Heart rate variability during two sequential mountaineering expeditions

SummaryThis study was undertaken to assess the duration of altitude acclimatization retention in individuals after initial exposure to a maximum altitude of 5360 m during a mountaineering expedition.Spectral heart rate variability analysis accompanied by an assessment of acute mountain sickness using the Lake Louise Scoring System was performed during two sequential mountaineering expeditions to altitudes of 5360 m and 5642 m, with a period of 30 days between each expedition.Subjects displayed varying degrees of alterations in heart rate variability during the initial expedition, which indicated differing degrees of dysadaptation and stress development. Their Lake Louise Scores accounted for the presence of acute mountain sickness throughout the trip. During the subsequent expedition, the subjects’ heart rate variability measures were within the normal range, and there were no signs of acute mountain sickness.All three subjects who underwent step-by-step exposure to altitudes of 5360 m displayed differing degrees of alterations in heart rate variability in conjunction with differing degrees of acute mountain sickness. All subjects also developed acclimatization to hypoxic conditions at this altitude, which was preserved for 30 days, and was sufficient to prevent them from showing any significant alterations in heart rate variability when re-exposed to the same altitude.