The use of adaptive Kalman and Wiener filters and the empirical mode decomposition algorithm for processing the experimental signal obtained by the tunable diode laser absorption spectroscopy method has been reported to improve the sensitivity of the measurement of 13 CO 2 content in human expiratory air. A laser diode, tunable in the range 4860-4880 cm −1 near the wavelength of 2 µm, is used as a source. It has shown that the application of these filters ensures a detection sensitivity of 13 CO 2 at the level of 10 15 cm −3 , while the minimum detectable fraction of 13 CO 2 in a mixture with the 12 CO 2 is 3.8 • 10 −5 .