Impulse oscillometry usefulness in small-airway dysfunction in asthmatics and its utility in asthma control

Background Small-airway affection and its relation to clinical status in asthmatic patients became an increasing interest during the last decade. Spirometry is a basic diagnostic tool for measuring pulmonary function in asthmatics but not fully illustrative especially in assessing small airways. Impulse oscillometry (IOS) can be considered a complementary and sometimes alternative technique to spirometry because it is used during quiet breathing and so gives more data about small-airways affection in asthmatic patients. Aim To evaluate IOS usefulness in the detection of small-airways disease in asthma and its correlation to the level of disease control. Patients and methods The study was conducted on 44 asthmatic patients who were classified into two groups: controlled asthma and uncontrolled asthma by asthma control test questionnaire (ACT score). Spirometry and IOS were performed on all patients. Results Small-airway IOS values (R5–20, X5, and AX) were found to be statistically significant between two groups. Moreover, they strongly correlated significantly with clinical symptoms, assessed by ACT. There was high sensitivity and specificity of (R5–20) 80 and 82%, (X5) 80 and 86%, and (AX) 86 and 89%, while for spirometric data only forced expiratory flow (FEF25–75%) showed a statistically significant difference between the two groups, and not FEV1% and there was poor correlation between ACT and FEF25–75%. Conclusion IOS provides an easy and rapid tool to diagnose and assess small-airways disease in adult, asthmatic patients