Abstract
BACKGROUND: This study assessed the clinical effects of a ventilatory assist (VA) device in addition to supplemental O(2) (VA+O(2)) on exercise endurance in subjects with severe to very severe COPD managed with long-term oxygen therapy (LTOT). METHODS: This was a crossover clinical feasibility study of the effects of VA+O(2) in subjects with severe to very severe COPD managed with LTOT (N = 15). At visit 1, physiologic measures were obtained, and subjects were tested on the cycle ergometer with VA. Peak work rate and flow for continuous supplemental O(2)/VA+O(2) were established. At visit 2, subjects exercised at a constant work rate of 80% peak work rate to maximum endurance after allocation to VA+O(2) or O(2). Cardiorespiratory variables, work rate, and dyspnea were included to define potential clinical benefits of VA+O(2). Data were analyzed using a linear mixed model. RESULTS: Fifteen subjects with COPD (mean ± SD, age 67.9 ± 9.0 y, FEV(1) 0.89 ± 0.35 observed) completed the study. Exercise duration in minutes was significantly longer with VA+O(2) versus O(2) (least squares mean [standard error], 12.0 [2.0] vs 6.2 [2.0], P = .01). VA+O(2) versus O(2) was also associated with significantly greater isotime improvements in Borg dyspnea scores (3.6 [0.5] vs 5.7 [0.5], P < .001), S(pO(2)) (96.9 [0.9] vs 91.4 [0.9], P < .001), leg fatigue scores (3.8 [0.6] vs 5.2 [0.6], P = .008), and breathing frequency (22.8 [0.9] vs 25.8 [0.9] breaths/min, P = .01). There were no differences in heart rate. CONCLUSIONS: In symptomatic subjects with severe to very severe COPD, VA+O(2) significantly increased exercise time and improved dyspnea, S(pO(2)) , breathing frequency, and leg fatigue versus O(2) alone.