Document Type


Date of Award

Winter 1994

Degree Name

Master of Science in Biomedical Engineering - (M.S.)


Biomedical Engineering Committee

First Advisor

Peter Engler

Second Advisor

David S. Kristol

Third Advisor

Arthur B. Ritter


Weakness of inspiratory muscles is a major cause of respiratory failure. There are many clinical circumstances in which it may occur. The diaphragm is a major respiratory muscle. It has been difficult to quantify its shape, curvature and length.

To solve this question, a three dimensional diaphragm equation was derived on the, assumption that the diaphragm is only attached at its periphery to the rib cage and the abdomen is filled with fluid. Computer programs were developed to fit the equation to the diaphragm contours obtained from plane X rays.

The results indicate that the ratio of transdiaphragmatic pressure to the surface tension of the diaphragm is relatively independent of lung volume, which supports the previous finding that the force-length
relation is a more important geometric factor in diaphragm mechanics. Comparing the diaphragm contour of the normal person to two patients with ascites, it is suggested that the ascites patients have higher transdiaphragmatic pressure than normal patients.



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