Background: Although pursed-lip breathing (PLB) has been advocated to reduce respiratory rate and improve oxygen saturation in patients with chronic obstructive pulmonary disease (COPD) at rest, the evidence of its effects on dynamic hyperinflation (DH) and exercise tolerance is scarce.
Aim: To evaluate the effect of PLB on exercise tolerance, breathing pattern, dynamic hyperinflation and arterial oxygenation in COPD patients during high-intensity exercise.
Design: Randomized crossover study.
Setting: Laboratory of Respiration Physiology, Federal University of Rio de Janeiro.
Population: Forty stable COPD patients aged 40-75 years and with FEV1<60%.
Methods: In a randomized order, all patients performed PLB and control breathing (CB) during constant work-rate exercise in an electrically-braked cycloergometer. Dynamic hyperinflation, oxygen saturation and breathing pattern were recorded at rest, in isotime and in peak exercise.
Results: The nine patients who increased their endurance time by more than 25% during PLB (6.42 ± 2.36 vs. 10.51 ± 3.83 min; P < 0.05) were considered as the Improver sub-group. Compared to the Non-improver subgroup, these patients presented a lower expiratory peak flow - EPF (40.2 ± 8.6 vs. 53.3 ± 17.8 % predicted, P<0.05). The ROC Curve analysis of the EPF as a percentage of the predicted values (%pred) was performed to identify cut-off values that had greater sensitivity and specificity in differentiating between IMPROVER and NON-IMPROVER. We observed 61% sensitivity and 89% specificity with a 47.7% pred EPF. At isotime, PLB yielded higher inspiratory capacity (IC) and oxygen saturation (1.19 ± 0.33 to 1.35 ± 0.39 L; P < 0.05 and 93.1 ± 4.6 to 94.0 ± 4.1%; P<0.05), and lower respiratory rate than CB only in Improver. Non-improver patients showed thoracoabdominal asynchrony during PLB in isotime. At peak exercise, PLB improved the arterial oxygenation in Improver, but there were no changes in the breathing pattern in the analyzed subgroups.
Conclusion: In COPD patients with low PEF, pursed-lip breathing reduces dynamic hyperinflation and improves exercise tolerance, breathing pattern and arterial oxygenation at submaximal intensity exercise.
Clinical rehabilitation impact: This study points to a possible application of PLB in a selected group of COPD patients aiming at improving the exercise tolerance. PEF measurements can help to indicate PLB for COPD patients.