Abstract
After an examination of the methods in vogue for the determination of the pressure of the venous blood and after a consideration of the difficulties involved in their use, we have succeeded in measuring the venous pressure by inserting a needle into the median basilic vein and observing the rise of the blood in a vertical tube. This simple and direct procedure was first used in 1735 by Stephen Hales, a British clergyman, who inserted tubes into the crural artery and the jugular vein of a mare and observed both arterial and venous pressures. The method has since been neglected, 2 other procedures being now in general use. The indirect, tambour method of Eyster and Hooker 1 is effective only when the veins are distinctly visible. It is subject to large personal error and the time required for an observation is appreciably longer. The direct method of Moritz and Tabora 2 is complicated by the use of an additional fluid, e. g., salt solution. Moreover the results do not appear to be entirely reliable.
The apparatus∗ which we have used, Fig. 1, is an L-shaped pyrex glass tube, ground at the horizontal end to fit an 18 gauge hypodermic needle. The vertical portion of the tube has an internal diameter of 4 mm. and is 30 cm. in length. The readings are taken with the help of a celluloid metric scale which is fastened to the vertical portion of the tube by means of spring clips. The capillary rise of the blood in such a tube is approximately 0.5 cm. and may cause a positive error of this magnitude in the determination. If the pressure is to be related to a column of water, the specific gravity of the blood will introduce an error in the opposite direction.
Get full access to this article
View all access options for this article.