Lin Y C, Shida K K, Hong S K
J Appl Physiol Respir Environ Exerc Physiol. 1983 Jan;54(1):166-71. doi: 10.1152/jappl.1983.54.1.166.
Five series of breath-hold (BH) experiments were conducted on eight male subjects with the purpose of partitioning the effects of apnea per se, hypercapnia, and hypoxia on the development and maintenance of BH bradycardia. All BH were 90 s in duration and were achieved by face immersion at room temperature. Of the five series of BH, one was a continuous BH and the remaining included rebreathing at 15-s intervals while the face remained immersed. Comparison of heart rate (HR) responses between the continuous BH with air and that interrupted every 15 s by rebreathing without improving the alveolar gas composition yields the attenuating effect of respiratory activity. The hypercapnic effect was calculated from the difference in HR responses between two series of BH with O2, in which hypoxia was not present and rebreathing was common to both; in one rebreathing was through a CO2 scrubber thus creating different alveolar CO2 levels in the two series. The effect of hypoxia was deduced by finding the difference between the total bradycardial response (continuous BH) and the summed effects of hypercapnia and apnea per se. By this procedure, it was found that apnea and hypoxia reduced the HR by 19 and 18%, respectively, from the pre-BH value, and hypercapnia increased HR by 6% from the pre-BH level, thus accounting for the total 31% reduction in HR in a continuous BH.
对八名男性受试者进行了五组屏气（BH）实验，目的是区分呼吸暂停本身、高碳酸血症和低氧血症对屏气性心动过缓的发生和维持的影响。所有屏气持续时间均为90秒，通过在室温下将面部浸入水中来实现。在这五组屏气实验中，一组是持续屏气，其余组包括在面部保持浸入水中的同时每隔15秒进行一次重复呼吸。比较持续屏气时的心率（HR）反应与每隔15秒通过重复呼吸中断屏气（而不改善肺泡气体成分）时的心率反应，可得出呼吸活动的减弱效应。高碳酸血症效应是通过两组吸氧屏气实验的心率反应差异计算得出的，这两组实验不存在低氧血症且都进行重复呼吸；其中一组重复呼吸通过二氧化碳洗涤器，从而使两组实验的肺泡二氧化碳水平不同。低氧血症的效应是通过计算总心动过缓反应（持续屏气）与高碳酸血症和呼吸暂停本身的综合效应之间的差异得出的。通过这个程序发现，呼吸暂停和低氧血症分别使心率较屏气前值降低了19%和18%，高碳酸血症使心率较屏气前水平增加了6%，从而解释了持续屏气时心率总共降低31%的原因。
