Temperature measurement: comparison of non-invasive methods used in adult critical care

Aims: To assess accuracy and reliability of two non-invasive methods, the chemical (Tempa.DOT angstrom) and tympanic thermometer (Genius(TM) First Temp M3000 angstrom), against the gold standard pulmonary artery catheter, and to determine the clinical significance of any temperature discrepancy using an expert panel. Background: There is continued debate surrounding the use of tympanic thermometry in clinical practice. Design: Prospective study. Methods: A total of 160 temperature sets were obtained from 25 adult intensive care patients over a 6-month period. Results: About 75.2% (n = 115) of chemical and 50.9% (n = 78) of tympanic readings were within a +/- 0.0-0.4 degrees C range of the pulmonary artery catheter. Both the chemical and tympanic thermometers were significantly correlated with temperatures derived from the pulmonary artery catheter (r = 0.81, P < 0.0001 and r = 0.59, P < 0.0001) and limits of agreement were -0.5-0.9 degrees C and -1.2-1.2 degrees C respectively. The chemical thermometer was associated with a mean temperature difference of 0.2 degrees C, which increased 0.4 degrees C when used in conjunction with a warming blanket. With regard to clinical significance 15.3% (n = 26) of chemical and 21.1% (n = 35) of tympanic readings might have resulted in patients receiving delayed interventions. Conversely 28.8% (n = 44) of chemical and 37.8% (n = 58) of tympanic readings might have resulted in patients receiving unnecessary interventions. Conclusions: The chemical thermometer was more accurate, reliable and associated with fewer clinically significant temperature differences compared with the tympanic thermometer. However, compared with the pulmonary artery catheter both methods were associated with erroneous readings. In the light of these findings and previous research evidence, it is becoming increasingly difficult to defend the continued use of tympanic thermometry in clinical practice. However, as chemical thermometers are not without their limitations, further research needs to be undertaken to evaluate the accuracy and reliability of other non-invasive methods. Relevance to clinical practise: Chemical and tympanic thermometers are used in both adults and children in a wide variety of settings ranging from community to intensive care. As such these findings have significant implications for patients, users and budget holders.