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

Abstract

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. To evaluate the influence diaphragmatic mobility has on exercise tolerance and dyspnea in patients with COPD. 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. 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=33.99 mm) and G2 (>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). Diaphragmatic mobility influences dyspnea and exercise tolerance in patients with COPD.