Procedure for combining a respiratory gas analysis and a functional pulmonary test by means of a device, wherein the device comprises the following characteristics: - a first mixed inlet / outlet opening (58), - a second mixed inlet / outlet opening (60 ), - a gaseous volume measurement device (66, 70) for determining a circulating volume of respiratory gas, - a gas analysis device (72) for analyzing respiratory gas, - a multi-way valve (10), which can be passed between at least a first combination of valve ways (A, B, C, D) and a second combination of valve ways (A, B, C, D), where - with the first combination of valve ways (A, B, C, D) of the multi-way valve (10) and avoiding the gas analysis device (72) a first gas route can be established between the first mixed inlet / outlet opening (58), the device for Gaseous volume measurement (66, 70) and the second mixed inlet / outlet opening (60), and - with the second combination of valve ways (A, B, C, D) of the multi-way valve (10) a second gas route can be established between the first mixed inlet opening / outlet (58), the gas analysis device (72), the gaseous volume measuring device (66, 70) and the second mixed inlet / outlet opening (60), wherein the method according to the invention comprises the next steps: - establishment of the first gas route, - inspiration by the influx of air from an outer chamber through the second mixed inlet / outlet opening (60) along the first gas route, in the direction of the first mixed inlet / outlet opening (58), - exhalation to check lung functionality with respect to the circulation of breathing gas through the gaseous volume measuring device (66, 70) along the first route of gas from the first mixed inlet opening / s alidade (58), in the direction of the second mixed inlet / outlet opening (60), - establishment of the second gas route while the aforementioned step is carried out, - conduction of circulatory breathing gas along the second gas route through the gas analysis dev
