Published online: February 13, 2018
Objective assessment of pulmonary function in preschool children is challenging but potentially may contribute important information for clinical practice or research in lung development or disease. Spirometry and impulse oscillometry (IOS), an application of the forced oscillation technique, are the most commonly used methods of assessment of pulmonary function. The theoretical advantage of IOS is that the test is effort-independent and would be more likely to yield acceptable tests in preschool children. Large studies comparing performance on the two tests are lacking. Furthermore, the populations studied have been predominantly white children.
In an article recently published in The Journal of Allergy & Clinical Immunology: In Practice, Kattan and colleagues compared the ability of predominantly black and Hispanic preschool children to perform the maneuvers. Smoking during pregnancy has been associated with reduced lung function in infants and older children but not in preschool children. The authors assessed the ability of IOS and spirometry to detect changes in respiratory system properties by determining the association between umbilical cord cotinine and pulmonary function as measured by the two tests.
Spirometry and IOS were done in the Urban Environment and Childhood Asthma study (URECA), a birth cohort study that is part of the Inner City Asthma Consortium sponsored by the National Institute of Allergy and Infectious Disease. As expected, performance on both tests improved with age. The study confirmed that pulmonary function can be performed with a high degree of success in 4- and 5-year-old children. At 3 years of age more children had acceptable tests with spirometry compared to IOS. Of the 609 children initially enrolled in URECA, 485 had attended at least one visit and attempted a pulmonary function test at ages 3, 4, or 5 years. At ages 3, 4, and 5 years, 78%, 90%, and 93%, respectively, were willing to perform spirometry and 79%, 89%, and 90%, respectively, were willing to perform IOS. At 3 years 60% of children who attended the visit had an acceptable test with spirometry compared with 46% with IOS (p<0.001). By 5 years 89% had acceptable spirometry compared to 84% with IOS. The longitudinal study design and large number of children with no history of recurrent wheezing provided normative data for African American and Hispanic children. The study found that umbilical cord cotinine was associated with a greater area of reactance determined by IOS but not lower FEV0.5 determined by spirometry.
The study does not support the belief that IOS is easier for younger preschool children to perform. The ability of IOS but not spirometry to detect changes in lung function related to in utero cigarette smoke exposure may reflect the fact that IOS measures both resistive and elastic properties. IOS and spirometry may reflect different aspects of respiratory system mechanics.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.