Central Apnea question

[Peter_C]

I do not know your machine.

But on a Resmed machine, you set:

MIN EPAP
MAX IPAP
Pressure Support

So if I wanted mine to act like a 'Auto-CPAP', I would do this:
MIN EPAP (when you are doing anything but inhale) to your comfortable lowest number
MAX IPAP (when inhaling only) to wide open, in my case '25'
Pressure Support to '1'. (Can't do zero on my machine)

As my machine raises both sides by the same amount a 9/10 could become a 11/12, 15/16 and so on, as it can't change the PS automagically.

[Sleepster]

Exhalation Pressure Relief, known as EPR, C-Flex, Bi-Flex, or A-Flex, is a way of reducing the exhalation pressure by 1, 2, or 3 cm.

To reduce it further, a bi-level machine (also known as a BiPAP or VPAP) can be used to set the exhalation pressure (EPAP) lower yet.

CPAP-induced CSA is a real effect that tends to subside with time. There is evidence that this is made worse, or even caused by, bi-level therapy. This is why you hear people talk about reducing the EPR or raising the EPAP to reduce CSA.

[vsheline]

You can make the BiPAP act like an APAP.

Thanks for that Bama. I had mistakenly initially thought EPR was referring to the exhaust pressure (EPAP in a BiPAP). I understand now that he was referring to the Philips equivalent C-Flex/B-Flex setting.

Turning off or decreasing EPR is like turning off or decreasing PS.

EPR on ResMed APAP machines and Pressure Support (PS) on all bi-level machines are both equal to the difference between EPAP and IPAP, except PS represents an increase and EPR represents a decrease.

PS on bi-level machines is added to EPAP to get IPAP.
EPR on ResMed APAP machines is subtracted from IPAP to get EPAP.

EPAP + PS = IPAP
IPAP - EPR = EPAP

EPR is pressure based, like true bilevel, except it is limited to 3 cm H2O.

Using EPR, the low EPAP pressure does not transition back to the higher IPAP pressure until inhalation actually begins. So a ResMed S9 AutoSet with EPR adjusted to "3" is similar to a ResMed S9 VPAP Auto with PS adjusted to 3, except EPR cannot be set higher than 3 on the S9 AutoSet, and PS can be set as high as 10 on the S9 VPAP Auto.

But Flex does not work quite the same way as EPR.

Although both EPR and Flex introduce some exhalation pressure relief, Flex does not last as long.

On Philips Respironics models, Flex is Flow based. During the times when there is no exhalation Flow, Flex adds no exhalation pressure relief.

Because it is usually natural for the exhalation Flow to reduce to nearly nothing well before inhalation actually begins, it is normal for Flex to end well before inhalation begins, about half way between the start of exhalation and the start of inhalation. This is different than true bilevel. EPR and PS, in contrast, last the entire period between the start of exhalation and the start of inhalation.

This is why Philips Respironics BiPAP models offer both PS and Flex, because these are different.

And this is why the ResMed VPAP Models do not offer both PS and EPR, because these are the same, except PS has a larger range.

Take care,
--- Vaughn

ADDED:

And to make a bi-level S9 VPAP Auto act like an AutoSet prescription, one would set PS the same as EPR, and would also adjust Min EPAP to match the minimum EPAP used by the AutoSet, which is the AutoSet's Min Pressure minus it's EPR.

For example, if AutoSet settings are 10 to 15 for Pressure, and EPR is 3, the equivalent settings on the VPAP Auto would be:

PS = same as EPR = 3
Min EPAP on bi-level would be AutoSet's Min Pressure minus EPR = 10 - 3 = 7
Max IPAP on bi-level would be same as AutoSet's Max Pressure = 15

To make a PRS1 BiPAP Auto act like an APAP is similar, except the PRS1 BiPAP Auto has a feature which the S9 VPAP Auto does not have.

On the BiPAP Auto the PS will very slowly vary and automatically adjust itself within a range, with the goal of best minimizing Flow Limitation and pressure. So the BiPAP Auto has a Min PS setting (fixed at 2 cm H2O on earlier models and adjustable between 0 and 8 on Series 60 model) and a Max PS setting. On the S9 VPAP Auto the PS is fixed, only manually adjustable between 0 and 10.

[jbuchanan6196]

I'm just taking all this in.

[jbuchanan6196]

What can you all tell me about flow limitation? I can't tell what's considered 'normal'? Seems like I heard that it wasn't measured like a normal graph so I'm not sure.