A NONINVASIVE TRANSCUTANEOUS ALTERNATIVE TO RECTAL THERMOMETRY FOR CONTINUOUS MEASUREMENT OF CORE TEMPERATURE IN THE PIGLET

Deep body temperature is an important and accepted index of health sta tus in newborn infants. There are no easily used accurate methods for continuous deep body temperature measurements. Oral and tympanic membr ane temperatures correlate well with rectal temperature but are not ea sily adapted to continuous measurement. We devised a noninvasive trans cutaneous temperature sensor for continuous deep body temperature meas urement that relies on the principle that, under steady state conditio ns, the temperature at the thermally insulated surface of a warm body, i.e. a zero heat loss surface, will be in equilibrium with the warmes t part of the body. We used a standard clinical temperature probe plac ed between the skin and the mattress and attached to the skin with a f oam adhesive disk. We used standard skin temperature probe attachment disks, which are also designed to provide thermal insulation to the sk in temperature probe. We tested the hypothesis that this transcutaneou s temperature would track body temperature as indicated by rectal temp erature. In six anesthetized (pentobarbital) newborn piglets (1600 +/- 200 g) placed on their abdomen in a convectively warmed infant incuba tor, we measured continuously the following temperatures for 5 h: tran scutaneous over lower and upper abdomen, brown fat, rectal, and descen ding aorta. To examine the influence of environment, we varied the inc ubator air temperature between 32-degrees and 36-degrees-C. Both trans cutaneous temperatures tracked the rectal temperature, within 0.2-degr ees-C for transcutaneous over lower abdomen and within 0.3-degrees-C f or transcutaneous over upper abdomen. Aortic artery temperature was al ways lower than rectal. We conclude that transcutaneous temperature ha s the potential to be used reliably as a noninvasive replacement for c ontinuous rectal temperature monitoring.