Expiratory air trapping during asthma exacerbation: Relationships with clinical indices and proximal airway morphology

Abstract

© 2015 Elsevier Ireland Ltd. All rights reserved. Objectives To semi-quantitatively assess expiratory air trapping (ATexp) and structural changes in the proximal airways in asthma during asthma exacerbation (AE) and to explore the relationships among ATexp, clinical indices, and proximal airway changes. Methods Paired inspiratory-dynamic forced expiratory CT scans of 36 asthmatics (30 women, 6 men; mean age, 49.2 ± 18.9 years) performed during AE were retrospectively reviewed for the total ATexpscore (summed scores [extent grading (0-4) × pattern grading (1-4)] of the twelve lung zones), morphologic parameters and expiratory bronchial collapse (BCexp) of the proximal airways. The relationships of the score with clinical indices and proximal airway morphology (normalized by body surface area [BSA]) were analyzed. A p value of <0.05 was considered statistically significant. Results The mean total ATexpscore was 110.1 ± 43.4 (range, 8-166). It was higher in the lower zones and in patients older than 60 years, having BMI of <27.5 kg/m2, and peak expiratory flow rate (PEFR) of <60% predicted. Correlation existed between the score and age (r = 0.331), BMI (r = -0.375), BSA (r = -0.442), % predicted PEFR (r = -0.332), right upper lobe apical segmental bronchus (RB1)-wall area (WA)/BSA (r = 0.467), %RB1-WA (r = 0.395), and RB1-bronchial wall thickness (BWT)/BSA (r = 0.378). The score showed no correlation with BCexpand other morphologic bronchial parameters. Area under receiver-operating-characteristic curve 0.724 (95% CI) showed that the score of 110 could discriminate patients with PEFR of <60% predicted from those with PEFR of 60% predicted. Conclusion During AE, there was a high prevalence of extensive ATexpwhich was correlated with patient's age, BMI, BSA, AE severity and RB1 morphology but not correlated with BCexp.