Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Canada; Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Canada.
Department of Critical Care and Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Canada.
Respir Med. 2018 Dec;145:57-65. doi: 10.1016/j.rmed.2018.10.015. Epub 2018 Oct 19.
Previous work suggests that mild chronic obstructive pulmonary disease (COPD) patients have greater lung dysfunction than previously appreciated from spirometry alone. There is evidence of pulmonary microvascular dysfunction in mild COPD, which may reduce diffusing capacity (DLCO) and increase ventilatory inefficiency during exercise. The purpose of this study was to determine if DLCO, pulmonary capillary blood volume (Vc), and membrane diffusing capacity (Dm) are diminished during exercise in mild COPD, and whether this is related to ventilatory inefficiency and dyspnea.
Seventeen mild COPD patients (FEV/FVC: 64 ± 4%, FEV = 94 ± 11%) and 17 age- and sex-matched controls were recruited. Ten moderate COPD patients were also tested for comparison (FEV = 66 ± 7%). DLCO, Vc, and Dm were determined using the multiple-fraction of inspired oxygen (FO) DLCO method at baseline and during steady-state cycle exercise at 40W, 50%, and 80% of V˙O. Using expired gas data, ventilatory inefficiency was assessed by V˙/V˙CO.
Compared to controls, mild COPD had lower DLCO at baseline and during exercise secondary to diminished Vc (P < 0.05). No difference in Dm was observed between controls and mild COPD at rest or during exercise. Patients with high V˙/V˙CO (i.e. ≥34) had lower Vc and greater dyspnea ratings compared to control at 40W. Moderate COPD patients were unable to increase Vc with increasing exercise intensity, suggesting further pulmonary vascular impairment with increased obstruction severity.
Despite relatively minor airflow obstruction, mild COPD patients exhibit a diminished DLCO and capillary blood volume response to exercise, which appears to contribute to ventilatory inefficiency and greater dyspnea.
先前的研究表明，轻度慢性阻塞性肺疾病（COPD）患者的肺功能障碍比仅通过肺功能检查评估的更为严重。在轻度 COPD 中已经有肺微血管功能障碍的证据，这可能会降低扩散能力（DLCO）并增加运动期间的通气效率低下。本研究的目的是确定在轻度 COPD 中，DLCO、肺毛细血管血容量（Vc）和膜扩散能力（Dm）是否在运动期间降低，以及这是否与通气效率低下和呼吸困难有关。
招募了 17 名轻度 COPD 患者（FEV/FVC：64±4%，FEV=94±11%）和 17 名年龄和性别匹配的对照者。还对 10 名中度 COPD 患者进行了测试以作比较（FEV=66±7%）。使用多分数吸入氧气（FO）DLCO 方法，在基线和稳定状态下的 40W、50%和 80%V˙O 下的自行车运动时，分别测定 DLCO、Vc 和 Dm。使用呼出气体数据，通过 V˙/V˙CO 评估通气效率低下。
与对照组相比，轻度 COPD 患者在静息和运动时的 DLCO 均较低，这是由于 Vc 降低所致（P<0.05）。在静息和运动时，对照组和轻度 COPD 患者的 Dm 没有差异。在 40W 时，具有高 V˙/V˙CO（即≥34）的患者的 Vc 较低，呼吸困难评分也高于对照组。中度 COPD 患者无法随着运动强度的增加而增加 Vc，这表明随着阻塞严重程度的增加，肺血管进一步受损。
尽管存在相对较小的气流阻塞，但轻度 COPD 患者在运动时的 DLCO 和毛细血管血容量反应明显降低，这似乎导致通气效率低下和呼吸困难增加。
