Method and device for measuring the content of at least one gas in exhaled air

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 multi-port valve, having at least one inlet and at least two outlets, 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, wherein the device for determining the respiratory phase has at least one respiratory phase sensor which configured as a fast sensor having a rise time of less than 500 ms, wherein the at least one gas sensor is an O2 sensor configured as a slow sensor having a rise time of more than 500 ms for determining O2 content in the respiratory gas sample, wherein the controllable multi-port valve is arranged downstream of the pump device and upstream of the gas sensor in a direction of flow of the respiratory gas sample, wherein the inlet of the multi-port valve is connected to the pump device, one of the outlets of the multi-port valve is connected to the gas sensor and another of the outlets of the multi-port valve is connected to an outlet, so that the respiratory gas sample is fed directly into the gas sensor or to the outlet depending on a valve position of the controllable multi-port valve.