Airway hyperreactivity: Assessment with helical thin-section CT

PURPOSE: To determine the accuracy of helical computed tomography (CT) for assessing reversible changes in bronchial size and air trapping due to airway hypereactivity. MATERIALS AND METHODS: Spirometry and helical CT were performed in 15 patients with mild asthma and six healthy control subjects before and after bronchial tron with metacholine chloride and after reversal of provocation with albuterol. CT was performed at suspended functional residual capacity and at residual volume in two lung regions (above and below the carina). Bronchial area and lung attenuation measurements were compared. RESULTS: At baseline, lung attenuation frequency distribution curves were similar between the control and asthma: groups. After methacholine, control subjects showed a decrease of less than 10% in the forced expiratory volume at 1 second (FEV1) and no significant differences in lung attenuation curves. Patients with asthma showed a 20%-36% decrease in FEV1, with significant decreases in the median and 10th percentile regions of the attenuation curves and in the cross-sectional area of small (<5-mm(2)) airways (P < .001 for all comparisons). After albuterol control subjects showed no change in spirometric measurements, lung attenuation, or bronchial size, whereas all such parameters returned to baseline levels in patients with asthma. CONCLUSION: Functional helical CT can accurately demonstrate reversible airflow obstruction resulting from airway hyperreactivity.