Device and method for gas exchange between a first exchange medium and a second gaseous exchange medium

Abstract

The invention relates to a method and a device for gas exchange between two exchange media, comprising: an exchange chamber (1) located in a housing of an exchange unit, which exchange chamber is subdivided into two chamber regions by at least one membrane (2), wherein: in the first chamber region a first side of the membrane (2) can be brought in contact with the first exchange medium and in the second chamber region a second side of the membrane (2) can be brought in contact with the second gaseous exchange medium; the first chamber region has ports for the first exchange medium, thereby connecting the first chamber region to a first line path (3) by means of which the first exchange medium can be conducted through the first chamber region; the second chamber region has ports for the second gaseous exchange medium, thereby connecting the second chamber region to a second line path (4) by means of which the second exchange medium can be conducted through the second chamber region; gas to be exchanged can be transferred over the membrane (2) by diffusion; and the device further comprises a pressure generating unit (9a) by means of which a pressure difference between the second exchange medium and the surrounding ambient pressure can be generated in the second chamber region, the pressure difference being in the order of at least 10 mmHg, and the at least one membrane (2) being permeable to the gas to be exchanged with respect to diffusion and being impermeable with respect to convection.

Description

[0001] Device and method for gas exchange between a first exchange medium and a second gaseous exchange medium

[0002] The invention relates to a device for gas exchange between a first exchange medium and a second gaseous exchange medium, comprising an exchanger unit with an exchange chamber arranged in a housing of the exchanger unit, wherein the exchange chamber is divided by at least one membrane, preferably by a plurality of hollow fiber membranes, into a first chamber region, in which a first side of the at least one membrane can be contacted with the first exchange medium, and is divided into a second chamber region, in which a second side of the at least one membrane can be contacted with the second gaseous exchange medium, and wherein the first chamber region has inlet and outlet connections for the first exchange medium, by means of which the first chamber region is integrated into a first line path, with which the first

[0003] Exchange medium can be guided through the first chamber region, and wherein the second chamber region has inlet and outlet connections for the second gaseous exchange medium, through which the second chamber region is integrated into a second line path with which the second exchange medium can be guided through the second chamber region, and wherein a gas to be exchanged present in one of the two exchange media can be transferred across the membrane into the other exchange medium by diffusion.

[0004] The invention also relates to a method for gas exchange between a first exchange medium, in particular excluding blood, and a second gaseous exchange medium, with an exchanger unit having an exchange chamber arranged in a housing of the exchanger unit, wherein the exchange chamber is divided by at least one membrane, preferably by a plurality of hollow-fiber membranes, into a first chamber region, in which a first side of the at least one membrane is in contact with the first exchange medium, and into a second chamber region, in which a second side of the at least one membrane is in contact with the second gaseous exchange medium, and wherein the first chamber region has inlet and outlet connections for the first exchange medium, through which the first chamber region is integrated into a first line path, with which the first exchange medium is guided through the first chamber region,and wherein the second chamber region has inlet and outlet connections for the second gaseous exchange medium, through which the second chamber region is integrated into a second conduit path by which the second exchange medium is guided through the second chamber region, and wherein a gas to be exchanged present in one of the two exchange media is transferred across the at least one membrane into the other exchange medium by diffusion.

[0005] Such devices are also referred to as membrane contactors and are primarily used to enrich or deplete at least one specific gas in an exchange medium on one side or the other of the exchange chamber. In a known manner and also in the invention, the first exchange medium can be a liquid or gaseous medium, and the second exchange medium can be a gaseous one.

[0006] In the medical field, such devices serve, for example, as so-called oxygenators to enrich blood with oxygen and simultaneously deplete it of carbon dioxide. The invention preferably also relates to precisely this application, in particular to a so-called oxygenator as the exchanger unit according to the invention, but is not limited thereto. A preferred embodiment also relates to a device for eliminating carbon monoxide from blood or to a device and a method for concentrating a gas component in one of the two exchange media, in particular in one of two gaseous exchange media.

[0007] In the prior art, as well as in the invention, the subdivision of the exchange chamber by the at least one membrane is preferably achieved in that the at least one membrane is sealed at its end regions to the housing wall of the exchange chamber. Preferably, several membranes are provided, in particular those designed as hollow-fiber membranes that are sealed at their axial end regions to the housing wall. In particular, hollow-fiber membranes are sealed with their radially outer surfaces in the end region to the housing wall and also to one another. In the technical field of such exchange units, this is also referred to as potting. A potting compound is used for potting, i.e., sealing.

[0008] To the extent that properties of the at least one membrane in the exchange chamber are described below, these properties preferably apply to all membranes used in the exchange chamber of the device. To the extent that the present device or method is described using blood as the liquid first exchange medium and oxygen / air as the gaseous second exchange medium, the same features are also deemed to be disclosed in connection with other liquid or gaseous first exchange media and a gaseous second medium.

[0009] The aforementioned first conduit path comprises, for example, a source for the first exchange medium on the inlet side of the first chamber region and a sink on the outlet side. In particular, a pump for conveying the first exchange medium through the conduit path can be provided in the first conduit path. The first conduit path can, for example, be integrated into a circuit. In an application for gas exchange with blood, a patient can be part of the conduit path, in particular the circuit, during operation of the device. The patient can thus form both the source and the sink.

[0010] The aforementioned second conduit path comprises, for example, a source for the second exchange medium (e.g., gas cylinder, gas supply) on the inlet side and a sink (e.g., atmospheric environment) on the outlet side. In particular, a pump for conveying the second exchange medium through the conduit path can be provided in the second conduit path. The second conduit path can also be integrated into a circuit, e.g., if the second exchange medium is reused after passing through the second chamber area.

[0011] In the invention, it is preferably provided that the first chamber region and the first conduction path adjoin a first side of the at least one membrane, which in the case of hollow-fiber membranes, for example, is the outside of the membranes, wherein the second chamber region and the second conduction path adjoin a second side of the at least one membrane, which in the case of hollow-fiber membranes, for example, is the inside of the membranes.

[0012] Alternatively, it is also preferably provided that the first chamber region and the first conduction path adjoin a first side of the at least one membrane, wherein in the case of hollow-fiber membranes this is, for example, the inside of the membrane, wherein the second chamber region and the second conduction path adjoin a second side of the at least one membrane, wherein in the case of hollow-fiber membranes this is, for example, the outside of the membrane.

[0013] A preferably liquid first exchange medium, e.g., blood, can thus alternatively flow around the outside of the hollow-fiber membranes or through the interior of the hollow-fiber membranes, with a preferably gaseous second exchange medium contacting the other side of the membrane. When used for gas exchange with blood, the second exchange medium during operation of the device according to the invention is preferably pure oxygen or an oxygen-containing gas, e.g., air.

[0014] In the prior art, it is known that such exchanger units may only be operated virtually without a pressure difference between the second gaseous exchange medium and the surrounding atmospheric pressure, in particular as a result of which the pressure in both chamber areas corresponds at least substantially to the usual atmospheric ambient pressure surrounding the device, because the at least one membrane, in particular typical hollow fibers that are used in oxygenators, are not impermeable to the convective passage of the exchange media, thus, for example, in the case of a pressure difference between the second exchange medium and the atmospheric pressure, not only would there be diffusion due to concentration gradients through the membrane, but in the case of a positive pressure difference, for example, gas bubbles of the gaseous second exchange medium into the other medium, e.g.Blood could pass through, or conversely, in the case of a negative pressure difference, liquid blood components, especially blood plasma, could convectively pass through the membrane into the second gaseous exchange medium. However, the transfer of gas bubbles must be avoided, especially in applications with oxygenators.

[0015] The transfer rates of gas between the exchange medium, in particular of oxygen and / or carbon dioxide or carbon monoxide in oxygenators, are therefore limited, and until now these could only be increased by increasing the membrane surface area. However, since the membrane surface area itself can also be classified as damaging to the blood, this cannot simply be increased arbitrarily, at least when the device is used as an oxygenator. It is therefore an object of the invention to provide a device and a method with which an increase in the exchange rate per unit membrane area can be achieved compared to the previous state of the art. The aim is to increase the transfer rate for the gas to be exchanged for a given membrane surface area, or to achieve a reduction in the membrane surface area for a given transfer rate.

[0016] This object is achieved according to the invention in the device in that the device according to the invention has a pressure generating device with which a pressure difference can be generated in the second chamber region, in particular via the second line path, from the second exchange medium compared to the surrounding atmospheric pressure, in particular is generated in gas exchange operation, which has an amount of at least 10 mmHg.

[0017] This object is achieved according to the invention in the method in that a pressure generating device in the second chamber region, in particular via the second line path, generates a pressure difference between the second exchange medium and the surrounding atmospheric pressure, in particular in gas exchange operation, which pressure difference has an amount of at least 10 mmHg, wherein the at least one membrane is permeable to the gas to be exchanged with respect to diffusion at the generated pressure difference and impermeable to the two exchange media with respect to convection at the generateable / generated pressure difference.

[0018] This reveals that in addition to the concentration gradient of the gas to be exchanged between the two exchange media, which exists across the membrane and causes the transition by diffusion through the membrane, a further driving potential is developed by the pressure difference, since in this way the partial pressure of the gas to be exchanged in the second chamber area in the second gaseous medium can be changed relative to the partial pressure corresponding to the concentration of this gas in the first exchange medium.

[0019] To generate the pressure difference, for example, the pressure in the second chamber region can be influenced via the second line path, preferably increased or decreased, in particular while the pressure in the first chamber region is unaffected, in particular corresponding to the atmospheric ambient pressure to which the device is exposed at the location of its use, possibly plus any hydrostatic pressure and / or back pressure due to the flow through the first chamber region. In particular, the differential pressure between the chamber regions thus preferably corresponds, during operation of the device, to the differential pressure of the second gaseous exchange medium in the second chamber region compared to the atmospheric ambient pressure, in particular, if necessary, taking into account the aforementioned pressure contributions.

[0020] Furthermore, the invention provides that the at least one membrane, in particular each hollow fiber-shaped membrane, is permeable with respect to diffusion at the pressure difference that can be generated / is generated for the gas to be exchanged and is impermeable with respect to convection at the pressure difference that can be generated / is generated for the two exchange media (in particular also their constituents).

[0021] In particular, this means that the membrane is permeable to individual molecules of the gas to be exchanged due to the concentration difference on both sides of the membrane, i.e., in the conventional sense, it is permeable to diffusion, but impermeable to gas bubbles of the gas to be exchanged or the second gaseous exchange medium. In particular, the membrane is also impermeable to the transfer of the first exchange medium as droplets or bubbles, in particular impermeable to liquid components of the first exchange medium, especially impermeable to blood plasma when using blood as the first exchange medium.

[0022] The convection-tight design of the membrane allows the aforementioned driving potential for gas exchange to be tapped, since the pressure difference additionally increases the concentration gradient on both sides of the membrane without the risk that the media itself can pass over in the form of bubbles or drops.

[0023] For this purpose, the material of the at least one membrane can, for example, be impermeable to convection, in particular to gas bubbles and / or drops, throughout the membrane thickness, or the at least one membrane has a layer on at least one of its sides or on both sides that is impermeable to convection, in particular to gas bubbles and / or drops of the exchange media.

[0024] Thus, according to the invention, the membrane or its material is impermeable to convection, in particular to the gas to be exchanged, but is permeable to diffusion, in particular is selectively more permeable to the at least one gas to be exchanged than to other possible gas components of the exchange media.

[0025] The pressure generating device can be formed, for example, by a pressurized gas source from which gas is forced through the second conduit into the second chamber region, or by a pump that pumps the gas into or out of the second chamber region via the second conduit. The pressure generating device can be formed by any technical means suitable for increasing or decreasing the pressure of the second exchange medium in the second chamber region relative to atmospheric pressure.

[0026] According to the invention, the differential pressure can thus be positive or negative, with the difference being at least 10 mmHg. The invention can preferably provide that the device is configured to variably adjust or regulate the differential pressure.

[0027] A preferred embodiment provides that the device according to the invention has at least one measuring device for measuring the actual value of at least one process parameter in at least one of the exchange media and that it has at least one control device, in particular in the second line path, with which the measured actual value of the at least one process parameter can be changed in the direction of a predetermined setpoint value of the at least one process parameter by changing the pressure of the second exchange medium in the second chamber region and / or by changing the volume flow of the second exchange medium as a manipulated variable.

[0028] In particular, it is provided that the device is configured to effect the change in the manipulated variable in such a way that a differential pressure according to the invention with a value of at least 10 mmHg is continuously present. This achieves that the setpoint is regulated or at least approximated by control while maintaining the inventive condition of the presence of the differential pressure.

[0029] A measured process parameter can be, for example, the concentration or partial pressure of the gas to be exchanged in the first and / or second exchange medium, or a value dependent thereon, e.g., the transfer rate of the gas to be exchanged. A process parameter can preferably also be the pressure of the second exchange medium in the second chamber region itself, in particular the absolute pressure or relative to atmospheric pressure, or the volume flow of the second exchange medium in the second chamber region or in the second conduit path.

[0030] Preferably, it is provided that the device is configured to adjust or approximate the process parameter of the gas to be exchanged, e.g. the concentration, in the first and / or second exchange medium or a value dependent thereon as a function of the pressure and / or the volume flow of the second exchange medium to a desired, in particular preset, setpoint value.

[0031] It is particularly preferred that, in the flow direction downstream of the outlet connection in the line path of one of the two chamber regions, at least one measuring device is provided for measuring at least one measured value representing the at least one process parameter, in particular which represents the concentration of the gas to be exchanged in the exchange medium of this chamber region or is dependent thereon, and that at least one control device is provided in the second line path of the second chamber region, with which the value of the pressure difference and / or the value of the volume flow of the second exchange medium can be changed depending on the measured value. This preferably takes place while continuously maintaining the condition according to the invention that the pressure difference has a value of at least 10 mmHg.

[0032] According to the invention, it is thus possible to regulate to a predetermined target value of the process parameter, preferably to a value representing the concentration or dependent thereon, for which purpose an actual value of the process parameter, in particular of the measured value representing the concentration, is recorded and the pressure and / or the volume flow is regulated in such a way that the predetermined target value is reached or at least approximated.

[0033] The invention provides for operating with a difference between the pressure in the second chamber region (or second line path) and the ambient atmospheric pressure that is greater than 10 mmHg in magnitude (i.e., neglecting the sign). The pressure in the exchange chamber on the side of the pressure-controlled exchange medium, in particular the second gaseous exchange medium, can therefore preferably be at least 10 mmHg greater or lesser than the ambient atmospheric pressure.

[0034] For this purpose, the invention can, for example, provide a measuring device to measure the ambient atmospheric pressure that exists around the device and to select the set or preferably regulated pressure of the second exchange medium in the second chamber region as a function of this recorded atmospheric pressure so that the difference to the atmospheric pressure provided according to the invention, in particular also between the chamber regions, is achieved and in particular continuously maintained during operation.

[0035] The invention therefore makes it possible to operate with a pressure that deviates from the atmospheric pressure by the differential pressure, in particular overpressure or negative pressure, in the second chamber region of the exchange chamber, so that the transfer rate of the at least one gas to be exchanged can be significantly increased compared to the prior art.

[0036] It is particularly preferably provided that the device is designed, in particular during operation, to set or regulate an amount of the pressure difference which is greater than 10 mmHg, preferably greater than 20 mmHg, preferably greater than 50 mmHg, more preferably greater than 100 mmHg, more preferably greater than 200 mmHg, more preferably greater than 300 mmHg, more preferably greater than 400 mmHg, more preferably greater than 500 mmHg, in particular less than 600 mmHg.

[0037] The highest value of the unsigned amount of the pressure difference is preferably provided to prevent bubble formation in blood, for example in blood applications.

[0038] In order to meet these differential value specifications, the invention preferably provides that the at least one membrane permeable to the gas to be exchanged has a layer preventing the convective passage of the exchange media on at least one of its sides, in particular on the side that contacts a liquid exchange medium, preferably on the inside (or alternatively the outside) of the at least one hollow fiber-shaped membrane, or is designed throughout as a membrane preventing the convective passage of the exchange media.Preferably, the layer or membrane is designed such that it can withstand, without destruction, an amount of pressure difference which is greater than 10 mmHg, preferably greater than 20 mmHg, preferably greater than 50 mmHg, more preferably greater than 100 mmHg, more preferably greater than 200 mmHg, more preferably greater than 300 mmHg, more preferably greater than 400 mmHg, more preferably greater than 500 mmHg, but in particular less than 700 mmHg, preferably less than 600 mmHg.

[0039] This can preferably be achieved, for example, in that the at least one aforementioned layer is formed from a non-porous, in particular non-porous porous material, preferably silicone, which allows the diffusion of the gas to be exchanged, or the at least one membrane is formed entirely from a non-porous, in particular non-porous porous material, preferably silicone, which allows the diffusion of the gas to be exchanged.

[0040] For the formation of a layer of silicone, it is preferred that the at least one membrane comprises a porous carrier element, in particular a porous hollow fiber, which has a layer of silicone on at least one of its sides, preferably which has a minimum thickness of 2 micrometers, more preferably 3 micrometers, more preferably 5 micrometers.

[0041] Such a layer can be formed by depositing the silicone, for example, on the inner or outer surface of the membrane and / or from there into the porous structure of the membrane. The layer can be formed from portions of silicone located in the pores or on the surface. Overall, across both portions, it is preferred that the minimum thickness be 2 micrometers, more preferably 3 micrometers, and more preferably 5 micrometers.

[0042] Particularly preferably, the layer is formed entirely within the pores, starting from the inner or outer surface, without the surface itself being coated with silicone. This creates a particularly stable silicone layer because the pore structure has a stabilizing effect.

[0043] Silicone is a particularly advantageous material here because it offers high diffusion permeability, especially for oxygen and / or carbon dioxide. However, with the pore-free layer, which is preferably provided here, it does not allow convective passage of either exchange medium. Alternatively, polyurethane, for example, can be used instead of silicone.

[0044] All embodiments mentioned in this description of the invention in which silicone is mentioned can alternatively also be formed with other suitable coating agents, e.g. polyurethane.

[0045] A hollow-fiber membrane, for example, can be used as a porous, particularly open-pore, support element. This membrane is otherwise used in conventional atmospheric-pressure applications for the purpose of gas exchange between two media, e.g., in oxygenators or dialyzers. These can be hollow-fiber membranes made of the following materials: polysulfone, polypropylene, or polymethylpentene.

[0046] The application of silicone or another suitable material to / in a porous, particularly open-pored, support element can be achieved, for example, by dissolving the corresponding material, preferably silicone, in a solvent or diluting it with it and then impregnating the support element with this solution, after which the solvent evaporates and the material remains in the pores and / or on the inner / outer surface, particularly depending on the post-treatment. When using silicone as a coating agent, it can preferably be dissolved in, for example, n-heptane. Polyurethane as a coating agent can preferably be dissolved in dimethylformamide.

[0047] Hollow fiber membranes equipped accordingly, in particular those made of the aforementioned materials, can thus be made suitable for the device according to the invention by subsequently providing them with an impermeable layer made of the suitable material, in particular silicone.

[0048] A preferred embodiment of the device provides that the at least one control device for controlling the pressure and / or the volume flow and the at least one measuring device for measuring the at least one process parameter, in particular its actual value, are arranged in the line paths of different chamber regions, in particular wherein the device is set up to have a liquid exchange medium as the first exchange medium in the first chamber region connected to the measuring device, preferably to the outlet-side measuring device, during operation and the control device is arranged in the line path of the second chamber region, preferably arranged on the outlet side, which is set up to have the gaseous second exchange medium during operation of the device.It is preferably provided that the control device is designed to regulate an overpressure in the second chamber region relative to the atmospheric pressure, in particular also relative to the first chamber region.

[0049] In such an embodiment, it is preferably provided that the device is configured for operation for enriching oxygen or depleting carbon monoxide in blood as the first exchange medium. For this purpose, the measuring device is designed, for example, to measure the oxygen concentration, in particular the oxygen partial pressure, or the carbon monoxide concentration, in particular the carbon monoxide partial pressure, in blood and is arranged in the conduit path downstream of the outlet connection of the first chamber region provided for the blood flow. Preferably, this chamber region adjoins the inner surfaces of a plurality of hollow-fiber membranes.

[0050] Alternatively, it can also be provided that the at least one control device and the at least one measuring device for the at least one process parameter are arranged in the same line path, in particular in the line path of the second chamber region, which is set up to have the gaseous second exchange medium during operation of the device, preferably, wherein the device is set up to have a liquid exchange medium in the chamber region which has the first exchange medium during operation, further preferably, wherein the control device is set up to regulate a negative pressure in the second chamber region relative to atmospheric pressure.

[0051] Preferably, the device in this embodiment is designed for operation for the depletion of carbon dioxide in blood as the first exchange medium, for which purpose the at least one measuring device is designed to measure the concentration of carbon dioxide, in particular the carbon dioxide partial pressure in the gaseous second exchange medium and is preferably arranged in the line path after the outlet connection of the chamber region provided for the guidance of the gaseous second exchange medium, in particular the chamber region which borders the outer surfaces of a plurality of hollow fiber-shaped membranes.

[0052] When regulating a negative pressure in the second chamber region relative to atmospheric pressure, it is preferably provided that the pressure-regulating element of the at least one control device, e.g. a throttle valve, is arranged on the outlet side of the chamber region in the pressure-regulated line path, and when regulating an overpressure in the second chamber region relative to atmospheric pressure, it is preferably provided that the pressure-regulating element of the at least one control device, e.g. a throttle valve, is arranged on the inlet side of the chamber region in the pressure-regulated line path.

[0053] Preferably, the device is further configured such that, by regulating the pressure, a predetermined target partial pressure of the gas to be exchanged or a target value dependent on the partial pressure of the gas to be exchanged, in particular as the aforementioned process parameter, can be adjusted with the at least one control device. The target partial pressure is a value that represents the concentration of the gas to be exchanged, as is a value dependent on it. The target value to be adjusted can also be, for example, the transfer rate of the gas to be exchanged.

[0054] A preferred development of the invention provides that the volume flow of the exchange medium in the second line path can be changed with the control device as a function of the measured value of the process parameter, in particular the concentration, and as a further function of the amount of the pressure difference, wherein the at least one control device is designed to increase the volume flow when a limit value of the pressure difference is exceeded, in particular while subsequently keeping the pressure difference constant.

[0055] It is therefore possible, for example, to increase the transfer rate of the gas to be exchanged by increasing the volume flow if the amount of pressure difference cannot be increased any further, e.g. because otherwise the membrane or the membrane layer would be destroyed.

[0056] In general, particularly in this aforementioned embodiment, with the at least one control device, a change in the volume flow is subordinate to a change in the pressure in order to regulate or approximate the process parameter and is only carried out when a change in the pressure is no longer possible, in particular if a limit value of the pressure difference would otherwise be exceeded. Alternatively, an embodiment is generally possible in which with the at least one control device, a change in the pressure is subordinate to a change in the volume flow in order to regulate or approximate the process parameter and is preferably only carried out when a change in the volume flow is no longer possible or would otherwise exceed a predetermined limit value.

[0057] With the at least one control device, in all possible embodiments, only a pressure change or alternatively only a volume flow change or alternatively both can be carried out, in particular one after the other, in particular in the two possible alternatives of the sequence.

[0058] However, the invention can also provide for a control device for controlling the pressure as a function of a first process parameter and a control device for controlling the volume flow as a function of a second process parameter to be operated in parallel, i.e., simultaneously. For example, in pressure control, the concentration of oxygen in the blood or gas can be measured on the output side as a process parameter, and in volume flow control, the concentration of carbon dioxide in the blood or gas can be measured on the output side as a process parameter. Both control systems operate subject to the condition that a pressure difference of the type described in the invention exists.

[0059] Further preferably, the axial length of a plurality of hollow-fiber membranes in the exchange chamber may be greater than the length of the chamber in the direction of the spacing of the ends of the hollow-fiber membranes. As a result, the hollow fibers are not extended in a straight line, but rather bulged, allowing the medium flowing around them, e.g., the gas, to flow more easily around them.

[0060] A further development also preferably provides that the conduit path through the chamber region, which carries a liquid exchange medium, in particular blood, during operation, preferably through the interior of hollow-fiber membranes, comprises a pulsation device with which recurring, in particular periodic, pressure fluctuations can be generated in the liquid exchange medium. This has the advantage that the thickness of the blood plasma seam on the inside of hollow fibers can be reduced.

[0061] The invention can also provide a combination of at least two devices of the previously described embodiments connected in series or in parallel in the flow direction of a preferably liquid exchange medium, wherein at least one device is operated with a positive pressure difference and at least one device is operated with a negative pressure difference compared to atmospheric pressure or one device is operated with a pressure difference and the other without a pressure difference.

[0062] In particular, with such a combination it can be provided that the at least two devices are operated with different flow ratios GBV of gas and blood, wherein the gas-blood ratio GBV is defined as GBV = gas flow / blood flow. Preferably, the gas-blood ratio GBV in a device that operates with negative differential pressure, in particular a device for CO2 elimination, is greater than the gas-blood ratio of a device that operates with a positive pressure difference, in particular a device for oxygen enrichment. Preferably, a device for CO2 elimination is operated with a GBV>1, e.g. 1 to 15, and a device for oxygen enrichment is operated with a GBV<1.

[0063] Embodiments of the invention are described below:

[0064] Figure 1 schematically shows a device according to the invention for gas exchange between a first exchange medium, here blood, and a second gaseous exchange medium, here pure oxygen or an oxygen-containing gas, comprising an exchanger unit with an exchange chamber 1 arranged in a housing of the exchanger unit and having membranes 2 designed as hollow fibers, which divide the exchange chamber 1 into two chamber regions. The first chamber region comprises the interior of the hollow fibers 2, and the second chamber region is located outside around them. Accordingly, blood flows through the first chamber region and through the hollow-fiber membranes 2, and gas flows through the second chamber region and outside around the membranes.

[0065] Both chamber areas are connected to conduits 3, 4. The first conduit 3 carries the blood, the second conduit 4 the gas. Both conduits 3, 4 have inlets and outlets at the respective chamber areas. At least the blood circulates between a patient (not shown here) and the device shown. The gas flows from a pressure-generating device 9a, e.g., a gas source, through the device to a gas sink 9b, e.g., to the environment. A circuit can also be formed here, for example, if the used gas is recovered.

[0066] Here, as in the other exemplary embodiments, a respective membrane 2 is designed, for example, as shown in Figure 2A or 2B. The membrane 2 has an open-pore, porous support element, for example formed from a porous hollow fiber, in particular from the prior art, for example from polysulfone, polypropylene, or polymethylpentene, and is provided on the inside in Figure 2A and on the outside in Figure 2B with a layer 2a of silicone, here, for example, with a thickness of approximately 7.5 micrometers.

[0067] Such a coated hollow fiber 2 is permeable to diffusion, for example, oxygen and carbon dioxide, but does not allow any gas bubbles or liquid components of the first exchange medium to pass through the membrane thickness through convection, thus being convection-tight, even if the gas is present at an excess pressure compared to the first chamber region or the atmospheric pressure at the location of the device in the second chamber region or second conduit path that carries the gas. This tightness is only created by the silicone layer or layer of alternative suitable materials. The porous carrier element, on the other hand, would be convective.

[0068] Convection of both exchange media in the presence of a differential pressure of the second exchange medium compared to the atmospheric pressure or in the two chamber areas may not be tight, e.g. gas bubbles may pass through.

[0069] The silicone layer 2a can be provided on the inside or outside as shown in Figures 2A and 2B, or the hollow fiber 2 is made entirely of silicone, in particular pore-free silicone or another suitable convection-tight material.

[0070] It is essential for the invention that at least one measuring device 5 is provided in the blood line 3 after the blood outlet, with which a value can be measured that represents a process parameter.

[0071] According to Figure 1, a first measuring device 5a is provided, for example, for measuring the oxygen concentration in the blood as the first measured value, e.g., for measuring the O2 saturation or the O2 partial pressure. Furthermore, a second measuring device 5b is provided for measuring the carbon dioxide concentration in the blood as the second measured value, e.g., for measuring the CO2 concentration or the CO2 partial pressure.

[0072] It can also be provided that - contrary to what is shown - only one of the two measuring devices mentioned is formed.

[0073] The first measured value is compared as an actual value in a control device 6a with a setpoint value of the process parameter, e.g. the oxygen concentration, e.g. with the setpoint oxygen partial pressure, and in order to achieve the setpoint value by the control device 6a, a gas pressure regulator 7 of the control device 6a in the second line path 4 at the gas outlet of the second chamber area is controlled, which can be designed as a throttle valve, e.g. The control device 6a in the second line path is thus formed at least by the gas pressure regulator 7. The valve position of the throttle valve can here form the manipulated variable of the control device 6a. The second measured value is compared as an actual value in a control device 6b with a setpoint value of the process parameter, e.g. the carbon dioxide concentration, e.g.compared with the target carbon dioxide partial pressure, and to achieve the target value, a gas flow regulator 8 of the control device 6b in the second line path 4 at the gas inlet of the second chamber area is controlled by the control device 6b, which can be designed, for example, as a throttle valve. The control device 6b in the second line path is thus formed at least by the gas flow regulator 8. The valve position of the throttle valve can here form the manipulated variable of the control device 6b.

[0074] The gas source 9a, e.g., a gas cylinder or pump, is arranged at the gas inlet, whereby the pressure generating device is formed in the second line path 4. By more or less severely throttling the gas outflow on the gas outlet side and / or gas inlet side, the pressure and / or volume flow of the gas, i.e., of the second exchange medium in the second chamber region, is influenced, wherein the pressure is set with a differential pressure, e.g., according to the invention, at least 10 mmHg higher. The control device is thus preferably also part of the pressure generating device, with which the pressure in the second exchange medium and / or the flow of the second exchange medium is generated.

[0075] Figure 3 shows the effect of the invention with regard to the pressure that can be changed by the control device.

[0076] In this example, normal ambient air with an oxygen content of approximately 20.8 percent is used as the second exchange medium. The atmospheric pressure is determined to be 760 mmHg, e.g., by measurement.

[0077] The diagram shows that with increasing overpressure, the oxygen partial pressure, as a measure of the oxygen concentration in the gas phase, increases significantly, e.g., from 158 mmHg at atmospheric pressure to 366 mmHg at an overpressure of 1000 mmHg. By measuring a process parameter, such as the oxygen concentration, at the blood outlet, it is possible to select or adjust a desired value of the process parameter, e.g., a desired concentration value, by changing the pressure difference, which is positive in magnitude.

[0078] Figure 4 additionally illustrates the effect of the invention at different blood flow rates.

[0079] The left side of Figure 4 shows the oxygen transfer rate (OTR) and the right side the carbon dioxide transfer rate (CTR), each plotted against the blood flow rate. The pressure of the second exchange medium, in this case oxygen or the oxygen-containing gas, is +300 mmHg relative to the atmosphere. It can be seen that at all blood flow rates, the oxygen transfer rate is higher at overpressure than at atmospheric pressure.

[0080] Although, as shown on the right in Figure 4, the transfer rate of carbon dioxide under this overpressure condition is lower than at normal pressure, this can be compensated by a higher gas flow, as illustrated, for example, by the design of Figure 1.

[0081] In this application of oxygen enrichment of blood according to the device of Figure 1, the measuring devices for measuring the process parameter, e.g. the oxygen concentration and / or the carbon dioxide concentration, and the control devices, here the gas pressure regulator 7 or the gas flow regulator 8, are arranged in different line paths, both in the respective line path on the output side of the respective chamber area.

[0082] Figure 1 shows—as previously described—a preferred development of the invention, in which a second control device in the line path 4 for guiding the second gaseous exchange medium has a gas flow regulator 8, here on the inlet side of the second chamber region, wherein a second process parameter is measured. This allows a controllable influence to be exerted on the volume flow of the second exchange medium. This can be done independently of the differential pressure control, in particular in parallel with it in time, depending on a second process parameter, but in particular also while maintaining a predetermined, in particular maximum, differential pressure when measuring only one process parameter.

[0083] This also provides the further possibility, particularly if the differential pressure cannot be increased any further to achieve the setpoint of the only process parameter, e.g., the carbon dioxide concentration or oxygen concentration, of further increasing the concentration by downstream or sole control of the gas volume flow. For example, it can be provided that upon reaching a maximum pressure differential or after setting a desired pressure differential, which does not necessarily correspond to the maximum, this pressure differential is not increased any further or is kept constant, and a volume flow change is made to adjust or approximate the setpoint.

[0084] The invention can also provide for only a volume flow control at an existing, in particular constant, differential pressure of at least 10 mmHg compared to atmospheric pressure.

[0085] Figure 5 shows a possible development of the arrangement according to Figure 1 in which the device, e.g. according to Figure 1, is followed by a vacuum unit in the blood line 3 after the blood outlet, in which vacuum unit the blood line 3 borders on a porous flat membrane, in which on the side facing away from the blood there is a vacuum chamber which is regulated by a vacuum regulator with a negative pressure compared to atmospheric pressure depending on the measured value of a bubble detector which determines whether and how many bubbles are present in the blood. If, contrary to expectations, bubbles are present in the blood after the blood outlet of the exchange chamber 1, these would be eliminated through the flat membrane and the negative pressure required for this would be automatically regulated.

[0086] Figure 6 shows another alternative of the device according to the invention. In this embodiment, the lines through the exchange chamber are configured as in Figure 1, but in the exemplary application for the elimination of CO2 from the blood, a differential pressure is used that is negative compared to atmospheric pressure, thus operating with a negative pressure in the second chamber region.

[0087] The measuring device 5b and the pressure control device 7 are both implemented in the same line, namely the line 4 for the gaseous exchange medium, in this case, e.g., oxygen or an oxygen-containing gas. The measuring device 5 is arranged on the outlet side of the second chamber area. The concentration of CO2 is measured as the partial pressure in the gas after leaving the second chamber area.

[0088] Alternatively, the concentration in blood could be measured at the exit of the first chamber area.

[0089] Negative pressure is generated by a vacuum pump pumping the second exchange medium from the second chamber area, which is supplied thereto by the gas source 9a. The vacuum pump forms a gas sink and the pressure generation device with which the pressure difference can be generated. The pressure can be regulated, for example, by controlling the power of the vacuum pump or by controlling a pressure regulator, e.g., throttle valve 7, in particular on the inlet side of the second chamber area, depending on the process parameter, such as the measured concentration value. The pressure regulator 7, in turn, is part of the pressure generation device and influences the pressure generated thereby.

[0090] Here, too, the volume flow of the gas can be changed additionally in parallel / following / leading or even solely with the flow controller 8, e.g. if the differential pressure cannot be reduced any further or if two different process parameters are to be controlled as in Figure 1.

[0091] In particular, the device is designed to keep the differential pressure constant when the volume flow changes. It is also possible to regulate only the volume flow of the second exchange medium at a constant differential pressure, which has the inventive differential of at least 10 mmHg compared to atmospheric pressure.

[0092] Figure 7 shows a modification of the embodiment of Figure 6 in that the concentration of carbon dioxide in the blood is measured with a measuring device at the blood outlet of the first chamber area and the negative pressure unit is controlled depending on this value in order to achieve a desired target value in the blood by changing the differential pressure, here also a negative pressure compared to the atmospheric pressure.

[0093] It is also possible to eliminate the absorbed CO2 from the gas flowing through the second chamber area, e.g. by using absorbers and using the gas in the circuit, i.e. sending it through the device again. Oxygen can also be added to the circuit, e.g. if this oxygen has been taken from the gas circuit by enrichment in the blood. For this purpose, the oxygen concentration in the blood can be measured at the blood outlet of the first chamber area and regulated by adding more oxygen. Figure 8 illustrates the effects of changing the gas flow, which are particularly significant when used for CCh elimination. Figure 4 on the right shows that although an increase in pressure increases the CH transfer rate, the CCh transfer rate decreases.

[0094] Figure 8 shows that when using a negative pressure, i.e. a negative pressure difference according to the invention, with increasing gas flow rate the transfer rate of CO2 increases significantly, especially with constant blood flow of, for example, 0.35 liters / min.

[0095] For a gas flow of 0.7 L / min, the increase in the transfer rate for CO2 at various pressure differences of -10, -100, -300 and -500 mmHg compared to atmospheric pressure is also shown for this constant value. It can therefore be seen that in negative pressure operation, e.g. for CO2 elimination, both a change in the pressure difference towards an increasing negative pressure difference and an increase in the gas flow rate lead to an increase in the transfer rate of carbon dioxide. Each of the two increase mechanisms can therefore be used alone or both in combination to increase the transfer rate, preferably whereby in both cases the transfer rate is regulated to a setpoint value as a value dependent on the CO2 concentration by changing a manipulated variable to influence the pressure difference and / or the volume flow.

[0096] Figure 9 shows an embodiment essentially as in Figure 6, but here the CO2 transfer rate is calculated as a process parameter.

[0097] Figure 10 shows a further embodiment variant in which, depending on the target concentration of CO2 in the blood, measured as partial pressure, with an existing pressure difference which represents a negative pressure compared to atmospheric pressure, the device is set up such that the volume flow of the second gaseous exchange medium, here oxygen or an oxygen-containing gas, is first changed, in particular increased, in order to achieve the target value. This control is preferably carried out up to a predetermined flow ratio of blood:gas of, for example, 1:15, wherein once the predetermined flow ratio is reached, the gas pressure is reduced, in particular wherein the amount of the differential pressure to the atmosphere in the negative pressure application is increased in order to achieve the target concentration value.

[0098] Figure 11 shows an embodiment in which a negative pressure is generated in the second chamber region using a vacuum pump as the pressure generating device. When the negative pressure exists, the volume flow is changed by the control device in the form of at least one gas flow regulator in the second line path to obtain a predetermined flow ratio of blood:gas or gas:blood as a process parameter. For this purpose, a measured value for the blood flow is preferably recorded in order to relate it to a measured value for the gas flow.

[0099] Figure 12A shows a combination of two exchange devices, which are preferably connected here by a vacuum unit, with which any gas bubbles can be eliminated, as described for Figure 1. The vacuum unit comprises a common blood outlet for both devices, which have separate blood inlets. At least one of the devices, which is operated with a pressure difference, in this case an overpressure, is designed according to the invention. The other can be designed according to the prior art, e.g., according to the preamble of claim 1.

[0100] Figure 12B shows an embodiment in which two devices according to the invention are connected in series, e.g. here by connecting them one after the other in the direction of blood flow, wherein both devices have a radial gas flow.

[0101] In the first device in the direction of blood flow (here, the lower one), CO2 elimination occurs at a higher gas flow (preferably air) when the pressure is negative compared to atmospheric pressure. In the second device in the direction of blood flow (here, the upper one), CO2 enrichment occurs at a higher gas flow (preferably air) when the pressure is positive compared to atmospheric pressure. Different hollow fiber membranes can also be used in the two devices, particularly with different diameters.

[0102] Figure 12C shows a structural alternative of two devices connected in series, with the second device arranged radially around the first and the blood flow from radially inward first through the first device and then through the second device. The devices thus have a common blood flow path, but separate gas flow paths running radially axially to the hollow fiber direction.

[0103] Here, a negative pressure is applied radially inside in the first device in the direction of blood flow to eliminate CO2 with a higher gas flow (preferably air) than in the second, radially outer device in the direction of blood flow, in which an enrichment of O2 takes place when overpressure is applied (gas phase: preferably oxygen).

[0104] In particular, the porosities of the hollow fibers in both devices are chosen differently, in particular in the first device in the direction of blood flow they are larger than in the second.

[0105] Figure 13 shows an embodiment of a device according to the invention, e.g. as described above, without the interconnection in the conduction paths, wherein the conduction path through the chamber region, which during operation carries a liquid exchange medium, in particular blood, preferably through the interior of hollow fiber membranes, comprises a pulsation device with which recurring, in particular periodic, pressure fluctuations can be generated in the liquid exchange medium, as shown in the diagram, so that the blood volume flow is not constant, which is advantageous in order to prevent the formation of a blood plasma seam on the surface of the membranes.

[0106] Figure 14 shows a supplementary variant, applicable to all possible designs, in which the axial length of a plurality of hollow-fiber membranes in the exchange chamber is greater than the length of the chamber in the direction of the spacing of the ends of the hollow-fiber membranes. This allows for better flow. Preferably, the gas flow is directed radially to the extension of the hollow fibers.

Claims

Patent claims 1 . Device for gas exchange between a first exchange medium and a second gaseous exchange medium, comprising an exchanger unit with an exchange chamber (1) arranged in a housing of the exchanger unit, a. wherein the exchange chamber (1) is divided by at least one membrane (2), preferably by a plurality of hollow fiber-shaped membranes (2), into a first chamber region in which a first side of the at least one membrane (2) can be contacted with the first exchange medium, and is divided into a second chamber region in which a second side of the at least one membrane (2) can be contacted with the second gaseous exchange medium, and b. wherein the first chamber region has inlet and outlet connections for the first exchange medium, through which the first chamber region is integrated into a first line path (3) with which the first exchange medium can be guided through the first chamber region, and c.wherein the second chamber region has inlet and outlet connections for the second gaseous exchange medium, by means of which the second chamber region is integrated into a second line path (4) with which the second exchange medium can be guided through the second chamber region, and d. wherein a gas to be exchanged present in one of the two exchange media is passed via the at least one membrane (2). into the other exchange medium by diffusion, characterized in that e. it has a pressure generating device (9a) with which a pressure difference can be generated in the second chamber region, in particular via the second line path (4), between the second exchange medium and the surrounding atmospheric pressure, in particular is generated in gas exchange operation, which pressure difference has an amount of at least 10 mmHg, wherein f. the at least one membrane (2) is permeable with respect to diffusion at the pressure difference that can be generated / is generated for the gas to be exchanged and is impermeable with respect to convection at the pressure difference that can be generated / is generated for the two exchange media.

2. Device according to claim 1, characterized in that it has at least one measuring device (5a, 5b) for measuring the actual value of at least one process parameter in at least one of the exchange media, and it has at least one control device (6a, 6b), in particular in the second line path (4), with which the measured actual value of the at least one process parameter can be changed in the direction of a predetermined target value of the at least one process parameter by changing the pressure of the second exchange medium in the second chamber region and / or the volume flow of the second exchange medium as a manipulated variable.

3. Device according to one of the preceding claims, characterized in that it is designed to determine the process parameter, in particular the concentration, of the gas to be exchanged in the first and / or second exchange medium or a dependent value depending on the pressure and / or the volume flow of the second exchange medium to a desired, in particular preset, setpoint or to approximate it.

4. Device according to one of the preceding claims, characterized in that in the flow direction after the outlet connection in the line path (3, 4) of one of the two chamber regions, at least one measuring device (5a, 5b) is provided for measuring a measured value representing the at least one process parameter, in particular which represents the concentration of the gas to be exchanged in the exchange medium of this chamber region or is dependent thereon, and that in the second line path (4) of the second chamber region, at least one regulating device (6a, 6b) is provided, with which a. the value of the pressure difference and / or b. the value of the volume flow of the second exchange medium can be changed depending on the measured value.

5. Device according to one of the preceding claims, characterized in that it is set up, in particular during operation, to set or regulate an amount of the pressure difference which is greater than 10 mmHg, preferably greater than 20 mmHg, preferably greater than 50 mmHg, more preferably greater than 100 mmHg, more preferably greater than 200 mmHg, more preferably greater than 300 mmHg, more preferably greater than 400 mmHg, more preferably greater than 500 mmHg, in particular which is less than less than 700 mmHg, preferably less than 600 mmHg.

6. Device according to one of the preceding claims, characterized in that the at least one membrane (2) permeable to the gas to be exchanged is provided on at least one of its sides, in particular on the side which contacts a liquid exchange medium, preferably on the inside of the at least one hollow-fibre-shaped membrane (2), has a layer which prevents the convective passage of the exchange media, or is designed throughout as a membrane which prevents the convective passage.

7. Device according to claim 6, characterized in that the layer or the membrane (2) non-destructively withstands an amount of pressure difference which is greater than 10 mmHg, preferably greater than 20 mmHg, preferably greater than 50 mmHg, more preferably greater than 100 mmHg, more preferably greater than 200 mmHg, more preferably greater than 300 mmHg, more preferably greater than 400 mmHg, more preferably greater than 500 mmHg, but in particular less than 700 mmHg, preferably less than 600 mmHg.

8. Device according to claim 6 or 7, characterized in that the at least one layer is made of a non-porous, in particular non-open-pored porous material, preferably silicone, which allows the diffusion of the gas to be exchanged, or the at least one membrane is made entirely of a non-porous, in particular non-open-pored porous material, preferably silicone, which allows the diffusion of the gas to be exchanged, in particular the at least one membrane (2) comprises a porous carrier element, in particular a porous hollow fiber, which has a layer of silicone on at least one of its sides, preferably which has a minimum thickness of 2 micrometers, more preferably a minimum thickness of 3 micrometers, more preferably a minimum thickness of 4 micrometers, more preferably a minimum thickness of 5 micrometers.

9. Device according to one of the preceding claims, characterized in that the at least one control device (6a, 6b) and the at least one measuring device (5a, 5b) for measuring the at least one process parameter a. is arranged in the line paths (3, 4) of different chamber regions, in particular wherein the device is set up to have a liquid exchange medium as the first exchange medium in the first chamber region connected to the measuring device (5a, 5b), preferably to the outlet-side measuring device, during operation, and the regulating device (6a, 6b) is arranged in the line path (4) of the second chamber region, preferably on the outlet side, which is set up to have the gaseous second exchange medium during operation of the device, further preferably wherein the regulating device (6a, 6b) is set up to regulate an overpressure in the second chamber region relative to atmospheric pressure, or b.are arranged in the same line path (3, 4), in particular in the line path (4) of the second chamber region, which is designed to have the gaseous second exchange medium during operation of the device, preferably, wherein the device is designed to have a liquid exchange medium in the chamber region which has the first exchange medium during operation, further preferably, wherein the control device (6a, 6b) is designed to regulate a negative pressure relative to atmospheric pressure.

10. Device according to one of the preceding claims, characterized in that it is designed for operation a. for enriching oxygen or depleting carbon monoxide in blood as the first exchange medium, for which purpose the at least one measuring device (5a) is designed for measuring the concentration of oxygen, in particular the oxygen partial pressure or the concentration of carbon monoxide, in particular the carbon monoxide partial pressure in blood and is arranged in the line path (3) after the outlet connection of the first chamber region provided for the blood supply, in particular wherein this chamber region adjoins the inner surfaces of a plurality of hollow fiber-shaped membranes, or b.for the depletion of carbon dioxide in blood as a first exchange medium, for which purpose the at least one measuring device (5b) is designed to measure the concentration of carbon dioxide, in particular the carbon dioxide partial pressure in the gaseous second exchange medium and is arranged in the line path (4) after the outlet connection of the chamber region provided for guiding the gaseous second exchange medium, in particular that chamber region which borders the outer surfaces of a plurality of hollow-fiber membranes (2).

11. Device according to one of the preceding claims, characterized in that with the at least one control device (6a, 6b) by controlling the pressure, a predetermined desired partial pressure of the gas to be exchanged or a desired value dependent on the partial pressure of the gas to be exchanged, in particular as a process parameter, can be adjusted.

12. Device according to one of the preceding claims, characterized in that the volume flow of the exchange medium in the second line path (4) can be changed with the at least one control device (6a, 6b) as a function of the at least one measured value and as a further function of the amount of the pressure difference, wherein the control device (6a, 6b) is set up, when a limit of the pressure difference, especially while keeping the pressure difference constant, to increase the volume flow.

13. Device according to one of the preceding claims, characterized in that in the exchange chamber (1) the axial length of a plurality of hollow fiber-shaped membranes is greater than the length of the exchange chamber (1) in the direction of spacing of the ends of the hollow fiber-shaped membranes (2).

14. Device according to one of the preceding claims, characterized in that the line path (3) through the chamber region, which in operation carries a liquid exchange medium, in particular blood, preferably which leads through the interior of hollow fiber-shaped membranes (2), comprises a pulsation device with which recurring, in particular periodic, pressure fluctuations can be generated in the liquid exchange medium.

15. Combination of at least two devices connected in series or in parallel in the flow direction of a preferably liquid exchange medium according to one of the preceding claims, characterized in that at least one device is operated with a positive pressure difference and at least one device with a negative pressure difference, or one device is operated with a pressure difference and the other without a pressure difference.

16. A method for gas exchange between a first exchange medium, in particular excluding blood, and a second gaseous exchange medium with an exchanger unit with an exchange chamber (1) arranged in a housing of the exchanger unit, a. wherein the exchange chamber (1) is formed by at least one membrane (2), preferably by a plurality of hollow fiber-shaped Membranes (2), is divided into a first chamber region in which a first side of the at least one membrane (2) is contacted with the first exchange medium and is divided into a second chamber region in which a second side of the at least one membrane (2) is contacted with the second gaseous exchange medium, and b. wherein the first chamber region has inlet and outlet connections for the first exchange medium, through which the first chamber region is integrated into a first line path (3) with which the first exchange medium is guided through the first chamber region, and c. wherein the second chamber region has inlet and outlet connections for the second gaseous exchange medium, through which the second chamber region is integrated into a second line path (4) with which the second exchange medium is guided through the second chamber region, and d.wherein a gas to be exchanged present in one of the two exchange media is transferred by diffusion across the at least one membrane (2) into the other exchange medium, characterized in that e. with a pressure generating device (9a) in the second chamber region, in particular via the second line path (4), a pressure difference is generated between the second exchange medium and the surrounding atmospheric pressure, in particular is generated in gas exchange operation, which pressure difference has an amount of at least 10 mmHg, wherein. f. the at least one membrane (2) is permeable with respect to diffusion at the pressure difference generated for the gas to be exchanged and impermeable with respect to convection at the pressure difference that can be generated / generated for the two exchange media.

Images