This tip gives you some practical hints on preparations that can help you optimize test results when using the Eclipse for ABR, ABRIS and ASSR testing.
Low noise is essential for clear results in any evoked potentials recording.
Both the physical location as well as the state of the patient can influence the noise level.
1. Make sure that your test room is suitable for testing
If you follow the below recommendations, you are well ahead of making sure that your room is suitable for testing:
- Use a magnetically shielded and soundproof - or at least very quiet room or booth
- Use a dedicated ground only for the Eclipse
- Separate any equipment cables, e.g. separate electrode cables from transducer cables
- Turn off or disconnect lights and other equipment that you are not using
If there is too much ambient or electrical noise in a room, in some cases, you can improve the set-up by moving to another test location.
Alternatively, moving the patient bed within the existing room can also improve the noise level as cables and electrical sources generating noise may be hidden in the wall.
2. Make sure that your patient is in the right state
Your patient should:
- Be relaxed and calm
- Have his eyes closed and face and jaw muscles relaxed
- Be lying or reclining comfortably in a bed or chair
So turn the lights of, and let your patient fall asleep. It will help improve the test results.
3. Prepare your patient correctly
Correct skin preparation and mounting of electrodes is important for optimizing electrode contact to the skin and thus reducing the electrode impedance.
We recommend that you use an abrasive preparation gel to clean the skin, e.g. NuPrep.
You should carefully attach the electrodes tightly to the skin by touching the outer edge of the electrodes.
For more details on how to prepare your patient and mount electrodes, we recommend that you read our tips on mounting electrodes.
4. Check the electrode impedance
When you have mounted the electrodes and electrode cables have been attached, we recommend that you check the electrode impedance by using the indications on the Eclipse preamplifier.
Under normal circumstances, the aim should be an impedance level of 3 kOhm or below.
5. Adjust the rejection level
With the Eclipse, you can adjust the rejection level according to electrical interference in the room as well as the state of the patient. The higher the rejection level value, the more noise is recorded during each average. That's why, the lowest possible rejection value (without rejection) is preferred.
Typically, when doing ABR with the Interacoustics Eclipse and under the above described conditions, you can make recordings using a rejection level of 40µV.