Abstract
Background: In preschoolers, performing an acceptable
spirometry and measuring bronchodilator response (BDR) is challenging;
impulse oscillometry (IOS) may be an alternative to spirometry. However,
there is still no consensus in standardization of BDR for IOS in young
children. Objective: The objective of the study was to identify
optimal thresholds to define a positive BDR test with IOS.
Methods: Young infants aged 3 to 6 years with suspected asthma
were evaluated in a real life setting with both IOS and spirometry pre-
and post-BDR. The BDR was defined as positive when the change of FEV1
was ≥12% and/or ≥200 mL. Results: Among 72 patients (age 4.98
± 0.94 years; 64% boys), 36 (age 5.15 ± 0.99 years; 64% boys) were
selected for the subsequent analysis according to ATS / ERS quality
criteria of measurements. The spirometric BDR was found positive in
seven subjects (19.4%). In IOS, the mean decrease in R5 and AX was
19.86% ± 10.04 and 44% ± 22.10, and the mean increase in X5 was
23.28% ± 17.82, respectively. A decrease in R5 of 25.7% (AUC 0.77, p =
0.03) and an increase in X5 of 25.7% (AUC 0.75, p = 0.04) showed the
best combination of sensitivity and specificity to detect an increase of
FEV1 ≥12% and/or ≥200 mL. Conclusion: The IOS may present a
valid alternative to spirometry to measure BDR in preschool children. We
are considering a decrease of 26% in R5 and an increase of 26% in X5
as diagnostic threshold for BDR.