Cardiorespiratory and metabolic stresses during repeated pursed-lips breathing in chronic obstructive pulmonary disease

Abstract

Introduction. Pursed-lip breathing (PLB) is a breathing exercise treatment for patients with chronic obstructive pulmonary disease (COPD). The purpose of this study was to investigate the dynamic changes in the cardiorespiratory and metabolic functions during and after repeated volitional PLB and spontaneous breathing (SB) at rest in COPD patients. Methods. Sixteen patients with moderate-to-severe airflow limitation participated in this crossover study in which the subjects in both the groups randomly received 10 repeated cycles of PLB and SB interventions. Cardiorespiratory and metabolic variables were collected at the baseline, throughout the 10 breathing cycles, and after a recovery period of 5 min. Results. During PLB, the tidal volume (VT) increased progressively, whereas the breathing frequency (BF) decreased gradually throughout the 10 volitional PLB cycles (p > 0.05). However, minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) remained unchanged during PLB (p > 0.05). The VT and BF peaks appeared during the 8th and 7th cycles, respectively, and then plateaued until the 10th breathing cycle. The heart rate (HR) while performing PLB slightly increased (p < 0.05) from the 3rd to the 10th cycle compared to SB. Conclusions. Despite the clinical benefits of PLB in increasing the inspired volume and slowing the rate of breathing, this manoeuvre in COPD patients should be prescribed with an awareness of the risk of cardiac stress, especially the effect on the HR, as well as the respiratory limitations with repeated PLB. Practically, this study recommends limiting repeated PLB in COPD patients to seven breathing cycles.