Proportional assist ventilation and exercise tolerance in subjects with COPD

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 = 2O1 [47]% predicted; diffusion of carbon monoxide = 36 [10]% predicted; PaO2 = 76 [8] mm Hg; and PaCO2 = 41 [4] 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 [3] cm H2O/L, flow assist = 3 [1] cm H2O/L/s); (3) continuous positive airway pressure (CPAP) (5 [2] 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.