An analysis device for analyzing expiration air of a patient, preferably for monitoring a patient under anesthesia during a medical intervention, is configured for determining, in the expiration air, a portion of an analyte contained in the expiration air. The analysis device preferably has a multi-capillary column for separating the expiration air to be analyzed and an ion mobility spectrometer in which gas components of the expiration air are ionized and accelerated toward a detection device. The analysis device can output signal excursions which are created by the ionized gas components of the expiration air which hit the detection device. A portion of the analyte which is to be determined and is contained in the expiration air to be analyzed is determined by a calibration of the signal excursion of the analyte to a signal excursion which is caused by the air moisture of expiration air.
