title: Supplemental oxygen and hyperbaric treatment at high altitude: cardiac and respiratory response.
abstract: BACKGROUND
  The most effective treatment for high altitude sickness is prompt descent. However, rapid descent is sometimes impossible and alternative solutions are desirable. Supplemental oxygen at ambient pressure and hyperbaric oxygen in a hyperbaric tent have both been demonstrated to improve symptoms and increase arterial oxygenation (SaO2) in those with high altitude sickness; however, their use in combination has not previously been described in a controlled study.
  
  
  RESULTS
  In this feasibility study, the SaO2 of six healthy, well-acclimatized participants rose from 76.5 to 97.5% at 4900 m and 72.5 to 96.0% at 5700 m following the administration of oxygen via a nasal demand circuit (33 ml of oxygen per pulse) inside a hyperbaric tent (107 mmHg above ambient barometric pressure) (p < 0.05). This contrasted with an increase in SaO2 to 89.5% at 4900 m and 86.3% at 5700 m with only supplemental oxygen and an increase in SaO2 to 92.8% (4900 m) and 90.5% (5700 m) with only hyperbaric exposure. In addition, combining treatments also resulted in an increase in tidal volume (29.0 and 31.0%) and minute ventilation (12.0 and 23.0%) together with a fall in heart rate (15.0 and 17.0%) at 4900 and 5700 m, respectively. No significant differences in heart rate, tidal volume, minute ventilation, SaO2, or respiratory rate were seen when hyperbaric treatment and supplemental oxygen were directly compared.
  
  
  CONCLUSIONS
  In healthy, well-acclimatized subjects the combination of hyperbaric exposure and supplemental oxygen has a noteworthy effect on physiological parameters at high altitude. Awareness of this knowledge may enhance the treatment of patients with life-threatening high altitude sickness.
authors.affiliation: Center for Sleep and Respiratory Neurobiology, University of Pennsylvania Schools of Medicine and Nursing, 420 Guardian Drive, Philadelphia, PA 19104-6096, USA. gwrodway@hotmail.com
authors.forename: George W
authors.initials: GW
authors.lastname: Rodway
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Windsor
authors.forename: Nigel D
authors.initials: ND
authors.lastname: Hart
mesh_terms: D000328:Adult; D000532:Altitude Sickness / Q000628:therapy*; D001784:Blood Gas Analysis; D004864:Equipment and Supplies; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000295:instrumentation / Q000379:methods*; D008297:Male; D009051:Mountaineering / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D012129:Respiratory Function Tests
chemical_list: D010100:Oxygen