Cochlear SPrint Sound Processor Información técnica descargar pdf (Pagina 51)

CLINICAL GUIDANCE | SECTION ONE

When you convert a Freedom MAP to a Nucleus 24 MAP, input processing

options that are not supported on Nucleus 24 sound processors will not

be available. Similarly, when you convert a CP810 MAP to a Freedom or

Nucleus 24 MAP, input processing options (e.g. Noise with zoom) that are not

supported on Freedom or Nucleus 24 processors will not be available.

1.14 OBJECTIVE MEASUREMENTS

1.14.1 Electrically-evoked Auditory Brainstem Response (EABR)

EABR is an electrophysiological measurement technique that records the

response of the auditory brainstem to electrical stimulation from the implant.

Externally applied scalp electrodes are used to record the EABR. To perform an

EABR, you need an external evoked potential averaging machine with a trigger

input. The trigger input of your EABR machine is connected to the trigger

output of the Programming Pod. The trigger is a TTL compatible pulse.

When you perform an EABR with Custom Sound

™

EP software, only the

thresholds are stored in your Custom Sound database. The actual EABR traces

should be stored on the external machine.

Electrode Placement: EABR recordings from the non-implanted side usually

have a smaller stimulus artifact. Therefore, the following electrode montage is

recommended: (+) on the forehead, (-) on the non-implanted mastoid and a

reference on the contralateral cheek (a position in the middle between (+) and

the (-) electrode is best).

Recommended Setting for the EABR Machine

The ampliﬁer should have a fast response time. The high-pass ﬁlter cut-off

frequency should be set between 1 Hz and 150 Hz and the low-pass ﬁlter

cut off frequency at 5 kHz (or 3 kHz if needed). You need an analog to digital

converter (ADC) with at least 12 bits range and a sample frequency of 10 kHz.

The pre-ampliﬁer gain should be between 60 and 100 dB.

Tips for Recording EABR

• To prevent interference from the RF that is sent from the coil to the

implant during recording, an RF free period can be set in the software that

prevents RF being sent after a stimulus. Make sure that the RF free period

covers the measuring window of your external EABR equipment.

• Bipolar stimulation modes produce less artefact than monopolar

stimulation modes.

• Apical electrodes usually produce less artefact than basal electrodes.

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Cochlear SPrint Sound Processor Información técnica Pagina 51