Near-infrared tunable diode laser absorptionspectroscopy-based determination of carbon dioxide in human exhaledbreath

摘要

A spectroscopic detection system for the accurate monitoring of carbondioxide (CO ) in exhaled breath was realized by tunablediode laser absorption spectroscopy (TDLAS) in conjunction with avertical-cavity surface-emitting laser (VCSEL) and a multipass cellwith an effective optical path-length of 20 m. The VCSEL diodeemitting light with an output power of 0.8 mW, covered thestrong absorption line of CO at6330.82 cm by drive-current tuning. Theminimum detectable concentration of 0.769‰ for CO detection was obtained, and a measurement precision of approximately100 ppm was achieved with an integration time of 168 s.Real-time online measurements were carried out for the detection ofCO expirograms from healthy subjects, differentconcentrations were obtained in dead space and alveolar gas. Theexhaled CO increased significantly with the increasingphysical activity, reaches its maximal value at the beginning ofrespiratory compensation and then decreased slightly until maximalexercise. The developed measurement system has a great potential to beapplied in practice for the detection of pulmonary diseases associatedwith CO retention.