Fractional carbon monoxide uptake in an employed population

Abstract

Minnesota 55455, USA Stebbings, J. H. (1974). Thorax, 29,[505][506][507][508][509][510] The fractional carbon monoxide uptake has been suggested as a useful index of pulmonary diffusing capacity in clinical evaluations, in respiratory screening programmes, and in epidemiological studies (Bates, Macklem, and Christie, 1971;Lacoste, 1971Lacoste, , 1972. The study reported on here was designed to evaluate this, to establish normal values, and to determine the effects of cigarette smoking. SUBJECTSA survey of the prevalence of chronic respiratory disease was carried out in New York City Transit Authority workers between November 1961 and August 1963. A total of 7,974 workers with job titles of motorman, surface line operator, and surface line dispatcher were studied. Details of the survey and results are given by Densen, Jones, Bass, and Breuer (1967), Densen et al. (1969), andStebbings (1972;.From the workers surveyed approximately 2,000 were selected for a five-year follow-up study which was carried out between June 1964 and June 1969. Criteria for selection for the follow-up study were complex and depended upon the smoking histories, ages, one-second forced expiratory volumes, and symptoms of the indivi- duals (Densen, Jones, and Bass, 1965). The majority of individuals in the follow-up study may be considered as a random sample of the surveyed transit workers; among the remainder there was an excess of both nonsmokers and heavy smokers, and among smokers there was an excess of individuals with either high or low one-second forced expiratory volumes or severe or absent respiratory symptoms. An analysis of the effect of lack of random selection of the follow-up population upon the results of this paper will be presented below. The fractional carbon monoxide uptake was measured at only one of the three clinic sites in Brooklyn and Manhattan utilized in the follow-up study. A total of 913 individuals had at least one fractional CO uptake test, but it is not known what fraction of the respondents attending the one clinic this represents. For all three clinics combined, 89-8 % of the defined follow-up population received at least one examination. The analyses presented in this paper are based on these 913 individuals, or upon a subset of 581 of the 913 who had two or more tests of their fractional CO uptake during the five-year study period.METHODS Respondents were interviewed and examined in most cases immediately following their annual (if over 50 years of age) or biannual (if younger) Transit Authority physical examination. An intensive effort was made to induce retirees, ex-employees, and those not scheduled 505