Monitoring Asthma in School-aged Children using the Forced Oscillation Technique

Background: Diagnosing asthma in school-aged children can be difficult, as spirometry can be challenging and even when successful is often normal when the patient is stable. Forced Oscillation Technique (FOT) could offer a rapid, non-invasive alternative test that reflects the resistance and reactance of the lungs during spontaneous breathing, requiring minimal patient cooperation.

Aims: To assess FOT measurements in children with acute, stable and uncontrolled asthma before and after bronchodilator administration (BDR), while also comparing the FOT to other lung function tests.

Methods: Children aged 5–16 years with stable controlled or uncontrolled asthma or doctor-diagnosed asthma attacks were eligible. A control group of healthy children in the same age range was also included. After obtaining informed consent, we assessed FOT using waveforms of 5–37 Hz and 7–41 Hz, before and after bronchodilation with salbutamol inhalation in asthma patients only. We reported, each at 5 or 7 Hz, the (i) resistance (Rrs5 or Rrs7), (ii) differences in resistance over the frequency range to 20 Hz (Rrs5-20 or Rrs7-20), (iii) reactance (Xrs5 or Xrs7) and (iv) area under the reactance curve (AX).

Results: FOT was feasible in cases of stable controlled and uncontrolled asthma and in children with asthma attacks. Of the reported parameters, AX best discriminated between asthmatic and healthy children. FOT measurements were more sensitive in children with stable asthma with diagnoses confirmed by objective tests than in those with incomplete or no evidence. In addi-tion, FOT measurements at 5–37 Hz and 7–41 Hz showed significant airway improvements following bronchodilator in children with acute and uncontrolled asthma, with no significant differences between measurements at different frequencies.

Conclusion: FOT measurements, including the assessment of BDR, are feasible in school-aged children with asthma. FOT is a useful method that could be applied alongside additional objective testing methods in asthmatic children.