title: Laser-based absorption spectroscopy as a technique for rapid in-line analysis of respired gas concentrations of O2 and CO2.
abstract: The use of sidestream analyzers for respired gas analysis is almost universal. However, they are not ideal for measurements of respiratory gas exchange because the analyses are both temporally dissociated from measurements of respiratory flow and also not generally conducted under the same physical conditions. This study explores the possibility of constructing an all optical, fast response, in-line breath analyzer for oxygen and carbon dioxide. Using direct absorption spectroscopy with a diode laser operating at a wavelength near 2 μm, measurements of expired carbon dioxide concentrations were obtained with an absolute limit of detection of 0.04% at a time resolution of 10 ms. Simultaneously, cavity enhanced absorption spectroscopy at a wavelength near 760 nm was employed to obtain measurements of expired oxygen concentrations with an absolute limit of detection of 0.26% at a time resolution of 10 ms. We conclude that laser-based absorption spectroscopy is a promising technology for in-line analysis of respired carbon dioxide and oxygen concentrations.
authors.affiliation: Department of Chemistry, University of Oxford, Oxford OX1 3PT, UK.
authors.forename: Beth
authors.initials: B
authors.lastname: Cummings
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Hamilton
authors.forename: Luca
authors.initials: L
authors.lastname: Ciaffoni
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Pragnell
authors.forename: Rob
authors.initials: R
authors.lastname: Peverall
authors.forename: Grant A D
authors.initials: GA
authors.lastname: Ritchie
authors.forename: Gus
authors.initials: G
authors.lastname: Hancock
authors.forename: Peter A
authors.initials: PA
authors.lastname: Robbins
mesh_terms: D000042:Absorption; D000465:Algorithms; D001944:Breath Tests / Q000295:instrumentation* / Q000379:methods*; D002245:Carbon Dioxide / Q000378:metabolism*; D005240:Feasibility Studies; D006801:Humans; D054023:Lasers, Semiconductor; D016014:Linear Models; D010100:Oxygen / Q000378:metabolism*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012119:Respiration; D012815:Signal Processing, Computer-Assisted; D013057:Spectrum Analysis / Q000295:instrumentation*; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen