Single breath diffusing capacity in a representative sample of the population of Michigan, a large industrial state.

Abstract

Many predictive equations for the single breath CO diffusing capacity (DlCOsb) are based on small, selected populations and do not account for the effect of cigarette smoking. We performed this test on 582 white adults who were part of a stratified random sample of the population of Michigan, a large industrial state. Data on 511 subjects who had full clinical information and normal hemoglobin concentration provided prediction equations and lower 95% limits for current cigarette smokers, ex-smokers, and nonsmokers. These are the first equations, obtained by sampling the general population of an entire state. Significant differences in the level of DlCOsb were found between smoking categories. To obtain information on the frequency with which DlCOsb would be reported as abnormal in a general population, the test results for all 582 subjects were compared with reference values. Use of equations that do not take, smoking into account classified 30% of the male and 28% of the female smokers as “abnormal,” whe...