CALORIC APPARATUS

Typical Number in Hospital: 1

Cost Bands: 3,4

References:

Patients with problems of vertigo or dizziness are often referred for vestibulometric tests. One of the most common tests is called the caloric test in which the patient's ear canal is heated or cooled by the introduction of warm or cool water (the usual temperatures are 44 and 30[d]C, although more extreme temperatures are applied when air is used rather than water).

This has the effect of heating or cooling the temporal bone and thus the semi-circular canals of the human balance mechanism, causing eddy currents in the fluid within the canals. These eddy currents cause the patient to experience a feeling of motion, resulting in eye movements called jerk nystagmus. The speed or duration of this nystagmus can be measured subjectively by using an infrared viewer or Frenzel glasses, or objectively using an electronystagmograph. These measurements are a crude indication of the sensitivity of the balance mechanism under test.

The caloric apparatus is the thermostatically controlled water tanks which comprise an earthed metal tank, circulating pump, dial thermometer and heating element with thermostatic control.