PULMONARY LIMITATIONS TO EXERCISE AFTER PNEUMONECTOMY

在海平面上，正常人的运动限制是由 那些控制或决定最大心脏的因素 产量及其分配。可能的例外是 奥运级别运动员的胸腔和肺泡泵功能 气体交换不会对运动施加重要限制 正常人的海平面。然而，在高海拔地区的正常人中 或在海平面上有功能性肺损伤的患者中， 肺和胸腔会对人体造成额外的重要限制 锻炼能力。限制可能产生于：1) 呼吸肌机械负荷增加；2)受损 低氧扩散量或低氧交换的肺泡气体交换 驾驶压力(高海拔)或区域匹配效率低下 通风和血液流动；3)对 右室后负荷增加所致的心血管功能 夸张的心肺相互作用，例如，增加 肺和心窝僵硬，导致 来自肺的舒张期充盈或心脏降压反射。 这些潜在锻炼来源的相对重要性 肺部疾病的界限不清楚，也很难接近 在人类身上进行实验。已经有了很多动物模型 为检查运动限制机制而开发的 由心血管功能受损引起，但实际上没有 探讨肺损伤所致受限的机制 功能。通过狗的全肺切除，我们可以增加 可重复使用的方式提高了刚性，降低了扩散能力 并增加肺血管阻力。这将是 进而增加呼吸功，减少肺泡储备 气体交换，增加右室后负荷，还可能 减少心脏的预负荷。在过去的31年半里，我们有 开发了检测每一种潜在可能性的技术 清醒犬使用最低限度运动的限制来源 侵入性方法和慢性内固定的有限使用。我们的 计划是使用这些方法来表征自然和 运动中潜在限制来源的重要性 因肺实质丧失而丧失的能力。

At sea level, exercise limitation in normal man is imposed by those factors which control or determine the maximal cardiac output and its distribution. With the possible exception of Olympic class athletes, pump function of the thorax and alveolar gas exchange do not impose an important limitation on exercise at sea level in normal man. However, in normal man at high altitude or in patients with functional lung impairment at sea level, the lungs and thorax can impose an important additional limitation on exercise capacity. Limitations potentially arise from: 1) increased mechanical load on respiratory muscles; 2) Impaired alveolar gas exchange by a low O2 diffusing capacity or low O2 driving pressure (high altitude) or inefficient regional matching of ventilation and blood flow; 3) Restrictions imposed on cardiovascular function by increased right ventricular afterload, exaggerated mechanical heart-lung interactions, e.g., increased stiffness of the lungs and cardiac fossa, causing impairment of diastolic filling or cardiodepressor reflexes from the lung. The relative importance of these potential sources of exercise limitation in lung disease are unclear and difficult to approach experimentally in man. There have been numerous animal models developed for examining mechanisms of exercise limitation caused by impaired cardiovascular function, but virtually none for examining mechanisms of limitation imposed by impaired lung function. By pneumonectomy in dogs, we can increase in a reproducible way the stiffness and reduce the diffusing capacity of the lungs and increase pulmonary vascular resistance. This will in turn increase work of breathing, reduce the reserve for alveolar gas exchange, increase right ventricular afterload, and may also reduce preload to the heart. Over the past 31/2 years we have developed the techniques to examine each of these potential sources of limitation to exercise in awake dogs using minimally invasive methods and limited use of chronic instrumentation. Our plan is to employ these methods to characterize the nature and importance of the potential sources of limitations in exercise capacity by loss of lung parenchyma.