Impulse Oscillometry in Respiratory Disease Diagnosis and Management

Primary Role and Clinical Positioning

The European Respiratory Society guidelines state that resistance measurements (including forced oscillation technique/IOS) have no clinical advantage over FEV1 measurement in most COPD situations, with spirometry remaining the gold standard for diagnosis and severity assessment 3, 2, 4
IOS measures respiratory resistance during normal tidal breathing using sound waves, requiring minimal patient cooperation compared to forced expiratory maneuvers, making it especially useful in children, elderly patients, and those unable to perform adequate spirometry 1

For bronchodilator response in children with chronic respiratory symptoms, a decrease in Rrs0 of ≥27.8% (or >-1 SD score) demonstrates 69% sensitivity and 78% specificity compared to FEV1 increase of ≥10% predicted, according to the European Respiratory Society 1, 5
Post-bronchodilator changes in COPD typically show decreased Rrs (especially at low frequencies) and increased Xrs, with correlation to FEV1 changes dependent on the magnitude of bronchodilator response, as stated by the European Respiratory Society 1, 5

Spirometry with FEV1/FVC ratio <0.7 post-bronchodilator remains the diagnostic threshold for airflow obstruction per European Respiratory Society guidelines, which cannot be established by IOS 7
FEV1 percentage predicted determines COPD severity classification (Mild ≥70%, Moderate 50-69%, Severe <50%), which cannot be derived from IOS parameters, according to the European Respiratory Society 3, 7

IOS requires less patient cooperation than spirometry as measurements occur during normal tidal breathing, making it feasible in populations where spirometry cannot be performed, as noted by the European Respiratory Society 1
Home-based IOS measurements appear feasible and may demonstrate advantages over peak flow for asthma monitoring, though diagnostic utility requires further study, according to the American Thoracic Society 8