title: Does the estimation of light attenuation in tissue increase the accuracy of reflectance pulse oximetry at low oxygen saturations in vivo?
abstract: A new technique was validated in vivo in reflectance pulse oximetry for measuring low oxygen saturations. Two pairs of light emitter/detector diodes allow for estimation of light attenuation (LA) in tissue, which is assumed to be responsible for the inaccuracy of pulse oximetry at less than 70 % arterial oxygen saturation. For validation, 17 newborn piglets were desaturated stepwise from 21 % to 1.25 % inspiratory oxygen concentration during general anesthesia, and arterial oxygen saturation was measured with the reflectance pulse oximeter adjusted for LA in tissue, with a standard transmission pulse oximeter and a hemoximeter. LA in tissue could be quantified and was different between snout and foreleg (probability level (p) < 0.05). At arterial oxygen saturations above 70 %, the bias between the methods was at 0 %-1 % and the variability 4 %-5 %. From 2 % to 100 % arterial oxygen saturation, the reflectance pulse oximeter estimated oxyhemoglobin saturation more accurately than a conventional transmission pulse oximeter (p < 0.05). At low oxygen saturations below 70 %, the bias and variability of the reflectance pulse oximeter calibration were closer to the hemoximeter measurements than the transmission pulse oximeter (p < 0.05). The variability of the reflectance pulse oximeter was slightly lower than the traditional oximeter by taking into account the LA in tissue (9 % versus 11 % -15 %, ns), and thus, the quality of the individual calibration lines improved (correlation coefficient, p < 0.05).
authors.affiliation: Clinic for Anaesthesiology, Ludwig- Maximilians-Universität Munich, D-81377 Munich, Germany. hille.kisch-wedel@med.uni-muenchen.de
authors.forename: H
authors.initials: H
authors.lastname: Kisch-Wedel
authors.forename: P
authors.initials: P
authors.lastname: Bernreuter
authors.forename: G
authors.initials: G
authors.lastname: Kemming
authors.forename: M
authors.initials: M
authors.lastname: Albert
authors.forename: B
authors.initials: B
authors.lastname: Zwissler
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001158:Arteries / Q000502:physiology; D002138:Calibration; D005552:Forelimb / Q000098:blood supply; D008027:Light; D016014:Linear Models; D008954:Models, Biological; D009666:Nose / Q000098:blood supply; D010092:Oximetry / Q000295:instrumentation / Q000379:methods; D010100:Oxygen / Q000097:blood*; D010108:Oxyhemoglobins / Q000378:metabolism; D015203:Reproducibility of Results; D013552:Swine
chemical_list: D010108:Oxyhemoglobins; D010100:Oxygen