A study of the use of impulse oscillometry in the evaluation of children with asthma: analysis of lung parameters, order effect, and utility compared with spirometry

Abstract

Background: The ability to objectively measure lung function in children is critical in the assessment and treatment of asthma in this age group. We thus determined the effectiveness of impulse oscillometry (IOS) as a non-invasive technique to assess lung function in children and in comparison to spirometry for sensitivity and specificity, testing variability, and the order effect of sequential testing of IOS and spirometry.

Methods: One hundred seventeen children sequentially evaluated in a pediatric clinic and under medical care for disease, were asked to perform IOS and spirometry. The utility of IOS and spirometry in differentiating children that had asthma versus those children who did not was then analyzed.

Results: In the primary analysis (n = 117), bronchodilator response using IOS distinguished asthmatics from non-asthmatics, P = 0.0008 for R10. Receiver-operator characteristic curve (ROC) analysis of R10 bronchodilator response at the best cut-off (-8.6% change) correctly identified 77% of patients with asthma and excluded 76% of non-asthmatics. Amongst those children able to perform spirometry (asthmatics, n = 66; non-asthmatics, n = 16), FEV(1) did not reveal a difference between these two groups, while area of reactance (AX) did distinguish these groups (P = 0.0092). Sequential testing of IOS and then spirometry (n = 47) showed a significant decrement in lung function as determined by IOS following performance of spirometry (P = 0.0309).

Conclusion: In the diagnosis and management of children with lung disease, IOS is a non-invasive approach that easily and objectively measures lung impedance and should be considered as both an adjunct, and in some situations, an alternative to standard spirometry.

Fig 1

ROC curves for IOS. A: Receiver operator characteristic curves for R5, R10, X5, and AX are displayed (n = 117) comparing asthmatics and non-asthmatics. Area-under-curve (AUC) is calculated to indicate the profile of sensitivity and specificity for each test parameter. Best cut-off value for R10 in noted. B: ROC for CV index (bronchodilator response/2CV) CV index ≥1 indicates positive response.

Fig 2

ROC curves IOS versus FEV₁. ROC curves in patients able to perform both IOS and spirometry (n = 82—asthmatics; n = 66 non-asthmatics; n = 16).

Fig 3

Order effect of IOS, spirometry and IOS. A total of 47 patients evaluated with baseline IOS, spirometry and immediate repeat IOS with mean and interquartile ranges for reactance and resistance. Outliers are indicated in red (n = 5).