Morphometry of pulmonary arteries from angiograms in chronic obstructive lung disease.

The application of morphometric techniques based on Strahler orders to the study of pulmonary angiograms is described. When the pulmonary arterial tree is ordered by Strahler's method, peripheral branches have the lowest orders and the main pulmonary artery the highest order. The mean diameter of vessels in each order can then be determined. Pulmonary angiograms were obtained from 16 patients, 10 of whom had chronic obstructive lung disease (COLD), the other six having normal angiograms. Six orders of branching were found in vessels of 1 mm diameter or greater, and a plot of log mean diameter versus order from the normal angiograms was linear. The mean diameters of orders 2, 3, and 4 (diameter 2 to 7 mm) from COLD patients were significantly reduced ((p less than 0.01) and the log mean diameter versus order plot was concave upwards. These changes were more marked when TLC was raised than when it was normal. Plots of diameters of vessels from zones of the lung in which the pathology was well advanced (as judged by radiological changes) showed even greater reduction in the middle orders. These changes are probably the result of stretching of vessels in emphysematous lesions and diminution of blood flow from loss of capillary bed.