Flow Limitations

[BrianT]

Hello all,
I am curious about one of the fields on my Encore Viewer reports. When i have my Respironics M Bi-PAP Auto set so that I have my prescribed 13/9 pressures set (non-auto), I never get any values showing on the Flow Limitations field of the daily report (graph). When I set the machine to Auto and set a range of 14/8, or any other range, I always get Flow Limitation numbers on the graph.
I'm not sure what this is about. Are the Flow Limitation occurences related only to the Auto settings? What are Flow Limitations exactly?
Are these numbers as important as the AHI numbers?
If so, what can be done to eliminate or lower them?
Brian

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, auto

[ozij]

I would put it this way:
Flow limitations are "almost" hypopneas, but not yet. In auto mode the machine uses them for calculating what to do about your pressure and how to understand your pattern. In fixed mode the machine doesn't need them because is doesn't change its behavior in response your breathing.

O.

[jimbassett]

I'm not sure about your machine and its workings but, Flow Limitations, UARS (upper airway resistance syndrom) , and RDI (resistance disturbance index) are basically all the same thing. The UARS is usually measured as hypopneas or Central Apneas. This is usually not picked up on the standard CPAP machine as I understand it. These numbers are very important for proper therapy. Not all apnea sufferers have OSA so it takes a special configured machine to trace these ( Complex Breathing Disordered Syndrom) maladies. Hope you get it worked out. Regards jim

[xyz]

> When I have my Respironics M Bi-PAP Auto set so that I have my pressures set (fixed),
> I never get any values showing on the Flow Limitations field. When I set the machine to
> Auto, I always get Flow Limitation numbers on the graph.

Funny that you should say that. I haven't had my Auto M bipap for all that long. I recently discovered this myself. For one week I ran it in fixed bipap. For 1.5 weeks I have run it in auto bipap.

Fixed: Ob Apnea average 0.1, range 0.0. - 0.2
Auto: Ob Apnea average 0.1, range 0.0. - 0.2

Fixed: Hypopnea average 0.1, range 0.1 - 0.4
Auto: Hypopnea average 0.6, range 0.3 - 1.0

Fixed: AHI average 0.2, range 0.1 - 0.6
Auto: AHI average 0.6, range 0.3 - 1.2

Fixed: Flow limitation average 0.0, range: 0.0 - 0.0 <----
Auto: Flow limitation average 1.4, range: 0.6 - 2.3

Fixed: Vib snore average 0.7, range 0.2 - 1.9
Auto: Vib snore average 8.1, range 5.6 - 12.6

In Auto, hypopneas are 6X, AHI is 3X, flow limitation is hugely higher, and vib snore is 11X.

The numbers above are not from page 3 of the EV report where EV dumbly displays them as whole numbers, but from page 4 where it shows them to one decimal place.

What are the units for this data: seconds, minutes, number of events, what?

A few details: EncoreViewer 1.0.0.003, Auto M firmware version 4.03.
Does anyone have different versions?

The constant pressures for the fixed bipap was 12/8.
The 90% pressures for auto bipap from the EV report (averaged for the 1.5 weeks) are 11.9/7.2.

The 90% numbers are a little misleading because the report shows it sitting at 8 epap and 6 ipap for 3+ hours per night (spread throughout the night, not all at the start). The starting pressures for auto mode are 8/6.

Why do sleep docs, DMEs, and mfgs use that 90% figure anyway? It seems to me that it could be misleading.

[ozij]

The 90% pressure is not misleading if you use it properly.

It means "if you want to get good therapy for 90% percent of the time, use this pressure. Because there were only 10% of the time when you needed higher pressure".

You may spend 75% of your sleeping time at a pressure of 8. That leaves 25% in which you need more. If you shoot up to 16 for the rest of the night, your 90% pressure will be 16.
On the other hand, if you shoot up to 12 for another 20% of the night, and the spend the last 5% at 16, your 90% percent pessure will be 12.

Think of it as information that says: "You can't afford to sleep at less than this pressure".

O.

[Snoredog]

when you are on "fixed" pressure, it is assumed the Flow Limitations are taken care of or the delivery pressure prescribed is eliminating the Flow Limitations.

In the Auto mode, the machine must sense those FL's and respond to them. Nearly all auto's begin treatment in the presence of Flow Limitations.

[BrianT]

Thank you all for the explanations. The fog is starting to clear.
Brian

[xyz]

Can anyone answer my question:
What are the units for this data: seconds, minutes, number of events, what?

[Wulfman]

Can anyone answer my question:
What are the units for this data: seconds, minutes, number of events, what?

WHICH "data"? If you're referring to AHI (Apnea Hypopnea Index), that's in events per hour.

Den

[xyz]

> WHICH "data"?

The ones in my post above. That's where I originally asked the question. (Ob Apneas, hypopneas, AHI, flow limitations, vib snore.)

> If you're referring to AHI, that's in events per hour.

Is it the same for all the other items?
Is this info in any documentation from Respironics?
I want to learn more about this.

So if I have an OA value of 0.1 (which I have gotten many nights) and I have slept for 8 hours, then I had 0.8 OAs. Approximately.

And when I had 12.8 vib snores? If the units are the same, that would say I snore every 4.6 minutes.

[ozij]

1 Apnea in 8 hours gives an Idex of 0.125.

It is rounded down to .1 in the report.

You will lots of info in the CPAP FAQs (red balloon) and Our Collective Knowledge (yellow light bulb) on this site. You will also find lot's of info in "Mile High Sleeper"'s blog http://smart-sleep-apnea.blogspot.com/

And cpap.com has a questions and answers part that will also help you.
O.