Abstract
Background: Lung clearance index (LCI) from N2 multiple breath washouts (MBW) is known as a sensitive marker of peripheral airway obstruction (ERJ 2013;4:507). Airway function declines with age but the association between ageing and peripheral airway function is not fully known.
Aim: To see if airway function decline with ageing is more closely related to the LCI than to the FEV1/FVC ratio from spirometry or the residual volume/total lung capacity (RV/TLC) ratio obtained by body plethysmography.
Subjects and methods: 313 (160 males) subjects without any history of lung disease, aged 60-86 yrs (median 72.0), performed triplets of N2 MBW using the ExhalyzerD (EcoMedics AG, Duerten, Switzerland) and spirometry. In 296 subjects measurements of RV and TLC were added using body plethysmography (Jaeger, Masterscreen, Care Fusion, Germany). Statistical analysis using IBS SPSS, included simple and multiple regression analyses.
Results: Simple regression disclosed moderate relationship between age and RV/TLC (r² 0.33; p<0.001) and age and LCI (r² 0.28, p<0,001), but poor association between age and FEV1/FVC (r² 0.01; p=0.05). While LCI and RV/TLC were moderately associated (r² 0.25; p<0.001), FEV1/FVC was not related to RV/TLC (r² 0.00; n.s.) and weakly to LCI (r² 0.03; p<0.01). In a multiple regression model with age as dependent variable, 39 % of overall variance was explained by the three lung function variables. RV/TLC contributed uniquely by 14%, LCI by 6% and FEV1 by <1%. RV/TLC and LCI contributed by 6% shared variance.
Conclusion: Peripheral airway ageing is poorly reflected in FEV1/FVC ratio, but moderately well described by RV/TLC ratio and LCI.
- Copyright ©ERS 2015
