A New Simple Method for Indirect Determination of Blood Pressure in the Rat.∗

Summary A new indirect method for measuring systolic pressure in the rat's tail has been described. It depends upon the visual recognition of pulsatile vibrations which are obliterated by inflating of the cuff to a pressure exceeding the systolic pressure. As the cuff is slowly deflated the vibratory motion reappears, the amplitude of the vibration increasing to a maximum as the cuff pressure approaches zero. The reappearance of the persistent vibration is taken as the systolic endpoint. The accuracy of the method was checked by comparing measurements with values recorded with the microphonic manometer, blood flow after amputating the tip of the tail, and in some instances by direct mean aortic pressure measurements in normal and hypertensive rats. No data were obtained in hypotensive animals. The advantages and limitations of the visual method have been discussed. The effect of cuff size and preliminary warming of the whole animal or only the tail have been studied.