Cigarette smoking and density-dependence of maximal expiratory flow in asymptomatic men.

The influence of cigarette smoking on helium response of maximal expiratory flows was studied in 26 asymptomatic male smokers 35 to 55 yr of age. The subjects had smoked 18.0 +/- 10.6 cigarettes/day for 19.2 +/- 6.7 yr (total consumption, 16.1 +/- 9.8 pack/yr) and were selected because they had no history of cardiopulmonary disease, and their physical examination, chest roentgenogram, and spirographic results were normal. Maximal expiratory flow (at the mouth)-volume curves were recorded while the subjects breathed air and a mixture of an 80% helium and 20% oxygen; the helium response (delta He) was expressed as the difference between maximal expiratory flow with helium and maximal expiratory flow with air at 50 and 25% of vital capacity. Current cigarette consumption and total tobacco use were not related to either delta He50% or delta He25%. However, maximal expiratory flows with air and helium were significantly related to current cigarette consumption (for cigarettes/day versus Vmax50% air, r = - 0.587 and p < 0.01; for cigarettes/day versus Vmax25% He+O2, r = - 0.594 and p <0.01) or to lifetime tobacco consumption (for packyr versus Vmax50% air, r = - 0.39 and p < 0.05; for pack-yr versus Vmax25% He + O2, r = - 0.643 and p < 0.001). The result were compatible with a tobacco effect on both central and peripheral airways: increase in upstream resistance due to peripheral airway obstruction, and slight downstream displacement of equal pressure points due to increase in central airway resistance. We concluded that the helium response of maximal expiratory flows is less sensitive than maximal expiratory flows with air in detecting an early effect of tobacco in asymptomatic cigarette smokers.