Determining the optimal time to assess the reversibility of airway obstruction

The optimal time to interpret bronchodilator reversibility remains controversial. This time may affect a positive diagnosis and manage asthma and chronic obstructive pulmonary disease (COPD).

We sought to document the time when maximum respiratory function is reached after inhalation of salbutamol and to define the optimal time of bronchodilator response to assess the reversibility or non reversibility of airway obstruction.

This prospective analytical study was spread over 8 months and included 58 patients with asthma or COPD with airway obstruction. Spirometry was performed before and at 5, 10, 15, 20, and 30 min after salbutamol inhalation (200 mcg) administered through pressurized metered-dose inhalers and large volume spacer.

After salbutamol inhalation, the mean individual peak bronchodilation occurred at 20 min for the forced vital capacity and at 30 min for the forced expiratory volume in 1 s. The percentage of reversible patients in our sample was guideline dependent. It increased from 53% to 67.2% when using the American Thoracic Society/European Respiratory Society definition compared to using the Global Initiative for Chronic Obstructive Lung Disease. The maximum number of reversible patients was significantly different at 20 min compared to 5 and 10 min.

Interpreting bronchodilator reversibility after 20 min was the ideal time to judge the reversibility or nonreversibility in obstructive ventilatory disorders in adults.