Operation Everest II: Importance of Ventilation in Defense of Maximal Oxygen Uptake at Extreme Altitudes,
Abstract
The role of ventilation in the reduction of maximal aerobic power was studied in 8 subjects exposed to progressive simulated altitudes of 3962, 6096, 7468, and 8839 m (barometric pressures of 464, 347, 289, 240 Torr, respectively), as members of Operation Everest II, a 40-day simulated ascent of Mt. Everest. The mean (+ or - SEM) maximal oxygen uptake (VO2 max) was decreased from 4.13 + or - 0.20 at sea level (SL) to 1.2 + or - 0.08 1/min at P sub B 240 Torr. Maximal heart rate also decreased while arterial oxygen saturation was reduced. Maximal exercise ventilation at all barometric pressures compared to SL with a significant increase occurring at 464 Torr. Both frequency (f) and tidal volume (TV) contributed to the increase in VE (with f tending to be higher and TV lower for any VE at SL). A higher correlation was found between SaO2 and VO2 max than with heart rate and VO2 max. The rank order of subjects for VE/VO2 at SL was essentially the same as that at 240 Torr. VO2 max was reduced in all subjects 2 days after return to SL reaching 82% of the original mean while associated values for VE, f and TV were not different, suggesting that responses which improve or maintain exercise performance at altitude persist for at least several days after return to SL to the detriment of VO2 max. We concluded that ventilatory control is not lost under severe, progressive hypoxia; that a strong response is paramount to maintaining VO2 max; and that ventilation may be more critical than circulation in preserving VO2 max.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1986
- Accession Number
- ADA177874
Entities
People
- Allen Cymerman
- Bertron M. Groves
- John R. Sutton
- John T. Reeves
- Paul B. Rock
Organizations
- United States Army Research Institute of Environmental Medicine