Variations in the Pulmonary Capillary Blood Volume and Membrane Diffusion Component in Health and Disease*

This is the authors' abstract. We don't add key points for this paper.

Forster, Roughton and their colleagues (1, 2) have reported a method of subdividing the com- ponents of the pulmonary diffusing capacity by measurement of the apparent diffusing capacity at different alveolar oxygen tensions.This development followed preparatory work by the same authors (3, 4) in which the kinetic factors in- volved in CO and hemoglobin combination were reported.The principles underlying the measure- ments have been fully discussed by Forster in a recent review (5).Lewis, Lin, Noe and Komisaruk (6) reported on the measurement of pulmonary capillary blood volume in normal subjects, using the single breath method of determining the pulmonary diffusing capacity.They found average values of 65 ml for the pulmonary capillary blood volume at rest and 98 ml CO per minute per mm Hg for the membrane diffusion component.In four subjects both of these quantities increased somewhat dur- ing exercise.They did not report any results on patients.McNeill, Rankin and Forster (7), using a similar technique of measuring the pulmonary diffusing capacity by a single breath method, found similar values at rest for the pulmonary capillary blood volume, but a lower value for the membrane component, which was about 63.5 ml CO per minute per mm Hg in normal subjects at rest.These authors reported the results of this measurement in five patients with various types of pulmonary fibrosis, two with pulmonary hypertension, two with pulmonary congestion, and three with chronic obstructive emphysema.The most significant findings were the decrease in membrane diffusion component ib patients with pulmonary fibrosis, and the increase generally found in pul- monary capillary blood volume in patients with in- creased pressure in the lesser circulation.