Air versus water caloric test

Abstract

The air caloric test is favoured because of the advantage of higher convenience for patient and operator and its applicability in situations where water is contradicted. We examined 20 normal subjects with air (60 s, 12 min, 45 degrees/29 degrees C) and 25 with water (30 s, 30 cm3, 44 degrees/30 degrees C) caloric test. Additionally, we evaluated the influence of flow rate and irrigating tip position on the temperature near the tympanic membrane during the irrigation, using a polyacryl copy of the external auditory canal. A high flow rate and a reproducible tip position--close to the tympanic membrane appeared to be essential to achieve reliable results in air caloric test. Furthermore, measurements of the actual temperature should be done at the irrigation tip delivery in every air caloric test. The lower heat capacity of air, turbulences near the tympanic membrane and air aspired from the environment are the main reasons of more distinct temperature drops in the air caloric test. We observed a significant (P less than 0.05) difference between maximum slow phase velocity in air (11.5 degrees C/s) and water (19.5 degrees C/s) irrigation. The relative standard deviation was markedly higher for air irrigations. Therefore, in spite of the advantages of the air caloric test, the disadvantage of a higher variability, even when using a sophisticated technique, has to be considered.