Impulse oscillometry in children and adolescents with persistent asthma and its correlation with spirometry

Introduction: Asthma is one of the most common chronic diseases of childhood. Spirometry is the traditional test for assessing lung function, while impulse oscillometrics is an alternative resource that measures the impedance of the respiratory system. Objective: To evaluate the pulmonary function of children and adolescents with asthma by impulse oscillometry and correlate the findings with those obtained by spirometry. Methods: A cross-sectional study in which the pulmonary function of asthmatic children and adolescents aged between 6 and 18 years was evaluated, categorized by the level of disease control according to the Asthma Control Test (ACT) or Children Asthma Control Test (C-ACT) into controlled (ACT/C-ACT>19; n = 70) and uncontrolled (ACT/C-ACT ≤ 19; n = 60). Results: A total of 130 asthmatic children and adolescents were evaluated (51% were males). There were no significant differences in the parameter values of both tests when patients were divided by the level of asthma control. Altered impulse oscillometry and spirometry were performed in 20 and 25% of the cases, respectively. Changes in impulse oscillometry were more frequent in patients with controlled asthma. R5 (%), X5 (%), and Fres showed moderate correlation with the main spirometric parameters, being stronger between X5 (%) and FEV1/FVC (%) (r: -0,58; P < 0,05) in patients with controlled asthma. Bronchodilator response was observed in a similar number of patients in both exams, but with reasonable agreement. Conclusions: Impulse oscillometry values showed a weak or moderate correlation with spirometry values.