BIOCALIBRATIONS AM/PM

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BIOCALIBRATIONS AM/PM

Postby sharonlags » Fri Mar 16, 2012 8:55 am

New to this site :)

We have 2 labs, 2 different scorers, 2 different systems (Alice 5 and Somnostar 9.1D)

One scorer wants PM and AM biocalibrations (Alice 5 system), which shows impedence the whole study.

The other scorer wants PM biocalibrations (Somnostar) only.

I have looked on several sites to see if this is a AASM protocol or just a preference to some labs and if so, can you please tell me where it is?

I don't think that we should have to do AM biocalibrations if our impedences are within normal range throughout the study.
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Postby bduce » Fri Mar 16, 2012 9:17 am

1st ask yourself the question "Why do we do patient calibrations in the first place?" That is your starting point.
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Postby stars » Fri Mar 16, 2012 9:38 am

May be ask first what different biocal and impedance
Why need impedance and biocal
why we technical calibration first impedace second and biocal next
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BIOCALIBRATIONS AM/PM

Postby sharonlags » Fri Mar 16, 2012 10:29 am

Patient calibrations are performed to show the amplifier and patients responses together performing different movements, whereas the impedence shows the equipment (leads, etc) and contact to the patient is within normal range in the EEG, EOG, legs, references, etc.

Still do not understand why it would be necessary to perform AM biocals for one scorer and not the other. If it is a AASM protocol, then of course, I will perform it otherwise I don't see the sense to only annoy the patient. They are most of the time out of it!
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Postby bduce » Fri Mar 16, 2012 10:29 am

Ah Stars. That would be my second question!
:lol:

Maybe I am wrong but the impression I am getting Sharon is that you think impedance measurement is the main reason for doing patient calibrations.

I don't think that we should have to do AM biocalibrations if our impedences are within normal range throughout the study.


The problem with that thinking is that I can provide you with some artefactual signals with good impedances. So are impedances the be-all and end-all for patient calibrations?????

If not, why are you doing pateint calibrations?
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Postby sharonlags » Fri Mar 16, 2012 10:41 am

May be I'm not saying it correctly,

I understand if you have good impedence that you may have artifact. You may have good contact which will give good impedence but visually you can see artifact so you know that the leads have to be moved and reapplied to the patient. Then, I would perform an impedence and also visually see that the artifact is removed due to placement. I wouldn't do biocals again. Biocals are the patient's response!
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Postby bduce » Fri Mar 16, 2012 10:56 am

Sharon
Understand what you are saying but I would disagree with you when you say that the biocal is the patients response. The patient is not what you see on the screen - they are in the room. What you are seeing are recording of specific signals which are used as a REPRESENTATION of specific patient activities.

Another way of looking at it. Have you ever noticed studies where the wake baseline chin EMG seems to reduce in its peak to peak range progressively during the night? Why is that?
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Postby somnonaut » Fri Mar 16, 2012 11:34 am

"peak to peak EMG levels? How was this measured? What consistent patient specific event was created at both extremes to get this "known signal"?

If the impedance is same start to end, the only explanation is increasing REM time , ergo increased time with low EMG levels.
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Postby somnonaut » Fri Mar 16, 2012 12:12 pm

The field can use a standard for gauging just how much a subject bites down.
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Postby sharonlags » Fri Mar 16, 2012 12:13 pm

We are going off topic here and I appreciate your responses.
My main question is: Is it necessary or "protocol" to perform AM biocalibrations? If so, why?

8)
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Postby somnonaut » Fri Mar 16, 2012 1:19 pm

Yes, to gauge if the electrode/sensor is still functioning at the same level as at start of study. It is sort of a holdover from paper based PSG, where once you changed a sensitivity or gain on a channel, that was how the waveform was represented, so if the AM cals were different, and the tech forgot to note on the recording a gain change, the signals reflected this new "reality" and allowed the scoring tech to search backwards through the record for the gain change and score accordingly from that point on. And yes, this is basically not an issue anymore as the currently valid AASM accreditable systems must have the ability to log the system changes and represent the acquired recording as the way the tech saw it, and as the scoring tech scored it. So, in this regard computers have far outstripped this need. What they have not done is guarantee that the sensor is actually in place. Meaning, if you are using leg leads, and they have slipped to a different location, they may still have perfect impedance, but when you ask to flew your leg, they no longer yield a signal. THAT is the reason for AM calibrations. To ascertain if the "sensors are still a sensing."
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Postby sharonlags » Fri Mar 16, 2012 1:58 pm

Thank you for your response and explaining the reason why. This is a constant learning process. I'm on my own at our 2 labs. So when I ask questions to the scorers, I get no response or get 2 different responses. I'm glad I came across this site. :wink:
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Postby labman2 » Fri Mar 16, 2012 2:04 pm

somnonaut wrote:Yes, to gauge if the electrode/sensor is still functioning at the same level as at start of study. It is sort of a holdover from paper based PSG, where once you changed a sensitivity or gain on a channel, that was how the waveform was represented, so if the AM cals were different, and the tech forgot to note on the recording a gain change, the signals reflected this new "reality" and allowed the scoring tech to search backwards through the record for the gain change and score accordingly from that point on. And yes, this is basically not an issue anymore as the currently valid AASM accreditable systems must have the ability to log the system changes and represent the acquired recording as the way the tech saw it, and as the scoring tech scored it. So, in this regard computers have far outstripped this need. What they have not done is guarantee that the sensor is actually in place. Meaning, if you are using leg leads, and they have slipped to a different location, they may still have perfect impedance, but when you ask to flew your leg, they no longer yield a signal. THAT is the reason for AM calibrations. To ascertain if the "sensors are still a sensing."


Very succinct explanation Claude!
Welcome Sharonlags!

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