Characteristics of pulmonary diffusing capacity in Japanese--aging effect on the sex and ethnic differences.

Abstract

Using 63 males aged from 9 to 68 years and 70 females aged from 9 to 56 years in good health, pulmonary diffusing capacity for CO (DL), diffusing capacity of the pulmonary capillary membrane (Dm), and pulmonary capillary blood volume (Vc) were measured in the sitting and supine positions and the age, sex, and ethnic differences in DL were studied. The subjects were divided into six groups by age as follows : Group I (9-12 years), Group 11 (16-25 years), Group III (26-35 years), Group IV (36-45 years), Group V (46-57 years), and Group VI (60-68 years). Group VI consisted of the males only. Regardless of age and sex, DL indicated a close relationship with the alveolar volume (VA'). The decreasing tendency of DL with age was more remarkable in the supine position than in the sitting position, and the degree of the decrease was greater in males than in females. As to Dm and Vc comprising DL, both showed an influence on age-related changes in DL in males, while such influence mainly due to Vc in females. Sex difference in pulmonary diffusing capacity per stature (DL/ST) was already observed in Group I, being greater in males. DL/ST was greater in males than in females throughout Groups I to IV, however, the sex difference disappeared in Group V. Pulmonary diffusing capacity per alveolar volume (DL/VA') which showed no sex difference in Groups I to IV, was greater in Group V of females than in that of males. The greater DL/ST in males seemed to be derived from a difference in alveolar volume per stature while the greater DL/ VA' in females seemed to be derived from a difference in age-related changes in pulmonary structure and function. Between the result of the present study and those of other reports on Caucasians (or those so considered), DL and DL/VA' corrected by age and stature were compared. As the result in the young adult groups of 11 and 111, either males or females showed smaller DL in Japanese than in Caucasians, but DL/VA' was nearly the same. The slopes of DL and DL/VA' against age were smaller in Japanese, for both males and females, thus in Group V for middle or old age, the difference in DL was smaller or even disappeared, while DL/VA' tended to be greater in Japanese.