Artifacts in the measurement of skin temperature under infant radiant warmers.

All skin temperature probes measure, to some extent, operative temperature as well as skin temperature, and thus artifactually measure a temperature different from true skin temperature. To assess the magnitude and direction of these artifacts in the measurement of surface temperature in radiant warmers designed for human infants, the artifactual deviation of measured surface temperatures from mean surface temperature was determined under a short-wavelength warmer and a long-wavelength radiant warmer, using a copper ball as an experimental model. The measurements were made using both a disk-shaped thermistor and a tubular thermistor. All measurements were made near the top of the hemisphere of the ball facing the heating element of the warmer. In all cases, the average artifact was negative. That is, even on the surface of the ball near the radiant heat source, the surface temperature probes recorded an artifactually low temperature. In the analogous clinical setting, a somewhat larger negative artifact would be expected.