METHOD AND DEVICE FOR MEASURING THE CONTENT OF AT LEAST ONE GAS IN EXAMINATE AIR

Description

[0001] The invention relates to a device for measuring the concentration of at least one gas in exhaled air, particularly for use with a ventilator.

[0002] Furthermore, the invention relates to a method for measuring the content of at least one gas in exhaled air.

[0003] Furthermore, the invention relates to a device for ventilation in the sense of a ventilator, in particular an emergency ventilator, comprising a device for measuring the content of at least one gas in exhaled air.

[0004] In the course of at least partially manual or mechanical ventilation of patients with air, the determination of various gas contents in both the air supplied to the patient and in the exhaled air is of interest.

[0005] For example, the carbon dioxide (CO2) or oxygen (O2) content is determined using suitable sensors.

[0006] Depending on the application, a high-resolution temporal measurement of the respective gas is required.

[0007] The respiratory cycle of humans and other respiratory organisms consists of inhalation (inspiration) and exhalation (expiration). When ambient air is inhaled, the inspiratory oxygen concentration (FiO2) is approximately 20.9 vol%. At the end of exhalation, after gas exchange between the lungs and the cardiovascular system, an end-tidal oxygen concentration (etO2) of approximately 16 vol% remains in the exhaled air. During inhalation, the CO2 content (FiCO2) of the inhaled air is approximately 0 vol% (0.04 vol% CO2 in the ambient air), while during exhalation it rises significantly, resulting in a measurable end-tidal CO2 concentration (etCO2) of approximately 4.5 vol%.

[0008] In medicine, for example, it is common practice to determine the CO2 concentration in a patient's exhaled air during breathing. At the end of exhalation, the end-tidal CO2 concentration (etCO2) can be determined, provided a sufficiently fast and therefore high-resolution CO2 sensor technology is used. This allows the concentration plateau at the end of exhalation to be determined.

[0009] There are two basic methods for measuring the CO2 content in exhaled air, according to current technology, which are used in connection with patient ventilation. Depending on the breathing phase, the respiratory gas flows through a tubing system of the ventilation device either towards or away from the patient. In the mainstream method, the patient's entire respiratory gas is analyzed directly in or on this tubing system, and thus within the main flow of respiratory gas. In contrast, in the sidestream method, a sample gas is drawn from the main flow and analyzed. The sample gas is usually drawn close to the patient so that both the inhaled and exhaled gas can be analyzed.

[0010] To measure the CO2 concentration in the inhaled air, a measuring cuvette is typically located in the ventilator, in which the sample gas is illuminated with near-infrared light. The CO2 in the sample gas absorbs some of the light, so the CO2 concentration in the inhaled air can be determined based on the remaining light intensity. This sensor technology is relatively fast, allowing the CO2 concentration in the inhaled air to be determined precisely throughout the entire breathing cycle (the rise time t(10%-90%) of such CO2 sensors is approximately 90 ms).

[0011] US 2013 / 165806 A1 discloses the detection of a respiratory phase and the respiratory phase-specific evaluation of the CO2 content of a gas sample of a patient's exhaled air.

[0012] US patent 2006 / 201507 A1 discloses a system for measuring oxygen consumption, whereby the breathing phase is detected and a gas sample is measured.

[0013] DE 10 2008 022761 A1 discloses a device for obtaining and examining breathing gas samples, wherein the breathing phase is determined using a CO2 sensor and a breathing phase-specific examination of the gas samples is carried out.

[0014] There are various sensor technologies for measuring the O2 content in exhaled air, such as paramagnetic sensors, galvanic cells, zirconium dioxide sensors, fluorescence sensors, and laser spectroscopy. These sensors also differ in size, response time, measurement accuracy, availability, lifespan, and price, with faster sensors generally being more expensive than slower ones.

[0015] Relatively small and inexpensive sensors for measuring O₂ concentration include galvanic oxygen sensors, in which the gas passes through a thin membrane to the cathode, where an initial reaction takes place. The resulting charge carriers then travel via the sensor's liquid electrolyte to the cathode, where a further reaction occurs. The anode coating is worn away with each reaction, which is why these sensors are also referred to as consumable sensors. The generated current is proportional to the O₂ concentration in the sample gas, but also depends on the pressure and temperature. Such galvanic O₂ sensors do not require an external power source, but their lifespan—depending on usage and the sensor's response time—is only one to two years. The rise time t(10%–90%) of such sensors is typically around 2 seconds, making them unsuitable for high-resolution temporal measurements of O₂ concentration.

[0016] For measuring the O2 content in exhaled air, the use of rapid O2 sensors is not common practice, particularly in emergency ventilation, due to space and / or cost constraints. Nevertheless, determining the end-tidal oxygen concentration (etO2) is of great interest to medical personnel in order to draw conclusions about the amount of oxygen taken up by a patient during ventilation, and conversely, the amount of oxygen not taken up and thus exhaled.

[0017] The etO2 value plays a particularly important role in preoxygenation, a process in which nitrogen is washed from a patient's lungs and replaced with oxygen. Using the etO2 value, the end time of the process can be determined based on measured data, thus avoiding the need to derive it from experience, which can be inaccurate for individual patients.

[0018] Determining the concentration of other gases in the air we breathe, such as VOCs (volatile organic compounds), hydrogen, or anesthetic gases, is also of interest in certain applications.

[0019] One object of the invention is therefore to create an improved device for measuring the concentration of at least one gas in exhaled air.

[0020] This problem is solved according to the invention by a device for measuring the content of at least one gas in exhaled air according to claim 1.

[0021] Another object of the invention is to create a device for measuring the concentration of at least one gas in exhaled air, which enables the determination of the concentration of this gas even with a sensor with a slow response time in a manner sufficient for the respective application.

[0022] This problem is solved according to the invention by a device for measuring the content of at least one gas in exhaled air according to claim 1.

[0023] Another objective of the invention is to create an improved device for ventilation.

[0024] This problem is solved according to the invention by a device for ventilation according to claim 6.

[0025] A further object of the invention is to create a method for measuring the content of at least one gas in exhaled air, which enables the determination of the content of this gas even with a sensor with a slow response time in a manner sufficient for the respective application.

[0026] This problem is solved according to the invention by a method for measuring the content of at least one gas in exhaled air according to claim 7.

[0027] The features of a device for measuring the concentration of at least one gas in exhaled air, disclosed below, are part of the invention both individually and in all feasible combinations.

[0028] An inventive device for measuring the content of at least one gas in exhaled air comprises at least one device for determining the breathing phase and additionally at least one gas sensor, as well as at least one control unit and at least one controllable valve and a pumping device.

[0029] The device for determining the respiratory phase is designed to determine the current respiratory phase and to detect a defined range within a patient's respiratory cycle. For this purpose, the device for determining the respiratory phase includes at least one suitable respiratory phase sensor.

[0030] In one embodiment of the invention, the device for determining the breathing phase has at least one breathing phase sensor designed as a CO2 sensor, an O2 sensor, a humidity sensor, a temperature sensor, a pressure sensor or a flow sensor.

[0031] The at least one respiratory phase sensor of the device for determining the respiratory phase is arranged for measurement according to the sidestream or mainstream method with reference to the main stream of the breathing air.

[0032] When using a pressure or flow sensor in the device for determining the breathing phase, the respective breathing phase sensor is, in a preferred embodiment of the invention, arranged for measurement in the mainstream flow method. The use of CO2, temperature, or humidity sensors for mainstream flow measurement is also possible.

[0033] The volume flow rate of the breathing air towards the patient is on the order of approximately 0 to 100 l / min. The aspiration rate of sample gas for a sidestream measurement is approximately 100 ml / min in embodiments of the invention.

[0034] When using a CO2, an O2, a humidity or a temperature sensor as a breathing phase sensor in the device for determining the breathing phase, the respective breathing phase sensor is arranged in a preferred embodiment of the invention for measurement in the sidestream method.

[0035] In an advantageous embodiment of the invention, the device for measuring the concentration of at least one gas in exhaled air comprises at least one water filter or other device for drying the sample gas, thus preventing condensation of the water vapor typically present in exhaled air in the vicinity of the measuring device and the associated impairment of the measurements. The use of at least one water filter or a device for drying the sample gas is particularly advantageous for sidestream measurements. Of course, measuring humidity after drying the sample gas is of little use for determining the exhalation phase.

[0036] As described above, the concentration of CO2 and O2 changes during the respiratory cycle. The humidity, temperature, pressure, and flow of the inhaled air also depend on the respiratory cycle. Exhaled air is generally more humid and warmer than the inhaled air, and it flows in the opposite direction.

[0037] Using a device for determining the respiratory phase according to the present invention, at least one of the aforementioned measured values ​​can be detected using a corresponding, high-resolution temporal respiratory phase sensor (fast sensor), and the measured value profile can be evaluated to determine in which respiratory phase of the respiratory cycle the breathing or ventilation of a patient is currently located.

[0038] In addition to the inspiration and expiration phases themselves, the recognition of the end-tidal area at the end of the expiration phase is of particular interest.

[0039] In a particularly advantageous embodiment of the invention, the device for determining the breathing phase is therefore designed to detect the end-tidal range.

[0040] Depending on the detected breathing phase, the control unit can be used to control at least one controllable valve and / or the pump device.

[0041] In an advantageous embodiment of the invention, the at least one controllable valve has at least one openable and closable valve path through which the gas to be measured can be directed to at least one gas sensor.

[0042] In addition, the pumping device can be controlled by the control unit in such a way that the gas to be measured can be directed to at least one gas sensor.

[0043] In a particularly preferred embodiment of the invention, the device for determining the respiratory phase is designed to determine the end-tidal range, and the controllable valve can be controlled by means of the control unit in such a way that the at least one valve path of the controllable valve is open for the duration of the end-tidal range of the expiratory phase and is closed at the beginning of the inspiratory phase, so that the gas sample of the exhaled air supplied to the area of ​​the at least one gas sensor originates from the end-tidal range of the expiratory phase.

[0044] In essence, the logic described above for opening or closing one or more valve paths of the controllable valve depending on any areas (breathing phases) in the breathing cycle is possible according to the invention.

[0045] In preferred embodiments of the invention, the device for determining the respiratory phase is designed to determine the end-tidal range, and the pumping device can be controlled by the control unit in such a way that the pumping device delivers sample gas to the area of ​​the gas sensor for the duration of the end-tidal range of the expiratory phase and switches off at the beginning of the inspiratory phase, so that the gas sample supplied to the area of ​​the at least one gas sensor originates from the end-tidal range of the expiratory phase.

[0046] The above-described setup of a device according to the invention for measuring the concentration of at least one gas in exhaled air thus enables the targeted introduction of a sample of exhaled air from a defined breathing phase and subsequently a longer period in which the exhaled air sample can be measured using the at least one gas sensor to determine the concentration of at least one gas in the exhaled air. This makes it possible to use gas sensors with a longer rise time and / or higher accuracy (slow sensor).

[0047] According to the invention, at least one gas sensor is designed as an O2 sensor, so that the end-tidal O2 content of the breathing air (etO2 value) can be determined.

[0048] The respiratory rate is typically 10 breaths / min in adults and 40 breaths / min in children, and can reach up to 110 breaths / min during cardiopulmonary resuscitation (CPR). Accordingly, the respiratory cycle period is approximately 540 ms (CPR) to 6 s (typical adult respiratory cycle).

[0049] The number of measurements required to reliably determine the respiratory phase depends on the length of the period of interest. Depending on the frequency or period of the desired ventilation mode (e.g., adult, child, cardiopulmonary resuscitation), the maximum permissible rise time for a gas sensor can therefore be determined.

[0050] In one embodiment of the invention, the maximum permissible rise time for a fast sensor for respiratory phase detection can be determined as t 10-90 = 60 / (10 · f max ), where 10 measurements per breath are assumed and f max indicates the maximum frequency of the expected breathing or ventilation in 1 / min.For the ventilation of a "giant" with an expected rate f max of 5 / min, the maximum rise time t 10-90 is therefore 1200ms; for an adult with an expected rate f max of 10 / min, the maximum rise time t 10-90 is 600ms; for a child with an expected rate f max of 20 / min, the maximum rise time t 10-90 is 300ms; for an infant with an expected rate f max of 50 / min, the maximum rise time t 10-90 is 120ms; for resuscitation with chest compressions at an expected rate f max of 100 / min, the maximum rise time t 10-90 is 60ms; and for slightly too rapid chest compressions at an expected rate f max of 110 / min, the maximum rise time t 10-90 is 54.5ms.

[0051] A high-resolution temporal sensor or fast sensor within the meaning of this application is therefore, with regard to the breathing or ventilation of an adult, a sensor with a rise time in the range of less than approximately 500ms, and a sensor with a longer rise time or slow sensor within the meaning of this application has a rise time of more than approximately 500ms.

[0052] In an advantageous embodiment of the invention, a fast sensor with a rise time of a maximum of 90ms is used for respiratory phase detection.

[0053] In a particularly advantageous embodiment of the invention, a fast sensor with a rise time of a maximum of 60ms is used for respiratory phase detection.

[0054] If the device according to the invention for measuring the content of at least one gas in exhaled air is designed to measure at least one of the measured values ​​detectable by means of the device for determining the breathing phase or by means of the further gas sensor according to the sidestream method, it preferably has a pumping device with which a gas sample can be pumped out of the main stream and transported into the area of ​​the respective sensor.

[0055] In one embodiment of the invention, the pumping device is designed as a suction pump.

[0056] In a particularly preferred embodiment of the invention, the device for measuring the concentration of at least one gas in exhaled air is additionally designed to measure the concentration of at least one gas in inhaled air.

[0057] For this purpose, the device for measuring the content of at least one gas in exhaled air has a further controllable valve, or the controllable valve is designed as a multi-way valve, wherein the valve paths can be opened or closed by means of the device for determining the breathing phase and the control unit in accordance with defined breathing phases.

[0058] In one embodiment of the invention, the device for measuring the content of at least one gas in exhaled air is designed for inspiratory oxygen measurement.

[0059] In a particularly preferred embodiment of the invention, the same sensor is used to determine the end-tidal oxygen content as is used to determine the inspiratory oxygen content.

[0060] Since the composition of the air used for ventilation is usually subject to only slight fluctuations, the oxygen content (or the content of another gas of interest) of the air supplied to a patient during the breathing cycle can be supplied to the O2 sensor (or another gas sensor measuring the content of the gas of interest), which is not needed to determine the etO2 value (or the content of the other gas of interest in the breathing phase of interest), so that the content of the respective gas in the inhaled air supplied to the patient and in the exhaled air can be determined alternately with the gas sensor.

[0061] A ventilation device according to the invention comprises at least one device according to the invention for measuring the content of at least one gas in exhaled air as described above.

[0062] The features of a method for measuring the content of at least one gas in exhaled air disclosed below are part of the invention both individually and in all feasible combinations.

[0063] A method according to the invention for measuring the content of at least one gas in exhaled air comprises at least the following method steps: 1. Determination of the breathing phase 2. Detection of whether a predetermined breathing phase is present in a breathing cycle 3. Introduction of a gas sample to at least one gas sensor 4. Isolation of the gas sample within the area of ​​the at least one gas sensor 5. Measurement of the introduced gas sample using the at least one gas sensor 6. Removal of the gas sample isolation

[0064] In advantageous embodiments, the aforementioned process steps run sequentially and continuously in a loop until the measurement is completed.

[0065] In a particularly preferred embodiment of the method according to the invention, the determination of the breathing phase is carried out continuously and in parallel with the other process steps.

[0066] In embodiments of the method according to the invention, the gas sample is supplied to the at least one gas sensor until the gas sample is isolated, optionally continuously and independently of the breathing phase, i.e. this step can also take place before the detection of the at least one predetermined breathing phase and optionally also before the (first) determination of the breathing phase.

[0067] In a preferred embodiment of the invention, the determination of the breathing phase is carried out by the continuous evaluation of temporally successively recorded measured values ​​of at least one sensor of a device for determining the breathing phase, wherein at least one sensor is used for temporally high-resolution measurement of the CO2 content, the O2 content, the humidity, the temperature, the pressure and / or the flow of the breathing gas, in particular the exhaled air.

[0068] In embodiments of the method, the respiratory phase is determined by measurements using the mainstream principle.

[0069] In other embodiments of the method according to the invention, the determination of the breathing phase is carried out by measurements using the sidestream principle.

[0070] In embodiments of the method, the respective breathing phase is detected by the measured values ​​exceeding or falling below a predetermined threshold or several predetermined thresholds.

[0071] For various measured values, the following are examples of threshold values ​​for detecting the breathing phase.

[0072] If a CO2 sensor is used to determine the breathing phase, in one embodiment of the invention a CO2 value > 2.5 vol.% indicates the expiratory phase. This value is typically around 5 vol.% during expiration. If the value subsequently falls below 0.5 vol.% CO2, an inspiratory phase is detected.

[0073] In another embodiment of the invention, the threshold value of the CO2 content in the inhaled air for determining the inspiratory phase is set to approximately 0.8 CO2max, corresponding to approximately 3.6 vol% CO2. This allows for faster detection of the inspiratory phase than a threshold of 0.5 vol% CO2, but may, depending on the actual CO2 concentrations reached during patient ventilation, pose problems with the robustness of the respiratory phase detection.

[0074] If an O2 sensor is used for respiratory phase detection, then in one embodiment of the invention, when a patient is ventilated with room air, a value for O2 > 20 vol.-% indicates an inspirational phase and a value for O2 < 19 vol.-% indicates an expiratory phase.

[0075] If an O2 sensor is used for respiratory phase detection, then in one embodiment of the invention, when a patient is ventilated with pure oxygen, a value for O2 > 98% indicates an inspirational phase and a value for O2 < 98 vol% indicates an expiratory phase.

[0076] If a flow sensor in the main stream is used for respiratory phase detection, in one embodiment of the invention a value for the flow > 0.5 l / min (in the direction of the patient) indicates an inspirational phase and a value for the flow < -0.5 l / min (coming from the patient) indicates an expiratory phase.

[0077] If a gas temperature sensor is used in the main flow for respiratory phase detection, then in one embodiment of the invention a value for temperature T > 32°C indicates an expiratory phase and a value for temperature T < 28°C indicates an inspirational phase.

[0078] If a humidity sensor is used to measure relative humidity (rH) for respiratory phase detection, then in one embodiment of the invention a value for rH > 90% indicates an expiratory phase because moist gas is exhaled, and a value for rH < 85% indicates an inspirational phase.

[0079] In other embodiments of the invention, the respiratory phase is detected by comparison with previously recorded measured values ​​of at least one respiratory cycle, preferably several respiratory cycles.

[0080] In embodiments of the invention, the detection of the breathing phase is carried out using dynamically adjustable threshold values, wherein the adjustment of the threshold values ​​is based on at least one detected parameter.

[0081] The use of algorithms, such as fuzzy logic, is also conceivable in embodiments of the invention for detecting the breathing phase. Other embodiments use the first or second derivative of the respective measured value signals to detect the breathing phase.

[0082] In any case, the isolation of the gas sample in the area of ​​the at least one gas sensor only occurs depending on the breathing phase if a defined breathing phase (e.g. the end-tidal region) has been detected.

[0083] In advantageous embodiments, the end-tidal region is detected by applying a delay after the detection of the end of the expiratory phase or the beginning of the inspiratory phase. The end-tidal region is the period approximately 200 ms to 50 ms before the end of the expiratory phase, such that, by appropriately controlling the controllable valve and / or the pump device, the respiratory gas from the end-tidal region is isolated in the area of ​​the gas sensor during the expiratory phase.

[0084] In a preferred embodiment of the invention, the sample gas from the last 30% of the expiratory phase is directed into the area of ​​the gas sensor for isolation.

[0085] The isolation of the gas sample in the area of ​​the at least one gas sensor is lifted as soon as the measurement of the concentration of the gas of interest in the gas sample is completed and / or as soon as a predetermined time has elapsed and / or as soon as an external signal indicates this.

[0086] In one embodiment of the method according to the invention, the gas sample is isolated in the area of ​​the at least one gas sensor by closing at least one valve path of a controllable valve and / or by switching off the pump device. In this embodiment, the isolation of the gas sample in the area of ​​the at least one gas sensor is lifted by opening at least one valve path of the controllable valve and / or switching on the pump device.

[0087] In embodiments of the invention, with the exception of the isolation phase, the supply of the breathing gas to be analyzed to the area of ​​the gas sensor is continuous or targeted immediately before the isolation phase, so that it is ensured that breathing gas from the breathing phase of interest is present in the area of ​​the at least one gas sensor during the isolation phase.

[0088] Any dead volume that may be present in a piping system must be taken into account when the breathing gas is introduced directly before the isolation phase. In such embodiments of the method, this dead volume is derived from the area of ​​the at least one gas sensor before the isolation phase. This is achieved, for example, by waiting a predefined time (delay) after the detection of the corresponding breathing phase. This delay must be selected depending on the flow rate of the sample gas or the pumping capacity of the pumping device, the volume of the piping line carrying the sample gas, and the geometry of the measuring device.

[0089] In embodiments of the method according to the invention, the detection of the breathing phase and the isolation of the gas sample do not take place in every breathing cycle, but regularly, for example in every xth breathing cycle (x ∈ N, x ≠1).

[0090] In preferred embodiments of the method, the isolated gas sample is measured and a moving average is calculated over the measured values ​​of the individual breaths recorded.

[0091] In a preferred embodiment, the method according to the invention is designed to determine the end-tidal O2 content (etO2 value) in the breathing air.

[0092] By means of the device according to the invention for measuring the content of at least one gas in exhaled air, as well as the method according to the invention for measuring the content of at least one gas in exhaled air, or a device according to the invention for ventilation, the combination of a fast respiratory phase sensor with a valve controllable depending on the detected respiratory phase makes it possible to use a slower gas sensor to measure the content of a specific gas in the exhaled air during a specific period of time in the respiratory cycle, thus enabling the use of more cost-effective and / or smaller and / or more accurate gas sensors.

[0093] The figures described below illustrate exemplary embodiments of the invention. They show: Figure 1: A schematic block diagram of a device according to the invention for measuring the concentration of at least one gas in exhaled air, Figure 2: Another schematic block diagram of an embodiment of a device according to the invention for measuring the concentration of at least one gas in exhaled air with further details, Figure 3: A perspective view of an exploded view of a part of a device for ventilation with a device for taking a gas sample from the exhaled air stream, Figure 4: A schematic flowchart of an embodiment of a method according to the invention for measuring the concentration of at least one gas in exhaled air, and Figure 5: A diagram illustrating the course of various measured quantities over a breathing cycle.

[0094] In Figure 1is a schematic block diagram of an embodiment according to the invention of a device for measuring the content of at least one gas in exhaled air (1) in the area of ​​a partially shown device for ventilation (20).

[0095] The device for measuring the concentration of at least one gas in exhaled air (1) is connected to the breathing airflow of the ventilation device (20) close to the patient via a connection device (2).

[0096] In the illustrated embodiment, the connection device (2) is designed as part of the breathing air line (22) and is arranged between the patient valve (21) and the mask (23) of the ventilation device (20), so that in the inspiration phase the breathing air directed to the mask (23) or to a patient flows through the connection device (2) just as in the expiration phase the breathing air directed from the mask (23) or from the patient to the patient valve (21) flows through the connection device (2).

[0097] The breathing air passed through the breathing air line (22) from the ventilation device (20) for the purpose of ventilating a patient is labelled O2 in the illustration and includes both the use of ambient air for ventilation and the use of oxygen-enriched air.

[0098] The device for measuring the concentration of at least one gas in exhaled air (1) further comprises a device for determining the breathing phase (3), which is connected to the connection device (2). Both arrangements that implement measurement using the main flow method and arrangements that implement measurement using the side flow method are embodiments according to the invention.

[0099] Furthermore, the illustrated embodiment of a device for measuring the content of at least one gas in exhaled air (1) includes a control device (4), a pump device (5), a controllable valve (6), a gas sensor (7) and an outlet (8).

[0100] Using the pump device (5), a gas sample can be pumped from the breathing air stream in the area of ​​the connection device (2).

[0101] With the aid of the control device (4) depending on the breathing phase determined by means of the device for determining the breathing phase (3) at least the controllable valve (6) can be controlled, so that the gas sample conveyed by means of the pump device (5) can be directed through an open valve passage to the gas sensor (7) or directly to the outlet (8).

[0102] The dashed arrows show optional configurations of a device according to the invention for measuring the content of at least one gas in exhaled air (1), which are explained below.

[0103] In a first modification according to the invention of the in Figure 1In the embodiment shown of a device for measuring the content of at least one gas in exhaled air (1), the pumping device (5) is connected to the device for determining the breathing phase (3) and the connection device (2) in such a way that gas samples conveyed by means of the pumping device (5) always also flow through the device for determining the breathing phase (3).

[0104] The pumping device (5) is arranged either upstream (flow direction along arrows B, D, F) or downstream (flow direction along arrows A, C, E) of the device for determining the breathing phase (3) in the direction of flow of the gas samples.

[0105] In one embodiment according to the invention, the pump device (5) can also be controlled by means of the control unit (4) depending on the breathing phase.

[0106] Figure 2Figure 1 shows a block diagram of a further embodiment according to the invention of a device for measuring the content of at least one gas in exhaled air (1) or of a device according to the invention for ventilation (20).

[0107] The device for measuring the concentration of at least one gas in exhaled air (1) is at least partially integrated into the housing of the ventilation device (20).

[0108] The connection device (2) is located in the area of ​​the patient valve (21) (not shown) and is connected via a sampling line (10) to a high-resolution temporal breathing phase sensor (9) of the device for determining the breathing phase (3), which is designed as a CO2 sensor. The pump device (5) is located downstream of the breathing phase sensor (9), so that breathing gas samples are always passed through the breathing phase sensor (9). The controllable valve (6), which is designed as a multi-way valve and, in the illustrated embodiment, has two inlets and three outlets, is located downstream of the pump device (5). The pump device (5) is connected to the first inlet, so that a gas sample can be pumped through the first inlet into the controllable valve (6).A branch (11) of the breathing air line (22) is connected to the second inlet. This branch is positioned upstream of the patient valve (21) in the direction of airflow towards the patient, ensuring that it always carries only the breathing air used for ventilation and not the exhaled air. The first outlet of the controllable valve (6) is a dead end (tightly sealed), the gas sensor (7) is connected to the second outlet, and the outlet (8) is connected to the third outlet.

[0109] With the help of the control unit (4) the controllable valve (6) can be switched in such a way as to depend on the breathing phase that the gas samples from the area of ​​the connection device (2) and from the branch (11) of the breathing air line (22) can be directed successively to the gas sensor (7) or directly to the outlet (8).

[0110] In the illustrated embodiment of the invention, the gas sensor (7) is designed as an O2 sensor, so that, depending on the valve state of the controllable valve (6), the O2 content of the breathing air directed towards the patient or the O2 content of the patient's exhaled air can be measured.

[0111] The ventilation device (20) further comprises a breathing air source (24), which may include an oxygen source for enriching the breathing air with oxygen, and a blower or valve (25) with which the breathing air can be actively conveyed (blower) or the flow of the breathing air can be controlled (valve).

[0112] Furthermore, the ventilation device (20) includes a mask (23) which can be placed on the patient's face for ventilation purposes.

[0113] In Figure 3, which serves among other things to illustrate the position of the connection device (2) in the system, is shown in a perspective view as an exploded view of a part of a device for ventilation (20) according to the invention in the area of ​​the patient valve (21).

[0114] The patient valve (21) is connected to the breathing air hose of the breathing air line (22). The patient valve (21) has a check valve, a control line and a pressure measuring hose.

[0115] A flow sensor (27) is connected to the patient valve (21) in the direction of the mask (23), which is connected via a connecting line (28) to a control unit or evaluation unit (not shown) of the device for ventilation (28).

[0116] The connection device (2) is connected to the flow sensor (27) and is linked to a sampling line (10). Breath gas samples from the area of ​​the connection device (2) can be conveyed through the sampling line (10) to the device (not shown) for measuring the concentration of at least one gas in exhaled air (1).

[0117] The connection device (2) is connected to the mask (23) or to a button (26) arranged on the mask (23) via a 90° connector, the button (26) being usable to trigger breaths of the ventilation device (20). Alternatively to a button (26), embodiments according to the invention can also have a remote control with which the corresponding function can be controlled.

[0118] The illustrated configuration of the patient tubing system is designed as a single-tube system. Alternatively, the invention can also be used in two-tube systems, in which the respiratory gas is first routed from the patient to the ventilator and then released there via an exhalation valve.

[0119] Figure 4 shows the process of an embodiment according to the invention of a method for measuring the content of at least one gas in exhaled air.

[0120] In this process, the respiratory phase is detected using a sample gas taken from a patient's exhaled air and a respiratory phase detection device (3). In the present embodiment, the CO2 content of the sample gas is determined using a respiratory phase sensor (9) designed as a CO2 sensor, and the current respiratory phase is determined based on threshold values. The first threshold value, which serves to detect an expiratory phase, is, in this embodiment of the method, a CO2 content of 3 vol%, which must be exceeded.

[0121] A predefined time period (delay) is then observed before the controllable valve (6) is switched. When the controllable valve (6) switches, the gas from the breath sample flows into the gas sensor (7), which in this embodiment is designed as an O2 sensor.

[0122] The O2 content of the breath gas sample is then measured using the gas sensor (7).

[0123] The respiratory phase detection continues continuously during this time, with the detection of an inspirational phase occurring by falling below a second threshold, which in this embodiment of the method is a CO2 content of 0.5 vol% that must be undercut.

[0124] If an inspiration phase is detected, a defined time is waited (delay) and then the controllable valve (6) is switched so that the gas of the breathing gas sample does not flow through the gas sensor (7) or past the gas sensor (7).

[0125] The previously mentioned isolation phase is the time during which no new sample gas flows to the gas sensor (7), i.e., the time between switching the controllable valve (6) after the detection of an inspiration phase and switching the controllable valve (6) after the detection of the subsequent expiration phase.

[0126] In Figure 5 The graph shows the flow rate of exhaled air and the CO2 and O2 content of the exhaled air over a breathing cycle in two connected diagrams. The abscissa (horizontal axis) represents time, and the ordinate (vertical axis) represents the volume flow rate [L / s] and the gas content [Vol.-%].

[0127] A respiratory cycle is divided into the phases inspiration phase (I) and expiration phase (II), with the last part of the expiration phase (II) being the end-tidal region (III).

[0128] During the inspiration phase, the volume flow of the respiratory gas initially rises sharply and then slowly decreases again. The O₂ content of the respiratory gas sample increases during the displacement of exhaled air from the gas sensor, rising from the end value of the previous expiratory phase (Il) of approximately 16 vol% to the O₂ content of the breathing air source of the ventilation device, here 20.9 vol%. Simultaneously, the CO₂ content of the respiratory gas sample falls from the end value of the previous expiratory phase (Il) of approximately 4.5 vol% to almost 0 vol%.

[0129] During the expiratory phase (II), the volume flow initially rises sharply in the opposite direction and then slowly decreases again. The O₂ content of the breath gas sample decreases from the end value of the preceding inspiratory phase (I) of approximately 20.9 vol% to the O₂ content of the patient's exhaled air, here 16 vol%, as the exhaled air is displaced from the gas sensor. Simultaneously, the CO₂ content of the breath gas sample rises from the end value of the preceding inspiratory phase (I) of almost 0 vol% to approximately 4.5 vol%.

[0130] In the end-tidal range (III), the values ​​of the volume flow rate and the O2 and CO2 concentrations undergo only very slight changes, so that these measured values ​​can be assumed to be almost constant in the end-tidal range. With regard to the O2 and CO2 concentrations, these are referred to as the concentration plateaus already mentioned.

Claims

1. Device for measuring the content of at least one gas in exhaled air (1) having at least one device for determining the respiratory phase (3), at least one control unit (4), at least one controllable multiport valve (6), having at least one inlet and at least two outlets, and at least one pumping device (5) and at least one gas sensor (7), wherein the device for determining the respiratory phase (3) can be used to determine the currently present respiratory phase in a respiratory cycle and the controllable valve (6) and the pumping device (5) can thus be actuated by the control unit (4) as a function of the detected respiratory phase, in that a respiratory gas sample of the respiratory air flowing towards or away from a patient depending on the respiratory phase can be passed through the gas sensor (7) or can be isolated in the region of the gas sensor (7), so that the content of a gas in the exhaled air can be determined in a predetermined section of the respiratory cycle with the aid of the gas sensor (7), wherein the device for determining the respiratory phase (3) has at least one respiratory phase sensor (9) which designed as a fast sensor with a rise time of less than 500 ms, wherein at least one gas sensor (7) is designed as an O2 sensor and the O2 sensor is designed as a slow sensor with a rise time of more than 500 ms for determining the O2 content in a respiratory gas sample and the controllable multi-port valve (6) is arranged downstream of the pumping device (5) and upstream of the gas sensor (7) in the direction of flow of the respiratory gas sample, wherein an inlet of the multi-port valve (6) is connected to the pumping device (5), an outlet of the multi-port valve (6) is connected to the gas sensor (7) and a further outlet of the multi-port valve (6) is connected to an outlet (8), so that the respiratory gas sample can be fed directly into the gas sensor (7) or to the outlet (8) depending on the valve position of the controllable multi-port valve (6).

2. Device (1) according to claim 1, characterized in that the device for determining the respiratory phase (3) is designed for measurement in the main-stream.

3. Device (1) according to one of claims 1 and 2, characterized in that the device for determining the respiratory phase (3) is designed for measurement in the secondary-stream.

4. Device (1) according to one of claims 1 to 3, characterized in that at least one respiratory phase sensor (9) is designed as a CO2 sensor, a temperature sensor, a humidity sensor, a flow sensor or as a pressure sensor.

5. Device (1) according to one of the preceding claims, characterized in that the controllable valve (6) is designed as a multiport valve having at least two inlets and at least two outlets, so that, depending on the respiratory phase, respiratory gas samples from different points of the system can be passed through the gas sensor (7) or can be isolated in the region of the gas sensor (7).

6. Device for ventilation (20) comprising at least one device for measuring the content of at least one gas in exhaled air (1) according to one of the preceding claims.

7. Method for measuring the content of at least one gas in exhaled air using a device for measuring the content of at least one gas in exhaled air (1) according to one of claims 1 to 5, comprising at least the following method steps: a. Determination of a respiratory phase with a respiratory phase sensor with a rise time of I ess than 500 ms b. Detection of whether a predetermined respiratory phase is present in a respiratory cycle c. Supply of a gas sample to at least one gas sensor (7) designed as an O2 sensor with a rise time of more than 500 ms d. Isolation of the gas sample in the area of at least one gas sensor (7) e. Measuring the supplied gas sample using at least one gas sensor (7) f. Terminating the isolation of the gas sample.

8. Method according to claim 7, characterized in that the determination of the respiratory phase and the detection of whether a predetermined respiratory phase is present is carried out continuously and in parallel with the other method steps.

9. Method according to one of claims 7 and 8, characterized in that the detection of the predetermined respiratory phase(s) is carried out on the basis of specified threshold values for the measurement values measured for determination of the respiratory phase, which measurement values must lie above or below the respective threshold values.

10. Method according to one of claims 7 to 9, characterized in that the respiratory phase is determined with the aid of a device for determining the respiratory phase (3)comprising at least one respiratory phase sensor (9), wherein the CO2 content, the humidity, the temperature, the flow and / or the pressure of the respiratory air flowing towards or away from a patient is measured with the aid of the at least one respiratory phase sensor (9).

11. Method according to one of claims 7 to 10, characterized in that the gas sensor (7) is used to measure the end-tidal oxygen content in the exhaled air of a patient.