Clinical impact of obesity on oscillometry lung mechanics in adults with asthma

Background In the year 2035, projections have estimated that 5% of the Scottish population will be morbidly obese defined as a body mass index (BMI) greater than or equal to 40 kg/m 2 . Airway oscillometry is an effort-independent test akin to bronchial sonar which measures resistance and compliance. Objective To evaluate the impact of obesity on lung mechanics using oscillometry. Methods Clinical data for 188 patients with respiratory physician–diagnosed moderate-to-severe asthma were retrospectively collected and analyzed. Results Obesity (BMI 30-39.9 kg/m 2 ) and morbid obesity (BMI ≥ 40 kg/m 2 ) were associated with a significantly worse heterogeneity of peripheral resistance between 5 Hz and 20 Hz and peripheral compliance as low-frequency reactance at 5 Hz and area under the reactance curve, as compared with normal weight (BMI 18.5-24.9 kg/m 2 ). Cluster analysis incorporating oscillometry identified a patient cohort who was older, obese, and female with combined impairment of spirometry and oscillometry coupled with more frequent severe exacerbations. Conclusion Obesity is associated with worse peripheral airway dysfunction in moderate-to-severe asthma, including a patient cluster who was older, obese, and female with more frequent exacerbations.