STUDY OBJECTIVE: This study determined whether proportional assist ventilation (PAV) applied during constant power submaximal exercise could enable individuals with severe but stable COPD to increase their exercise tolerance. DESIGN: Prospective controlled study having a randomized order of intervention. SETTING: Pulmonary function exercise laboratory. PARTICIPANTS: Ten subjects with severe stable COPD (mean (SD): age 59 (6) years; FEV1 29 (7) % predicted; FEV1/FVC 33% (7); thoracic gas volume 201 (47) % predicted; diffusion of carbon monoxide 36 (10) % predicted; PaO2 76 (8) mmHg; and PaCO2 41 (4) mmHg). INTERVENTION: Each subject completed five sessions of cycling at 60 to 70% of their maximum power. The sessions differed only in the type of inspiratory assist: (1) baseline (airway pressure (Paw) 0 cmH2O); (2) proportional assist ventilation (PAV) (volume assist 6 (3) cmH2O/L, flow assist 3 (1) cmH2O/L/s); (3) continuous positive airway pressure (CPAP) (5 (2) cmH2O); (4) PAV+CPAP; and (5) sham (Paw 0 cmH2O). MEASUREMENTS AND RESULTS: Dyspnea was measured using a modified Borg scale. Subjects reached the same level of dyspnea during all sessions but only PAV+CPAP significantly (p < 0.05) increased exercise tolerance (12.88 (8.74) min) versus the sham session (6.60 (3.12) min). Exercise time during the PAV and CPAP sessions was 7.10 (2.83) and 8.26 (5.54) min, respectively. Minute ventilation increased during exercise but only during PAV+CPAP was the end exercise minute ventilation greater than the unassisted baseline end exercise minute ventilation (36.2 (6.7) versus 26.6 (6.4) L/min, respectively; p < 0.05). CONCLUSIONS: In this study, PAV+CPAP provided ventilatory assistance during cycle exercise sufficient to increase the endurance time. It is now appropriate to evaluate whether PAV+CPAP will facilitate exercise training.

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