Arctic Aeromedical Laboratory. Aerospace Medical Division, Air Force Systems Command. Fort Wainwright, Alaska. Technical documentary report TDR-62-19. 46 p.
Arctic Aeromedical Laboratory. Aerospace Medical Division, Air Force Systems Command. Fort Wainwright, Alaska. Technical documentary report TDR-62-19. 46 p.
The effect of induced hypoxia on body temperature regulation and cardiopulmonary function is assessed in anesthetized dogs under warm, neutral and cold environments. Hypoxia acts differently to heat conservation (shivering) and heat dissipation (thermal panting) mechanisms: the former is suppressed, while the latter is facilitated. It is also found that the suppression of shivering is partly due to the hypocapnia which is produced under hypoxia. The lethal threshold of acutely induced hypoxia is at the inspiratory O2 level of approximately 3 per cent in the neutral and cold environments, whereas it is at 5 per cent in the warm environment. Under hypoxia, the total ventilation is increased two- to threefold. The alveolar ventilation, however, is augmented to a lesser degree with a progressive increase in physiological dead space. Contrary to respiration, the cardiac output is only slightly increased (less than 30 per cent over the control value) under hypoxia.