Eucapnic hypoxia lowers human cold thermoregulatory response thresholds and accelerates core cooling
| Autor: | Matthew D. White, Gordon G. Giesbrecht, Wu Mp, Chad E. Johnston, Gerald K. Bristow |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Adult
Male Physiology Sweating Body Temperature Oxygen Consumption Hypocapnia Heart Rate Physiology (medical) Immersion Hyperventilation medicine Humans Hypoxia Chemistry Shivering Carbon Dioxide Thermoregulation Hypothermia Hypoxia (medical) medicine.disease Cold Temperature Regional Blood Flow Vasoconstriction Anesthesia Exercise Test Room air distribution Female medicine.symptom Body Temperature Regulation |
| Zdroj: | Journal of Applied Physiology. 80:422-429 |
| ISSN: | 1522-1601 8750-7587 |
| Popis: | Hypoxia lowers the basic thermoregulatory responses of animals and humans. In cold-exposed animals, hypoxia increases core temperature (Tco) cooling rate and suppresses shivering thermogenesis. In humans, the experimental effects of hypoxia on thermoregulation are equivocal. Also, the effect of hypoxia has not been separated from that of hypocapnia consequent to hypoxic hyperventilation. To determine the isolated effects of hypoxia on warm and cold thermoregulatory responses and core cooling during mild cold stress, we examined the Tco thresholds for sweating, vasoconstriction, and shivering as well as the core cooling rates of eight subjects immersed in 28 degrees C water under eucapnic conditions. On 2 separate days, subjects exercised on an underwater cycle ergometer to elevate Tco above the sweating threshold. They then rested and cooled until they shivered vigorously. Subjects inspired humidified room air during the control trial. For the eucapnic hypoxia trial, they inspired 12% O2-balance N2 with CO2 added to maintain eucapnia. Eucapnic hypoxia lowered the Tco thresholds for vasoconstriction and shivering by 0.14 and 0.19 degrees C, respectively, and increased core cooling rate by 33% (1.83 vs. 1.38 degrees C/h). These results demonstrate that eucapnic hypoxia enhances the core cooling rate in humans during mild cold stress. This may be attributed in part to a delay in the onset of vasoconstriction and shivering as well as increased respiratory heat loss during hypoxic hyperventilation. |
| Databáze: | OpenAIRE |
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