Influence of asthma duration on airway wall thickness

Introduction. Airway remodeling can be defined as the "structural changes in the airways that may impair their function". Those changes cause a thickening of the airway walls. HRCT is used (as non-invasive test) to assess thickness of bronchial walls. Only few studies are accessible on the natural progress of the remodeling process and the relationships between the remodeling and duration of asthma have not been explained yet. Aim of the study. The aim of the study was to find out a relationship (if any) between the remodeling in terms of increased thickness of bronchial walls as identified by high-resolution computerized tomography (HRCT) and the duration of bronchial asthma. Material and methods. 30 patients with asthma and 20 healthy control subjects were studied using HRCT. The asthmatics were classified into two groups according to the duration of the disease: 16 patients [group A] <10 years and 15 patients [group B] >10 years. The external (ED) and internal (ID) diameters of segmental or sub-segmental bronchi and their accompanying vessels were measured in the HRCT scans in three fields of the lung: the upper (1.5 cm above), middle (1.5 cm below) and lower (6 cm below the tracheal bifurcation). One millimeter thick HR layers spaced 3 mm apart were defined in the individual fields, 8 layers per each field. Wall thickness (WT) and bronchial wall area (WA) were calculated as follows: WT=(ED-ID)/2; WA%=[11(ED/2)2-11(ID/2)(2)]x100/0. Results. The mean value of bronchial wall thickness in the upper, middle and lower field in the asthmatics was 0.79/0.81/0.97 compared with 0.57/0.62/0.60 in the healthy subjects. The mean value of bronchial wall thickness in patients Group A was: 0.89/0.95/0.99 and in Group B: 0.72/0.79/0.95. WA in the asthmatics was: 70.7/64.8/70.5(%) and 62.6/54.2/49.1(%) in control group. WA in group A was: 73.4/67.1/69.6(%) and in group B 66.6/63.4/70.2(%). A significant increase in the mean value of bronchial wall thickness was observed in the asthmatics (Mann-Whitney U test, p<0.001). No difference was found between Groups A and B. Conclusions. Bronchial walls were thicker in patients with asthma than in non-asthmatic ones. The remodeling of the airways did not depend on the duration of asthma.