Spirometry and Impulse Oscillometry in Preschool Children: Acceptability and Relationship to Maternal Smoking in Pregnancy

Background: Comparisons of the technical acceptability of spirometry and impulse oscillometry (IOS) and clinical correlations of the measurements have not been well studied in young children. There are no large studies focused on African American and Hispanic children. Objectives: We sought to (1) compare the acceptability of spirometry and IOS in 3- to 5-year-old children and (2) examine the relationship of maternal smoking during pregnancy to later lung function. Methods: Spirometry and IOS were attempted at 4 sites from the Urban Environmental and Childhood Asthma Study birth cohort at ages 3, 4, and 5 years (472, 471, and 479 children, respectively). We measured forced expiratory flow in 0.5 s (forced expiratory volume in 0.5 seconds [FEV_0.5]) with spirometry and area of reactance (A_X), resistance and reactance at 5 Hz (R₅ and X₅, respectively) using IOS. Results: Children were more likely to achieve acceptable maneuvers with spirometry than with IOS at age 3 (60% vs 46%, P <.001) and 5 years (89% vs 84%, P =.02). Performance was consistent among the 4 study sites. In children without recurrent wheeze, there were strong trends for higher FEV_0.5 and lower R₅ and A_X over time. Maternal smoking during pregnancy was associated with higher A_X at ages 4 and 5 years (P <.01 for both years). There was no significant difference in FEV_0.5 between children with and without in utero exposure to smoking. Conclusion: There is a higher rate of acceptable maneuvers with spirometry compared with IOS, but IOS may be a better indicator of peripheral airway function in preschool children.