Document bBqmqx37M5XkvxX9Ng09bk5ak

728 Asbestosis, Bronchogenic Carcinoma--Isselbacher et al. poisoning who usually show a favorable re sponse to steroid therapy.29 Two further aspects of this case merit more detailed consideration and analysis: (1) the pulmonary function and cardiac catheterization studies; and (2) the significance of the superim posed bronchogenic carcinoma. PULMONARY FUNCTION AND CARDIAC CATHETERIZATION STUDIES Table 1 indicates, as one might expect, that the patient had a reduction in vital and maxi mum breathing capacities. However, the finding of an alveolar-arterial oxygen gradient of 27 mm. Hg demonstrates that one of the dis turbances in pulmonary function was a defect in the diffusion of oxygen from the alveoli of the lungs to the capillaries. This corresponds to the syndrome of "alveolar-capillary block" de scribed by Baldwin, Cournand and Richards31'92 and again by Austrian et al." This diffusion defect is not surprising when one recalls the fibrosis about the alveoli, alveolar ducts, capil laries and bronchioles that occurs in asbestosis. In order for the patient to maintain a near normal arterial oxygen saturation, a high alveolar oxygen was necessary; and this ap parently was accomplished in part by hyper ventilation. The patient had an average respiratory rate of 40 per minute at rest. This compensatory mechanism apparently was not adequate during stress or exercise for under those conditions the arterial oxygen saturation fell. There was a considerable degree of pulmo nary hypertension and, as in the cases of pulmo nary fibrosis studied by Cournand and his associates, a rise in the pulmonary artery pressure occurred with exercise. (Table 11.) The partial pressure of carbon dioxide in the blood (36 mm. Hg) was low normal rather than ele vated. Had there been a defect in alveolar ventilation, the pCC>2 would probably have been higher. As Amot emphasized in discussing this case16 carbon dioxide is not impaired in its transfer from the blood to the alveoli because of its great diffusion capacity. This speed of diffusion plus the increased alveolar ventilation no doubt accounted for the lowered pCC>2 value. ASBESTOSIS AND CARCINOMA OF THE LUNO The association of asbestosis and carcinoma of the lung has been mentioned frequently in the literature. 1-9,94~63 Heretofore some authors have believed that the cases were too few in number to be of significance; others, especially Vorwald and Karr, have stated that "inhaled dusts, except those containing recognized carci nogenic substances (as radium and tar) cannot in general be considered as etiologic factors in the development of primary pulmonary carci- Table m INCIDENCE OF ASBESTOSIS AND CARCINOMA OF LUNG Author No. of No. Due to Deaths with Cancer of Asbestosis Lung Inci dence <%) Merewether1........... Wedler44.................. Wyers*...................... Lynch, Cannon47. . Gloyne*.................... Total......................... 235 92 115 40 121 603 31 13.2 15 16.3 17 14.8 3 7.5 17 14.1 83 13.8 noma."4 Our conclusion at present is in favor of the concept that the association of broncho genic carcinoma with asbestosis is more than coincidence. That there is a significant incidence of bronchogenic carcinoma in asbestosis is apparent from Table in. Merewether has cited the largest series--of 235 cases of asbestosis there were thirty-one with bronchogenic carcinoma, or 13.2 per cent.1 An average of the five analyses recorded in the literature is 13.8 per cent. This is considerably higher than the incidence of lung carcinoma in routine necropsies, which in a comparable period (1935-1948) ranged from 0.8 to 2.4 per cent.9'47-64 In contrast to asbestosis the incidence of bronchogenic carcinoma in silicosis as recorded in the two largest series has been similar to what might be expected in the general popula tion. The data compiled by Merewether1 and the Miner's Phthisis Medical Bureau of South Africa66 are based on a total of 6,884 and 1,438 autopsied cases of silicosis respectively, and disclose an incidence of lung carcinoma of 1.32 and 0.70 per cent. Vorwald and Karr found two lung carcinomas in 136 silicotics (1.47 per cent). Klotz66 noted an incidence of 8 per cent, but his series of fifty cases does not seem large enough to be statistically significant. However Gloyne9 in reviewing necropsy material from 1929 to 1949 (796 cases) also described the surprisingly high incidence of lung carcinoma in silicosis of 6.9 per cent, and 7.7 per cent in AMERICAN JOURNAL OF MEDICINE