Taylor N A, Clarke J R
Department of Biomedical Sciences, University of Wollongong, Australia.
Acta Physiol Scand. 1993 Aug;148(4):371-8. doi: 10.1111/j.1748-1716.1993.tb09572.x.
Tracheal gas density breathing heliox at 31.3 atmospheres absolute (O2 at 0.42 ATA) is 6.287 g l-1, or approximately 5.5 times greater than air at 1 ATA. This constitutes a significant respiratory load, previously shown to induce respiratory adaptation. During a saturation dive to 31.3 ATA, five divers were exposed to this load for 16 days. This project aimed at investigating possible hysteresis in pulmonary function during dive compression, adaptation and decompression phases. Pulmonary function tests were performed at the surface in air, and at four pressure stops during compression and decompression, with divers breathing the helium-oxygen gas mixture. Significant hysteresis patterns were observed for pooled maximal voluntary ventilation, forced expired volume at 1 s, peak expiratory flow, and maximum expiratory flows (P < 0.05), with post-adaptation flows consistently exceeding those observed during compression. Two mechanisms may explain these observations. Differences may be attributable to positive effort-dependence in the forced expiratory flow; or it is possible the subjects adapted to the respiratory load by modifying neural input to airway smooth muscle, thereby modifying airway resistance.
在31.3个绝对大气压下呼吸氦氧混合气时（氧气分压为0.42ATA），气管气体密度为6.287g/L，约为1ATA下空气密度的5.5倍。这构成了显著的呼吸负荷，此前已证明会引发呼吸适应。在一次饱和潜水至31.3ATA的过程中，五名潜水员在该负荷下暴露了16天。该项目旨在研究潜水加压、适应和减压阶段肺功能中可能存在的滞后现象。在空气中的水面以及加压和减压过程中的四个压力停留点进行肺功能测试，潜水员呼吸氦氧混合气。对于合并的最大自主通气量、1秒用力呼气量、呼气峰值流速和最大呼气流量，观察到了显著的滞后模式（P<0.05），适应后的流量始终超过加压过程中观察到的流量。有两种机制可以解释这些观察结果。差异可能归因于用力呼气流量中的正用力依赖性；或者有可能受试者通过改变对气道平滑肌的神经输入来适应呼吸负荷，从而改变气道阻力。
