Effect of Therapeutic Hyperoxia on Maximal Oxygen Consumption and Perioperative Risk Stratification in Chronic Obstructive Pulmonary Disease
Maximal consumption of oxygen $$ (\dot{V} $$ O2max) during exercise is used in patients with chronic obstructive pulmonary disease (COPD) to stratify perioperative risk. However, the impact of therapeutic hyperoxia (i.e., use of supplemental oxygen to prevent hypoxemia during exercise) on $$ \dot{V} $$ O2max and other ventilatory parameters during maximal exercise in the resting normoxic COPD population is poorly defined. A randomized, double-blind crossover study was performed in which resting normoxic subjects (n = 16) with COPD underwent two standard symptom-limited, ramped-protocol bicycle ergometry cardiopulmonary exercise tests >5 days apart with FiO2 of 0.21 (control) and ~0.28 (therapeutic hyperoxia). $$ \dot{V} $$ O2max and other ventilatory parameters were compared using a paired two-sample t-test. Therapeutic hyperoxia significantly increased $$ \dot{V} $$ O2max (12.2 ± 2.9 vs. 13.6 ± 3.8 ml/kg/min, P = 0.03), partial pressure of end-tidal carbon dioxide, and oxygen saturation and significantly decreased $$ \dot{V} $$ E– $$ \dot{V} $$ CO2 slope, but it did not affect exercise time, maximum watts achieved, maximum minute ventilation, or change in end-expiratory lung volume. Three of four subjects with $$ \dot{V} $$ O2max <10 ml/kg/min without supplemental oxygen increased $$ \dot{V} $$ O2max to ≥10 ml/kg/min on therapeutic hyperoxia and potentially changed perioperative risk category. Therapeutic hyperoxia in a resting normoxic COPD population significantly improves $$ \dot{V} $$ O2max and may change perioperative risk stratification by conventional criteria. Further studies are needed to determine if this change in stratification is appropriate.