Control of carbon dioxide transfer in oxygenator for extracorporeal blood gas exchange

Abstract

A method for controlling carbon dioxide [CO2] removal in a device (5) for extracorporeal blood gas exchange is disclosed. The device (5) comprises an oxygenator (21) comprising a membrane (23) acting as a gas-liquid barrier, which membrane (23) enables CO2 to be transferred between the blood flow through the oxygenator and the flow of purge gas. The method comprises the steps of measuring (S12a) a pre-oxygenator CO2 fraction [FCO2 in] in the purge gas stream upstream of the oxygenator (21), measuring (S12b) a pre-oxygenator purge gas flow rate (Vin) of the purge gas stream upstream of the oxygenator (21), measuring (S12c) a post-oxygenator CO2 fraction [FCO2 out] in the purge gas stream downstream of the oxygenator (21), a post oxygenator purge gas flow (Vout) of the purge gas stream downstream of the oxygenator (21) is measured (S12d), and a net CO2 exchange [VCO2 net] on the membrane (23) is calculated (S12e) based on the measured FCO2 inlet, Vin, FCO2 outlet and Vout.

Description

Technical Field

[0001] The present disclosure relates to the field of extracorporeal blood gas exchange for extracorporeal removal of carbon dioxide from a patient's blood using an oxygenator. In particular, the present disclosure relates to a method for controlling carbon dioxide exchange on an oxygenator by adding carbon dioxide to a purge gas flow flowing through the oxygenator. Background Art

[0002] Mechanical ventilators and medical devices for oxygenation and extracorporeal removal of CO2 from human blood are well-known examples of critical care equipment used to provide ventilation and sometimes circulatory support to patients with reduced lung function.

[0003] Mechanical ventilators are used to provide respiratory therapy to a patient by supplying breathing gases containing oxygen to the patient's lungs, thereby allowing CO2 to be removed from and oxygen to be added to the patient's circulatory system through gas exchange within the lungs.

[0004] Historically, medical devices for the extracorporeal removal of CO2 from human blood, often referred to as extracorporeal membrane oxygenation (ECMO) devices, have been used primarily to provide ventilation and circulatory support to patients with reduced lung and / or cardiac function when conventional and less invasive treatments, such as mechanical ventilation, are inadequate. Recently, however, combined treatment by ECMO devices and mechanical ventilators has also gained increasing interest among clinicians in the treatment of patients with less severe lung diseases.

[0005] In an ECMO device, carbon dioxide-rich blood is removed from the patient and provided to an oxygenator, which acts as an artificial lung by removing CO2 and adding oxygen to the blood before the oxygen-rich blood is returned to the patient's circulatory system. The removal of CO2 and the addition of oxygen are achieved by purging a purge gas flow containing oxygen through the oxygenator, thereby allowing gas exchange between the blood and the purge gas to occur across the oxygenator membrane.

[0006] The purge gas stream is typically an oxygen stream and / or an air stream. In this case, the extent of CO2 removal by the oxygenator can be controlled by adjusting the purge gas stream and / or the oxygen fraction in the purge gas stream, as described in, for example, US20150034082.

[0007] It is also known to add carbon dioxide to the purge gas stream to adjust the extent of CO2 removal by the oxygenator without affecting the addition of oxygen to the patient's blood. In particular, it allows the ongoing ventilation therapy provided by the mechanical ventilator and / or the patient's lung function to be assessed by minimizing CO2 removal by the oxygenator while reducing the risk of hyperventilation and improving pH control. This assessment is often referred to as a weaning test because it is sometimes performed to assess whether the patient is ready to be weaned from the ECMO device and / or mechanical ventilator.

[0008] Typically, to minimize CO2 removal by the oxygenator by adding CO2 to the purge gas flow, the clinician manually adjusts the addition of CO2 until the measured CO2 fraction in the purge gas flow upstream of the oxygenator equals the measured CO2 fraction in the purge gas flow downstream of the oxygenator. When the CO2 fraction upstream of the oxygenator matches the CO2 fraction downstream of the oxygenator, it is assumed that no CO2 removal is occurring at the oxygenator.

[0009] However, this assumption is often wrong due to, for example, the so-called Haldane effect, according to which oxygenation of the blood leads to a removal of CO 2 from hemoglobin, thereby increasing CO 2 removal.

[0010] Furthermore, manually controlling the CO 2 addition of the purge gas flow increases the clinician's manual workload and increases the risk of human error in patient treatment. Summary of the invention

[0011] It is an object of the present disclosure to propose methods, computer programs and systems for solving or alleviating one or more of the above mentioned problems associated with the prior art.

[0012] A specific object of the present disclosure is to propose methods, computer programs and systems for improving the control of the addition of CO 2 to an oxygenator purge gas flow in terms of accuracy and automation.

[0013] This object and other objects which will become apparent from the detailed description hereinafter below are achieved according to a first aspect of the present disclosure by a method, a computer program and a system as described below.

[0014] According to a first aspect of the present disclosure, there is provided a system for controlling CO2 removal in an apparatus for extracorporeal blood gas exchange, wherein the apparatus comprises an oxygenator, the oxygenator comprising a membrane acting as a gas-liquid barrier, the membrane enabling CO2 to be transferred between a blood flow through the oxygenator and a purge gas flow. The method comprises the following steps:

[0015] - adding CO2 to the purge gas flow upstream of the oxygenator to control the degree of CO2 removal from the blood flow by the oxygenator,

[0016] - Based on the pre-oxygenator CO2 content (CCO2 入 ) is a measure of the post-oxygenator CO2 content (CCO2 出 ) between the estimates (ΔCCO2 血液 ) to determine the CO2 removal measure of the oxygenator, and

[0017] - Using the CO2 removal measure to improve the regulation of CO2 addition to the purge gas stream.

[0018] By measuring CO2 removal as CCO2 in the blood stream upstream of the oxygenator 入 The measurement of CCO2 in the blood stream downstream of the oxygenator 出 The difference between the estimates of ΔCCO2 血液 , a more correct measure of CO2 removal can be obtained compared to solutions that control CO2 addition based on, for example, the difference between FCO2 measured upstream and downstream of the oxygenator. The proposed technique thus provides an accurate but relatively uncomplicated method of controlling the degree of CO2 removal performed by the oxygenator.

[0019] According to some embodiments, the step of utilizing the CO2 removal measure to improve regulation of CO2 addition to the purge gas stream comprises:

[0020] - presenting the CO2 removal measure to the operator of the plant as a decision support for manual adjustment of CO2 addition to the purge gas flow, and / or

[0021] - presenting a recommendation to the operator for adjusting CO2 addition to the purge gas flow based on the CO2 removal measure and the set target for CO2 removal by the oxygenator, and / or

[0022] - Automatically adjust CO2 addition of the purge gas flow based on CO2 removal measurements and a set target for CO2 removal by the oxygenator.

[0023] Improved manual adjustment of CO 2 addition may be obtained by presenting a measure of CO 2 removal to an operator of the device, thereby allowing the operator to adjust CO 2 addition to the purge gas stream to obtain a desired degree of CO 2 removal, such as zero CO 2 removal.

[0024] Recommendations for adjusting CO2 addition can be based on ΔCCO2, for example 血液 In one example, the suggestion may be to use the measured CO2 fraction (FCO2) in the purge gas flow upstream of the oxygenator to 入 ) Recommendations for adjusting by a certain amount or to a recommended level.

[0025] Automatic regulation of CO2 addition may be performed based on the CO2 removal measure and a set target value for CO2 removal. In particular, automatic regulation of CO2 removal may be advantageous in situations where CO2 removal by the oxygenator is undesirable. In such situations, a closed control loop may be used to regulate CO2 addition in an effort to achieve and / or maintain ΔCCO2 血液 is zero.

[0026] According to some embodiments, CO2 removal is measured by the pre-oxygenator CO2 partial pressure (PCO2) in the blood stream upstream of the oxygenator. 入 ) and O2 partial pressure (PO2 入 ) and the post-oxygenator CO2 fraction (FCO2) in the purge gas flow downstream of the oxygenator 出 ) and O2 fraction (FO2 出 ) measurements. The measurements of pre-oxygenator PCO2 and PO2 can be obtained by a standard blood gas analyzer (BGA). BGA is commonly used during ECMO therapy and is therefore easily available at the patient's bedside. By considering both pre-oxygenator and post-oxygenator CO2 and O2 when determining the CO2 removal measurement, the Holden effect can be compensated and a more reliable CO2 removal measurement can be obtained.

[0027] Thus, a first aspect of the present disclosure represents a semi-gas-based method for determining a measure of CO2 removal by an oxygenator, wherein blood gas analysis of a blood flow upstream of the oxygenator is combined with gas analysis of a purge gas flow downstream of the oxygenator.

[0028] According to some embodiments, the method comprises the following steps:

[0029] -Measurement of the pre-oxygenator CO2 partial pressure (PCO2) in the blood stream upstream of the oxygenator 入 ),

[0030] -Measurement of pre-oxygenator O2 partial pressure (PO2 入 ),

[0031] -Measurement of the post-oxygenator CO2 fraction (FCO2) in the purge gas flow downstream of the oxygenator 出 ),

[0032] -Measurement of the post-oxygenator O2 fraction (FO2 出 ),

[0033] -Based on FCO2 出 and FO2 出 To estimate the post-oxygenator CO2 partial pressure (PCO2 出 ) and post-oxygenator O2 partial pressure (PO2出 ),and

[0034] -Based on PCO2 入 PO2 入 、PCO2 出 and PO2 出 To determine CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 .

[0035] Pre-oxygenator CO2 content in the blood stream upstream of the oxygenator (CCO2 入 ) can be expressed as PCO2 入 PO2 入 , T 入，血液 and Hb 入 A function where T 入，血液 is the temperature of blood flow upstream of the oxygenator, and Hb 入 is the hemoglobin content of the blood stream upstream of the oxygenator. Similarly, an estimate of the post-oxygenator CO2 content (CCO2 出 ) can be expressed as PCO2 出 PO2 出 , T 出，血液 and Hb 出 A function where T 出，血液 is the temperature of blood flow downstream of the oxygenator, and Hb 出 is the hemoglobin content of the blood stream downstream of the oxygenator. 入 can be assumed to correspond to Hb 出 , and because T 入，血液 can be assumed to be relatively close to T 出，血液 , so in approximate determination of CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 These quantities do not need to be considered.

[0036] According to some embodiments, the method comprises the following steps:

[0037] -Measure or estimate the pre-oxygenator blood temperature (T 入，血液 ),

[0038] -Measure or estimate the post-oxygenator blood temperature (T 出，血液 ),and

[0039] -Based on PCO2 入 PO2 入 , T 入，血液 、PCO2 出 PO2 出, T 出，血液 To determine CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 .

[0040] By determining ΔCCO2 血液 By taking into account the pre-oxygenator and post-oxygenator temperatures of the blood flow, a more accurate measure of CO2 removal can be determined.

[0041] According to some embodiments, the method comprises the following steps:

[0042] - measuring or estimating the hemoglobin content (Hb) of the blood in the blood flow through the oxygenator, and

[0043] -Based on PCO2 入 PO2 入 , T 入，血液 、PCO2 出 PO2 出 , T 出，血液 and Hb to determine CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 .

[0044] By determining ΔCCO2 血液 By measuring and taking into account Hb, the CO2 transfer across the oxygenator membrane can be quantified and the actual net CO2 exchange in ml / min can be calculated. and use it as a CO2 removal measure. This is advantageous because a measure indicative of the actual CO2 removal in ml / min across the membrane can be presented to an operator of the device or used as a control parameter for manual, semi-automatic or automatic control of the purge gas flow rate and / or CO2 addition to the purge gas stream in order to meet a set target value for net CO2 exchange.

[0045] Therefore, the method may include the following steps:

[0046] -Based on ΔCCO2 血液 To calculate the net CO2 exchange across the membrane and

[0047] -use As a measure of CO2 removal.

[0048] According to some embodiments, the method comprises the following steps:

[0049] - receiving a target value for a CO2 removal measure, and

[0050] - Automatically regulate CO2 addition of the purge gas flow in order to reach and / or maintain a target value for a CO2 removal measure.

[0051] According to some embodiments, the device is connected to a patient, who is also connected to a mechanical ventilator for mechanically ventilating the patient by supplying breathing gas to the patient's lungs, wherein the target value is selected to be zero in order to evaluate the ventilation therapy provided by the mechanical ventilator and / or the patient's lung function.

[0052] The above mentioned features allow accurate and automatic performance of so-called weaning testing of a patient. By ensuring that the oxygenator is not involved in removing CO2 from the patient's blood, the patient's ventilation therapy and / or lung function can be reliably assessed.

[0053] According to a first aspect of the present disclosure, there is also provided a computer program for controlling CO2 removal in an apparatus for extracorporeal blood gas exchange, wherein the apparatus comprises an oxygenator, the oxygenator comprising a membrane acting as a gas-liquid barrier, the membrane enabling CO2 to be transferred between a blood flow through the oxygenator and a purge gas flow. The computer program comprises computer readable instructions that, when executed by a control computer, cause the above method to be performed.

[0054] According to a first aspect of the present disclosure, there is also provided a computer program product comprising a non-transitory storage hardware device storing a computer program for controlling CO2 removal in an apparatus for extracorporeal blood gas exchange, wherein the apparatus comprises an oxygenator, the oxygenator comprising a membrane serving as a gas-liquid barrier that enables CO2 to be transferred between a blood flow through the oxygenator and a purge gas flow. The computer program comprises computer-readable instructions that, when executed by a control computer, cause the above method to be performed.

[0055] According to a first aspect of the present disclosure, there is also provided a system for controlling CO2 removal in an apparatus for extracorporeal blood gas exchange, wherein the apparatus comprises an oxygenator, the oxygenator comprising a membrane acting as a gas-liquid barrier, the membrane enabling CO2 to be transferred between a blood flow passing through the oxygenator and a purge gas flow. The system further comprises a purge gas regulator for adding CO2 to the purge gas flow upstream of the oxygenator so as to control the degree of CO2 removal of the blood flow by the oxygenator. The apparatus further comprises at least one control computer, the at least one control computer being configured to:

[0056] - Based on the pre-oxygenator CO2 content (CCO2 入 ) is a measure of the post-oxygenator CO2 content (CCO2 出 ) between the estimates (ΔCCO2 血液 ) to determine the CO2 removal measure of the oxygenator, and

[0057] - Using the CO2 removal measure to improve the regulation of CO2 addition to the purge gas stream.

[0058] According to some embodiments, at least one control computer is configured to utilize the CO2 removal measure to improve regulation of CO2 addition to the purge gas stream by:

[0059] - presenting the CO2 removal measure to the operator of the plant as a decision support for manual adjustment of CO2 addition to the purge gas flow, and / or

[0060] - presenting to an operator of the apparatus a recommendation for adjusting CO2 addition to the purge gas flow, the recommendation being based on the CO2 removal measurement and a set target for CO2 removal by the oxygenator, and / or

[0061] - Automatically adjust CO2 addition of the purge gas flow based on CO2 removal measurements and a set target for CO2 removal by the oxygenator.

[0062] According to some embodiments, the control computer is configured to adjust the pre-oxygenator CO2 partial pressure (PCO2) in the blood flow upstream of the oxygenator. 入 ) and O2 partial pressure (PO2 入 ) and the post-oxygenator CO2 fraction (FCO2) in the purge gas flow downstream of the oxygenator 出 ) and O2 fraction (FO2 出 ) to determine the CO2 removal measure.

[0063] According to some embodiments, the control computer is configured to:

[0064] - Pre-oxygenator CO2 partial pressure (PCO2) in the blood stream upstream of the receiving oxygenator 入 ),

[0065] - Pre-oxygenator O2 partial pressure (PO2 入 ),

[0066] - The post-oxygenator CO2 fraction (FCO2) in the purge gas stream downstream of the receiving oxygenator 出 ),

[0067] -Receive the post-oxygenator O2 fraction (FO2 出 ),

[0068] -Based on FCO2 出 and FO2 出 To estimate the post-oxygenator CO2 partial pressure (PCO2 出) and post-oxygenator O2 partial pressure (PO2 出 ),and

[0069] -Based on PCO2 入 PO2 入 、PCO2 出 and PO2 出 To determine CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 .

[0070] According to some embodiments, the control computer is configured to:

[0071] - Estimating or receiving the pre-oxygenator blood temperature (T 入，血液 ),

[0072] - Estimating or receiving the post-oxygenator blood temperature (T 出，血液 ) and

[0073] -Based on PCO2 入 PO2 入 , T 入，血液 、PCO2 出 PO2 出 and T 出，血液 To determine CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 .

[0074] According to some embodiments, the control computer is configured to:

[0075] - estimating or receiving a measurement of the hemoglobin content (Hb) of the blood in the blood flow through the oxygenator, and

[0076] -Based on PCO2 入 PO2 入 , T 入，血液 、PCO2 出 PO2 出 , T 出，血液 and Hb to determine CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 .

[0077] According to some embodiments, the control computer is configured to:

[0078] -Based on ΔCCO2 血液 To calculate the net CO2 exchange across the membrane and

[0079] -use As a measure of CO2 removal.

[0080] According to some embodiments, the control computer is configured to:

[0081] - receiving a target value for a CO2 removal measure, and

[0082] - Automatically regulate CO2 addition to the purge gas flow in order to reach and / or maintain a target value.

[0083] According to some embodiments, the device is connected to a patient, who is also connected to a mechanical ventilator for mechanically ventilating the patient by supplying breathing gas to the patient's lungs, wherein the target value is selected to be zero in order to evaluate the ventilation therapy provided by the mechanical ventilator and / or the patient's lung function.

[0084] Another object of the present disclosure is to propose a method, a computer program and a system for quantifying CO2 removal in an oxygenator for extracorporeal blood gas exchange, which method, computer program and system are advantageously used to further improve the control of CO2 addition to the oxygenator purge gas flow.

[0085] According to a second aspect of the present disclosure, this object and other objects which will become apparent from the detailed description below hereinafter are achieved by the method, computer program and system described below.

[0086] According to this second aspect of the disclosure, there is provided a method for controlling CO2 removal in an apparatus for extracorporeal blood gas exchange, wherein the apparatus comprises an oxygenator, the oxygenator comprising a membrane acting as a gas-liquid barrier, the membrane enabling CO2 to be transferred between a blood flow through the oxygenator and a purge gas flow. The method comprises the following steps:

[0087] -Measurement of the pre-oxygenator CO2 fraction (FCO2) in the purge gas flow upstream of the oxygenator 入 ),

[0088] -Pre-oxygenator purge gas flow to measure the purge gas flow upstream of the oxygenator

[0089] -Measurement of the post-oxygenator CO2 fraction (FCO2) in the purge gas flow downstream of the oxygenator 出 ),

[0090] - Post-oxygenator purge gas flow to measure the purge gas flow downstream of the oxygenator and

[0091] - Based on measured FCO2 入 , FCO2 出 and To calculate the net CO2 on the membrane

[0092] Calculation of net CO2 exchange across the membrane The effect is that a measure of the actual CO2 removal in ml / min across the indicator membrane can be presented to an operator of the device, or used as a control parameter for manual, semi-automatic or automatic control of the purge gas flow and / or CO2 addition to the purge gas stream to meet a set target value for net CO2 exchange. The proposed technique is advantageous because it proposes a purely gas-based method for determining the actual CO2 removal by the oxygenator without the need for blood gas analysis.

[0093] According to some embodiments, the method comprises the following steps:

[0094] - adding CO2 to the purge gas flow upstream of the oxygenator to control the degree of CO2 removal from the blood flow by the oxygenator, and

[0095] -use Improved regulation of CO 2 addition to the purge gas stream as a measure of CO 2 removal.

[0096] By utilizing the actual net CO2 exchange to regulate the CO2 addition of the purge gas stream, an improved and more intuitive CO2 addition regulation is achieved. Compared to solutions that directly control CO2 addition based on the difference in CO2 fractions measured upstream and downstream of the oxygenator (or the difference between other surrogate parameters indicative of CO2 exchange across the membrane), The calculation of allows to visualize the actual effect of the regulation of CO2 addition in terms of the volume of CO2 removed per unit time. Furthermore, in contrast to solutions according to the prior art, it allows the operator to set a non-zero target value for net CO2 removal, whereby CO2 addition can be controlled manually, semi-automatically or automatically so that the calculated The value corresponds to the set target value.

[0097] According to some embodiments, the step of utilizing the CO2 removal measure to improve regulation of CO2 addition to the purge gas stream comprises:

[0098] - presenting the CO2 removal measure to the operator of the plant as a decision support for manual adjustment of CO2 addition to the purge gas flow, and / or

[0099] - presenting a recommendation to the operator for adjusting CO2 addition to the purge gas flow based on the CO2 removal measure and a set target for CO2 removal by the oxygenator, and / or

[0100] - Automatically adjust CO2 addition of the purge gas flow based on CO2 removal measurements and a set target for CO2 removal by the oxygenator.

[0101] According to some embodiments, the method comprises the following steps:

[0102] - measuring or estimating a pre-oxygenator at least one additional gas fraction in a purge gas flow upstream of the oxygenator, the at least one additional gas being one or more of water vapor (H2O), oxygen (O2), nitrogen (N2) and an anesthetic agent, and / or

[0103] - measuring or estimating a post-oxygenator at least one additional gas fraction in a purge gas flow downstream of the oxygenator, and

[0104] -based on FCO2 入 and at least one additional gas fraction of the pre-oxygenator to calculate the compensated pre-oxygenator purge flow and / or

[0105] -based on FCO2 出 and at least one additional gas fraction for the post-oxygenator to calculate the compensated post-oxygenator purge flow and

[0106] -based on and At least one of

[0107] Compensating the pre-oxygenator and / or post-oxygenator purge flow measurements by taking into account the composition of the purge gas and based on at least one additional gas fraction measured in the purge gas flow upstream and / or downstream of the oxygenator and One or both of these can provide more accurate Different and varying compositions of the purge gas flows upstream and downstream of the oxygenator typically introduce errors in the flow measurement due to the characteristics of the flow sensors used to obtain the measurements and calibration-related parameters. By calculating the compensated purge flow and Such errors can be eliminated or at least substantially mitigated.

[0108] According to some embodiments, the at least one additional gas comprises water vapor.

[0109] High concentrations of water vapor in the purge gas stream downstream of the oxygenator can cause several problems when it comes to flow and gas concentration measurements and comparisons in a membrane oxygenator. By appropriately measuring or estimating the water vapor fraction in the purge gas stream, gas composition measurements and purge gas flow measurements can be compensated based on the water vapor fraction in the purge gas stream upstream and / or downstream of the oxygenator. In particular, for measurements of purge gas flow downstream of an oxygenator where humidity is high, the water vapor fraction in the measured gas needs to be taken into account for a more accurate determination of the flow.

[0110] According to some embodiments, the method comprises the following steps:

[0111] -Based on FCO2 入 and in Measuring points and FCO2 入 The estimated water vapor addition or removal (ΔFH2O) of the purge gas between the measurement points 入 ) to calculate the compensated pre-oxygenator CO2 fraction (FCO2 入，补偿 ), compensated pre-oxygenator CO2 fraction (FCO2 入，补偿 ) represents An estimate of the CO2 fraction at the measurement point, and / or

[0112] -Based on FCO2 出 and in Measuring points and FCO2 出 The estimated water vapor addition or removal (ΔFH2O) of the purge gas between the measurement points 出 ) to calculate the compensated post-oxygenator CO2 fraction (FCO2 出，补偿 ), compensated post-oxygenator CO2 fraction (FCO2 出，补偿 ) represents An estimate of the CO2 fraction at the measurement point, and

[0113] -Based on FCO2 入，补偿 and FCO2 出，补偿 At least one of

[0114] In order to accurately calculate Not only does the measured flow rate need to be compensated, but also the measured CO2 fraction needs to be compensated in order to accurately reflect the CO2 fraction in the purge gas flow measured by the flow sensor. In particular, in cases where a sidestream gas analyzer is used to sample the purge gas from the purge gas outlet line of an oxygenator, the CO2 fraction in the measured purge gas sample may deviate significantly from the CO2 fraction in the purge gas outlet line due to the removal of water vapor from the gas sample to be measured. For example, it may be necessary to remove water vapor from the gas sample prior to the FCO2 measurement in order to avoid condensation of water vapor in the gas analyzer. The difference in H2O fraction ΔFH2O between the purge gas in the outlet line (where the post-oxygenator flow measurement is made) and the purge gas sample measured by the sidestream gas analyzer is 出 Introduced the measurement of FCO2 出 The difference between the actual CO2 fraction at the flow measurement point and the actual CO2 fraction at the flow measurement point. This difference can be calculated based on the FCO2 出 and in Measuring point and FCO2 出 Estimated water vapor addition or removal of the purge gas between the measurement points ΔFH2O 出 To calculate the compensated FCO2 出，补偿 The same applies to the upstream side of the oxygenator, although due to the relatively dry pre-oxygenator purge gas flow, the H2O fraction difference ΔFH2O between the purge gas in the purge gas inlet line of the oxygenator and the purge gas sample measured by the sidestream gas analyzer 入 Typically significantly smaller than the downstream side of the oxygenator.

[0115] For example, in some embodiments, the purge gas outlet line Measuring point and FCO2 in sidestream gas analyzer 出 Estimated water vapor addition or removal of the purge gas between the measurement points ΔFH2O 出 The post-oxygenator temperature (T 出，气体 ), measured or estimated post-oxygenator relative humidity (RH) of the purge gas flow downstream of the oxygenator 出 ), FCO2 出 The measured or estimated reference temperature (T 参考 ) and FCO2 出 The measured or estimated reference relative humidity (RH) at or near the measurement point 参考 ) is used for calculation. Similarly, Measuring point and FCO2 in sidestream gas analyzer 入 Estimated water vapor addition or removal of the purge gas between the measurement points ΔFH2O 入The pre-oxygenator temperature (T 入，气体 ), the measured or estimated pre-oxygenator relative humidity (RH) of the purge gas flow upstream of the oxygenator 入 ), FCO2 入 The measured or estimated reference temperature (T 参考 ) and FCO2 入 The measured or estimated reference relative humidity (RH) at or near the measurement point 参考 For example, when water vapor is removed from the sampled purge gas by conditioning the sample using, for example, a Nafion drying tube before providing it to the sidestream analyzer for FCO2 measurement, the reference relative humidity RH 参考 Typically corresponds to the ambient RH surrounding the Nafion drying tube. In other examples, when water vapor is removed from the sampled purge gas by conditioning the sample using, for example, silica gel before providing it to the lateral flow analyzer, the reference relative humidity RH 参考 can be assumed to be zero or close to zero.

[0116] According to some embodiments, Based on FCO2 入，补偿 and at least one additional gas fraction of the pre-oxygenator. According to some embodiments, Based on FCO2 出，补偿 and at least one additional gas fraction after the oxygenator to calculate.

[0117] By calculating the compensated purge gas flow rate from the compensated CO2 fraction and optionally from the measured value of the compensated additional gas fraction, independent of the measured fraction, an even higher purge gas flow rate measurement accuracy can be obtained, and thus a higher Determine the accuracy.

[0118] According to some embodiments, the method comprises the following steps:

[0119] - receiving a target value for a CO2 removal measure, and

[0120] - Automatically regulate CO2 addition of the purge gas flow in order to reach and / or maintain a target value for a CO2 removal measure.

[0121] According to some embodiments, a device for extracorporeal blood gas exchange is connected to a patient, who is also connected to a mechanical ventilator for mechanically ventilating the patient by supplying breathing gases to the patient's lungs, wherein the target value is selected to facilitate evaluation of the ventilation therapy provided by the mechanical ventilator and / or the patient's lung function, for example by selecting a target value corresponding to zero or near-zero CO2 removal.

[0122] This facilitates effective combined therapy of the patient by an oxygenator and a ventilator, since quantification of the net CO2 removal by the oxygenator allows the clinician to better understand the effect of the ongoing therapy and facilitates diagnosis of the patient's current lung status. It allows accurate and automatic performance of so-called weaning testing of the patient, since the ventilation therapy provided by the ventilator and / or the patient's lung function can be reliably assessed by setting a target value for the net CO2 removal by the oxygenator to zero or close to zero values.

[0123] The step of measuring the post-oxygenator purge gas flow rate is advantageously performed by measuring the post-oxygenator purge gas flow rate as the flow rate of the entire purge gas effluent stream leaving the oxygenator. Measuring the flow rate of the entire purge gas effluent stream is essential for accurately calculating is important.

[0124] In most oxygenators, the purge gas is exhausted to the atmosphere after passing through the oxygenator. Some oxygenators have more than one outlet for exhausting the purge gas, for example, as a precaution that one or more of the oxygenator outlets may be blocked during operation. In this case, in order to be able to measure the flow rate of the entire purge gas effluent stream leaving the oxygenator, it may be necessary to prevent the purge gas from leaving the oxygenator via all outlets except one of the plurality of outlets. Therefore, according to some embodiments in which the oxygenator includes more than one outlet for the purge gas, the method may include the steps of preventing the purge gas from passing through all outlets of the oxygenator except one outlet, and measuring the post-oxygenator purge gas flow rate as the flow rate of the purge gas flowing through the one outlet. Preventing the purge gas from flowing through one or more additional outlets of the oxygenator may be achieved by temporarily or permanently blocking one or more of the additional outlets, for example by blocking one or more of the additional outlets using a silicon plug or the like.

[0125] According to a second aspect of the present disclosure, there is also provided a computer program for controlling CO2 removal in an apparatus for extracorporeal blood gas exchange, wherein the apparatus comprises an oxygenator, the oxygenator comprising a membrane acting as a gas-liquid barrier, the membrane enabling CO2 to be transferred between a blood flow through the oxygenator and a purge gas flow. The computer program comprises computer readable instructions that, when executed by a control computer, cause the above method to be performed.

[0126] According to a second aspect of the present disclosure, there is also provided a computer program product comprising a non-transitory storage hardware device storing a computer program for controlling CO2 removal in an apparatus for extracorporeal blood gas exchange, wherein the apparatus comprises an oxygenator, the oxygenator comprising a membrane serving as a gas-liquid barrier that enables CO2 to be transferred between a blood flow through the oxygenator and a purge gas flow. The computer program comprises computer-readable instructions that, when executed by a control computer, cause the above method to be performed.

[0127] According to a second aspect of the present disclosure, there is also provided a system for controlling CO2 removal in an apparatus for extracorporeal blood gas exchange, wherein the apparatus comprises an oxygenator, the oxygenator comprising a membrane serving as a gas-liquid barrier, the membrane enabling CO2 to be transferred between a blood flow through the oxygenator and a purge gas flow. The system further comprises at least one control computer, the at least one control computer being configured to:

[0128] - The pre-oxygenator CO2 fraction (FCO2) in the purge gas flow upstream of the receiving oxygenator 入 ),

[0129] - a measurement of a pre-oxygenator purge gas flow rate of a purge gas flow upstream of a receiving oxygenator,

[0130] - The post-oxygenator CO2 fraction (FCO2) in the purge gas stream downstream of the receiving oxygenator 出 ),

[0131] - receiving a measurement of a post-oxygenator purge gas flow rate of a purge gas flow downstream of the oxygenator, and

[0132] - Based on measured FCO2 入 , FCO2 出 and To calculate the net CO2 on the membrane

[0133] According to some embodiments, the system includes a gas regulator for adding CO2 to a purge gas flow upstream of the oxygenator to control the degree of CO2 removal from the blood flow by the oxygenator, wherein the control computer is configured to utilize Improved regulation of CO 2 addition to the purge gas stream as a measure of CO 2 removal.

[0134] According to some embodiments, the control computer is configured to utilize the CO2 removal measure to improve regulation of CO2 addition to the purge gas stream by:

[0135] - presenting the CO2 removal measure to the operator of the plant as a decision support for manual adjustment of CO2 addition to the purge gas flow, and / or

[0136] - presenting a recommendation to an operator of the apparatus for adjusting CO2 addition to the purge gas flow based on the CO2 removal measure and a set target for CO2 removal by the oxygenator, and / or

[0137] - Automatically adjust CO2 addition to the purge gas stream based on CO2 removal measurements.

[0138] According to some embodiments, the control computer is configured to:

[0139] - estimating or receiving a measurement of a fraction of at least one additional gas pre-oxygenator in a purge gas flow upstream of the oxygenator, the at least one additional gas being one or more of water vapor (H2O), oxygen (O2), nitrogen (N2) and an anesthetic agent, and / or

[0140] - estimating or receiving a measurement of a fraction of at least one additional gas post-oxygenator in a purge gas flow downstream of the oxygenator, and

[0141] -based on FCO2 入 and at least one additional gas fraction of the pre-oxygenator to calculate the compensated pre-oxygenator purge flow and / or

[0142] -based on FCO2 出 and at least one additional gas fraction for the post-oxygenator to calculate the compensated post-oxygenator purge flow and

[0143] -based on and At least one of

[0144] According to some embodiments, the at least one additional gas comprises water vapor.

[0145] According to some embodiments, the control computer is configured to:

[0146] -Based on FCO2 入 and in The measuring point (P1) and FCO2 入 The estimated water vapor addition or removal (ΔFH2O) of the purge gas between the measurement points (P2) 入 ) to calculate the compensated pre-oxygenator CO2 fraction (FCO2 入，补偿 ), compensated pre-oxygenator CO2 fraction (FCO2 入，补偿 ) represents An estimate of the CO2 fraction at the measurement point (P1), and / or

[0147] -Based on FCO2 出 and in The measuring point (P3) and FCO2 出 The estimated water vapor addition or removal (ΔFH2O) of the purge gas between the measurement points (P4) 出 ) to calculate the compensated post-oxygenator CO2 fraction (FCO2 出，补偿 ), compensated post-oxygenator CO2 fraction (FCO2 出，补偿 ) represents An estimate of the CO2 fraction at the measurement point (P3), and

[0148] -Based on FCO2 入，补偿 and FCO2 出，补偿 At least one of

[0149] According to some embodiments, the control computer is configured to determine the post-oxygenator temperature (T 出，气体 ) and measured post-oxygenator relative humidity (RH 出 ) and FCO2 出 The measured or estimated reference temperature (T 参考 ) and the measured or estimated reference relative humidity (RH 参考 ) to calculate the purge gas outlet line Measuring point and FCO2 in sidestream gas analyzer 出 Estimated water vapor addition or removal of the purge gas between the measurement points ΔFH2O 出 Likewise, the control computer is configured to determine the pre-oxygenator temperature (T 入，气体 ) and measured or estimated pre-oxygenator relative humidity (RH 出 ) and FCO2 入 The measured or estimated reference temperature (T 参考 ) and the measured or estimated reference relative humidity (RH 参考 ) to calculate the purge gas inlet line Measuring point and FCO2 in sidestream gas analyzer 入 Estimated water vapor addition or removal of the purge gas between the measurement points ΔFH2O 入 .

[0150] According to some embodiments, Based on FCO2 入，补偿and at least one additional gas fraction of the pre-oxygenator. According to some embodiments, Based on FCO2 出，补偿 and at least one additional gas fraction after the oxygenator to calculate.

[0151] According to some embodiments, the control computer is configured to:

[0152] - receiving a target value for a CO2 removal measure, and

[0153] - Regulating the CO2 addition of the purge gas stream in order to reach and / or maintain a target value for the CO2 removal measure.

[0154] According to some embodiments, a device for extracorporeal blood gas exchange is connected to a patient, who is also connected to a mechanical ventilator for mechanically ventilating the patient by supplying breathing gases to the patient's lungs, wherein the target value is selected to facilitate evaluation of the ventilation therapy provided by the mechanical ventilator and / or the patient's lung function, for example by selecting a target value corresponding to zero or near-zero CO2 removal.

[0155] Further advantageous features of the method, computer program and system of the first and second aspects of the disclosure will be described in the detailed description below. BRIEF DESCRIPTION OF THE DRAWINGS

[0156] The present invention will be more fully understood through the detailed description and accompanying drawings provided below, which are given by way of non-limiting illustration only. In the different drawings, the same reference numerals correspond to the same elements.

[0157] Figure 1 An exemplary non-limiting embodiment of an ECMO ventilation system for extracorporeal removal of CO 2 from the blood of a patient undergoing mechanical ventilation is illustrated.

[0158] Figure 2 Pictured Figure 1 An exemplary non-limiting embodiment of an ECMO device of an ECMO ventilation system in.

[0159] Figures 3 to 5 is a flow chart illustrating an exemplary non-limiting embodiment of a method for controlling CO 2 removal in and by an ECMO device according to the first aspect of the present disclosure.

[0160] Figure 6 is a flow chart illustrating an exemplary non-limiting embodiment of a method for controlling CO 2 removal in and by an ECMO device according to the second aspect of the present disclosure. DETAILED DESCRIPTION

[0161] The present disclosure relates to the field of extracorporeal blood gas exchange by extracorporeal removal of carbon dioxide (CO2) from a patient's blood using an oxygenator. In particular, the present disclosure relates to a method, computer program and system for improving the control of CO2 removal by an oxygenator by adding CO2 to a purge gas flow through the oxygenator.

[0162] The present invention will be described in the context of a combined system for extracorporeal blood gas exchange via a membrane oxygenator during lung protective ventilation of a patient using a mechanical ventilator. However, it should be understood that the proposed control of the oxygenator is independent of the ventilator and that the operation of the oxygenator does not require the presence of a ventilator.

[0163] Figure 1 A system 1 for combined mechanical ventilation of the lungs of a patient 3 and extracorporeal removal of CO2 from the blood of the patient 3 is illustrated. The system 1 will be referred to hereinafter as the ECMO ventilation system. ECMO (Extracorporeal Membrane Oxygenation) is one of several terms used for extracorporeal blood gas exchange, wherein blood is pumped to a device sometimes called a heart-lung machine outside the body of the patient being treated, which removes CO2 and returns oxygen-rich blood to the patient. Other terms often used in the art for the same or similar treatments are ECLA (Extracorporeal Lung Assist), ECCO2R (Extracorporeal Removal of CO2), ECLS (Extracorporeal Life Support), and ECGE (Extracorporeal Membrane Gas Exchange), all of which are included in the term ECMO as used herein.

[0164] The ECMO ventilation system 1 comprises a device 5 for the extracorporeal removal of CO 2 from the blood of a patient 3 , hereinafter referred to as an ECMO device, and a mechanical ventilator 7 for mechanically ventilating the patient 3 by supplying breathing gases to the patient's lungs.

[0165] The ventilator 7 comprises or is connected to a source of pressurized breathing gas (not shown), which is supplied to the patient 3 via a patient circuit 9. In this example, the patient circuit 9 comprises an inspiratory line 11 for delivering a flow of breathing gas to the patient 3, and an expiratory line 13 for delivering a flow of expiratory gas exhaled by the patient away from the patient. The inspiratory line 11 and the expiratory line 13 are connected to each other via a so-called Y-piece 15, which in turn is connected to the patient 3 via a common line 17.

[0166] The ECMO device 5 is configured to: provide ECMO therapy to the patient 3 by generating an extracorporeal blood flow from the patient 3; oxygenate the blood through extracorporeal blood gas exchange in which CO2 is removed from the extracorporeal blood flow and oxygen (O2) is added to the extracorporeal blood flow; and return the oxygen-rich blood to the patient 3.

[0167] In order to generate blood flow to and from the patient 3, the ECMO device 5 may include a blood flow generator (not shown), typically in the form of one or several rollers, turbines and / or centrifugal pumps. The blood flow generator generates blood flow through a tubing system forming a blood flow channel 19 of the ECMO device 5, where portions of the channel may be heated to maintain a desired temperature of the blood when the blood is returned to the patient 3.

[0168] Blood gas exchange including blood oxygenation and CO2 removal occurs in the membrane oxygenator 21 of the ECMO device 5, in which a purge gas flow containing oxygen interacts with the blood in the blood flow channel 19 via a membrane 23 of the oxygenator 21. The membrane 23 acts as a gas-liquid barrier that is capable of transferring CO2 and O2 content between the blood flow of the oxygenator 21 flowing through the liquid side of the membrane 23 and the purge gas flow of the oxygenator 21 flowing through the gas side of the membrane 23.

[0169] The purge gas flow is generated by a purge gas generator 25 connected to one or more purge gas sources, which typically include one or both of an oxygen source and a compressed air source. According to the principles of the present disclosure, the purge gas generator 25 is also connected to a CO2 source so as to control the degree of CO2 removal on the oxygenator 21 by adding CO2 to the purge gas flow. The purge gas generator 23 is configured to deliver a controllable purge gas composition to the oxygenator 21 at a controllable purge gas flow rate.

[0170] The composition and optionally the flow rate of the purge gas generated by the purge gas generator 23 may be automatically controlled by a controller or control computer 27 of the ECMO apparatus 5 based on set target values ​​and sensor data obtained by various sensors 29, 31 of the ECMO apparatus 5. Specifically, the control computer 27 of the ECMO apparatus 5 may be configured to automatically control the addition of CO2 to a purge gas flow comprising either or both of oxygen and air based on a set target for a measure of CO2 removal by the oxygenator 21.

[0171] Hereinafter, the purge gas flow upstream of the oxygenator 21 (i.e., before the oxygenator from the perspective of the purge gas) will be referred to as the input purge gas flow or the pre-oxygenator purge gas flow, and the purge gas flow downstream of the oxygenator 21 (i.e., after the oxygenator from the perspective of the purge gas) will be referred to as the output purge gas flow or the post-oxygenator purge gas flow. The input purge gas flow flows from the purge gas generator 25 to the oxygenator 21 via the purge gas inlet line 33a of the ECMO device 5, and the output purge gas flow flows from the oxygenator 21 to the atmosphere or to an evacuation or recirculation system via the purge gas outlet line 33b. In most configurations, the ECMO system is an open system, which means that the post-oxygenator purge gas flow is allowed to escape into the surrounding environment. In some cases, particularly when anesthetic agents are added to the purge gas flow, a closed or semi-closed (purge) gas control system can be envisioned, similar to the gas control systems often used in anesthesia machines.

[0172] Likewise, the blood flow upstream of the oxygenator 21 (i.e., before the oxygenator from the perspective of blood flow) may be referred to as input blood flow or pre-oxygenator blood flow hereinafter, and the blood flow downstream of the oxygenator 21 (i.e., after the oxygenator from the perspective of blood flow) may be referred to as output blood flow or post-oxygenator blood flow. The input blood flow flows from the patient 3 to the oxygenator 21 via the blood flow inlet line 19a of the ECMO device 5, and the output blood flow flows from the oxygenator 21 and flows back to the patient 3 via the blood flow outlet line 19b of the ECMO device 5.

[0173] Now refer to Figure 2 , the sensors 29, 31 of the ECMO device 5 may include:

[0174] - A pre-oxygenator flow sensor 29a, which is used to measure the flow rate of the input purge gas flow The pre-oxygenator flow sensor 29a is a mainstream flow sensor, which means that it is configured to measure the flow of the purge gas flowing in the purge gas inlet line 33a. The pre-oxygenator flow measurement obtained by the pre-oxygenator flow sensor 29a occurs at a pre-oxygenator flow measurement point denoted as P1 in the purge gas inlet line 33a.

[0175] - a pre-oxygenator gas analyzer 29b for measuring at least the fraction FCO2 of CO2 in the input purge gas flow 入. The pre-oxygenator gas analyzer 29b may also be configured to measure the fraction of one or more additional gases selected from the group consisting of oxygen (O2), nitrogen (N2) and anesthetic agents. In this exemplary embodiment, the pre-oxygenator gas analyzer 29b is a so-called sidestream gas analyzer configured to extract a purge gas sample from the purge gas inlet line 33a and measure the fraction of CO2 in the purge gas sample at a pre-oxygenator CO2 measurement point denoted as P2, and optionally, the fraction of at least one additional gas. The pre-oxygenator CO2 measurement point P2 is separated in distance from the pre-oxygenator purge gas flow measurement point P1 by at least the length of the pre-oxygenator sample line 34a. In other embodiments, the pre-oxygenator gas analyzer 29b may be a so-called mainstream gas analyzer configured to measure the fraction of CO2 within the purge gas inlet line 33a, and optionally, the fraction of at least one additional gas. In some embodiments, the pre-oxygenator gas analyzer includes at least a CO2 sensor and an O2 sensor for measuring the fraction of CO2 and O2 in the purge gas sample, respectively. In some embodiments, the CO2 sensor is a non-dispersive infrared (NDIR) CO2 sensor. In some embodiments, the O2 sensor is a paramagnetic or electrochemical O2 sensor.

[0176] - a pre-oxygenator temperature sensor 29c, which is used to measure the temperature T of the input purge gas 入，气体 .

[0177] a pressure sensor 29d for measuring a purge gas circuit pressure P which corresponds substantially to the purge gas pressure in the gas inlet line 33a 气体 .

[0178] - A post-oxygenator flow sensor 31a, which is used to measure the flow rate of the output purge gas flow The post-oxygenator flow sensor 31a is a mainstream flow sensor, which means that it is configured to measure the flow rate of the purge gas flowing in the purge gas outlet line 33b. The post-oxygenator flow measurement obtained by the post-oxygenator flow sensor 31a occurs at a post-oxygenator flow measurement point denoted as P3 in the purge gas outlet line 33b.

[0179] - a post-oxygenator gas analyzer 31b for measuring at least the fraction FCO2 of CO2 in the output purge gas flow 出. The post-oxygenator gas analyzer 31b may also be configured to measure the fraction of one or more additional gases selected from the group consisting of oxygen (O2), nitrogen (N2) and anesthetic agents. In this exemplary embodiment, the post-oxygenator gas analyzer 31b is a so-called sidestream gas analyzer configured to extract a purge gas sample from the purge gas outlet line 33b and measure the CO2 fraction in the purge gas sample at a post-oxygenator CO2 measurement point denoted as P4, and optionally, the fraction of at least one additional gas. The post-oxygenator CO2 measurement point P4 is separated in distance from the post-oxygenator purge gas flow measurement point P3 by at least the length of the post-oxygenator sample line 34b. In other embodiments, the post-oxygenator gas analyzer 31b may be a so-called mainstream gas analyzer configured to measure the fraction of CO2 within the purge gas outlet line 33b, and optionally, the fraction of at least one additional gas. In some embodiments, the post-oxygenator gas analyzer includes at least a CO2 sensor and an O2 sensor for measuring the fraction of CO2 and O2, respectively, in the purge gas sample. In some embodiments, the CO2 sensor is an IR spectrometer for IR spectroscopy, such as IR absorption spectroscopy. In some embodiments, the O2 sensor is a paramagnetic O2 sensor.

[0180] - A post-oxygenator temperature sensor 31c for measuring the temperature of the output purge gas.

[0181] In some embodiments, the ECMO device 5 may also include or be connected to a pre-oxygenator blood gas analyzer 32 for measuring at least the partial pressure PCO2 of CO2 in the input blood flow. 入 The pre-oxygenator blood gas analyzer 32 can also be configured to measure the partial pressure of O2 in the input blood flow, PO2 入 The pre-oxygenator blood gas analyzer 32 can also be configured to measure the hemoglobin content Hb of the input blood flow. 入 In some embodiments, the blood gas analyser 32 is not incorporated into the ECMO apparatus 5, but is arranged to form part of another medical device connected to the ECMO apparatus 5 so that the ECMO apparatus 5 receives measurements obtained by the blood gas analyser. For example, the blood gas analyser may form part of a stand-alone blood gas analyser unit, commonly referred to as a BGA, which is typically used for intermittent blood gas analysis during ECMO therapy.

[0182] While referring to the previous drawings, reference will now be made to Figures 3 to 6The flowcharts shown in describe some functions and features of the ECMO ventilation system 1, which illustrate methods for controlling CO2 removal in and by the ECMO device 5. Unless otherwise specified, each method is a computer-implemented method performed by the ECMO device 5 when at least one processor 37 of the control computer 27 executes a computer program. The computer program includes computer-readable instructions that can be stored in a storage medium of the ECMO ventilation system 1, such as a non-transitory hardware storage device 39 of the control computer 27.

[0183] Figure 3 is a flow chart illustrating a method for controlling CO 2 removal in and by an ECMO device according to a first aspect of the present disclosure.

[0184] In a first step S1, CO2 is added to the purge gas flow upstream of the oxygenator 25 in order to control the degree of CO2 removal of the blood flow by the oxygenator 21. CO2 is added to the purge gas flow via a purge gas regulator 25 which is controlled manually, semi-automatically or automatically.

[0185] In a second step S2, based on the pre-oxygenator CO2 content (CCO2 入 ) and the post-oxygenator CO2 content (CCO2 出 ) between the estimates (ΔCCO2 血液 ) determines a measure of CO 2 removal by the oxygenator 21. This determination is made by the control computer 27 based on sensor data obtained by sensors 29a to 29d, sensors 31a to 31c and sensor 32.

[0186] In a third step S3, the CO2 removal measure is used to improve the regulation of CO2 addition to the purge gas stream.

[0187] In some embodiments, CO2 removal is measured by the pre-oxygenator CO2 partial pressure (PCO2) in the input blood stream, for example, obtained by a blood gas analyzer 32. 入 ) and O2 partial pressure (PO2 入 ) and the post-oxygenator CO2 fraction (FCO2) in the output purge gas stream obtained, for example, by the post-oxygenator gas analyzer 31b 出 ) and O2 fraction (FO2 出 ) is determined by the measured value.

[0188] Pre-oxygenator CO2 content in the blood flow CCO2 入 The measurement of blood flow can be expressed as the pre-oxygenator CO2 partial pressure (PCO2 入 ), blood flow pre-oxygenator O2 partial pressure (PO2入 ), blood flow pre-oxygenator temperature (T 入，血液 ) and the pre-oxygenator hemoglobin concentration (Hb 入 ). Similarly, the post-oxygenator CO2 content in the output blood flow, CCO2 出 The estimate of blood flow can be expressed as the post-oxygenator CO2 partial pressure (PCO2 出 ), post-oxygenator O2 partial pressure of blood flow (PO2 出 ), blood flow post-oxygenator temperature (T 出，血液 ) and post-oxygenator hemoglobin concentration (Hb 出 ). PCO2 入 and PO2 入 can be measured by a pre-oxygenator blood gas analyzer32, while PCO2 出 and PO2 出 can be assumed to correspond essentially to the post-oxygenator CO2 fraction (FCO2) measured in the outlet purge gas flow 出 ) and O2 fraction (FO2 出 ). Since the Hb concentration in the bloodstream can be assumed to be constant, Hb 入 and Hb 出 is offset, and CCO2 入 Estimation of CCO2 出 The difference between the estimates can be based on FCO2 入 FO2 入 、FCO2 出 FO2 出 , T 入，血液 and T 出，血液 to calculate.

[0189] Figure 4 is a diagram showing how this can be achieved in more detail Figure 3 Flowchart of a non-limiting example of determination of a measure of CO2 removal in step S2 of FIG.

[0190] like Figure 4 As shown in FIG. 1 , step S2 may include the following sub-steps:

[0191] S2a) For example, the pre-oxygenator CO2 partial pressure (PCO2) in the blood flow upstream of the oxygenator 21 is measured by means of a pre-oxygenator blood gas analyzer 32. 入 ),

[0192] S2b) For example, the pre-oxygenator O2 partial pressure (PO2 入 ),

[0193] S2c) For example, by means of a post-oxygenator gas analyzer 31b, the post-oxygenator CO2 fraction (FCO2) in the purge gas flow downstream of the oxygenator 21 is measured. 出 ),

[0194] S2d) For example, by means of a post-oxygenator gas analyzer 31b, the post-oxygenator O2 fraction (FO2 出 ),

[0195] S2e) based on FCO2 出 and FO2 出 To estimate the post-oxygenator CO2 partial pressure (PCO2) in the blood flow downstream of the oxygenator 21 出 ) and post-oxygenator O2 partial pressure (PO2 出 ),

[0196] S2f) Measure or estimate the pre-oxygenator blood temperature (T 入，血液 ). 入，血液 It can be measured using a pre-oxygenator blood temperature sensor (not shown), or T 入，血液 may be estimated, for example, based on an assumed and / or measured temperature of the patient 3, the temperature of the purge gas flow, the tube length of the blood flow channel 19, and / or the effect of a heater (not shown) for heating the blood in the blood flow channel,

[0197] S2g) Measure or estimate the post-oxygenator blood temperature (T 出，血液 ). 出，血液 It can be measured with a post-oxygenator blood temperature sensor (not shown), or T 出，血液 It may be estimated, for example, based on assumed and / or measured temperature of patient 3, temperature of the purge gas flow, tube length of blood flow channel 19 and / or the effect of a heater (not shown) for heating blood in the blood flow channel.

[0198] S2h) measuring or estimating the hemoglobin content (Hb) of the blood in the blood flow through the oxygenator 21, for example by means of a pre-oxygenator blood gas analyzer 32, and

[0199] S2i) according to PCO2 入 PO2 入 , T 入，血液 、PCO2 出 PO2 出 , T 出，血液 and Hb to determine CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 .

[0200] like Figure 4 As shown by the dashed line, the measured or estimated T 入，血液 、T 出，血液 The step of adjusting the Hb is optional. Since, for some situations and some oxygenator configurations, T 入，血液 can be assumed to correspond essentially to T 出，血液 , and since Hb is constant upstream and downstream of the oxygenator 21, CCO2 入 With CCO2 出 The difference between ΔCCO2 血液 Can be based on PCO2 alone 入 PO2 入 、PCO2 出 and PO2 出 However, in order to further improve the accuracy of the determination, T 入，血液 and T 出，血液 By determining the difference ΔCCO2 血液 When Hb is determined and used, this difference can be quantified and the actual net CO2 exchange can be calculated and the actual net CO2 exchange Used as a measure of the CO2 exchange on the oxygenator 21.

[0201] Figure 5 is a diagram illustrating how a certain measure of CO2 removal can be used in Figure 3 Flowchart of some non-limiting examples of improving the regulation of CO 2 addition to the purge gas flow in step S3 of FIG.

[0202] like Figure 5 As shown in FIG. 1 , step S3 may include one or more of the following steps:

[0203] S3a) Presenting the CO2 removal measure to the operator of the ECMO device 5 as a decision support for manually adjusting the CO2 addition of the purge gas flow. The CO2 removal measure may be presented, for example, on a display included in or connected to the ECMO device 5.

[0204] S3b) Based on the CO2 removal measure and the set target for CO2 removal for the oxygenator, presenting a suggestion for adjusting CO2 addition of the purge gas flow to the operator of the ECMO device 5. For example, the suggestion may be presented on a display included in or connected to the ECMO device 5. For example, the suggestion may be, for example, by manually increasing or decreasing the CO2 fraction (FCO2) in the purge gas flow upstream of the oxygenator 21. 入 ) set point to increase or decrease the CO2 addition of the purge gas flow.

[0205] S3c) Automatically adjusting CO2 addition to the purge gas stream based on the CO2 removal measurement and the set target for CO2 removal. For example, if the set target is zero CO2 removal, the control computer 27 can be configured to control the purge gas regulator 25 to adjust the CO2 fraction in the inlet purge gas stream so as to achieve and / or maintain zero CO2 removal.

[0206] Figure 6 is a flow chart illustrating a method for controlling CO 2 removal in and by an ECMO device 5 according to a second aspect of the present disclosure.

[0207] In an optional first step S11 , CO 2 is added to the purge gas flow upstream of the oxygenator 21 in order to control the extent of CO 2 removal of the blood flow of the patient 3 by the oxygenator 21 .

[0208] In a second step S12, the net CO2 exchange across the membrane 23 of the oxygenator 21 is calculated.

[0209] Step S12 includes the following sub-steps:

[0210] S12a) For example, by means of a pre-oxygenator gas analyzer 29b, the pre-oxygenator CO2 fraction (FCO2) in the purge gas flow upstream of the oxygenator 21 is measured. 入 );

[0211] S12b) Measuring the pre-oxygenator purge gas flow of the purge gas flow upstream of the oxygenator 21, for example by means of the pre-oxygenator flow sensor 29a

[0212] S12c) For example, by means of a post-oxygenator gas analyzer 31b, the post-oxygenator CO2 fraction (FCO2) in the purge gas flow downstream of the oxygenator 21 is measured. 出 );

[0213] S12d) Measuring the post-oxygenator purge gas flow rate of the purge gas flow downstream of the oxygenator 21, for example by means of the post-oxygenator flow sensor 31a and

[0214] S12e) Based on measured FCO2 入 , FCO2 出 and To calculate the membrane 23 net.

[0215] In an optional third step S13, using Improve the regulation of CO2 addition to the purge gas stream as a measure of CO2 removal. Step S13 may include Figure 5 Any one or any combination of steps S3a to S3c shown in FIG. 1, using the calculated As a measure of CO2 removal.

[0216] The CO2 fraction (FCO2) in the input purge gas flow can be calculated according to the following equation 入 ) multiplied by the input purge gas flow rate Subtract the CO2 fraction (FCO2) in the output purge gas stream 出 ) multiplied by the output purge gas flow rate

[0217]

[0218] Of course, in order to accurately calculate the CO2 flow into and out of the oxygenator 21, the term FCO2 入 and FCO2 出 Should be reflected in and The true fraction of CO2 at the measurement point. Due to the humid environment downstream of the oxygenator (usually close to 100% RH), it is usually necessary to condition the purge gas (e.g. dry it) before it enters the gas analyzer, for example to prevent water condensation inside the gas analyzer. Therefore, refer again to Figure 2 The ECMO device 5 may include a water vapor trap or gas sample regulator (not shown) for conditioning the purge gas sample before it enters the post-oxygenator gas analyzer 31 b and in particular for drying the purge gas sample extracted from the purge gas outlet line 33 b. The gas sample regulator may, for example, include a section of Nafion tubing or silica gel. As water is removed by the gas sample regulator, the composition of the measured purge gas sample is consistent with the measured The composition of the purge gas flow in the purge gas outlet line 33b is different. Therefore, the CO2 fraction FCO2 measured by the side stream post-oxygenator gas analyzer 31b at the measurement point P4 is 出 It will not accurately reflect the CO2 fraction at the output purge gas flow measurement point P3.

[0219] To this end, the method may further include the following steps:

[0220] -Based on FCO2 入 and in Measuring points P1 and FCO2 入 The estimated water vapor addition or removal ΔFH2O of the purge gas between the measurement points P2 入To calculate the compensated pre-oxygenator CO2 fraction (FCO2 入，补偿 ), whose representatives are An estimate of the CO2 fraction at the measuring point P1, and / or

[0221] -Based on FCO2 出 and in Measuring point P3 and FCO2 出 The estimated water vapor addition or removal (ΔFH2O) of the purge gas between the measurement points P4 出 ) to calculate the compensated post-oxygenator CO2 fraction (FCO2 出，补偿 ), whose representatives are An estimate of the CO2 fraction at the measurement point P3, and

[0222] -based on and and FCO2 入，补偿 and FCO2 出，补偿 At least one of

[0223] For example, the compensated post-oxygenator CO2 fraction (FCO2 出，补偿 ) can be calculated as the measured post-oxygenator CO2 fraction (FCO2 出 ) and in Measuring point P3 and FCO2 出 The estimated addition or removal of water vapor (ΔFH2O) of the purge gas between the measurement points P4 出 ) and is used for Determination of:

[0224] FCO2 出，补偿 = f(FCO2 出 , ΔFH2O 出 ) Equation 2

[0225]

[0226] In some embodiments, the estimated water vapor addition or removal ΔFH2O 出 The post-oxygenator temperature (T 出，气体 ); measured or estimated post-oxygenator relative humidity (RH) of the purge gas flow downstream of the oxygenator 出 ); FCO2 出 The measured or estimated reference temperature (T 参考 ); and FCO2 出 The measured or estimated reference relative humidity (RH) at or near the measuring point P4 参考In embodiments where the gas sample conditioner comprises a section of Nafion tubing, the reference relative humidity RH 参考 can be assumed to correspond to the relative humidity of the air surrounding the Nafion tube. In embodiments where the gas sample conditioner comprises silica gel, the reference relative humidity RH 参考 Can be assumed to be zero or close to zero. Post-oxygenator relative humidity RH 出 In most cases it can be assumed to be 100%, but in some embodiments it can be measured by a humidity sensor (not shown) of the ECMO device 5 arranged downstream of the oxygenator 21 .

[0227] exist Another potential source of error in the calculation of is inaccuracy in the purge gas flow measurement. and The flow sensors 29a and 31a are usually calibrated for a specific gas composition, and the deviation between the actual composition of the measured purge gas and the assumed composition introduces errors in the flow determination. Therefore, the method may further include the following steps:

[0228] - measuring or estimating a pre-oxygenator at least one additional gas fraction in the purge gas flow upstream of the oxygenator 21, the at least one additional gas being one or more of water vapor (H2O), O2, nitrogen (N2) and an anesthetic agent, and / or

[0229] - measuring or estimating a post-oxygenator at least one additional gas fraction in a purge gas flow downstream of the oxygenator, and

[0230] -based on FCO2 入 and at least one additional gas fraction of the pre-oxygenator to calculate the compensated pre-oxygenator purge flow and / or

[0231] -based on FCO2 出 and at least one additional gas fraction for the post-oxygenator to calculate the compensated post-oxygenator purge flow and

[0232] -Based on FCO2 入 、FCO2 出 as well as and At least one of

[0233] Compensating the pre-oxygenator and / or post-oxygenator purge flow measurements by taking into account the composition of the purge gas and based on at least one additional gas fraction measured in the purge gas flow upstream and / or downstream of the oxygenator and To obtain more accurate value.

[0234] For example, compensated post-oxygenator purge gas flow It can be calculated according to the following equation: FCO2 出 and post-oxygenator O2 fraction, water vapor fraction, and / or N2 fraction as a function of:

[0235]

[0236] Among them, FCO2 出 and FO2 出 is the CO2 fraction and O2 fraction measured by the sidestream post-oxygenator gas analyzer 31b, FH2O 出 is the water vapor fraction in the purge gas stream downstream of the oxygenator, FH2O 出 The post-oxygenator temperature T can be calculated based on the measured purge gas flow downstream of the oxygenator. 出，气体 and the measured or estimated post-oxygenator relative humidity RH of the purge gas flow downstream of the oxygenator 出 To determine, and FN2 出 is the post-oxygenator N2 fraction, FN2 出 It may be measured by the post-oxygenator gas analyzer 31b, or may be assumed to correspond to the remaining post-oxygenator purge gas flow fraction.

[0237] Then it can be calculated as:

[0238]

[0239] As discussed above, it is often necessary to use a gas sample conditioner to dry the gas sample between the purge gas sampling point in the purge gas outlet line 33b and the sidestream post-oxygenator gas analyzer 31b. The water vapor content removal or reduction performed by the gas sample conditioner is The purge gas composition in the purge gas outlet line of the sidestream gas analyzer 31b introduces a deviation between the purge gas composition in the sidestream gas analyzer 31b and the purge gas sample measured by the sidestream gas analyzer 31b. Therefore, in order to further improve the compensated post-oxygenator purge gas flow The accuracy of determination is In the determination of CO2, the compensated post-oxygenator CO2 fraction FCO2 may be advantageously used according to the following equation: 出，补偿 Instead of measuring the post-oxygenator CO2 fraction FCO2 出 :

[0240]

[0241] The fraction of any additional gas measured by the post-oxygenator sidestream gas analyzer 31b, such as the measured O2 fraction (FO2 出 ) and / or measured N2 fraction (FN2 出 ) can also be based on additional gas measured by a gas analyzer in Estimated water vapor addition or removal ΔFH2O of the purge gas between measuring point P3 and measuring point P4 出 The compensated additional gas fraction can be calculated as the measured additional gas fraction and the estimated water vapor addition or removal ΔFH2O according to the following equation: 出 Function:

[0242] FO2 出，补偿 = f(FO2 出 , ΔFH2O 出 ) Equation 7

[0243] FN2 出，补偿 = f(FN2 出 , ΔFH2O 出 ) Equation 8

[0244] The compensated additional gas fraction can then be substituted for the measured additional gas fraction in Equation 6 according to the following equation to further improve the accuracy of the post-oxygenator purge gas flow determination:

[0245]

[0246] The exact measure of can then be obtained by using Equation 5 with the value calculated according to Equation 9 to calculate.

[0247] It should be noted that, although described herein as techniques for controlling CO2 removal from a patient's blood stream, the techniques of the first and second aspects of the present disclosure may also be used to control CO2 addition to a patient's blood stream via an oxygenator 21. It may sometimes be desirable to obtain or maintain a desired pH or CO2 partial pressure (PCO2) in the patient's blood 3. It should therefore be appreciated that the disclosed method for controlling CO2 removal in an ECMO device 5 may be generalized to a method for controlling CO2 transfer from a patient's blood stream 3 via an oxygenator 21 in order to control CO2 addition or removal from the patient's blood. The purpose of controlling CO2 transfer may be any of the following: 1) ensuring adequate removal of CO2 from the patient's blood; 2) maintaining CO2 removal constant, for example, in order to assess ongoing respiratory therapy provided by the mechanical ventilator 7 and / or lung function of the patient 3; and 3) obtaining or maintaining a set or desired post-oxygenator pH and / or PCO2, particularly during regulation of purge gas flow.

[0248] In applications where the transfer of CO2 across the oxygenator membrane 23 is controlled to achieve or maintain a set or desired post-oxygenator pH and / or PCO2, the control computer 27 of the ECMO device 5 can be configured to automatically control the inlet purge gas flow rate and / or CO2 addition to the inlet purge gas flow to achieve or maintain pH and / or PCO2.

Claims

1. A method for controlling the removal of carbon dioxide [CO2] in an apparatus (5) for extracorporeal blood gas exchange, wherein: The device (5) comprises an oxygenator (21) comprising a membrane (23) acting as a gas-liquid barrier, the membrane (23) enabling CO2 to be transferred between a blood flow and a purge gas flow passing through the oxygenator, the method comprising the following steps: - measuring (S12a) the pre-oxygenator CO2 fraction [FCO2 入 ], - measuring (S12b) a pre-oxygenator purge gas flow rate of the purge gas flow upstream of the oxygenator (21) - measuring (S12c) the post-oxygenator CO2 fraction [FCO2 出 ], - measuring (S12d) a post-oxygenator purge gas flow rate of the purge gas flow downstream of the oxygenator (21) and - Based on measured FCO2 入 , FCO2 出 and To calculate (S12e) the net CO2 exchange on the membrane (23) 2. The method according to claim 1, further comprising the steps of: - adding (S11) CO2 to the purge gas flow upstream of the oxygenator (21) to control the degree of CO2 removal from the blood flow by the oxygenator (21), and -Use(S13) As a measure of CO2 removal, CO2 addition is used to adjust the purge gas stream.

3. The method according to claim 2, wherein: The step of using the CO2 removal measure to adjust the CO2 addition of the purge gas stream comprises: - presenting (S13a) the CO2 removal measure to an operator of the device (5) as a decision support for manually adjusting the CO2 addition of the purge gas flow, and / or - presenting (S13b) to the operator a recommendation for adjusting CO2 addition to the purge gas flow based on the CO2 removal measure and the set target for CO2 removal by the oxygenator, and / or - Automatically adjusting (S13c) CO2 addition of said purge gas stream based on said CO2 removal measure.

4. The method according to any one of the preceding claims, comprising the steps of: - measuring or estimating a pre-oxygenator at least one additional gas fraction in the purge gas flow upstream of the oxygenator (21), the at least one additional gas being one or more of water vapor (H2O), oxygen (O2), nitrogen (N2) and an anesthetic agent, and / or - measuring or estimating a post-oxygenator at least one additional gas fraction in the purge gas flow downstream of the oxygenator (21), and -based on FCO2 入 and the pre-oxygenator at least one additional gas fraction to calculate the compensated pre-oxygenator purge flow and / or -based on FCO2 出 and the post-oxygenator at least one additional gas fraction to calculate a compensated post-oxygenator purge flow and -based on and At least one of 5. The method according to any one of the preceding claims, comprising the steps of: -Based on FCO2 入 and in The measuring point (P1) and FCO2 入 The estimated water vapor addition or removal [ΔFH2O 入 ] to calculate the compensated pre-oxygenator CO2 fraction [FCO2 入，补偿 ], the compensated pre-oxygenator CO2 fraction [FCO2 入，补偿 ]Representative an estimate of the CO2 fraction at said measurement point (P1), and / or -Based on FCO2 出 and in The measuring point (P3) and FCO2 出 The estimated water vapor addition or removal (ΔFH2O) of the purge gas between the measurement points (P4) 出 ) to calculate the compensated post-oxygenator CO2 fraction [FCO2 出，补偿 ], the compensated post-oxygenator CO2 fraction [FCO2 出，补偿 ]Representative an estimate of the CO2 fraction at said measurement point (P3), and -Based on FCO2 入，补偿 and FCO2 出，补偿 At least one of 6. The method according to claims 4 and 5, wherein: Based on FCO2 入，补偿 and at least one additional gas fraction before the oxygenator to calculate and / or based on FCO2 出，补偿 and the post-oxygenator at least one additional gas fraction to calculate 7. The method according to claim 2, further comprising the steps of: - receiving a target value for said CO2 removal measure, and - Automatically regulating CO2 addition of said purge gas flow in order to reach and / or maintain said target value for said CO2 removal measure.

8. The method according to claim 7, wherein: The device (5) is connected to a patient (3), which is also connected to a mechanical ventilator (7) for mechanically ventilating the patient by supplying breathing gas to the patient's lungs, and wherein the target value is selected to evaluate the ventilation therapy provided by the mechanical ventilator (7) and / or the patient's lung function, for example by selecting a target value corresponding to zero or near-zero CO2 removal.

9. A method according to any one of the preceding claims, wherein: Measuring (S12d) the post-oxygenator purge gas flow rate The step of measuring the flow rate of the entire purge gas effluent stream leaving the oxygenator (21) is performed.

10. The method according to claim 9, wherein: The oxygenator (21) comprises more than one purge gas outlet, the method comprising the steps of preventing the purge gas from passing through all outlets of the oxygenator (21) except one outlet, and measuring the post-oxygenator purge gas flow as the flow rate of the purge gas flowing through the one outlet.

11. A computer program for controlling the removal of carbon dioxide [CO2] in an apparatus (5) for extracorporeal blood gas exchange, wherein: The apparatus (5) comprises an oxygenator (21) comprising a membrane (23) acting as a gas-liquid barrier, the membrane (23) enabling CO2 to be transferred between a blood flow and a purge gas flow through the oxygenator, the computer program comprising computer readable instructions which, when executed by a control computer (27), cause a method according to any one of the preceding claims to be performed.

12. A computer program product comprising a non-transitory storage hardware device (39) storing a computer program for controlling the removal of carbon dioxide [CO2] in an apparatus (5) for extracorporeal blood gas exchange, wherein: The apparatus (5) comprises an oxygenator (21) comprising a membrane (23) acting as a gas-liquid barrier, the membrane (23) enabling CO2 to be transferred between a blood flow and a purge gas flow through the oxygenator, the computer program comprising computer readable instructions which, when executed by a control computer (27), cause the method according to any one of claims 1 to 10 to be performed.

13. A system (1) for controlling the removal of carbon dioxide [CO2] in an apparatus (5) for extracorporeal blood gas exchange, wherein: The device (5) comprises an oxygenator (21) comprising a membrane (23) acting as a gas-liquid barrier, the membrane (23) enabling CO2 to be transferred between a blood flow through the oxygenator and a purge gas flow, and at least one control computer (27) configured to: - receiving a pre-oxygenator CO2 fraction [FCO2 入 ], - a pre-oxygenator purge gas flow rate receiving the purge gas flow upstream of the oxygenator (21) The measured value of - receiving a post-oxygenator CO2 fraction [FCO2 出 ], - a post-oxygenator purge gas flow rate receiving the purge gas flow downstream of the oxygenator (21) The measured value of - Based on measured FCO2 入 , FCO2 出 and To calculate the net CO2 exchange on the membrane (23) 14. The system (1) according to claim 13, further comprising a gas regulator (25) for adding CO2 to the purge gas flow upstream of the oxygenator (21) so as to control the degree of CO2 removal of the blood flow by the oxygenator (21), wherein The control computer (25) is configured to utilize The CO 2 addition to the purge gas stream is controlled as a measure of CO 2 removal.

15. The system (1) according to claim 14, wherein: The control computer (25) is configured to utilize the CO2 removal measure to regulate the CO2 addition of the purge gas stream by: - presenting a CO2 removal measure to an operator of the device (5) as a decision support for manually adjusting the CO2 addition of the purge gas flow, and / or - presenting a recommendation to an operator of the device (5) for adjusting the CO2 addition to the purge gas flow based on the CO2 removal measure and the set target for CO2 removal by the oxygenator, and / or - Automatically adjust CO2 addition of the purge gas stream based on CO2 removal measurements.

16. System (1) according to any one of claims 13 to 15, wherein: The control computer (25) is configured to: - estimating or receiving a measured value of a pre-oxygenator fraction of at least one additional gas in the purge gas flow upstream of the oxygenator (21), the at least one additional gas being one or more of water vapor (H2O), oxygen (O2), nitrogen (N2) and an anesthetic agent, and / or - estimating or receiving a measured value of the fraction of at least one additional gas post-oxygenator in the purge gas flow downstream of the oxygenator (21), and -based on FCO2 入 and the pre-oxygenator at least one additional gas fraction to calculate the compensated pre-oxygenator purge flow and / or -based on FCO2 出 and the post-oxygenator at least one additional gas fraction to calculate a compensated post-oxygenator purge flow and -based on and At least one of the following is used to calculate (S2'i) VCO2 净 .

17. System (1) according to any one of claims 13 to 16, wherein: The control computer (25) is configured to: -Based on FCO2 入 and in The measuring point (P1) and FCO2 入 The estimated water vapor addition or removal [ΔFH2O] of the purge gas between the measurement points (P2) 入 ] to calculate the compensated pre-oxygenator CO2 fraction [FCO2 入，补偿 ], the compensated pre-oxygenator CO2 fraction [FCO2 入，补偿 ]Representative an estimate of the CO2 fraction at said measurement point (P1), and / or -Based on FCO2 出 and in The measuring point (P3) and FCO2 出 The estimated water vapor addition or removal [ΔFH2O] of the purge gas between the measurement points (P4) 出 ] to calculate the compensated post-oxygenator CO2 fraction [FCO2 出，补偿 ], the compensated post-oxygenator CO2 fraction [FCO2 出，补偿 ]Representative an estimate of the CO2 fraction at said measurement point (P3), and -Based on FCO2 入，补偿 and FCO2 出，补偿 At least one of 18. System (1) according to claims 16 and 17, wherein: Based on FCO2 入，补偿 and at least one additional gas fraction of the pre-oxygenator, and / or Based on FCO2 出 and at least one additional gas fraction after the oxygenator is calculated.

19. The system (1) according to claim 14, wherein: The control computer (25) is configured to: - receiving a target value for a CO2 removal measure, and - regulating CO2 addition of said purge gas stream to reach and / or maintain said target value for said CO2 removal measure.

20. The system (1) according to claim 19, wherein: The device (5) is connected to a patient (3), which is also connected to a mechanical ventilator (7) for mechanically ventilating the patient by supplying breathing gas to the patient's lungs, and wherein the target value is selected to evaluate the ventilation therapy provided by the mechanical ventilator (7) and / or the lung function of the patient (3), for example by selecting a target value corresponding to zero or near-zero CO2 removal.

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