Preschool impulse oscillometry predicts active asthma and impaired lung function at school age.

BACKGROUND:Asthmatic symptoms often start during early childhood. Impulse oscillometry (IOS) is feasible in preschool children who may be unable to reliably perform spirometry measurements. OBJECTIVE:We sought to evaluate the use of IOS in a multicenter, multiethnic high-risk asthma cohort titled the Vitamin D Antenatal Asthma Reduction Trial. METHODS:The trial recruited pregnant women whose children were followed from birth to age 8 years. Lung function was assessed with IOS at ages 4, 5, and 6 years and spirometry at ages 5, 6, 7, and 8 years. Asthma status, respiratory symptoms, and medication use were assessed with repeated questionnaires from birth to age 8 years. RESULTS:In total, 220 children were included in this secondary analysis. Recent respiratory symptoms and short-acting β2-agonist use were associated with increased respiratory resistance at 5 Hz at age 4 years (β = 2.6; 95% CI, 1.0 to 4.4; P = .002 and β = 3.4; 95% CI, 0.7 to 6.2; P = .015, respectively). Increased respiratory resistance at 5 Hz at age 4 years was also associated with decreased lung function from ages 5 to 8 years (β = -0.3; 95% CI, -0.5 to -0.1; P < .001 for FEV1 at 8 years) and active asthma at age 8 years (β = 2.0; 95% CI, 0.2 to 3.8; P = .029). CONCLUSIONS:Increased respiratory resistance in preschool IOS is associated with frequent respiratory symptoms as well as school-age asthma and lung function impairment. Our findings suggest that IOS may serve as a potential objective measure for early identification of children who are at high risk of respiratory morbidity.