The Effect of Hypoxia on Behavioural Temperature Regulation – Report from the Si.mobil Ski Everest 2000 Expedition

During the Si.mobil Ski Everest 2000 expedition the hypothesis that hypoxia affects temperature perception was tested. Subjects (N = 5), all members of the expedition, provided subjective ratings of temperature perception on a 7-point scale and thermal comfort on a 4-point scale at Base Camp (BC, 5.360 m), Camp 1 (C1, 6.050 m), Camp 2 (C2, 6.500 m), Camp 3 (C3, 7.300m) and Camp 4 (C4, 7.950 m). In addition, we recorded oxygen saturation (SaO₂, %), axilla temperature (Tax), and tympanic temperature (Tty). All measurements were made at 21.00 hrs after the subjects had been resting in a sleeping bag within the tent for a minimum of 30 minutes. Average (±SD) SaO₂ decreased from 75 (± 8) % at BC, to 65 (± 5) % at C3. Although ambient temperature decreased with altitude from –9.6°C at BC to –27°C at C3, there were no significant differences in either Tax [BC: 36.1 (± 0.1)°C; C1: 35.7 (± 0.5)°C; C2: 35.9 (± 0.8)°C; C3: 36.8 (± 0.8)°C] or Tty [BC: 36.9 (± 0.3)°C; C1: 36.6 (± 0.5)°C; C2: 36.8 (± 0.8)°C; C3: 36.6 (± 0.8)°C] between measurements taken at the different camps. In contrast, there were significant changes (p < 0.001) in the perception of temperature from 4 (neutral) to 2 (cold) and in thermal comfort from 1 (comfortable) to 3 (uncomfortable). All subjects reported experiencing an increased perception of warmth at the onset of supplemental oxygen breathing at altitude. Assuming that the subjects’ thermal status was similar during all measurements, we conclude that hypoxia alters the perception of temperature and thermal comfort.