Abstract
We present a compact sensor for carbon monoxide (CO) in air and exhaled breath based on a room temperature interband cascade laser (ICL) operating at 4.69 µm, a low-volume circular multipass cell and wavelength modulation absorption spectroscopy. A fringe-limited (1σ) sensitivity of 6.5 × 10-8 cm-1Hz-1/2 and a detection limit of 9 ± 5 ppbv at 0.07 s acquisition time are achieved, which constitutes a 25-fold improvement compared to direct absorption spectroscopy. Integration over 10 s increases the precision to 0.6 ppbv. The setup also allows measuring the stable isotope 13CO in breath. We demonstrate quantification of indoor air CO and real-time detection of CO expirograms from healthy non-smokers and a healthy smoker before and after smoking. Isotope ratio analysis indicates depletion of 13CO in breath compared to natural abundance.
Highlights
Breath gas analysis (BGA) has recently received wide attention and is increasingly used in medical research and diagnostics [1]
We present a compact sensor for carbon monoxide (CO) in air and exhaled breath based on a room temperature interband cascade laser (ICL) operating at 4.69 μm, a lowvolume circular multipass cell and wavelength modulation absorption spectroscopy
A fringelimited (1σ) sensitivity of 6.5 × 10−8 cm−1Hz-1/2 and a detection limit of 9 ± 5 ppbv at 0.07 s acquisition time are achieved, which constitutes a 25-fold improvement compared to direct absorption spectroscopy
Summary
Breath gas analysis (BGA) has recently received wide attention and is increasingly used in medical research and diagnostics [1]. A fraction of eCO may originate from induced heme oxygenase in airway or lung tissue as a consequence of local oxidative stress and inflammation If this contribution could be distinguished from systemic CO and exogenous sources, eCO may be useful as biomarker for air pollution health effects and related respiratory diseases [7]. Real-time BGA can be used to measure the response to exposure or interventions and extract physiological parameters [10,11,12,13], and to optimize breath sampling procedures Another important, yet largely unexplored, feature is the possibility to obtain spatially resolved information about the respiratory tract. The sensor is applied to real-time detection of 12CO and 13CO exhalation profiles from healthy subjects and to investigate breath CO isotope ratios
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