Multispecies breath analysis faster than a single respiratory cycle by optical-feedback cavity-enhanced absorption spectroscopy

Abstract

We demonstrate a first application, of optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) to breath analysis in a medical environment. Noninvasive monitoring of trace species in exhaled air was performed simultaneous to spirometric measurements on patients at Bichat Hospital (Paris). The high selectivity of the OF-CEAS spectrometer and a time response of 0.3 s (limited by sample flow rate) allowed following the evolution of carbon monoxide and methane concentrations during individual respiratory cycles, and resolving variations among different ventilatory patterns. The minimum detectable absorption on this time scale is about 3 x 10(-10) cm(-1). At the working wavelength of the instrument (2.326 microm), this translates to concentration detection limits of approximately 1 ppbv (45 picomolar, or approximately 1.25 microg/m(3)) for CO and 25 ppbv for CH(4), well below concentration values found in exhaled air. This same instrument is also able to provide measurement of NH(3) concentrations with a detection limit of approximately 10 ppbv; however, at present, memory effects do not allow its measurement on fast time scales.

Real-time breath gas analysis of CO and CO2 using an EC-QCL

“…True real-time detection requires a sampling and analysis system with low volume to ensure fast gas exchange times. Breath-cycle resolved, simultaneous detection of 1-3 compounds can today be achieved with the soft-ionization MS techniques [22,23] and laser spectroscopy [24][25][26][27], but only the latter method also offers the potential for compact and affordable instrumentation, which is desired in medical research and clinical practice.…”

“…Due to its low proton affinity, CO is rarely measured with standard soft-ionization MS, and eCO detection with solid state, chemiluminescence and near-infrared sensors lacks the required time-resolution for real-time BGA [31]. Recent efforts with laser spectroscopy [25,[32][33][34] revealed controversial results regarding the dependence of eCO on exhalation flow rate and breath-holding time.…”

Comparison of optical-feedback cavity-enhanced absorption spectroscopy and gas chromatography for ground-based and airborne measurements of atmospheric CO concentration

“…The sample volume inside the cavity is bellow 20 cm 3 (standard temperature and pressure conditions), and the pressure can be lowered down to a few mbar, opening field applications in trace detection where small volume samples are available, such as bubbles of gas trapped in ice cores for climate studies (Faïn et al, 2014;Rhodes et al, 2016;Grilli et al, 2014). Additionally, some OF-CEAS analysers can reach a high sensitivity (below 1 ppb for CO) associated with a short response time (of typically 1 s) that can be exploited in different applications such as in breath analysis to distinguish the respiratory phases (Ventrillard-Courtillot et al, 2009;Maignan et al, 2014) or during tropospheric and stratospheric airborne campaigns to deliver high spatial resolution data for atmospheric models Iannone et al, 2009a). OF-CEAS gas analysers are now commercialized by AP2E (ProCEAS), which offers presently the ability to measure the concentration of 15 molecular species at high sensitivity with high selectivity.…”

“…OF-CEAS-based measurements of CO have been conducted before around various applications, for example for in situ trace measurements on geothermal gases , for continuous and high-resolution measurement of air extracted from ice cores drilled out of polar glaciers (Faïn et al, 2014), and for breath analysis in different medical settings (Ventrillard-Courtillot et al, 2009;Maignan et al, 2014). ProCEAS analysers are now commercialized in the domains of industrial and air quality monitoring, with some very stringent applications such as air quality control onboard nuclear submarines.…”

“…The laser spectroscopy technique going under the name of OF-CEAS was introduced by Morville et al (2005) and has been further detailed in different publications (Kerstel et al, 2006;Kassi et al, 2006;Ventrillard-Courtillot et al, 2009;Faïn et al, 2014;Maignan et al, 2014;Morville et al, 2014).…”