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Elevated Lung Clearance Index in Smokers Without COPD

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A1038 - Elevated Lung Clearance Index in Smokers Without COPD
Author Block: M. Funke1, F. Singer2, J. Frey1, S. Nyilas2, T. Schreder1, T. K. Geiser1, P. Latzin2; 1Pulmonary Medicine, University Hospital Bern, University Bern, Inselspital, Bern, Switzerland, 2Department for Pediatric Pulmonology, University Hospital Bern, University of Bern, Inselspital, Bern, Switzerland.
Background:
Early lung disease in cigarette smokers may be present despite lack of symptoms and normal spirometry. Compared to spirometry, nitrogen multiple-breath washout (MBNW) is more sensitive for impaired function of peripheral airways in, for example, Cystic Fibrosis. We compared MBNW indices in smokers with normal spirometry and healthy age-matched controls.
Methods:
In this prospective cross-sectional single-center study we enrolled subjects with FEV1/FVC >0.7 and a history of current or previous cigarette smoking without chronic respiratory symptoms and healthy never-smokers. We applied a health questionnaire, MBNW and spirometry. Primary outcomes were FEV1 from spirometry and lung clearance index (LCI) from MBNW, a measure of global ventilation inhomogeneity. Secondary MBNW outcomes were indices of diffusion- (Sacin) and diffusion-convection (Scond) dependent ventilation inhomogeneity. We compared lung function indices by Mann-Whitney test and prevalence of abnormal findings (±1.64 z-scores).
Results:
We enrolled 46 subjects (24 females) of whom 18 were smokers. Median (IQR) LCI was 7.4 (7.0-8.4) in controls and 8.4 (7.8-9.1) in smokers, p = 0.021. FEV1, Scond and Sacin did not statistically significantly differ on the group level. In the group of smokers, six had abnormal LCI, four abnormal Sacin, three abnormal Scond whereas all had normal FEV1. Abnormal findings were not concordant in the smoking population.
Conclusion:
Despite normal spirometry, MBNW captures subclinical functional impairment predominantly arising peripheral airways. LCI seems a promising biomarker in smokers without chronic obstructive lung disease.
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