Abstract: Measurement device (1) for measuring the exhale capacity of a patient, includes a main body (2) with a through hole (3) with a blowing device (17) which has a rotation device (20) which is put in rotary motion through blowing, with a rotary speed depending on the intensity of the blowing, and the rotation of which is sensed by an optical sensor (6). The measuring device includes a cable (11) which is connected to the main body of the measurement device, and with a free end (11b) which is arranged to be connected to an audio input of a handheld general purpose computer unit (14), and in that the measurement device is arranged to, to the handheld computer unit, continuously deliver an analogue electric signal which carries information about rotary speed or air flow. A piece of software and a method are also described.