Ferretti Guido, Costa Mario
Department of Physiology, University Medical Centre, 1 rue Michel Servet, CH-1211 4, Geneva, Switzerland.
Comp Biochem Physiol A Mol Integr Physiol. 2003 Sep;136(1):205-13. doi: 10.1016/s1095-6433(03)00134-x.
Several features of potential adaptation to breath-hold diving in diving populations and extreme divers are reviewed. Thermal adaptation consists of an improvement in cold tolerance, as witnessed by a decrease in critical water temperature, and implies an elevation of the shivering threshold associated with a greater body insulation. This is indicative of either a strong peripheral vasoconstriction or a more effective countercurrent heat exchange. Respiratory adaptation consists of a blunted ventilatory response to carbon dioxide and an enlargement of lung volumes. Finally, the occurrence of a diving response has been demonstrated. An extreme peripheral vasoconstriction is associated with a dramatic increase in arterial blood pressure. The consequent stimulation of arterial baroreceptors causes an extreme drop of heart rate. Bradycardia is not compensated by a higher stroke volume, with consequent decrease in cardiac output. This decrease, however, is not such as to undermine perfusion to vital organs. Redistribution of blood flow occurs, and some organs such as skeletal muscle may become unperfused, as indicated by the high blood lactate concentrations at low metabolic rate. It is not possible to state, however, whether these changes reflect genetic adaptations or an adaptive response to a prolonged environmental stress.
本文综述了潜水人群和极限潜水者对屏气潜水潜在适应的几个特征。热适应表现为耐寒能力的提高，临界水温降低即证明了这一点，这意味着与更好的身体隔热相关的寒颤阈值升高。这表明要么是强烈的外周血管收缩，要么是更有效的逆流热交换。呼吸适应包括对二氧化碳的通气反应减弱和肺容积增大。最后，已经证实了潜水反应的存在。极端的外周血管收缩与动脉血压的急剧升高有关。由此对动脉压力感受器的刺激导致心率急剧下降。心动过缓并没有通过更高的每搏输出量得到代偿，从而导致心输出量减少。然而，这种减少并不会损害对重要器官的灌注。血流会重新分布，一些器官如骨骼肌可能会出现无灌注，低代谢率下高血乳酸浓度就表明了这一点。然而，无法确定这些变化是反映了基因适应还是对长期环境压力的适应性反应。
