title: Instrumentation for the breath-by-breath determination of oxygen and carbon dioxide based on nondispersive absorption measurements.
abstract: This paper describes the development and evaluation of instrumentation for the breath-by-breath determination of oxygen and carbon dioxide in respiratory gases. The method is based on nondispersive absorption and uses the 145-nm absorption band for detection of oxygen and the 4.3-micron band for detection of carbon dioxide. A xenon discharge lamp with a sharp band at 147 nm was chosen as the source for the determination of oxygen, and a carbon dioxide discharge lamp with a sharp band at 4.3 micron was chosen for determination of carbon dioxide. A vacuum photodiode was used as the detector for oxygen, and a photoconductive cell with a built-in interference filter was used for detection of carbon dioxide. Plots of absorbance (A) vs concentration (C, %) were linear for oxygen and were nonlinear for carbon dioxide. Typical least-squares calibration equations were A = 0.020C + 0.02 for oxygen (0-100%) and A = 0.0012C2 + 0.050C + 0.008 for carbon dioxide (0-8%). Comparisons of computed (y) vs prepared (x) values for the concentrations given above were linear for both gases, yielding y = (1.00 +/- 0.01)x - 0.13 +/- 0.73 for oxygen and y = (1.07 +/- 0.02)x - 0.04 +/- 0.06 for carbon dioxide. The standard deviations were 1.2% at 50% oxygen and 1.5% at 4% carbon dioxide. Records are presented to illustrate breath-by-breath monitoring of these gases in a healthy subject.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393.
authors.forename: P B
authors.initials: PB
authors.lastname: Arnoudse
authors.forename: H L
authors.initials: HL
authors.lastname: Pardue
authors.forename: J D
authors.initials: JD
authors.lastname: Bourland
authors.forename: R
authors.initials: R
authors.lastname: Miller
authors.forename: L A
authors.initials: LA
authors.lastname: Geddes
mesh_terms: D000042:Absorption; D002245:Carbon Dioxide / Q000032:analysis*; D006221:Halothane / Q000032:analysis; D006801:Humans; D016018:Least-Squares Analysis; D009609:Nitrous Oxide / Q000032:analysis; D010100:Oxygen / Q000032:analysis*; D012129:Respiratory Function Tests / Q000295:instrumentation*
chemical_list: D002245:Carbon Dioxide; D009609:Nitrous Oxide; D010100:Oxygen; D006221:Halothane