Detection of small airways disease by impulse oscillometry among smokers and non-smokers with normal spirometry

Abstract

Title: Detection of small airways disease by impulse oscillometry among smokers and non-smokers with normal spirometry.

Background: Smoking is recognized to be the most important risk factor for development of chronic airway diseases. Small airways (<2mm) are the major site of airflow obstruction and small airways dysfunction (SAD) can occur in subjects with preserved spirometry. Impulse oscillometry (IOS) offers advantages of being effort independent with a higher sensitivity to SAD. This study explores the diagnostic utility of IOS to detect SAD in smokers and non-smokers.

Methods: This was a prospective, cross-sectional study which assessed the IOS results in 102 subjects with preserved spirometry and its correlation to smoking status and quality of life (CAT score). R5-R20 results on IOS were analysed to detect SAD.

Results: 102 subjects were included with 51 current or past smokers (>10 pack years history) and 51 non-smokers. Baseline demographics were matched across the two groups. The mean age was 49 years with male predominance (77.5%). Smokers had a significantly higher incidence of SAD on IOS despite preserved spirometry (31.37% vs 5.89%, p=0.0005). Higher pack year history correlated significantly with development of SAD (p=0.0001). Subjects with presence of SAD had worse mean CAT scores (11.79 vs 4.69, p=0.001). Higher pack year history also correlated with worse CAT scores. (p<0.001).

Conclusion: Impulse oscillometry is more sensitive than spirometry in diagnosing SAD. With the advantage of being effort independent, it can thus be used as an adjunct for early diagnosis and monitoring of airway diseases.