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Updated: Sep 14, 2025
Conducting Respiratory Oscillometry in an Outpatient Setting
Published on: April 8, 2022
A Comparison of Impulse Oscillometry and Spirometry by Percent Predicted in Identifying Uncontrolled Asthma
Chalerm Liwsrisakun1, Chaicharn Pothirat1, Athavudh Deesomchok1
1Division of Pulmonary, Critical Care and Allergy, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
Background:
The role of impulse oscillometry (IOS) in evaluating asthma control remains a challenge because the interpretation varies by many factors, including ethnicity. We aimed to assess the diagnostic contribution of spirometry and IOS, established from reference equations, in the detection of uncontrolled asthma.
Methods:
This retrospective study was conducted in adult asthma subjects with normal spirometry. Uncontrolled asthma was defined as an Asthma Control Test (ACT) score ≤ 19. Receiver operating characteristic (ROC) curves were plotted to compare the diagnostic abilities of the %-predicted of heterogeneity of resistance at 5 Hz and 20 Hz (R5-R20) and the %-predicted of forced expiratory volume in the first second (FEV1) in detecting uncontrolled asthma. Multivariable risk regressions were performed to identify the %-predicted of R5-R20 as a predictor for uncontrolled asthma.
Results:
The %-predicted of R5-R20 demonstrated a superior diagnostic ability for detecting uncontrolled asthma compared to the %-predicted FEV1, with the area under the ROC curves (AuROC) = 0.939 vs. 0.712, respectively, p < 0.001. The %-predicted R5R20 of ≥200 showed the highest AuROC for detecting uncontrolled asthma with an adjusted risk ratio of 10.86 (95%CI; 3.77, 31.29; p < 0.001).
Conclusions:
IOS demonstrated better diagnostic ability for detecting uncontrolled asthma than spirometry.
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