Relationship of hypoxic ventilatory response to exercise performance on Mount Everest

Abstract

At very high altitude, exercise performance in the human sojourner may depend on a sufficient hypoxic ventilatory response (HVR). To study the relationship of HVR to exercise performance at high altitude, we studied HVR at sea level and 5,400 m and exercise ventilation at sea level, 5,400 m, and 6,300 m in nine members of the American Medical Research Expedition to Everest. The relationship of HVR between individuals was maintained when HVR was repeated after acclimatization to 5,400 m (P less than 0.05). There was a significant correlation in all subjects between HVR and ventilatory equivalent during exercise at sea level (r = 0.704, P less than 0.05). Subjects were then grouped into high (H) and low (L) HVR responders (ventilation increase to end-tidal PO2 of 40 Torr = 21.2 +/- 5.4 and 5.6 +/- 0.9 1 X min-1, respectively. At low and moderate levels of exercise, ventilation at sea level and after acclimatization to 6,300 m was higher in the high HVR group. At 6,300 m blood O2 saturation (Sao2%) decreased from rest to maximum exercise: H = 8.3 +/- 1.8%, L = 20.0 +/- 2.5% (P less than 0.01). HVR correlated inversely in all subjects with the decrease in Sao2 from rest to maximum exercise (P less than 0.05). Climbers with the highest HVR values reached and slept at higher altitudes. We conclude that the relative value of HVR in our group of climbers was not significantly altered after acclimatization; HVR predicts exercise ventilation at sea level and high altitude; the drop in Sao2% that occurs with exercise is inversely related to HVR; and sojourners with high HVR may perform better at extreme altitude.

Periodic breathing at high altitude and ventilatory responses to O2 and CO2.

“…Kangchenjunga by MASUYAMA et al (1986). Though this study did not find any relationship between daytime climbing performance and HVR (all climbers reached the summit), the exercise test done at 5,360 m in this expedition revealed that the higher HVR a climber had, the less desaturation during exercise (HASAKO et al, 1988), which agreed with the result of SCHOENE et al (1984). However, we should take cycle time of PB into account.…”

Air to Muscle O2Delivery during Exercise at Altitude

“…Consequently, the ODC was shifted to the left in hypoxia, improving by 8 percentage units the level of Sao 2 at exhaustion compared with the Sao 2 expected from the ODC corresponding to normoxia (Calbet et al, 2003a). The drop in Sao 2 that occurs with exercise in hypoxia is inversely related to HVR, explaining why sojourners with high HVR may perform better at extreme altitude (Schoene et al, 1984). In addition, replacing the N 2 -O 2 gas mixture by helium-O 2 (both with a Fio 2 ¼ 0.11) allowed increases in V Emax by 31%, Pao 2 by 17%, Sao 2 by 6%, and Vo 2max by 14% (Esposito and Ferretti, 1997), thus emphasizing the impact of hyperventilation on O 2 transport and exercise capacity in hypoxia.…”

Ventilatory Chemosensitivity, Cerebral and Muscle Oxygenation, and Total Hemoglobin Mass Before and After a 72-Day Mt. Everest Expedition

“…Ventilation rapidly increases upon acute hypoxic exposure, and this hypoxic ventilatory response (HVR) is generally presumed to enable better performance at altitude by maintaining arterial oxygen saturation levels (Schoene et al, 1984;Masuyama et al, 1986). Alternatively, a strong HVR has also been proposed to be a negative adaptation that reduces ventilatory reserve at altitude (Bernardi et al, 2006), while hyperventilation and the resultant hypocapnia may reduce cerebral blood flow (Poulin et al, 2002;Ainslie and Poulin, 2004).…”