Mou X B, Howard L S, Robbins P A
University Laboratory of Physiology, Oxford, UK.
Respir Physiol. 1995 Aug;101(2):139-43. doi: 10.1016/0034-5687(95)00027-b.
The ventilatory response to isocapnic hypoxia is biphasic, which makes any experimental assessment of the relationship between the acute (peak) ventilatory response and the level of hypoxia difficult. This study explored whether one particular protocol could be useful for determining this relationship. The protocol consisted of exposing subjects to seven different levels of isocapnic hypoxia, each of which lasted 50 sec. In order to test whether the order of the hypoxic exposure had any effect on the outcome, the steps were performed both in increasing and decreasing severity of hypoxia, and the ventilatory responses compared. Twelve subjects were studied, and each test was repeated four times in each subject. PETCO2 was held at 2 mmHg above resting throughout. The ventilations obtained at the lowest level of PETO2 employed were clearly different between the two protocols. However, provided that these ventilations were excluded, no significant differences were present between the results from the ascending and descending exposures (ANOVA). This finding suggests that the rate of change of PO2 in these protocols was sufficiently slow for a full ventilatory response to develop, but also sufficiently fast to prevent significant ventilatory depression from occurring.
对等碳酸血症性低氧的通气反应是双相的，这使得对急性（峰值）通气反应与低氧水平之间关系的任何实验评估都很困难。本研究探讨了一种特定方案是否有助于确定这种关系。该方案包括让受试者暴露于七种不同水平的等碳酸血症性低氧，每种低氧持续50秒。为了测试低氧暴露顺序对结果是否有任何影响，在低氧严重程度增加和降低两种情况下都进行了这些步骤，并比较了通气反应。研究了12名受试者，每个受试者的每项测试都重复进行了四次。整个过程中呼气末二氧化碳分压（PETCO2）保持在比静息值高2 mmHg的水平。在两种方案中，采用的最低呼气末氧分压（PETO2）水平下获得的通气量明显不同。然而，如果排除这些通气量，递增和递减暴露的结果之间没有显著差异（方差分析）。这一发现表明，在这些方案中，氧分压的变化速率足够缓慢，以使通气反应充分发展，但又足够快，以防止显著的通气抑制发生。
