Control unit for a ventilator

Abstract

To provide a control unit capable of reliably identifying opening and / or closing of at least a part of a respiratory organ during ventilation of a patient.SOLUTION: The respiratory device 1 comprises a breathing air connection 3, which is connected to the respiratory organs 15 of the patient and makes it possible to ventilate the patient with breathing air, an actuator device 5 for supplying the breathing air connection with a breathing air flow 7, and a sensor device 9 for generating measurement data 11 relating to the ventilation. The control unit 13 of the ventilator is configured to generate a control signal 25 for controlling the actuator arrangement to perform a ventilation maneuver in which at least a part 17, 19 of the respiratory tract is opened in an inspiration phase and / or closed in an expiration phase, and to generate measurement data, wherein the measurement data indicate a pressure-dependent curve of a volume of at least one breathing gas inhaled by the patient in the inspiration phase and / or exhaled in the expiration phase as a function of the pressure of the breathing air.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control unit for a ventilator. Furthermore, the invention relates to a computer program executable by a control unit, a corresponding computer readable medium, and a ventilator comprising such a control unit. [Background technology]

[0002] In ventilated patients, under certain circumstances, repeated collapse of the lung or parts of the lung may occur during expiration. In the worst case, this may cause local lung damage and adversely affect the patient's prognosis. Therefore, ventilation should be performed in a way that avoids such collapses as much as possible.

[0003] Furthermore, with regard to lung recruitment maneuvers, it has been shown to be important to identify airway obstruction as well as lung collapse.

[0004] Such airway obstruction can block airflow between the proximal airway opening and distal (smaller) airway structures and / or distal alveolar structures. As a result, lung re-expansion can occur only when the airways reopen. The pressure required for this is sometimes referred to as airway opening pressure. However, even during end-expiratory obstruction, the pressure within the airways may be distinctly different from the pressure within the alveoli. This can lead to misinterpretation of ventilation status. Therefore, a reliable and easy-to-perform method for distinguishing such pressures is needed. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention can be to provide a control unit capable of reliably identifying the patency and / or obstruction of at least a part of the respiratory tract during ventilation of a patient. Further objects of the present invention can be to provide a corresponding computer program, a corresponding computer-readable medium, and a corresponding ventilator. [Means for solving the problem]

[0006] These problems are solved by the subject matter of the independent claims. Advantageous embodiments of the invention are set forth in the dependent claims, the following description and the accompanying drawings.

[0007] A first aspect of the present invention relates to a control unit of a ventilator, comprising a breathing air connection connected to a patient's respiratory tract to enable ventilation of the patient with breathing air, an actuator mechanism for supplying a breathing air flow to the breathing air connection, and a sensor mechanism for generating measurement data related to the ventilation. The control unit is configured to perform the following method: generate a control signal for controlling the actuator mechanism to perform a ventilation maneuver in which at least a portion of the respiratory tract opens during an inspiration phase and / or closes (or collapses) during an expiration phase; receive measurement data representing a pressure-dependence curve of an amount of inhaled air during the inspiration phase and / or an amount of exhaled air during the expiration phase of at least one respiratory gas as a function of the pressure of the breathing air; and determine an opening pressure corresponding to the pressure of the breathing air when at least a portion of the respiratory tract opens by evaluating a portion of the pressure-dependence curve related to the inspiration phase and / or determine a closing pressure corresponding to the pressure of the breathing air when at least a portion of the respiratory tract closes (or collapses) by evaluating a portion of the pressure-dependence curve related to the expiration phase.

[0008] Surprisingly, experiments have shown that there are characteristic breakpoints in the progression of carbon dioxide or oxygen partial pressure relative to ventilation pressure in the corresponding (pressure-based) capnogram or oxigram. These breakpoints correlate significantly with opening or closing pressures, as can be determined in conventional bedside lung recruitment maneuvers followed by PEEP titration. In other words, opening or closing pressures can be read directly from such capnograms or oxigrams without necessarily having to consider additional information for validation. This represents a significant advantage in terms of accuracy, reliability, and efficiency compared to conventional recruitment or titration methods.

[0009] In contrast to complex probability-based computational methods for assessing airway opening pressure and lung mechanics during ventilation, such a method allows accurate and reliable determination of opening or closing pressures while significantly reducing computational costs. An additional advantage is that it eliminates the need for time-consuming PEEP titration over multiple breaths. Furthermore, it reduces the risk of lung overinflation that can occur with increased ventilation pressures over longer periods.

[0010] The control unit may comprise data processing means. The data processing means may be implemented as hardware and / or software and / or may comprise a processor. The processor may be configured to execute a (computer-implemented) method. In addition to the processor, the control unit may comprise at least one of the following data processing means: a memory, a bus system for data communication between the memory and the processor, a data communication interface for wireless and / or wired data communication with peripherals. Alternatively, the control unit may be implemented exclusively as hardware, for example in the form of an ASIC module or an FPGA module.

[0011] "Breathing air" can be understood as a single breathing gas or a mixture of breathing gases for the ventilation of a patient. "Breathing gas" can be understood as, for example, carbon dioxide, oxygen, nitrogen, water vapor, or anaesthetic gas.

[0012] A "ventilatory maneuver" can generally be understood as a maneuver in which at least a portion of the respiratory system, e.g., the airways and / or lungs, more precisely at least a portion of the alveoli, are opened during inspiration (also called recruitment) and / or closed (or collapsed) during expiration, by adaptively controlling the pressure and / or volumetric flow of breathing air. A ventilation maneuver can be performed during a single breath or during multiple, e.g., consecutive, uninterrupted breaths.

[0013] It should be understood that the at least partial obstruction of the respiratory tract does not occur actively, but (purely) passively due to the surface tension and resilience of the lung tissue and the thorax. This avalanche-like system can be targeted and inhibited during ventilation, for example by correspondingly increasing or decreasing the duration and / or pressure range of the obstruction. The term "obstruction" should therefore be understood in particular as collapse.

[0014] The control signal may further be generated using the measured data (or at least part of the measured data), thereby allowing the ventilation procedure to be controlled according to the current state of the patient.

[0015] "Amount" can be understood as the partial pressure or concentration of the respective respiratory gas in the patient's respiratory airflow and / or blood.

[0016] The measurement data may be generated using a sensor mechanism during the performance of a ventilation maneuver. For example, the measurement data used to determine the opening pressure, i.e., the measurement data representing the portion of the pressure-dependence curve related to the inspiratory phase, may be generated during the inspiratory phase of the ventilation maneuver. In a corresponding manner, the measurement data used to determine the closing pressure, i.e., the measurement data representing the portion of the pressure-dependence curve related to the expiratory phase, may be generated during the expiratory phase of the ventilation maneuver. Furthermore, at least one other portion of the pressure-dependence curve may be evaluated to determine the opening pressure and / or the closing pressure.

[0017] The measurement data can be generated during a single breath and / or can be newly generated and / or newly received with each breath. In other words, the pressure-dependence curve can be associated with a single breath and / or updated with each breath. Depending on the respective respiratory gas, the pressure-dependence curve can also be referred to as, for example, a pressure-based or pneumatic capnogram or oxigram.

[0018] A second aspect of the invention relates to a ventilator comprising a breathing air connection adapted to be connected to the respiratory tract of a patient and enabling the patient to be ventilated with breathing air, an actuator mechanism for supplying a flow of breathing air to the breathing air connection, a sensor mechanism for generating measurement data relating to the ventilation, and a control unit as described above and below.

[0019] "Ventilator" can be understood as, for example, a device for providing invasive and / or non-invasive ventilation to a patient, and / or an anesthesia device.

[0020] The breathing air connection may be connectable to the respiratory system via one or more ventilation tubes and / or a suitable patient interface, such as a mask, nasal cannula, or tube.

[0021] The actuator mechanism may include, for example, one or more blowers and / or one or more electrically controllable valves.

[0022] The sensor mechanism can be configured to detect, for example, at least one of the following variables: the amount of breath inhaled during the patient's inspiratory phase and / or the amount of breath exhaled during the patient's exhalation phase of the respective breathing gas, the pressure of the breathing air, the volume of the breathing air, and the volumetric flow rate of the breathing air. The sensor mechanism can include one or more sensors. The sensor or at least some of the sensors can be positioned in the main and / or side streams of the breathing air, which are the patient's inhaled and / or exhaled breath.

[0023] A third aspect of the present invention relates to a computer program for operating the above-mentioned and below-mentioned ventilator, the computer program comprising instructions which, when executed by a control unit, cause the control unit, e.g. a processor of the control unit, to perform the following method: generating control signals for controlling an actuator mechanism to perform a ventilation maneuver in which at least a part of a respiratory organ opens in an inspiration phase and / or closes (or collapses) in an expiration phase; receiving measurement data indicative of a pressure-dependence curve of an amount of breath inhaled in an inspiration phase and / or an amount of breath exhaled in an expiration phase of at least one respiratory gas as a function of the pressure of the breathing air; and determining an opening pressure corresponding to the pressure of the breathing air when at least a part of the respiratory organ opens by evaluating a portion of the pressure-dependence curve related to the inspiration phase and / or determining a closing pressure corresponding to the pressure of the breathing air when at least a part of the respiratory organ closes (or collapses) by evaluating a portion of the pressure-dependence curve related to the expiration phase.

[0024] A fourth aspect of the invention relates to a computer readable medium having stored thereon a computer program as described above and below.

[0025] The computer-readable medium may be a volatile or non-volatile data memory. For example, the computer-readable medium may be a hard disk, a USB memory device (USB = universal serial bus), a RAM (random-access memory), a ROM (read-only memory), an EPROM (erasable programmable read-only memory), an EEPROM (electrically erasable programmable read-only memory), a flash memory, or a combination of at least two of these examples. The computer-readable medium may also be a data communication network that allows for downloading of the program code (e.g., via the Internet), or a cloud.

[0026] It is noted that the features of the control unit mentioned above and below may also be features of a computer program and / or a computer readable medium (and vice versa).

[0027] Various embodiments of the present invention are described below, which should not be construed as limiting the scope of the present invention.

[0028] According to one embodiment, the opening pressure can include an airway opening pressure corresponding to the pressure of breathing air when a patient's (previously at least partially obstructed) airway is at least partially opened. Additionally or alternatively, the opening pressure can include a lung opening pressure corresponding to the pressure of breathing air when a patient's (previously at least partially collapsed) lung is at least partially opened or recruited.

[0029] According to one embodiment, the closure pressure can include a lung closure pressure corresponding to the pressure of breathing air when a patient's (previously at least partially patent or recruited) lungs at least partially close, i.e., at least partially collapse. Additionally or alternatively, the closure pressure can include an airway closure pressure corresponding to the pressure of breathing air when a patient's (previously at least partially patent) airway at least partially closes (or at least partially collapses).

[0030] According to one embodiment, the control signal can be generated so that the inspiratory pressure, corresponding to the pressure of the breathing air during the inspiratory phase, increases over a number of consecutive time steps. The inspiratory pressure in each time step can be higher than the previous time step. In other words, the inspiratory pressure can continuously increase from a given starting value to a given ending value. Additionally or alternatively, the inspiratory pressure can follow a given inspiratory pressure curve, which can increase at least partially linearly. This is useful when the starting value corresponds to the inspiratory pressure when at least a portion of the respiratory tract is obstructed. For example, the starting value of the inspiratory pressure can be zero or the respective ambient pressure. Meanwhile, the ending value corresponds to the inspiratory pressure when the lungs are at least largely open or recruited without excessive inflation. For example, the ending value of the inspiratory pressure can be up to 30 cmH2O, 40 cmH2O, 50 cmH2O, or 60 cmH2O. However, other starting and / or ending values ​​of the inspiratory pressure are also possible depending on the condition of the respective patient.

[0031] According to one embodiment, the control signal can be generated such that the volumetric flow rate of breathing air during the expiratory phase follows a given (e.g., time-dependent) volumetric flow rate curve. In other words, ventilation during the expiratory phase can be flow-controlled. The volumetric flow rate curve can be at least partially constant and / or at least partially increasing and / or at least partially decreasing. This allows for a more accurate assessment of the pressure-dependent curve compared to a pressure-controlled expiratory phase.

[0032] According to one embodiment, the volumetric flow rate of breathing air during the expiratory phase can be between 0.02 l / s and 0.20 l / s, preferably between 0.05 l / s and 0.15 l / s, particularly preferably 0.10 l / s. Alternatively, the volumetric flow rate can be at least 0.02 l / s, preferably at least 0.05 l / s, and / or at most 0.20 l / s, preferably at most 0.15 l / s. This allows a particularly accurate evaluation of the pressure-dependence curve due to the significantly extended time window compared to a pressure-controlled expiratory phase.

[0033] According to one embodiment, the control signal can be generated such that the expiratory pressure, corresponding to the pressure of the breathing air during the expiratory phase, decreases in multiple successive time steps. Here, the expiratory pressure in each time step can be lower than in the preceding time step. In other words, the expiratory pressure can decrease continuously from a given starting value to a given ending value. Additionally or alternatively, the expiratory pressure can follow a given expiratory pressure curve. Here, the expiratory pressure curve can decrease at least partially linearly. The ending value of the expiratory pressure can be, for example, zero or correspond to the respective ambient pressure. The starting value of the expiratory pressure can coincide with the ending value of the inspiratory pressure at the end of the preceding inspiratory phase and / or the ending value of the expiratory pressure can coincide with the starting value of the inspiratory pressure at the start of the following inspiratory phase. The ending value of the expiratory pressure can be, for example, positive end-expiratory pressure, or PEEP for short. Thus, the starting value of the inspiratory pressure can correspond to the PEEP of the preceding breath.

[0034] According to one embodiment, determining the opening and / or closing pressure may include identifying a characteristic breakpoint in the pressure dependence curve, determining a pressure of the breathing air corresponding to the characteristic breakpoint, and determining the opening and / or closing pressure. In other words, determining the opening and / or closing pressure may include identifying a characteristic change in the slope of the pressure dependence curve.

[0035] When the airway is obstructed and the inspiratory pressure reaches a critical threshold, the airway suddenly opens, allowing fresh, i.e., oxygen-rich, breathing air to flow into the lungs. This dilutes the spent, i.e., carbon dioxide-rich, breathing air that remained in the respiratory tract during previous expiration, resulting in a corresponding significant drop in the carbon dioxide partial pressure in the breathing airflow. The effect of this sudden opening is identified, for example, as a characteristic breakpoint in a corresponding pressure-based capnogram. The breathing air pressure corresponding to this breakpoint can therefore be considered the airway opening pressure.

[0036] According to one embodiment, characteristic breakpoints can be identified based on, for example, a characteristic decrease in the magnitude of the mean slope of the pressure-dependence curve with increasing ventilation duration, allowing accurate and reliable identification of opening or closing pressures even under widely varying patient conditions.

[0037] A characteristic breakpoint corresponding to opening pressure, particularly airway opening pressure, may correspond, for example, to a decrease of at least 50 percent or at least 70 percent in the magnitude of the (average) slope of the pressure-dependence curve in the first third of the inspiratory phase.

[0038] For example, to determine opening pressure, a portion of the pressure dependence curve can be evaluated over an inspiratory pressure range of 0 cmH2O to 20 cmH2O, or 5 cmH2O to 15 cmH2O, or 10 cmH2O to 15 cmH2O, although other inspiratory pressure ranges are possible depending on the individual patient's condition.

[0039] For example, to determine the closure pressure, a portion of the pressure dependence curve can be evaluated over the expiratory pressure ranges of 0 cmH2O to 20 cmH2O, or 0 cmH2O to 15 cmH2O, or 0 cmH2O to 10 cmH2O, although other expiratory pressure ranges are possible depending on the individual patient's condition.

[0040] According to one embodiment, the inspiration phase and the expiration phase may be successive phases of one breath, in other words the pressure dependence curve may relate to one breath.

[0041] According to one embodiment, a portion of the pressure-dependence curve can be evaluated in the first half or first third of the inspiratory phase (e.g., of a single breath) to determine the opening pressure. In other words, by evaluating the pressure-dependence curve, the opening pressure can be determined at the beginning of the inspiratory phase rather than at the end. Additionally or alternatively, a portion of the pressure-dependence curve can be evaluated in the last third of the expiratory phase (e.g., in the same breath as the inspiratory phase) to determine the closing pressure. In other words, by evaluating the pressure-dependence curve, the closing pressure can be determined at the end of the expiratory phase rather than at the beginning.

[0042] The expiratory phase can be divided into multiple phases, for example, by evaluating the corresponding volumetric capnograms or oxigrams, where each volume-dependent curve can be divided into, for example, at least three consecutive phases characteristic of one breath. The phases can differ significantly from one another in terms of their length and / or the (e.g., average) slope of the volume-dependent curve.

[0043] For example, in the case of a volumetric capnogram, the first phase can be from the beginning of expiration to the first point where the rate of change of the second derivative of the volume-dependent curve reaches a maximum or where the third derivative of the volume-dependent curve reaches a maximum on the left side. The second phase can be from the first point to the second point where the third derivative of the volume-dependent curve reaches a maximum on the right side. The third phase can be from the second point to the end of expiration. Here, the term "volume-dependent curve" can also be understood as a suitable approximation. The first phase can refer to the earliest phase of expiration in which little or no carbon dioxide is present in the respiratory air (e.g., 10%-12% of the entire breath). The second phase can refer to the phase in which the (average) increase in the amount of carbon dioxide in the respiratory airflow is greatest (e.g., 15%-18% of the entire breath). The third phase can refer to the phase in which the amount of carbon dioxide (as opposed to the preceding phases) is primarily determined by gas expelled from the alveoli (e.g., 70%-75% of the entire breath).

[0044] The phase portion can be approximated from the (e.g., measured) volume-dependence curve, for example, according to the Fowler method and / or the Levenberg-Marquardt method. The "Levenberg-Marquardt method" can be understood as a special numerical optimization algorithm for solving nonlinear fitting problems by the least-squares method. This algorithm can be interpreted as a combination of the Gauss-Newton method and a regularization technique that enforces a decrease in function values. This allows for a more accurate and computationally efficient approximation than traditional Fowler method implementations, even when there is a large variation in the volume-dependence curve between consecutive breaths and / or between different patients.

[0045] Alternatively, the phase fraction can be determined in a corresponding manner using a volumetric oxigram.

[0046] According to one embodiment, the measurement data may further show a volume-dependence curve of the amount of breath inhaled during the inspiratory phase and / or the amount of breath exhaled during the exhalation phase of the patient for at least one respiratory gas as a function of the volume of respiratory air. The opening pressure may further be determined by evaluating a portion of the volume-dependence curve related to the inspiratory phase. Additionally or alternatively, the closing pressure may further be determined by evaluating a portion of the volume-dependence curve related to the exhalation phase. For example, each point on the volume-dependence curve may correspond to a certain percentage of the total volume of breath air inhaled and / or exhaled (including the respective respiratory gas) in one breath of the patient. Thus, the beginning of the volume-dependence curve may correspond to a volume value of zero, and the end of the volume-dependence curve may correspond to a volume value equal to the total volume. Such a total volume may also be referred to as a respiratory volume or tidal volume. Depending on the respective respiratory gas, the volume-dependence curve may also be referred to as, for example, a volume-based or volumetric capnogram or oxigram. This embodiment allows for further validation of the results obtained by evaluating the pressure-dependence curve.

[0047] According to one embodiment, the measurement data may further show a time-dependent curve of the patient's inhaled volumetric flow rate during the inhalation phase and / or exhaled volumetric flow rate during the exhalation phase of breathing air as a function of ventilation duration. The opening pressure may further be determined by evaluating a portion of the time-dependent curve related to the inhalation phase. Additionally or alternatively, the closing pressure may further be determined by evaluating a portion of the time-dependent curve related to the exhalation phase. In this example, determining the opening and / or closing pressure may involve identifying further characteristic breakpoints in the time-dependent curve (as in evaluating the pressure-dependent curve) and determining the pressure of the breathing air corresponding to the further characteristic breakpoint, thereby determining the opening and / or closing pressure. This embodiment allows for further validation of the results obtained by evaluating the pressure-dependent curve.

[0048] If the airway is (completely) obstructed at the beginning of the inspiratory phase, the pressure of the respiratory air increases while the volumetric flow of the respiratory air tends to zero. Only when the pressure of the respiratory air is high enough to open the airway does the volumetric flow also increase. Therefore, the pressure of the respiratory air corresponding to this first breakpoint in the time-dependent curve of the volumetric flow during the inspiratory phase can be considered the airway opening pressure.

[0049] After the airways are cleared, the lungs are gradually filled with respiratory air. At this point, some distal portions of the lungs may still be collapsed. Only when the pressure of the respiratory air becomes large enough will these still-collapsed portions, such as smaller airway structures and alveolar structures, also open. The volumetric flow rate of the respiratory air correspondingly increases significantly. Therefore, the pressure of the respiratory air at which the volumetric flow rate of the respiratory air reaches its (local) maximum during the inspiratory phase can be considered the lung opening pressure. If the lung opening pressure is exceeded during the further progression of the inspiratory phase, the volumetric flow rate will again decrease significantly as the lung tissue reaches its elastic limit. Any further pressure increase beyond this point may lead to undesirable lung hyperinflation.

[0050] According to one embodiment, the method can further include determining at least one target value for the pressure of the breathing air, taking into account the opening pressure and / or the closing pressure, and controlling the actuator mechanism using the at least one target value. The target value or values ​​can be, for example, positive end-expiratory pressure, or PEEP for short. The target value or values ​​can be, for example, between the opening pressure and the closing pressure. This can avoid the need for time-consuming titration of PEEP individually for each patient, as is typically performed.

[0051] According to one embodiment, the measurement data may include and / or be based on (e.g., measured and / or estimated) values ​​for at least one of the following variables: the amount of at least one breathing gas inhaled during the inhalation phase and / or exhaled during the exhalation phase of the patient, the pressure of the breathing air, the volume of the breathing air, the volumetric flow rate of the breathing air. The volume of the breathing air may, for example, be determined by integrating the volumetric flow rate of the breathing air.

[0052] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but it should not be understood that the description and drawings are intended to limit the scope of the present invention. [Brief explanation of the drawings]

[0053] [Figure 1] 1 is a diagram showing a ventilator according to an embodiment of the present invention. [Figure 2] FIG. 4 is a flow diagram illustrating a method that may be performed by a control unit according to an embodiment of the present invention. [Figure 3] 10A and 10B show time-dependent pressure and volumetric flow curves when performing a ventilation maneuver using a control unit according to an embodiment of the present invention. [Figure 4] 1 is a pressure-based capnogram for evaluation by a control unit according to one embodiment of the present invention. [Figure 5] 10 is a volume-based capnogram for evaluation by a control unit according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] The figures are only schematic and are not to scale. When the same reference signs are used in different figures, these signify the same or equivalent features.

[0055] Figure 1 shows a ventilator 1 comprising a breathing air connection 3, an actuator mechanism 5 for supplying a breathing air flow 7 to the breathing air connection 3, and a sensor mechanism 9 for generating measurement data 11 relating to at least one ventilation-related measurement variable. Furthermore, the ventilator 1 comprises a control unit 13 connected to the actuator mechanism 5 and the sensor mechanism 9 and for example further using the measurement data 11 to control the actuator mechanism 5.

[0056] The actuator mechanism 5 may include one or more blowers and / or one or more electrically controllable valves.

[0057] The sensor mechanism 9 may include one or more sensors, for example, at least one of a carbon dioxide sensor for detecting the partial pressure of carbon dioxide pCO2 (see Figures 4 and 5), an oxygen sensor for detecting the partial pressure of oxygen, a flow sensor for detecting the volumetric flow rate Q of the breathing air, and a pressure sensor for detecting the pressure p of the breathing air (see Figure 3).

[0058] The breathing air connection 3 is connected to the patient's respiratory system 15, in particular the patient's airways 17 and / or lungs 19 (e.g. via one or more ventilation tubes and a suitable patient interface, such as a mask, nasal cannula, or tube) so that the patient can be ventilated with breathing air. Depending on the application, ventilation can be performed invasively or non-invasively.

[0059] The control unit 13 may include a processor 21 and a memory 23 capable of storing a computer program for operating the ventilator 1. The processor 21 may be configured to execute the computer program to perform the following method M for operating the ventilator 1. The flow of the method M is illustrated in FIG.

[0060] In step S1, a control signal 25 is generated to control the actuator mechanism 5 to perform a specific ventilation maneuver, for example, for recruitment of the lungs 19. As can be seen from the progression of the respiratory air pressure p during ventilation of a patient shown in Figure 3, the ventilation maneuver can be performed such that, during the inspiratory phase I of a breath, the airways 17 (which were previously closed) are first opened, followed by the lungs 19 (which were previously at least partially collapsed). Then, during the expiratory phase E of the same breath, the lungs 19 are again closed, i.e., at least partially collapsed. The ventilation maneuver can be performed, for example, in less than one minute.

[0061] In step S2, measurement data 11 are received. The measurement data 11 may have been generated during the performance of a ventilation procedure. In this example, the measurement data 11 show a pressure dependence curve 27 of the carbon dioxide partial pressure pCO2 as a function of the pressure p of the breathing air breathed by the patient during the performance of the ventilation procedure (hereinafter referred to as the pressure dependence curve 27 for short) (see FIG. 4). The measurement data 11 may, for example, comprise (measured and / or estimated) values ​​for at least one of the following measurement variables and / or may be based on (measured and / or estimated) values ​​for at least one of the following measurement variables: the carbon dioxide partial pressure pCO2, the oxygen partial pressure, the breathing air pressure p, the breathing air volume V, and the breathing air volumetric flow rate Q.

[0062] In step S3, the airway opening pressure p is determined, for example, by evaluating the pressure dependence curve 27 during the inspiratory phase I (shown by the solid line in FIG. 4), in particular during the first half or first third of the inspiratory phase I. o_aw Calculate the airway opening pressure p o_aw corresponds to the pressure p of the respiratory air when the airway 17 (which was, for example, closed during previous exhalation) is (fully) opened.

[0063] Additionally or alternatively, by evaluating the pressure dependence curve 27 during the expiratory phase E (shown by the dashed line in FIG. 4), particularly during the last third of the expiratory phase E, the lung closure pressure p, which corresponds to the pressure p of the respiratory air at which the lung 19 (e.g., which had been open during previous inspiration) begins to collapse again, can be determined. c_lu can be obtained.

[0064] As shown in FIG. 3, for example, by using the measurement data 11 to evaluate the time-dependent curve 28 of the volumetric flow rate Q of breathing air during the inspiration phase I, the lung opening pressure p o_lu can be further calculated. o_lu may correspond to the pressure p of the respiratory air when the volumetric flow Q of respiratory air reaches its maximum value during the inspiration phase I as a result of (full) opening of the lungs 19 (which, for example, had been at least partially collapsed during previous expiration).

[0065] The control signal 25 is an inspiratory pressure p corresponding to the pressure p of breathing air during the inspiratory phase I. I can be generated to increase in several successive time steps. I can be higher at each time step than at the previous time step, resulting in an intake pressure p I Furthermore, the control signal 25 controls the actuator mechanism 5 to adjust the intake pressure p I can be controlled so that it increases linearly at least for the most part. I At least partially non-linear progressions of .times. ...

[0066] Intake pressure p I Similarly, the pressure p of the breathing air during the expiratory phase E is controlled by the control signal 25 to the expiratory pressure p E can be controlled to obtain a continuous and / or at least largely linearly decreasing progression.

[0067] To improve the accuracy of the evaluation of the pressure dependence curve 27 during the expiratory phase E, the respiratory air flow 7 during the expiratory phase E can also be supplied in a flow-controlled manner. For this purpose, a control signal 25 can be generated so that the volumetric flow Q of the respiratory air during the expiratory phase E follows a given, e.g., constant, volumetric flow curve. Suitable target values ​​for the volumetric flow Q of the respiratory air are, for example, 0.02 l / s to 0.20 l / s, preferably 0.05 l / s to 0.15 l / s, particularly preferably 0.10 l / s. In principle, the volumetric flow Q during the expiratory phase E should not be too large, so as to ensure a sufficiently large time window for evaluating the pressure dependence curve 27.

[0068] In Figure 4, the pulmonary closure pressure p is calculated by applying two slope tangents to the pressure dependence curve 27. c_lu As shown in the example of Fig. 1, the average slope of the pressure dependence curve 27 can be determined for several successive time steps, and a characteristic breakpoint in the pressure dependence curve 27 can be identified based on a characteristic decrease in this slope with increasing ventilation duration t. This breakpoint is related to the airway opening pressure p o_aw or pulmonary closure pressure p c_lu It can be shown that

[0069] The airway 17 is obstructed and the inspiratory pressure p I When the critical threshold is reached, the airway 17 suddenly opens, allowing fresh, i.e., oxygen-rich, breathing air to flow into the lungs 19. This dilution of the spent, i.e., carbon dioxide-rich, breathing air remaining in the respiratory tract 15 during previous expiration results in a correspondingly large drop in the carbon dioxide partial pressure pCO2 in the breathing airflow 7. The pressure p of breathing air corresponding to this breakpoint on the pressure-dependence curve 27 is known as the airway opening pressure pCO2. o_aw It can be considered as follows.

[0070] As shown in Fig. 5, the measurement data 11 can further show a volume-dependence curve 29 of the carbon dioxide partial pressure pCO2 as a function of the volume V of breathing air (hereinafter referred to as volume-dependence curve 29 for short). The volume-dependence curve 29 can be used for further validation when evaluating the pressure-dependence curve 27. For this purpose, for example, the lung closure volume V can be calculated based on the volume-dependence curve 29. c_lu can be determined, which corresponds to the volume V of respiratory air in the at least partially collapsed lungs 19 at or near the end of the expiratory phase E. c_lu and pulmonary closure pressure p c_lu Since the variables can be correlated with each other over time, these two variables are suitable for cross-validation.

[0071] Furthermore, in step S4, the airway opening pressure p o_aw and / or lung opening pressure p o_lu and / or pulmonary closure pressure p c_lu At least one target value for the breathing air pressure p can be determined taking into account: The at least one target value can include, for example, an upper target value and a lower target value for a range within which the breathing air pressure p varies.

[0072] Finally, in step S5, the target value or values ​​can be used to further control the actuator mechanism 5 during normal ventilation operation, ie following a ventilation maneuver.

[0073] Finally, it is noted that the terms "comprise", "include", "have", "involve" and the like do not exclude other elements or steps, and non-quantitative words do not exclude a plurality.

[0074] Furthermore, it is noted that features or steps described with reference to one of the above-described embodiments may also be used in combination with features or steps described with reference to other of the above-described embodiments.

[0075] Any reference signs in the claims should not be construed as limiting the scope of the subject matter defined by the claims. [Explanation of symbols]

[0076] 1 ventilator 3 Breathing air connection 5 Actuator mechanism 7. Respiratory Airflow 9 Sensor mechanism 11 Measurement data 13 Control Unit 15 Respiratory organs 17 Airway 19 Lungs 21 processors 23 Memory 25 Control Signals 27 Pressure Dependence Curve 28 Time-dependent curve 29 Volume Dependence Curve p pressure p c_lu Pulmonary closure pressure p o_aw Airway opening pressure p o_lu Lung opening pressure p E Expiratory pressure p I Intake pressure pCO2 partial pressure of carbon dioxide t time, ventilation duration E exhalation phase I. Inspiratory phase M method Q Volumetric flow rate Generates S1 control signals S2 Receive measurement data S3 Determine opening and / or closing pressure S4 Determine one or more target values S5 Use more than one target value V volume V c_lu Lung closure volume

Claims

1. A control unit (13) for a ventilator (1), comprising: The ventilator (1) comprises: a breathing air connection (3) connected to the patient's respiratory system (15) and enabling said patient to be ventilated with breathing air; an actuator mechanism (5) for supplying a flow of breathing air (7) to said breathing air connection (3); a sensor mechanism (9) for generating measurement data (11) relating to said ventilation; Equipped with The control unit (13) comprises the following method (M): generating (S1) a control signal (25) for controlling the actuator mechanism (5) to perform a ventilation maneuver in which at least a portion (17, 19) of the respiratory system (15) is opened during an inspiratory phase (I) and / or closed during an expiratory phase (E); Receiving (S2) the measurement data (11), wherein the measurement data (11) includes the pressure of the breathing air (p, p Ｅ , p Ｉ ) of at least one respiratory gas of the patient inhaled during the inhalation phase (I) and / or exhaled during the exhalation phase (E) (pCO ２ ) pressure dependence curve (27); By evaluating the part of the pressure dependence curve (27) related to the inspiratory phase (I), the pressure (p, p) of the breathing air when at least a part (17, 19) of the respiratory system (15) opens is determined. Ｉ ) corresponding to the opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) (S3) and / or by evaluating the part of the pressure dependence curve (27) related to the expiratory phase (E), the pressure (p, p) of the breathing air when at least a part (17, 19) of the respiratory system (15) is obstructed. Ｅ ) corresponding to the closing pressure (p ｃ＿ｌｕ ) (S3); a control unit configured to:

2. A control unit (13) according to claim 1, The opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) is the pressure (p, p) of the breathing air when the airway (17) of the patient is at least partially open. Ｉ ) corresponding to the airway opening pressure (p ｏ＿ａｗ ), and / or the pressure of the breathing air when the lungs (19) of the patient are at least partially open (p, p Ｉ ) corresponding to the lung opening pressure (p ｏ＿ｌｕ ) and / or The closing pressure (p ｃ＿ｌｕ ) is the pressure (p, p) of the breathing air when the lungs (19) of the patient are at least partially obstructed. Ｅ ) corresponding to the pulmonary closure pressure (p ｃ＿ｌｕ ) a control unit.

3. A control unit (13) according to claim 1 or 2, The control signal (25) is an inspiratory pressure (p) corresponding to the pressure (p) of the breathing air during the inspiratory phase (I). Ｉ ) is generated to follow a given intake pressure curve that increases at least partially linearly and / or in a number of successive time steps, and the intake pressure (p Ｉ ) each higher than the preceding time step, the control unit.

4. A control unit (13) according to any one of claims 1 to 3, the control signal (25) is generated so that the volumetric flow rate (Q) of the breathing air during the expiratory phase (E) follows a given volumetric flow rate curve; and / or A control unit, wherein the volumetric flow rate (Q) of the breathing air during the expiration phase (E) is between 0.02 l / s and 0.20 l / s, preferably between 0.05 l / s and 0.15 l / s, particularly preferably 0.10 l / s.

5. A control unit (13) according to any one of claims 1 to 4, The control signal (25) is an expiratory pressure (p) corresponding to the pressure (p) of the breathing air during the expiratory phase (E). Ｅ ) is generated to follow a given expiratory pressure curve that is at least partially linearly decreasing and / or decreasing in a number of successive time steps, and the expiratory pressure (p Ｅ ) is lower than the previous time step, the control unit.

6. A control unit (13) according to any one of claims 1 to 5, The opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) and / or the closing pressure (p ｃ＿ｌｕ ) (S3) is Identifying characteristic breakpoints in said pressure dependence curve (27); The pressure of the breathing air (p, p) corresponding to the characteristic breakpoint Ｅ , p Ｉ ) is obtained, and the opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) and / or the closing pressure (p ｃ＿ｌｕ ) and a control unit including:

7. A control unit (13) according to claim 6, The characteristic breakpoints are identified based on a characteristic decrease in magnitude of the mean slope of the pressure dependence curve (27) with increasing ventilation duration (t).

8. A control unit (13) according to any one of claims 1 to 7, the inhalation phase (I) and the exhalation phase (E) are successive phases of a single breath; and / or The opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) and / or by evaluating the pressure dependence curve (27) in the first half or first third of the inspiration phase (I) to determine (S3) the closing pressure (p ｃ＿ｌｕ a control unit for evaluating the portion of said pressure dependence curve (27) in the last third of said expiratory phase (E) to determine (S3)

9. A control unit (13) according to any one of claims 1 to 8, The measurement data (11) may represent the amount of the at least one respiratory gas inhaled during the inhalation phase (I) and / or exhaled during the exhalation phase (E) of the patient as a function of the volume of respiratory air (V) (pCO ２ ) and the opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) is further determined by evaluating the portion of the volume-dependence curve (29) related to the inspiratory phase (I), and / or the closing pressure (p ｃ＿ｌｕ ) is further determined by evaluating the portion of said volume-dependence curve (29) related to said expiratory phase (E).

10. A control unit (13) according to any one of claims 1 to 9, The measurement data (11) further show a time-dependent curve (28) of the volumetric flow rate (Q) of the breathing air of the patient in the inspiratory phase (I) and / or the volumetric flow rate (Q) of the breathing air of the patient in the expiratory phase (E) as a function of the ventilation duration (t), and the opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) is further determined by evaluating the portion of the time-dependent curve (28) related to the inspiration phase (I), and / or the closing pressure (p ｃ＿ｌｕ ) is further determined by evaluating the portion of said time-dependent curve (28) related to said expiratory phase (E).

11. A control unit (13) according to any one of claims 1 to 10, The method (M) The opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) and / or the closing pressure (p ｃ＿ｌｕ ), taking into account the pressure (p, p Ｅ , p Ｉ ) determining (S4) a target value for at least one of using said at least one target value to control (S5) said actuator mechanism (5); The control unit further comprises:

12. A control unit (13) according to any one of claims 1 to 11, The measurement data (11) comprises and / or is based on values ​​for at least one of the following variables: The variables are: the amount of the at least one respiratory gas that is inspired by the patient during the inspiration phase (I); and / or The amount of exhaled air (pCO ２ ), the pressure of the breathing air (p, p Ｅ , p Ｉ ), the volume of the breathing air (V), and the volumetric flow rate of the breathing air (Q).

13. A ventilator (1), comprising: a breathing air connection (3) connected to the patient's respiratory system (15) and enabling said patient to be ventilated with breathing air; an actuator mechanism (5) for supplying a flow of breathing air (7) to said breathing air connection (3); a sensor mechanism (9) for generating measurement data (11) relating to said ventilation; A control unit (13) according to any one of claims 1 to 12; An artificial respirator comprising:

14. A computer program for operating a ventilator (1) according to claim 13, comprising: When the computer program is executed by the control unit (13), the computer program causes the control unit (13) to: generating (S1) a control signal (25) for controlling the actuator mechanism (5) to perform a ventilation maneuver in which at least a portion (17, 19) of the respiratory system (15) is opened during an inspiratory phase (I) and / or closed during an expiratory phase (E); Receiving (S2) the measurement data (11), wherein the measurement data (11) includes the pressure of the breathing air (p, p Ｅ , p Ｉ ) of at least one respiratory gas of the patient inhaled during the inhalation phase (I) and / or exhaled during the exhalation phase (E) (pCO ２ ) pressure dependence curve (27); By evaluating the part of the pressure dependence curve (27) related to the inspiratory phase (I), the pressure (p, p) of the breathing air when at least a part (17, 19) of the respiratory system (15) opens is determined. Ｉ ) corresponding to the opening pressure (p ｏ＿ａｗ , p ｏ＿ｌｕ ) (S3) and / or by evaluating the part of the pressure dependence curve (27) related to the expiratory phase (E), the pressure (p, p) of the breathing air when at least a part (17, 19) of the respiratory system (15) is obstructed. Ｅ ) corresponding to the closing pressure (p ｃ＿ｌｕ ) (S3); A computer program comprising instructions for carrying out a method (M) comprising:

15. A computer readable medium having stored thereon the computer program of claim 14.

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