Jones Joshua H, Zelt Joel T, Hirai Daniel M, Diniz Camilla V, Zaza Aida, O'Donnell Denis E, Neder J Alberto
a Laboratory of Clinical Exercise Physiology (LACEP), Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen's University , Kingston , ON , Canada.
b Respiratory Investigation Unit (RIU), Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen's University , Kingston , ON , Canada.
COPD. 2017 Apr;14(2):210-218. doi: 10.1080/15412555.2016.1253670. Epub 2016 Dec 20.
There is growing evidence that emphysema on thoracic computed tomography (CT) is associated with poor exercise tolerance in COPD patients with only mild-to-moderate airflow obstruction. We hypothesized that an excessive ventilatory response to exercise (ventilatory inefficiency) would underlie these abnormalities. In a prospective study, 19 patients (FEV = 82 ± 13%, 12 Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 1) and 26 controls underwent an incremental exercise test. Ventilatory inefficiency was assessed by the ventilation ([Formula: see text]E)/CO output ([Formula: see text]CO) nadir. Pulmonary blood flow (PBF) in a submaximal test was calculated by inert gas rebreathing. Emphysema was quantified as % of attenuation areas below 950 HU. Patients typically presented with centrilobular emphysema (76.8 ± 10.1% of total emphysema) in the upper lobes (upper/total lung ratio = 0.82 ± 0.04). They had lower peak oxygen uptake ([Formula: see text]O), higher [Formula: see text]E/[Formula: see text]CO nadir, and greater dyspnea scores than controls (p < 0.05). Lower peak [Formula: see text]O and worse dyspnea were found in patients with higher [Formula: see text]E/[Formula: see text]CO nadirs (≥30). Patients had blunted increases in PBF from rest to iso-[Formula: see text]O exercise (p < 0.05). Higher [Formula: see text]E/[Formula: see text]CO nadir in COPD was associated with emphysema severity (r = 0.63) which, in turn, was related to reduced lung diffusing capacity (r = -0.72) and blunted changes in PBF from rest to exercise (r = -0.69) (p < 0.01). Ventilation "wasted" in emphysematous areas is associated with impaired exercise ventilatory efficiency in mild-to-moderate COPD. Exercise ventilatory inefficiency links structure (emphysema) and function (DCO) to a key clinical outcome (poor exercise tolerance) in COPD patients with only modest spirometric abnormalities.
越来越多的证据表明，对于仅存在轻度至中度气流受限的慢性阻塞性肺疾病（COPD）患者，胸部计算机断层扫描（CT）显示的肺气肿与运动耐力差有关。我们推测，运动时过度的通气反应（通气效率低下）是这些异常的潜在原因。在一项前瞻性研究中，19例患者（第一秒用力呼气容积[FEV₁]=82±13%，12例慢性阻塞性肺疾病全球倡议组织（GOLD）1期）和26名对照者接受了递增运动试验。通气效率低下通过通气量（[公式：见原文]E）/二氧化碳排出量（[公式：见原文]CO）最低点进行评估。次极量试验中的肺血流量（PBF）通过惰性气体再呼吸法计算。肺气肿以低于950HU的衰减区域百分比进行量化。患者的肺气肿通常以上叶的小叶中心型肺气肿为主（占总肺气肿的76.8±10.1%）（上叶/全肺比值=0.82±0.04）。与对照组相比，他们的峰值摄氧量（[公式：见原文]VO₂）更低，[公式：见原文]E/[公式：见原文]CO最低点更高，且呼吸困难评分更高（p<０.０５）。在[公式：见原文]E/[公式：见原文]CO最低点较高（≥30）的患者中，发现峰值[公式：见原文]VO₂更低且呼吸困难更严重。患者从静息状态到等[公式：见原文]VO₂运动时PBF的增加不明显（p<０.０５）。COPD患者中较高的[公式：见原文]E/[公式：见原文]_CO最低点与肺气肿严重程度相关（r=0.63），而肺气肿严重程度又与肺弥散能力降低（r=-0.72）以及从静息状态到运动时PBF的变化不明显（r=-0.69）相关（p<０.０１）。肺气肿区域中“浪费”的通气与轻度至中度COPD患者运动通气效率受损有关。运动通气效率低下将结构（肺气肿）和功能（DCO）与仅存在适度肺量计异常的COPD患者的关键临床结局（运动耐力差）联系起来。
