Bronchial reactivity in hyperresponsive patients and healthy individuals: demonstration with high resolution computed tomography

Abstract

Objective: High resolution computed tomography (HRCT) was used to assess the extent of bronchial reactivity after inhalative bronchoprovocation and dilation in hyperresponsive patients and healthy subjects. Patients and methods: Patients with mild intermittent asthma, 15 with a >20% decrease in FEV 1 and a >10 mmHg (PC 20+) in PaO 2, 12 with a <20% decrease in FEV 1 and a >10 mmHg (PC 20−) in PaO 2 after provocation, and eight healthy humans were included in the study. Changes in cross-sectional area in a total of 1256 bronchi and in bronchial wall area (792 bronchi) were evaluated after histamine-triggered bronchoprovocation and salbutamol-induced bronchodilation at high lung volumes (FVC 80%). Data were compared with the results of pulmonary function tests (FEV 1, PaO 2, PaCO 2). Results: In all groups, a significant decrease in bronchial cross-sectional area ( P<0.001) and a significant increase in bronchial wall area ( P<0.001) were observed subsequent to bronchoprovocation. After bronchodilation, the increase in cross-sectional area ( P<0.001) and the further increase in airway wall area ( P<0.01) were significant in all groups. In PC 20+ and PC 20− asthmatics, significant differences ( P<0.05) in PaO 2, >10 mmHg between baseline and provocation were observed. In healthy persons, the PaO 2 decrease was <10 mmHg ( P>0.05). After histamine provocation, the decrease in FEV 1 was measured in the PC 20+ group, whereas a <20% FEV 1 decrease was found in the PC 20− and the control groups, respectively. No significant correlations were observed between radiological data and the results of pulmonary function tests. Conclusions: HRCT demonstrated bronchial reactivity in hyperresponsive patients and, unexpectedly, in healthy subjects. The applied pulmonary function tests failed to characterize bronchial reactions in the healthy subjects. Based on these results, HRCT is a useful tool by which to achieve a comprehensive understanding of the pathophysiological processes in asthmatic patients.