Radiographic and Plethysmographic Determination of Total Lung Capacity1

Journal/Book: Reprinted from RADIOLOGY Vol. 86 No. 1 Pages 7-14 January 1966. 1966;

Abstract: HERBERT M. LOYD M.D. 2 S. TIMOTHY STRING B.A. 3 and ARTHUR B. DuBOIS 4 M.D. 1 From the Department of Physiology Division of Graduate Medicine and the Department of Radiology University of Pennsylvania School of Medicine Philadelphia Penna. Accepted for publication in July 1965. This work was supported in part by a gram (H4797) from the U.S.P.H.S. 2 This project was carried out during a Senior Clinical Traineeship (CST-164-64) from the Division of Chronic Diseases (Cancer Control) U.S.P.H.S. 3 This investigator was supported in part by General Research Support Grant No. 1-501-05115-01 from the Division of Research Facilities and Resources and by Training Grant No. 5T5GM-4-08 from the Division of General Medical Sciences both from the U.S.P.H.S. 4 Research Career Awardee of U.S.P.H.S. SUMMARY 1. The total lung capacities (TLC) of 50 subjects including both normal and pathological states were determined by radiographic and plethysmographic methods. 2. The radiographic method as originally described by Barnhard et al. was reviewed and modified in the light of new physiological data concerning pulmonary tissue volume and pulmonary blood volume. A nomogram was devised relating these data to height and weight. The method of calculation was simplified. The resulting modification was tested against the original method and found to produce data of equal validity when compared to plethysmographic data. 3. A statistical analysis showed that the radiographic method was a reliable predictor of the plethysmographically deter mined TLC (r = 0.966 p = <0.001). The overall mean difference (radiographic TLC-plethysmographic TLC) was -62 ml S.D. 532 ml. The mean per cent difference [(mean difference/mean plethysmographic TLC) X 100 ] was -1.5 per cent S.D. 9.7 per cent. 4. The reproducibility of the x-ray method was tested by independently re-measuring ten sets of radiographs. Excellent agreement between the two measurements resulted (mean difference -112 ml S.D. 141 ml). 5. The method was taught to a nurse-technician who was able to independently produce measurements of the TLC which varied insignificantly from those of the radiologist (mean difference 8 ml and S.D. 144 ml). 6. It was concluded that the radiographic method produced reliable measurements of the total lung capacity with an acceptably small error in both diseased and normal chests. ___MH

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