A Comparison of Expiratory and Inspiratory Flow Rates in Health and in Chronic Pulmonary Disease

More attention has been paid to the analysis of forced expiratory spirograms than to the inspiratory counterpart, probably because expiration is the more obvious difficulty in chronic obstructive respiratory disease. We believe that a greater understanding of the underlying abnormal mechanisms in the lungs can be obtained from a study of both inspiratory and expiratory spirograms. The method introduced by Danzig and Comroe and described by Comroe, Forster, Dubois, Briscoe, and Carlsen (1955) for the spirometric analysis of maximum expiratory and inspiratory flow rates has been chosen. It involves the measurement of the time taken to deliver a litre