Alveolar surface area (Sa) may be derived from measurements of total lung capacity (TLC) and mean linear intercept (Lm), an estimate of average airspace size. Because the index of pulmonary distensibility, K, is a function of Lm, we were able to derive Lm from ln K using their respective age regressions and estimated Sa in 147 healthy subjects. K was obtained from exponential analysis of static pressure-volume data. TLC was measured in a body plethysmograph. As an estimate of airspace size, the value used for Lm was shown to be appropriate for the air-inflated lung at TLC. In 95 men (mean age 40 +/- 16 SD years), Sa was 118 (SD 22) m2 and in 52 women (mean age 38 +/- 17 SD years) it was 91 (SD 18) m2 and Sa decreased with age (P less than 0.001). In a morphometric study, Thurlbeck (Am. Rev. Respir. Dis. 95: 765-773, 1967) obtained smaller values for Sa (owing to the use of a smaller lung volume) and a similar decrease in Sa with age as that found here. Providing a standardised methodology is used for measurement of K, the present method allows a reasonable estimate of Sa to be obtained during life.

Adult↗

PubMedDate not supplied

Pulmonary distensibility and ventilatory function in smokers.

To define the increase in pulmonary distensibility preceding the development of emphysema, we studied 101 cigarette-smoking volunteers, 73 males and 28 females between the ages of 18 yr and 60 yr (mean 42 yr), who were not disabled. A single exponential function fitted to deflation static pressure-volume data gave the exponent K, an index of distensibility. Total lung capacity (TLC) was measured with a body plethysmograph. Values for VC, FEV1 and mid-expiratory flow were only slightly less than values obtained in nonsmokers. K was increased in smokers and increased with age at a greater rate than in nonsmokers, but smokers were unevenly affected. In relation to height, TLC was increased in male smokers and the increase was directly related to the increase in K. The findings show that increased pulmonary distensibility may be identified in smokers without airway obstruction. Because K is directly related to the size of peripheral airspaces, increased pulmonary distensibility in smokers implies an increase in the size of airspaces caused by an action of cigarette smoke, and taking place in asymptomatic subjects.

Adolescent↗