Effects of a 1-yr stay at altitude on ventilation, metabolism, and work capacity

Abstract

The hypoxic and hypercapnic ventilatory drive, gas exchange, blood lactate and pyruvate concentrations, acid-base balance, and physical working capacity were determined in three groups of healthy males: 17 residents examined at sea level (group I), 24 sea-level natives residing at 1,680-m altitude for 1 yr and examined there (group II), and 17 sea-level natives residing at 3,650-m altitude for 1 yr and examined there (group III). The piecewise linear approximation technique was used to study the ventilatory response curves, which allowed a separate analysis of slopes during the first phase of slow increase in ventilation and the second phase of sharp increase. The hypoxic ventilatory response for both isocapnic and poikilocapnic conditions was greater in group II and even greater in group III. The first signs of consciousness distortion in sea-level residents appeared at an end-tidal O2 pressure level (4.09 +/- 0.56 kPa) higher than that of temporary residents of middle (3.05 +/- 0.12) and high altitude (2.90 +/- 0.07). The hypercapnic response was also increased, although to a lesser degree. Subjects with the highest hypoxic respiratory sensitivity at high altitude demonstrated greater O2 consumption at rest, greater ventilatory response to exercise, higher physical capacity, and a less pronounced anaerobic glycolytic flux but a lower tolerance to extreme hypoxia. That is, end-tidal O2 pressure that caused a distortion of the consciousness was higher in these subjects than in those with lower hypoxic sensitivity. Two extreme types of adaptation strategy can be distinguished: active, with marked reactions of "struggle for oxygen," and passive, with reduced O2 metabolism, as well as several intermediate types.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced hypoxic ventilatory response with preserved blood oxygenation in yoga trainees and Himalayan Buddhist monks at altitude: evidence of a different adaptive strategy?

“…However, our study suggests that a lower increase in HVR does not preclude a successful adaptation, in agreement with the recent Wnding that elite climbers who reached the summit of Everest or K2 without oxygen support had lower increases in HVR during acclimatization (Bernardi et al 2006). Our results support the hypothesis of two possible strategies to cope with high altitude (Serebrovskaya and Ivanshkevich 1992): one based on increased chemoreXex responsiveness leading to hyperventilation (as in our Caucasian controls), the other based on "saving energy" by a more eYcient ventilation with moderate chemoreXex stimulation (as in yoga trainees, Buddhist monks and, to a lower extent, Sherpas). This second strategy seems also to reduce neurobehavioural impairment at altitude and to increase tolerance to extreme hypoxia (Hornbein et al 1989), by enhancing the capability to utilize the anaerobic glycolysis (Serebrovskaya and Ivanshkevich 1992).…”

A Rwandan spirometry and resting ventilation study

“…Therefore, part of the increase in ventilation was due to resting metabolism. At a slightly lower altitude of 1 680 m, a comparable ventilation was observed in males: 153 ± 5.7 mL.min -1 .kg -1 ; weight: 64.3 ± 1.5 kg (mean ± SD) (Serebrovskaya and Ivashkevich, 1992). At higher altitudes, the increase in ventilation is greater (Frisancho et al, 1999;Schoene, 1997;Serebrovskaya and Ivashkevich, 1992).…”