What is the Electrode Switching Feature in the Bio-logic AEP Software?

Question

Answer

The electrode switching feature in our AEP application was implemented to allow users who perform one channel ABR recordings to collect right ear and left ear ABRs without having to manually change the position of the inverting (aka "reference") and ground electrodes in the patient connection cable.

The electrode switching feature is designed to interact with the stimulus ear in the following manner:

• When the stimulus is presented to the right ear, the amplifier inputs that are used for data recording are those that are plugged into the Channel 1 Input 1 (non-inverting) jack and the Common (or ground) jack.
• When the stimulus is presented to the left ear, the amplifier inputs that are used for data recording are those that are plugged into the Channel 1 Input 1 jack and the Channel 1 Input 2 jack.

The caveats for use of electrode switching are:

• When it is enabled, you must plug in your electrodes in a specific way for ABR testing. The left ear electrode must be plugged into Channel 1 Input 2. The right ear electrode must be plugged into the Ground (common) jack. The Cz or high forehead (non-inverting) electrode must be plugged into Channel 1 Input 1.
• When it is enabled, you should NOT manually change the position of the right and left electrode leads in the patient connection cable when you change the test ear. If you do, you are defeating the purpose of the electrode switching feature and you will be collecting contralateral recordings when you test the right ear.
• If you disable electrode switching in your one channel ABR protocol, then you must manually change the positions of the inverting and ground electrodes in the patient cable when you change from one stimulus ear to the other. Failing to do so will mean that for one of the ears (which one depends on how you choose to plug in the electrodes) you will be recording contralateral rather than ipsilateral recordings.

Used properly, electrode switching is a very helpful tool. Used incorrectly, it can result in incorrect data recordings, so it is worthy of close attention when you are designing your own test protocols in the AEP application.

Visit www.bio-logic.com for more information or the Bio-logic Web Channel on Audiology Online at www.audiologyonline.com/channels/bio-logic.asp

Kathy Murphy, MA Global Marketing Manager -Hearing Diagnostics Bio-logic Systems Corp. Ms. Murphy worked as a clinical audiologist for 15 years and has been involved in hearing product design and marketing at Bio-logic for over 15 years, with particular emphasis in evoked potentials and otoacoustics emissions technology.