A Simplified Morphometric Method for Estimating Diffusing Capacity in Normal and Emphysematous Human Lungs1,2

Abstract

A simple method was developed for estimating pulmonary diffusing capacity by morphometry using light microscopic preparations of normal and diseased human lungs. It should be particularly useful in studying emphysematous lungs obtained at autopsy in view of a structure-function correlation. The main determinants of morphometric estimations of diffusing capacity of the lung are the alveolar surface area and the capillary loading, estimated by the capillary surface and volume. Alveolar surface area can be easily measured on thin sections by the intersection counting method. a procedure is given for estimating capillary surface and capillary volume from a simple counting measurement performed on capillary networks observed in thicker paraffin sections. Introducing a few assumptions based on indirect estimations or subjective judgment of the specimen (relative changes in barrier thickness), a formula can be used to arrive at an estimate of diffusing capacity of the lung, which should be compared to physiologic determinations of diffusing capacity obtained during exercise. a nomogram is provided for rapid evaluation of the data and prediction of normal values.