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

Abstract

A method and a device for measuring the content of at least one gas in exhaled air and to a device for ventilation. Due to the combination of a rapid respiratory phase sensor with a valve controllable depending on the detected respiratory phase, the use is made possible of a slower gas sensor to measure the content of a specific gas in the exhaled air during a certain period in the respiratory cycle so that the use of more economical and/or smaller and/or more accurate gas sensors is possible.

Claims

1-16. (canceled)

17. A device for measuring a content of at least one gas in exhaled air, comprising: at least one device for determining a respiratory phase; at least one control unit; at least one controllable valve and/or one pump device; and at least one gas sensor, wherein a current respiratory phase in a respiratory cycle is determinable by the device for determining the respiratory phase and the controllable valve and/or the pump device is actuable by the control unit according to the determined respiratory phase so that a respiratory gas sample of respiratory air that is flowing toward or away from a patient depending on the respiratory phase is passable through the gas sensor or isolatable in a region of the gas sensor, so that the content of the at least one gas in the exhaled air in a predetermined segment of the respiratory cycle is determined by the gas sensor.

18. The device according to claim 17, wherein the gas sensor is a slow sensor for determining the content of the gas in the respiratory gas sample.

19. The device according to claim 17, wherein the device for determining the respiratory phase comprises at least one respiratory phase sensor configured as a fast sensor.

20. The device according to claim 17, wherein the device for determining the respiratory phase is configured for main-stream measurement.

21. The device according to claim 17, wherein the device for determining the respiratory phase is configured for secondary-stream measurement.

22. The device according to claim 19, wherein the at least one respiratory phase sensor is a CO2 sensor, a temperature sensor, a humidity sensor, a flow sensor or a pressure sensor.

23. The device according to claim 17, wherein the gas sensor is an O2 sensor.

24. The device according to claim 17, wherein the controllable valve is a multiport valve comprising at least one input port and at least two output ports.

25. The device according to claim 17, wherein the controllable valve is a multiport valve comprising at least two input ports and at least two output ports, so that respiratory gas samples of various points of the system are passable through the gas sensor or isolatable in the region of the gas sensor according to the respiratory phase.

26. A device for ventilation, comprising at least one device for measuring a content of at least one gas in exhaled air according to claim 17.

27. A method for measuring a content of at least one gas in exhaled air, comprising the steps of: a. determining a respiratory phase; b. detecting whether there is a predetermined respiratory phase in a respiratory cycle; c. supplying a gas sample to at least one gas sensor: d. isolating the gas sample in a region of the at least one gas sensor; e. measuring the supplied gas sample with the aid of the at least one gas sensor; and f. terminating the isolation of the gas sample.

28. The method according to claim 27, including carrying out the determination of the respiratory phase and the detection of whether there is a predetermined respiratory phase continuously and in parallel to the other method steps.

29. The method according to claim 27, including carrying out the detection of the predetermined respiratory phase(s) based on specified threshold values for measurement values measured for determination of the respiratory phase, which measurement values must lie above or below the respective threshold values.

30. The method according to claim 27, including carrying out the respiratory phase with a device for determining the respiratory phase comprising at least one respiratory phase sensor, wherein CO2 content, humidity, temperature, flow and/or pressure of respiratory air that is flowing toward or away from a patient is measured with the at least one respiratory phase sensor.

31. The method according to claim 27, including measuring an end-tidal oxygen content in exhaled air of a patient with the gas sensor.

32. The method according to claim 27, including using a device for measuring the content of at least one gas in exhaled air comprising: at least one device for determining a respiratory phase; at least one control unit; at least one controllable valve and/or one pump device; and at least one gas sensor, wherein a current respiratory phase in a respiratory cycle is determinable by the device for determining the respiratory phase and the controllable valve and/or the pump device is actuable by the control unit according to the determined respiratory phase so that a respiratory gas sample of respiratory air that is flowing toward or away from a patient depending on the respiratory phase is passable through the gas sensor or isolatable in a region of the gas sensor, so that the content of the at least one gas in the exhaled air in a predetermined segment of the respiratory cycle is determined by the gas sensor.

Description

[0096] The figures described hereinbelow depict exemplary embodiments of the invention, where:

[0097] FIG. 1: shows a schematic block diagram of a device for measuring the content of at least one gas in exhaled air, which device is according to the invention,

[0098] FIG. 2: shows a further schematic block diagram of one embodiment of a device for measuring the content of at least one gas in exhaled air, which device is according to the invention, containing further details,

[0099] FIG. 3: shows a perspective view of an exploded drawing of part of a device for ventilation comprising a mechanism for collecting a gas sample from the respiratory air stream,

[0100] FIG. 4: shows a schematic flow chart of one embodiment of a method for measuring the content of at least one gas in exhaled air, which method is according to the invention, and

[0101] FIG. 5: shows a graph to illustrate the course of various measurement values over a respiratory cycle.

[0102] FIG. 1 depicts a schematic block diagram of one embodiment of the invention of a device for measuring the content of at least one gas in exhaled air (1) in the region of a partially shown device for ventilation (20).

[0103] The device for measuring the content of at least one gas in exhaled air (1) is connected near a patient to the respiratory air stream of the device for ventilation (20) via a connection mechanism (2).

[0104] In the embodiment depicted, the connection mechanism (2) is designed as part of the respiratory air line (22) and arranged between the patient valve (21) and the mask (23) of the device for ventilation (20), so that the respiratory air conducted toward the mask (23) or toward a patient in the inspiration phase flows through the connection mechanism (2) just like the respiratory air conducted in the expiration phase from the mask (23) or from the patient toward the patient valve (21).

[0105] The respiratory air conducted from the device for ventilation (20) through the respiratory air line (22) for ventilation of a patient is identified by O2 in the illustration and includes both the use of ambient air for ventilation and the use of oxygen-enriched air.

[0106] The device for measuring the content of at least one gas in exhaled air (1) further comprises a device for determining the respiratory phase (3), which is connected to the connection mechanism (2). Embodiments according to the invention include both arrangements which realize a measurement in a main-stream method and arrangements which realize a measurement in a secondary-stream method.

[0107] Furthermore, the embodiment shown of a device for measuring the content of at least one gas in exhaled air (1) comprises a controller (4), a pump device (5), a controllable valve (6), a gas sensor (7) and an outlet (8).

[0108] With the aid of the pump device (5), a gas sample is pumpable out of the respiratory air stream in the region of the connection mechanism (2).

[0109] With the aid of the controller (4), at least the controllable valve (6) is actuable according to the respiratory phase determined with the aid of the device for determining the respiratory phase (3), so that the gas sample conveyed with the aid of the pump device (5) is conductable through an opened valve path toward the gas sensor (7) or directly conductable toward the outlet (8).

[0110] The dashed arrows show optional configurations of a device for measuring the content of at least one gas in exhaled air (1), which device is according to the invention and which configurations will be explained hereinbelow.

[0111] In a first modification of the invention of the embodiment shown in FIG. 1 of a device for measuring the content of at least one gas in exhaled air (1), the pump device (5) is connected to the device for determining the respiratory phase (3) and to the connection mechanism (2) such that gas samples conveyed with the aid of the pump device (5) also always flow through the device for determining the respiratory phase (3).

[0112] In this case, the pump device (5) is arranged, in the flow direction of the gas samples, either upstream (flow direction along arrows B, D, F) or downstream (flow direction along arrows A, C, E) of the device for determining the respiratory phase (3).

[0113] Also conceivable in modifications of the invention is an arrangement of the pump device (5) between the controllable valve (6) and the gas sensor (7) or between the gas sensor (7) and the outlet (8).

[0114] In one embodiment of the invention, the pump device (5) is also actuable with the aid of the control unit (4) according to the respiratory phase.

[0115] In a further embodiment of the invention, the device for measuring the content of at least one gas in exhaled air (1) does not comprise a controllable vale (6) and, instead, only comprises at least one pump device (5) which is actuable with the aid of the control unit (4) according to the respiratory phase and by means of which a gas sample is conductable into the region of the gas sensor (7) and isolatable in the region of the gas sensor (7) according to the respiratory phase.

[0116] FIG. 2 shows a block diagram of a further embodiment of the invention of a device for measuring the content of at least one gas in exhaled air (1) or of a device for ventilation (20) according to the invention.

[0117] The device for measuring the content of at least one gas in exhaled air (1) is at least partially integrated into the housing of the device for ventilation (20).

[0118] Arranged in the region of the patient valve (21) is the connection device (2) (not depicted), which is connected via a withdrawal line (10) to a respiratory phase sensor (9) of the device for determining the respiratory phase (3), which respiratory phase sensor (9) is designed as a CO2 sensor and has high temporal resolution. Arranged downstream of the respiratory phase sensor (9) is the pump device (5), so that respiratory gas samples are always conducted through the respiratory phase sensor (9). Arranged downstream of the pump device (5) is the controllable valve (6), which is designed as a multiport valve and comprises two input ports and three output ports in the embodiment shown. Connected to the first input port is the pump device (5), so that a gas sample is pumpable by means thereof through the first input port into the controllable valve (6). Connected to the second input port is a branch (11) of the respiratory air line (22) that is arranged upstream of the patient valve (21) in the flow direction of the respiratory air toward the patient, so that said branch (11) always guides only the respiratory air used for ventilation and not the exhaled air. The first output port of the controllable valve (6) is a dead end (tightly sealed), what is connected to the second output port is the gas sensor (7), and what follows the third output port is the outlet (8).

[0119] With the aid of the control unit (4), the controllable valve (6) is switchable according to the respiratory phase in such a way that the gas samples are successively conductable from the region of the connection device (2) and from the branch (11) of the respiratory air line (22) toward the gas sensor (7) or directly toward the outlet (8).

[0120] In the embodiment of the invention that is depicted, the gas sensor (7) is designed as an O2 sensor, so that the O2 content of the respiratory air guided toward the patient or the O2 content of the exhaled air of the patient is measurable depending on the valve status of the controllable valve (6).

[0121] The device for ventilation (20) further comprises a respiratory air source (24), which optionally comprises an oxygen source for enriching the respiratory air with oxygen, and a fan or valve (25), by means of which the respiratory air is actively conveyable (fan) or the flow of the respiratory air is controllable (valve).

[0122] Furthermore, the device for ventilation (20) comprises a mask (23), which is fittable on the face of a patient for ventilation of the patient.

[0123] FIG. 3, which serves inter alia to illustrate the position of the connection device (2) in the system, depicts a perspective view of an exploded drawing of part of a device for ventilation (20) in the region of the patient valve (21), which device for ventilation (20) is according to the invention.

[0124] The patient valve (21) is connected to the respiratory air hose of the respiratory air line (22). The patient valve (21) comprises a check valve, a control line and a pressure measurement hose.

[0125] Following the patient valve (21) in the direction of the mask (23) is a flow sensor (27), which is connected via a connection line (28) to a control device or an evaluation unit (not depicted) of the device for ventilation (28).

[0126] Following the flow sensor (27) is the connection mechanism (2), which is connected to a withdrawal line (10). Conductable through the withdrawal line (10) are respiratory gas samples, from the region of the connection mechanism (2) toward the device for measuring the content of at least one gas in exhaled air (1), which device is not depicted here.

[0127] The connection mechanism (2) is connected via a 90° connection piece to the mask (23) and to a button (26) arranged on the mask (23), said button (26) being utilizable for triggering breaths of the device for ventilation (20). As an alternative to a button (26), embodiments of the invention can also comprise a remote control, by means of which the relevant function is controllable.

[0128] The depicted configuration of the patient hose system is designed as a one-hose system. As a deviation from this, the invention is also utilizable in two-hose systems, in which the respiratory gas is initially guided from the patient to the ventilator, where it is discharged via an exhaled air valve.

[0129] FIG. 4 shows the sequence of one embodiment of the invention of a method for measuring the content of at least one gas in exhaled air.

[0130] With the aid of a device for determining the respiratory phase (3), the respiratory phase is detected on the basis of a sample gas withdrawn from the respiratory air of a patient. In the present exemplary embodiment, the CO2 content of the sample gas is determined with the aid of a respiratory phase sensor (9) designed as a CO2 sensor and threshold values are used to determine which respiratory phase is currently present. In this embodiment of the method, the first threshold value, which is used for detection of an expiration phase, is a CO2 content of 3% by volume, which must be exceeded.

[0131] Thereafter, a predefined period of time (delay) is waited for before the controllable valve (6) is switched. After the controllable valve (6) has been switched, the gas of the respiratory gas sample flows into the gas sensor (7), which is designed as an O2 sensor in this embodiment.

[0132] This is followed by measurement of the O2 content of the respiratory gas sample with the aid of the gas sensor (7). Meanwhile, respiratory phase detection continues without stopping, with an inspiration phase being detected through values below a second threshold value, which in this embodiment of the method is a CO2 content of 0.5% by volume, which must be fallen short of.

[0133] If an inspiration phase is detected, a defined period (delay) is waited for and the controllable valve (6) is then switched, so that the gas of the respiratory gas sample does not flow through the gas sensor (7) and flows past the gas sensor (7).

[0134] The abovementioned isolation phase is the period in which no new sample gas flows to the gas sensor (7), i.e., the period between the switching of the controllable valve (6) after the detection of an inspiration phase up to the switching of the controllable valve (6) after the detection of the subsequent expiration phase.

[0135] FIG. 5 depicts, in two connected graphs, the course of the flow of the respiratory air and of the CO2 content and O2 content of the respiratory air over one respiratory cycle. The abscissa (horizontal axis) is the time axis and the ordinate (vertical axis) is the volumetric flow rate [I/s] or the gas content [% by volume].

[0136] One respiratory cycle is divided into the phases inspiration phase (I) and expiration phase (II), the last segment of the expiration phase (II) being given by the end-tidal region (III).

[0137] During the inspiration phase, the volumetric flow rate of the respiratory gas first rises steeply and then falls again slowly. During the displacement of the exhaled air from the gas sensor, the O2 content of the respiratory gas sample rises from the end value of the preceding expiration phase (II) of about 16% by volume to the O2 content of the respiratory air source of the device for ventilation, in this case 20.9% by volume. In parallel, the CO2 content of the respiratory gas sample falls from the end value of the preceding expiration phase (II) of about 4.5% by volume to almost 0% by volume.

[0138] During the expiration phase (II), the volumetric flow rate first rises steeply in the opposite direction and then falls again slowly. During the displacement from the gas sensor of the respiratory air conducted toward the patient for ventilation, the O2 content of the respiratory gas sample falls from the end value of the preceding inspiration phase (I) of about 20.9% by volume to the O2 content of the exhaled air of the patient, in this case 16% by volume. In parallel, the CO2 content of the respiratory gas sample rises from the end value of the preceding inspiration phase (I) of almost 0% by volume to about 4.5% by volume.

[0139] In the end-tidal region (III), the values for the volumetric flow rate and for the O2 content and CO2 content only undergo very slight changes, and so it can be assumed that these measurement variables have virtually constant values in the end-tidal region. Regarding the O2 content and CO2 content, reference is made to the concentration plateaus already mentioned above.