Fixed airflow obstruction (FAO)
Fixed airflow obstruction was defined as the ratio of the forced
expiratory volume in the first second to the forced vital capacity
(FEV1/FVC) being persistently below the lower limit of
normal range (LLN), according to reference equations, even after the use
of a postbronchodilator (BD) (3). For adolescents with
FEV1/FVC ratios lower than the LLN persistently on the
two consecutive visits, oral corticosteroids (OC) were prescribed for
seven consecutive days (the OC dose ranged from 1 to 2 milligrams (mg)
per kg of body weight, up to a maximum dose of 40 mg/day) (1). After
seven days of OC treatment, the adolescents returned to the hospital and
underwent a new spirometry test. The presence of FAO was noted if the
FEV1/FVC ratio remained lower than the LLN (3).