VENTILATION SYSTEM WITH MECHANICAL VENTILATION AND EXTRACORPOREAL BLOOD GAS EXCHANGE

Abstract

A system for supporting the blood gas exchange by means of mechanical ventilation and extracorporeal blood gas exchange comprises a ventilation device for mechanical ventilation of the lungs of a patient, and an ECLS device for the extracorporeal blood gas exchange, wherein the ventilation system is designed to perform mechanical respiratory support by the ventilation device on the one hand and an extracorporeal blood gas exchange by the ECLS device on the other hand in coordinated, automated manner in order to support the gas exchange in the blood circulation of the patient, wherein the ECLS device sets a level of the extracorporeal blood gas exchange, and the ventilation device, on the basis of the level of the extracorporeal blood gas exchange set by the ECLS device, adjusts in automated manner to a level of the mechanical respiratory support.

Claims

1. A ventilation system for supporting blood gas exchange by mechanical ventilation and extracorporeal blood gas exchange, the ventilation system comprising: a ventilation device for mechanical ventilation of lungs of a patient, and an ECLS device for extracorporeal blood gas exchange, wherein the system is designed to perform both mechanical respiratory support by the ventilation device and extracorporeal blood gas exchange by the ECLS device in a coordinated automated manner in order to support the gas exchange in the blood circulation of the patient, wherein the ECLS device sets a level of the extracorporeal blood gas exchange and the ventilation device, on the basis of the level of the extracorporeal blood gas exchange set by the ECLS device, adjusts in an automated manner to a level of mechanical respiratory support.

2. The system of claim 1, wherein the level of the extracorporeal blood gas exchange can be preselected by the ECLS device in an automated or manual manner.

3. The system of claim 2, wherein the ECLS device sets a target value for the level of the extracorporeal blood gas exchange.

4. The system of claim 1, wherein the ventilation device, for a respective effected setting of the level of the extracorporeal blood gas exchange by the ECLS device, automatically controls the mechanical respiratory support by positive-pressure ventilation.

5. The system of claim 4, wherein the ventilation device is designed to select, in an automated manner and in the scope of set ventilation parameters, a ventilation state to be set by the ventilation device, and to control the ventilation device such that the ventilation device assumes the selected ventilation state.

6. The system of claim 5, wherein the set ventilation parameters are derived from the level of the extracorporeal blood gas exchange set by the ECLS device.

7. The system of claim 1, wherein the level of extracorporeal blood gas exchange set by the ECLS device is associated with a degree of extracorporeal support in oxygenation that includes enriching the blood with oxygen.

8. The system of claim 7, wherein the degree of extracorporeal support in oxygenation determines a maximum positive end-expiratory pressure for mechanical ventilation.

9. The system of claim 8, wherein the maximum positive end-expiratory pressure increases with a decreasing degree of extracorporeal support in oxygenation.

10. The system of claim 7, wherein the degree of extracorporeal support in oxygenation determines a maximum value for the flow of the blood taken from the patient by the ECLS device.

11. The system of claim 10, wherein the maximum value for the flow of the blood taken from the patient by the ECLS device increases with an increasing degree of extracorporeal support in oxygenation.

12. The system of claim 1, wherein the level of the extracorporeal blood gas exchange set by the ECLS device is associated with a degree of extracorporeal support in ventilation that includes removing CO2 from the blood.

13. The system of claim 12, wherein the degree of extracorporeal support in ventilation determines a maximum minute volume for mechanical ventilation.

14. The system of claim 13, wherein the maximum minute volume increases with a decreasing degree of extracorporeal support in ventilation.

15. The system of claim 12, wherein the degree of extracorporeal support in ventilation determines a maximum airway pressure for mechanical ventilation.

16. The system of claim 15, wherein the maximum airway pressure increases with a decreasing degree of the maximum value of extracorporeal support in oxygenation and extracorporeal support in ventilation.

17. The system of claim 12, wherein the degree of extracorporeal support in ventilation determines a maximum value of the flow of oxygenation gas that the ECLS device supplies to the blood taken from the patient's blood circulation.

18. The system of claim 17, wherein the maximum value of the flow of oxygenation gas that the ECLS device supplies to the blood taken from the patient's blood circulation, increases with an increasing degree of the extracorporeal support in ventilation.

19. The system of claim 1, wherein at a respective level of the extracorporeal blood gas exchange, the ECLS device examines, after expiration of a predetermined period of time whether, at the level of the extracorporeal blood gas exchange, a predetermined target state for the blood gas exchange is reached by the ventilation device and the ECLS device together.

20. The system of claim 19, wherein the predetermined target state for the blood gas exchange is a parameter that defines a concentration of O2 in the blood circulation.

21. The system of claim 19, wherein the predetermined target state for the blood gas exchange is a parameter that defines a concentration of CO2 in the blood circulation.

22. The system of claim 19, wherein the ECLS device, upon reaching the predetermined target state, reduces the level of the extracorporeal blood gas exchange.

23. The system of claim 19, wherein the ECLS device, upon reaching the predetermined target state which is a set value of a concentration of O2 in the blood circulation, reduces the level of the extracorporeal blood gas exchange in oxygenation by a first predetermined amount.

24. The system of claim 19, wherein the ECLS device, upon reaching the predetermined target state which is set value of a concentration of O2 in the blood, reduces the degree of the extracorporeal support in ventilation by a second predetermined amount.

25. The system of claim 19, wherein the ECLS device examines in recurrent intervals of time whether, at the respective level of the extracorporeal blood gas exchange, a predetermined target value for the blood gas exchange is reached by the ventilation device and the ECLS device together.

26. The system of claim 25, wherein a time interval for the examination by the ECLS device is greater than a time constant of the ventilation device.

27. The system of claim 1, wherein the ECLS device starts from a preset starting value for the level of the extracorporeal blood gas exchange.

28. The system of claim 27, wherein the starting value corresponds to a maximum level for the level of the extracorporeal blood gas exchange.

29. The system of claim 27, wherein the starting value is a reference value for the reduction and increase, respectively, of the level of the extracorporeal blood gas exchange.

30. A method comprising: coordinating cooperation of a ventilation device for mechanical positive-pressure ventilation of the lungs of a patient and an ECLS device for extracorporeal blood gas exchange of the blood of the patient, wherein mechanical respiratory support by the ventilation device on the one hand and an extracorporeal blood gas exchange by the ECLS device on the other hand, are performed in a coordinated automated manner in order to support gas exchange in the blood circulation of the patient, wherein the ECLS device sets a level of the extracorporeal blood gas exchange, and the ventilation device, on the basis of the level of the extracorporeal blood gas exchange set by the ECLS device, adjusts in an automated manner to a level of the mechanical respiratory support.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0046] The invention will be explained in more detail in the following on the basis of embodiments illustrated in the drawings, wherein:

[0047] FIG. 1 shows a schematic, highly simplified view of a ventilation system according to the invention, comprising a device for mechanical ventilation designed as positive-pressure ventilation device, as well as an ECLS device;

[0048] FIG. 2 shows a schematic, highly simplified view according to FIG. 1, illustrating a further ventilation system according to the invention, comprising a device for mechanical ventilation designed as positive-pressure ventilation device, as well as an ECLS device;

[0049] FIG. 3 shows a flow diagram illustrating an example of the procedure of coordinated cooperation between the device for mechanical ventilation and the ECLS device;

[0050] FIG. 4 shows a flow diagram illustrating further details of the procedures taking place in the oxygenation module according to FIG. 3;

[0051] FIG. 5 shows a flow diagram illustrating further details of the procedures taking place in the ventilation module according to FIG. 3;

[0052] FIG. 6 shows a diagram qualitatively illustrating the correlation between the degree of extracorporeal support in oxygenation % ECLS_O2 and the maximum positive end-expiratory pressure PEEPmax;

[0053] FIG. 7 shows a diagram qualitatively illustrating the correlation between the degree of extracorporeal support in oxygenation % ECLS_O2 and the maximum pump flow settable in the ECLS device;

[0054] FIG. 8 shows a diagram qualitatively illustrating the correlation between the degree of extracorporeal support in ventilation % ECLS_CO2 and the maximum minute volume in positive-pressure ventilation;

[0055] FIG. 9 shows a diagram qualitatively illustrating the correlation between the maximum of the degree of extracorporeal support in oxygenation % ECLS_C2 and the degree of extracorporeal support in ventilation % ECLS_CO2, on the one hand, as well as the maximum airway pressure (Pinsp+PEEP)max in positive-pressure ventilation;

[0056] FIG. 10 shows a diagram qualitatively illustrating the correlation between the degree of extracorporeal support in ventilation % ECLS_CO2 and the maximum flow of oxygenation gas settable in the ECLS device;

[0057] FIG. 11 shows a diagram qualitatively illustrating which values for the oxygen saturation value SpO2 measured by means of pulse oximetry, at the respective prevailing positive end-expiratory pressure PEEP, are deemed too high, too low, normal or even as an emergency, and in the query according to FIG. 4 result in corresponding changes of the parameter % ECLS_O2; and

[0058] FIG. 12 shows a diagram qualitatively illustrating which values for the carbon dioxide concentration PaCO2 measured in the arterial blood, at the respective prevailing maximum airway pressure (Pinsp+PEEP), are deemed too high, too low or normal, and in the query according to FIG. 5 result in corresponding changes of the parameter % ECLS_CO2.

DETAILED DESCRIPTION

[0059] FIG. 1 shows in a schematic and highly simplified view a ventilation system 10 according to the invention, comprising a device 20 for mechanical ventilation designed as positive-pressure ventilation device, and an ECLS device 50. The ventilation device 20 comprises a ventilator 22 shown merely schematically in FIG. 1. The ventilator 22 is connected, via a conduit system 24 not shown in more detail, to the airway of a patient (illustrated schematically in FIG. 1 and designated 12). Via the conduit system 22, the ventilator 22 supplies pressurized air to the airway of the patient 12 during inspiration phases and discharges air from the patient's airway during expiration phases. During ventilation, the conduit system 22 permanently has a positive end-expiratory pressure PEEP applied thereto. Added to this pressure, during the inspiration phases, is an inspiration pressure Pinsp that is also applied by the ventilator (and which as a rule changes during the inspiration cycle). During the expiration phases, the ventilator as a rule applies only the positive end-expiratory pressure PEEP with respect to which the lung tissue relaxes.

[0060] The ventilation device 20 furthermore is equipped with a sensor system for detecting parameters essential for ventilation. For example, the following parameters partly illustrated in FIG. 1 are detected in the conduit system 24: inspiration pressure Pinsp, expiration pressure Pexp, positive end-expiratory pressure PEEP, tidal volume VT (i.e., breathing gas volume applied into the lungs during an inspiration cycle), flow quantity of the breathing gas applied, positive pressure of CO2 in the breathing gas (in particular during expiration). The ventilation device 20 moreover comprises sensor means for determining the oxygen saturation in the patient's blood, illustrated in FIG. 1 at numeral 26. This may be provided in the form of a pulse oximetry sensor means (e.g., with fingertip sensor) for subcutaneous determination of the arterial oxygen saturation SpO2. In the embodiment illustrated in FIG. 1, the ventilation device 20 comprises furthermore sensor means for analyzing blood gases, in particular for determining the arterial concentration of oxygen in the blood PaO2 and for determining the arterial concentration of carbon dioxide in the blood PaCO2 in recurrent intervals, as shown schematically in FIG. 1 at numeral 28. Instead of the concentrations PaO2 and PaCO2 of oxygen and carbon dioxide, respectively, there may also be determined the corresponding saturations in hemoglobin SaO2 and SaCO2.

[0061] The ventilation device 20 has a control unit associated therewith, which is designed for controlling all procedures of the ventilation device in largely automated manner. This control unit may be integrated in the ventilator 22, but may also be designed in part or even completely as external control device. The control unit for the ventilation device 20 comprises the usual interfaces for communication with operating personnel, in particular for displaying the ventilation state of the patient and for inputting control commands. The control unit basically is designed such that the ventilation device 20 selects suitable ventilation modes largely autonomously and without manual interventions, respectively, and, in the scope of a preselected ventilation mode, sets the ventilation parameters to optimum values each and, in the sense of closed-loop control systems, also autonomously monitors the ventilation parameters and possibly readjusts the same, so that a desired ventilation state can be maintained, if possible.

[0062] Ventilation devices of this kind, for example, are devices encompassing largely automated ventilation modes, for example the ventilation mode known under the designation Adaptive Support Ventilation which is realized in ventilation devices of the applicant.

[0063] For additional support of the blood gas exchange, the ventilation system 10 in FIG. 1 is provided with an ECLS device (ECLS=extracorporeal lung support), generally indicated at 50. In contrast to the ventilation device 20 that is connected to the patient's airway and applies breathing gas to the lungs via the airway, the ECLS device 50 serves to support the exchange of blood gases directly, i.e., to substitute the function of the lungs partially or even completely. The ECLS device 50 therefore is not coupled to the lungs, but directly to the blood circulation of the patient. The ECLS device 50 comprises a first conduit 52 via which blood is withdrawn from the venous system of the patient and is fed to an extracorporeal blood circulation of the ECLS device. The extracorporeal blood circulation is driven by an ECLS pump 56 which supplies the blood taken from the venous system to an oxygenator 58 and then returns the same via a further conduit 54 to the patient's blood circulation. In case of veno-venous extracorporeal blood gas exchange support, the additional conduit 54 returns the blood enriched with oxygen and depleted from CO2 to the patient's venous system. There are also conceivable forms of veno-arterial extracorporeal blood gas exchange support, in which the additional conduit 54 conveys the blood enriched with oxygen and depleted from CO2 back to the patient's arterial system downstream of the heart, so as to support also the patient's cardiac function in addition to the pulmonary function. In that case, the ECLS device 50 in terms of its function is very similar to a heart-lung machine.

[0064] In the oxygenator 58 the venous blood is depleted from CO2 and enriched with O2. To this end, an oxygenation gas 62 is supplied to the oxygenator 58, which in the oxygenator 58 interacts with the venous blood so as to take up CO2 from the hemoglobin, and to apply O2 to the hemoglobin released thereby. The oxygenator 58 thus substantially takes over the function of the alveoli in the lungs. Such oxygenators 58 are known for example in heart-lung machines. When provided in the form of a membrane oxygenator, a semi-permeable membrane is used for exchange of the blood gases O2 and CO2, with the support in blood gas exchange afforded by the ECLS device being known under the designation ECMO (extracorporeal membrane oxygenation). There are also other oxygenator constructions known and basically usable as well. The oxygenation gas 62 has its origin in a conditioning unit 60 and basically is a gas mixture enriched with O2, sometimes also pure O2. The extent of the desired oxygenation and ventilation, respectively, can be set by the partial pressures of O2 and CO2, respectively, in the oxygenation gas 62. To this end, the oxygenation gas may be suitably conditioned, if desired this can be effected in accordance with the composition of blood gases in the venous system from which the extracorporeal blood gas flow is taken, or in the arterial system.

[0065] The fundamental parameters for controlling the level of blood gas exchange support by the ECLS device 50 are the flow of the blood taken from the body and pumped through the extracorporeal circuit, as well as the flow of the oxygenation gas supplied to the oxygenator. The flow of the blood taken from the body and pumped through the extracorporeal circuit can be detected quite easily by the pump flow generated by pump 58, and can be adjusted. It is also easily possible to detect and adjust the flow of the oxygenation gas by means of suitable flow sensors or flow controls.

[0066] In addition, there is also the possibility to take suitable influence on the composition of the oxygenation gas, as described hereinbefore. For example, it is indeed possible to add a certain amount of CO2 to the oxygenation gas in order to suppress negative physiologic effects of an excessive depletion of CO2.

[0067] For controlling the ECLS parameters, there is provided an ECLS control unit indicated in FIG. 1 as separate control device and shown at numeral 30. The ECLS control unit 30 detects the data mentioned as regards the flow of the blood taken from the body and pumped through the extracorporeal circuit as well as the flow of the oxygenation gas supplied to the oxygenator, and also as regards the composition of the oxygenation gas. In response to these data, the ECLS control unit issues suitable control commands to the ECLS pump 56, the oxygenator 58 and the oxygenation gas generator 60 as well as to actuators associated with the same, in order to set the respectively desired flows and compositions, as a rule via corresponding closed-loop control systems (e.g., PI control systems). This is illustrated in FIG. 1 by way of respective arrows.

[0068] The control unit associated with the ventilation device as well as the control unit associated with the ECLS device operate generally in mutually independent manner. However, they exchange data via a connection illustrated at numeral 40 in FIG. 1 so as to render possible a coordinated mode of operation of the ventilation device 20 on the one hand and the ECLS device 50 on the other hand. This will be described in more detail in the following.

[0069] However, it should already be pointed out here that a physical separation of the control unit 30 associated with the ECLS device 50 and the control unit associated with the ventilation device 20 is not absolutely necessary. It is indeed conceivable to physically combine both control units in one unit or module. Such a unit or module may be provided as an independent unit in addition to the ventilation device 20 and the ECLS device 50, but may also be fully integrated in one of these devices, e.g., in the ventilator 22 shown in FIG. 1.

[0070] FIG. 2 shows, in a schematic and highly simplified view according to FIG. 1, another ventilation system 10 according to the invention, comprising a ventilation device 20 and an ECLS device 50. The reference numerals used in FIG. 2 are in correspondence with those of FIG. 1, in so far as the same or corresponding components are present. In this regard, reference is made to the description of these components in relation to FIG. 1, which applies analogously. The ventilation system according to FIG. 2 differs from that according to FIG. 1 merely in that the sensor system for determining the concentration or saturation of O2 and CO2 (in the form PaO2 and PaCO2, respectively, or in the form SaO2 and SaCO2, respectively) in the patient's blood circulation is no longer associated with the ventilation device 20, but is associated with the ECLS device 50. As indicated by numeral 66, the determination of PaO2/PaCO2 (or SaO2/SaCO2) takes place in the extracorporeal blood circulation. This is expedient in particular in the light of the fact that such a sensor system can easily be accommodated in the extracorporeal blood circulation and as such information as a rule is necessary anyway for operation of the ECLS device 50. Via the interface 40, the data detected in the ECLS blood circulation then are also available for the ventilation device 20.

[0071] FIG. 3 illustrates, in the form of a flow diagram, the basic process of the coordinated cooperation between ventilation device 20 and ECLS device 50 in an example. The flow diagram according to FIG. 3, like the flow diagrams according to FIG. 4 and FIG. 5 to be described hereinafter, are restricted to a representation of the steps and parameters relevant with respect to the coordinated cooperation of ventilation device 20 and ECLS device 50, without any claim to comprehensiveness of the total course of the procedures illustrated.

[0072] After start of the process, there are firstly set starting values for some parameters which are of relevance as regards the coordinated cooperation of ventilation device 20 and ECLS device 50. These are, above all, the parameters of the degree of extracorporeal support in oxygenation % ECLS_O2 and the degree of extracorporeal support in ventilation % ECLS_CO2. In accordance with the embodiment illustrated, both quantities are expressed as relative quantities which each are to show the proportion of the extracorporeal support in blood gas exchange (i.e., in oxygenation and ventilation, respectively) afforded by the ECLS device 50 in relation to the total support in blood gas exchange. In doing so, oxygenation and ventilation will be considered separately and expressed each by a separate degree of extracorporeal support % ECLS_O2 and % ECLS_CO2, respectively. A starting value is assigned both to the parameter % ECLS_O2 and to the parameter % ECLS_CO2. This starting value can be set manually. In selecting the starting values, the condition of the patient in general will be used as orientation, and one will follow an assessment as to the extent or proportion of the necessary additional extracorporeal blood gas exchange in order to arrive at a reasonable overall condition of the patient in cooperation with positive-pressure ventilation. As regards this assessment, it is recommended to proceed conservatively, i.e., to definitely not underestimate the degree of extracorporeal support in oxygenation and ventilation, respectively, but rather in case of doubt, to select the starting values for % ECLS_O2 and % ECLS_CO2 rather too high. In the example illustrated, starting values of 100% each are selected for % ECLS_O2 and % ECLS_CO2, which means that the support in blood gas exchange at the beginning is afforded completely by extracorporeal blood gas exchange, so that the positive-pressure ventilation thus has no contributory effect at all.

[0073] In addition thereto, there is also set a starting value for the content of oxygen in the breathing gas FiO2 supplied to the airway by the ventilation device 20. In the embodiment illustrated in FIG. 3, a starting value of FiO2=100% is set, which means that the ventilation device supplies pure oxygen to the patient as soon as it contributes in supporting the blood gas exchange in addition to the ECLS device 50. The value set for FiO2 in this step, however, will change very rapidly as the ventilation device 20 is configured such that it will always select a best possible ventilation mode and, for the ventilation mode selected, will set the ventilation parameters such that a best possible ventilation state is obtained. In doing so, the ventilation device 20 as a rule will change the value of FiO2, in particular to a value clearly smaller than 100%.

[0074] Upon setting of the starting values, the procedure waits until a predetermined period of time has lapsed (step 120). This predetermined time determines the repetition rate of the renewed adjustment of the parameters for the ECLS device 50. It should be selected clearly longer than the time constant of the ventilation device 20, i.e., the time required for the ventilation device 20 on the average for adjusting to a new state. In the instant example, this time is 30 s.

[0075] After lapse of the predetermined time, the process enters into a procedure for setting relevant parameters with respect to oxygenation (step 200) followed by a procedure for setting relevant parameters with respect to ventilation (step 300).

[0076] This sequence then is repeated recurrently, i.e., the process waits again for the lapse of the predetermined time (step 120), whereupon oxygenation (step 200) takes place, followed by ventilation (step 300), etc.

[0077] FIG. 4 shows a flow diagram illustrating the procedures occurring in the oxygenation module 200 according to FIG. 3 in some more detail. After the start in step 202, the process first waits for a predetermined period of time (step 204) which in the example illustrated is 30 s. After lapse of this time, it is examined in step 206 whether the oxygenation of the blood circulation is sufficient. This can be effected by one or more of the aforementioned sensors, e.g., by determination of the oxygen saturation value SpO2 by pulse oximetry, or by an ongoing analysis of the blood gas values along with a determination of the oxygen concentration in the blood PaO2. If desired, the oxygen saturation SpO2 determined by pulse oximetry may be supplemented with values for PaO2 or SaO2 that are ascertained only sporadically by means of blood gas analysis. If the determination in step 206 has the result that the oxygen concentration or oxygen saturation is within a desired range, the parameter % ECLS_O2, expressing the degree of extracorporeal support in oxygenation, is reduced in step 210 by a predetermined first amount, which in the example illustrated is 0.05%. Starting with this moment of time, the relative proportions of the support in the blood gas exchange between extracorporeal blood gas exchange support by the ECLS device 50 and the support by positive-pressure ventilation change. This can be seen from the graphs in FIG. 6 and FIG. 7: the diagram shown in FIG. 6, which qualitatively illustrates the correlation between the degree of extracorporeal support in oxygenation % ECLS_O2 and the maximum positive end-expiratory pressure PEEPmax, reveals that the reduction of the parameter % ECLS_O2 by the first predetermined amount on the one hand increases the maximum positive end-expiratory pressure PEEPmax set for the ventilation device 20. On the other hand, the diagram according to FIG. 7, which qualitatively illustrates the correlation between the degree of extracorporeal support in oxygenation % ECLS_O2 and the maximum pump flow settable in the ECLS device, reveals that the maximum pump flow becomes lower when the parameter % ECLS_O2 is decreased by the first predetermined amount. However, the maximum pump flow corresponds to the maximum flow of blood that can flow in the extracorporeal ECLS circuit and accordingly is enriched with oxygen. This means that the basic conditions for extracorporeal support by the ECLS device 50 are set narrower whereas the basic conditions for support by the ventilation device 20 are set more leniently.

[0078] After step 208, the process arrives at point 2 in FIG. 4, bearing reference numeral 210. At this point, the procedure proceeds to the ventilation module 300 in FIG. 1. FIG. 5 shows a flow diagram illustrating further details of the procedures taking place in ventilation module 300.

[0079] Firstly, the process again waits for the lapse of a predetermined period of time (step 302), which in the example illustrated is 30 s. After lapse of this time, it is examined in step 304 whether the ventilation of the blood circulation is sufficient. This can be effected by means of one or more of the aforementioned sensors, for example by an ongoing analysis of the blood gas values along with a determination of the carbon dioxide concentration in the blood PaCO2 and the corresponding carbon dioxide saturation SaCO2, respectively. A measurement of the CO2 content in the exhaled air, indicated in FIGS. 1 and 2 as PetCO2, may be used as well. If desired, such a measurement may be supplemented by values for PaCO2 or SaCO2 ascertained only sporadically by means of blood gas analysis. When the determination in step 302 has the result that the carbon dioxide concentration or carbon dioxide saturation is within a desired range, the parameter % ECLS_CO2, which expresses the degree of extracorporeal support in ventilation, is reduced in step 304 by a predetermined second amount, in the example illustrated by 0.05%. Starting with this moment of time, the relative proportions of the support in the blood gas exchange between extracorporeal blood gas exchange support by the ECLS device 50 and the support by positive-pressure ventilation change. This can be seen from the graphs in FIGS. 8 to 10: the diagram shown in FIG. 8, which qualitatively illustrates the correlation between the degree of extracorporeal support in ventilation % ECLS_CO2 and the maximum minute volume in positive-pressure ventilation % MinVolMax, reveals that the reduction of the parameter % ECLS_CO2 by the second predetermined amount on the one hand increases the maximum minute volume % MinVolMax set for the ventilation device 20. On the other hand, the diagram according to FIG. 9, which qualitatively illustrates the correlation between the degree of extracorporeal support in oxygenation % ECLS_O2 and the degree of extracorporeal support in ventilation % ECLS_CO2 on the one hand, and the maximum airway pressure (Pinsp+PEEP)max in positive-pressure ventilation, reveals that also the maximum airway pressure (Pins+PEEP)max becomes higher in positive-pressure ventilation when both parameters have decreased, % ECLS_O2 by the first predetermined amount and % ECLS_CO2 by the second predetermined amount. Both an increase in the maximum minute volume and an increase in the maximum permitted airway pressure allow an in total greater influence of positive-pressure ventilation in the support of the blood gas exchange exerted by the ventilation system in total. In addition, FIG. 10 reveals that the reduction of the parameter % ECLS_CO2 by the second predetermined amount still has an additional effect. It can be seen from the diagram shown in FIG. 10 that qualitatively the maximum flow of oxygenation gas settable in the ECLS device becomes lower with a decreasing degree of extracorporeal support in ventilation % ECLS_CO2. Thus, a reduction of the parameter % ECLS_CO2 also entails a reduction in the blood gas exchange obtainable in total by means of ECLS as the basic conditions for the extracorporeal support by the ECLS device are set narrower. In contrast thereto, the basic conditions for support by positive-pressure ventilation are set more leniently.

[0080] In total, this has the effect that at point 310 the influence of positive-pressure ventilation has increased in total at the expense of the influence of extracorporeal blood gas exchange. And this although the target values set with respect to the enrichment of blood with oxygen and the depletion of blood from CO2, respectively, could be fulfilled with the setting selected initially for the procedure.

[0081] Upon arrival at point 1 in FIG. 5, which bears reference numeral 310, the process returns to point 1 in FIG. 4 which also bears reference numeral 310. This means, there follows a new waiting period, followed by a new detection of the state as regards oxygenation and possibly a new setting of the parameter % ECLS_O2.

[0082] The procedure described means in its entirety that the ventilation system 10 has a tendency to develop from a selected initial state in a direction in which positive-pressure ventilation is gaining increasing influence and the extracorporeal blood gas exchange increasingly loses influence, at least as long as target values concerning oxygenation and ventilation and set by the combined effect of positive-pressure ventilation and extracorporeal blood gas exchange can be achieved. Thus, the ventilation system 10 of itself, without requiring interventions from outside, adjusts to a state in which positive-pressure ventilation takes as much influence as possible and the extracorporeal blood gas exchange is supportive just to a degree that is necessary. This development is promoted by the ECLS device 50, but not by the ventilation device 20. In the end, this leads to a gradual, but continuous development with little or no impacts on the ECLS device by the ventilation device 20 adapting to respective basic conditions set by the ECLS device 50.

[0083] Should the case occur that the concentration of oxygen in the blood detected in step 206 does not correspond to the desired target value, but rather is too low or too high, it is provided that the parameter % ECLS_O2 indicating the degree of extracorporeal support in oxygenation is reduced by a third amount which is greater than the first amount (step 212), or is increased by a fourth amount (step 214). The third amount is greater than the first amount, so that the proportion of positive-pressure ventilation thereafter increases even faster than in case of merely reaching the desired target value for the oxygen concentration in the blood. To the contrary, the increase of % ECLS_O2 by the fourth amount has the effect that the support by positive-pressure ventilation thereafter does no longer increase, but to the contrary decreases. This takes account of the fact that in such a situation the patient's condition does not permit a further increase of the percentage of positive-pressure ventilation. Should the desired oxygen concentration be drastically missed, an emergency is concluded, with the consequence that the parameter % ECLS_O2 is drastically increased, in the example by 10% (step 216) so that a sufficient blood gas exchange can be ensured in the extracorporeal circuit.

[0084] Similar mechanisms are also applicable for the ventilation module 300. Should the situation arise that the concentration of carbon dioxide in the blood, as detected in step 302, does not correspond to the desired target value, but rather is too high or too low, it is provided that the parameter % ECLS_CO2 indicating the degree of extracorporeal support in ventilation is reduced by a fifth amount which is greater than the second amount (step 306), or is increased by a sixth amount (step 308). The fifth amount is greater than the second amount, so that the proportion of positive-pressure ventilation thereafter increases even faster than in the case of merely reaching the desired target value for the carbon dioxide concentration in the blood. To the contrary, the increase of % ECLS_CO2 by the sixth amount has the effect that the support by positive-pressure ventilation thereafter does no longer increase, but to the contrary decreases. This takes account of the fact that, in such a situation, the patient's condition does not permit a further increase of the proportion of positive-pressure ventilation.

[0085] FIG. 11 shows a diagram that qualitatively illustrates which values for the oxygen saturation value SpO2 measured by pulse oximetry, with respect to the respective prevailing positive end-expiratory pressure PEEP, are deemed too high, too low, normal or even as an emergency, and in the query according to FIG. 4 leads to corresponding changes of the parameter % ECLS_O2.

[0086] FIG. 12 shows a diagram that qualitatively illustrates which values for the concentration of CO2 PaCO2 determined in arterial blood, with regard to the respective prevailing maximum airway pressure (Pinsp+PEEP), are deemed too high, too low or normal, and in the query according to FIG. 5 lead to corresponding changes of the parameter % ECLS_CO2.

[0087] In all of the diagrams illustrated, in particular in the correlations illustrated in FIGS. 6 to 12, it is to be noted that merely a qualitative course is to be illustrated. There is no intention to make quantitative statements by this. In addition, the linear course of the relationships merely represents a simplification. The true course may deviate in partial sections or even completely from the linear course. What is of importance is the respective outlined increasing or decreasing tendency of the respective parameters with an increasing value of % ECLS_O2 and % ECLS_CO2, respectively.