THE REGULATION OF RESPIRATION

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Abstract
The effects of mechanical asphyxia, of the administration of CO2 and intravenous injection of NaHCO3 on the carotid and femoral flow of blood were studied by a continuous thermoelectric method. Mechanical asphyxia had variable effects on the carotid flow. The variations were related to the phase of respiration during which asphyxia was initiated. It was concluded that the changes in flow are attributable to mechanical and reflex effects as well as to chemical changes entailed in suspended ventilation. To circumvent mechanical and reflex effects CO2 was administered in room air by normal and artificial ventilation. Such administrations increased the carotid and decreased the femoral flow. Subsequent administration of room air reversed the changes. Decreased ventilation, with accumulation of CO2 in the blood and tissues, increased the carotid flow of blood and decreased the femoral. Increased ventilation produced opposite effects. It was demonstrated that the changes in flow were not dependent on blood pressure. The reciprocal relation between the carotid and femoral flow suggests that circulatory adjustments following variations in CO2 content of the body occur in favor of the brain. The opposite effects of NaHCO3 and Na2CO3 on pulmonary ventilation were missing in volume-flow of blood. Both salts elicited an increased carotid and femoral flow. No explanation is offered for the difference in behavior of these salts.

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