Relationship between physical activity and quantitative inspiratory-to-expiratory CT imaging

Rationale: Although the development of CT imaging can help us to understand the complex pathophysiology of lung diseases, the association with physical activity (PA) and multiple CT metrics remain unknown. The aim of the study is to investigate whether inspiratory-to-expiratory CT imaging show promise for use as biomarkers in PA. Methods: Parametric response mapping(PRM), expiratory/inspiratory mean lung density ratio (E/I) and expiratory/inspiratory mean normal lung density ratio (ND-E/I) through the use of inspiratory and expiratory CT scan and PA by use of a triaxial accelerometer was evaluated in healthy(n=6), asthmatics(n=27) and COPD(n=14). PRM classifies lung as normal, functional small airway disease (PRMfSAD), and emphysema (PRMEMPH). Exercise (Ex) was calculated by metabolic equivalents (METs) multiplied by PA duration and low activity (LA) was defined exercise as Ex below 1.5. Results: 6 patients were classified as the LA group and 41 patients as the activity maintenance (MA) group. LA group was more likely to be heavy smokers, have low pulmonary function and hyperinflation. Moreover, LA group show higher PRMfSAD (41.6 vs 29.8, p Conclusion: Quantitative inspiratory-to-expiratory CT imaging can be biomarker to detect physical activity levels.