Control unit for a ventilation system for the invasive ventilation of a patient

Abstract

The invention relates to a ventilation system (1) for the invasive ventilation of a patient, comprising: a tracheal pressure sensor (3) for detecting a tracheal pressure as a respiratory air pressure in the trachea (5) of the patient; a ventilation tube (7) that can be inserted into the trachea (5) of the patient; and a ventilator (9) for generating a respiratory air flow (11, 11a, 11b) through the ventilation tube (7) inserted into the trachea (5) of the patient, such that the patient is ventilated. A control unit (13) for the ventilation system (1) is designed to carry out a control method when the patient is connected to the ventilator (9) via the ventilation tube (7), wherein the control method comprises controlling the tracheal pressure in a plurality of successive time steps. Each time step comprises: receiving an actual value (19) of the tracheal pressure determined by means of the tracheal pressure sensor (3) and a setpoint value (21) associated with the tracheal pressure; determining a tracheal pressure deviation by comparing the actual value (19) with the setpoint value (21); and generating a control signal (23) for controlling the ventilator (9) in order to adjust the respiratory air flow (11, 11a, 11b) in such a way that the tracheal pressure deviation is reduced.

Description

[0001] Control unit for a ventilation system for the invasive ventilation of a patient

[0002] Technical field

[0003] The invention relates to a control unit for a ventilation system. Furthermore, the invention relates to a computer program executable by the control unit, a corresponding computer-readable medium, and a ventilation system with such a control unit.

[0004] State of the art

[0005] In mechanical ventilation, the so-called dead space volume plays a crucial role. This can generally be understood as the portion of the tidal volume that remains within an anatomical and instrumental dead space during each breath (also called dead space ventilation) and thus does not participate in alveolar gas exchange. The dead space fills with carbon dioxide during each exhalation, which is then re-inhaled during the following inhalation. Due to the dead space, carbon dioxide can be retained in the body to an undesirable degree, which in some cases can cause hypercapnia or respiratory acidosis. For example, in patients with ARDS and COPD (ARDS = acute respiratory distress syndrome; COPD = chronic obstructive pulmonary disease), dead space ventilation can account for at least half of the total ventilation per unit of time. This can significantly reduce the efficiency of ventilation.In principle, a reduction in dead space ventilation, i.e., an improvement in carbon dioxide elimination, can have a protective effect on the lungs because this allows the use of a lower tidal volume and / or a lower airway pressure.

[0006] Dead space can be reduced, for example, by decreasing the number and / or volume of components connecting the respiratory system to the ventilator. However, such a reduction in dead space is difficult to implement in practice. Furthermore, it is possible to increase carbon dioxide removal using a suitable extracorporeal method, such as extracorporeal membrane oxygenation (ECMO) or extracorporeal carbon dioxide removal (ECCO2R). These methods, however, are highly invasive and technically very complex.

[0007] In non-invasive ventilation via a mask, a continuous flushing of unwanted carbon dioxide from the dead space can be achieved by means of a controlled leak in the ventilation circuit, for example, in the form of a corresponding opening in the mask. Such a leak is not readily possible with invasive ventilation.

[0008] Disclosure of the invention

[0009] One object of the invention can be seen as providing a control unit that makes it possible to improve carbon dioxide elimination during invasive ventilation of a patient in a simple and gentle manner. A further object of the invention can be seen as providing a corresponding computer program, a corresponding computer-readable medium, and a corresponding ventilation system.

[0010] These problems are solved by the subject matter of the independent claims. Advantageous embodiments of the invention are set out in the dependent claims, the following description, and the accompanying figures.

[0011] A first aspect of the invention relates to a control unit for a ventilation system for the invasive ventilation of a patient. The ventilation system comprises a tracheal pressure sensor for detecting tracheal pressure as the breathing pressure in the patient's trachea (hereinafter referred to as the trachea), a breathing tube that can be inserted into the trachea, and a ventilator for generating a flow of air through the breathing tube inserted into the trachea, thus ventilating the patient. The control unit is configured to execute a control procedure (for example, a computer-implemented one) when the patient is connected to the ventilator via the breathing tube. The control procedure comprises controlling the tracheal pressure in several successive phases. Each phase comprises the following procedure steps: receiving an actual value of the tracheal pressure determined by the tracheal pressure sensor and a value that is

[0012] Tracheal pressure setpoint; determining a tracheal pressure deviation by comparing the actual value with the setpoint; generating a control signal to control the ventilator to adjust the airflow so that the tracheal pressure deviation is reduced.

[0013] Such a control unit enables – especially in combination with targeted passive and / or active ventilation described below by means of an (additional) ventilation catheter inserted into the trachea – significantly more efficient carbon dioxide elimination during exhalation compared to other pressure-based ventilation methods, due to the tracheal pressure-based ventilation control, so that unwanted rebreathing of carbon dioxide from the dead space is avoided during inhalation.

[0014] Tracheal pressure can be understood as the atmospheric pressure at a point within the trachea between the larynx and the tracheal bifurcation. It is possible that the tracheal pressure at this point is measured using a tracheal pressure sensor to obtain the actual values. The measurement point can be significantly closer to the tracheal bifurcation than to the larynx. For example, the measurement point could be located in the lower third, lower quarter, or lower eighth of the section of the trachea connecting the larynx to the tracheal bifurcation, adjacent to the bifurcation.

[0015] Controlling (and / or monitoring) tracheal pressure can, for example, be done continuously or at least intermittently with each breath during an inhalation phase, when the patient is supposed to inhale, and / or during an exhalation phase, when the patient is supposed to exhale.

[0016] The term "journal" can generally be understood as a single iteration of the control procedure. The time interval between two consecutive journals can be, for example, between 1 minute and 1 second, between 1 second and 100 milliseconds, between 100 milliseconds and 10 milliseconds, or between 10 milliseconds and 1 millisecond. However, the time interval can also be longer than 1 minute, shorter than 1 millisecond, or as long as a single breath or a phase of a single breath, such as an inhalation or exhalation phase.

[0017] The term "actual value" can refer to a value measured and / or estimated using the tracheal pressure sensor. Each setpoint can be read, for example, from the memory of the ventilation system, particularly the ventilator. It is also possible to receive the setpoint from external storage and / or a data communication network such as a LAN, WLAN, or WAN. The setpoints received in different journals may at least partially coincide and / or at least partially differ from one another.

[0018] The tracheal pressure deviation can be determined, for example, by calculating the difference between the actual value and the target value of the respective time step.

[0019] The control unit can include data processing means. These means can be implemented as hardware and / or software and / or include a processor. The processor can be configured to execute the (computer-implemented) control procedure. In addition to the processor, the control unit can include at least one of the following data processing means: memory, a bus system for data communication between the memory and the processor, or a data communication interface for wireless and / or wired data communication with peripheral devices. Alternatively, the control unit can be implemented exclusively as hardware, for example, in the form of an ASIC or FPGA chip.

[0020] A second aspect of the invention relates to a ventilation system for the invasive ventilation of a patient. The ventilation system comprises: a tracheal pressure sensor for detecting tracheal pressure as the breathing pressure in the patient's trachea; a breathing tube that can be inserted into the patient's trachea; a ventilator for generating a flow of air through the breathing tube inserted into the patient's trachea, thus ventilating the patient; and a control unit as described above and below.

[0021] The term "ventilator" can also refer to an anesthesia machine.

[0022] The ventilator can include one or more electropneumatic actuators for generating the breathing airflow. Such an actuator can be, for example, a blower or an electrically controlled valve and / or be controllable by the control unit. A third aspect of the invention relates to a computer program for operating the ventilation system described above and below. The computer program includes commands that, when the computer program is executed by the control unit, cause the control unit of the ventilation system—for example, a processor of the control unit—to execute the (computer-implemented) control procedure described above and below.

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

[0024] The computer-readable medium can be volatile or non-volatile data storage. For example, the computer-readable medium can be a hard drive, a USB storage device (USB = Universal Serial Bus), RAM (random-access memory), ROM (read-only memory), EPROM (erasable programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), flash memory, or a combination of at least two of these. The computer-readable medium can also be a data communication network that allows the downloading of program code (e.g., via the internet) or a cloud.

[0025] It should be noted that features of the control unit described above and below may also be features of the computer program and / or the computer-readable medium (and vice versa).

[0026] The following describes various embodiments of the invention. These embodiments are not to be understood as limiting the scope of the invention.

[0027] According to one embodiment, controlling the tracheal pressure in each magazine can further include: receiving a ventilation pressure reading indicating the ventilation pressure applied to a pressure port of the ventilator, with the endotracheal tube connected to the ventilator via the pressure port during patient ventilation; checking whether the actual tracheal pressure reading is plausible using the ventilation pressure reading; if the reading is plausible, using the reading to determine the tracheal pressure deviation, and / or, if the reading is implausible, discarding the reading. The ventilation pressure reading may, for example, have been determined using a ventilation pressure sensor to detect the ventilation pressure. Such plausibility checks can prevent significant errors in controlling the tracheal pressure, for example, due to (random) measurement inaccuracies.

[0028] According to one embodiment, the setpoints received in the multiple successive magazines can be values ​​of a predetermined tracheal pressure profile (hereinafter referred to as the tracheal pressure profile). The control signal in each magazine can be generated such that the tracheal pressure follows the tracheal pressure profile with each breath of the patient. The tracheal pressure profile can rise from a lower limit to an upper limit during an inhalation phase, when the patient is inhaling, and fall from the upper limit to the lower limit during an exhalation phase, when the patient is exhaling. The lower limit can be switched (during patient ventilation) between a first setpoint and a second setpoint, which is smaller in absolute value than the first setpoint, according to a (predefined) breathing sequence that repeats cyclically (during patient ventilation).The breathing sequence can, in each repetition, include one or more first breaths, during which the tracheal pressure is intended to fall to the first setpoint during exhalation, and one or more second breaths, during which the tracheal pressure is intended to fall to the second setpoint during exhalation. Each second breath or sequence of immediately consecutive second breaths can be immediately preceded by a first breath or a sequence of immediately consecutive first breaths.

[0029] In this way, a targeted periodic fluctuation of the functional residual capacity (FRC) can be achieved over one or more breaths. This, in turn, can have a beneficial effect on carbon dioxide elimination.

[0030] In particular, such control of tracheal pressure allows for a significant increase in average carbon dioxide elimination without necessarily increasing the volume exhaled by the patient. Such an increase in tidal volume should be avoided in the interest of the gentlest possible ventilation.

[0031] The term "course," as used in "tracheal pressure course," can refer to a course that is at least partially constant and / or at least partially variable (linearly or non-linearly). The lower limit should always be chosen to prevent lung collapse during exhalation. Simultaneously, the difference between the first and second setpoint values ​​should be large enough to achieve a therapeutically effective increase in carbon dioxide elimination.

[0032] The lower limit to which the tracheal pressure should fall in each exhalation phase (more precisely at the end of each exhalation phase) can also be referred to as positive end-expiratory pressure, or PEEP for short.

[0033] It is possible that at least one repetition of the breathing sequence differs from at least one other repetition of the breathing sequence, for example, in the number and / or type and / or order of the breaths. In other words, the breathing sequence can be varied from repetition to repetition when ventilating the patient. This allows the breathing sequence to be adapted to changes in the patient's health condition. Alternatively, the breathing sequence can be the same in every repetition.

[0034] The various repetitions of the breathing sequence during patient ventilation can follow each other, at least partially. The first breath in a current repetition can be immediately preceded by the last breath in an earlier repetition that immediately precedes the current repetition, and / or the last breath in a current repetition can be immediately followed by the first breath in a later repetition that immediately follows the current repetition.

[0035] According to one embodiment, the exhalation phase of each first breath can be associated with a descending first section of the tracheal pressure curve. Similarly, the exhalation phase of each second breath can be associated with a descending second section of the tracheal pressure curve. The first and second sections can be coordinated in their respective duration and / or amplitude in each repetition of the breathing sequence such that the volume exhaled by the patient in each second breath is at most as large as the volume exhaled by the patient in each first breath.

[0036] In other words, the tracheal pressure profile can be defined such that the patient's tidal volume does not change significantly from breath to breath, and in particular does not increase significantly during each transition from the first to the second breath. This ensures the gentlest possible ventilation. "Amplitude" can be understood as the difference between the respective upper limit and the respective lower limit (to which the tracheal pressure should fall during exhalation).

[0037] According to one embodiment, the control method may further include: receiving a distensibility value indicating the distensibility of at least one part of the patient's respiratory apparatus, and / or a resistance value indicating flow resistance in at least one part of the patient's respiratory apparatus; determining the respective duration and / or amplitude of the first sections and / or the second sections using the distensibility value and / or the resistance value.

[0038] For example, the extensibility value can indicate a measured and / or estimated compliance of the patient's lungs, and / or the resistance value can indicate a measured and / or estimated resistance of the patient's airways. This allows for easy adjustment of the respective sections of the tracheal pressure curve to different physiological states of the respiratory system, with a view to providing the gentlest possible ventilation.

[0039] According to one embodiment, a product can be calculated by multiplying the extensibility value and the resistance value. This product can then be used to determine the respective duration and / or amplitude of the first and / or second sections.

[0040] The product could, for example, be a time constant. In other words, the ductility value and the resistance value can be combined into a single value by calculating their product. This can simplify subsequent calculations in the control unit.

[0041] According to one embodiment, the duration of the first and / or second sections can be chosen to be longer as the product increases. Additionally or alternatively, the amplitude of the first and / or second sections can be chosen to be greater as the product increases. This allows for simple scaling of the duration or amplitude depending on the current state of the respiratory system. Additionally or alternatively, the extensibility value and / or the resistance value and / or the product of the extensibility value and the resistance value can be used to determine the number of second breaths in each repetition of the breathing sequence and / or to determine the ratio of first breaths to second breaths in each repetition of the breathing sequence.

[0042] According to one embodiment, the control method may further include: receiving a difference value for each breath; determining an actual upper limit value for the respective breath by adding the difference value to an actual lower limit value.

[0043] It is possible that the same differential value is received for each breath. Alternatively, different differential values ​​may be received, at least partially, for different breaths. The differential value may, for example, have been set taking into account a maximum ventilation pressure and / or volume with which the patient may be ventilated during the inhalation phase. Depending on the type of breath being received, the current lower limit value may be the first setpoint, the second setpoint, or another setpoint, such as a third setpoint (see below), according to the breath sequence.

[0044] According to one embodiment, the control method may further include: receiving an alternative difference value for each breath immediately following a second breath; determining an actual upper limit value for each breath immediately following the second breath by adding the alternative difference value instead of the difference value to an actual lower limit value.

[0045] The lower limit in the inhalation phase of each breath immediately following the second breath is normally set to the second (lower) setpoint value, corresponding to the preceding exhalation phase. This reduction can be appropriately taken into account, for example, compensated for, when determining the upper limit for the respective breath using a suitably adjusted alternative difference value.

[0046] In other words, the difference between the lower limit and the upper limit can be

[0047] The limit can be specifically varied depending on the breath, in relation to the inhalation and / or exhalation phase. For example, the difference value for each breath immediately following a second breath can be chosen to be a certain amount greater than for each breath immediately preceding a second breath, specifically such that the upper limit is the same for these two breaths. Alternatively, the same difference value can be received for each breath. In this case, the upper limit can fluctuate accordingly (e.g., periodically).

[0048] According to one embodiment, the alternative difference value can be equal to a sum obtained by adding the difference values ​​to the difference between the first setpoint and the second setpoint. This ensures that the upper limit in every first breath immediately following a second breath is the same as in every first breath immediately preceding a second breath.

[0049] According to one embodiment, the ratio of the number of first breaths to the number of second breaths in each repetition of the breathing sequence and / or per unit of time, for example, per minute, can be at least two to one. The ratio can be fixed or varied from repetition to repetition during ventilation, depending on the patient's condition. For example, the ratio of the number of first breaths to the number of second breaths per unit of time can be three to one, four to one, five to one, or more than five to one. In some cases, a ratio of one to one may also be advantageous.

[0050] According to one embodiment, the exhalation phase of every second breath can last at most 3 seconds, preferably at most 1 second. Experience has shown that at such a duration, a sufficiently effective increase in the (average) carbon dioxide elimination can be achieved without significantly increasing the tidal volume or the risk of lung collapse.

[0051] According to one embodiment, the second setpoint can be between 20 and 70 percent of the first setpoint. A ratio within this percentage range has proven particularly advantageous in practice.

[0052] According to one embodiment, the lower limit can be switched between the first setpoint, the second setpoint, and a third setpoint lying between the first and second setpoints, depending on the breathing sequence. In this case, the breathing sequence can further include one or more third breaths in at least one (or each) repetition, during which the tracheal pressure is intended to fall to the third setpoint during the (respective) exhalation phase. Each first breath that immediately precedes a second breath or a sequence of immediately consecutive second breaths, or each sequence of first breaths that immediately precedes a second breath or a sequence of immediately consecutive second breaths, can be immediately preceded by a third breath or a sequence of immediately consecutive third breaths.

[0053] The third setpoint can be, for example, a reference value, particularly in the form of a normal value for positive end-expiratory tracheal pressure, which should be used for a predominant proportion or at least half of the breaths per repetition or per unit of time. By first raising the lower limit from this reference value to the first setpoint before lowering it to the second setpoint in the subsequent exhalation phase, alveolar ventilation can be further improved.

[0054] According to one embodiment, the third setpoint can be between 50 and 80 percent of the first setpoint. A ratio within this percentage range has proven particularly advantageous in practice.

[0055] The ventilation system may further include: a ventilation catheter that can be inserted into the trachea to enable pressure equalization between the trachea, more precisely an (inner) cavity of the trachea, and an (external) environment of the patient; a suction device to generate a suction flow through the ventilation catheter inserted into the trachea, so that breathing air is actively drawn from the trachea into the environment of the patient.

[0056] In this case, according to one embodiment, the control method can further include, if the patient is also connected to the suction device via the ventilation catheter: activating the suction device in parallel with controlling the tracheal pressure to flush out unwanted carbon dioxide from the dead space. "Activating" can be understood, for example, as switching the suction device on or off alternately, or more generally, controlling the suction power of the suction device. In this way, for example, additional elimination of carbon dioxide from the dead space can be achieved during an exhalation phase of the current breath, so that during an inhalation phase of a future breath immediately following the current one, unwanted rebreathing of carbon dioxide from the dead space is avoided or at least reduced compared to an embodiment without such active ventilation.

[0057] Furthermore, this embodiment allows for targeted adjustment of the suction flow, for example, to a change in the ventilation situation and / or the patient's health status. For instance, such active suction can significantly increase or decrease the suction flow compared to an embodiment where the suction flow occurs solely as a result of a given difference between the pressure in the trachea and the pressure in the patient's environment.

[0058] Experiments showed that particularly efficient carbon dioxide removal can be achieved when the extraction flow rate is 5-20 l / min, 10-20 l / min or 5-7 l / min.

[0059] According to one embodiment, the suction device can be activated during one or more exhalation phases, for example, during the exhalation phase of each first breath and / or each second breath in the aforementioned breathing sequence. Additionally or alternatively, the suction device can be activated during one or more inhalation phases, for example, during the inhalation phase of each first breath and / or each second breath in the aforementioned breathing sequence. Such a combination of active suction of (exhaled) air with targeted FRC variation can further improve carbon dioxide elimination.

[0060] According to one embodiment, the control method can further include receiving measurement data relating to at least one parameter relevant to patient ventilation. This parameter can include at least one of the following: a (current) partial pressure of at least one respiratory gas—preferably a (current) partial pressure of carbon dioxide—in the suction stream and / or in an exhaled air stream from the patient and / or in the patient's blood; a (current) pH value of the patient's blood. Accordingly, activation of the suction device can be performed taking the measurement data into account, and / or the control method can further include: determining the amount of carbon dioxide eliminated from the dead space and / or via the ventilation catheter per ventilation duration using the measurement data, and outputting a value indicating the amount of carbon dioxide eliminated.The term "ventilation duration" can generally be understood as a unit of time as a reference value, such as 1 min, 1 s, the duration of a single breath or the duration of a phase of a single breath, for example an inhalation or exhalation phase.

[0061] Additionally or alternatively, at least one measurement parameter can include at least one of the following: a (current) suction pressure as a (current) breathing air pressure in the ventilation catheter; a (current) volume flow through the ventilation catheter; a (total) volume of breathing air exhaled by the patient during a ventilation period (for example, a current minute ventilation of the patient); a (current) volume of dead space.

[0062] The (current) volume of dead space can be determined, for example, from a capnogram and / or oxigram of the patient, preferably automatically and / or before the first start of the control procedure and / or before each (or each nth) new journal.

[0063] It is possible that the measurement data may additionally or alternatively include image data showing the two- and / or three-dimensional extent of air-filled regions of the patient's lungs. The image data may preferably have been generated using electrical impedance tomography (EIT). However, other invasive or non-invasive imaging techniques are also conceivable.

[0064] The measurement data can also be used to generate the control signal for controlling the ventilator.

[0065] According to one embodiment, activating the extraction device can include: generating a further control signal to control the extraction device so that the extraction flow follows a predetermined extraction flow profile.

[0066] In other words, activation can include controlling the suction power of the suction device in parallel with controlling the tracheal pressure. This allows, for example, automatic adjustment of the suction power to changes in the ventilation situation and / or the patient's health status by appropriately adjusting the suction flow profile. The suction flow profile can, for example, be based on a single breath or on at least one phase of a single breath, preferably an inhalation and / or exhalation phase. The suction flow profile can, for example, specify one or more setpoint values ​​between 5–20 l / min, 10–20 l / min, or 5–7 l / min for the suction flow.

[0067] According to one embodiment, activating the extraction device based on the measurement data can include controlling the extraction flow in several successive stages. Each stage can include: receiving the measurement data and reference data for the at least one measurand; determining a measurement deviation by comparing the measurement data with the reference data (for example, by calculating the difference between the measurement data and the reference data for the respective time step); and generating a further control signal to control the extraction device in order to adjust the extraction flow so that the measurement deviation is reduced. "Reference data" can, for example, be understood to mean a setpoint or a series of setpoints for the at least one measurand. In other words, the extraction flow can be controlled so that the actual value of the at least one measurand approaches a constant or varying setpoint.The reference data can, for example, define an approximate carbon dioxide partial pressure to be reached at the end of an exhalation phase, preferably zero, and / or a minimum lower limit for the pH of the patient's blood. In principle, the pH of the patient's blood should be between 7.35 and 7.45. However, in ventilation according to the permissive hypercapnia concept, where a slight respiratory acidosis is accepted in the interest of the gentlest possible ventilation, a significantly lower lower limit, preferably 7.2, is also possible.

[0068] According to one embodiment, the ventilation system may further include: a ventilation catheter that can be inserted into the trachea to allow pressure equalization between the trachea and the patient's environment while controlling tracheal pressure, thus flushing out unwanted carbon dioxide from a dead space in the patient's respiratory apparatus and / or the ventilation system. In other words, the ventilation catheter may be designed to allow a controlled, for example, continuous, outflow of exhaled air from the trachea into the patient's environment when the patient is ventilated with a positive airway pressure (relative to the ambient pressure), for example, during CPAP ventilation or a form of ventilation based on it.

[0069] The term "catheter," as in "ventilation catheter" or "pressure monitoring catheter" (see below), can refer, for example, to a tube or hose with a proximal open end (from the patient's perspective) and a distal open end (from the patient's perspective). Such a catheter may be significantly thinner than the endotracheal tube and / or be insertable into the endotracheal tube. Depending on the design, either the ventilation catheter or the pressure monitoring catheter, or both, may be integrated into the endotracheal tube, for example, permanently attached to it (and thus insertable into the trachea along with it).

[0070] The ventilation catheter causes a leak, which, due to the tracheal pressure control, prompts the ventilator to provide an (additional) lavage flow to maintain the set tracheal pressure. If such a leak persists throughout the entire respiratory cycle, the resulting lavage flow is continuous. This has the effect of flushing unwanted carbon dioxide from the dead space—specifically, the instrumental dead space and the anatomical dead space—into the patient's surrounding environment before the next inhalation phase begins. Depending on the proportion of dead space to the minute volume (generally at least one-third of the minute volume), this can significantly increase the efficiency of ventilation compared to other ventilation methods.Essential to this is the monitoring and control of the tracheal pressure during the inhalation and / or exhalation phase of each breath, so that the pressure loss caused by the ventilation catheter, which can optionally be adjusted by active suction, can be quickly and accurately compensated.

[0071] According to one embodiment, the control procedure for ventilating the patient using the ventilation catheter may further include: receiving measurement data regarding at least one parameter relevant to the patient's ventilation (see above); determining the amount of carbon dioxide eliminated from the dead space and / or via the ventilation catheter per ventilation duration using the measurement data; and outputting a value indicating the amount of carbon dioxide eliminated (for example, via a display). According to one embodiment, the ventilation system may further include: a suction device for generating a suction flow through the ventilation catheter inserted into the trachea, so that exhaled air is actively drawn from the trachea into the patient's environment.In this case, the control unit can be configured to further perform the following step when executing the control procedure, if the patient is also connected to the suction device via the ventilation catheter: activating the suction device in parallel with controlling the tracheal pressure to flush out unwanted carbon dioxide from a dead space of the patient's respiratory apparatus and / or the ventilation system.

[0072] To actively generate the extraction flow, the extraction device can include one or more electropneumatic actuators. Such an actuator can be, for example, a blower or an electrically controlled valve and / or be controllable by the control unit.

[0073] In this way, for example, an additional elimination of carbon dioxide from the dead space can be effected during an exhalation phase of a current breath, so that in an inhalation phase of a future breath immediately following the current breath, an undesirable rebreathing of carbon dioxide from the dead space is avoided or at least reduced compared to an embodiment without such active ventilation.

[0074] Furthermore, this embodiment allows for targeted adjustment of the suction flow, for example, to a change in the ventilation situation and / or the patient's health status. For instance, such active suction can significantly increase or decrease the suction flow compared to an embodiment where the suction flow occurs solely as a result of a given difference between the pressure in the trachea and the pressure in the patient's environment.

[0075] According to one embodiment, the ventilation system may further include a pressure-measuring catheter that can be inserted into the trachea. In this case, the tracheal pressure sensor may be configured to detect the tracheal pressure as the breathing air pressure within the pressure-measuring catheter inserted into the trachea. For example, the tracheal pressure sensor may be connected to a distal open end (from the patient's perspective) of the pressure-measuring catheter. A proximal open end (from the patient's perspective) of the pressure-measuring catheter may be insertable into the trachea. In other words, when the pressure-measuring catheter is inserted into the trachea, the distal open end may be located outside the trachea and the proximal open end inside the trachea. The location of the proximal open end of the pressure-measuring catheter, once fully inserted into the trachea, may, for example, correspond to the detection point described above.This allows for a sufficiently accurate measurement of tracheal pressure using simple means.

[0076] According to one embodiment, the tracheal pressure sensor can be placed (completely) inside the trachea. This can further improve the accuracy of tracheal pressure measurement.

[0077] According to one embodiment, the tracheal pressure sensor can be designed as a MEMS sensor (MEMS = microelectromechanical system), i.e., in a miniaturized form, for example, as a capacitive or resistive MEMS pressure sensor. For instance, the tracheal pressure sensor can be designed as a MEMS sensor that can be placed entirely within the trachea. In this case, the tracheal pressure sensor can be attached to one end of a suitable tracheal catheter, such as a ventilation catheter, endotracheal tube, or other (endo)tracheal catheter, and inserted into the trachea along with this end. This allows for particularly accurate measurement of the tracheal pressure without the need for a separate pressure-measuring catheter.Such direct measurement can also be less susceptible to interference than measurement via the air column in a separate tube (or tube) in the form of the pressure-measuring catheter, which can be partially or completely obstructed, for example, by respiratory secretions or a kink, thus impairing the pressure measurement. Inserting only one catheter or tube can also reduce airway resistance compared to a design with multiple catheters. Furthermore, this allows the use of a standard endotracheal tube without additional design modifications and / or a standard connector with a suitable opening for inserting the respective catheter. Such a combination catheter, for example, allows for subsequent insertion in patients who develop a carbon dioxide-related problem during ventilation.The transmission of sensor data generated by the MEMS sensor, including, for example, the actual values ​​of the tracheal pressure, to the control unit can be carried out, for example, via a wired and / or wireless data communication connection.

[0078] Brief description of the drawings

[0079] The following describes embodiments of the invention with reference to the accompanying drawings. Neither the description nor the drawings are to be understood as limiting the scope of the invention.

[0080] Fig. 1 shows a ventilation system according to one embodiment of the invention.

[0081] Fig. 2 shows a tracheal pressure curve corresponding to a cyclically repeating sequence of first and second breaths for use in a control method that can be implemented by a control unit according to an embodiment of the invention.

[0082] Fig. 3 shows a tracheal pressure profile corresponding to a cyclically repeating sequence of first, second and third breaths for use in a control method that can be implemented by a control unit according to an embodiment of the invention.

[0083] The figures are purely schematic and not to scale. If the same reference symbols are used in different drawings, these reference symbols denote identical or equivalent features.

[0084] Embodiments of the invention

[0085] Fig. 1 shows a ventilation system 1 for the invasive ventilation of a patient. The ventilation system 1 comprises a tracheal pressure sensor 3 for detecting a tracheal pressure p_tr as a breathing air pressure in the patient's trachea 5 (hereinafter referred to as trachea 5), ​​a breathing tube 7 that can be inserted into the trachea 5, and a ventilator 9 for generating a breathing airflow 11 through the breathing tube 7 inserted into the trachea 5, thus ventilating the patient. Furthermore, the ventilation system 1 includes a control unit 13 configured to execute a specific control procedure when the patient is connected to the ventilator 9 via the breathing tube 7, as shown in Fig. 1.

[0086] The control unit can comprise a processor 15 and a memory 17 in which a computer program for operating the ventilation system 1 can be stored. The processor 15 can be configured to execute the aforementioned (computer-implemented) control procedure by running the computer program.

[0087] The control procedure involves controlling the tracheal pressure p_tr in several successive journals. Each journal comprises the following procedure steps: receiving an actual value 19 of the tracheal pressure p_tr determined by the tracheal pressure sensor 3 and a setpoint 21 associated with the tracheal pressure p_tr; determining a tracheal pressure deviation by comparing the actual value 19 with the setpoint 21, for example by subtracting the actual value 19 from the setpoint 21; generating a control signal 23 to control the ventilator 9, for example a ventilation actuator 25 of the ventilator 9, in order to adjust the airflow 11 so that the tracheal pressure deviation is reduced.

[0088] The setpoint 21 can be received, for example, from memory 17, from another memory of the ventilation system 1, from an external memory and / or via a wired and / or wireless data communication network.

[0089] The ventilation actuator 25 can include one or more electropneumatic ventilation actuators. Such a ventilation actuator could be, for example, a blower or an electrically controlled valve.

[0090] The breathing tube 7 can be connected to a pressure port 27 of the ventilator 9. The ventilation actuator 25 can be configured to provide a suitable ventilation pressure at the pressure port 27, for example, such that during an exhalation phase an expiratory airflow 11a is directed through the breathing tube 7 as the airflow 11 and during an inhalation phase an inspiratory airflow 11b is directed through the breathing tube 7 as the airflow 11.

[0091] The breathing air streams 11a, 11b can be directed through a common tube or - as shown in Fig. 1 - through separate tubes and a Y-piece 29 between the breathing tube 7 and the pressure port 27.

[0092] Additionally, the ventilator 9 can include a ventilation pressure sensor 31 for detecting the ventilation pressure currently applied to the pressure port 27. In this case, controlling the tracheal pressure p_tr in each journal can further include: receiving a ventilation pressure value 33, which indicates the ventilation pressure detected by the ventilation pressure sensor 31; checking whether the actual value 19 is plausible using the ventilation pressure value 33; if the actual value 19 is plausible, using the actual value to determine the tracheal pressure deviation and / or, if the actual value 19 is implausible, discarding the actual value 19. Such plausibility checks can prevent major errors in controlling the tracheal pressure p_tr, for example, due to measurement inaccuracies resulting from mechanical interference with the pressure measurement, e.g. B. by misplacing and / or kinking a pressure measuring catheter used for pressure measurement.

[0093] The actual value can be considered plausible, for example, if it lies within a specific range around the ventilation pressure value of 33. Such a range could correspond, for instance, to a deviation of plus / minus 0.1, plus / minus 1, plus / minus 5, or plus / minus 10 percent of the ventilation pressure value of 33. If the actual value lies outside this range, it is considered implausible.

[0094] In this example, the ventilation pressure value 33 is an output value of the ventilation pressure sensor 31 (received directly from the control unit 13). Alternatively, the ventilation pressure value 33 can also be an output value of a separate data storage device.

[0095] In addition to the endotracheal tube 7, a ventilation catheter 35 may be inserted into the trachea 5. The ventilation catheter 35 allows pressure equalization between the trachea 5 and the patient's surroundings while controlling the tracheal pressure p_tr.

[0096] This results in (at least partial) flushing out of unwanted carbon dioxide from a dead space of the patient's respiratory apparatus and / or the ventilation system 1 when the patient is ventilated by means of the ventilator 9 with a positive airway pressure (relative to the respective ambient pressure), for example as part of CPAP ventilation or a form of ventilation based thereon.

[0097] To further improve or better control the lavage, the ventilation system 1 can also include a suction device 37 for actively generating a suction flow 39 through the ventilation catheter 35, so that breathing air is actively pumped from the trachea 5 into the patient's environment. In this case, the control method can also include activating the suction device 37, for example, a suction actuator 41 of the suction device 37, in parallel with controlling the tracheal pressure p_tr. Due to the (simultaneous) tracheal pressure control, this results in a targeted, for example, continuous lavage of the unwanted carbon dioxide from the dead space.

[0098] The extraction actuator 41 can comprise one or more electropneumatic extraction actuators. Such an extraction actuator could be, for example, a blower or an electrically controlled valve.

[0099] In this way, for example, an additional elimination of carbon dioxide from the dead space can be effected during an exhalation phase of a current breath, so that in an inhalation phase of a future breath immediately following the current breath, an undesirable rebreathing of carbon dioxide from the dead space is avoided or at least reduced compared to an embodiment without such active ventilation.

[0100] Furthermore, this allows for targeted adjustment of the suction flow 39, for example, to a change in the ventilation situation and / or the patient's health status. For example, such active suction can significantly increase or decrease the suction flow 39 compared to an embodiment where the suction flow 39 only results from a given difference between the pressure in the trachea 5 and the pressure in the patient's environment.

[0101] Furthermore, the control procedure can also include receiving measurement data regarding at least one parameter relevant to the patient's ventilation. Such a parameter could be, for example, one of the following:

[0102] - a (current) carbon dioxide partial pressure in the extraction stream 39;

[0103] - a (current) partial pressure of carbon dioxide in a respiratory airflow exhaled by the patient, for example in the expiratory respiratory airflow 11a (and / or in a sidestream branched off from it);

[0104] - a (current) partial pressure of carbon dioxide in the patient's blood;

[0105] - a (current) pH value of the patient's blood;

[0106] - a (current) suction pressure as a (current) breathing air pressure in the ventilation catheter 35;

[0107] - a (current) volume flow through the ventilation catheter 35;

[0108] - a total (current) volume of air exhaled by the patient during a specific ventilation duration, for example in the form of the patient's (current) minute volume; a (current) volume of dead space.

[0109] In this case, the activation of the extraction device 37 can take place taking the measurement data into account.

[0110] The measurement data may have been generated, at least in part, by means of suitable sensors in the ventilation system 1.

[0111] In addition to or as an alternative to the aforementioned measurement parameter(s), the measurement data may include image data showing the two- and / or three-dimensional extent of air-filled regions of the patient's lungs. The image data may preferably have been generated using electrical impedance tomography (EIT). However, other invasive or non-invasive imaging techniques are also conceivable.

[0112] Activating the extraction device 37 based on the measurement data can, for example, involve controlling the extraction flow 39 in several successive cycles. Each cycle can include the following process steps: receiving the measurement data and reference data for the respective measured quantity; determining a measurement data deviation by comparing the measurement data with the respective reference data, for example, by subtracting the measurement data from the respective reference data; generating a further control signal 43 to control the extraction device 37, for example, the extraction actuator 41, in order to adjust the extraction flow 39 so that the measurement data deviation is reduced.

[0113] The measurement data can also be used, for example, to generate the control signal 23 in a suitable manner.

[0114] The tracheal pressure sensor 3 can be located outside the trachea 5 in a housing of the ventilator 9, as shown here. The tracheal pressure sensor 3 can be connected to a separate pressure measuring catheter 45, which extends into the trachea 5, thus enabling precise measurement of the tracheal pressure p_tr. The proximal open end of the pressure measuring catheter 45 (from the patient's perspective) can be positioned along the longitudinal axis of the trachea 5 at the same location as the proximal open end of the ventilation catheter 35 and / or the endotracheal tube 7 (from the patient's perspective). Depending on the situation, the proximal open end of the pressure measuring catheter 45 can also be positioned significantly higher or lower than the proximal open end of the ventilation catheter 35 and / or the endotracheal tube 7.

[0115] In the example shown in Fig. 1, the ventilation catheter 35 and the pressure measuring catheter 45 each run partially inside the breathing tube 7. However, it is also possible for the respective catheter 35 or 45 to be arranged completely outside the breathing tube 7.

[0116] Alternatively, the tracheal pressure sensor 3 can be designed as a particularly compact MEMS sensor that can be placed entirely within the trachea 5. Such a sensor can further improve the accuracy and robustness of the tracheal pressure measurement due to the short measuring distance. In this case, a pressure measuring catheter 45 is not required, which can simplify connecting the patient to the ventilation system 1.

[0117] The extraction capacity of the extraction device 37 can be controlled manually by the user and / or automatically by the control unit 13.

[0118] The ventilation system 1 can optionally include one or more sensors for detecting a carbon dioxide partial pressure and / or a volume flow rate (also called flow) and / or an inspiratory air pressure in the ventilation catheter 35. The carbon dioxide partial pressure thus detected should, however, be appropriately adjusted to the compensating (carbon dioxide-free) fresh gas flow provided by the ventilator 9 during suctioning. This allows for a good degree of accuracy in determining how much carbon dioxide is eliminated per unit of time via this pathway.

[0119] It is also possible that the carbon dioxide partial pressure is measured directly at Y-piece 29. If the carbon dioxide partial pressure measured there approaches zero, this can be considered a reliable indication that no rebreathing of carbon dioxide from the (instrumental) dead space is occurring. Generally, the carbon dioxide partial pressure in the circulation should approach zero when suction is activated.

[0120] Depending on the strength of the suction flow 39, the expiratory airflow 11a may also come to a complete standstill during active suction.

[0121] As shown in Fig. 2 and Fig. 3, it is possible that the setpoint values ​​21 received in the several successive journals are values ​​of a predefined tracheal pressure profile 47 (hereinafter referred to as tracheal pressure profile 47). Accordingly, the control signal 23 can be generated in each journal such that the tracheal pressure p_tr follows the tracheal pressure profile 47 with each breath of the patient.

[0122] The tracheal pressure curve 47 can rise from a lower limit 49 to an upper limit 51 during an inhalation phase, in which the patient is supposed to inhale, and fall from the upper limit 51 back to the lower limit 49 during an exhalation phase, in which the patient is supposed to exhale.

[0123] The lower limit 49 can be switched between a first setpoint v1 and a second setpoint v2, which is smaller in absolute value than the first setpoint v1, during patient ventilation according to a cyclically repeating (predefined) breathing sequence. The breathing sequence can, in each repetition, include one or more first breaths I, during which the tracheal pressure p_tr is intended to fall to the first setpoint v1 during exhalation, and one or more second breaths II, during which the tracheal pressure p_tr is intended to fall to the second setpoint v2 during exhalation. Each second breath II or each sequence of immediately consecutive second breaths II can be immediately preceded by a first breath I or a sequence of immediately consecutive first breaths I.

[0124] In this way, a targeted periodic fluctuation of the functional residual capacity (FRC) can be achieved over one or more breaths. This, in turn, can have a beneficial effect on carbon dioxide elimination, particularly in combination with the active and / or passive suction via the ventilation catheter 35 described above. Furthermore, such control of the tracheal pressure (p_tr) allows for a significant increase in average carbon dioxide elimination without necessarily increasing the volume exhaled by the patient.

[0125] Preferably, the activation of the suction device 37 and the switching of the lower limit 49 between the different setpoints v1, v2 can be appropriately coordinated in time, in particular such that the activation of the suction device 37 takes place in the exhalation phase of each first breath I and / or each second breath II.

[0126] In the example shown in Fig. 2, every second breath II is immediately preceded by a sequence of four (or three) consecutive first breaths I. Accordingly, the ratio of the number of first breaths I to the number of second breaths II in each repetition, for example per minute, is four (or three) to one. However, other ratios are also possible, such as one to one, two to one, or five to one. Preferably, the second setpoint v2 is between 20 and 70 percent of the first setpoint v1.

[0127] As shown in Fig. 3, the breathing sequence in each repetition can further include one or more third breaths III, during which the tracheal pressure p_tr is intended to fall to a third setpoint v3 in the respective exhalation phase. The third setpoint v3 (here 8 cmHjO) can lie in magnitude between the first setpoint v1 (here 12 cmHjO) and the second setpoint v2 (here 5 cmHjO). Preferably, the third setpoint v3 is between 50 and 80 percent of the first setpoint v1.

[0128] Thus, it is possible for the lower limit 49 to switch between the first setpoint v1, the second setpoint v2, and the third setpoint v3 according to the respiratory sequence. In this example, each first breath I, which immediately precedes a second breath II, is immediately preceded by a sequence of two consecutive third breaths III. Accordingly, the ratio between the number of third breaths III, the number of first breaths I, and the number of second breaths II in each repetition, for example, per minute, is two to one to one. However, other suitable ratios are also possible, such as one to one to one. It is also conceivable that the ratio is continuously varied during ventilation depending on the patient's condition.

[0129] The third setpoint v3 could, for example, be a normal PEEP value used for a majority or at least half of the breaths per repetition or per unit of time. By first raising the lower limit 49 from the normal PEEP value to the first setpoint v1 before lowering it to the second setpoint v2 in the subsequent exhalation phase, alveolar ventilation can be further improved.

[0130] It is possible that the exhalation phase of each first breath (I) is associated with a decreasing first segment of the tracheal pressure curve 47, the exhalation phase of each second breath (II) with a decreasing second segment of the tracheal pressure curve 47, and the exhalation phase of each third breath (III) with a decreasing third segment of the tracheal pressure curve 47. The respective segments of the different breath types (I, II, III) can be coordinated in their duration and / or amplitude in each repetition of the breath sequence so that the volume exhaled by the patient with each breath remains more or less constant over several breaths, and in particular does not increase significantly during each transition from a first breath (I) to a second breath (II). Thus, despite a significantly increased average carbon dioxide elimination, the gentlest possible ventilation can be ensured.

[0131] To allow for adjustment of the respective duration and / or amplitude – particularly of the second segments – to the patient's individual condition, an optional step in the control procedure can receive a compliance value indicating the compliance of at least a part of the patient's respiratory system (e.g., lung compliance). Additionally or alternatively, a resistance value indicating flow resistance in at least a part of the patient's respiratory system (e.g., airway resistance) can be received.

[0132] For example, the elongation value and the resistance value can be multiplied together. The resulting product, for example in the form of a

[0133] The time constant can then be used to determine the respective duration and / or amplitude of the first and / or second segments. The duration can be chosen to be longer the larger the absolute value of the product. Similarly, the amplitude can be chosen to be larger the larger the absolute value of the product. This allows for a simple scaling of the duration or amplitude depending on the respective state of the respiratory system.

[0134] Additionally or alternatively, the extensibility value and / or the resistance value and / or the product of the extensibility value and the resistance value can be used to determine a number of second breaths II in each repetition of the breathing sequence and / or to determine a ratio of a number of second breaths II to a number of first breaths I and / or to a number of third breaths III in each repetition of the breathing sequence.

[0135] In practice, a duration of no more than 1 to 3 seconds for the exhalation phase of every second breath (II) has proven effective. However, other values ​​are possible depending on the patient's condition. The upper limit 51 can be determined, for example, by obtaining a suitable differential value (here, a suitable tracheal pressure differential value) for each individual breath (I, II, or III) and then adding this differential value to the current value v1, v2, or v3 of the lower limit 49 to obtain the current value of the upper limit 51 for the respective breath (I, II, or III).

[0136] The difference value can be the same for each breath. Alternatively, different difference values, i.e., differing in their magnitude, can be received for different breaths.

[0137] For example, it is possible that for each breath I or III immediately following a second breath II, an alternative differential value (here, an alternative tracheal pressure differential value) is received, which differs in magnitude from the (normal) differential value in a suitable way, for example, being larger in magnitude than the (normal) differential value. The current value of the upper limit 51 for the respective breath I or III can then be determined by adding the alternative differential value instead of the (normal) differential value to the respective current value of the lower limit 49, here v2. For example, the alternative differential value could be equal to the sum obtained by adding the (normal) differential value to the difference between the first setpoint v1 and the second setpoint v2.

[0138] It is well known that the functional residual capacity (FRC) in healthy individuals is not constant, but fluctuates at low cyclic frequencies of approximately 1 in 500 breaths, which correspondingly affects gas exchange. The ventilation mode described above takes this physiological behavior into account, but accelerates these fluctuations to achieve additional carbon dioxide elimination during mechanical ventilation. This is accomplished by recurring, short, and controlled reductions in the functional residual capacity every few breaths. The ventilation mode can therefore also be referred to as variable FRC ventilation. Such a ventilation mode can be used as an independent ventilation mode in a ventilator or in conjunction with other devices, such as the suction device 37, to actively reduce anatomical and instrumental dead spaces.

[0139] The ventilation mode can consist of an automatic, cyclical reduction of FRC relative to a baseline value, for example, by lowering the PEEP value for the duration of a single breath. This PEEP reduction is therefore particularly short, for example, less than one second. Such a PEEP reduction can occur, for instance, every two to four breaths. This cyclical PEEP-induced FRC reduction results in additional elimination of carbon dioxide from the smaller airways and the alveolar compartment. Since the carbon dioxide in these specific breaths originates predominantly from the alveoli, alveolar ventilation is enhanced without dead space in the airways.

[0140] The reduction in FRC should be very brief to avoid lung collapse. Generally, the duration of the FRC reduction should be significantly shorter than the time constant for airway and / or alveolar collapse. After a series of normal breaths at a baseline PEEP, the PEEP level should be reduced for a single breath to allow the FRC to decrease. This temporary reduction in FRC can be compensated for during the subsequent inhalation phase. Therefore, the ventilator should be able to provide a sufficiently high inhalation flow rate to not only restore the FRC but also deliver the desired tidal volume.

[0141] For example, the ventilation mode can be configured so that the PEEP value decreases or increases by approximately 5 cmHjO from one breath to the next, while providing a sufficiently high airflow during inhalation to quickly compensate for any changes in FRC and maintain normal tidal ventilation. The pressure difference between the upper and lower set pressures should be below 15 mmHg to ensure the most lung-protective ventilation possible.

[0142] The FRC changes can be manually adjusted in terms of their number per unit of time, for example per minute, and / or their amplitude. Alternatively, the adjustment can be made automatically by the ventilator.

[0143] It is possible for the ventilation mode to automatically generate a sequence of FRC changes at a constant tidal volume, depending on the specific difference value. The total exhaled minute volume comprises a first part, corresponding to the product of tidal volume and respiratory rate, and a second part, corresponding to the additional volume exhaled due to the additional PEEP reduction. For example, a standard minute volume of 6.75 L / min (product of a tidal volume of 450 mL and a respiratory rate of 15 / min) can be set, along with repeated short PEEP reductions, first from 10 cmHjO to 5 cmHjO and then back to 10 cmHjO. Assuming that such a PEEP reduction causes an additional exhalation of 200 mL on every fourth breath, an additional ventilation of approximately 1 L / min (200 mL times 5 breaths per minute) can be achieved, resulting in a total minute volume of 7.75 L / min.In other words, the lower the ratio between normal breaths and special breaths (with reduced PEEP) and the greater the PEEP reduction, the greater the effect of the additional carbon dioxide elimination.

[0144] Using a breathing sequence, as illustrated in Fig. 3, the amplitude of the FRC change can be further increased, thus improving alveolar ventilation. The lower limit 49 can, for example, fluctuate regularly by plus / minus 3 to 4 cmHjO around a baseline PEEP value. The baseline PEEP value should be set so that the lungs do not collapse during exhalation. With a baseline PEEP value of 8 cmHjO and a 1:1:1 ratio, the lower limit 27 could, for example, fluctuate cyclically as follows: 8-12-4-8-12-4-8-12-4, etc. (8-8-12-4-8-8-12-4-8-8-12-4, etc., at a 2:1:1 ratio). Such a reduction in PEEP, here by 8 cmHjO each time, can significantly increase carbon dioxide elimination. This makes it possible to reduce the tidal volume to a minimum value when the FRC fluctuates.

[0145] Finally, it should be noted that terms such as "have", "comprise", "include", "with", etc. do not exclude any other elements or steps, and indefinite articles such as "a" or "an" do not exclude any variety.

[0146] It is further noted that features or steps described with reference to one of the foregoing embodiments may also be used in combination with features or steps described with reference to other of the foregoing embodiments.

[0147] Reference numerals in the claims are not to be understood as limiting the scope of the subject matter defined by the claims. List of reference numerals

[0148] I Ventilation system 20 33 Ventilation pressure value

[0149] 3 Tracheal pressure sensor 35 Ventilation catheter

[0150] 5 Trachea 37 Suction device 7 Breathing tube 39 Suction flow

[0151] 9 ventilator 41 suction actuator

[0152] II Breathing airflow 25 43 further control signal

[0153] 11a Expiratory airflow 45 Pressure measuring catheter

[0154] 11b Inspiratory airflow 47 Tracheal pressure curve 13 Control unit 49 Lower limit

[0155] 15 processors 51 upper limit

[0156] 17 storage 30 p_tr tracheal pressure

[0157] 19 Actual value t Time

[0158] 21 Setpoint vl first setpoint 23 Control signal v2 second setpoint

[0159] 25 Ventilation actuator v3 third setpoint

[0160] 27 Pressure connection 35 l first breath

[0161] 29 Y-piece II second breath

[0162] 31 Ventilation pressure sensor III third breath

Claims

Claims 1. Control unit (13) for a ventilation system (1) for invasive ventilation of a patient, wherein the ventilation system (1) comprises: a tracheal pressure sensor (3) for detecting a tracheal pressure (p_tr) as a breathing air pressure in the trachea (5) of the patient; a breathing tube (7) insertable into the trachea (5) of the patient; a ventilator (9) for generating a breathing airflow (11, 11a, 11b) through the breathing tube (7) inserted into the trachea (5) of the patient, so that the patient is ventilated; wherein the control unit (13) is configured to execute a control procedure when the patient is connected to the ventilator (9) via the breathing tube (7), the control procedure comprising: Control of tracheal pressure (p_tr) in several consecutive journals, each journal comprising: Receiving an actual value (19) of the tracheal pressure (p_tr) determined by means of the tracheal pressure sensor (3) and a setpoint value (21; v1, v2, v3) assigned to the tracheal pressure (p_tr); Determining a tracheal pressure deviation by comparing the actual value (19) with the target value (21; v1, v2, v3); Generating a control signal (23) to control the ventilator (9) to adjust the breathing airflow (11, 11a, 11b) so that the tracheal pressure deviation is reduced.

2. Control unit (13) according to claim 1, wherein controlling the tracheal pressure (p_tr) in each journal further comprises: receiving a ventilation pressure value (33) which corresponds to a The pressure port (27) of the ventilator (9) indicates the applied ventilation pressure, with the ventilation tube (7) being connected to the ventilator (9) via the pressure port (27) when ventilating the patient; Check if the actual value (19) is plausible, using the ventilation pressure value (33); if the actual value (19) is plausible: use the actual value (19) to determine the tracheal pressure deviation; and / or If the actual value (19) is not plausible: Discard the actual value (19).

3. Control unit (13) according to one of the preceding claims, wherein the setpoints (21; v1, v2, v3) received in the multiple successive magazines are values ​​of a predetermined tracheal pressure profile (47), wherein the control signal (23) is generated in each magazine such that the tracheal pressure (p_tr) follows the predetermined tracheal pressure profile (47) with each breath, wherein the predetermined tracheal pressure profile (47) rises from a lower limit (49) to an upper limit (51) during an inhalation phase, in which the patient is to inhale, and falls from the upper limit (51) to the lower limit (49) during an exhalation phase, in which the patient is to exhale, wherein the lower limit (49) switches between a first setpoint (v1) and a second setpoint (v2), which is smaller in absolute value than the first setpoint (v1), according to a cyclically repeating breath sequence. becomes,wherein the breathing sequence in each repetition comprises one or more first breaths (I) in which the tracheal pressure (p_tr) is to fall to the first set point (v1) during the exhalation phase, and one or more second breaths (II) in which the tracheal pressure (p_tr) is to fall to the second set point (v2) during the exhalation phase, wherein each second breath (II) or each sequence of immediately successive second breaths (II) is immediately preceded by a first breath (I) or a sequence of immediately successive first breaths (I).

4. Control unit (13) according to claim 3, wherein the exhalation phase of each first breath (I) is assigned a descending first section of the predetermined tracheal pressure profile (47) and the exhalation phase of each second breath (II) is assigned a descending second section of the predetermined tracheal pressure profile (47), wherein the first sections and the second sections are coordinated in their respective duration and / or amplitude in each repetition of the breathing sequence such that a volume exhaled by the patient in each second breath (II) is at most as large as a volume exhaled by the patient in each first breath (I).

5. Control unit (13) according to one of the preceding claims, wherein the ventilation system (1) further comprises: a ventilation catheter (35) that can be inserted into the patient's trachea (5) to enable pressure equalization between the patient's trachea (5) and the patient's environment; a suction device (37) for generating a suction flow (39) through the ventilation catheter (35) inserted into the patient's trachea (5), so that breathing air is actively drawn from the patient's trachea (5) into the patient's environment; wherein the control method further comprises, when the patient is connected to the suction device (37) via the ventilation catheter (35): Activating the suction device (37) in parallel with controlling the tracheal pressure (p_tr) to flush out unwanted carbon dioxide from a dead space of the patient's respiratory apparatus and / or the ventilation system (1).

6. Control unit (13) according to claim 5 referring backward to claim 3, wherein the suction device (37) is activated in the exhalation phase of each first breath (I) and / or each second breath (II).

7. Control unit (13) according to claim 5 or 6, wherein the control method further comprises: Receiving measurement data relating to at least one measurement relevant to the ventilation of the patient, wherein the at least one measurement includes at least one of the following: a carbon dioxide partial pressure in the suction stream (39) and / or in an exhaled air from the patient Airflow (11, 11a) and / or in the patient's blood; a pH value of the patient's blood; the activation of the suction device (37) is carried out taking into account the measurement data.

8. Control unit (13) according to claim 7, wherein the activation of the extraction device (37) is carried out taking into account the Measurement data includes: Controlling the extraction flow (39) in several successive journals, each journal comprising: Receiving measurement data and reference data for at least one measurement quantity; Determining a measurement data deviation by comparing the measurement data with the reference data; Generating an additional control signal (43) to control the extraction device (37) in order to adjust the extraction flow (39) so that the measurement data deviation is reduced.

9. Ventilation system (1) for invasive ventilation of a patient, wherein the ventilation system (1) comprises: a tracheal pressure sensor (3) for detecting a tracheal pressure (p_tr) as a breathing air pressure in the trachea (5) of the patient; a breathing tube (7) that can be inserted into the trachea (5) of the patient; a ventilator (9) for generating a breathing airflow (11, 11a, 11b) through the breathing tube (7) inserted into the trachea (5) of the patient, so that the patient is ventilated; a control unit (13) according to any one of claims 1 to 4.

10. Ventilation system (1) according to claim 9, further comprising: a ventilation catheter (35) that can be inserted into the trachea (5) of the patient to enable pressure equalization between the trachea (5) of the patient and an environment of the patient when controlling the tracheal pressure (p_tr), so that unwanted carbon dioxide is flushed out of a dead space of the respiratory apparatus of the patient and / or the ventilation system (1).

11. Ventilation system (1) according to claim 10, further comprising: a suction device (37) for generating a suction flow (39) through the ventilation catheter (35) inserted into the trachea (5) of the patient, so that breathing air is actively drawn from the trachea (5) of the patient into the patient's environment; wherein the control unit (13) is a control unit (13) according to any one of claims 5 to 8.

12. Ventilation system (1) according to one of claims 9 to 11, further comprising: a pressure measuring catheter (45) that can be inserted into the trachea (5) of the patient; wherein the tracheal pressure sensor (3) is configured to detect the tracheal pressure (p_tr) as a breathing air pressure in the pressure measuring catheter (45) inserted into the trachea (5) of the patient.

13. Ventilation system (1) according to one of claims 9 to 12, wherein the tracheal pressure sensor (3) is designed as a MEMS sensor that can be placed inside the trachea (5) of the patient.

14. Computer program for operating the ventilation system (1) according to any one of claims 9 to 13, wherein the computer program comprises commands which cause the control unit (13) to execute a control procedure when the patient is connected to the ventilator (9) via the breathing tube (7) when the computer program is executed by the control unit (13), wherein the control procedure comprises: Control of tracheal pressure (p_tr) in several consecutive journals, each journal comprising: Receiving an actual value (19) of the tracheal pressure (p_tr) determined by means of the tracheal pressure sensor (3) and a setpoint value (21; v1, v2, v3) assigned to the tracheal pressure (p_tr); Determining a tracheal pressure deviation by comparing the actual value (19) with the target value (21; v1, v2, v3); Generating a control signal (23) to control the ventilator (9) to adjust the breathing airflow (11, 11a, 11b) so that the tracheal pressure deviation is reduced.

15. Computer-readable medium on which the computer program according to claim 14 is stored.

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