The Role of the Cardiovascular Response in the Resistance to Asphyxia of Avian Divers

Abstract

Abstract H ollenberg , N. K. and B. U vnäs . The role of the cardiovascular response in the resistance to asphyxia of avian divers. Acta physiol. scand. 1963. 58. 150–161. — Submersion asphyxia in unanaesthetized ducks produced a characteristic circulatory response consisting of a pronounced bradycardia, increased blood pressure, decreased splanchnic and skin blood flow and little change in skeletal muscle blood flow. The circulatory responses to asphyxia were completely abolished by denervation of the carotid chemoreceptors and baroceptors. Continuous measurement of arterial oxygen saturation showed a biphasic fall during asphyxia, decreasing very rapidly during the first 40 sec, and then falling much less rapidly at the time splanchnic and skin blood flow reached a minimum. It was concluded that the marked ability of divers to withstand asphyxia is related to their circulatory response. The net result of the circulatory response is to decrease the oxygen supply to areas that can easily withstand an oxygen deficit for a limited period, conserving the available oxygen stores for tissues more sensitive to a lack of oxygen. Evidence is presented which suggests that the above described response is due to chemoreceptor stimulation.