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.