Continuous measurement of core body temperature in preterm infants

We tested a transcutaneous core temperature sensor using a method that reli es on the principle of zero heat flow. We tested the hypothesis that transc utaneous and rectal temperatures would track within 0.3 degreesC of each ot her for >90% of the time. A thermistor was placed between the infant's abdo men or back and the incubator's or radiant warmer's mattress, or within the axilla, attached to the skin with a loam adhesive disk insulator. Thirty p reterm infants were either placed on their abdomens or backs in a convectiv e incubator or under a radiant warmer, and continuous transcutaneous and re ctal temperatures were measured for 1 hour. There were no significant diffe rences between abdominal and core temperatures or between axillary and core temperatures measured in double-walled convective incubators or in radiant warmers. The rectal-abdominal temperature difference was significantly les s than the rectal-axillary difference (p < 0.02) in convective incubators, but not when the infant was placed prone under radiant warmers (p = 0.27). Transcutaneous thermometry is reliable for monitoring core body temperature as indicated by rectal temperature in stable preterm infants in a convecti ve incubator.