Assessment of Airway Wali Thickness by High-Resolution Computed Tomography in Patients With Asthma of Different Degree of Severity

To measure airway wall thickness at the segmental and subsegmental levels, HRCT scanning was performed in 30 patients with asthma and in 10 normal controls. The subjects were prospectively divided into four groups: 10 normal controls (group 1), 10 patients with mild asthma (group 2), 10 patients with moderate asthma (group 3), and 10 patients with severe asthma (group 4). HRCT (1.5 mm collimation) scans of the chest were done at five different levels. The ratio of airway wall thickness to outer diameter (T/D) and the percentage wall area (WA %) defined as [(wall area/total airway area) x 100] were used to compare airway wall thickness between the groups. Mean (SD) forced expiratory volume in one second (FEVj) was 102.10 (5.47) % for group 1, 95.10 (13.40) % for group 2, 68.50 (19.67) % for group 3, and 45.0 (15.30) % for group 4. Mean (SD) T/D and WA% were 0.23 (0.05) and 70.28 (10.28) % for group 1, 0.26 (0.05) and 75.14 (9.95) % for group 2, 0.27 (0.05) and 78.09 (10.40) % for group 3, and 0.29 (0.04) and 81.72 and WA% than group 3 (p<0.001). The differences between the groups were noted both for small airways (with a luminal diameter of >2 mm) and for the larger airways (with a luminal diameter of <2 mm). The results of the study indicate that, as assessed by HRCT scanning, all patients with asthma had some degree of airway wall thickening compared to normal subjects. The methodology described in this study may be useful in assessing airway wall thickness in asthma.