BRONCHIAL CLEARANCE OF DTPA IS INCREASED IN ACUTE ASTHMA BUT NOT IN CHRONIC ASTHMA

To investigate bronchial permeability in asthma, we measured the bronchial clearance of In-113m-DTPA in seven asthmatics during and after an acute attack of asthma, seven asthmatics with chronic airflow limitation, and seven asthmatics without airflow limitation but with bronchial hyperresponsiveness to methacholine. We compared these results with those from seven normal subjects, seven patients with chronic bronchitis and bronchial infection, and seven patients with emphysema. An aerosol of In-113m-DTPA was produced with a spinning disc to ensure a predominantly bronchial deposition of inhaled particles (6.3-mu-m MMAD). Radioactivity over the chest was recorded with a gamma-camera for 10 min after the subject inhaled the aerosol. Central regions of interest were selected, and the logarithm of the radioactivity was plotted against time; bronchial clearance of In-113m-DTPA was calculated as the negative slope of the regression line. Clearance was substantially higher in asthmatics during their acute attacks than in all other groups (p < 0.0001), and it decreased toward normal levels after recovery from the acute episode. The bronchial clearance of In-113m-DTPA in all other groups did not differ from normal. We conclude that the bronchial clearance of In-113m-DTPA is increased In asthmatics during attacks of asthma but in the stable state is not related either to bronchial hyperresponsiveness or to airflow limitation. Our findings are best explained by an increase in permeability of the bronchial mucosa of asthmatics during acute attacks.