Differential Forced Expiratory Spirograms

A Bronchospirometric Study

¹ Attending Physician, Municipal Tuberculosis Sanitarium; Associate Attending Physician, Michael Reese Hospital
² Professor of Medicine, The Chicago Medical School and Chief, Division of Thoracic Medicine, Mount Sinai Hospital
³ Chief Technician, Pulmonary Function Laboratory, Municipal Tuberculosis Sanitarium

1. Resistance to flow through the right and left lumens of Carlens bronchospirometry catheters was determined at flows above 120 liters per minute, using expired air. In 37F catheters, the difference in resistance between the two lumens remains low throughout the range tested.

2. Differential forced expiratory spirograms, made using 37F Carlens catheters, were studied in 19 patients with pulmonary disease, chiefly tuberculosis.

3. By comparing the split of the amount of air expired in the first one-half second with the split of the forced vital capacity, and by comparing the FEF_0.25% and FEF_25-50% for each lung, it was posible to estimate the relative degree of expiratory delay of the two lungs.

4. In 12 of the 19 cases, there was more expiratory delay in the smaller lung as compared with the larger; in two cases, there was much more expiratory delay in the smaller lung than the larger; and in five cases with relatively severe restriction, especially in the smaller lung, there seemed to be an equal amount of expiratory delay on the two sides.