Landsberg P G
S Afr Med J. 1975 Apr 5;49(15):626-30.
The bradycardial response to the diving reflex, which occurs in man and in diving animals, is thought to be a physiologically protective oxygen-conserving mechanism whereby the animal is kept alive during submergence. The physiology and nervous pathways are not yet fully understood, but several investigators have pointed out the potentially fatal outcome of an accentuated diving reflex. the CO2 content of the peripheral venous blood has been proved variable and unpredictable during the hyperventilation-breath-hold dive cycle in man. A group of 8 male divers (average age 34 years) was investigated during breathhold dives to 3,3 m in a swimming pool. Heart rates were recorded and compared at various stages during breath-hold and SCUBA (self-contained underwater breathing apparatus) dives, viz. when resting on the surface, breath-holding, hyperventilating and swimming underwater. Two divers performed extreme breathhold endurance tests lasting 135 seconds underwater. All divers had a tachycardia after hyperventilation and a bradycardia after breathhold diving, lasting 80-100 seconds. Extrasystoles were recorded during some of the breathhold dives. Prolonged submergence caused extreme bradycardia (24/min) with central cyanosis. Bradycardia during diving may be a physiological )2-conserving reflex or the start of a pathophysiological asphyxial response.
人类和潜水动物都会出现的潜水反射所引起的心动过缓，被认为是一种生理保护性的氧保存机制，通过这种机制动物在水下时能够存活。其生理机能和神经通路尚未完全明了，但一些研究人员指出了潜水反射增强可能带来的致命后果。在人类过度通气-屏气潜水周期中，已证实外周静脉血中的二氧化碳含量是可变且不可预测的。一组8名男性潜水员（平均年龄34岁）在游泳池中进行33米的屏气潜水时接受了调查。记录并比较了屏气潜水和使用水肺（自给式水下呼吸器）潜水不同阶段的心率，即当在水面休息时、屏气时、过度通气时以及在水下游泳时的心率。两名潜水员进行了长达135秒的极限屏气耐力测试。所有潜水员在过度通气后出现心动过速，在屏气潜水后出现心动过缓，持续80 - 100秒。在一些屏气潜水中记录到了早搏。长时间潜水会导致极度心动过缓（每分钟24次）并伴有中心性发绀。潜水时的心动过缓可能是一种生理性的氧保存反射，也可能是病理生理性窒息反应的开始。
