title: Hyperoxia reversibly alters oxygen consumption and metabolism.
abstract: OBJECTIVE
  Ventilation with pure oxygen (hyperoxic ventilation: HV) is thought to decrease whole body oxygen consumption (VO(2)). However, the validity and impact of this phenomenon remain ambiguous; until now, under hyperoxic conditions, VO(2) has only been determined by the reverse Fick principle, a method with inherent methodological problems. The goal of this study was to determine changes of VO(2), carbon dioxide production (VCO(2)), and the respiratory quotient (RQ) during normoxic and hyperoxic ventilation, using a metabolic monitor.
  
  
  METHODS
  After providing signed informed consent and institutional acceptance, 14 healthy volunteers were asked to sequentially breathe room air, pure oxygen, and room air again. VO(2), VCO(2), RQ, and energy expenditure (EE) were determined by indirect calorimetry using a modified metabolic monitor during HV.
  
  
  RESULTS
  HV reduced VO(2) from 3.4 (3.0/4.0) mL/kg/min to 2.8 (2.5/3.6) mL/kg/min (P < 0.05), whereas VCO(2) remained constant (3.0 [2.6/3.6] mL/kg/min versus 3.0 [2.6/3.5] mL/kg/min, n.s.). After onset of HV, RQ increased from 0.9 (0.8/0.9) to 1.1 (1.0/1.1). Most changes during HV were immediately reversed during subsequent normoxic ventilation.
  
  
  CONCLUSIONS
  HV not only reduces VO(2), but also increases the respiratory quotient. This might be interpreted as an indicator of the substantial metabolic changes induced by HV. However, the impact of this phenomenon requires further study.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Tübingen University Hospital, Eberhard-Karls University, Tübingen, Germany. patrick.lauscher@gmx.de
authors.forename: Patrick
authors.initials: P
authors.lastname: Lauscher
authors.forename: Sabine
authors.initials: S
authors.lastname: Lauscher
authors.forename: Harry
authors.initials: H
authors.lastname: Kertscho
authors.forename: Oliver
authors.initials: O
authors.lastname: Habler
authors.forename: Jens
authors.initials: J
authors.lastname: Meier
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000378:metabolism; D018592:Cross-Over Studies; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen