Fatemian M, Robbins P A
University Laboratory of Physiology, University of Oxford, Oxford OX1 3PT, United Kingdom.
J Appl Physiol (1985). 1998 Nov;85(5):1922-8. doi: 10.1152/jappl.1998.85.5.1922.
During ventilatory acclimatization to hypoxia (VAH), the relationship between ventilation (VE) and end-tidal PCO2 (PETCO2) changes. This study was designed to determine 1) whether these changes can be seen early in VAH and 2) if these changes are present, whether the responses differ between isocapnic and poikilocapnic exposures. Ten healthy volunteers were studied by using three 8-h exposures: 1) isocapnic hypoxia (IH), end-tidal PO2 (PETO2) = 55 Torr and PETCO2 held at the subject's normal prehypoxic value; 2) poikilocapnic hypoxia (PH), PETO2 = 55 Torr; and 3) control (C), air breathing. The VE-PETCO2 relationship was determined in hyperoxia (PETO2 = 200 Torr) before and after the exposures. We found a significant increase in the slopes of VE-PETCO2 relationship after both hypoxic exposures compared with control (IH vs. C, P < 0.01; PH vs. C, P < 0.001; analysis of covariance with pairwise comparisons). This increase was not significantly different between protocols IH and PH. No significant changes in the intercept were detected. We conclude that 8 h of hypoxia, whether isocapnic or poikilocapnic, increases the sensitivity of the hyperoxic chemoreflex response to CO2.
在对低氧的通气适应（VAH）过程中，通气量（VE）与呼气末二氧化碳分压（PETCO2）之间的关系会发生变化。本研究旨在确定：1）这些变化在VAH早期是否可见；2）如果存在这些变化，等碳酸血症和变碳酸血症暴露时的反应是否不同。通过对10名健康志愿者进行三次8小时的暴露研究：1）等碳酸血症性低氧（IH），呼气末氧分压（PETO2）=55托，PETCO2维持在受试者低氧前的正常水平；2）变碳酸血症性低氧（PH），PETO2 = 55托；3）对照（C），呼吸空气。在暴露前后的高氧状态（PETO2 = 200托）下测定VE-PETCO2关系。我们发现，与对照组相比，两种低氧暴露后VE-PETCO2关系的斜率均显著增加（IH与C相比，P < 0.01；PH与C相比，P < 0.001；协方差分析及两两比较）。方案IH和PH之间的这种增加没有显著差异。未检测到截距有显著变化。我们得出结论，8小时的低氧，无论是等碳酸血症还是变碳酸血症，都会增加高氧化学反射对CO2反应的敏感性。
