Reliability of Rectal Temperatures as an Index of Internal Body Temperature

Abstract

Studies were made to determine whether or not the distance from the anus at which rectal temps. are recorded is critical beyond a depth of 2-3 inches. In 8 men under a variety of conditions of heat balance and inbalance, temps. near the tip of a flexible catheter inserted 8 inches through the external anal sphincter were in almost every instance lower than temps. recorded simultaneously at intermediate points along the catheter. Deviations observed varied from 0.1[degree] to 1.5[degree] F and were greatest in individuals whose body temps. were falling. X-ray films showed that the tip of the catheter in a majority of instances lay near the posterolateral wall of the pelvis. The exptl. data suggested that cooled blood from the surface of the body passing through veins in the pelvic wall adjacent to the terminal portion of the catheter was responsible for the deviations observed. The meaningfulness of "an index of deep body temp." was discussed, and the importance of accurate positioning of devices for recording internal temps. was stressed. A rigid plastic catheter was described which permits reproducible positioning of a thermocouple against the rectal mucosa, sufficiently anterior in the pelvic cavity to be beyond the direct influence of the temp. of blood in the large vessels of the posterior pelvic wall.