Effects of stimulus duration on air caloric slow phase velocity

This study was designed (1) to assess the test-retest reliability of the slow phase velocity (SPV) in response to air calorics, (2) to compare four procedures for calculating the SPV (average of 3 beats, average of 10 beats, average of all beats in a 10 second period, and the single largest beat), and (3) to investigate the effects of the duration of air irrigation (45, 60, and 75 seconds) on the SPV. Three groups of 10 subjects each were administered test and retest air irrigations (8 L/min) in each ear at 24 degrees C and 50 degrees C. Reliability was assessed with the standard error of measurement, which was approximately 4 degrees/second for all SPV calculations. This value is consistent with previous research. The 1-beat and 3-beat measurements revealed larger SPVs (approximately 24 degrees/sec) than the 10-beat and 10-sec measurements (approximately 20 degrees/sec). Considering time efficiency, and to avoid the effects of an artifact on the single largest beat, the 3-beat average may be preferred for calculating the SPV. Finally, our data do not allow recommendation of a preferred stimulus duration from among those evaluated (45, 60, 75 seconds).