Abstract
Localized pressure applied to muscle or nerve is commonly employed to depress, or abolish function in these tissues. In the present experiments our purpose is to observe the effects of high pressure upon the heart when applied in a manner so as to give equal compression throughout the organ.
A special compression chamber has been constructed which is capable of withstanding pressures of 80 atmospheres, and is large enough to admit a small optically recording membrane manometer with a frog, or turtle heart attached. The heart and optical manometer are completely filled with Ringer's solution and mounted in the compression chamber which is also completely filled with the solution. In this manner the heart is surrounded inside and out with the Ringer's solution, and the pressure when applied to the heart is through this liquid medium.
Since the source of pressure in our experiments is nitrogen gas, provision is made also, for the liquid system of the compression chamber to be continuous through a small bore tube to a reservoir of about 100 cc. capacity. The reservoir is partly filled with Ringer's solution, and from the top of it a small tube leads to a high pressure nitrogen tank. In one end of the compression chamber a small window, backed with heavy plate glass, provides a way for recording the movements of the manometer system produced by the contractions of the heart.
When pressure of about 60 atmospheres is applied to a normal beating heart, an increase of nearly twofold is produced immediately in the amplitude of its contractims. The maximum augmenting action of compression is not shown in the first cycle after the onset of pressure, but usually it requires from 3 to 5 cycles for the full effect to take place.
Get full access to this article
View all access options for this article.