Hsia C C, Carlin J I, Ramanathan M, Cassidy S S, Johnson R L
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-9034.
Respir Physiol. 1991 Jan;83(1):11-21. doi: 10.1016/0034-5687(91)90089-2.
In three foxhounds, diffusing capacity for carbon monoxide (DLCO) was reduced by 25-30% after left pneumonectomy. Based on previous morphometric data in animals and physiologic data in humans, this reduction should not result in any impairment in gas exchange. However, experimental evidence indicates that diffusion limitation develops during exercise after pneumonectomy. Our objective is to determine whether this diffusion limitation to gas exchange can be predicted from physiologic measurements of DLCO. DLCO measured by the rebreathing technique was translated into diffusing capacity for O2 (DLO2) using an average conversion factor for canids obtained morphometrically (Weibel et al., Respir. Physiol. 54: 173-188, 1983). Arterial O2 saturation (SaO2) at various intensities of steady state exercise was calculated from DLO2 and measured values of O2 consumption, alveolar PO2, hemoglobin and arterial pH, and compared to observed SaO2. After pneumonectomy, SaO2 declined progressively with increasing exercise load. In all dogs, the observed pattern of arterial O2 saturation could be predicted from DLCO measured at similar work loads. The relationship between predicted (Pr) and observed (Ob) SaO2 is: SaO2(Pr) = 22.73 + 0.77SaO2(Ob), r = 0.92. The slope is significantly less than 1.0 (P less than 0.005), indicating that other factors must also contribute to arterial desaturation. We conclude that physiologic measurement of DLCO is a meaningful indicator of diffusion limitation to gas exchange. In the foxhound, a modest reduction in DLCO significantly impairs O2 transport during exercise; but other gas exchange abnormalities, e.g. ventilation perfusion inhomogeneity, must also develop.
在三只猎狐犬中，左肺切除术后一氧化碳弥散量（DLCO）降低了25% - 30%。根据先前动物的形态学数据和人类的生理学数据，这种降低不应导致气体交换出现任何损害。然而，实验证据表明，肺切除术后运动期间会出现弥散受限。我们的目的是确定这种气体交换的弥散受限是否可以通过DLCO的生理学测量来预测。使用通过形态学方法获得的犬科动物平均转换系数（Weibel等人，《呼吸生理学》54: 173 - 188, 1983），将通过重复呼吸技术测量的DLCO转换为氧气弥散量（DLO2）。根据DLO2以及测量得到的氧气消耗量、肺泡氧分压、血红蛋白和动脉血pH值，计算出稳态运动不同强度下的动脉血氧饱和度（SaO2），并与观察到的SaO2进行比较。肺切除术后，随着运动负荷增加，SaO2逐渐下降。在所有犬只中，观察到的动脉血氧饱和度模式可以根据相似工作负荷下测量的DLCO进行预测。预测的（Pr）和观察到的（Ob）SaO2之间的关系为：SaO2(Pr) = 22.73 + 0.77SaO2(Ob)，r = 0.92。斜率显著小于1.0（P < 0.005），表明其他因素也必定导致动脉血氧饱和度降低。我们得出结论，DLCO的生理学测量是气体交换弥散受限的一个有意义指标。在猎狐犬中，DLCO适度降低会显著损害运动期间的氧气运输；但其他气体交换异常，例如通气灌注不均匀，也必定会出现。
