oaefit

Susan M Lopez lopezs at musc.edu
Tue Aug 26 19:52:04 EST 1997


>From: Christine Stegemann <cmsmoose at ican.net>
>To: audiolog at net.bio.net
>Subject: oaefit

>Just started newborn screens with transient OAE's , but am having a 
>problem with fit... The ILO92 manual is not very clear as to wht 
>happens with a poor fit, just shows what a poor fit looks like. I'm 
>getting a lot of "ringing" in the stimulus--can this give me false 
>results that could ultimatley make a hearing impaired child "pass?" Any 
>info would be great!!

>Chris

Chris-

	I'm sure there are a lot of other people out there who have loads
more experience than I do, but as a new user of emissions to screen
premies and newborns, the fit is a tricky issue and you'll get better
really fast but in the beginning, your fail rate may be higher than what
you read in the lit due to being low on the "learning curve."

	I started screening newborns and NICU preemies in early May.  I
have found that squirmy babies are more likely to fail.  Newborns also are
prone to fail because they still often have birth canal goop in their
external canals.  The screen may tell you your fit is OK (green circle)
but if your noise is high (the little register on the right side of the
screen that is a pink/purply line with a white arrow you can use to set
your reject level for the noise levels) your kid will also be more likely
to fail, unless they've got gang buster emissions.  On the other hand, if
you jam that probe in the kid's ear and the noise goes to almost nothing
and you still have a green circle, but you aren't getting a response,
don't trust your fit.  One thing that is very helpful for me is using a
low frequency filter and using the "quickscreen" option.  The Quickscreen
option goes a lot faster than the regular test function.  The low
frequency filter setting may be something that the people using the
equipment before me set up that doesn't come already programmed.  Its an
option I can turn on and off and a green box appears in the upper left
hand corner of the middle of the screen which shows the temporal envelope
of the response you are getting.  Also, after you get a response,
filtering the low frequency "noise" out can help clean up the waveform and
get your reproducibility up to an acceptable level if you find it's not
good.  I hit F3 and a screen comes up with the noise and emission laid out
across frequency.  You can go in and set a band pass filter with a low
parameter (use your arrow keys to set the cursor on where you want to
filter out the lows and hit "L" and then use the arrorw keys to set the
cursor on where you want to filter out the highs and hit "U", then hit "B"
and this will set your band pass filter settings).  Be careful with
filtering, though, and save your unfiltered response first, so that if you
don't like what you get after you filter you can start over with the
original response.

	I am quite certain that this explanation sounds really mickey
mouse and that I have many bionet. audiology readers rolling their eyes in
disgust at my lack of "scientific" explanation here.  You sounded like you
needed help on this level, and as a user of the machine myself, I could've
used this kind of help when I started out.  You can email me privately if
you have other questions if the group isn't interested in button pushing
on the ILO88 and you need this kind of help.  I don't claim to be an
emissions authority, but I do claim "trench" knowledge of what works and
doesn't work on the job on the spot.  You probably already do this, but if
you have access, take along an otoscope and a bridge--as this can be
helpful.  When you have kids fail in the beginning, its a good idea to
assume you are the problem and not that there's something wrong with the
kid's ear....

Susan
lopezs at musc.edu

all opinions/ideas expressed are functions of my addled brain solely, so
don't sue anyone but me over anything written here....  :-)





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