Environmental conditions at the South Col of Mount Everest and their impact on hypoxia and hypothermia experienced by mountaineers

Kent Moore,Paolo Stocchi,Paolo Cristofanelli,Paolo Bonasoni,John Semple

doi:10.1186/2046-7648-1-2

Abstract

BackgroundHypoxia and hypothermia are acknowledged risk factors for those who venture into high-altitude regions. There is, however, little in situ data that can be used to quantify these risks. Here, we use 7 months of continuous meteorological data collected at the South Col of Mount Everest (elevation 7,896 m above sea level) to provide the first in situ characterization of these risks near the summit of Mount Everest.MethodsThis is accomplished through the analysis of barometric pressure, temperature and wind speed data collected by an automatic weather station installed at the South Col. These data were also used as inputs to parameterizations of wind chill equivalent temperature (WCT) and facial frostbite time (FFT).ResultsThe meteorological data show clear evidence of seasonality, with evidence of pre-monsoon, monsoon and post-monsoon conditions. Low pressures, cold temperatures and high wind speeds characterize the pre- and post-monsoon periods with significant variability associated with the passage of large-scale weather systems. In contrast, the monsoon period is characterized by higher pressures, warmer temperatures and lower wind speeds with a pronounced reduction in variability. These environmental conditions are reflected in WCTs as low as −50°C and FFTs as short as 2 min during the pre- and post-monsoon periods. During the monsoon, the risk of cold injury is reduced with WCTs of order −20°C and FFTs longer than 60 min. The daily cycle in the various parameters is also investigated in order to assess the changes in conditions that would be experienced during a typical summit day. The post-monsoon period in particular shows a muted daily cycle in most parameters that is proposed to be the result of the random timing of large-scale weather systems.ConclusionsOur results provide the first in situ characterization of the risk of hypoxia and hypothermia on Mount Everest on daily, weekly and seasonal timescales, and provide additional confirmation as to the extreme environment experienced by those attempting to summit Mount Everest and other high Himalayan mountains.

Highlights

Hypoxia and hypothermia are acknowledged risk factors for those who venture into high-altitude regions
This study focused on two parameters: the wind chill equivalent temperature (WCT) and the facial frostbite time (FFT), defined as the time it takes for facial flesh to freeze
We introduce two new parameters: the wind chill temperature deficit (WCTD) that is defined as the difference between the observed temperature and the WCT, and the facial frostbite time deficit (FFTD) that is defined as the difference between the observed FFT and the FFT that would occur if the wind speed was zero

Summary

Introduction

Hypoxia and hypothermia are acknowledged risk factors for those who venture into high-altitude regions. The combination of low barometric pressure, cold temperatures and high winds that are common in highaltitude environments can compound hypoxic physiological stresses, resulting in an increased risk of hypothermia and frostbite [1,2,3] Towards this end, a comprehensive analysis of mortality on Mount Everest indicated that hypoxia and hypothermia were the leading causes of nontraumatic. Messner and Habler's successful ascent of the mountain in 1978 without the use of supplementary oxygen provided the definitive answer to the question as to the ability of humans to survive in this hypoxic environment [3] Notwithstanding this singular accomplishment, Mount Everest is so high that the low barometric pressure near its summit places humans exquisitely close to the tolerance limit for hypoxia, and changes in pressure near the summit as small as 4 hPa have been argued to be of physiological relevance [6,7]. During the ‘Into Thin Air’ storm of May 1996, a summit barometric pressure drop of a similar magnitude was estimated to have occurred, based on global meteorological datasets [11]

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