Pulmonary parenchymal tissue volume in normal subjects. The effect of age and sex.

Abstract

Pulmonary parenchymal tissue volume (Vt) and pulmonary capillary blood flow were determined by the acetylene-inhalation technique of Cander and Forster in 66 normal subjects (31 male and 35 female subjects) ages 8 to 66 years. In subjects under the age of 20 years, values for Vt, when factored by alveolar volume (VA) to correct for differences in body size, were essentially identical in both male and female subjects (0.248 +/- 0.039 in male subjects and 0.242 +/- 0.079 in female subjects). In subjects between the ages of 21 and 40 years, Vt/Va was significantly lower in men than women, 0.125 +/- 0.057 vs 0.193 +/- 0.046 (P less than 0.001), respectively. In subjects over the age of 41 years, although Vt/VA increased, there was no significant difference between the sexes; ie, Vt/VA decreased with advancing age up to the age of 35 years (more so in male than female subjects) and then increased back to pubertal values. The reason for the intersex changes is a greater increase of VA in male than female subjects for the same Vt. The reasons for the increase in Vt/VA in subjects over the age of 35 years are obscure.