Supplemental oxygen effects on ventilation in acclimatized subjects exercising at 5700 m altitude

Abstract

Introduction: This study examines the effect of supplemental oxygen on acclimatized mountaineers at high altitude during rest and submaximal exercise.

Methods: Three healthy, acclimatized participants undertook nine periods of data collection lasting 10 min each over 2 consecutive days at 5700 m. These occurred at rest and exercise (40 and 80 W), breathing ambient air or supplemental oxygen (2 and 4 L m min') through an open-circuit breathing system.

Results: As minute ventilation increased during exercise, the fraction of inspired oxygen (FIO2) fell from 0.31 at rest to 0.23 with 2 L x min(-1) of oxygen and from 0.36 to 0.26 with 4 L x min(-1). Oxygen at both flow rates resulted in a significant increase in the arterial blood saturation of oxygen (SaO2) (Rest: 79% to 96% to 97%; 40 W: 80% to 95% to 97%; 80 W: 76% to 94% to 98%) and reduction in respiratory rate (RR) (Rest: 28 to 22 to 24; 40 W: 36 to 25 to 25; 80 W: 41 to 26 to 26). Tidal volume (VT, ml x s(-1)) was found to increase with the addition of oxygen (Rest: 959 to 844 to 969; 40 W: 1393 to 1834 to 1851; 80 W: 1558 to 2105 to 2215) and resulted in a non-significant reduction in minute ventilation (VE, L) (Rest: 25 to 17 to 21; 40 W: 46 to 45 to 43; 80 W: 61 to 51 to 53). No significant changes in heart rate were observed when oxygen was used (Rest: 78 to 62 to 71; 40 W: 90 to 91 to 96; 80 W: 105 to 102 to 101).

Conclusion: An open-circuit breathing system may increase SaO2 and reduce RR in acclimatized mountaineers during rest and sub-maximal exercise at 5700 m, though further research is needed to confirm this.