LUNG ELASTICITY IN REGIONAL AND DIFFUSE PULMONARY FIBROSIS

Static deflation air and saline pressure-volume (PV) curves were performed on 5 normal excised baboon lungs, 4 with radiation-induced upper lobe fibrosis, and 2 with diffuse bleomycin-induced fibrosis. Curves were compared visually and using half-inflation pressure (h). When plotted as percent of observed vital capacity vs. transpulmonary pressure, the radiation-associated curves were similar in shape to control curves. Also, h values were not significantly different between the two groups. The bleomycin-associated curves, however, were shifted rightward and exhibited increased h values. PV curves were correlated with connective tissue data. Elastin concentration was increased in the irradiated upper lobes through loss of associated constituents. Elastin accumulated in the lower lobes of the irradiated animals through compensatory growth and in the bleomycin associated lungs through excessive production. Collagen followed a similar but less dramatic trend. We conclude connective tissue accumulation may not lead to rightward shifted PV curves if accumulation is present in relatively noninflatable lung units, or as part of compensatory lung growth.