The influence of body temperature on transient evoked otoacoustic emissions

Thirty patients undergoing open heart surgery under induced hypothermia had transient evoked otoacoustic emissions (TEOAE) recorded during cooling to 26.07 degrees C (standard deviation (SD) 4.25 degrees C) vesically measured temperature and 24.86 degrees C (SD 4.7 degrees C) nasopharyngeally measur ed temperature respectively. Subsequently the patients were rewarmed until normal body temperature was reached again. There was a clear influence of b ody temperature on the amplitudes and reproducibilities of the TEOAE. The r elationship of temperature and amplitude or reproducibility during the cool ing phase was significantly different from that during rewarming. No TEOAE were measurable during cooling at a mean temperature lower than 33.41 degre es C (SD 2.04 degrees C) vesical temperature and 30.16 degrees C (SD 3.0 de grees C) nasopharyngeal temperature respectively. During rewarming the echo es became recognizable again at a mean temperature of 28.75 degrees C (SD 3 .38 degrees C) vesical temperature and 27.49 degrees C (SD 2.99 degrees C) nasopharyngeal temperature. These results suggest a hysteresis in the relat ionship between the amplitude of TEOAE and temperature, similar to the well -established relationship between evoked potentials and temperature.