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: We studied interrelationships between exercise endurance, ventilatory demand, operational lung volumes, and dyspnea during acute hyperoxia in ventilatory-limited patients with advanced chronic obstructive pulmonary disease (COPD). Eleven patients with COPD (FEV1.0 = 31 /- 3% predicted, mean /- SEM) and chronic respiratory failure (PaO2 52 /- 2 mm Hg, PaCO2 48 /- 2 mm Hg) breathed room air (RA) or 60% O2 during two cycle exercise tests at 50% of their maximal exercise capacity, in randomized order. Endurance time (Tlim), dyspnea intensity (Borg Scale), ventilation ([latin capital V with dot above] e), breathing pattern, dynamic inspiratory capacity (ICdyn), and gas exchange were compared. PaO2 at end-exercise was 46 /- 3 and 245 /- 10 mm Hg during RA and O2, respectively. During O2, Tlim increased 4.7 /- 1.4 min (p < 0.001); slopes of Borg, [latin capital V with dot above] e, [latin capital V with dot above] co2, and lactate over time fell (p < 0.05); slopes of Borg-[latin capital V with dot above] e, [latin capital V with dot above] e-[latin capital V with dot above] co2, [latin capital V with dot above] e-lactate were unchanged. At a standardized time near end-exercise, O2 reduced dyspnea 2.0 /- 0.5 Borg units, [latin capital V with dot above] co2 0.06 /- 0.03 L/min, [latin capital V with dot above] e 2.8 /- 1.0 L/min, and breathing frequency 4.4 /- 1.1 breaths/min (p < 0.05 each). ICdyn and inspiratory reserve volume (IRV) increased throughout exercise with O2 (p < 0.05). Increased ICdyn was explained by the combination of increased resting IRV and decreased exercise breathing frequency (r2 = 0.83, p < 0.0005). In conclusion, improved exercise endurance during hyperoxia was explained, in part, by a combination of reduced ventilatory demand, improved operational lung volumes, and dyspnea alleviation.

(C) 2001 American Thoracic Society