A Distribution Curve for Chronic Bronchitis.

In 1960, Reid described a method of quantitating the bronchial mucous gland hypertrophy that occurs in chronic bronchitis. She expressed the bronchial mucous gland size as a ratio of the bronchial mucous gland thickness to the thickness of the bronchial wall, as measured from the epithelial basement membrane to the inner perichondrium. This ratio was increased in chronic bronchitis, and there was no overlap between the ratios found in the lungs of patients with chronic bronchitis and those found in normal lungs, in a small series of cases. Thurlbeck, Angus, and Pare (1963), using this ratio (the Reid index), confirmed the mucous gland hypertrophy of chronic bronchitis but found that there was an overlap in the Reid index values obtained in bronchitics and in non-bronchitics. Restrepo and Heard (1963) measured the area of bronchial mucous glands as seen in histological sections, and found that the glands were increased in a group of patients with chronic bronchitis when compared with a group of non-bronchitics, but they also found an overlap between the groups. Reid's cases of bronchitis, however, appear to have had more severe disease than the bronchitics in the other two series: none had had bronchitis for less than five years and all had produced large quantities of sputum. Her 'controls' and 'bronchitics' may be from two extremes of a distribution curve. Since chronic bronchitis has been regarded as 'an excess of normal function' (Reid and Simon, 1959), an overlap in mucous gland size in bronchitics and non-bronchitics is perhaps to be anticipated. This has to be reconciled with the Ciba Guest Symposium (1959) definition of chronic bronchitis in which patients either suffer from chronic bronchitis or they do not, a vizwpoint which would be supported by finding little or no overlap between the two groups. Further light might be shed on this issue by investigating the distribution curves of the Reid index and of bronchial mucous gland thickness in a group of random cases. Such curves might settle the problem of overlap or non-overlap between groups of bronchitics and non-bronchitics. In addition to describing the distribution curves of the Reid index and bronchial mucous gland thickness in a random group of necropsies, the present work also refers to the relationship between the Reid index and bronchitis, smoking, and emphysema in a larger group of cases than has previously been reported.