Hsia C C, Carlin J I, Wagner P D, Cassidy S S, Johnson R L
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235.
J Appl Physiol (1985). 1990 Jan;68(1):94-104. doi: 10.1152/jappl.1990.68.1.94.
Loss of a major portion of lung tissue has been associated with impaired exercise capacity, but the underlying mechanisms are not well defined. We studied the alterations in gas exchange during exercise before and after left pneumonectomy in three conditioned foxhounds. After pneumonectomy, minute ventilation and O2 consumption at comparable submaximal work loads were unchanged but arterial PCO2 at any work load was higher, implying that ventilatory response to CO2 was impaired. Arterial hypoxemia and an elevated alveolar-arterial O2 tension difference (AaDO2) developed during heavy exercise. Using the multiple inert gas elimination technique, we determined the distributions of ventilation-perfusion (VA/Q) ratios postpneumonectomy. Significant increase in VA/Q inequality developed during exercise while the foxhounds were breathing room air, accounting for an average of 42% of the total increase in AaDO2 while diffusion limitation accounted for 58%. While the animals were breathing hypoxic gas mixture, diffusion limitation accounted for an average of 88% of the total increase AaDO2. Cardiac output and O2 delivery were reduced at a given O2 consumption after pneumonectomy. After pneumonectomy, the animals reached O2 consumptions close to the maximum expected for normal dogs. Compensation for the impairment in O2 delivery post-pneumonectomy occurred mainly by an increase in hemoglobin concentration. Training probably played an important role in returning exercise capacity toward prepneumonectomy levels. We conclude that significant abnormalities in gas exchange develop during exercise after loss of 42% of lung tissue, but the animals demonstrate a remarkable ability to compensate for these changes.
肺组织大部分丧失与运动能力受损有关，但其潜在机制尚未明确。我们研究了三只经过训练的猎狐犬左肺切除术前、后运动期间气体交换的变化。肺切除术后，在相当的次最大工作负荷下，分钟通气量和耗氧量未变，但在任何工作负荷下动脉血二氧化碳分压均升高，这意味着对二氧化碳的通气反应受损。剧烈运动时出现动脉低氧血症和肺泡-动脉氧分压差（AaDO2）升高。使用多惰性气体消除技术，我们测定了肺切除术后通气-灌注（VA/Q）比值的分布。当猎狐犬呼吸室内空气时，运动期间VA/Q不均一性显著增加，平均占AaDO2总增加量的42%，而扩散限制占58%。当动物呼吸低氧气体混合物时，扩散限制平均占AaDO2总增加量的88%。肺切除术后，在给定的耗氧量下，心输出量和氧输送减少。肺切除术后，动物的耗氧量接近正常犬预期的最大值。肺切除术后氧输送受损的代偿主要通过血红蛋白浓度的增加来实现。训练可能在使运动能力恢复到肺切除术前水平方面发挥了重要作用。我们得出结论，在肺组织丧失42%后运动期间会出现显著的气体交换异常，但动物表现出了对这些变化的显著代偿能力。
