Studies of Total Pulmonary Capacity and Its Sub-divisions. I. Normal, Absolute and Relative Values.

In the investigation of the symptom, dyspnea, by physiological methods studies of the pulmonary mechanisms have lagged behind those of other mechanisnis involved. In most clinics the measurement of the vital capacity is frequently made, but rarely in conjunction with measurements of total pulmonary air and its subdivisions. No complete understanding of the problem can be attained without a complete study of the functions of the lungs in addition to those of the blood and the circulatory organs. The studies to be reported here were commenced as a preliminary to an investigation of the functional disability caused by various types of fibrosis of the lungs, particularly the pneumonoconioses. At the outset it was discovered that data regarding lung capacity were available in only a small number of normal individuals, so small that no standards of normality could be established for comparison with measurements to be made in pathological conditions. We will not attempt to make a historical review of the methods used in the determination of the lung volume and its subdivisions. A complete presentation of the subject, from this point of view, has been published very recently by Christie (4). We may mention that probably three factors have largely been responsible for hesitancy in accepting this procedure as a useful tool in clinical medicine: unreliability of the methods used; difficulty of using complicated methods in dealing with very sick patients, and finally lack of normal standards for comparative purposes. The first two drawbacks have been solved by the methods described by Van Slyke and Binger (12), and lately by Christie (4). The present study was undertaken in an attempt to furnish some information regarding the normal values of the pulmonary air and its subdivisions, to appreciate the character of its variations, to establish a method which will permit the prediction of normal values in a given case, and finally to apply the information gained from the normal observations to the study of cases of