Breath testing with a mid-IR laser spectrometer

摘要

A mid-IR tunable diode laser absorption spectrometer (TDLAS) equipped with a multiple-pass gas cell was used to measure breath samples from a number of student volunteers at the University of Oklahoma. Test subjects included one to two pack-a-day cigarette smokers and non-smokers. The concentrations of four different molecules, N$-2$/O, $+12$/CO$-2$/, $+13$/CO$-2$/ and CO, were measured by each laser scan in the 2206.1 cm$+$MIN@1$/ to 2207 cm$+$MIN@1$/ spectral range. The average concentration of nitrous oxide (N$-2$/O) increased slightly for smokers versus non-smokers and was generally higher (12%) than the approximately 255 ppm concentration measured in ambient air. Carbon monoxide concentrations, however, were much higher in breath samples from cigarette smokers. Ambient concentrations of carbon monoxide, approximately 0.4 ppm, increased from approximately 1.0 ppm in non-smokers to levels over 13.4 ppm in smokers. These measurements provide clear evidence of the well-known effect that cigarette smoking has on replacing oxygen with carbon monoxide in human hemoglobin. Carbon dioxide concentrations of smokers were generally decreased by approximately 12%. Mid-IR laser measurements also provided $+13$/CO$-2$//$+12$/CO$-2$/ isotope ratio values, and smokers had a approximately 30% greater concentration of isotopic $+13$/C in their breath. The possible mechanisms for $+13$/CO$-2$/ isotopic increases are at present unknown. Overall, long-path TDL spectroscopy of exhalation products is a uniquely powerful tool. The TDL systems can be used for noninvasive diagnosis of a wide range of metabolisms and pathologies.