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 d ue to airway hypereactivity. MATERIALS AND METHODS: Spirometry and hel ical CT were performed in 15 patients with mild asthma and six healthy control subjects before and after bronchial tron with metacholine chl oride and after reversal of provocation with albuterol. CT was perform ed at suspended functional residual capacity and at residual volume in two lung regions (above and below the carina). Bronchial area and lun g attenuation measurements were compared. RESULTS: At baseline, lung a ttenuation frequency distribution curves were similar between the cont rol 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. Pati ents with asthma showed a 20%-36% decrease in FEV1, with significant d ecreases 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 n o change in spirometric measurements, lung attenuation, or bronchial s ize, whereas all such parameters returned to baseline levels in patien ts with asthma. CONCLUSION: Functional helical CT can accurately demon strate reversible airflow obstruction resulting from airway hyperreact ivity.