Donnelly P M, Daxini B V, Bye P T
Dept of Respiratory Medicine, Royal Prince Alfred Hospital, Camperdown, NSW, Australia.
Eur Respir J. 1994 Jul;7(7):1371-5. doi: 10.1183/09031936.94.07071371.
In order to obtain further insight into the adaptive mechanisms relating to gas exchange in anatomically small lungs, tests of mechanical lung function and gas exchange were made in an active young man, whose lung growth had been severely impaired due to pectus excavatum developed in childhood. We found our patient to have small (total lung capacity, 59% of predicted) but mechanically normal lungs. He had a normal cardiac output, a normal single-breath diffusing capacity (100% pred), and a high diffusion coefficient (148% pred) associated with a high pulmonary capillary blood volume (131% pred) at rest. Pulmonary distensibility (K) and elastic recoil were normal. During steady-state exercise he was unable to recruit further reserves of pulmonary capillaries, but this was not reflected in a plateau for oxygen consumption, which was presumably the result of an increased pulmonary capillary blood flow rather than volume. The recruitment of pulmonary capillary reserves in this young man has enabled him to maintain a normal maximum exercise capacity. In addition, the high stroke volume and a haemoglobin level in the high normal range (176 g.l-1) may have maintained his maximal exercise function, despite fewer alveolar units. This study suggests that, contrary to previous findings, loss of a major proportion of lung tissue need not impair exercise capacity. Patients with either small lungs or following pneumonectomy may benefit from physical training sufficient to optimize both an increase in cardiac output and recruitment of their existing alveolar capillary reserves.
为了更深入了解解剖学上较小肺部与气体交换相关的适应性机制，我们对一名活跃的年轻男性进行了肺功能和气体交换测试。该男性童年时因漏斗胸导致肺部发育严重受损。我们发现患者的肺较小（肺总量为预测值的59%），但机械功能正常。他的心输出量正常，单次呼吸弥散能力正常（为预测值的100%），静息时扩散系数较高（为预测值的148%），同时肺毛细血管血容量较高（为预测值的131%）。肺顺应性（K）和弹性回缩正常。在稳态运动期间，他无法进一步调动肺毛细血管储备，但这并未反映在耗氧量平台期，这可能是肺毛细血管血流量增加而非血容量增加的结果。该年轻男性肺毛细血管储备的调动使他能够维持正常的最大运动能力。此外，尽管肺泡单位较少，但较高的每搏输出量和处于高正常范围的血红蛋白水平（176 g.l-1）可能维持了他的最大运动功能。这项研究表明，与之前的发现相反，大部分肺组织的丧失不一定会损害运动能力。肺部较小或接受肺叶切除术后的患者可能会从足够的体育训练中受益，这足以优化心输出量的增加和调动其现有的肺泡毛细血管储备。
