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  years; FEV1=29 % predicted; FEV1/FVC=33 %; thoracic gas volume=201 % predicted; diffusion of carbon monoxide=36 % predicted; PaO2=76  mm Hg; and PaCO2=41  mm Hg).
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 cm H2O); (2) proportional assist ventilation (PAV) (volume assist=6  cm H2O/L, flow assist=3  cm H2O/L/s); (3) continuous positive airway pressure (CPAP) (5  cm H2O); (4) PAV+CPAP; and (5) sham (Paw=0 cm H2O).
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) vs 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] vs 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.