Inner Ear Cooling Experiment: Non-Toxic Substance for Convection Study

[THaugen]

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 occurred 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.

 

[Drakkith]

Is there a reason you used warm air instead of cool? Wouldn't cool air cool off the eardrum better?

 

[Andy Resnick]

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 occurred 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.

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?