EFFECT OF ACUTE HYPEROXIA ON THE BRONCHODILATOR RESPONSE TO SALBUTAMOL IN STABLE ASTHMATIC-PATIENTS

Background - Recent animal studies have suggested that changes in oxyg en tension may alter airway responses to bronchoconstrictor and bronch odilator stimuli. These effects may have relevance to the management o f acute exacerbations of asthma but have not been well studied in man. This study was designed therefore to examine the effect of acute hype roxia (Fio(2) 1.0) on the bronchodilator response to salbutamol in sta ble asthmatic patients. Methods - Twelve stable adult asthmatic patien ts (three women) were studied using a randomised double blind placebo controlled crossover design. On two study days following baseline meas urements patients breathed either air (Fio(2) 0.21) or oxygen (Fio(2) 1.0) for 10 minutes alone and then in combination with three increment al doses of nebulised salbutamol administered at 15 minute intervals. The same protocol was employed on two further study days using nebulis ed saline instead of salbutamol. Results - The mean absolute change in forced expiratory volume in one second (FEV(1)) from baseline after s albutamol was similar on the normoxic and hyperoxic study days but sig nificantly greater than the study days on which nebulised saline was a dministered. Conclusion - Acute hyperoxia does not potentiate the imme diate bronchodilator response to salbutamol in stable asthmatic patien ts.