Acute effects of Expiratory Positive Airway Pressure (EPAP) on different levels in ventilation and electrical activity of sternocleidomastoid and parasternal muscles in Chronic Obstructive Pulmonary Disease (COPD) patients: a randomized controlled trial

OBJECTIVE: To investigate the acute effects of EPAP on the activity of sternocleidomastoid (SCM), parasternal muscles and ventilatory parameters in COPD patients. METHOD: Twenty-four patients with COPD were studied using surface electromyography (sEMG) and a ventilometer. Patients were randomly assigned to EPAP 10 cmH(2)O-EPAP(10) or 15 cmH(2)O-EPAP(15) for 20 minutes. RESULTS: The parasternal muscle sEMG activity increased during EPAP(10) and EPAP(15); however, a greater and significant increase was observed with EPAP(10) (mean between-group difference: 12.5% RMS, 95% CI: 9.5 to 15.4, p<0.001). In relation to the baseline, at 10 and 20 minutes and upon recovery, respectively parasternal activity increased by 23.9%, 28.9% and 19.1% during EPAP(10) and by 10.7% at 10 and 20 minutes and upon recovery, respectively, 11.4% and 6.9% during EPAP(15) at 10 and 20 minutes and upon recovery, respectively. The sEMG activity of SCM muscle showed an opposite pattern, increasing with EPAP(15) and decreasing with EPAP(10) (mean between-group difference: 15.5% RMS, 95% CI: 12.6 to 18.4, p<0.001). SCM muscle activity during EPAP(15), increased by 4.8% and 6.1% at 10 and 20 minutes and decreased by -4.0% upon recovery compared to decreases of –5.6%, –20.6% and –21.3% during EPAP(10) at 10, 20 minutes, and recovery. Ventilation at both EPAP intensities promoted significant reductions in respiratory rate (RR) and dyspnea, more pronounced in EPAP(15): RR (mean between-group difference: –3,8bpm, 95%CI: –7,5 to –0,2, p=0,015) and dyspnea (mean between-group difference: –1.01, 95%CI: –1.4 to –0.53, p=0.028) . CONCLUSION: In COPD patients, the use of EPAP(10) was more effective in reducing accessory inspiratory activity and increasing parasternal activity, which was accompanied by an improvement in ventilation and a reduction in dyspnea.