COMPARISON OF PULMONARY-FUNCTION IN MALE SMOKERS AND NONSMOKERS

Abstract

Results of certain tests of pulmonary function, e.g., a questionnaire, single-breath N2 test of closing capacity, forced expiration and diffusing capacity, were significantly different in groups of male smokers and nonsmokers. The influence of age on these smoking-related changes of pulmonary function was evaluated. Some tests including number of symptoms; closing capacity, i.e., closing volume plus residual volume as a percentage of total lung capacity; residual volume as a percentage of total lung capacity; Phase III of the single-breath N2 test; and steady-state diffusing capacity (ml of CO/mm Hg.cntdot.min) revealed significant differences between adjusted mean smoker and nonsmoker values but did not reveal differences associated with age. Tests of forced expiration (1 s forced expiratory volume/vital capacity, reciprocal of the maximal mid-expiratory flow, maximal flow at 50% of vital capacity; and moments) revealed differences between smoker and nonsmoker means (adjusted and unadjusted), as well as increasing smoker-nonsmoker differences with increasing age. The 1st group of tests probably measured an all-or-none response that occurred with the onset of smoking and was not affected by duration of smoking. The 2nd group of tests probably measured the effects of continued smoking and indicated increasing abnormality associated with longer exposure (years of smoking). Tests showing age-related differences between smokers and non-smokers may reflect cumulative, irreversible changes in pulmonary function to a greater extent than tests that do not.