The Roentgen ray has made, perhaps, no more important revelation to the medical eye than that of the upper contour of the diaphragm. The position and movements of the diaphragm have received but little consideration in our modern systems of physical diagnosis, yet it is frequently demonstrated that the recognition of many thoracic and abdominal diseases is dependent on accurate data concerning the phrenic contour and position. It has been aptly said that the diaphragm is the vital barometer of the chest. And we may add that it is an important indicator of intra-abdominal conditions as well. The Roentgen ray has made possible a broader knowledge of the physiology and pathology of this organ.
A skilled diagnostician may, in a favorable subject, determine by percussion the level of the phrenic circumference and may in the same way roughly estimate the extent of the excursions of the diaphragm in forced respiration.
LANGE S. THE RELATIONS OF THE DIAPHRAGM AS REVEALED BY THE ROENTGEN RAY.. JAMA. 1908;L(9):673-676. doi:10.1001/jama.1908.25310350019001d