Relationship between bronchial and arterial diameters in normal human lungs.

In order to find an objective method for measuring narrowing of small airways, eight lungs from four people without lung disease were inflated and fixed at 25 cm of water pressure. Eight to nine blocks were taken at random from each of six parasaggital slices from each lung, sectioned, and stained. The size of the bronchioles (airways without cartilage) in relation to their accompanying arteries was determined. The internal bronchiolar diameter was compared with three different arterial diameters (the internal, external medial, and external adventitial). The ratio of the internal bronchiolar diameter to the external adventitial arterial diameter was constant between lungs (0.62 +/- 0.02) and independent of the method of inflation or the position within the lungs. This ratio may provide a useful index of bronchiolar narrowing in disease.