Decline of Resting Inspiratory Capacity in COPD

医学 四分位数 肺活量测定 慢性阻塞性肺病 心脏病学 容积描记器 内科学 通风(建筑) 肺容积 哮喘 置信区间 机械工程 工程类
作者
Denis E. O’Donnell,Jordan A. Guenette,François Maltais,Katherine A. Webb
出处
期刊:Chest [Elsevier]
卷期号:141 (3): 753-762 被引量:165
标识
DOI:10.1378/chest.11-0787
摘要

Background To better understand the interrelationships among disease severity, inspiratory capacity (IC), breathing pattern, and dyspnea, we studied responses to symptom-limited cycle exercise in a large cohort with COPD. Methods Analysis was conducted on data from two previously published replicate clinical trials in 427 hyperinflated patients with COPD. Patients were divided into disease severity quartiles based on FEV1 % predicted. Spirometry, plethysmographic lung volumes, and physiologic and perceptual responses to constant work rate (CWR) cycle exercise at 75% of the peak incremental work rate were compared. Results Age, body size, and COPD duration were similar across quartiles. As the FEV1 quartile worsened (mean, 62%, 49%, 39%, and 27% predicted), functional residual capacity increased (144%, 151%, 164%, and 185% predicted), IC decreased (86%, 81%, 69%, and 60% predicted), and peak incremental cycle work rate decreased (66%, 55%, 50%, and 44% predicted); CWR endurance time was 9.7, 9.3, 8.2, and 7.3 min, respectively. During CWR exercise, as FEV1 quartile worsened, peak minute ventilation (e) and tidal volume (Vt) decreased, whereas an inflection or plateau of the Vt response occurred at a progressively lower e (P < .0005), similar percentage of peak e (82%–86%), and similar Vt/IC ratio (73%–77%). Dyspnea intensity at this inflection point was also similar across quartiles (3.1-3.7 Borg units) but accelerated steeply to intolerable levels thereafter. Conclusion Progressive reduction of the resting IC with increasing disease severity was associated with the appearance of critical constraints on Vt expansion and a sharp increase in dyspnea to intolerable levels at a progressively lower ventilation during exercise. To better understand the interrelationships among disease severity, inspiratory capacity (IC), breathing pattern, and dyspnea, we studied responses to symptom-limited cycle exercise in a large cohort with COPD. Analysis was conducted on data from two previously published replicate clinical trials in 427 hyperinflated patients with COPD. Patients were divided into disease severity quartiles based on FEV1 % predicted. Spirometry, plethysmographic lung volumes, and physiologic and perceptual responses to constant work rate (CWR) cycle exercise at 75% of the peak incremental work rate were compared. Age, body size, and COPD duration were similar across quartiles. As the FEV1 quartile worsened (mean, 62%, 49%, 39%, and 27% predicted), functional residual capacity increased (144%, 151%, 164%, and 185% predicted), IC decreased (86%, 81%, 69%, and 60% predicted), and peak incremental cycle work rate decreased (66%, 55%, 50%, and 44% predicted); CWR endurance time was 9.7, 9.3, 8.2, and 7.3 min, respectively. During CWR exercise, as FEV1 quartile worsened, peak minute ventilation (e) and tidal volume (Vt) decreased, whereas an inflection or plateau of the Vt response occurred at a progressively lower e (P < .0005), similar percentage of peak e (82%–86%), and similar Vt/IC ratio (73%–77%). Dyspnea intensity at this inflection point was also similar across quartiles (3.1-3.7 Borg units) but accelerated steeply to intolerable levels thereafter. Progressive reduction of the resting IC with increasing disease severity was associated with the appearance of critical constraints on Vt expansion and a sharp increase in dyspnea to intolerable levels at a progressively lower ventilation during exercise.
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