ASV Epap vs PS correlation?

[Moemah123]

Thanks to everyone here, I feel I am at a phase where my therapy is getting so much better. I have a question and hopefully it is helpful to Resmed ASV users.

Is there a correlation between Epap min/max with PS min/max? I ask this question because my settings used to be 4-8 epap with 3-8 PS and I used to notice that median epap would be say 5 or 6 and IPAP would be say 14 median. However slowly increasing min epap I would notice that epap median would increase and IPAP is still 14 for example. Finally last night decided to push it so went epap 6.6 and I noticed now median is 7 but now IPAP is 10ish. I keep observing if I increase epap min to where last couple night median was, median numbers would increase by 1 while IPAP stays same or lower (which means less PS needed) 

So hopefully my description was clear and happy to attach examples. 2 questions I have. Why would increasing epap min require need for less PS 2. I personally feel better with increasing epap min while lowering PS from 3 to 2 and max to 7 from 8 and it seems I may even need less PS since median epap was 7 and ipap was 3. Any thoughts ?

[Sleeprider]

The first thing that needs to be pointed out is that what works for you, may not be appropriate for others. The individual response to pressure and pressure support will vary in both efficacy and comfort between different individuals. When you joined the forum, you were using ST therapy and had a surprisingly low AHI with fixed pressure at EPAP 5.0 and IPAP 10.0, so the ST was able to help you trigger breaths with only 5.0 cm. That is unusual for central apnea. With ASV, you continue to be able to use relatively low pressure support that would not work for everyone, but it works fine for you.

[Geer1]

Simple to explain assuming you have obstructive apnea. EPAP is what holds your airway open stopping obstruction from happening. Raising EPAP prevents airway collapse and reduces the amount of work the machine has to do to maintain your minute ventilation (these machines target 90% of recent/previous ventilation).

One of the misconceptions with ASV is that a lower EPAP is perfectly fine. We often see cases where a person has been titrated to 10+ cm min pressure on APAP or bilevel and then once they switch to ASV are told to start back over at 4 cm min EPAP allowing obstructive apnea to be present again. The responsiveness and power of an ASV allow it to blow open many of these obstructions and fight through them and in some cases this does allow a user to get by with a lower EPAP but it also means the machine has to work much more regularly to fight these obstructions rather than just fighting the central apnea (assuming that is the reason you use an ASV).

What you have done is figured out the minimum EPAP that helps avoid obstruction and minimizes the amount of effort the machine has to put in to maintain your target ventilation. In short you have optimized your therapy by preventing obstruction rather than trying to continuously fight it.

[Geer1]

Basics of PAP are as follows.

EPAP: Prevents airway collapse
PS/EPR: Provides ventilatory assistance through a restricted airway

Then with these ASV units you also get

Backup Rate: Tries to initiate a breath if you don't spontaneously take one
Variable PS: Changes machine effort to rapidly stabilize your breathing rather than relying on spontaneous effort to correct itself

[SarcasticDave94]

Hope this addresses some of your questions.

Assuming your ASV is in ASV Auto mode, you will have EPAP Min/Max and PS Min/Max, therefore both are ranges. Despite not being able to actively edit IPAP, it will be a Min/Max range as well. In ASV mode, EPAP becomes a static single pressure, no range available. Then all increases to pressure are in PS.

My belief is these three, EPAP PS IPAP, can each move about within their ranges semi-independent of the others. However, there's specific needs to consider. I believe EPAP will increase for Obstructive based events and PS for Central.

EPAP addresses base pressure (what you feel as soon as your start it), Obstructive Apnea and Hypopnea. And I felt it was more constant. This is your exhale pressure.

PS addresses the Central components. It felt like a short duration burst.

IPAP will be the sum of EPAP and PS, used for inhale.

You can move EPAP numbers to PS and vice versa to a certain degree and change how it feels. You need to experiment to see if therapy effectiveness is still good. It can get better or worse depending on what changes and by how much.

Possible problems, too limiting on PS can allow CA to increase.

[Moemah123]

Simple to explain assuming you have obstructive apnea. EPAP is what holds your airway open stopping obstruction from happening. Raising EPAP prevents airway collapse and reduces the amount of work the machine has to do to maintain your minute ventilation (these machines target 90% of recent/previous ventilation).

One of the misconceptions with ASV is that a lower EPAP is perfectly fine. We often see cases where a person has been titrated to 10+ cm min pressure on APAP or bilevel and then once they switch to ASV are told to start back over at 4 cm min EPAP allowing obstructive apnea to be present again. The responsiveness and power of an ASV allow it to blow open many of these obstructions and fight through them and in some cases this does allow a user to get by with a lower EPAP but it also means the machine has to work much more regularly to fight these obstructions rather than just fighting the central apnea (assuming that is the reason you use an ASV).

What you have done is figured out the minimum EPAP that helps avoid obstruction and minimizes the amount of effort the machine has to put in to maintain your target ventilation. In short you have optimized your therapy by preventing obstruction rather than trying to continuously fight it.

You are correct, I have complex Apnea and Sleeprider and Dave were kind to help me throughout. I guess what you mentioned about obstruction males sense. A follow up question is say today's median of epap is 7 I keep min at 6.4 but I want to know what would it mean if say today I set it to 7 and reported median comes back 7.6 or 8 for instance. Do I keep upping my epap min until at some point median never changes? And based on my observations does it mean central apnea is now managed but what I am helping with epap is keep obstructions away? So as long as machine reports low ipap everyday I should be happy to keep PS min and max as low as possible to get to median IPAP min / max?

[SarcasticDave94]

FWIW I myself wouldn't be editing pressure settings from a one day result. You may trap yourself with pushing pressures up when you maybe encountered a few days that your median pressure creeped up for whatever reason, but it might not have been your long term trend.

[Moemah123]

Basics of PAP are as follows.

EPAP: Prevents airway collapse
PS/EPR: Provides ventilatory assistance through a restricted airway

Then with these ASV units you also get

Backup Rate: Tries to initiate a breath if you don't spontaneously take one
Variable PS: Changes machine effort to rapidly stabilize your breathing rather than relying on spontaneous effort to correct itself

Hope this addresses some of your questions.

Assuming your ASV is in ASV Auto mode, you will have EPAP Min/Max and PS Min/Max, therefore both are ranges. Despite not being able to actively edit IPAP, it will be a Min/Max range as well. In ASV mode, EPAP becomes a static single pressure, no range available. Then all increases to pressure are in PS.

My belief is these three, EPAP PS IPAP, can each move about within their ranges semi-independent of the others. However, there's specific needs to consider. I believe EPAP will increase for Obstructive based events and PS for Central.

EPAP addresses base pressure (what you feel as soon as your start it), Obstructive Apnea and Hypopnea. And I felt it was more constant. This is your exhale pressure.

PS addresses the Central components. It felt like a short duration burst.

IPAP will be the sum of EPAP and PS, used for inhale.

You can move EPAP numbers to PS and vice versa to a certain degree and change how it feels. You need to experiment to see if therapy effectiveness is still good. It can get better or worse depending on what changes and by how much.

Possible problems, too limiting on PS can allow CA to increase.

Ok so question to you both. I believe i am following what you are saying but here is an example with numbers (Hypothetical) that I meant to drive at.

Lets say
Day 1 : Epap is min 6 max 10 with PS 1-6 for example so that means your min IPAP is 7 with max IPAP as 16. 
Day 2 : Epap is min 4 max 8 with PS 3-8 which means min IPAP is 7 and max IPAP is 16

My question to you both is given AHI is reported to be the same lets say below 1. And if oscar reports that max Ipap was 15 where obviously in both cases median EPAP would be different due to range difference. What does this mean? because likely one Oscar will show you need lower epap and other will show higher while one oscar will show you need lower PS support but the other higher. In this case 1 will be inclined towards obstructive and other central. Or is my example wrong to begin with? Hope i am making sense

[Geer1]

Don't chase perfection it will only make things worse. PAP treatment is a game of balance, the best results come at the lowest settings that treat majority of issues. If you surpass that point the increased pressure or PS os often more detrimental than helpful.

You will also always have good days and bad days, you try to treat the the average days and let the bad ones be a bit worse.

Your median EPAP will always be greater than min EPAP and if you chase eventually your machine will be maxed out. It is all about finding the minimum effective EPAP which it sounds like you pretty much did.

Max IPAP is not important and only exists momentarily.

Edit: One minor correction. Max reported IPAP is not important. Max PS/max IPAP settings increase the machines power and capability to treat central apnea in a timely manner. The higher PS range the more capability machine has. High PS can cause leaks or aerophagia in some people which are about the only reason to handcuff the machine with a lower max PS.

[Moemah123]

Thank you so much Sleeprider , Dave and Geer. You are right, I believe I found the settings that work for me hopefully for a long time. No more chasing, was educating myself and your responses are logical and helps me understand why slightly higher epap made alot of difference