Airway wall thickness in patients with near fatal asthma and control groups: assessment with high resolution computed tomographic scanning

Abstract

Background-Airway wall thickening has been observed in post mortem studies 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 patients with asthma and 14 normal controls. Methods-The subjects were prospectively 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. High resolution (1 mm collimation) CT scans of the chest were done at five diVerent levels. Results-The mean (SD) forced expiratory volume in one second (FEV 1 ) 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 wall area (WA%) defined as (wall area/total airway area) × 100 were used to compare airway wall thickness between the groups. The mean (SD) T/D and WA% were 0.27 (0.05) and 78.0 (9.2)% for group 1, 0.27 (0.05) and 78.8 (9.2)% for group 2, 0.25 (0.04) and 74.2 (7.5)% for group 3, and 0.23 (0.04) and 70.9 (8.2)% for group 4. T/D and WA% were not significantly diVerent 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 diVerences (95% CI) between the groups in WA% were 7.1% (0 to 14.4) for groups 1 and 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 diVerences between the groups in T/D and WA% were noted both for those with airways with a luminal diameter of >2 mm and those with a luminal diameter of <2 mm. Conclusions-All the patient groups had greater airway wall thickening than the 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 assessing airway calibre in early intervention studies with antiinflammatory therapy. (Thorax 1998;53:248-253)

Evaluation of Airway Wall Thickness Via High-Resolution Computed Tomography in Mild Intermittent Asthma

“…5 However, given the higher degree of airway thickening in subjects with nearly fatal and moderate asthma than in Values are given as the mean ϭ SD unless stated otherwise. T/D ratio ϭ bronchial wall thickness to bronchial lumen diameter ratio WA% ϭ bronchial wall area percentage PEF ϭ peak expiratory flow subjects with mild asthma, 13 the inclusion of control subjects with mild intermittent asthma in the present study seems consistent with our findings of similar T/D values for both segmental and subsegmental airways between the subject and control groups. Accordingly, significantly higher subsegmental WA% values for the measurements at the level of inferior pulmonary vein and 2 cm above the diaphragm in the subject group than in the control group in the present study seem to indicate that increased bronchial wall thickness among subjects with mild intermittent asthma was specific to small peripheral airways, as has also been confirmed in a study on childhood asthma.…”

“…Accordingly, significantly higher subsegmental WA% values for the measurements at the level of inferior pulmonary vein and 2 cm above the diaphragm in the subject group than in the control group in the present study seem to indicate that increased bronchial wall thickness among subjects with mild intermittent asthma was specific to small peripheral airways, as has also been confirmed in a study on childhood asthma. 19 Besides, increased segmental and subsegmental bronchial wall area in our subjects compared to control subjects supports the idea that the use of WA% in the evaluation of both segmental and subsegmental bronchial walls was associated with increased bronchial wall thickness in both small and large airways in subjects with mild-tomoderate asthma 13,17 and in subjects with nearly fatal asthma, with the thickening being directly proportional to the severity of the disease. 13 Likewise, given that the inflammation involves the whole wall of the bronchus, leading to an obstruction, measurements taken from a single point were reported to be associated with incorrect findings, while WA% was indicated to be a more relevant method in the reflection of the changes in bronchial wall thickness.…”

“…19 Besides, increased segmental and subsegmental bronchial wall area in our subjects compared to control subjects supports the idea that the use of WA% in the evaluation of both segmental and subsegmental bronchial walls was associated with increased bronchial wall thickness in both small and large airways in subjects with mild-tomoderate asthma 13,17 and in subjects with nearly fatal asthma, with the thickening being directly proportional to the severity of the disease. 13 Likewise, given that the inflammation involves the whole wall of the bronchus, leading to an obstruction, measurements taken from a single point were reported to be associated with incorrect findings, while WA% was indicated to be a more relevant method in the reflection of the changes in bronchial wall thickness. 20 The pathological features of bronchial wall thickening may reflect not only irreversible airway remodeling, such as hypertrophy of mucus-secreting glands, subepithelial fibrosis, marked thickening of basement membrane, hyperplasia, and hypertrophy of airway smooth muscle, but also reversible components, such as edema, infiltration by inflammatory cells, and bronchoconstriction.…”

“…15 In the present study, airway dimensions of both segmental and subsegmental bronchi were measured directly from magnified HRCT images, and the results were expressed based on calculation of the T/D and the WA%. While similar studies in the literature evaluated bronchial wall thickness based on the measurement of T/D only (Boulet et al 16 ) and the calculation of WA% only (Okazawa et al 17 ), we used both T/D and WA% to assess thickening of the segmental and subsegmental bronchi, and compared our results to those in studies conducted by Awadh et al, 13 Niimi et al, 18 and Gono et al 5 The results of these studies revealed inconsistent data, including no bronchial wall thickening in large airways, 16 and increased thickness in large airways, 18 in airways Ͻ 6 mm in luminal diameter, 17 and also in both large and small airways 13 among asthmatic subjects compared to control subjects, as well as in asthmatic subjects with deficient reversible airflow obstruction compared to asthmatic subjects with normal spirometric functions. 5 However, given the higher degree of airway thickening in subjects with nearly fatal and moderate asthma than in Values are given as the mean ϭ SD unless stated otherwise.…”

Chest CT Findings in EBUS-TBNA-Proven Anthracosis in Enlarged Mediastinal Lymph Nodes

“…The thickening of bronchial walls as a sign of chronic bronchitis was classified as moderate or severe compared with the representative HRCT images of airway wall thickness as published by Awadh et al [11]. Vascular attenuation (thinning of pulmonary vessels and reduction in their number) and distortion (increased branching angle or straightening) were considered as signs of emphysema.…”