Multicomponent analysis of biomarkers in exhaled air using diode laser spectroscopy

We have proposed methods of multicomponent spectral analysis of exhaled air based on the use of tunable diode lasers to solve some problems in biomedical diagnostics. Simultaneous laser spectral analysis of CO and СO$_{2}$, CO and N$_{2}$O pairs near 4.7 $\mu$m can be used to examine gas exchange in the studies on the physiology of respiration and cardiovascular diagnostics conducted using various stress tests and for solving problems of anesthesiology and continuous monitoring ventilation–perfusion status. Simultaneous analysis of NO and СO$_{2}$ at approximately 5.4 $\mu$m can be useful for monitoring the breathing maneuver in studies of inflammatory processes in the distal lungs. Simultaneous detection of NH$_3$, СO$_{2}$, and C$_2$H$_4$ near 10.5 $\mu$m is promising for studies of general metabolism and major metabolic cycles. Simultaneous analysis of $^{13}$СO$_{2}$ and $^{12}$СO$_{2}$ near 2.05 $\mu$m can be used to measure the ratio of $^{13}$СO$_{2}$ to $^{12}$СO$_{2}$ when conducting isotopic breathing tests. The results of the analysis of promising spectral ranges and the relative position of the analytical lines in them are given. The possibility of simultaneous detection of several molecules under study in the proposed spectral regions was experimentally demonstrated, and laser transmission spectra were obtained. The proposed approach can be applied to the analysis of the microcomposition of exhaled air.