General and local cold responses in humans after 2 weeks at high altitude

Abstract

To investigate the effects of a short-term high altitude residence (2 weeks between 4150 m and 6885 m in the Andes) on the general and local cold responses after descent, 11 subjects were submitted both to a whole body standard cold air test (SCAT, dry bulb temperature = 1°C, 2 h, nude, at rest) and to a local cold water test of the right upper limb (CWT, 5°C, 5 min) both before and after the expedition. Compared to before the expedition, a lower systolic blood pressure was observed after the high altitude residence [130.00 (SEM 3.35) mm Hg vs 140.40 (SEM 4.74) mm Hg at the end of CWT, P < 0.05] whereas no significant change either in diastolic blood pressure or in heart rate was found. All skin temperatures of the right upper limb were lowered (P < 0.05). During SCAT, body temperatures were unchanged (rectal and mean skin temperature, _sk) but metabolic heat production was slightly but significantly diminished [110 (SEM 4) W · m⁻² vs 125 (SEM 3) W · m⁻², P < 0.05] and heat debt increased [11.37 (SEM 1.11) kJ · kg⁻¹ vs 9.30 (SEM 2.30) kJ · kg⁻¹ , P < 0.05]. Moreover, the time of onset of continuous shivering (d) was shortened [8.20 (SEM 1.90) min vs 17.30 (SEM 3.60) min, P < 0.05] and the level of _sk observed at (d) was higher [25.70 (SEM 0.80)°C vs 23.57 (SEM 0.78)°C, P < 0.05] suggesting an increase in the sensitivity of the thermoregulatory system despite the slight decreased shivering activity observed. It was concluded that general and local cold tolerance were modified by a short-term residence at altitude and that the changes observed were not in accordance with general or (and) local cold adaptation. In contrast, high altitude sojourn could be a risk factor for frostbite of the extremities.