title: Validity of oxygen uptake measurements during exercise under moderate hyperoxia.
abstract: OBJECTIVE
  The validity of oxygen uptake in hyperoxia (FIO2 = 30%) measured by an automated system (MedGraphics, CPX/D system) was assessed during the simulation of gas exchanges during exercise with a mechanical system and during submaximal exercise by human subjects.
  
  
  METHODS
  The simulation system reproduced a stable and accurate VO2 for 30 min (sim-test). This trial was repeated nine times in normoxia and nine times in hyperoxia. Ten subjects also performed two submaximal exercises (55% of normoxic VO2max) on a cycle ergometer at the same absolute power in normoxia and in hyperoxia (ex-test).
  
  
  RESULTS
  There was a significant downward drift of the oxygen fraction measurement in hyperoxia (< or = 0.10% for FIO2 and FEO2) during sim-test, but VO2 measurement remained stable in the two conditions. There was also a downward drift of the oxygen fraction measurement in the two conditions (< or = 0.07% for FIO2) during ex-test. VO2 was significantly higher in hyperoxia (+4.6%), and this result was confirmed using a modified Douglas bag method.
  
  
  CONCLUSIONS
  These findings show that the CPX/D system is stable and valid for assessing VO2 in moderate hyperoxia.
authors.affiliation: Laboratoire de Physiologie-GIP Exercise, Université Jean Monnet, Faculté de Médecine Saint-Etienne, France. prieur@univ-st-etienne.fr
authors.forename: F
authors.initials: F
authors.lastname: Prieur
authors.forename: T
authors.initials: T
authors.lastname: Busso
authors.forename: J
authors.initials: J
authors.lastname: Castells
authors.forename: R
authors.initials: R
authors.lastname: Bonnefoy
authors.forename: H
authors.initials: H
authors.lastname: Benoit
authors.forename: A
authors.initials: A
authors.lastname: Geyssant
authors.forename: C
authors.initials: C
authors.lastname: Denis
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D006801:Humans; D018496:Hyperoxia; D008297:Male; D008954:Models, Biological; D010101:Oxygen Consumption; D015203:Reproducibility of Results