• T E Dolmage and R S Goldstein.
• Department of Medicine, University of Toronto, West Park Hospital, Ontario, Canada.
• Chest. 1997 Apr 1; 111 (4): 948-54.

Study ObjectiveThis 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.DesignProspective controlled study having a randomized order of intervention.SettingPulmonary function exercise laboratory.ParticipantsTen 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] mm Hg; and PaCO2=41 [4] mm Hg).InterventionEach 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 ResultsDyspnea 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).ConclusionsIn 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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