Lung permeability in adult obliterative bronchiolitis

Abstract

There is histopathological evidence that, in certain inflammatory disorders involving the smaller airways, extension of the inflammatory process may occur distally into the respiratory bronchioles, alveolar ducts and alveoli (1,2). The objective of this study was to perform a non-invasive evaluation of the possible involvement of gas exchanging regions of the lung in obliterative bronchiolitis presenting with severe airways obstruction. We measured the clearance of technetium 99m-labelled diethylene triamine penta-acetate (99m Tc-DTPA) with time from the lungs to the blood, in 11 normal, non-smoking subjects (mean age 30 years), ten non-smoking patients with cryptogenic fibrosing alveolitis (CFA, mean age 57 years) and ten patients who were non-smokers with obliterative bronchiolitis (mean age 51 years). There was a substantial increase in clearance in patients with CFA, (mean T1/2 19.9 min), compared with either patients with obliterative bronchiolitis (mean T1/2 52.2 min; mean difference 32.3; 95% confidence intervals (CI) 18.40; P less than 0.001) or normal controls (mean T1/2 84.3; mean difference 64.4; 95% CI 55, 74; P less than 0.001). Clearance was also significantly faster in patients with obliterative bronchiolitis than in normal controls (mean difference 32.1; 95% CI 18.48; P less than 0.001). Peripheral deposition of 99m Tc-DTPA was uniform in normal subjects and patients with CFA, but patchy in patients with obliterative bronchiolitis, possibly resulting from altered patterns of ventilation associated with patchy distribution of bronchiolitis within affected lungs. Increased clearance of 99m Tc-DTPA from the lungs in these patients suggests that subtle derangement of the alveolar-capillary membrane occurs in adult obliterative bronchiolitis.