Ventilatory constraints and dyspnea during exercise in chronic obstructive pulmonary disease.
Dyspnea (respiratory difficulty) and activity limitation are the primary symptoms of chronic obstructive pulmonary disease (COPD) and progress relentlessly as the disease advances, contributing to reduced quality of life. In COPD, the mechanisms of dyspnea are multifactorial, but abnormal dynamic ventilatory mechanics are believed to play a central role. In flow-limited patients with COPD, dynamic lung hyperinflation (DH) occurs during exercise and has serious sensory and mechanical consequences. In several studies, indices of DH strongly correlate with ratings of dyspnea intensity during exercise, and strategies that reduce resting hyperinflation (either pharmacological or surgical) consistently result in reduced exertional dyspnea. The mechanisms by which DH gives rise to exertional dyspnea and exercise intolerance are complex, but recent mechanistic studies suggest that DH-induced inspiratory muscle loading, restriction of tidal volume expansion during exercise, and consequent neuromechanical uncoupling of the respiratory system are key components. This review examines the specific derangements of ventilatory mechanics that occur in COPD during exercise and attempts to provide a mechanistic rationale for the attendant respiratory discomfort and activity limitation.
Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen's University, 102 Stuart St., Kingston, ON K7L 2V6.
Pierantonio
P
Laveneziana
Chris M
CM
Parker
Denis E
DE
O'Donnell
D000339:Affect / Q000502:physiology; D000368:Aged; D001696:Biomechanical Phenomena; D004417:Dyspnea / Q000503:physiopathology* / Q000523:psychology; D015444:Exercise / Q000502:physiology* / Q000523:psychology; D005081:Exercise Therapy; D017079:Exercise Tolerance / Q000502:physiology; D006801:Humans; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000523:psychology; D015656:Respiratory Mechanics / Q000502:physiology*; D012132:Respiratory Muscles / Q000502:physiology