Pulmonary tissue volume and blood flow as functions of body surface area and age.

We measured pulmonary tissue volume (Vt) and capillary blood flow (Qc) by rebreathing acetylene as the soluble gas in 94 male and 82 female patients with normal healthy lungs. We found that the standard deviation of Vt was a function of Vt and that the standard deviation of Qc was a function of Qc; logarithm transforms were used to prevent this. A significant correlation exists between log Vt and body surface area (BSA) and log Vt and vital capacity (VC). For both sets of regressions older subjects (greater than or equal to 40 years of age) exhibited greater variability about the regression line than younger subjects; therefore the 2 age groups of subjects were analyzed separately for tissue volume. We describe regression equations of log Vt vs. BSA or VC for younger male, younger female, older male, and older female patients. The normal limits by sex and age groups are also included. A significant correlation was found between log Qc, BSA, and age. Thus 2 equations, for male and female patients, are used to predict log Qc based on these 2 covariates.