INFRARED THERMOMETRY IN THE AUDITORY-CANA L - EVALUATION ON THE DIATEK-9000 INSTATEMP AND DIATEK-9000 THERMOGUIDE

Temperature of the tympanic membrane is recommended as a ''gold standa rd'' of core-temperature recording. However, use of temperature probes in the auditory canal may lead to damage of tympanic membrane. Temper ature measurement in the auditory canal with infrared thermometry does not pose this risk. Furthermore it is easy to perform and not very ti me-consuming. For this reason infrared thermometry of the auditory can al is becoming increasingly popular in clinical practice. We evaluated two infrared thermometers - the Diatek 9000 Thermoguide and the Diate k 9000 Instatemp - regarding factors influencing agreement with conven tional tympanic temperature measurement and other core-temperature rec ording sites. In addition, we systematically evaluated user dependent factors that influence the agreement with the tympanic temperature. Ma terials and Methods. In 20 volunteers we evaluated the influence of th ree factors: duration of the devices in the auditory canal before taki ng temperature (0 or 5 s), interval between two following recordings ( 30, 60, 90, 120, 180 s) and positioning of the grip relative to the au ditory-canal axis (0, 60, 180 and 270 degrees). Agreement with tympani c contact probes (Mon-a-therm tympanic) in the contralateral ear was i nvestigated in 100 postoperative patients. Comparative readings with r ectal (YSI series 400) and esophageal (Mon-a-therm esophageal stethosc ope with temperature sensor) probes were done in 100 patients in the I CU. The method of Bland and Altman was taken for comparison. Results. Shortening of the interval between two consecutive readings led to inc reasing differences between the two measurements with the second readi ng decreasing. A similar effect was seen when positioning the infrared thermometers in the auditory canal before taking temperatures: after 5 s the recorded temperatures were significantly lower than temperatur e recordings taken immediately. Rotation of the devices out of the tel ephone handle position led to increasing lack of agreement between inf rared thermometry and contact probes. Mean differences between infrare d thermometry (Instatemp and Thermoguide, CAL-Mode) and tympanic probe s were -0.41+/-0.67 degrees C (2 SD) and -0.43+/-0.70 degrees C, respe ctively. Mean differences between the Thermoquide (Rectal-Mode) and re ctal probe were -0.19+/-0.72 degrees C, and between the Thermoguide (C ore Mode) and esophageal probe -0.13+/-0.74 degrees C. Discussion. Alt hough easy to use, infrared thermometry requires careful handling. To obtain optimal recordings, the time between two consecutive readings s hould not be less than two min. Recordings should be taken immediately after positioning the devices in the auditory canal. Best results are obtained in the 60 degrees position with the grip of the devices foll owing the ramus mandibulae (telephone handle position). The lower read ings of infrared thermometry compared with tympanic contact probes ind icate that the readings obtained represent the temperature of the audi tory canal rather than of the tympanic membrane itself. To compensate for underestimation of core temperature by infrared thermometry, the r esults obtained are corrected and transferred into core-equivalent tem peratures. This data correction reduces mean differences between infra red recordings and traditional core-temperature monitoring, but leaves limits of agreement between the two methods uninfluenced.