REFLEX CARDIOVASCULAR RESPONSES TO SIMULATED DIVING.

Two techniques have been used to study further the diving reflex in man using eight male volunteer subjects. First is a method which allows diving to be simulated by a cold wet cloth placed on the face of an apneic subject. Second is a ballistocardiogram-analog computer system which permits a beat-to-beat determination of cardiac output and other cardiovascular measurements. A marked decrease in the heart, rates resulted during simulated diving. Associated with these decreases in heart rate were decreases in cardiac output, left ventricular work and mean forearm blood flow with an increase in the mean arterial pressure. Our observations all confirm that the diving reflex in man is qualitatively similar to that in marine mammals although considerably attenuated. Our results with the ballistocardiogram are consistent with the well described integrated oxygen conserving reflex which slows the heart, maintains central arterial pressure and redistributes blood flow. [ABSTRACT FROM AUTHOR]