The association of forced expiratory volume in one second and forced expiratory flow at 50% of the vital capacity, peak expiratory flow parameters, and blood eosinophil counts in exercise-induced bronchospasm in children with mild asthma

BACKGROUND: Exercise-induced bronchoconstriction (EIB), which describes acute airway narrowing that occurs as a result of exercise, is associated with eosinophilic airway inflammation, bronchial hyperresponsiveness. The forced expiratory volume in one second (FEV(1)) is the most commonly used spirometric test in the diagnosis of EIB in exercise challenge in asthma. Other parameters such as forced expiratory flow at 50% of the vital capacity (FEF(50%)) and peak expiratory flow (PEF) are used less often in the diagnosis of EIB. OBJECTIVE: The purpose of this study is to evaluate the association of FEV(1) and FEF(50%), PEF parameters, blood eosinophil counts in EIB in children with mild asthma. METHODS: Sixty-seven children (male: 39, female: 28) with mild asthma were included in this study. Pulmonary functions were assessed before and at 1, 5, 10, 15, and 20 minutes after exercise. The values of spirometric FEV(1), FEF(50%), PEF, and blood eosinophil counts were evaluated in EIB in children with mild asthma. RESULTS: There was a positive correlation between FEV(1) with FEF(50%) and PEF values (p<0.05; FEF(50%), r=0.68; PEF, r=0.65). Also, a positive correlation was found between blood eosinophil counts and the values of spirometric FEV(1), FEF(50%), and PEF (p<0.05; FEV(1), r=0.54; FEF(50%), r=0.42; PEF, r=0.26). In addition to these correlations, in the exercise negative group for FEV(1), the FEF(50%) and PEF values decreased more than the cutoff values in 3, and 2 patients, respectively. CONCLUSION: According to the presented study, eosinophil may play a major role in the severity of EIB in mild asthma. FEF(50%) and PEF values can decrease in response to exercise without changes in FEV(1) in mild asthmatic patients.