Ventilator control unit

Abstract

This invention provides a control unit that can improve carbon dioxide emissions during patient ventilation more easily and with less burden. [Solution] The ventilator 1 is connected to the patient's respiratory organ 5 and includes a respiratory air connection unit 3 that enables ventilation using respiratory air to be performed on the patient. Furthermore, the ventilator includes an actuator mechanism 7 that supplies a respiratory airflow 9 to the respiratory air connection unit. When the respiratory organ is connected to the respiratory air connection unit, the control unit 17 generates a control signal 23 for controlling the actuator mechanism.

Description

Technical Field

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

Background Art

[0002] In mechanical ventilation, the so-called dead space volume plays an important role. This can generally be understood as the proportion of the tidal volume that remains in the anatomical dead space and the mechanical dead space (also called dead space ventilation) during each breath and thus does not participate in alveolar gas exchange. The dead space is filled with carbon dioxide during the expiratory phase, and this carbon dioxide is inhaled again during the subsequent inspiratory phase. Due to the dead space, an undesirable amount of carbon dioxide can be retained in the body, and in some cases, it may cause hypercapnia or respiratory acidosis. For example, in ARDS patients and COPD patients (ARDS = acute respiratory distress syndrome; COPD = chronic obstructive pulmonary disease), dead space ventilation may account for at least half of the total ventilation per unit time. Thereby, the efficiency of ventilation can be significantly reduced. In principle, reducing dead space ventilation, that is, improving carbon dioxide excretion, can help protect the lungs by enabling the use of a smaller tidal volume and / or a lower airway pressure.

[0003] The dead space can be reduced by reducing the number and / or volume of components connecting the respiratory organ and the ventilator. However, such reduction of the dead space cannot actually be easily achieved. Furthermore, carbon dioxide excretion can be increased using a suitable extracorporeal method such as extracorporeal membrane oxygenation (abbreviated as ECMO) or extracorporeal carbon dioxide removal (abbreviated as ECCO2R). However, these methods are highly invasive and very technically complex.

Summary of the Invention

[0004] An object of the present invention may be to provide a control unit that can improve carbon dioxide removal in patient ventilation more easily and with less burden. A further object of the present invention may be to provide a corresponding computer program, a corresponding computer-readable medium, and a corresponding ventilator. [Means for solving the problem]

[0005] These problems are addressed by the subject matter of the independent claims. Advantageous embodiments of the present invention are shown in the dependent claims, the following description, and the accompanying drawings.

[0006] A first aspect of the present invention relates to a control unit for a ventilator. The ventilator includes a breathing air connection unit connected to the patient's respiratory organs, enabling ventilation using breathing air to the patient. Furthermore, the ventilator includes an actuator mechanism that supplies breathing airflow to the breathing air connection unit. When the respiratory organs are connected to the breathing air connection unit, the control unit generates a control signal for controlling the actuator mechanism in the following manner: namely, that at least one real variable (Istgroesse) related to ventilation, including the pressure and / or volume of breathing air, follows a target curve (Sollverlauf) between a lower limit and an upper limit for each breath, wherein the target curve rises from a lower limit to an upper limit during the inspiratory phase when the patient inhales, and falls from an upper limit to a lower limit during the expiratory phase when the patient exhales, and (during ventilation and / or when controlling the actuator mechanism) the lower limit is periodically repeated The system is configured to switch between a first target value and a second target value smaller than the first target value, according to a returned breathing sequence, wherein each repetition includes one or more first breaths in which at least one real variable decreases to a first target value in the respective expiratory phase, and one or more second breaths in which at least one real variable decreases to a second target value in the respective expiratory phase, and each sequence of a first breath or a directly consecutive first breath precedes each sequence of a second breath or a directly consecutive second breath.

[0007] In this way, functional residual capacity (FRC) can be intentionally and periodically varied over one or more breaths. This can have a positive effect on carbon dioxide efflux. In particular, by controlling each (or multiple) ventilation-related variables in this manner, it is possible to significantly increase average carbon dioxide efflux, although this does not necessarily increase the patient's expiratory volume. Such an increase in tidal volume should be avoided from the perspective of ventilation that is as minimally burdensome as possible.

[0008] The lower limit should be selected in all cases to avoid lung collapse during exhalation. At the same time, the difference between the first and second target values ​​should be selected to be large enough to achieve a therapeutically effective increase in carbon dioxide elimination.

[0009] The lower limit may include, for example, the lower target pressure at which the breathing air pressure should decrease in each expiratory phase. Similarly, the upper limit may include the upper target pressure. The lower target pressure can also be referred to as positive end-expiratory pressure (PEEP). The lower target pressure can be understood as a pressure that is smaller than the upper target pressure.

[0010] Additionally or alternatively, the lower limit may include a lower target volume to which the volume of breathing air should decrease in each exhalation phase. Similarly, the upper limit may include an upper target volume. The lower target volume can be understood as a volume smaller than the upper target volume.

[0011] A ventilator may further include a sensor mechanism that generates measurement data related to ventilation (see also below). The sensor mechanism may include, for example, a pressure sensor that detects the pressure of the breathing air, and / or a flow sensor that detects the volumetric flow rate of the breathing air. In this case, the method may further include receiving measurement data, which may include one or more values ​​(detected during ventilation) of real variables (which may be multiple). Thus, using the measurement data, it is possible to generate control signals so that each real variable, or more precisely its transition, approaches a target curve, in particular by controlling the actuator mechanism in a situational manner. Additionally or alternatively, the measurement data can be used to fit target curves and / or breathing sequences of (e.g., a first target value and / or a second target value).

[0012] In a broad sense, the pressure of the air being breathed can refer to the pressure of the air being breathed within a patient's lungs. Similarly, in a broad sense, the volume of air being breathed can refer to the volume of air-filled lungs.

[0013] At least one repetition of the respiratory sequence may differ from at least one other repetition of the respiratory sequence, for example, with respect to the number and / or type and / or order of breaths. In other words, the respiratory sequence during ventilation can vary from repetition to repetition. This makes it possible to adapt the respiratory sequence to changes in the patient's condition. Alternatively, the respiratory sequence may be the same in each repetition.

[0014] Different repetitions of a breathing sequence can be directly consecutive, at least partially. In this case, the first breath in the current repetition is preceded by the last breath in the previous repetition that precedes the current repetition, and / or the last breath in the current repetition is preceded by the first breath in the next repetition that follows immediately after the current repetition.

[0015] For example, a breathing sequence may include, in at least one repetition or in each repetition, at least two or at least four directly consecutive sequences of first breaths in addition to a second breath, and the sequence of first breaths may precede the second breath immediately.

[0016] This method can be implemented, for example, on a computer.

[0017] The control unit may include data processing means. The data processing means may be implemented as hardware and / or software and / or may include a processor. The processor may be configured to perform a (computer-implemented) method. In addition to the processor, the control unit may include at least one of the following data processing means: namely, memory, a bus system for data communication between memory and the processor, and a data communication interface for wireless and / or wired data communication with peripheral devices. Alternatively, the control unit may be implemented exclusively as hardware, for example, in the form of an ASIC module or an FPGA module.

[0018] A second aspect of the present invention relates to a ventilator. The ventilator includes a respiratory air connection that is connected to the patient's respiratory organs and enables ventilation using respiratory air to the patient. Furthermore, the ventilator includes an actuator mechanism that supplies respiratory airflow to the respiratory air connection. Furthermore, the ventilator includes the control units described above and below. The control units can be integrated, for example, within the housing of the ventilator. Alternatively, an external control unit is also possible.

[0019] A "ventilator" can be understood, for example, as a device that provides invasive and / or non-invasive ventilation to a patient, and / or anesthesia device.

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

[0021] The actuator mechanism may include one or more electro-pneumatic actuators. For example, the actuator mechanism may include one or more blowers and / or one or more electrically controllable valves.

[0022] A third aspect of the present invention relates to a computer program for operating the ventilators described above and below. When the respiratory organs are connected to the breathing air connection, the computer program is executed by the control unit, and the control unit, for example, the processor of the control unit, generates a control signal for controlling the actuator mechanism such that at least one real variable related to ventilation, including the pressure and / or volume of breathing air, follows a target curve between a lower limit and an upper limit for each breath, the target curve rises from the lower limit to the upper limit during the inspiratory phase when the patient inhales, and falls from the upper limit to the lower limit during the expiratory phase when the patient exhales, and (during ventilation and / or acting When controlling the tuner mechanism, the lower limit is switched between a first target value and a second target value smaller than the first target value, according to a periodically repeated breathing sequence, wherein each repetition includes one or more first breaths in which at least one real variable decreases to the first target value in the respective expiratory phase, and one or more second breaths in which at least one real variable decreases to the second target value in the respective expiratory phase, and each sequence of first breaths or directly consecutive first breaths is preceded immediately by each sequence of second breaths or directly consecutive second breaths, and the command to perform this is included.

[0023] A fourth aspect of the present invention relates to a computer-readable medium on which the computer programs described above and below are stored.

[0024] A computer-readable medium can be a volatile or non-volatile data memory. For example, the computer-readable medium can 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 can also be a data communication network or a cloud that enables the download of program code (e.g., via the Internet).

[0025] Note that the features of the control unit described above and below can also be features of a computer program and / or a computer-readable medium (and vice versa).

[0026] Various embodiments of the present invention will be described below. These embodiments should not be understood as limiting the scope of the present invention.

[0027] According to one embodiment, the expiratory phase of each first breath may correspond to a first descending portion of the target curve. Similarly, the expiratory phase of each second breath may correspond to a second descending portion of the target curve. The first portion and the second portion may be adapted to each other in terms of their respective durations and / or amplitudes such that, in each repetition of the breathing sequence, the volume of the patient's exhalation during each second breath is at most the same as the volume of the patient's exhalation during each first breath. In other words, the target curve can be defined such that the patient's tidal volume or minute ventilation does not vary significantly from breath to breath, particularly does not increase significantly during each transition from a first breath to a second breath. This can ensure ventilation with as little burden as possible. The "amplitude" can be understood as the difference between each upper limit and each lower limit (the points at which the respective real variables should decline during the expiratory phase).

[0028] According to one embodiment, the method may further include receiving a stretch value indicating the extensibility of at least a part of the patient's respiratory organs and / or a resistance value indicating the flow resistance of at least a part of the patient's respiratory organs, and using the stretch value and / or the resistance value to determine the respective durations and / or amplitudes of the first portion and / or the second portion. For example, the stretch value can indicate the measured and / or estimated compliance of the patient's lungs, and / or the resistance value can indicate the measured and / or estimated resistance of the patient's airways. This makes it possible to easily adapt each portion of the target curve to various physiological states of the respiratory organs with the aim of ventilation with as little burden as possible.

[0029] According to one embodiment, a product can be calculated by multiplying the stretch value and the resistance value. Then, this product can be used to determine the respective durations and / or amplitudes of the first portion and / or the second portion. This product can be, for example, a time constant. In other words, the stretch value and the resistance value can be integrated as a single value by calculating their product. This can simplify subsequent calculation steps in the control unit.

[0030] According to one embodiment, the durations of the first and / or second parts can be selected such that the greater the product value, the longer the duration. Additionally or alternatively, the amplitudes of the first and / or second parts can be selected such that the greater the product value, the larger the amplitude. This makes it possible to easily scale the duration or amplitude according to the respective conditions of the respiratory organs.

[0031] Additionally or alternatively, the extensibility value and / or resistance value and / or the product of the extensibility value and resistance value can be used to determine the number of second breaths in each repetition of a breathing sequence, and / or to determine the ratio of the number of first breaths to the number of second breaths in each repetition of a breathing sequence.

[0032] According to one embodiment, the method may further include receiving a differential value for each breath and determining the current upper limit value for each breath by adding the differential value to the current lower limit value. It is possible to receive the same differential value for each breath. Alternatively, at least partially different differential values ​​can be received for different breaths. The differential value can be set, for example, by considering the maximum ventilatory pressure and / or tidal volume that is maximally permissible for ventilation in the patient's inspiratory phase. The current lower limit value can be a first target value, a second target value, or other target values, such as a third target value (see below), depending on the type of current breath corresponding to the breathing sequence.

[0033] According to one embodiment, the method may further include receiving alternative difference values ​​for each breath immediately following a second breath, and determining the current value of the upper limit for each breath immediately following a second breath by adding the alternative difference values ​​to the current value of the lower limit instead of the difference values. The lower limit in the inspiratory phase of each breath immediately following a second breath is usually set to a second (lower) target value, depending on the preceding expiratory phase. This reduction in the lower limit can be suitably taken into consideration and, for example, corrected by using situationally adapted alternative difference values ​​when determining the upper limit for each breath.

[0034] In other words, the difference between the lower and upper limits can be intentionally varied with each breath, in relation to the inspiratory and / or expiratory phases. For example, the difference value for each breath immediately following a second breath can be selected to be a certain amount larger than the difference value for each breath immediately preceding the second breath, in particular, so that the upper limits of both breaths are the same magnitude. Alternatively, the same difference value can be received for each breath. In this case, the upper limit can vary (e.g., periodically) depending on its value.

[0035] According to one embodiment, the alternative difference value can be equal to the sum obtained by adding the difference value to the difference between the first target value and the second target value. This makes it possible to ensure that the upper limit in each first breath immediately following the second breath is the same as the upper limit in the first breath preceding the second breath.

[0036] According to one embodiment, the ratio of the number of first breaths to the number of second breaths per unit time, and / or per unit time, for example per minute, in each repetition of the respiratory sequence can be at least 2:1. This ratio can be fixed or can vary with each repetition depending on the patient's condition during ventilation. For example, the ratio of the number of first breaths to the number of second breaths per unit time can be greater than 3:1, 4:1, 5:1, or 5:1. In some cases, a ratio of 1:1 may be appropriate.

[0037] According to one embodiment, the expiratory phase of each second breath can be sustained for a maximum of 3 seconds, preferably a maximum of 1 second. Such a duration has been empirically shown to be sufficiently effective in increasing (average) carbon dioxide efflux without significantly increasing the risk of tidal volume or lung collapse.

[0038] According to one embodiment, the second target value can be 20 percent to 70 percent of the first target value. Ratios within this percentage range have proven to be particularly advantageous in practice.

[0039] According to one embodiment, the lower limit can be switched between a first target value, a second target value, and a third target value between the first and second target values, according to the breathing sequence. In this case, the breathing sequence may further include one or more third breaths in at least one (or each) repetition in which at least one real variable falls to the third target value in the respective expiratory phase. In this case, a third breath or a sequence of directly consecutive third breaths may precede each first breath immediately preceding a second breath or a sequence of directly consecutive second breaths, or each sequence of first breaths immediately preceding a second breath or a sequence of directly consecutive second breaths. The third target value is, for example, a reference value used for most or at least half of the breaths per repetition or per unit time, and can be in particular in the form of a normal PEEP value. Alveolar ventilation can be further improved by starting from this reference value as the lower limit, rising to the first target value, and then decreasing to the second target value in the subsequent expiratory phase.

[0040] For example, a breathing sequence may include, in at least one repetition or in each repetition, at least two or at least four directly consecutive sequences of third breaths in addition to the first and second breaths, with the first breath preceding the second breath, and the sequence of third breaths preceding the first breath.

[0041] According to one embodiment, the third target value can be 50 to 80 percent of the first target value. Ratios within this percentage range have proven to be particularly advantageous in practice.

[0042] According to one embodiment, the ventilator may further include a sensor mechanism that generates measurement data related to ventilation. In this case, the method may further include receiving measurement data at a plurality of consecutive time steps. In this case, the measurement data may include at least one of the following data types: volume data showing the volume of carbon dioxide in the patient's exhaled breath (e.g., carbon dioxide minute ventilation); partial pressure data showing the partial pressure of carbon dioxide in the patient's exhaled breath air and / or in the patient's blood (e.g., end-expiratory); and image data showing the two-dimensional and / or three-dimensional extent of the air-filled region of the patient's lungs. The image data may preferably be generated using electrical impedance tomography (EIT). However, other invasive or non-invasive image generation methods are also possible. Furthermore, the method may include a step of obtaining evaluation data showing an estimated curve of carbon dioxide exhaustion during ventilation (geschaetzten Verlauf) using measurement data from at least two time steps. For example, evaluation data at each time step may be obtained from measurement data at the current time step and at least one time step preceding the current time step.

[0043] Furthermore, the method may include the steps of displaying evaluation data on a display, and / or generating a control signal using the evaluation data (and / or measurement data), and / or fitting a target curve (for example, by changing a first target value and / or a second target value and / or the difference between the first target value and the second target value), in particular, to bring the estimated carbon dioxide emission curve closer to a desired range of values.

[0044] Embodiments of the present invention will be described below with reference to the attached drawings. However, neither this description nor the drawings should be understood as limiting the scope of the present invention. [Brief explanation of the drawing]

[0045] [Figure 1] This is a diagram showing a ventilator according to one embodiment of the present invention. [Figure 2] This figure shows target pressure curves corresponding to a periodically repeating breathing sequence of a first breath and a second breath, used in a method that can be performed by a control unit according to one embodiment of the present invention. [Figure 3] This figure shows target pressure curves corresponding to a periodically repeating breathing sequence of a first breath, a second breath, and a third breath, used in a method that can be performed by a control unit according to one embodiment of the present invention. [Modes for carrying out the invention]

[0046] These diagrams are schematic and not to scale. When the same reference numerals are used in different drawings, these reference numerals refer to the same or equivalent features.

[0047] Figure 1 shows a ventilator 1 that provides invasive and / or non-invasive ventilation to a patient. The ventilator 1 comprises a respiratory air connection 3 connected to the patient's respiratory organ 5, enabling ventilation using respiratory air to the patient, and an actuator mechanism 7 that supplies respiratory airflow 9 to the respiratory air connection 3. For example, the respiratory air connection 3 can be connected to the patient's lungs 10 and / or airway 11 via one or more ventilation tubes and a suitable patient interface such as a mask, nasal cannula, or tube.

[0048] Furthermore, the ventilator 1 includes a sensor mechanism 13 that generates ventilation-related measurement data 15. The sensor mechanism 13 and the actuator mechanism 7 can be connected to a control unit 17, respectively. The control unit 17 can be configured to control the actuator mechanism 7 using the measurement data 15.

[0049] The actuator mechanism 7 may include one or more blowers and / or one or more electrically controllable valves.

[0050] The sensor mechanism 13 may include one or more sensors, for example, at least one of the following: a carbon dioxide sensor for detecting the partial pressure of carbon dioxide in the patient's breathing air and / or blood; an oxygen sensor for detecting the partial pressure of oxygen in the patient's breathing air and / or blood; a flow sensor for detecting the volumetric flow rate of breathing air; a pressure sensor for detecting the pressure of breathing air; or a plurality of electrodes for measuring changes in electrical resistance in the patient's lung tissue, for example, as part of electrical impedance tomography.

[0051] Therefore, the measurement data 15 may include at least one of the following data types: volume data showing the volume of carbon dioxide and / or oxygen in the patient's exhaled breath (e.g., minute ventilation), partial pressure data showing the partial pressure of carbon dioxide and / or oxygen (e.g., end-expiratory), and image data showing the two-dimensional and / or three-dimensional extent of the air-filled area in the patient's lungs.

[0052] Image data can, for example, encode the brightness and / or color of each pixel (also called a pixel) in a two-dimensional or three-dimensional pixel matrix with respect to one or more cross-sections of a lung 10. Here, the brightness and / or color may vary depending on the measured electrical resistance corresponding to each pixel. For example, to encode the brightness of red, green, and blue, each pixel can be assigned three values ​​from 0 percent to 100 percent or 0 to 255 (in the case of 8 bits). However, other color spaces and / or other types of encoding are also possible.

[0053] The control unit 17 may include a processor 19 and a memory 21 that can store a computer program for operating the ventilator 1. The processor 19 may be configured to perform the following method of operating the ventilator 1 by executing the computer program.

[0054] In the first step, a control signal 23 is generated to control the actuator mechanism 7 such that at least one real variable related to ventilation, which may include the pressure p and / or volume of the breathing air, follows a target curve 25 (see Figures 2 and 3) between a lower limit 27 and an upper limit 29 for each breath. In this example, the real variable is the pressure p of the breathing air. The target curve 25 can rise from a lower limit 27 (here, the lower target pressure) to an upper limit 29 (here, the upper target pressure) during the inspiratory phase when the patient inhales, and descend from an upper limit 29 to a lower limit 27 during the expiratory phase when the patient exhales.

[0055] In the second step, the lower limit 27 is switched between a first target value v1 (here, a first target pressure value) and a second target value v2 (here, a second target pressure value) which is smaller than the first target value v1, according to a given periodically repeated breathing sequence. The breathing sequence may include, in each repetition, one or more first breaths I in which the pressure p decreases to the first target value v1 in each expiratory phase, and one or more second breaths II in which the pressure p decreases to the second target value v2 in each expiratory phase. Here, each sequence of second breaths II or a directly consecutive sequence of second breaths II may precede immediately before a sequence of first breaths I or a directly consecutive sequence of first breaths I.

[0056] The first and second steps can be performed simultaneously or with a time delay.

[0057] In the example shown in Figure 2, each second respiration II is preceded by a sequence of four (or three) direct, consecutive first respirations I. Therefore, for example, the ratio of the number of first respirations I to the number of second respirations II per minute in each repetition is 4 (or 3) to 1. However, other ratios, such as 1 to 1, 2 to 1, or 5 to 1, are also possible. The second target value v2 is preferably 20 to 70 percent of the first target value v1.

[0058] As shown in Figure 3, the breathing sequence may further include one or more third breaths III in each repetition in which the pressure p decreases to a third target value v3 (here, a third target pressure value) in each expiratory phase. The third target value v3 (here, 8 cmH2O) can be a value between the first target value v1 (here, 12 cmH2O) and the second target value v2 (here, 5 cmH2O). Preferably, the third target value v3 is 50 percent to 80 percent of the first target value v1.

[0059] Therefore, the lower limit 27 can be switched between a first target value v1, a second target value v2, and a third target value v3, according to the respiratory sequence. In this example, each first breath I that precedes the second breath II is preceded by a sequence of two directly consecutive third breaths III. Thus, for example, the ratio of the number of third breaths III to the number of first breaths I and the number of second breaths II per minute in each repetition is 2:1:1. However, another preferred ratio, such as 1:1:1, is also possible. Furthermore, this ratio may be continuously varied during ventilation according to the patient's condition.

[0060] The third target value v3 can be, for example, the normal PEEP value used for most or at least half of the respirations per repetition or per unit time. Alveolar ventilation can be further improved by raising the lower limit 27 from the normal PEEP value to the first target value v1, and then lowering it to the second target value v2 in the subsequent expiratory phase.

[0061] The expiratory phase of each first breath I can correspond to the descending first portion of the target curve 25, the expiratory phase of each second breath II can correspond to the descending second portion of the target curve 25, and the expiratory phase of each third breath III can correspond to the descending third portion of the target curve 25. These portions of different breath types I, II, and III can be adapted to each other in terms of their respective durations and / or amplitudes in each repetition of the breathing sequence, so that the volume of the patient's exhaled air in each breath remains largely constant across multiple breaths, and in particular, does not increase significantly at each transition from the first breath I to the second breath II. Thus, ventilation can be ensured that is as unburdensome as possible, even though carbon dioxide emissions increase significantly on average.

[0062] To enable the adaptation of the duration and / or amplitude (particularly the second portion) of each portion to the individual patient's condition, in an optional step, a distensibility value indicating the extensibility of at least a portion of the respiratory organ 5 (e.g., compliance of the lung 10) can be received. Additionally or alternatively, a resistance value indicating the flow resistance (e.g., resistance of the airway 11) in at least a portion of the respiratory organ 5 can be received. The distensibility value and the resistance value may be measured and / or estimated values, respectively (e.g., using one or more suitable sensors of the sensor mechanism 13).

[0063] For example, the extensibility value and the resistance value can be multiplied together. The resulting product can then be used, for example, in the form of a time constant to determine the duration and / or amplitude of the first and / or second parts, respectively. In this case, a larger product value can be selected to result in a longer duration. Similarly, a larger product value can be selected to result in a larger amplitude. This makes it possible to easily scale the duration or amplitude according to the respective states of the respiratory organ 5.

[0064] Additionally or alternatively, the extensibility value and / or resistance value and / or the product of the extensibility value and resistance value can be used to determine the number of second breaths (II) in each repetition of a breathing sequence, and / or to determine the ratio of the number of second breaths (II) to the number of first breaths (I) and / or third breaths (III) in each repetition of a breathing sequence.

[0065] In practice, it has been proven that a maximum duration of 1 to 3 seconds is appropriate for the expiratory phase of each second breath (II). However, other values ​​may be possible depending on the patient's condition.

[0066] The upper limit value of 29 can be determined, for example, by receiving a suitable differential value (in this case, a suitable differential pressure value) for each individual respiration I, II, or III, and then adding this differential value to the current values ​​v1, v2, or v3 of the lower limit 27 to obtain the current value of the upper limit 29 for each respiration I, II, or III.

[0067] The difference value may be the same for each breath. Alternatively, for different breaths, it may be possible to receive difference values ​​that are at least partially different, i.e., differ in magnitude.

[0068] For example, for each breath I or III immediately following the second breath II, it is possible to receive an alternative differential value (here, an alternative differential pressure value) whose magnitude is appropriately different from the (normal) differential value, for example, a value that is larger than the (normal) differential value. Then, the current value of the upper limit 29 for each breath I or III can be determined by adding the alternative differential value instead of the (normal) differential value to the respective current value of the lower limit 27 (here, v2). For example, the alternative differential value may be equal to the sum obtained by adding the (normal) differential value to the difference between the first target value v1 and the second target value v2.

[0069] The measurement data 15 can be received, for example, in multiple directly consecutive time steps at a frequency of, for example, 1 Hz to 1000 Hz, preferably 100 Hz to 300 Hz. In a further optional step, evaluation data showing an estimated, for example, time-dependent curve of carbon dioxide emissions during ventilation can be obtained from the measurement data 15 of different time steps. The evaluation data can then be displayed on a display, for example, in numerical and / or graphical form, for monitoring. Additionally or alternatively, the evaluation data can be used to generate control signals 23 and / or to fit at least a portion of the target curve 25 by changing, for example, at least a portion of the target values ​​v1, v2, and v3. For example, the target curve 25 (or at least a portion thereof) at the current time step can be fitted so that the estimated curve of carbon dioxide emissions at future time steps is within a desired value range, or at least closer to the desired value range at future time steps than at the current time step.

[0070] Functional residual capacity (FRC) is not constant in healthy individuals, but fluctuates at a low frequency of approximately once every 500 breaths, and this is known to affect gas exchange. The ventilation modes described above take this physiological behavior into account, but accelerate such fluctuations in order to achieve additional carbon dioxide removal during mechanical ventilation. For this purpose, the functional residual capacity can be repeatedly and controlledly reduced for short periods every few breaths. Therefore, these ventilation modes can also be called ventilation with variable FRC. Such ventilation modes can be used as an independent ventilation mode in a ventilator or in combination with other devices to actively reduce anatomical and mechanical dead space.

[0071] The ventilation mode can be one in which the FRC automatically and periodically decreases relative to the baseline value by lowering the PEEP value, for example, during the duration of a single breath. Therefore, the PEEP decrease is particularly short, e.g., less than 1 second. Such a PEEP decrease may occur, for example, every 2 to 4 breaths. Further decreases in FRC lead to further expulsion of carbon dioxide from the small airways and alveolar compartments. Since the carbon dioxide in these special breaths originates mainly from the alveoli, alveolar ventilation is enhanced without creating dead space in the airways.

[0072] To avoid lung collapse, the decrease in FRC should be kept to a very short duration. Generally, the duration of the FRC decrease should be well below the time constants of airway collapse and / or alveolar collapse. After a series of normal breaths at baseline PEEP, the PEEP level should be reduced for each breath to allow the FRC to decrease. This temporary decrease in FRC can be compensated for during the subsequent inspiratory phase. Therefore, the ventilator needs to be able to provide a sufficiently high volumetric flow rate for inspiration to not only restore the FRC but also to supply the desired tidal volume.

[0073] For example, the ventilation mode can be configured to increase or decrease the PEEP value by approximately 5 cmH2O from one breath to the next, while providing a sufficiently high respiratory airflow during the inspiratory phase so that changes in FRC are rapidly compensated for and normal tidal volume is maintained. The pressure difference between the upper and lower target pressure limits should be less than 15 mmHg to enable ventilation with as little strain on the lungs as possible.

[0074] The FRC (Frequency Rate Control) can be manually adjusted in terms of the number of breaths per unit time, for example, per minute, and / or amplitude. Alternatively, this adjustment can be performed automatically by the ventilator.

[0075] The ventilation mode can automatically generate a sequence of FRC changes at a constant tidal volume, depending on the respective difference values. Here, the total expiratory time ventilation includes a first part corresponding to the product of tidal volume and respiratory rate, and a second part corresponding to the additional expiratory volume based on the additional PEEP reduction. For example, a standard minute ventilation of 6.75 l / min (product of tidal volume of 450 ml and respiratory rate of 15 breaths / min) can be set, and in addition, a repeated short-duration PEEP reduction can be set, first decreasing from 10 cmH2O to 5 cmH2O and then returning to 10 cmH2O. Assuming that such a PEEP reduction generates an additional 200 ml of exhalation every four breaths, an additional ventilation of approximately 1 l / min (200 ml per minute x 5 breaths) can be achieved, resulting in a total minute ventilation of 7.75 l / min. In other words, the smaller the ratio of normal breathing to special breathing (with PEEP reduction), and the greater the PEEP reduction, the greater the effect of additional carbon dioxide elimination.

[0076] By using a respiratory sequence as illustrated in Figure 3, the amplitude of changes in FRC can be further increased, thereby improving alveolar ventilation. For example, the lower limit 27 can fluctuate regularly within ±3 cmH2O to 4 cmH2O from the baseline PEEP value. The baseline PEEP value should be adjusted so that the lungs do not collapse during exhalation. If the baseline PEEP value is 8 cmH2O and the ratio is 1:1:1, the value of the lower limit 27 can fluctuate periodically, for example, 8-12-4-8-12-4-8-12-4 (if the ratio is 2:1:1, for example, 8-8-12-4-8-8-12-4-8-8-12-4). Such a decrease in PEEP (in this case, by 8 cmH2O) can significantly increase carbon dioxide elimination. This makes it possible to reduce the tidal volume to a minimum when FRC fluctuates.

[0077] Finally, note that terms such as "equip," "include," "possess," and "accompany" do not exclude other elements or steps, and words that do not specify a quantity do not exclude the possibility of being plural.

[0078] Furthermore, it should be noted that any feature or step described with reference to one of the embodiments described above may be used in combination with any feature or step described with reference to another of the embodiments described above.

[0079] Reference numerals in the claims should not be understood as limiting the scope of subject matter defined by the claims. [Explanation of Symbols]

[0080] 1 ventilator 3. Breathing air connection 5 Respiratory organs 7. Actuator mechanism 9. Breathing airflow 10 Lungs 11 Airway 13 Sensor mechanism 15 Measurement data 17 Control Unit 19 processors 21 memory 23 Control signals 25 Target curve 27 lower limit 29 upper limit p pressure t time v1 First target value v2 Second target value v3 Third target value I. First Breath II. Second Breath III. The Third Breath

Claims

1. A control unit (17) of a ventilator (1), wherein the ventilator (1) is A respiratory air connection unit (3) is connected to the patient's respiratory organ (5) and enables ventilation using respiratory air to be performed on the patient, An actuator mechanism (7) that supplies a breathing airflow (9) to the breathing air connection part (3), Equipped with, When the respiratory organ (5) is connected to the respiratory air connection part (3), the control unit (17) uses the following method, namely, The method involves generating a control signal (23) for controlling the actuator mechanism (7) such that at least one real variable related to the ventilation, including the pressure (p) and / or volume of the breathing air, follows a target curve (25) between a lower limit (27) and an upper limit (29) for each breath (I, II, III), wherein the target curve (25) rises from the lower limit (27) to the upper limit (29) during the inspiratory phase when the patient inhales, and falls from the upper limit (29) to the lower limit (27) during the expiratory phase when the patient exhales. The lower limit (27) is switched between a first target value (v1) and a second target value (v2) smaller than the first target value (v1) according to a periodically repeating breathing sequence, wherein each repetition includes one or more first breaths (I) in which the at least one real variable decreases to the first target value (v1) in the expiratory phase, and one or more second breaths (II) in which the at least one real variable decreases to the second target value (v2) in the expiratory phase, and each sequence of second breaths (II) or directly consecutive second breaths (II) is preceded by a sequence of first breaths (I) or directly consecutive first breaths (I). A control unit configured to perform the following actions.

2. The control unit (17) according to claim 1, wherein the expiratory phase of each first breath (I) corresponds to a descending first portion of the target curve (25), and the expiratory phase of each second breath (II) corresponds to a descending second portion of the target curve (25), and the duration and / or amplitude of the first portion and the second portion are adapted to each other such that in each repetition of the breathing sequence, the volume of the patient's exhaled breath during each second breath (II) is at most the same as the volume of the patient's exhaled breath during each first breath (I).

3. The aforementioned method, Receiving an extensibility value indicating the extensibility of at least a portion (10, 11) of the patient's respiratory organ (5), and / or a resistance value indicating the flow resistance in at least a portion (10, 11) of the patient's respiratory organ (5), Using the aforementioned extensibility value and / or resistance value, the duration and / or amplitude of the first portion and / or the second portion, respectively, are determined. The control unit (17) according to claim 2, further comprising:

4. The control unit (17) according to claim 3, wherein the product is obtained by multiplying the extensibility value and the resistance value, and the respective duration and / or amplitude is determined using the product.

5. The durations of each of the above are selected such that they become longer as the value of the above product increases, and / or The control unit (17) according to claim 4, wherein each of the amplitudes is selected to increase as the value of the product increases.

6. The aforementioned method, The system receives the difference value for each respiration (I, II, III), The current value of the upper limit (29) for each of the respirations (I, II, III) is determined by adding the difference value to the current value of the lower limit (27) (v1, v2, v3). A control unit (17) according to any one of claims 1 to 5, further comprising:

7. The aforementioned method, Receiving alternative difference values ​​for each breath (I, III) immediately following the second breath (II), The current value of the upper limit (29) for each of the breaths (I, III) immediately following the second breath (II) is determined by adding the alternative difference value to the current value (v2) of the lower limit (27) instead of the difference value. The control unit (17) according to claim 6, further comprising:

8. The control unit (17) according to claim 7, wherein the alternative difference value is equal to the sum obtained by adding the difference value to the difference between the first target value (v1) and the second target value (v2).

9. The ratio of the number of first breaths (I) to the number of second breaths (II) in each repetition of the breathing sequence is at least 2 to 1, and / or The expiratory phase of each second breath (II) lasts for a maximum of 3 seconds, preferably a maximum of 1 second, and / or The control unit (17) according to any one of claims 1 to 8, wherein the second target value (v2) is 20 percent to 70 percent of the first target value (v1).

10. The lower limit (27) is switched between the first target value (v1), the second target value (v2), and a third target value (v3) between the first target value (v1) and the second target value (v2), according to the breathing sequence. The breathing sequence further includes one or more third breaths (III) in which, in at least one repetition, the at least one real variable decreases to the third target value (v3) during the expiratory phase. A control unit (17) according to any one of claims 1 to 9, wherein each first breath (I) precedes immediately before a second breath (II) or a sequence of directly consecutive second breaths (II), or each sequence of first breaths (I) precedes immediately before a second breath (II) or a sequence of directly consecutive second breaths (II), wherein a sequence of third breaths (III) or a sequence of directly consecutive third breaths (III) precedes immediately before each sequence of second breaths (II) or a sequence of directly consecutive second breaths (II).

11. The ventilator (1) further comprises a sensor mechanism (13) that generates measurement data (15) related to ventilation, The aforementioned method, Receiving the measurement data (15) in a plurality of consecutive time steps, wherein the measurement data (15) includes at least one data type from among volume data indicating the volume of carbon dioxide in the patient's exhaled breath, partial pressure data indicating the partial pressure of carbon dioxide in the patient's exhaled breath and / or in the patient's blood, and image data indicating the two-dimensional and / or three-dimensional extent of the air-filled region of the patient's lungs (9), Using the measurement data (15) from at least two time steps, evaluation data showing an estimated curve of carbon dioxide emissions during ventilation is obtained. A control unit (17) according to any one of claims 1 to 10, further comprising:

12. The aforementioned method, The control unit (17) according to claim 11, further comprising using the evaluation data to generate the control signal (23) and / or fitting the target curve (25) so that the estimated curve of carbon dioxide emissions approaches a desired range of values.

13. A respiratory air connection unit (3) is connected to the patient's respiratory organ (5) and enables ventilation using respiratory air to be performed on the patient, An actuator mechanism (7) that supplies a breathing airflow (9) to the breathing air connection part (3), A control unit (17) according to any one of claims 1 to 12 and A ventilator (1) equipped with the following features.

14. A computer program for operating the ventilator (1) according to claim 13, wherein, when the respiratory organ (5) is connected to the respiratory air connection part (3), the computer program is executed by the control unit (17), and the control unit (17) is instructed to perform the following actions, namely, The method involves generating a control signal (23) for controlling the actuator mechanism (7) such that at least one real variable related to the ventilation, including the pressure (p) and / or volume of the breathing air, follows a target curve (25) between a lower limit (27) and an upper limit (29) for each breath (I, II, III), wherein the target curve (25) rises from the lower limit (27) to the upper limit (29) during the inspiratory phase when the patient inhales, and falls from the upper limit (29) to the lower limit (27) during the expiratory phase when the patient exhales. The lower limit (27) is switched between a first target value (v1) and a second target value (v2) smaller than the first target value (v1) according to a periodically repeated breathing sequence, wherein each repetition includes one or more first breaths (I) in which the at least one real variable decreases to the first target value (v1) in the expiratory phase, and one or more second breaths (II) in which the at least one real variable decreases to the second target value (v2) in the expiratory phase, and each sequence of second breaths (II) or directly consecutive second breaths (II) is preceded immediately by a sequence of first breaths (I) or directly consecutive first breaths (I). A computer program that contains instructions to execute something.

15. A computer-readable medium storing the computer program described in claim 14.

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