Effects of imposed pursed-lips breathing on respiratory mechanics and dyspnea at rest and during exercise in COPD

Study objectives: To investigate the effect of volitional pursed-lips breathing (PLB) on breathing pattern, respiratory mechanics, operational lung volumes, and dyspnea in patients with COPD. Subjects: Eight COPD patients (6 male and 2 female) with a mean (+/- SD) age of 58 +/- 11 years and a mean FEV1 of 1.34 +/- 0.44 L (50 +/- 21% predicted). Methods: Wearing a tight-fitting transparent facemask, patients breathed for 8 min each, with and without PLB at rest and during constant-work-rate bicycle exercise (60% of maximum). Results: PLB promoted a slower and deeper breathing pattern both at rest and during exercise. Whereas patients had no dyspnea with or without PLB at rest, during exercise dyspnea was variably affected by PLB across patients. Changes in the individual dyspnea scores with PLB during exercise were significantly correlated with changes in the end-expiratory lung volume (EELV) values estimated from inspiratory capacity maneuvers (as a percentage of total lung capacity; r(2) = 0.82, p = 0.002) and with changes in the mean inspiratory ratio of pleural pressure to the maximal static inspiratory pressure-generating capacity (Pcapi) [r(2) = 0.84; p = 0.001], measured using an esophageal balloon, where Pcapi was determined over the range of inspiratory lung volumes and adjusted for flow. Conclusion: PLB can have a variable effect on dyspnea when performed volitionally during exercise by patients with COPD. The effect of PLB on dyspnea is related to the combined change that it promotes in the tidal volume and EELV and their impact on the available capacity of the respiratory muscles to meet the demands placed on them in terms of pressure generation.