Influence of diaphragmatic mobility on exercise tolerance and dyspnea in patients with COPD.

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) present increased airway resistance, air trapping, pulmonary hyperinflation, and diaphragm muscle alterations, all of which affect pulmonary mechanics. PURPOSE: To evaluate the influence diaphragmatic mobility has on exercise tolerance and dyspnea in patients with COPD. MATERIALS AND METHODS: Fifty-four COPD patients with lung hyperinflation were evaluated to assess pulmonary function, diaphragm mobility, exercise tolerance, and dyspnea (score). Twenty healthy (age- and body mass index-matched) subjects were evaluated as controls. RESULTS: The COPD patients presented lower diaphragmatic mobility than did the controls (36.27+/-10.96 mm vs. 46.33+/-9.46 mm). Diaphragmatic mobility presented a linear correlation with distance covered on the 6-min walk test (6MWT) (r=0.38; p=0.005) and a negative correlation with dyspnea (r=-0.36; p=0.007). Patients were then divided into two subgroups based on the degree of diaphragmatic mobility: G1 (or=34 mm). Those in G1 presented poorer 6MWT performance and greater dyspnea upon exertion than did those in G2 (distance covered on the 6MWT: 454.76+/-100.67 m vs. 521.63+/-70.82 m; dyspnea score: 5.22+/-3.06 vs. 3.48+/-2.77). The G1 patients also presented greater residual volume (in liters) and lower maximal voluntary ventilation (in % of predicted values) than did the G2 patients (266.20+/-55.30 vs. 209.74+/-48.49 and 39.00+/-14.94 vs. 58.11+/-20.96). CONCLUSION: Diaphragmatic mobility influences dyspnea and exercise tolerance in patients with COPD.