FACTORS AFFECTING INDIRECT DETERMINATION OF SYSTOLIC BLOOD PRESSURE OF RATS.

Abstract Several factors which affect the measurement of systolic blood pressure of the unanesthetized rat were studied with the microphonic manometer technique. Variation of the width of rubber tubing in the metal occluding cuff results in wide variation in the measurement of systolic blood pressure, as does the position of the occluding cuff on the tail. The more distal the placement of the cuff on the tail, the lower the measured blood pressure; for reproducible results the cuff must be placed in the same position on the tail for all measurements. The procedure used for heating the rat in preparation for blood pressure measurement also must be standardized. Under the conditions of these experiments, an average rise of colonic temperature of 0.8 °C. was found to be necessary before sounds were audible in the tails of the rats tested. The rat responded initially to the stress of blood pressure measurement by a slight increase in blood pressure, but after 4 minutes, blood pressure attained a stable level. Attention to these factors will help decrease variability of indirect blood pressure measurement by this technique.