HRCT imaging of asthma demonstrates wall thickening of the segmental bronchi. This abnormality may be related to irreversible changes in the bronchial wall, remodeling, or to reversible inflammation. If bronchial wall thickening is due to remodeling, wall morphology should not change when inflammation is treated. We hypothesized that asthmatics studied during and after a clinical exacerbation would show a decline in airway inflammation as measured by exhaled nitric oxide (NO) accompanied by a decrease in bronchial wall area/total bronchial cross section area x 100 (Bronchial wall area %).
We enrolled nine severe persistent asthmatics during acute asthma exacerbations. All patients underwent low radiation dose HRCT scanning of the right upper lobe apical bronchus, measurement of exhaled nitric oxide (NO) and spirometry. Patients were treated with systemic corticosteroids or increased amounts of inhaled corticosteroids at doses selected by their pulmonary physicians. After a minimum of 6 weeks subjects returned for repeat testing. Seven control subjects also underwent HRCT, exhaled nitric oxide measurement and spirometry on two occasions for comparison.
The nine asthmatics had bronchial wall area % and exhaled NO greater than controls 58 ± 4 vs. 48 ±5 (p<.05) and 30 ± 4 ppb vs. 14 ±3 ppb (p<.005) respectively . Following treatment the FEV1 per cent of predicted among asthmatic patients markedly improved 0.45±.08 vs. 0.76±.08 (p<.05). Exhaled NO decreased modestly, 30 ± 5ppb vs. 26 ±5 (p<.05) and bronchial wall area% did not change significantly 58± 4 vs. 65± 4 . Bronchial wall area % and exhaled NO did not change in controls and both remained significantly less than seen in asthmatics.
Bronchial wall thickening can persist after treatment of acute asthma exacerbation despite marked improvement in spirometry and decline in NO. Persistent bronchial wall thickening may be due to chronic airway remodeling.
HRCT measurement of bronchial wall thickeness in not likely to be accurate in assessing airway inflammation among patients with severe persistent asthma.
L.H. Ketai, None.