Does the different amount of short-acting bronchodilator drugs have different effects on small airway response in bronchodilator test?

Purpose: It is recommended to use 200 (2 puffs) or 400 (4 puffs) μg of salbutamol in the bronchodilator response (BDR) test. We aimed to compare the difference between these 2 doses with regard to small airway dysfunction.Methods: One hundred sixteen subjects who visited the hospital for diagnosis or follow-up of asthma were consecutively enrolled between June 1 and November 31, 2013. The subjects were randomly assigned to the BDR test at the 2 doses (200 or 400 μg of salbutamol), with physicians blinded to the group each subject was assigned to and undertook the BDR test using the spirometry and impulse oscillometry system (IOS).Results: A total of 116 subjects participated in this study; the mean age was 7.8±3.6 years. The number of participants who were assigned to 2 and 4 puffs groups was 59 and 57, respectively. The mean age was older in the 4 puffs group than in the 2 puffs group (P=0.008). There were no significant difference in spirometric and oscillometric parameters between the 2 and 4 puffs groups. However, in subgroup analysis of asthmatic patients on maintenance therapy (n=21), there was a significant difference in relative changes in Rrs5 between the 2 and 4 puffs groups (16.4%±9.6% vs. 28.7%±8.8%, P=0.035). The forced expiratory volume of 1 second showed a significant correlation with resistance in the 2 puffs group and with reactance in the 4 puffs group.Conclusion: There was a significant relationship between the amounts of bronchodilators administered and the small airway dysfunction in children with asthma on maintenance therapy. Further research is warranted to delineate changes in spirometric and IOS measures in accordance with the different amounts of bronchodilators administered. (Allergy Asthma Respir Dis 2016:4:284-289)