AIRWAY WALL THICKNESS IN PATIENTS WITH NEAR-FATAL ASTHMA AND CONTROL-GROUPS - ASSESSMENT WITH HIGH-RESOLUTION COMPUTED TOMOGRAPHIC SCANNING

Background-Airway wall thickening has been observed in post mortem stu dies of patients with asthma, Assessment of airway wall thickening by high resolution computed tomographic (HRCT) scanning has been reported in experimental studies. We have used HRCT scanning to measure airway wall thickness at the segmental and subsegmental levels in 40 patient s with asthma and 14 normal controls, Methods-The subjects were prospe ctively divided into four age and sex matched groups: 14 patients with a history of near fatal attack of asthma (NFA; group 1), 12 patients with moderate asthma (group 2), 13 patients with mild asthma (group 3) , and 14 normal controls (group 4), All subjects were non-smokers. Hig h resolution (1 mm collimation) CT scans of the Chest were drone at fi ve different levels. Results-The mean (SD) forced expiratory volume in one second (FEV1) was 68 (20)% of predicted for group 1, 73 (12)% for group 2, 102 (12)% for group 3, and 103 (12)% for group 4. The ratio of airway wall thickness to outer diameter (T/D) and the percentage wa ll area (WA%) defined as (wall area/total airway area) x 100 were used to compare airway wall thickness between the groups. The mean (SD) TI D and WA% were 0.27 (0.05) and 78.0 (9.2)% for group 1, 0.27 (0.05) an d 78.8 (9.2)% for group 2, 0.25 (0.04) and 74.2 (7.5)% for group 3, an d 0.23 (0.04) and 70.9 (8.2)% for group 4. T/D and WA% were not signif icantly different between groups 1 and 2. However, both groups 1 and 2 had higher T/D and WA% than either group 3 or 4 (p < 0.001) and group 3 had a higher T/D and WA% than group 4 (p < 0.03). The differences ( 95% CI) between the groups in WA% were 7.1% (0 to 14.4) for groups 1 a nd 4, 3.8% (-3.4 to 10) for groups 1 and 3, and 3.3% (-4.4 to 10) for groups 3 and 4. The differences between the groups in TID and WA% were noted both for those with airways with a luminal diameter of >2 mm an d those with a luminal diameter of less than or equal to 2 mm. Conclus ions-All the patient groups had greater airway wall thickening than th e normal subjects as assessed by HRCT scanning, but patients with more severe asthma had greater airway wall thickening than those with mild asthma. The methodology described in this study may be useful in asse ssing airway calibre in early intervention studies with antiinflammato ry therapy.