COMPARISON OF DISTAL ESOPHAGEAL TEMPERATURE WITH DEEP AND TRACHEAL TEMPERATURES

Purpose: To compare distal oesophageal (reference) temperature with '' deep-sternal,'' ''deep-forehead,'' and tracheal temperatures, establis hing the accuracy and precision of each. Methods: We studied 20 patien ts undergoing general anaesthesia for gynaecological surgery, Their lu ngs were mechanically ventilated with a circle system, at a fresh-gas flow rate of 6 L.min(-1). Respiratory gases were not warmed or humidif ied. Tracheal temperatures were recorded from a Trachelon(R) tube inse rted approximate to 21 cm. Deep-body temperatures were measured at the sternum and forehead using a Coretemp(R) thermometer. The principle o f the method is to null thermal flux through a cutaneous disk; thus ob literating thermal gradients between the sides of the disk, skin surfa ce, and subcutaneous tissues. Distal oesophageal temperatures were mea sured from thermocouples incorporated into oesophageal stethoscopes. T racheal and deep-tissue temperatures were compared with oesophageal te mperature using regression and Bland and Altman analyses. Results: Tra cheal, sternal, and forehead temperatures correlated similarly with di stal oesophageal temperature, correlation coefficients (r(2)) being 0. 7 in each case. The offset (oesophageal temperature minus study site) was considerably larger for tracheal temperature (0.7 degrees C) than for the other sites (0.2 degrees C). However, the precision was-only 0 .3 degrees C at each site, Conclusion: Our data suggest that tracheal temperatures may not be an adequate substitute for conventional core-t emperature monitoring sites. In contrast, the accuracy and precision o f deep-tissue temperature monitoring at the sternum and forehead was s ufficient for clinical use.