Background The gold standard for diagnosing asthma is spirometry, but performance in preschool children is poor. Forced Oscillation Technique (FOT) is an alternative for assessing pulmonary function. It measures airway resistance and reactance by superimposing sound waves on tidal breathing. Because of minimal effort and cooperation needed, it might be more feasible to use in preschool children.

Aim To assess whether FOT can reliably discriminate differences in pulmonary function in healthy and wheezing children.

Methods Healthy and wheezing preschool children were recruited in this cross-sectional study. Wheezing children were given a probability diagnosis of asthma or transient wheeze based on a breath test (Klaassen et al. AJRCCM 2015;191:201-7). TremoFlo® was used for FOT measurements to determine R5, X5, AX and R5-20 before and after inhalation of salbutamol.

Results Eighty healthy and 220 wheezing preschool children were included, of which a preliminary analysis of 13 healthy and 103 wheezing children was performed. There were no differences found at baseline between healthy and wheezing children. Only the percentage improvement in AX after bronchodilation was significantly higher in wheezing children compared to healthy (33.8% vs 58.8%, p=0.010). The R5-20 was significantly higher in transient wheezing children (n=82) compared to asthmatics (n=18) (1.6 vs 0.7 kPa.s.L-1, p=0.005).

Conclusion This preliminary analysis of FOT in preschool children showed some differences between healthy and wheezing children, and between children with a likelihood diagnosis of asthma and transient wheeze. Analysis of the full cohort is ongoing and will be presented at the conference.