Dyspnea, inspiratory and expiratory muscles in mild and severe COPD compared to healthy individuals

Rationale: Dyspnea and augmented ventilatory muscle constrain are important determinants for exercise cessation in mainly severe COPD. However, these mechanisms were not fully evaluated in mild patients (FEV 1 > 50% pred). Objectives: To evaluate the ventilatory work, the recruitment of inspiratory and expiratory muscles and dyspnea, at rest and during maximum exercise test, in mild and severe COPD compared to healthy controls. Methods: Cross-sectional study involving 12 mild (FEV 1 > 50%pred) and 12 severe (FEV 1 Results: Static muscle strength was preserved in most of COPD patients. Dyspnea was the main reason for interrupting the exercise in 70% of patients and dynamic hyperinflation happened in 87.5% of them. COPD patients, mild and severe, had greater respiratory work mainly of resisitive and expiratory components. With the increase in ventilatory demand, the diaphragmatic activity (P di ) and the recruitment of inspiratory accessory and expiratory muscles during exercise was earlier and more progressive than controls (p Conclusions: Although maximal ventilatory strengths at rest were preserved in COPDs, during exercise even mild patients have already a higher dyspnea which is secondary to augmented inspiratory muscle recruitment.