Control of ventilation in extreme-altitude climbers

Abstract

Ten climbers who participated in the Nepal-Japan Kangchenjunga Expedition (altitude, 8,478-8,586 m) in 1984 were examined for their hypercapnic and isocapnic hypoxic ventilatory responses (HCVR and HVR) at sea level before and after the expedition. Five climbers who reached an altitude higher than 8,000 m, [designated high-performance climbers (HPC)] exhibited significantly higher HVR than five climbers who did not [low-performance climbers (LPC)]. On the other hand, no significant difference in HCVR was seen between HPC and LPC. Our results were in agreement with the findings reported by Schoene et al. (J. Appl. Physiol. 56: 1478-1483, 1984) obtained in the American Medical Research Expedition to Everest in 1981. Significant depression in HVR in five climbers was found even 35-40 days after the expedition, which was accompanied by decreased arterial partial pressure of CO2 and increased pH at rest. Hence, the effect of altitude acclimatization in the climbers exposed to extreme altitude may have still persisted at the time of the postexpedition study. Our results confirmed that HRV evaluated at sea level may be used as an indicator of a climber's capability at great high altitude.

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

“…Everest by SCHOENE et al (1984) and for Mt. 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).…”

“…HCVR was also evaluated as 4 'i/4 P02 and 4P02/4P02. Methodological details have been described elsewhere (MASUYAMA et al, 1986). Sleep studies by polysomnography were also done in eight climbers.…”

Effects of exercise and CO2 inhalation on intersubject variability in ventilatory and heart rate responses to progressive hypoxia

“…This intersubject variability is explained, at least in part, by genetic factors [16][17][18] and remains unchanged for many years in healthy subjects [19]. Low HVR values have been shown to be associated with poor exercise capacity at high altitude [6,7], severe nocturnal desaturation in sleep apnoea syndrome [8], hypercapnic respiratory failure in COPD [9][10][11], and possibly even fatal asthma attacks [12]. Since these conditions are all associated with exercise or hypercapnia, the strong influence on the pathophysiology of hypoxic chemosensitivity may be a consequence of enhancement of hypoxic chemosensitivity itself and also amplification of intersubject variability under such conditions.…”

“…It is also known that hypoxic chemosensitivity evaluated by HVR has a wide interindividual variability [4,5], and that the variability in hypoxic chemosensitivity is a factor accounting for intersubject variation in pathophysiological responses under a variety of hypoxic conditions. For instance, a lower HVR is shown to be associated with poorer performance at high altitude [6,7], more severe nocturnal desaturation in sleep apnoea syndrome [8], hypercapnic respiratory failure in chronic obstructive pulmonary disease (COPD) [9][10][11], and even near-death cases of bronchial asthma [12]. It is, thus, clinically important to examine the interaction of HVR with exercise and/or hypercapnia.…”

Deacclimation period in ventricular function after high altitude expedition.

“…Many reports have suggested that several months are needed for hypoxic deacclimation, particulary in the pulmonary function of rats (see references cited by FRIED and REID, 1984) and also in man (FoRSTER et al, 1971;MASUYAMA et al, 1986), with earlier recovery in the hematological changes. For cardiovascular function, on the other hand, such long-term studies are lacking, though some parameters in man seem to recover within several days after descent from highaltitude stay (VOGEL et al, 1967;BALASUBRAMANIAN et al, 1978), and rats with cardiac hypertrophy induced by intermittent exposure to simulated high altitude showed the regression with a half-time of about 7 days (SIZEMORE et al, 1973).…”