Proportional assist ventilation improves exercise capacity in patients with obesity.

BACKGROUND Exercise capacity is reduced in obese patients due to disadvantageous respiratory mechanics that lead to dyspnea. Proportional assist ventilation (PAV) has the potential to unload resistive and elastic burdens of the ventilatory system. OBJECTIVES The present study aimed to test if PAV can increase endurance and reduce exercise-related dyspnea in obese patients. METHODS Two symptom-limited exercise tests were performed at 75% of V.O(2max): (1) without PAV and (2) with PAV. Exercise endurance, blood gases, dyspnea and limb discomfort (Borg scale) were assessed. Responders to PAV were defined as those increasing their exercise duration by more than 20%. RESULTS Eighteen male obese patients (body mass index 35 +/- 5 kg/m(2)) were investigated. Overall, PAV increased exercise duration by 13% (p = 0.037) and improved exercise-induced dyspnea (p = 0.004). In responders (n = 10), PAV increased the exercise duration by 31% from 721 +/- 300 to 1,041 +/- 454 s (p < 0.001) and reduced dyspnea (p = 0.004) as well as limb discomfort (p = 0.016). Following stepwise multiple linear regression analysis, prolonged exercise time with PAV can only be predicted from total lung capacity (p = 0.02), considering total lung capacity, V.O(2max) and body mass index. CONCLUSIONS PAV applied during exercise led to an overall prolongation in exercise endurance and a reduction in dyspnea in obese patients. There was a broad spectrum of response to PAV, with more than 50% of patients increasing their exercise endurance by a mean of 31%. Therefore, PAV might serve as a novel treatment option to enhance exercise capacity in a subgroup of obese patients in rehabilitation programs.