Cutaneous vascular and core temperature responses to sustained cold exposure in hypoxia

Abstract

We tested the effect of hypoxia on cutaneous vascular regulation and defense of core temperature during cold exposure. Twelve subjects had two microdialysis fibres placed in the ventral forearm and were immersed to the sternum in a bathtub on parallel study days (normoxia and poikilocapnic hypoxia with an arterial O 2 saturation of 80%). One fibre served as the control (1 mm propranolol) and the other received 5 mm yohimbine (plus 1 mm propranolol) to block adrenergic receptors. Skin blood flow was assessed at each site (laser Doppler flowmetry), divided by mean arterial pressure to calculate cutaneous vascular conductance (CVC), and scaled to baseline. Cold exposure was first induced by a progressive reduction in water temperature from 36 to 23• C over 30 min to assess cutaneous vascular regulation, then by clamping the water temperature at 10• C for 45 min to test defense of core temperature. During normoxia, cold stress reduced CVC in control (−44 ± 4%) and yohimbine sites (−13 ± 7%; both P < 0.05 versus precooling). Hypoxia caused vasodilatation prior to cooling but resulted in greater reductions in CVC in control (−67 ± 7%) and yohimbine sites (−35 ± 11%) during cooling (both P < 0.05 versus precooling; both P < 0.05 versus normoxia). Core cooling rate during the second phase of cold exposure was unaffected by hypoxia (−1.81 ± 0.23• C h −1 in normoxia versus −1.97 ± 0.33• C h −1 in hypoxia; P > 0.05). We conclude that hypoxia increases cutaneous (non-noradrenergic) vasoconstriction during prolonged cold exposure, while core cooling rate is not consistently affected.

Thermoregulatory responses to combined moderate heat stress and hypoxia

“…The lack of difference in sweating but altered cutaneous blood flow responses during hypoxia in this study may seem counterintuitive, but other researches has shown that variations in regional sweating are not explained by local variations in cutaneous blood flow . The slightly reduced core temperature elevation during heating in Hypoxia in this study despite similar heating protocols (e.g., similar mean skin temperatures and duration of heating) is intriguing and is consistent with previous research that reported lower core temperatures during combined cold and hypoxic stress . However, similar local sweat rates and similar or lower local cutaneous blood flow responses would not contribute to a lower core temperature elevation during heating in hypoxia.…”

Dynamic Adaptation of the Peripheral Circulation to Cold Exposure

“…With acute cold exposure in a laboratory setting, Simmons et al. [70–72] studied the effect of hypoxia on cutaneous vascular conductance during cold exposure. Data from these three studies are mixed, suggesting both increased and decreased cutaneous vasoconstriction in the forearm.…”

“…Based on field acclimation studies, one intriguing possibility is that hypoxic exposure itself, irrespective of cold exposure, potentiates CIVD response and local thermal response to cold. With acute cold exposure in a laboratory setting, Simmons et al [70][71][72] studied the effect of hypoxia on cutaneous vascular conductance during cold exposure. Data from these three studies are mixed, suggesting both increased and decreased cutaneous vasoconstriction in the forearm.…”

Emerging Environmental and Weather Challenges in Outdoor Sports

“…In cold environment, practitioners are more liable to make mistakes or wrong cognitive choices, as their decision-making deteriorates (e.g., rugby players dropping the ball on the coldest match days) [123], potentially increasing the risk of being injured as well. Prolonged exposition to cold environments can cause hallucinations, while the combination of cold and hypoxia exacerbate the magnitude of physiological adaptations [123]; for instance, hypoxia is known to increase cutaneous vasoconstriction during prolonged cold exposure [129]. Finally, "cold urticarial" arises during re-warming after cold exposure.…”