LAUSR

BACKGROUND We previously showed that use of portable non-invasive ventilation (pNIV) during recovery periods within intermittent exercise improved breathlessness and exercise tolerance in COPD patients compared to pursed-lip breathing (PLB). However, in a minority of patients recovery from dynamic hyperinflation (DH) was better with PLB, based on inspiratory capacity. We further explored this using Optoelectronic Plethysmography to assess total and compartmental thoracoabdominal volumes. METHODS Fourteen COPD patients (mean±SD) (FEV1: 55±22% predicted) underwent, in a balanced order sequence, two intermittent exercise protocols on the cycle ergometer consisting of five repeated 2-min exercise bouts at 80% peak capacity, separated by 2-min recovery periods, with application of pNIV or PLB in the first minute of recovery. RESULTS Our findings identified 7 patients showing clinically meaningful recovery in DH with pNIV (DH responders) while 7 showed similar or better recovery in DH with PLB. When pNIV was applied, DH responders compared to DH non-responders exhibited greater tidal volume (by 0.8±0.3 L, p=0.015), inspiratory flow rate (by 0.6±0.5 L/sec, p=0.049), prolonged expiratory time (by 0.6±0.5 sec, p=0.006) and duty cycle (by 0.7±0.6 sec, p=0.007). DH responders showed a clinically meaningful reduction in end-expiratory thoracoabdominal DH (by 265±633 ml) predominantly driven by reduction in the abdominal compartment (by 210±494 ml); this effectively offset end-inspiratory rib-cage DH. Compared to DH non-responders, DH responders had significantly greater BMI by 8.4±3.2, p=0.022 and tended towards less severe resting hyperinflation by 0.3±0.3 L. CONCLUSION COPD patients who mitigate end-expiratory rib-cage DH by expiratory abdominal muscle recruitment benefit from pNIV application.