in the blood. a CO2. As mentioned above, depending on the configuration of system 100, other sensors, such as those for measuring blood flow Q, can also be used. b And a pH sensor.

[0061] It should be noted that, Figure 2 The system shown is merely one example of a possible implementation of the inventive concept, and various sensor configurations can be employed depending on the specific construction of system 100. Furthermore, two or more of the aforementioned sensor functions can be provided by a single sensor device, such as oxygen saturation S. a O2 / S v O2 and hemoglobin concentration (Hb).

[0062] Sensor data can be provided to control unit 140 to determine the performance of gas exchange device 110. Figure 3 The flowchart illustrates an example of this approach. To better understand the techniques disclosed herein, this example can be compared with... Figure 2Let's study it together. According to... Figure 3 CO2 flow rate V in the exhaust gas e CO2 can be based on the CO2 concentration F in the exhaust gas measured by CO2 sensor 121. e CO2 and exhaust gas flow rate Q e To determine. Indicates the exhaust gas flow rate V. e The CO2 signal can be generated by the exhaust module and transmitted to the control unit 140. When the inlet gas also includes CO2, the CO2 flow rate V in the exhaust gas stream can be determined. e CO2 and CO2 flow rate V in the inlet gas s The difference between CO2 is used to obtain the flow rate V transferred during gas exchange. g CO2. Then, the CO2 flow rate V can be... g CO2 and the reference flow V retrieved from the model describing the ideal situation ref The performance of the gas exchange device 110 is determined by comparing CO2 flow rates, with reference flow rates including the expected CO2 flow rate of the gas exchange device under similar operating conditions, defined by one or more parameters such as the blood flow rate Q assuming the gas exchange device is in its original, undamaged condition. b airflow rate Q s CO2 concentration F in the inlet gas s CO2, etc.

[0063] Therefore, according to Figure 3 In the example shown, one step of the method may be to determine (S110) the discharged gas F e The CO2 concentration in CO2. This information can be obtained, for example, from... Figure 2 The CO2 sensor 121 acquires the data. A further step may be to determine (S120) the flow rate Q of the exhaust gas. e And use this information to calculate (S130) the CO2 flow rate V in the exhaust gas. e CO2. Determine the flow rate Q of the exhaust gas. e There are many methods. (See reference) Figure 4 Let's discuss a possible example in more detail. Furthermore, the CO2 flow rate V transferred into the gas stream during gas exchange... g CO2 can be measured by the CO2 flow rate V in the exhaust gas. e CO2 minus the CO2 flow rate of the inlet gas V s CO2 is determined (S140) (see Equation 5 below). In the absence of CO2 in the inlet gas, the CO2 flow rate V transferred to the gas stream is... g CO2 equals the CO2 flow rate V in the exhaust gas. eCO2. Optionally, the method may include determining the CO2 flow rate V in the inlet gas. s The steps involved in CO2 processing may include, for example, sensor measurements or retrieving gas composition information from the gas mixer 130.

[0064] Subsequently, the CO2 reference flow rate V (S150) was determined based on the model. ref CO2, and its CO2 flow rate V g CO2 was compared to determine the performance of the (S160) gas exchange device 110.

[0065] This model typically includes one or more of a set of parameters or variables describing the operating conditions of the gas exchange device, such as the blood flow rate Q through the gas exchange device 110. b The airflow rate Q after passing through the gas exchange device 110 s The partial pressure of CO2 in the anoxic blood entering the gas exchange device 110 (p v CO2), CO2 concentration in the inlet gas (F) s The model may include CO2, hemoglobin concentration (Hb) in the blood, and optionally, the pH value of the blood. Additionally, the model may include a set of constants or weights specific to the gas exchange apparatus model design used.

[0066] In some examples, the flow rate V of blood-based CO2 released from the membrane of gas exchanger 110 into the purge gas is... b CO2 can be based on blood flow Q b and carbon dioxide concentration in anoxic blood C v CO2 and the concentration of carbon dioxide in oxygenated blood (C) a The difference between CO2 values ​​is used to determine (S130): (Equation 1) The control unit can be configured from the operating settings of the pump that circulates blood in the extracorporeal circuit, and / or by being arranged to generate an indicated flow rate Q. b The flow sensor uses a sensor signal to acquire blood flow Q. b It should be noted that the CO2 concentration C in the blood... v CO2 / C a CO2 can be determined using various methods known in the art. One possible method is to use methods based on pH and partial pressure (p). v CO2 / p a A model for CO2.

[0067] The flow rate V of blood-based CO2 released into the purge gas during gas exchange. b CO2 can be measured by measuring the CO2 flow rate V in the exhaust gas. gCO2 flow rate V, determined based on the gas flow (and, if applicable, the CO2 flow rate in the inlet gas). g CO2 was compared to verify the measured CO2 flow rate V. g The accuracy of CO2 determination. Therefore, the flow rate V of CO2 released during gas exchange based on blood gases can be determined. b CO2 corresponds to the CO2 flow rate V measured in the exhaust gas based on the gas flow. g CO2. If these two flows (V) b CO2 and V g If the difference or quotient between CO2 and CO2 exceeds a predetermined limit, such as 30% or more, then an error state can be determined.

[0068] As mentioned above, the CO2 flow rate V transferred into the airflow g CO2 can be based on the CO2 concentration F in the exhaust gas. e CO2 multiplied by the total flow rate of the exhaust gas Q e And taking into account any CO2 present in the inlet gas, the total flow rate Q of the exhaust gas is determined with sufficient accuracy due to the leakage flow through, for example, emergency outlet 116. e This may be challenging, therefore, the exhaust gas flow rate Q e Alternatively, it can be calculated based on the oxygen mass balance method.

[0069] An example of this method is in Figure 4 As shown in the figure. In this method, the oxygen uptake of the blood is determined based on the oxygen concentration in the blood before and after gas exchange, and is used together with the oxygen concentration in the expelled gas to determine the flow rate of the expelled gas. Therefore, the method includes determining (S121) the oxygen concentration C in the blood before gas exchange. v The steps for O2 exchange, and determining the oxygen concentration C in the blood after gas exchange (S122). a The steps involved in O2 exchange. Oxygen concentration C before and after gas exchange. v O2, C a O2 can be based on the oxygen saturation (S) in the blood before and after gas exchange. v O2, S a O2 and partial pressure p v O2, p a The O2 sensor data and hemoglobin concentration (Hb) are used to determine the concentration. Hemoglobin concentration (Hb) can be measured, for example, by a probe integrated into a gas exchange device or through a blood sample. The oxygen concentration (C) before gas exchange is also used. v Oxygen concentration C after O2 exchange with gas a The difference between O2 and oxygen concentration and blood flow Q bBy combining these factors, the oxygen uptake V during gas exchange (S123) can be determined. b O2: (Equation 2) Among them, blood flow Q b Information such as velocity (RPM) and pressure, as well as hematocrit and / or hemoglobin concentration (Hb) and temperature, can be measured by the flow sensor 127 or retrieved from the blood pump settings.

[0070] The method also includes, for example, oxygen concentration F based on the inlet gas. s O2 and total flow Q s Determine the oxygen flow rate V in the inlet gas (S124). s O2. These parameters may be known based on the settings of the gas mixer 130 and may be provided to the control unit by the gas supply module. The gas mixer 130 may, for example, be configured to deliver a total inlet flow of 4 L / min and an oxygen concentration of 80% or 100% oxygen. However, it should be understood that in some examples, the total inlet flow and / or oxygen concentration may be determined by one or more sensors, such as flow meters or sensors for measuring oxygen concentration, which may be included in the gas supply device. Other sensors may also be used to compensate for sensor inaccuracies and other sources or errors. Examples include pressure sensors, temperature sensors, and humidity sensors. The balance method is based on the assumption that the amount of oxygen leaving the gas exchange device 110 corresponds to the difference between the amount of oxygen supplied to the gas exchange device 110 and the amount of oxygen absorbed by the blood during gas exchange. This mass balance method can be described by the following expression: (Equation 3) Among them, V g O2 is the amount of oxygen taken up in the blood based on gas flow (corresponding to the amount of blood-based gas uptake V determined in Equation 2). b O2), F s O2 is the oxygen concentration in the purge gas supplied to the gas exchange device 110, Q s It is the inlet gas flow rate, F e O2 is the oxygen concentration in the exhaust gas, and Q e This is the total flow rate of the discharged gas. (Regarding Q) e Solve this problem and provide the following: (Equation 4) Oxygen concentration in exhaust gas F e O 2The oxygen concentration can then be determined (S125) based on sensor data from oxygen sensor 124, which is located at the outlet 114 of gas exchange device 110. The total flow rate of the discharged gas can then be determined (S126) using Equation 4 above.

[0071] Once the flow rate Q of the exhaust gas is determined... e CO2 flow rate V in the exhaust gas e CO2 can then be identified as (S126): (Equation 5) Among them, as mentioned above, F e CO2 can be obtained from CO2 sensor 121.

[0072] The CO2 flow rate V transferred to the gas stream during gas exchange g CO2 can be identified as: (Equation 6) Among them, V s CO2 is the CO2 flow rate in the inlet gas. In the absence of CO2 in the inlet gas, the CO2 flow rate V transferred to the gas stream is... g CO2 equals the CO2 flow rate V in the exhaust gas. e CO2.

[0073] As mentioned earlier, oxygen in the blood typically exists in two main forms: bound to hemoglobin (“oxygen saturation”), and directly dissolved in the plasma (“oxygen partial pressure”). Generally, most of the oxygen transported by the blood is bound to hemoglobin, with a small portion (e.g., 1.5% to 3%) dissolved in the plasma. Therefore, oxygen concentration C... v O2 / C a O2 usually refers to oxygen saturation (S). v O2 / S a O2, hemoglobin Hb and partial pressure p v O2 / p a The combination of O2. However, as mentioned above, in some examples, the oxygen concentration C v O2 / C a O2 can be determined solely by oxygen saturation S v O2 / S a The O2 concentration is approximated. Examples of how to determine the various concentrations will be discussed below.

[0074] Oxygen saturation S v O2 / S a O2 can be understood as the proportion of available oxygen-binding sites in hemoglobin occupied by oxygen molecules. In healthy adults, oxygen saturation in oxygenated blood is typically between 95% and 100%, while in oxygen-deficient blood it is typically between 60% and 80%.

[0075] It is known that each gram of hemoglobin can carry approximately 1.34 mL of oxygen at full saturation. Hemoglobin concentration (Hb) varies between individuals, and it is preferable to measure it on a patient-by-patient basis. Typically, hemoglobin levels range from 13.5 g / dL to 18 g / dL for adult men, from 12 g / dL to 15 g / dL for adult women, and from 11 g / dL to 16 g / dL for children. Therefore, the total concentration of oxygen bound to hemoglobin can be directly proportional to the oxygen saturation in the blood and the hemoglobin concentration.

[0076] oxygen partial pressure p v O2 / p a O2 can be calculated using a relationship known as Henry's Law. At body temperature, it is known that approximately 0.0033 mL of oxygen per mmHg of oxygen partial pressure dissolves in 1 mL of blood plasma.

[0077] The above relationship can be used to determine the blood (C) after gas exchange. a O2) and pre-gas exchange blood (C a The oxygen concentration in O2. This allows for a comparison of the oxygen concentration in oxygenated blood with the oxygen concentration in the blood before gas exchange (as shown in Equation 2 above) to determine the blood's oxygen uptake V using the following relationship. b O2 (e.g., in L / min): (Equation 7) Among them, S a O2 is the oxygen saturation (%) in the blood after gas exchange. v O2 is the oxygen saturation (%) in the blood before gas exchange. a O2 is the partial pressure of oxygen in the blood after gas exchange (mmHg), and p v O2 is the partial pressure of oxygen in the blood before gas exchange (mmHg).

[0078] It can be assumed that most of the oxygen supplied to the gas exchange device 110 is absorbed by the blood, or is transferred as excess oxygen to the exhaust gas stream. The oxygen concentration of the inlet gas is typically adjusted based on the patient's needs and the type of cardiac / lung support provided. Therefore, the oxygen concentration can range from approximately 21% to 100%. In the case where the inlet gas contains 100% oxygen, the oxygen flow rate V... s O2 corresponds to the total inlet gas flow rate Q. s After gas exchange occurs, the oxygen concentration F in the exhaust gas (or "waste" purge gas) is... e O2 may still remain relatively high, such as around 95% or above. However, it should be understood that the oxygen concentration F in the exhaust gas... eO2 can vary depending on several factors, such as the gas exchange efficiency between the purge gas and circulating blood, and blood flow rate Q. b Oxygen concentration F in the purge gas s O2, oxygen saturation in anoxic blood, and hemoglobin concentration (Hb).

[0079] Then, the CO2 flow rate V transferred to the gas stream during gas exchange can be compared. g CO2 and reference flow rate V ref The difference between V and CO2 is used to obtain S150 information about the performance of the gas exchange device 110. For example, if V g CO2 and V ref CO s If the difference or quotient between the two exceeds the predetermined limit, it can be determined that the gas exchange device needs to be replaced.

[0080] In some examples, CO2 flow rate V can be monitored. g Any rate and magnitude of change in CO2 over time—also known as trend—is used to assess whether a gas exchange unit is operating correctly or malfunctioning. A relatively stable CO2 flow rate V g CO2 can indicate that the gas exchange unit is operating correctly. If the problem persists, it may originate elsewhere, allowing the gas exchange unit to be ruled out as the source of the problem. Furthermore, the CO2 flow rate V... g Significant trends in CO2 (even if kept within acceptable limits) can indicate potential problems that might not be immediately apparent by relying on static measurements alone. For example, CO2 flow rate V g A rapid drop in CO2 may indicate a gradual deterioration in gas transport efficiency, requiring immediate attention to prevent further deterioration.

[0081] As mentioned above, the reference flow rate V ref CO2 can be determined using a model designed to describe the relationship between a set of variables and constants. The mathematical framework can vary depending on the system's physical characteristics, the scope of interest, and the availability of data. However, in general, the model can be represented by the following mathematical function: (Equation 8) in, x 1 、x 2 ……x n It is an input or a variable. f(·) This represents the functional relationship between the input and output, and a 1 、 a 2 ……a mThese are constants or weights that adjust the behavior of a function to best fit the applied data or theory. These constants can be determined by fitting the model to experimental data. Once set, these constants can be kept constant for a particular type or design of gas exchange device 110. Variables x 1 、x 2 ……x n The set of variables may differ between different examples in this disclosure. Typically, the set of variables includes one or more of the following: Q b Blood flow rate after passing through the gas exchange device Q s Flow rate of the gas flow supplied to the gas exchange device F s CO2: CO2 concentration in the inlet gas p v CO2: The partial pressure of CO2 in the blood entering the oxygenator Hb: Hemoglobin concentration in the blood pH: Blood pH value In some cases, blood flow Q has been observed b and gas flow rate Q s The transfer of CO2 from the blood to the airflow has the greatest impact. Therefore, the model can be a function of these two variables: (Equation 9) Furthermore, this can be considered in the model when the inlet gas includes CO2: (Equation 10) In some examples, the partial pressure p of carbon dioxide in the blood entering the gas exchange device can also be considered. v CO2, further model improvement: (Equation 11) Gas transport efficiency can also be affected by pH and / or Hb. Therefore, in some examples, the model considers this variable: (Equation 12) It should be noted that in some models, one or more variables, such as pH, Hb, and F, can be omitted. s CO2 and p v CO2. Specifically, when there is no CO2 in the inlet gas, F can be omitted. s CO2.

[0082] Depending on the system's physical characteristics, desired accuracy, and data availability, various types of models can be used. For example, a model could represent a reference flow rate V. ref A linear model showing the direct proportional relationship between CO2 and one or more of the above variables, or a polynomial model including higher power terms of one or more variables: (Equation 13) Higher-order polynomial models, such as sixth-degree polynomials, are also possible, and their application can be similar to that outlined in example equation 13 above.

[0083] S-shaped functions, such as logistic functions, can also be used. S-shaped functions typically have an "S"-shaped curve and are suitable for modeling the gas transfer efficiency of gas exchangers. An example including four parameters could be: (Equation 14) in, x 1 to x 4 They are Q b Q s p v CO2 and Hb, and a, b, and c1 through c4 are constants. Other examples of sigmoid functions include the hyperbolic tangent function, the arctangent function, the Gudermannian function, the error function, the generalized logic function, and the smoothing step function.

[0084] Regression methods can be used to establish a reference CO2 flow rate (V). ref The relationship between CO2 and one or more variables. This includes the least squares method, which takes the minimum of the sum of squares of the differences between observed and predicted CO2 flows. Other methods, such as Gaussian regression and ridge regression, are also possible. Additionally, various machine learning models, from regression trees to neural networks, can be used to estimate V. ref CO2.

[0085] The constants in the model can be derived from the system's observational data, ideally covering a wide range of conditions to accurately reflect the system's behavior under different scenarios. This data can be collected from instances of CO2 released into the gas stream from a new, undegraded gas exchanger 110 of the same model or design. Data acquisition can occur when replacing an old gas exchanger 110 with a new one, or during dedicated test runs. Data with CO2 flow rates transferred into the gas stream for different values ​​of one or more variables, such as blood flow rate Q, may be preferred. b Inlet gas flow rate Q s CO2 concentration F in the inlet gas sCO2, the partial pressure p of carbon dioxide in the blood entering the gas exchange device 110 v CO2, hemoglobin concentration (Hb), and pH.

[0086] As will be readily understood by those skilled in the art, various sensors can be employed to measure the oxygen concentration in inlet and / or outlet gases. However, water vapor condensation in outlet gases has been observed to pose a challenge, as water can interfere with the sensor and affect the relative concentrations of other gases, including oxygen. In some examples, this can be addressed by lowering the temperature of the outlet gas, allowing water vapor to condense in a more controlled manner before the sensor is exposed to the gas. The outlet gas can be cooled to ambient room temperature or even lower to further reduce its humidity. In other examples, the sensor can be heated directly (either directly on or near the sensor chip) or indirectly (the entire sensor assembly / tube) to reduce the risk of condensation interfering with sensor operation. Additionally, or alternatively, the outlet gas can be passed through a device that allows water vapor to be removed from the gas. One example of such a device is a Nafion tube. Combinations are also possible, where the outlet gas is cooled and the sensor is heated to further reduce the risk of condensation.

[0087] For blood gas measurement, oxygen sensors can be used to measure the oxygen content in the blood, such as oxygen saturation, and the partial pressure of oxygen in the blood after and before gas exchange. Sensors such as photoelectric or Clark electrodes can be used to measure the partial pressure of oxygen in the blood after and before gas exchange, respectively. Therefore, each of the oxygen sensor 122 on the inlet side and the oxygen sensor 123 on the outlet side of the gas exchange device 110 can include a corresponding sensor for measuring saturation and partial pressure, and in some examples, a sensor for measuring the hemoglobin concentration (Hb) in the blood.

[0088] The CO2 concentration in the airflow, inlet gas, and / or outlet gas can be obtained from one or more CO2 sensors, such as CO2 sensor 125 disposed at the inlet of gas exchanger 110 and CO2 sensor 126 disposed at the outlet of gas exchanger 110. Examples of CO2 sensors include, but are not limited to, infrared sensors that correlate the absorption level of carbon dioxide molecules to infrared light with the concentration of carbon dioxide molecules in the exhaust gas. Infrared sensors and Severinghaus electrodes can also be used to measure the partial pressure p of carbon dioxide in blood. v CO2 / p a CO2.

[0089] It should be understood that any sensor discussed herein can be integrated into the gas exchange device 110, i.e., permanently or alternatively installed at, for example, the outlet of the gas exchange device 110. However, in other examples, one or more sensors may be separate units configured to perform measurements, for example, of gas flow or blood flow. In other examples, one or more sensors may be integrated into the gas supply or exhaust module as described above.

[0090] The system 100 disclosed herein may generally include one or more control units 140 or processors, and one or more non-transitory computer-readable media storing first computer-executable instructions that, when executed by one or more processors, cause the system 100 to perform operations in... Figure 3 and Figure 4 At least some of the actions shown and described above.

[0091] Generally, system 100 may include circuitry configured (using one or more non-transitory computer-readable media) to implement the functions described herein. Suitable processors for executing instruction programs include, for example, general-purpose and special-purpose microprocessors, and a single processor or one of multiple processors or processing cores of any kind of computer. The processor may be supplemented by or incorporated into an ASIC (Application-Specific Integrated Circuit). Those skilled in the art will understand that the exemplary embodiments described above can be implemented in any suitable software, hardware, or firmware configuration or combination thereof. Exemplary hardware platforms for implementing the exemplary embodiments may include, for example, Intel x86-based platforms with compatible operating systems, Windows operating systems, Linux-based operating systems, Mac platforms and Mac operating systems, and mobile devices with operating systems such as iOS, Android, etc. In another example, exemplary embodiments of the methods described above may be implemented as a program containing lines of code stored on a non-transitory computer-readable storage medium, which, when compiled, can be executed on a processor or microprocessor.

[0092] The above embodiments should be understood as illustrative examples of the present invention. It should be understood that any feature described with respect to any embodiment may be used alone or in combination with other described features, and may also be used in combination with one or more features of any other embodiment, or in any combination of any other embodiment. Furthermore, equivalents and modifications not described above may be employed without departing from the scope of the invention as defined in the appended claims.

Claims

1. A method for determining the performance of a gas exchange device (110), the gas exchange device being coupled to the circulatory system of a patient (10) to transfer one or more blood gases between blood in the circulatory system and an airflow passing through the gas exchange device, the airflow entering the gas exchange device as an inlet gas and exiting the gas exchange device as an outlet gas, the method comprising: Based on the carbon dioxide concentration F in the exhaust gas e CO2, the carbon dioxide flow rate V in the inlet gas s CO2 and the flow rate Q of the exhaust gas e Determine the flow rate V of carbon dioxide transferred to the gas flow. g CO2; and Based on the carbon dioxide flow rate V transferred to the gas flow g CO2 and reference flow rate V ref CO2, to determine the performance of the gas exchange device; Wherein, the reference flow rate V ref CO2 is based on a model that describes the flow rate of carbon dioxide transferred to the gas stream as a function of at least one of the following: the blood flow rate Q through the gas exchange device. b The flow rate Q of the airflow s The carbon dioxide concentration F in the inlet gas s CO2, the partial pressure of carbon dioxide in the blood before gas exchange, p v CO2, the hemoglobin concentration (Hb) in the blood, and the pH value of the blood.

2. The method according to claim 1, wherein, said reference flow V ref CO2 corresponds to the flow rate of carbon dioxide transferred to the gas stream by means of the fresh gas exchange device.

3. The method according to claim 1 or 2, further comprising comparing the flow rate of carbon dioxide V g CO2 transferred into the gas stream ref CO2 with the reference flow rate V ref CO2, indicating that the gas exchange device needs to be replaced.

4. The method according to any one of the preceding claims, wherein, determining the flow rate V of carbon dioxide transferred into the gas stream g CO2 comprises: based on the blood flow Q b and the oxygen concentration C in the blood after gas exchange a O2; the difference between the oxygen concentration C in the blood before gas exchange v O2; and the oxygen uptake V of the blood is determined b O2; Based on the oxygen flow rate V in the inlet gas s O2 and the oxygen uptake V of the blood b The difference between O2 values ​​is used to determine the oxygen flow rate V in the exhaust gas. e O2; and Based on the oxygen flow rate V in the exhaust gas e O2 and the oxygen concentration F in the exhaust gas e O2, determine the flow rate Q of the discharged gas. e .

5. The method according to any one of the preceding claims further comprises, at least in part, based on the blood flow Q. b The partial pressure of carbon dioxide in the blood before gas exchange, p v After CO2 exchanges with the aforementioned gas, the partial pressure of carbon dioxide in the blood is p. a The difference between CO2 levels, the hemoglobin concentration (Hb) in the blood, and the pH of the blood are used to determine the blood-based carbon dioxide flow rate (V) transferred into the gas stream. b CO2.

6. The method according to claim 5, comprising comparing the blood gas based carbon dioxide flow rate V b CO2 transferred into the gas flow with the gas flow based carbon dioxide flow rate V g CO2 transferred into the gas flow, wherein, said gas flow-based flow rate V g CO2 is based on the carbon dioxide concentration F in said exhaust gas e CO2, said carbon dioxide flow rate V in said inlet gas s CO2 as well as the flow rate Q of said exhaust gas e determined.

7. The method of claim 6, comprising determining, based on the comparison, the blood gas based carbon dioxide flow rate V b CO2 corresponding to the gas flow based carbon dioxide flow rate V g CO2.

8. The method according to claim 5 or 6, comprising based on the blood gas-based carbon dioxide flow rate V b CO2 and the carbon dioxide flow rate V based on the gas flow g The difference between CO2 values ​​exceeds the predetermined limit, indicating an error state.

9. The method of claim 5, wherein, Determining the performance of the gas exchange device includes using the reference flow rate V ref CO2 and the carbon dioxide flow rate V based on blood gases b CO2 and flow rate V based on gas flow g Comparing the average CO2 values, The flow rate based on the gas flow is based on the carbon dioxide concentration F in the exhaust gas. e CO2, the carbon dioxide flow rate V in the inlet gas s CO2 and the flow rate Q of the exhaust gas e It's confirmed.

10. The method of any of the preceding claims, wherein, The model describes the flow rate of carbon dioxide released into the gas stream by the new gas exchange device, and the model is based on experimental data obtained from one or more new gas exchange devices.

11. The method of claim 10, wherein, The model is a function of a set of parameters, including at least one of the following: the blood flow rate Q b The flow rate Q of the airflow s The carbon dioxide concentration F in the inlet gas s CO2, the partial pressure of carbon dioxide in the blood before the gas exchange, p v CO2, the hemoglobin concentration (Hb) in the blood, the pH value of the blood; and wherein, a weight is assigned to each of these parameters, retrieved from experimental data.

12. A system (100) comprising: A gas exchange device (110) is used to transfer blood gases between the blood in the circulatory system of the patient (10) and an airflow passing through the gas exchange device. The airflow enters the gas exchange device as inlet gas and leaves the gas exchange device as outlet gas. a carbon dioxide sensor (121) configured to generate a signal indicative of a carbon dioxide concentration F in the exhaust gas e sensor data of CO2; as well as Control unit (140), the control unit is configured to: based on the carbon dioxide concentration F in the exhaust gas e CO2, the carbon dioxide flow rate V in the inlet gas s CO2and the flow rate Q of the exhaust gas e determining the carbon dioxide flow rate V transferred into the gas stream g CO2; and based on the flow rate of carbon dioxide V transferred into the gas stream g CO2 and the reference flow rate V ref CO2, determining the performance of the gas exchange device; The reference flow rate is based on a model that describes the flow rate of carbon dioxide transferred to the gas flow as a function of at least one of the following: the blood flow rate Q through the gas exchange device. b The flow rate Q of the airflow s The carbon dioxide concentration F in the inlet gas s CO2, the partial pressure of carbon dioxide in the blood before gas exchange, p v CO2, the hemoglobin concentration (Hb) in the blood, and the pH value of the blood.

13. The system according to claim 12, further comprising: Oxygen sensor devices (122, 123, 124), the oxygen sensor devices being configured to generate an indicator C of the oxygen concentration in the blood prior to the gas exchange. v O2, oxygen concentration in the blood after gas exchange (C) a O2 and the oxygen concentration F in the exhaust gas e O2 sensor data; The control unit is configured as follows: Based on the blood flow Q b And the oxygen concentration C in the blood after the gas exchange a O2 and the oxygen concentration in the blood before the gas exchange C v The difference between O2 and O2 is used to determine the oxygen uptake V of the blood. b O2; Based on the oxygen flow rate V in the inlet gas s O2 and the oxygen uptake V of the blood b The difference between O2 values ​​is used to determine the oxygen flow rate V in the exhaust gas. e O2; and Based on the oxygen flow rate V in the exhaust gas e O2 and the oxygen concentration F in the exhaust gas e O2, determine the total flow rate Q of the discharged gas. e .

14. The system of claim 13, further comprising a blood gas sensor device (125, 126), the blood gas sensor device being configured to generate an indication of the partial pressure p of carbon dioxide in the blood prior to the gas exchange. v CO2 and the partial pressure p of carbon dioxide in the blood after the gas exchange a CO2 sensor data.

15. The system of claim 14, wherein, The control unit is configured to be based at least in part on the blood flow Q. b The partial pressure of carbon dioxide in the blood before gas exchange, p v CO2, the partial pressure of carbon dioxide in the blood after the gas exchange, p a The carbon dioxide flow rate V transferred to the gas stream is determined by at least one of CO2, the hemoglobin concentration (Hb) in the blood, the oxygen saturation before and after gas exchange, and the pH value of the blood before and after gas exchange. b CO2.

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