Human breath trace gas content study by tunable diode laser spectroscopy technique

Abstract Measurements of carbon monoxide, ammonia, methane and carbon dioxide concentrations by registration of high resolution absorption spectra are described. A description of the automated tunable diode laser (TDL) system developed for simultaneous CO and CO 2 measure, and the TDL system developed for CH 4 and NH 3 measure is given. Calibration of concentration calculated on the base of a priori data on strength and broadening coefficients of detected lines is described. A clarified correct manner of value definition of spontaneous fraction of TDL' radiation allows an accuracy improvement of concentration measurement of several percent. The same level of CO surplus content of about 400–800 ppb in non-smoker's respiration was detected under different ambient conditions of CO content varied within one order of magnitude. A surplus content in human respiration of CH 4 equal to ∼3–8 ppm and NH 3 equal to 100–250 ppb were detected. The accumulation of CH 4 and NH 3 by the human organism seems to be rather negligible for a short time exposure, e.g. like smoking. Data obtained on non-invasive CO/CO 2 ratio detection in human breath shows that after 10–20 sec of breath holding time the organism's compensation reactions on acuity oxygen shortage for breath holding appear. Prospects for the development and application of diode laser spectroscopy to trace gas analysis in medicine are also discussed.