Bronchodilator response using oscillometry to detect uncontrolled asthma

Dear Editor, Bronchodilator response (BDR) is helpful in the diagnosis and evaluation of symptom control in asthma. A positive BDR by spirometry is defined as a greater than 12% and 200 mL change from baseline in forced expiratory volume in 1 sec (FEV1). Spirometry reliability depends on active patient cooperation and their ability to perform forced expiration maneuvers. This can often be an issue in populations such as children and the elderly. Oscillometry is a non-invasive and relatively effort-independent technique to evaluate respiratory mechanics during tidal breathing. The cutoff values for BDR in oscillometry were calculated from healthy subjects and asthma patients. However, comparability across different devices and the applicability of existing reference values remain challenging. A comparative study using phantom models found that the measured impedance values were confirmed to be almost consistent, but not identical, with more negative respiratory system reactance (Xrs) values in IOS than those in MostGraph.