Variance in AHI readings

[NotMuffy]

BTW, some more traditional ResScan graphics in this case presented in

viewtopic.php?f=1&t=61477&p=578203#p578203

using the "Calming Gray" skin.

[billbolton]

If pressure drops by 3 cmH2O at EPR 3, then the airway may close. If that's where FOT is probing for centrals, it may now register a closed airway.

There's really no choice to do FOT other than after an exhalation has concluded (whether EPR is engaged or not). Clearly the airway must be open if there was a exhalation in progress.....

If there is a reasonable suspicion of misssed central apneas, then disabling EPR, for a week or so, might be a smart move in terms of looking for a difference in scoring efficacy

Cheers,

Bill

[Pugsy]

If pressure drops by 3 cmH2O at EPR 3, then the airway may close. If that's where FOT is probing for centrals, it may now register a closed airway. I think that may be an explanation all of bandnut's "obstructive" apneas. In summary, if S9 says it's a central, then it is near certain to be so, but if it says it's an obstructive, I think measuring airway patency at 3 cmH2O lower than therapeutic pressure is going to miss a ton of events if there's an element of obstruction. However, I suppose if it's a case of pure centrals, then wingin' the pressure around like that may not make a difference in the yield.

I would imagine this would explain why some people experience an increase in obstructive events with a reduction in EPR. A little more pressure during that exhale phase might have kept that airway open. So how do I determine what to say if someone has a few centrals and obviously still a number of obstructive events that needs addressing? Where is the line in regards to centrals? Reports that show a crap load of events like OutaSync had before centrals were flagged or some of the most recent reports that show a definite central predominance? Those are pretty obvious.

How easy is it to trigger centrals with a pressure increase? How many centrals must a person have before I worry about triggering centrals with an increase in pressure. I can see discarding a handful but I just was never told where it was okay to not worry about the centrals.. If the centrals are going to happen anyway, do we just go ahead and do our usual to minimize the obstructive events and just sort of watch the centrals to see if they get worse? Under what circumstances is it possible for them to get worse? I haven't been told or read anything that explains that. Only been told "centrals, beware, watch out, pressure increase will make it worse, you will get in crap load of trouble." well not exactly that last part but I would feel bad if I in any way offered an idea that really messed things up. It was a lot easier before the machines flagged centrals.. Would just ask if any history of them and go from the "no"...

Thank you for taking time to explain what you have already. I do appreciate it and I see a wee bit of light in the tunnel.

[Pugsy]

Still on the sbject, can someone tell me what the following "terms" mean and what's being measured?
Flow,
Flow limitation,
Minute ventilation and
Snore index

How can the S9 measure snore when there's no microphone or audio in it?

Remember I don't have same machine and may not have the right handle on things
Someone else please explain it better. Then I will learn also.


Not sure what flow is in the context of the report. Air flow . It shows a breathing rhythm that can be looked at to possibly see what might have happened...
Flow Limitation is something that is blocking the air flow to some degree. I believe it is one of the things the machine senses for and evaluates for naming or flagging events.
Minute Ventilation.. I have no clue how to describe it and how it relates to the report.
Snore Index, .. Obviously snores can be a sign of flow limitation and a precursor of an obstructive event.
Measured more by vibration of sound. Hose movement also causes vibrations that sometimes gets interpreted as snores.

[NotMuffy]

If pressure drops by 3 cmH2O at EPR 3, then the airway may close. If that's where FOT is probing for centrals, it may now register a closed airway.

There's really no choice to do FOT other than after an exhalation has concluded (whether EPR is engaged or not).

That isn't why a problem exists. A problem exists because EPR continues "after an exhalation has concluded". If they turn if off before then, they'd have to call it "CFlex".

Clearly the airway must be open if there was a exhalation in progress.....

I'm not sure what the point there is. Even in the most severe cases, exhalation can occur because the "one-way valve concept" has been reversed. However, it may just be barely so, creating significant expiratory resistance (or, the "expiratory intolerance" noted by Barry, who thought he could treat it by lowering EPAP).

If there is a reasonable suspicion of misssed central apneas, then disabling EPR, for a week or so, might be a smart move in terms of looking for a difference in scoring efficacy

Thanks, Bill, but I think they got that already.

[sleeptiger]

Had a great 9 hr sleep last night, maybe it was becos I had only 5 hrs the night before.
The LCD read cpap 9.0. epr 2.0, ahi 3.7, ai 3.4 and centrals 2.7.
My only comment is that it appears the centrals have increased from the usual reading of about 1.7.
I'm gonna stay on these settings for the next 3 days and see the results.

[avi123]

After a few days the numbers changed to:


"The LCD read cpap 9.0. epr 2.0, ahi 3.7, ai 3.4 and centrals 2.7.

My only comment is that it appears the centrals have increased from the usual reading of about 1.7.
I'm gonna stay on these settings for the next 3 days and see the results."


How could it be effective? Don't you need to average the numbers over months?

About the Centrals, you just need to touch the mask, pinch the air tube, change body position, etc., and the Centrals will rise.

[Pugsy]

Had a great 9 hr sleep last night, maybe it was becos I had only 5 hrs the night before.
The LCD read cpap 9.0. epr 2.0, ahi 3.7, ai 3.4 and centrals 2.7.
My only comment is that it appears the centrals have increased from the usual reading of about 1.7.
I'm gonna stay on these settings for the next 3 days and see the results.

It is common to have variations from night to night in all the different types of events. Let's see what happens next few nights.
The math is a bit off, typo maybe ??
AI 3.4
CA 2.7
even if zero HI
AHI adds up to 6.1

Even that is an improvement over some of the other higher numbers you have reported though.

[Pugsy]

How could it be effective? Don't you need to average the numbers over months?

No.

An average of 9 AHI over months is still going to be 9 if nothing is done to try to optimize things.

Edit: If therapy is not optimal, no amount of time is going to change an average and bring down a clearly sub optimal AHI to an acceptable AHI. Avi, you have been on therapy for 4 months now? Still having average AHI over 10? How long do you want to wait for that number to reduce to what is generally accepted in the medical community to be adequately treated, that number being an AHI of less than 5. Just keep on thinking that it just takes time. Don't worry about your leak and keep just giving it "time".

The rest of us find that unacceptable. It is not for you to judge someone who wishes to improve things just because you don't want to.

[sleeptiger]

The LCD read cpap 9.0. epr 2.0, ahi 3.7, ai 3.4 and centrals 2.7.

AHI = AI + HI

AI= Obstructive apneas + Centrals

So I thinks this means that with an AHI of 3.7 and AI of 3.4, my HI (hyponpnea index) = 0.3

AI= 3.4 = OA+Centrals = OA + 2.7...this gives OA = 3.4-2.7 = 0.7,

so in summary, AHI =3.7, AI 3.4, HI 0.3, OA 0.7 and Centrals 2.7. Is this right?

[Pugsy]

so in summary, AHI =3.7, AI 3.4, HI 0.3, OA 0.7 and Centrals 2.7. Is this right?

Yep, you are right, my bad.. Note to self to remember ResMed counts centrals in AI...

In that case extremely well done and much better than what you have had before. Let's see what next few nights bring. You had a few low AHI numbers before the minor change according to your first post. Just want to see if things continue along these lines.

[sleeptiger]

Cheers Pugsy