Diagnosing and monitoring asthma using the Forced Oscillation Technique in children under 5 years with wheeze

Background: The assessment of lung function in young children is helpful to the diagnosis, treatment, and management of paediatric respiratory disease.

Since measuring lung function for such patients can be challenging, specific lung function tests for this age group have been developed, including Forced Oscillation Technique (FOT), a non-invasive method of measuring respiratory impedance (Zrs), requiring minimal cooperation from the patient.

Aims: To investigate feasibility and the application of FOT in preschool children with wheeze; and to assessed bronchodilator response (BDR) in children with acute wheeze. 

Methods: Preschool children with physician-diagnosed asthma were recruited from the Asthma Clinic, ED and Children’s ward at Leicester Royal Infirmary Hospital. Following a standardized physical examination, three measurements of respiratory resistance and reactance by forced oscillation were attempted.

Results: Twenty of twenty-four stable preschool children with wheeze are able to successfully complete the forced oscillation technique. Thirteen of 39 of preschool children with acute wheeze performed FOT using airwaveoscillometry system (AOS) 7-41 with good quality control and CoV ≤ 15%.

Children with acute wheeze had statistically significantly higher Rrs7, Rrs7 zscore, Rrs7-20 and Ax7, and lower Xrs7 and Xrs7 z-score compared to healthy children. The average of bronchodilator response on preschool children with acute wheeze was -18% for Rrs7, -47% for Rrs7-20, 33% for Xrs7 and -17% for Ax7.

Conclusion: These findings highlight the FOT (AOS 7-41 Hz) is feasible in preschool children for routine testing of lung function and in ED. In addition, this study demonstrates that more work is required to understand the value of FOT to differentiate preschool children with acute wheeze from healthy children due to the overlap between individual participants in acute wheeze and healthy groups on FOT parameters. However, there are significant differences between children with physician diagnosis of acute wheeze and healthy children at baseline, as assessed by Rrs7, Rrs7-20, Xrs7, and Ax7 (p value = 0.004, 0.02, 0.00, and 0.00) respectively. Also, comparing pre- and post-bronchodilator response of acute wheeze revealed a statistically significant difference in all FOT measurements (p-value < 0.05).