Moderate hypoxia does not affect the zone of thermal comfort in humans

Abstract

The zone of thermal comfort was determined during normoxia and hypoxia in 15 healthy normothermic young subjects. Subjects dressed only in shorts/shorts and bikini top donned a water-perfused suit and assumed a supine position on a bench. The ambient temperature was maintained at a mean (SD) of 25.7 (0.3) degrees C. The thermal comfort zone was determined by increasing the temperature of the water perfusing the suit from cool to warm. During the heating process, subjects were instructed to report when their perception of the thermal stimulus provided by the suit changed from unpleasant to pleasant, and again from pleasant to unpleasant. The boundaries of the thermal comfort zone were assumed to be the temperatures of the water perfusing the suit at the time the subjects reported a change in the affective component of their thermal perception. In normoxia, subjects inspired room air and in hypoxia a gas mixture containing 10% O(2) in N(2). Tympanic temperature was similar in the normoxia and hypoxia conditions (P>0.05). The average (SD) lower and upper limits of the thermal comfort zone were 30.5 (1.5) and 34.7 (3.3) degrees C, respectively, during normoxia, and 30.5 (1.7) and 35.1 (3.4) degrees C, respectively, during hypoxia. No significant differences were observed between the normoxia and hypoxia conditions (P>0.05). Also, no gender-related differences were observed in the characteristics of the thermal comfort zone. The results of the present study indicate that acute hypoxic exposure simulated in the present study does not affect the zone of thermal comfort in humans.

Effects of normobaric hypoxic bed rest on the thermal comfort zone

“…Moreover, previous findings that neither hypoxia nor inactivity/ unloading per se alter behavioural thermoregulatory responses (Golja and Mekjavic, 2003;Golja et al, 2005;Yogev et al, 2010) are confirmed by the present results, and extended to include that the combination of hypoxia and inactivity/unloading does not affect behavioural thermoregulation. No statistically significant differences were found when observing the separate and combined effects of normobaric hypoxia and/or inactivity/unloading.…”

“…However, the results reported by Golja and Mekjavic (2003) and Golja et al, (2005) indicate that behavioural temperature regulation does not appear to be compromised by moderate hypoxia. Present results from the HAMB condition confirm previous findings (Golja and Mekjavic, 2003;Golja et al, 2005), and extend them to suggest that neither acute nor prolonged exposure to moderate hypoxia affects behavioural thermoregulation.…”

“…It has been suggested that a normobaric hypoxic exposure induces slowing of neural activity in the sensor-to-effector pathway, but does not affect the threshold for cutaneous detection of either warmth or cold (Malanda et al, 2008). However, the results reported by Golja and Mekjavic (2003) and Golja et al, (2005) indicate that behavioural temperature regulation does not appear to be compromised by moderate hypoxia. Present results from the HAMB condition confirm previous findings (Golja and Mekjavic, 2003;Golja et al, 2005), and extend them to suggest that neither acute nor prolonged exposure to moderate hypoxia affects behavioural thermoregulation.…”

“…They reported a reduced sensitivity to cold during the hypoxic exposure, suggesting that alteration in thermal perception may affect the individual's perception of thermal comfort and consequently attenuate thermoregulatory behaviour during cold exposure at altitude. The few studies that have investigated the effect of hypoxia on behavioural thermoregulatory responses in humans have reported that hypoxia does not seem to affect human behavioural thermoregulation (Golja and Mekjavic, 2003;Golja et al, 2005). The bedrest experimental model is commonly used as a ground-based simulation model for studying the effects of microgravity on certain physiological systems (Fortney et al, 1996).…”

Activation of autonomic thermoeffectors preceding the decision to behaviourally thermoregulate in resting humans

“…Given that shivering and sweating are not required for thermal behaviour to be initiated, the present study provides mechanistic insights in support of previous studies that have identified no effect of hypoxia (Golja & Mekjavic, ; Golja et al . ) and bed rest (Yogev et al . ) on thermal behaviour.…”