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Help with an experiment

  1. Sep 24, 2010 #1
    Question:
    What substance (non-toxic and obtainable) when placed on my ear drum and heated with hot air will cause the most cooling of my inner ear through convection?

    Background:
    I'm an otolarngology resident and recently saw a dizzy patient who had just undergone VNG (videonystagmography). This patient had a caloric response that was opposite of what was expected. Warm air stimulated nystagmus beating to the oppose side instead of the same side. I examined the patient's ear under the microscope and his tympanic membrane was very inflamed and moist. I theorized that convection from the evaporation that occured as warm air was blowing across his moist tympanic membrane actually cooled his horizontal semicircular canal. I looked up some literature and this effect (I believe the physics term is convection?) has been shown to occur with perforated TM's but never with an intact TM. I tried to replicate this in our balance lab with a 50% rubbing alcohol and 50% normal saline solution of my tympanic membrane but failed.
     
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  3. Sep 25, 2010 #2

    Drakkith

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    Is there a reason you used warm air instead of cool? Wouldn't cool air cool off the eardrum better?
     
  4. Sep 25, 2010 #3

    Andy Resnick

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    IIRC, otholith repositioning procedures commonly use warm saline flushes to create flow in the inner ear. The effect could be similar to what you observed.

    Your idea to use alcohol was a good one, that will also cool the tympanic membrane due to evaporation- can you use 70% EtOH? How much cooling do you think you need?
     
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