Question
We have been referring our patients out for ENGs, but are now considering purchasing equipment and providing ENGs. What are the pros and cons of using air or water calorics? What should we consider when deciding whether to offer ENG, VNG or both? Thank you for any information you can provide.
Answer
There is absolutely no question that moving to VNG technology versus ENG is the way to go. You eliminate the hassle and time of electrode applications, the problem of signal drift with time, higher resolution and most importantly you will have higher quality recordings. Automatic analysis software on most systems is far superior when used in conjunction with VNG technology. As we evolve into the Firewire Camera technology the quality of the recordings will be even better and the camera speed (i.e. 174hz) will permit better Saccade analysis where eye movement speed exceeds the capture rates on some instruments.
Water caloric irrigators are often times the first choice among many experts because of the more consistent stimulation that can be obtained from user to user and the ability to stimulate when ear wax partially obstructs the view of the TM. The downside to water irrigators is their size and the maintenance. Things like keeping a supply of distilled water, keeping the water tanks filled and clean and the obvious mess and clean up during and after stimulation. Air caloric irrigators do require a longer stimulation period and more attention to pointing the air stream directly at the TM, but many individuals who now use air irrigators would never go back to water. You can also stimulate a patient's ear when there is a perforation - whereas you would not be able to do so with water. Just be aware that warm air stimulation with a perforation can generate a reverse beating nystagmus because of the cooling effect of the moisture in the middle ear space.
David Speidel holds a Masters Degree in Audiology from the University of Wisconsin - Oshkosh (1979). He has been in the field of Audiology for over 25 years, first in clinical practice and then 15 years as a sales and support representative for an equipment distribution company. Since 1997 David has been working in a sales and audiology support capacity in the William Demant Group (Maico for 3 years and then Interacoustics until the present).