The invention relates to a measurement device and a method for analyzing asample gas byinfrared absorption spectroscopy. The measurement device comprises: ameasurementchamber with the sample gas to be analyzed, a laser being arranged in relationto themeasurement chamber such that light being emitted from the laser radiatesthrough themeasurement chamber, a detection device detecting the light being emitted fromthe laser andradiated through the measurement chamber, and an evaluation unit evaluatingsignalsgenerated by the detection device regarding a light absorption occurred in themeasurementchamber. Provision is made that the laser is a narrowband emitting laser, theline width of whichis smaller or equal to the width of an infrared absorption line to be measuredof the sample gas,the laser is designed and arranged such that the laser frequency is variedperiodically within adefined spectral range, wherein the laser frequency and its variation arechosen such that atleast one infrared absorption line to be measured of the sample gas lies inthe defined spectralrange, and the detection device is designed and arranged such that it detectsthe light beingemitted from the laser and radiated through the measurement chamber in such atime-resolvedmanner that the light absorption can be determined frequency-resolved withinthe definedspectral range, wherein the detection device carries out a single absorptionmeasurement within-5 s or faster. Furthermore, the measurement device is suited and can bearranged tomeasure the respiratory gas of a human or animal as sample gas, wherein therespiratory gasexchanges in the measurement chamber only by the respiration of the human oranimal, andthe respiratory resistance of the measurement device is less than 60 mbar.
