Determination of exhaust gas flow of a blood oxygenator

Abstract

A method (200) for determining a total flow rate of exhaust gas leaving a gas exchange device (110) coupled to a circulatory system of a patient (10) is disclosed. The gas exchange device is configured to provide oxygen-rich blood to the circulatory system by exposing oxygen-poor blood to oxygen provided by an inlet gas and to allow excess oxygen to enter the exhaust gas. The method involves determining the total flow rate of the exhaust gas from a concentration and a flow rate of oxygen leaving the gas exchange device. The concentration is retrieved from a sensor, while the flow rate is determined based on a mass balance approach, wherein the amount of oxygen leaving the gas exchange device corresponds to the difference between the amount of oxygen supplied to the gas exchange device and the amount of oxygen taken up by the blood during gas exchange.

Description

Technical Field

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

[0002] Gas exchange in the blood is a physical process through which gases move across membranes, such as the blood-gas barrier in the alveoli of mammalian lungs, to allow oxygen to be absorbed by the blood and carbon dioxide to be released from the blood.

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

[0004] The performance of gas exchange equipment is crucial for patient safety and effective medical treatment. Insufficient oxygen intake or carbon dioxide release can rapidly lead to dangerous situations, jeopardizing patient health and safety. Therefore, comprehensive monitoring of the flow rate and composition of the purge gas is essential.

[0005] A common monitoring parameter is the amount of oxygen uptake in the blood, which can be estimated by the difference between the oxygen content of the incoming purge gas and the oxygen content of the outgoing purge gas (i.e., the oxygen content before and after gas exchange has occurred). This estimation typically requires knowledge of the total flow rate and oxygen concentration of the purge gas.

[0006] While the inflow velocity can be measured directly using appropriate measuring equipment, determining the output velocity with high accuracy is more challenging. Direct velocity measurement at the outlet of a gas exchange device carries the risk of missing leaks, such as purge gas escaping through emergency outlets often implemented in many gas exchange devices. Furthermore, the output purge gas is often saturated with water vapor, which can condense and thus limit the accuracy of the velocity measurement.

[0007] Therefore, there is a general need for improved and alternative technologies to monitor the flow rate of gas passing through gas exchange equipment, and in particular, to determine the total flow rate of exhaust gas leaving such gas exchange equipment. Summary of the Invention

[0008] In view of the foregoing, this disclosure provides improved or alternative techniques having the features set forth in the independent claims.

[0009] Therefore, according to a first aspect, a method is provided for determining the total flow rate of exhaust gas leaving a gas exchange device coupled to a patient's circulatory system, wherein the gas exchange device is configured to provide oxygenated blood to the circulatory system by exposing the patient's oxygen-deficient blood to oxygen supplied by the inlet gas, and to allow excess oxygen to enter the exhaust gas, the method comprising: Receive sensor data indicating the oxygen content in oxygen-rich blood and oxygen content in oxygen-depleted blood; The amount of oxygen uptake in the blood is determined at least in part based on the flow rate of blood through the gas exchange device and the difference between the oxygen content in oxygen-rich blood and oxygen-depleted blood. The oxygen flow rate in the inlet gas is determined at least in part based on the oxygen concentration in the inlet gas and the total flow rate of the inlet gas; The oxygen flow rate in the exhaust gas is determined at least in part based on the difference between the oxygen flow rate in the inlet gas and the oxygen uptake in the blood. Receive sensor data indicating the oxygen concentration in the exhaust gas; and The total flow rate of the exhaust gas is determined at least in part based on the flow rate and concentration of oxygen in the exhaust gas.

[0010] In a second aspect, a system is provided for exchanging one or more gases with blood in a patient's circulatory system. The system includes a gas exchange device having a gas inlet and an outlet, the gas inlet for receiving inlet gas and the outlet for discharging outlet gas, wherein the gas exchange device is configured to provide oxygenated blood by exposing the patient's oxygen-deficient blood to oxygen provided by the inlet gas, and to allow excess oxygen to enter the outlet gas. The system also includes a sensor device configured to generate sensor data indicating the oxygen content in the oxygenated blood, the oxygen content in the oxygen-deficient blood, and the oxygen concentration in the outlet gas. Further, the system includes one or more processors and one or more non-transitory computer-readable media storing instructions executable by the one or more processors, wherein the instructions, when executed, cause the system to perform operations including: The amount of oxygen uptake in the blood is determined at least in part based on the flow rate of blood through the gas exchange device and the difference between the oxygen content in oxygen-rich blood and oxygen-depleted blood. The oxygen flow rate in the inlet gas is determined at least in part based on the oxygen concentration in the inlet gas and the total flow rate of the inlet gas; The oxygen flow rate in the exhaust gas is determined, at least in part, based on the difference between the oxygen flow rate in the inlet gas and the oxygen uptake in the blood; and The total flow rate of the exhaust gas is determined at least in part based on the flow rate and concentration of oxygen in the exhaust gas.

[0011] In the above aspects, the total flow rate of the exhaust gas is obtained from the concentration and flow rate of oxygen leaving the gas exchange device. The concentration can be retrieved from sensors, while the flow rate can be determined based on a mass balance approach, in which the amount of oxygen leaving the gas exchange device is assumed to correspond to the difference between the amount of oxygen supplied to the gas exchange device and the amount of oxygen absorbed by the blood during gas exchange. The amount of oxygen absorbed by the blood can be determined based on blood sensor data by comparing the oxygen content in oxygen-rich blood with the oxygen content in oxygen-deficient blood. By subtracting the amount of oxygen absorbed by the blood from the amount of oxygen supplied to the gas exchange device, the amount of oxygen remaining in the purge gas after gas exchange can be determined. By combining the amount of oxygen 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.

[0012] Direct measurement of the total flow rate of the exhaust gas can be challenging for several reasons. First, the exhaust gas may be saturated with water vapor and may have a temperature rise corresponding to or close to the patient's body temperature. This is associated with a considerable risk of water vapor condensation, which can in turn reduce the accuracy of flow rate measurements, as condensed water can interfere with sensor readings, clog sensor pathways, and effectively alter the relative concentrations of other gases, including oxygen. Second, for patient safety reasons, many gas exchange devices are provided with an additional gas outlet, which is often arranged to be normally open to allow a portion of the exhaust gas to flow through it. This additional gas outlet forms an emergency outlet, preventing overpressure from forming in the gas exchange device if the main outlet is blocked for any reason. Because a portion of the exhaust gas can escape through the emergency outlet instead of the main outlet, a flow sensor located at the main outlet risks providing an inaccurate measurement of the total flow rate of the exhaust gas. As in some prior art, the total flow rate of the exhaust gas is approximated using the inlet gas flow rate, which can be particularly risky for gas exchange devices with leaks, such as those through the emergency outlet.

[0013] Therefore, this aspect provides an alternative to the method of determining the total velocity of the exhaust gas by direct velocity measurement or approximating the total velocity of the exhaust gas by the velocity of the inlet gas.

[0014] In the context of this disclosure, the terms "flow rate" or "velocity" generally refer to how a gas is moved through a system. Velocity can refer to the total flow rate of gas supplied to or discharged from a gas exchange device, or the flow rate of a specific component of the gas, such as oxygen or carbon dioxide. Velocity can generally be understood as a term describing the amount of gas moving through a given cross-sectional area per unit time, and can be measured in volume or mass. The former can be referred to as volumetric flow rate and describes the volume of gas that passes through a given area in a specific time. In SI systems, volumetric flow rate is often expressed in cubic meters per second (m³ / s). 3 The velocity is expressed in units of volumetric flow rate (L / min). However, in this context, the velocity is often expressed in liters per minute (L / min). Therefore, volumetric flow rate typically describes the number of liters of gas, such as oxygen, supplied to (or discharged from) a gas exchange device per minute. Alternatively, the velocity can be measured as mass flow rate, which describes the mass of gas (such as oxygen) that passes through a given area in a given time. Therefore, mass flow rate can be expressed in kilograms per second (kg / s). Mass flow rate can be particularly useful when the density of a gas may change under varying conditions, as it provides a measurement independent of temperature, pressure, and moisture content. It should be understood that volumetric flow rate is proportional to mass flow rate, and therefore for a given gas temperature and pressure, volumetric flow rate can be converted to mass flow rate (and vice versa).

[0015] Standard cubic centimeters per minute (SCCM) is an example of a unit that can be used to quantify the flow rate of a fluid, and can be understood as the mass flow rate of one cubic centimeter of gas per minute at a density defined under certain standard conditions of temperature and pressure. Standard conditions can vary between different regulatory agencies, but in this example, they can correspond to a temperature of 0 °C and a pressure of 1.01 bar.

[0016] The oxygen content in blood generally refers to the total concentration of oxygen carried by the bloodstream. Oxygen typically exists in blood in two main forms: bound to hemoglobin and dissolved directly in plasma. It should be understood that while other forms may exist, these two forms tend to constitute the majority of the oxygen content. Commonly, the majority of the oxygen transported in the blood is bound to hemoglobin, while a smaller portion of the oxygen in the blood is dissolved in plasma. Therefore, oxygen content generally refers to the total concentration of oxygen carried by hemoglobin and plasma. Oxygen content can be expressed as the volume of oxygen per unit volume of blood (such as milliliters of oxygen per deciliter of blood) or the amount of oxygen per unit volume of blood (such as millimoles of oxygen per deciliter of blood).

[0017] The oxygen concentration in the inlet and outlet gases is typically measured as a percentage of the total gas mixture. For example, depending on clinical needs, the concentration of medical oxygen supplied to a gas exchange device can range from about 21% (corresponding to the concentration in air) to 100%. This percentage is usually described as a volume ratio, such as liters of oxygen per liter of total gas. However, in some examples, the 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 oxygen per unit volume of the gas mixture.

[0018] Oxygenated blood typically refers to blood that has circulated through the body and delivered oxygen to the tissues. Therefore, oxygenated blood has a higher carbon dioxide concentration. Oxygenated blood can also be called deoxygenated blood or venous blood. Oxygenated blood can be supplied to gas exchange devices to enrich it with oxygen.

[0019] Oxygenated blood, also known as oxygenated blood or arterial blood, is understood as blood that has been enriched with oxygen through a gas exchange device. Oxygenated blood can be reinfused into a patient to supply oxygen to the tissues.

[0020] As mentioned above, the oxygen content in blood can refer to the total concentration of oxygen carried by the blood flow (including oxygen bound to hemoglobin and oxygen dissolved in the plasma). Therefore, sensor data can indicate both the concentration of oxygen bound to hemoglobin in oxygen-rich and oxygen-depleted blood, and the concentration of oxygen dissolved in the plasma of both oxygen-rich and oxygen-depleted blood. By considering both the concentration of oxygen bound to hemoglobin and the concentration of oxygen dissolved in the plasma, the total concentration or amount of oxygen absorbed by the blood during gas exchange can be determined with relatively high accuracy.

[0021] Alternatively or additionally, for anoxic blood or blood not fully saturated with oxygen, the concentration of oxygen bound to hemoglobin can be determined based on the concentration of oxygen dissolved in the plasma. This is based on the established relationship between the concentration of oxygen dissolved in the plasma (also known as oxygen partial pressure) and the concentration of oxygen bound to hemoglobin (also known as hemoglobin oxygen saturation). Therefore, by measuring the oxygen partial pressure in anoxic blood, this relationship can be used to estimate oxygen saturation without directly measuring the oxygen saturation level.

[0022] Various sensors can be employed to measure the oxygen concentration in exhaust gases. However, the condensation of water vapor in exhaust gases has been observed to pose a challenge, as it can interfere with the sensor and affect the relative concentrations of other gases, including oxygen. In some embodiments, this can be addressed by lowering the temperature of the exhaust gas to allow water vapor to condense in a more controlled manner before the sensor is exposed to the gas. The exhaust gas can be cooled to ambient room temperature or even lower to further reduce its humidity. In another example, the sensor can be heated directly (directly on or near the sensor chip) or indirectly (the entire sensor assembly / tube) to reduce the risk of condensed water interfering with sensor operation. Additionally or alternatively, the exhaust gas can be guided through a device that allows water vapor to be removed from the gas. An example of such a device is a Nafion tube, which will be referenced. Figure 1 The Nafion tube is described in further detail. It can also be combined with cooling the exhaust gas and heating the sensor to further reduce the risk of condensation.

[0023] It should be understood that the sensor used to measure the oxygen concentration in the exhaust gas can be integrated into the gas exchange device, i.e., permanently or replaceably installed at, for example, the outlet of the gas exchange device. However, in other examples, the sensor can be a separate unit configured to measure the exhaust gas downstream of the gas exchange device.

[0024] In some examples, the flow rate of carbon dioxide in the exhaust gas can be determined based on the total flow rate of the exhaust gas and sensor data indicating the concentration of carbon dioxide in the exhaust gas. The carbon dioxide flow rate can be used as an indicator of the performance of the gas exchange device, and more specifically, as the efficiency of performing gas exchange. A relatively low or reduced concentration or flow rate of carbon dioxide in the exhaust gas can indicate that the membrane of the gas exchange device is operating with reduced capacity, through which the gas exchange between the purge gas and the blood occurs. Common causes may include membrane sludge or blockage and deposits on the membrane fibers, which can increase diffusion resistance and reduce gas exchange efficiency. Therefore, the status of the gas exchange device can be determined by comparing the concentration or flow rate of carbon dioxide in the exhaust gas with a threshold measurement. If the concentration or flow rate of carbon dioxide meets or exceeds the threshold measurement, it can be determined that the gas exchange device is performing as intended. If the concentration or flow rate of carbon dioxide is below the threshold measurement, a warning or signal can be issued indicating that the gas exchange device needs to be replaced. The threshold measurement rate can be a predetermined reference value based on, for example, an operating point of the gas exchange device defined by the inlet flow rate of the purge gas, the flow rate of the blood through the gas exchange device, and the amount of carbon dioxide dissolved in the blood.

[0025] In the example above, some parameters used to determine the total flow rate of the exhaust gas can be predetermined or known from system settings, while other parameters can be retrieved from sensor data. The flow rate of blood through the gas exchange device, i.e., the velocity of blood under which gas exchange can occur, can be measured using an ultrasonic flow sensor or as known parameters determined by system settings, such as the pump speed 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 known from the settings of the inlet gas supply, such as from the settings of the gas mixer used to supply the required purge gas to the gas exchange device. However, the oxygen content in oxygenated and oxygen-depleted blood, and the oxygen concentration in the exhaust gas, can be retrieved from sensor data.

[0026] The second aspect can generally have the same features and advantages as the first aspect. It should also be noted that, unless otherwise expressly stated, this disclosure covers all possible combinations of features. Attached Figure Description

[0027] The above and additional objects, features, and advantages of this disclosure will be better understood through the following illustrative and non-limiting detailed description of examples of the present disclosure with reference to the accompanying drawings, in which the same reference numerals will be used for similar elements, wherein: Figure 1 A system based on an example is shown, which includes a gas exchange device coupled to an extracorporeal circulation loop.

[0028] Figure 2 An example of a method for determining the total flow rate of exhaust gas emitted by a gas exchange device is shown.

[0029] As shown in the figures, the dimensions of elements and features may be exaggerated for illustrative purposes and are therefore provided to illustrate the general structure of the example. Throughout the text, similar reference numerals indicate similar elements. Detailed Implementation

[0030] Figure 1System 100 is illustrated by way of example. System 100 is used to exchange one or more gases with blood in the circulatory system of patient 10. System 100 includes a gas exchange device 110 configured to provide oxygenated blood by exposing the patient 10's deoxygenated blood to oxygen supplied by an inlet gas, and to allow excess oxygen to enter the exhaust gas. The system also includes sensor devices 122, 123, and 124 configured to generate sensor data indicating the oxygen content in the oxygenated blood, the oxygen content in the deoxygenated blood, and the oxygen content in the exhaust gas. The sensor data can be processed by a processor 140 configured to determine the total flow rate of the exhaust gas based on the sensor data, such as by combining... Figure 2 A further detailed description.

[0031] Examples of the system 100 according to this disclosure include: a cardiopulmonary bypass machine (cardiopulmonary bypass machine) that provides circulatory and respiratory support in an operating room when the heart is stopped for surgery; an extracorporeal membrane oxygenation (ECMO) device that provides circulatory and respiratory support in an intensive care unit; and an extracorporeal carbon dioxide removal (ECCO2R) device that removes excess carbon dioxide from the blood.

[0032] In this example, a gas exchange device 110 is arranged in an extracorporeal circulation loop 105, in which the patient's blood is circulated through the gas exchange device 110 by means of a circulation unit 107. The extracorporeal circulation loop 105 typically includes fluid lines or loops for connecting the various components of the extracorporeal circulation loop and carrying the patient's blood through the gas exchange device 110.

[0033] For example, depending on the specific type of system 100, circulation unit 107 may include a roller pump or a centrifugal pump. A roller pump typically includes rotating rollers that compress a flexible tube or membrane. As the rollers rotate, they squeeze the tube, creating a pulsating flow of blood. On the other hand, a centrifugal pump uses a rapidly rotating impeller to generate centrifugal force, which pushes blood outward to create a substantially continuous flow of blood. Centrifugal pumps have been observed to reduce the risk of hemolysis, i.e., rupture of red blood cells, and to improve patient comfort.

[0034] Gas exchange device 110 is configured to facilitate the exchange of gases between a patient's blood and a purge gas passing through the gas exchange device 110. Typically, the gas exchange device is configured to allow oxygen to enter the blood from the purge gas for oxygenation, and is configured to allow carbon dioxide to be released from the blood and enter the purge gas. It should be understood that other types of gases and substances, including anesthetics and nitric oxide, can be exchanged in a similar manner.

[0035] The gas exchange device 110 may include a gas region 117 and a blood region 118 separated by a permeable membrane 119. In some examples, the gas exchange device 110 may be referred to as an oxygenator. Blood can be circulated through the blood region 118 via a circulation unit 107, while purge gas can flow through the gas region 117 via a gas inlet 112 and a gas outlet 114. At the gas inlet 112, the purge gas may be referred to as the inlet gas, and the gas leaving the gas exchange device 110 may be referred to as the outlet gas. Due to the partial pressure gradient or concentration difference between the components of the purge gas and their corresponding components in the blood, components can cross from the gas region 117 through the membrane 119 into the blood region 118, or vice versa. Specifically, oxygen can cross from the gas region 117 into the blood region 118 through the membrane 119, causing oxygenated blood to be oxygenated into oxygenated blood. Conversely, carbon dioxide can cross from the blood region 118 into the gas region 117 through the membrane 119, removing carbon dioxide from the blood flow.

[0036] Several types of membranes 119 can be used. In an example, the gas exchange device 110 includes a hollow fiber membrane in which blood flows in a blood region 118 inside the fibers, and a gas mixture flows in a gas region 117 outside the fibers. The exchange of oxygen and carbon dioxide can occur across the membrane formed by the walls of the hollow fibers. However, in Figure 1 In the example shown, membrane 119 is schematically shown as a sheet.

[0037] The oxygen or carbon dioxide transfer capacity, i.e., the amount of carbon dioxide or oxygen supplied to or removed from the blood flow per unit time, depends particularly on the blood flow rate, the volumetric flow rate of the purge gas, the composition of the purge gas, and the condition of the gas exchange device 110 itself. Specifically, the gas transfer capacity of membrane 119 may deteriorate over time due to blood clot buildup, the deposition of layers that increase diffusion resistance, and water vapor condensing inside and clogging the hollow fibers of the membrane. Therefore, a gas exchange device 110 that cannot oxygenate blood to a satisfactory level can be considered to be in a degraded or malfunctioning state.

[0038] The inlet gas can be provided by a gas mixer 130. Typically, the gas mixer 130 includes multiple inlets 132, 134, which are configured to receive medical gases from their respective gas sources (not shown). Figure 1 In the example shown, the gas mixer 130 includes a first inlet 132 and a second inlet 134, the first inlet 132 for a medical oxygen flow P1 and the 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 nitric oxide or anesthetics.

[0039] 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 a hospital facility, a pressurized gas cylinder, or any other type of oxygen source suitable for delivering oxygen for medical applications. The same applies to air, which can be supplied from a pressurized air outlet of a central medical gas system in a hospital facility, from a pressurized cylinder, or extracted and pressurized from ambient air.

[0040] The gases received at inlets 132 and 134 may be mixed into a purge gas mixture via a valve device (commonly indicated by reference numeral 135) and supplied to gas inlet 112 of the gas exchange apparatus 110. Valve device 135 may be configured to adjust the oxygen concentration and flow rate of the inlet gas according to the patient's needs, thereby allowing healthcare professionals to control the oxygen level delivered to the patient. Valve device 135 may be electrically controlled and, in some examples, configured to utilize sensor inputs to achieve accurate gas composition and flow rate.

[0041] Therefore, the gas mixer 130 can be operated to deliver oxygen of a specific concentration, such as 100% oxygen, at a specific flow rate, such as 4 liters per minute. Thus, the oxygen concentration and flow rate can be known or predetermined through the operating settings of the gas mixer 130 and used as inputs when calculating the total flow rate of the discharged gas, as discussed below. Additionally or alternatively, the mass flow rate of the gas can be determined. The mass flow rate can be determined by means of a mass flow sensor or by converting the volumetric flow rate to a mass flow rate. Conversion typically requires knowledge of the actual conditions of the gas flow, i.e., temperature and pressure, while mass flow rate measurement typically requires information related to the composition of the gas flow. For this purpose, temperature sensors, pressure sensors, and / or mass flow sensors (commonly indicated by reference numeral 125) can be provided.

[0042] exist Figure 1 In the example shown, an emergency outlet 116 is provided at the gas area 117 of the gas exchange device 110. The emergency outlet 116 forms an additional outlet, i.e., an additional outlet besides the "main" outlet 114 discussed above, and is used to protect the gas exchange device 110 and the patient 10 from damage 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 flow freely through the emergency outlet 116 during operation of the gas exchange device 110. Therefore, the total flow rate of the exhaust gas can be divided into partial flows: a first portion of the flow flows through the gas outlet 114, and a second portion of the flow flows through the emergency outlet 116.

[0043] Gas exchange equipment 110 can be arranged to release exhaust gas to the open air, a gas capture device, or a gas evacuation device (in... Figure 1(Not shown in the image). Gas capture devices or gas evacuation devices can be used to recover components of exhaust gases or to prevent, for example, anesthetics and high-pressure oxygen from accumulating in the ambient air. It should be understood that both main outlet 114 and emergency outlet 116 can be coupled to such capture devices or evacuation devices.

[0044] One or more sensor devices can be provided to generate sensor data indicating the oxygen content in anoxic blood, oxygen-rich blood, and the oxygen content in exhaust gases. Figure 1 In the example shown, a first sensor device 122 is arranged at the blood outlet of the gas exchange device 110 to measure the oxygen concentration in the oxygenated blood leaving the gas exchange device 110. Further, a second sensor device 123 is arranged at the blood inlet of the gas exchange device 110 to measure the oxygen concentration in the oxygen-deficient blood supplied to the gas exchange device 110.

[0045] The oxygen concentration of blood (upstream and downstream of gas exchange device 110) can refer to either oxygen bound to hemoglobin or oxygen dissolved in plasma. The amount of oxygen bound to hemoglobin can also be referred to as the oxygen saturation level, and can be measured using optical methods in which blood is irradiated and backscattered light is measured to determine the saturation level. Light at two or more separate wavelengths can be used separately to further increase the accuracy of measuring the oxygen saturation levels of oxygen-rich and oxygen-depleted blood.

[0046] Blood gas sensors can be used to measure the amount of oxygen dissolved in blood plasma, also known as oxygen partial pressure. These sensors are typically electrochemical sensors, such as Clarke electrodes, or optical sensors, such as photoelectrodes. Electrochemical sensors usually require contact with the blood via a permeable membrane that allows oxygen to pass towards the cathode, where it is electrolytically reduced. The reduction reaction generates a measurable current. The magnitude of this current is proportional to the concentration of dissolved oxygen in the blood.

[0047] Therefore, in Figure 1 In the example shown, each of the first sensor device 122 and the second sensor device 123 includes a sensor for measuring oxygen saturation, such as a spectral sensor, and a sensor for measuring oxygen partial pressure, such as a Clarke electrode or a photoelectrode. However, as will be readily apparent to those skilled in the art, other sensor configurations and techniques are also possible. Furthermore, in some examples, the oxygen saturation of hemoglobin in oxygen-rich and / or oxygen-depleted blood can be estimated based on oxygen partial pressure, rather than measured by a sensor. This estimation is based on a so-called oxygen dissociation curve, which is a known relationship describing the affinity of hemoglobin for oxygen and the ease with which hemoglobin absorbs and releases oxygen dissolved in plasma.

[0048] like Figure 1 As shown, the gas outlet 114 of the gas exchange device 110 can be equipped with a sensor 124 for measuring the oxygen concentration of the discharged gas, i.e., the gas discharged from the gas exchange device after the gas exchange process has occurred. For example, the sensor 124 can be: an electrochemical sensor that generates a current proportional to the oxygen concentration; a paramagnetic sensor that measures the change in the magnetic field caused by the presence of oxygen (due to the paramagnetic properties of oxygen); or an optical sensor that measures the phase shift of modulated light caused by oxygen molecules. Other types of sensors readily known to those skilled in the art are also possible.

[0049] In some examples, the water vapor content in the exhaust gas can be reduced before it reaches the sensor 124 used to measure oxygen concentration. Removing moisture from the exhaust gas reduces the risk of condensation, which in turn improves the accuracy of oxygen concentration measurements. The water vapor content can be reduced by cooling the gas (e.g., to room temperature) and allowing water vapor to condense in a more controlled manner. Additionally or alternatively, moisture can be removed using a Nafion tube (including a sulfonated tetrafluoroethylene vinyl fluoropolymer copolymer), through which the exhaust gas can be guided in its path to the sensor 124. The walls of the Nafion tube can typically be arranged to selectively allow water vapor to permeate through the tube walls, effectively “drying” the exhaust gas inside the tube. In another example, the sensor 124 can be heated to reduce the risk of water vapor condensation on the sensor 124. For example, the temperature of the sensor 124 can be increased by applying heat directly to the sensor chip or by applying heat to a structure adjacent to and in thermal contact with the sensor 124.

[0050] Each of the sensors and sensor devices 122, 123, and 124 discussed above may be an integrated component of the gas exchange device 110 (and therefore replaceable with the gas exchange device 110) or a separate element that may be attached to or within the gas exchange device 110. In the latter case, the sensor may be reusable, i.e., it may be used with more than one gas exchange device 110.

[0051] Sensors 122, 123, and 124 can be configured to communicate with processor 140 via wired or wireless connections, such as a local access network (LAN).

[0052] During operation of system 100, deoxygenated blood from the extracorporeal circulation loop is supplied to the blood region 118 of the gas exchange device 110, wherein the deoxygenated blood from the extracorporeal circulation loop is oxygenated by purge gas flowing through the gas region 117 of the gas exchange device 110. The flow rate of the blood through the gas exchange device 110 is expressed below as follows: Q 血液 The inlet velocity of the purging gas is expressed as Q 入口 And the total discharge velocity of the purge gas leaving the gas exchange device 110 is expressed as Q 排出 Blood flow rate Q 血液 The range is typically from 2 liters per minute (L / min) to 6 liters per minute (L / min), while the inlet gas flow rate... Q 入口 and the flow rate of the exhaust gas Q 排出 The range for each of these is typically from 1 L / min to 10 L / min.

[0053] The concentration or fraction of oxygen in the inlet gas is expressed below as follows: F 入口 O 2 The concentration of oxygen in the exhaust gas is expressed as... F 排出 O 2 The concentration of oxygen in the purge gas can usually be expressed as a volume ratio, i.e., liters of oxygen per liter of inlet / outlet gas. Therefore, the partial oxygen flow rate (also known as the oxygen velocity) in the inlet gas can be expressed as... F 入口 O 2 ·Q 入口 Furthermore, the flow rate of oxygen in the discharged gas can be expressed as... F 排出 O 2 ·Q 排出Typically, the inlet gas contains 100% oxygen, and the oxygen flow rate corresponds to the total inlet gas flow rate. After gas exchange has occurred, the oxygen concentration in the exhaust gas (or "used" purge gas) can still be relatively high, such as about 95%. However, it should be understood that the oxygen concentration in the exhaust gas can vary depending on several factors, such as the efficiency of gas exchange between the purge gas and circulating blood, the blood flow rate, the oxygen concentration in the purge gas, the oxygen saturation in the oxygen-deficient blood, and the concentration of hemoglobin.

[0054] As mentioned above, the oxygen flow rate in the inlet gas can be predetermined by controlling the operation settings of the gas mixer 130, while the oxygen flow rate in the exhaust air can be approximated by subtracting any oxygen absorbed by the blood during gas exchange in the gas exchange device 110 from the oxygen flow rate in the inlet gas. Therefore, by determining the flow rate of oxygen absorbed by the blood and comparing it with the flow rate of oxygen supplied to the gas exchange device 110, the flow rate of oxygen discharged from the gas exchange device 110 can be estimated.

[0055] Figure 2 The flowchart illustrates a method in which the flow rate of oxygen leaving gas exchange device 110 is determined and used to calculate the total flow rate of exhaust gas discharged from gas exchange device 110. The total flow rate of exhaust gas can then be used to determine the carbon dioxide exchange rate, which is an indicator of the overall performance or condition of gas exchange device 110, as discussed below.

[0056] Gas exchange device 110 can be used with Figure 1 The system disclosed herein is part of a similar system 100 and can therefore be coupled to a patient’s circulatory system to provide oxygenated blood by exposing deoxygenated blood to oxygen in a purge gas passing through a gas region 117 of a gas exchange device 110.

[0057] This method involves receiving (210) sensor data indicating the oxygen content in oxygen-rich blood and the oxygen content in oxygen-depleted blood. Oxygen content can refer to the total concentration of oxygen bound to hemoglobin and oxygen dissolved in the plasma. Typically, most of the oxygen is bound to hemoglobin, while a smaller portion of the oxygen (such as approximately 1.5%–3% of the total oxygen concentration) is directly dissolved in the plasma. References will be made below. Figure 1 and Figure 2 Discuss examples of how to determine the appropriate concentration.

[0058] The concentration of oxygen bound to hemoglobin is proportional to a parameter known as blood oxygen saturation, which can be understood as the proportion of available oxygen-binding sites in hemoglobin occupied by oxygen molecules. In healthy adult individuals, oxygen saturation of oxygen-rich blood is typically between 95% and 100%, while oxygen saturation of oxygen-deficient blood is typically between 60% and 80%.

[0059] Hemoglobin is known to carry approximately 1.34 mL of oxygen per gram when fully saturated. The concentration of hemoglobin in the blood varies between individuals and is preferably measured for each patient. Typically, hemoglobin levels range from 13.5 to 18 g / dL for adult men, 12 to 15 g / dL for adult women, and 11 to 16 g / dL for children. Therefore, the total concentration of oxygen bound to hemoglobin can be proportional to the oxygen saturation in the blood and the concentration of hemoglobin.

[0060] The concentration of oxygen dissolved in blood plasma can be considered to be proportional to the partial pressure of oxygen in the blood, and can be calculated using a relationship known as Henry's Law. At body temperature, given an oxygen partial pressure of mmHg, approximately 0.0033 mL of oxygen is dissolved in 1 mL of blood plasma.

[0061] The above relationship can be used to determine the concentration or oxygen content of oxygen in oxygen-rich and oxygen-deficient blood. This allows for the determination of (220) oxygen uptake in the blood by comparing the oxygen concentration in oxygen-rich blood with that in oxygen-deficient blood. VO 2 (For example, in L / min): ( Equation 1 ) Among them, Q 血液 Blood flow rate (L / min), Hb concentration (g / dL), and S... a O2 represents the oxygen saturation (%) in oxygen-rich blood. v O2 represents the oxygen saturation (%) in oxygen-deficient blood. a O2 is the partial pressure of oxygen in oxygen-rich blood (mmHg), and p v O2 is the partial pressure of oxygen in oxygen-deficient blood (mmHg).

[0062] As discussed above, the blood flow rate can be predetermined by controlling the operation settings of pump unit 107, while data indicating the oxygen concentration in the blood can be retrieved from sensor devices 122 and 123. In this example, a pulse oximeter can be used to measure the concentration of oxygen bound to hemoglobin in oxygen-rich and oxygen-depleted blood, while sensors such as optical electrodes or Clarke electrodes can be used to measure the concentration of oxygen dissolved in plasma in oxygen-rich and oxygen-depleted blood, respectively. Therefore, each of the first sensor device 122 and the second sensor device 123 may include a corresponding pulse oximeter and Clarke electrode. The pulse oximeter can be used to generate an indicator of oxygen saturation S in the blood. a O2, S v Sensor data on O2 and hemoglobin concentration, and Clark electrodes can be used to generate indicator partial pressure p. a O2, p v O2 sensor data. For example, in... Figure 1 As indicated, the first sensor device 122 may be placed at the outlet of the gas exchange device 110, and the second sensor device 123 may be placed at the inlet of the gas exchange device 110.

[0063] The oxygen flow rate in the inlet gas (230) can be determined based on the oxygen concentration in the inlet gas and the total flow rate of the inlet gas. As already mentioned, these parameters can be obtained from the settings controlling the operation of the gas mixer 130. For example, the gas mixer 130 can be configured to deliver a total inlet flow rate 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 rate and / or oxygen concentration can be determined by one or more sensors, such as by a flow meter or a sensor used to measure oxygen concentration.

[0064] The oxygen flow rate in the exhaust gas can be determined (240) based on the difference between the oxygen flow rate in the inlet gas and the oxygen uptake in the blood. This is based on the understanding that most of the oxygen supplied to the gas exchange device 110 is either absorbed by the blood or enters the exhaust gas stream as excess oxygen. This relationship can be expressed as: (Equation 2) in, VO 2 This refers to the oxygen uptake in the blood determined above. F 入口 O 2 This represents the concentration of oxygen in the inlet gas. Q 入口 The inlet gas velocity, F 排出 O2 The concentration of oxygen in the exhaust gas, and Q 排出 Let be the total velocity of the discharged gas. Solve for... Q 排出 get: (Equation 3) Oxygen concentration in exhaust gas F 排出 O 2 It can be retrieved from the sensor data received (250) from sensor device 124, which is arranged at the outlet 114 of gas exchange device 110, such as Figure 1 As shown in the example. Then, the oxygen concentration can be used together with Equation 3 above to determine the total flow rate of the exhaust gas.

[0065] In some examples, the total flow rate of the exhaust gas can be used to determine (280) the flow rate of carbon dioxide in the outlet gas. The flow rate of carbon dioxide can be determined based on the concentration of carbon dioxide in the exhaust gas and the total flow rate of the exhaust gas. The concentration of carbon dioxide can be received (270) from a carbon dioxide sensor, which can be included in a sensor device 124 located at the outlet 114 of the gas exchange device 110. Examples of carbon dioxide sensors include, but are not limited to, infrared sensors that correlate the level of absorption of infrared light by carbon dioxide molecules with the concentration of carbon dioxide molecules in the exhaust gas.

[0066] The concentration or flow rate of carbon dioxide in the exhaust gas can be used to determine the condition of (290) the gas exchange device 110. More specifically, the concentration or flow rate of carbon dioxide can be compared with reference values ​​such as threshold concentrations or flow rates. If the concentration or flow rate of carbon dioxide meets or exceeds the threshold concentration or flow rate, this indicates that the gas exchange device 110 is operating well and is therefore able to provide the expected gas exchange rate. If the concentration or flow rate of carbon dioxide is below the threshold rate, this indicates that the performance of the membrane 119 has deteriorated and the gas exchange device 110 may require maintenance or replacement.

[0067] It should be understood that the term "condition" in the context of gas exchange device 110 generally refers to the condition or performance level of the gas exchange device 110. In a well-functioning or normal state, gas exchange device 110 can provide a gas exchange rate within an acceptable range. This condition can be determined by comparing the concentration or flow rate of carbon dioxide in the exhaust gas with a reference measurement. In a degraded or malfunctioning state, the performance of gas exchange device 110 may have declined from its normal level. In this state, membrane 119 may not be able to facilitate the expected exchange of blood gases. In other examples, gas exchange device 110 may still be operational, but there is a risk that it may not be operating properly. In other words, patient safety may be compromised. The terms "degraded," "damaged," or "requiring maintenance" may be used to describe this state.

[0068] The system 100 of this disclosure typically includes one or more processors 140 and one or more non-transitory computer-readable media, the one or more non-transitory computer-readable media storing first computer-executable instructions, which, when executed by the one or more processors, cause the system 100 to perform... Figure 2 The text shows at least a portion of the actions described above.

[0069] Typically, system 100 may include a loop configured (using one or more non-transitory computer-readable media) to implement the functions described herein. Suitable processors for executing the program's instructions include, for example, both general-purpose microprocessors and special-purpose microprocessors, as well as a single processor or one of multiple processors or 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 OS, Mac platforms and MAC OS, mobile devices with operating systems such as iOS, Android, etc. In another example, exemplary embodiments of the methods described above may be embodied as programs containing lines of code stored on a non-transitory computer-readable storage medium that can be executed on a processor or microprocessor at compile time.

[0070] Additionally, through a study of the accompanying drawings, this disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. Furthermore, preferred examples of the invention have been disclosed in the drawings and description; although specific terminology has been used, such terminology is used only in a general and descriptive sense and not for limiting purposes. The scope of the invention is set forth in the appended claims, wherein the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

Claims

1. A method (200) for determining the total flow rate of exhaust gas leaving a gas exchange device coupled to a patient's circulatory system, wherein, The gas exchange device is configured to provide oxygenated blood to the circulatory system by exposing the patient's oxygenated blood to oxygen supplied by the inlet gas, and to allow excess oxygen to enter the exhaust gas, the method comprising: Receive (210) sensor data indicating the oxygen content in the oxygen-rich blood and the oxygen content in the oxygen-depleted blood; (220) The oxygen uptake in the blood is determined at least in part based on the flow rate of blood through the gas exchange device and the difference between the oxygen content in the oxygen-rich blood and the oxygen content in the oxygen-depleted blood; (230) The oxygen flow rate in the inlet gas is determined at least in part based on the oxygen concentration in the inlet gas and the total flow rate of the inlet gas; The oxygen flow rate in the exhaust gas is determined (240) based at least in part on the difference between the oxygen flow rate in the inlet gas and the oxygen uptake in the blood. Receive (250) sensor data indicating the oxygen concentration in the exhaust gas; and The total flow rate of the exhaust gas is determined (260) based at least in part on the flow rate of oxygen in the exhaust gas and the oxygen concentration in the exhaust gas.

2. The method according to claim 1, wherein, Sensor data indicating the oxygen content in the oxygen-rich blood and the oxygen content in the oxygen-depleted blood respectively indicate the amount of oxygen bound to hemoglobin in the oxygen-rich blood and the oxygen-depleted blood, and respectively indicate the amount of oxygen dissolved in the plasma of the oxygen-rich blood and the oxygen-depleted blood.

3. The method according to claim 2, wherein, Sensor data indicating the amount of oxygen dissolved in the plasma of the oxygen-rich blood and the oxygen-depleted blood, respectively, are measured by means of corresponding blood gas sensors.

4. The method according to any one of the preceding claims further includes: Lower the temperature of the discharged gas; then The sensor is exposed to the exhaust gas and is configured to generate sensor data indicating the oxygen concentration in the exhaust gas.

5. The method according to claim 4, comprising: The temperature of the discharged gas is reduced to ambient temperature.

6. The method according to claim 4 or 5, wherein, The sensor is integrated into the gas exchange device.

7. The method according to any one of the preceding claims further comprises: Receive (270) sensor data indicating the concentration of carbon dioxide in the exhaust gas; The flow rate of carbon dioxide in the outlet gas is determined (280) based at least in part on the carbon dioxide concentration and total flow rate of the exhaust gas; and The state of the gas exchange device is determined (290) at least in part based on the flow rate of the carbon dioxide meeting or exceeding a threshold flow rate.

8. The method according to any one of the preceding claims, wherein, Each of the blood flow rate, the oxygen concentration in the inlet gas, and the total flow rate of the inlet gas is a predetermined parameter.

9. A system (100) for exchanging one or more gases with blood in the circulatory system of a patient (10), comprising: A gas exchange device (110) includes a gas inlet (112) and an outlet (114), the gas inlet being for receiving inlet gas and the outlet being for discharging outlet gas, wherein the gas exchange device is configured to provide oxygenated blood by exposing the patient’s oxygenated blood to oxygen provided by the inlet gas, and to allow excess oxygen to enter the outlet gas; The sensor device (120) is configured to generate sensor data indicating the oxygen content in the oxygen-rich blood, the oxygen content in the oxygen-depleted blood, and the oxygen concentration in the exhaust gas; One or more processors; and One or more non-transitory computer-readable media storing instructions executable by the one or more processors, wherein the instructions, when executed, cause the system to perform operations including: The oxygen uptake in the blood is determined at least in part based on the flow rate of blood through the gas exchange device and the difference between the oxygen content in the oxygen-rich blood and the oxygen content in the oxygen-depleted blood. The oxygen flow rate in the inlet gas is determined at least in part based on the oxygen concentration in the inlet gas and the total flow rate of the inlet gas; The oxygen flow rate in the exhaust gas is determined at least in part based on the difference between the oxygen flow rate in the inlet gas and the oxygen uptake in the blood; and The total flow rate of the exhaust gas is determined at least in part based on the flow rate of oxygen in the exhaust gas and the oxygen concentration in the exhaust gas.

10. The system according to claim 9, wherein, The gas exchange device also includes an emergency outlet (116) through which at least a portion of the exhaust gas is discharged.

11. The system according to claim 9 or 10, wherein, The sensor device includes: A first pulse oximeter and a second pulse oximeter, the first pulse oximeter being configured to measure the oxygen saturation level of the oxygen-rich blood, and the second pulse oximeter being configured to measure the oxygen saturation level of the oxygen-deficient blood; and A first blood gas sensor and a second blood gas sensor, the first blood gas sensor being arranged to measure the partial pressure of oxygen in the oxygen-rich blood, and the second blood gas sensor being arranged to measure the partial pressure of oxygen in the oxygen-depleted blood.

12. The system according to claim 9 or 10, wherein, The operation also includes at least one of the following operations: The oxygen saturation level of the oxygen-enriched blood is determined based on the partial pressure of the oxygen-enriched blood; and The oxygen saturation level of the anoxic blood is determined based on the partial pressure of the anoxic blood.

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