Air caloric stimulation system

An air caloric stimulation system for providing air at controlled temperatures to patient's ears to induce nystagmus,

• said system comprising a source of air,
• power supply means for supplying electrical current,
• thermal element means connected to said power supply means for either heating or cooling the air as a function of electrical current direction through said thermal units,
• sensor means for sensing the temperature of the air going into the patient's ears,
• means for setting the temperature of the air going into the patient's ear,
• switch means for selecting a hot mode or a cold mode of operation to determine whether the air delivered is relatively hot or cold by controlling the direction of the current going through said thermal element means from said power supply means, and
• phase control means operating responsive to the difference between said sensed temperature and said set temperature for supplying current to said thermal units for a time period that is a function of the amplitude of said difference.

An air caloric stimulation system for eliciting a nystagmus condition in a patient by stimulating the patient's ear with an air stream of controlled temperature,

• compressed air supply means,
• means for supplying air from said air supply means to the patient's ear,
• temperature setting means for setting the temperature of the air delivered to the patient's ear to a desired level,
• sensor means for sensing the actual temperature of the air delivered to the patient's ear,
• thermal element means for supplying or removing heat from the air supplied to the ear responsive to the duration and direction of current therethrough,
• power supply means for supplying electrical current to said thermal element means,
• control circuit means for controlling the electrical current from said power supply both as to direction and duration as the electrical current passes through said thermal element means,
• said current direction and duration being supplied as a function of the difference between said set temperature and the actual temperature, whereby said actual temperature is made equal to said set temperature by the controlled current passing through the thermal element means,
• said control circuit means further including timing means for indicating the time and duration of the delivery of air to the patient's ear, and
• said timing means including alarm means to alert an operator of said air caloric stimulation system that a desired amount of time has elapsed.

An air caloric stimulation system for providing air at controlled temperatures to a patient's ear to induce nystagmus,

• said system comprising:
• a source of air,
• power supply means for supplying electrical current,
• Peltier elements connected to said power supply means for heating or cooling the air as a function of electrical current direction through said Peltier elements,
• means for setting the temperature of the air going into the patient's ear,
• switch means for selecting a hot mode or a cold mode of oepration to determine whether the air delivered is relatively hot or cold,
• phase control means operating responsive to the difference between said sensed temperature and said set temperature for supplying current to said Peltier elements for a time period that is a function of the amplitude of said difference,
• liquid exchange equipment for cooling said Peltier elements,
• said phase control means including means for determining the difference between said set temperature and said sensed temperature and for converting the sensed temperature to a first signal and the set temperature to a second signal,
• means for providing an error signal as a function of the difference between the first signal and the second signal,
• control means for using the error signal to control the current duration through said Peltier elements, and
• said control means including means for synchronizing the error signal to the line frequency to convert the error signal to a square wave signal having a frequency that is twice the line frequency and having the duration of the positive portion varied as a direct function of the amplitude of the error signal.