One hundred patients with chronic airway obstruction, 50 in Chicago and 50 in London, were studied by standardized techniques in 1961. The results of the initial studies, previously reported, showed that the patients in the two cities were similar; using clinical and physiological criteria based on pathological studies, the patients were divided into three types—emphysematous type A, bronchial type B, and an indeterminate type X. The patients were studied again in succeeding years, 1962-65. During this time 26 died, 19 due to their respiratory disease; these 19 patients were initially more breathless, had a higher incidence of cor pulmonale, and had more severe airway obstruction and higher carbon dioxide pressures than the remainder. Type B patients (mortality 36%) had a worse prognosis than either type A (15%) or type X (12%). Of the measurements made, high carbon dioxide pressures were most closely related (p<0·001) to mortality.
During the period of follow-up about one-third of the patients who did not die became more short of breath and developed more severe airway obstruction and carbon dioxide retention: about 10% showed definite improvement in symptoms and pulmonary function. The F.E.V.1·0 declined on average by 46 ml./year, 4·8% of the initial value; V.C. declined by 120 ml./year, 4·0% of the initial value; mixed venous Pco2 increased 1 mm. Hg/year.
The changes that occurred during this time confirmed the previously reported similarity between the patients attending the two clinics. Although the incidence of bronchitic exacerbations was similar in the two cities, such illnesses in the London patients led to more frequent and more prolonged incapacity.
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