Hempleman S C, Hughes J M
Department of Medicine, University of California, San Diego, La Jolla.
Respir Physiol. 1991 Feb;83(2):167-78. doi: 10.1016/0034-5687(91)90026-f.
Inert gas elimination studies in interstitial fibrosis ascribe all of the resting and most (58-83%) of the exercise (A-a)PO2 difference to ventilation-perfusion inequality. The previous paper (Hughes, J.M.B., D.N.A. Lockwood, H.A. Jones and R.J. Clark, (1991) Respir. Physiol. 83:155-166) [corrected] suggests from estimates of global DLO2/Q beta ratios a larger role for diffusion limitation on exercise. Gas exchange data from that paper was analyzed at rest and on exercise for five patients with interstitial fibrosis. Hypoxemia at rest was attributed to VA/Q inequality which was quantified using a log-normal lung model. DLO2 was calculated by Bohr integration. The base 10 LogSDQ at rest averaged 0.5 +/- 0.1 (SEM). On the assumption that VA/Q inequality remained unchanged on exercise, DLO2 (exercise) was estimated to be 14.3 +/- 1.9 ml.min-1.Torr-1. At that level of DLO2, diffusion limitation accounted for 36% +/- 8(SEM)% of the total (A-a)PO2 difference using the log-normal VA/Q model. But estimates of DLO2/Q beta assuming a homogenous lung, ascribed 96% of the (A-a)PO2 gradient on exercise to diffusion limitation. This discrepancy was shown to be related to the shape of the oxygen equilibrium curve and high alveolar PO2 values. On the other hand, analysis in terms of oxygen contents showed that 68 +/- 5% of the (A-a) content difference was accounted for by diffusion limitation. This differs substantially from estimates based on partial pressure alone.
间质性肺纤维化惰性气体清除研究表明，静息状态下以及大部分（58 - 83%）运动时的（肺泡 - 动脉血氧分压差）（A - a）PO₂差值均归因于通气 - 灌注不均。上一篇论文（休斯，J.M.B.，D.N.A.洛克伍德，H.A.琼斯和R.J.克拉克，（1991年）《呼吸生理学》83:155 - 166）[已修正]根据整体DLO₂/Qβ比值的估计，提示扩散限制在运动中起更大作用。对该论文中五例间质性肺纤维化患者静息和运动时的气体交换数据进行了分析。静息时的低氧血症归因于通气/血流比值（VA/Q）不均，采用对数正态肺模型对其进行量化。通过玻尔积分计算DLO₂。静息时以10为底的LogSDQ平均值为0.5±0.1（标准误）。假设运动时VA/Q不均保持不变，估计运动时的DLO₂为14.3±1.9 ml·min⁻¹·Torr⁻¹。在该DLO₂水平下，使用对数正态VA/Q模型，扩散限制占总（A - a）PO₂差值的36%±8（标准误）%。但假设肺均匀一致时对DLO₂/Qβ的估计表明，运动时（A - a）PO₂梯度的96%归因于扩散限制。这种差异被证明与氧平衡曲线的形状和高肺泡PO₂值有关。另一方面，根据氧含量分析表明，（A - a）含量差值的68±5%由扩散限制所致。这与仅基于分压的估计有很大不同。
