Treatment of airway inflammation improves exercise pulmonary gas exchange and performance in asthmatic subjects

Background: Asthma is an inflammatory disease of the airways that can lead to impaired arterial blood oxygenation during exercise. Objective: We asked whether treatment of airway inflammation in asthmatic subjects would improve arterial blood gases during whole-body exercise. Methods: By using a double-blind parallel-group design, 19 asthmatic subjects completed treadmill exercise to exhaustion on 2 occasions: (1) before and (2) after 6 weeks' treatment with an inhaled corticosteroid (ICS; n = 9) or placebo (n = 10). Results: The ICS group had improved resting pulmonary function, decreased exercise-induced bronchospasm, and decreased postexercise sputum histamine during the posttreatment study compared with that during the pretreatment study. In the ICS group exercise Pao₂ was significantly increased after treatment (84.8 to 93.8 mm Hg). Increased alveolar ventilation (arterial Pco₂ decreased from 36.9 to 34.1 mm Hg) accounted for 37% of the increased Pao₂ and improved gas exchange efficiency (alveolar-to-arterial Po₂ difference decreased from 22.5 to 16.3 mm Hg) accounted for the remaining 63% of the increased Pao₂ after treatment. In the ICS group exercise time to exhaustion was increased from 9.9 minutes during the pretreatment study to 14.8 minutes during the posttreatment study. Conclusion: Treatment of airway inflammation in asthmatic subjects can improve arterial blood oxygenation during exercise by (1) improving airway function, thereby allowing increased alveolar ventilation during exercise, and (2) improving the efficiency of alveolar-to-arterial blood O₂ exchange. Clinical implications: In asthmatic patients ICSs not only attenuate exercise-induced bronchospasm but also improve arterial blood oxygenation during exercise.