Determination of pulmonary parenchymal tissue volume and pulmonary capillary blood flow in man

Abstract

The rates of disappearance of SF6, N2O, C2H2, diethyl ether and acetone from alveolar air during breath holding, following a single deep inspiration of a mixture containing one of these gases and about 15% helium, was studied in five normal seated subjects. SF6 is so insoluble that no significant change in its concentration relative to helium was found. Ether and acetone are so soluble that they dissolve in the tissues around the respiratory dead space during inspiration and evaporate during expiration, contaminating the expired alveolar gas to such an extent that the exchange of these gases cannot be properly measured at the alveolar level. N2O and C2H2 showed a) a rapid (less than 1.5 sec.) initial fall in relative alveolar concentration and b) a subsequent more gradual decrease; a) presumably results from the solution of the foreign gas in the pulmonary parenchymal tissues and can be used to calculate the pulmonary parenchymal tissue volume (Vt); b) can be used to calculate the pulmonary capillary blood flow (Qc), provided observations are not extended beyond 21 sec. The average values obtained were 3.31 l/min/m2 and 606 ml for Qc and Vt, respectively. Submitted on December 4, 1958