Confusion over PS equation

[David Clark]

There is a big difference between min EPAP and EPAP.
EPAP typically refers to actual pressure.

Also there is a big difference between max IPAP and IPAP.

A typical PS is something around 4.  A PS of 10 is extremely unusual.

We try to lead you toward good settings.  To do this we need to see how your body reacts to the settings we suggest.  If you choose to use different settings we have to continually adjust to the changes you choose to make which often obscures the results we are looking for.  If you don't understand why/what we are doing ask.

I get you Gideon and I'm not asking about it because I changed it or want to it's just that formula that was/is confusing me. Maybe it's the min vs actual or max vs actual that is what the formula is using that is confusing to me. I was just trying to understand how whoever came up with it came up with it. I think it's better if it's not something I try to figure out. I appreciate all of you offering your time and help with settings and I hope none of you misunderstood my question about the PS equation and took it that I was dicking around with settings.

[David Clark]

Ok. Gideon, I just saw the long comment you made after the one I quoted. I think I see my confusion now. I took the formula to mean what you should set the PS at. For instance if you set your IPAP at 20 and you set your IPAP at 9 then you need to set your PS at 11...and if 10 is the highest PS a machine allows then that is why I said you couldn't set it at 11...or whatever setting above 10. I'm not sure if that helps you understand what was confusing me or not.

[David Clark]

You're also right about striving for a number that in reality I'm probably already at if I remove all the junk and how that can be detrimental to treatment. Especially if someone has a touch of "perfectionism" in them and strives for that in pretty much everything. It can make you a little obsessive about "tweaking just one more thing" trying to find that perfection when in reality you just need to let it be what it is. That can be problematic in many areas other than pap treatment...trust me...I know.

[GuyScharf]

IPAP is the pressure at inhalation and EPAP is the pressure at exhalation; EPAP and IPAP change during the session as the machine adjusts your pressures based on events seen, etc.. PS is the difference between IPAP and EPAP.

On a VAuto machine, PS never changes and is fixed in the settings. For example if you have set PS=4, then the difference between EPAP and IPAP will always be 4.

Because the VAuto is an auto-adjusting machine, you have to set the limits within which it can adjust. "Min EPAP" is the minimum value of EPAP that the machine will use, and "max IPAP" is the maximum value of IPAP. But remember that PS is fixed and unchanging, so IPAP and EPAP increase or decrease together so as always to maintain the difference of PS.

For example, suppose min EPAP=6, max IPAP=10, and PS=4. This is a fixed pressure setting as there is no room for the machine to adjust pressures. It cannot increase EPAP without raising IPAP (which is EPAP+PS) higher than 10, which is set as the upper limit.

In an auto-adjusting configuration, if min EPAP=6, max IPAP=16, and PS=4, the machine can raise EPAP as long as IPAP isn't more than 16. Specifically, it can raise EPAP as high as 12 [max IPAP(16) - PS(4) = 12].

Does this help?

[Geer1]

You're also right about striving for a number that in reality I'm probably already at if I remove all the junk and how that can be detrimental to treatment. Especially if someone has a touch of "perfectionism" in them and strives for that in pretty much everything. It can make you a little obsessive about "tweaking just one more thing" trying to find that perfection when in reality you just need to let it be what it is. That can be problematic in many areas other than pap treatment...trust me...I know.

My perfectionism is probably as bad or worse than yours... Feel free to take my advice or keep chasing and learning as necessary to prove it to yourself 

I think you have your question figured out now. In short the formula is a relationship defining pressure support (PS) as the difference between exhalation pressure (EPAP) and inhalation pressure (IPAP). You can use it to determine settings but you only ever need to set 2 of the 3 variables, the 3rd is determined by the other 2 variables using this formula.

[David Clark]

I looked a little bit into transitional/sleep onset apnea. This was helpful...not about the question I was asking but where my charts are concerned. 
What Is Transitional Sleep Apnea

[OpalRose]

Rubicon,
Discussion on PS moved here:

http://www.apneaboard.com/forums/Thread-...Discussion

[Valtor]

Sorry for using a quoted reply, but since this is an old thread I thought my question would be clearer this way.

...The EPAP pressure controls hypopnea and OAs. You would raise the EPAP until these cease.  The PS can correct inhalation flow limitations.   The limitations will show up on the Flow Rate graph on the top of the inhalation arc.  For practical purposes, a normal arc will mimic a sine wave (on the top).  Flow limitations will display as a plateau or (to me) like a cursive "r".  To overcome the flow limitations, you keep increasing the PS until the waveform looks close to normal.   It sounds easy, but the PS is a double-edged sword.  Increasing PS will cause CO2 washout, thus causing CAs.  So the bottom-line is to use as much pressure that is needed that is below the CA threshold...

Let's say one has managed to control for all except CAs due to CO2 washout, is this when we start resorting to stuff like adding a piece of filter to the mask exhaust port in order to retain more CO2?

[SarcasticDave94]

I'd think a better way would be EERS, standing for Enhanced Expiratory Rebreathing Space.

A link to the wiki on EERS

EERS WIKI