Abstract

Selected time components of the cardiac cycle were determined during breathing in air, breathing through a snorkel during face immersion, apnea in air, and apnea during face immersion. Of primary interset were diastole (Dia), electromechanical lag (EML), isovolumetric contraction period (ICP), and ejection period (EP). Both apnea and face immersion significantly lengthened Dia and in combination resulted in a greater lengthening than would be expected if their effects were merely additive. The EP was shortened by apneabutlengthened by face immersion while EML was lengthened by apnea and shortened by face immersion. Due to the opposing nature of these reflexes on EP and EML, there was little changes in total systole during apneic face immersion. At this water temperature (22 to 24 degrees C), the effects of apnea were greater than those of face immersion. It was concluded that the effects of apneic face immersion on the heart probably involve two relatively independent components. Verf.-Referat