Title: Effect of inspiratory pressure support on exercise performance in patients with chronic obstructive pulmonary disease. Purpose: This study examined the effects of a non-invasive ventilator on submaximal and maximal exercise performance in patients with chronic obstructive pulmonary disease (COPD). Methods: Fourteen men (66.0 ± 7.4yr) and six women (59.0 ± 7.4yr) with a diagnosis of COPD, a forced expiratory volume! (FEVi) <40%, and the ability to tolerate 12 cmH20 of pressure on a non- invasive ventilator performed two maximal exercise tests on a cycle ergometer, with and without ventilatory assistance prior to exercise. Blood samples, respiratory metabolic measures, heart rate and rating of perceived exertion (RPE) were obtained throughout each exercise test. Results: Peak work rate (W), total exercise time, and respiratory rate were higher (p<0.05) when exercise was preceded by ventilatory support compared to no support. There was no difference in peak oxygen uptake (V02), carbon dioxide (VC02,), heart rate (HR), minute ventilation (VE), tidal volume (VT), blood lactate or RPE between the two experimental conditions. A total of 12 subjects completed at least 5 stages of the exercise protocol, and their physiological response during exercise with NIV and without NIV were compared. RPE was significantly lower during the first 3 min in the NIV condition than the no NIV condition. Circulating levels of blood lactate were lower (p<0.01) during stage 3 in the NIV than the than no NIV condition. There was no difference in RR, VT, HR, %HR, VE, V 0 2and %V02 between the two experimental conditions during sub maximal exercise. Conclusions: Application of non-invasive ventilatory support prior to exercise improves maximal exercise performance, but has no effect on cardio-metabolic response during submaximal exercise in patients with COPD.