CPAP versus APAP

skjansen · Post by **skjansen** » Thu Jul 10, 2008 3:11 pm

Can someone please explain why I might be better off with an APAP machine versus a straight CPAP? My current CPAP is set a 13 cm and I believe the doc prescribed this back in 2004 when I first got my machine becasue he thought that an auto CPAP would not react quickly enough to my apneas. Does that make sense to any of you?

It seems like to me that an APAP like the Resmed S8 would be great.

Just interested in knowing a little more about machines other than just a CPAP.

All feedback is appreciated!

Guest · Post by **Guest** » Thu Jul 10, 2008 3:22 pm

Because with APAP, you can CHOOSE what settings you want to use - Auto, straight cpap, cflex, aflex, no flex....

I PREFER straight CPAP, but I have the OPTION to change my mind, or self-titrate.

Also, APAPs come with data capability (at least, all the one's I've read about).

I like CHOICE. I like being able to self-titrate as my health/weight/climate changes.

Why not get the best quality machine you can, when the price difference out of pocket is so minimal? To me, it's like getting the stripped down model car - you still will be going out and buying carpeting for the floor, a nicer stereo, fancier whooziwhatsits. If the price difference is small, go for the better model!

Cheers,
Babs

echo · Post by **echo** » Thu Jul 10, 2008 3:24 pm

my sleep doc said the same thing, but then why would they make APAPs at all if they couldnt respond to the event? So no, I dont beleive that. However , some people do sleep better with a straight pressure than with auto adjusting pressure. That said, others do better on an APAP.
With an APAP, you can always run it in CPAP mode..
CPAPs also come in data-capable mode.

annie123 · Post by **annie123** » Thu Jul 10, 2008 7:02 pm

I demanded an auto when I lost weight (110 lbs. total so far) and the pressure on the straight C (at 80lbs. lost) was blowing too hard. The auto ended up being set too high too after more weight loss, but I adjusted the top pressure and things are good again.
So my reason for the auto was weight loss and continued weight loss. I wanted to avoid another sleep study, and the auto figures things out for me w/o the expense and pain of another sleep study!

ozij · Post by **ozij** » Thu Jul 10, 2008 7:18 pm

Originally, APAP were touted as being capable of handling anything when set at the full range 4-20. That has turned out to be wrong - they are not as good at preempting as they were originally thought to be, and for the majority of users, an APAP set with a wide range is not fast enough. Additionally, some are woken up by pressure changes.

The doctor may also have seen things we don't know in your breathing pattern.

However, many of us APAP users have found that if the minimum APAP pressure is set rather close to the Rxed, we can be enjoy slightly lower pressure for most of the night, and yet have our apneas controlled.

If, however, you have obstructive apneas (without flow limitations or snores) occuring at pressure higher than 10, a Resmed is not a good idea for you, since a Resmed is programmed not to respond to apneas that occur above 10. You will have to rely on the Resmed's response to snores and flow limitations to raise your pressure.

If you get a chance to trial different autos, do so. Their response patterns are very different, and some people do much better with one auto than they do with another.

O.[/list]

echo · Post by **echo** » Thu Jul 10, 2008 7:37 pm

Hey Ozij -- You always have very good things to say and I always learn from your posts.
Why is it exactly that a large range prevents the APAP from reacting quickly? I never really understood that? I can understand if the minimum pressure isn't near the ideal pressure, but what does the max pressure have to do with it?

I mean assume I'm sitting at a minimum of 8 cm. My max is 20cm. If I have an event that needs, let's say 10cm, why would it take longer for the APAP to get to 10cm if it's set for 20cm max, as opposed to if it's set for 12cm max?

Is the Resmed limitation for preventing central apnea induced run-away? Do they not detect "apneas with cardiac oscillations" (=CA) like the P&B does?

DreamStalker · Post by **DreamStalker** » Thu Jul 10, 2008 8:23 pm

What ozij said.

The positive air pressure "prevents" obstructive apneas (when set up correctly) ... it does not undo obstructive apneas.

So, if your min pressure is set too low, it will not prevent the obstructive apnea ... the machine will sense it when it does occur and then begin to raise pressure but not necessarily dislodge the obstruction (your tongue). Instead what will happen is you will begin to suffocate and your brain will send a signal to your body to gasp for air and that is what opens the airway back up. The raised pressure will then hopefully prevent a future obstruction. However, if you do not have another obstruction, the auto algorithm will lower the pressure again back towards the minimum set pressure and the cycle starts all over again.

So set your lower pressure closer to your titrated pressure and the machine cycles less frequently.

ozij · Post by **ozij** » Fri Jul 11, 2008 2:20 am

echo wrote:Why is it exactly that a large range prevents the APAP from reacting quickly? I never really understood that? I can understand if the minimum pressure isn't near the ideal pressure, but what does the max pressure have to do with it?

You're right of course, echo. Only the min. pressure is relevant to this aspect.

Is the Resmed limitation for preventing central apnea induced run-away? Do they not detect "apneas with cardiac oscillations" (=CA) like the P&B does?

echo · Post by **echo** » Fri Jul 11, 2008 6:02 am

thanks for the clarifications

tangents · Post by **tangents** » Fri Jul 11, 2008 7:11 am

The positive air pressure "prevents" obstructive apneas (when set up correctly) ... it does not undo obstructive apneas.

HUH? Really? The increased pressure will not open the airway? I'm flabbergasted if this is true.

Thanks,
Cathy

tangents · Post by **tangents** » Fri Jul 11, 2008 7:13 am

Duplicate post!
Sorry,
Cathy

Needsdecaf · Post by **Needsdecaf** » Fri Jul 11, 2008 8:16 am

You know, I asked this question before I started CPAP and was told that with my readings and pressure (9) straight CPAP should do well.

Since I am running low 2's, high 1's consistently on my reports for total AHI, and feel comfortable with the machine, how would the auto pressure be able to help me?

What is the benefit to the auto pressure anyway?

Wulfman · Post by **Wulfman** » Fri Jul 11, 2008 8:56 am

tangents wrote:
The positive air pressure "prevents" obstructive apneas (when set up correctly) ... it does not undo obstructive apneas.
HUH? Really? The increased pressure will not open the airway? I'm flabbergasted if this is true.

Thanks,
Cathy

I generally agree with him.
If DreamStalker was talking about CPAP (single pressure) mode, then it COULD be true if the pressure isn't high enough.....and the event will take place anyway.
However, even with an APAP/Auto, the pressure increases are triggered by "events". If that event is an (obstructive) apnea, the machine will make several (three) attempts (Respironics APAP) to clear the event before it gives up. If the pressure is sitting at a point that's too low to get there in time, the event(s) will occur anyway.....but it's highly unlikely that it'll be able to do it in time to clear the first event. Lots of apneas are only about 12 seconds in duration......that's not a lot of time.

Den

Snoredog · Post by **Snoredog** » Fri Jul 11, 2008 10:41 am

skjansen wrote:Can someone please explain why I might be better off with an APAP machine versus a straight CPAP? My current CPAP is set a 13 cm and I believe the doc prescribed this back in 2004 when I first got my machine becasue he thought that an auto CPAP would not react quickly enough to my apneas. Does that make sense to any of you?

It seems like to me that an APAP like the Resmed S8 would be great.

Just interested in knowing a little more about machines other than just a CPAP.

All feedback is appreciated!

It all depends on what you are trying to fix.

Let's use your case as the example. You are on straight CPAP at 13 cm pressure for past 4 years.

What is it you are having problems with to wonder why a auto may be better?

Some of the more common reasons where an autopap might be helpful would be:

Suspect pressure needs have changed:
It's been 4 years since last PSG. A person may suspect their pressure needs have changed due to weight loss/gain, or time since last PSG, with a plain jane CPAP offering no therapy feedback how do you know that? You don't, you need a machine that gives therapy details or at least AHI and leak data.

Most autos can find your lab found pressure: Most autopaps on the market can find your 90% pressure found during a PSG within a few hours.

Difficulty tolerating therapy:
The most common problem seen with tolerating CPAP therapy is it keeps the patient awake. They lay there for 1 hr or more trying to fall asleep with an uncomfortable mask, breathing against higher CPAP pressure designed to be where it is at for the worst possible "condition", that is when they are asleep fully relaxed in REM at 4 or 5AM in the morning. It is 10PM they have 7 hours to fight it.

Use the Ramp:
Most doctors and DME's don't set this up for the patient. Most newbies don't know it exists or even how to use it. Then if they DO set it up, it is set up to fail.

If a patient is having difficulty falling asleep at 13 cm pressure they could make their life so much easier simply setting up the Ramp feature found on nearly every machine and using it. In your case, you could set it up to start at say 7 or 8 cm pressure over 30 minutes. Then once set up a simple press of the button enables it when needed. You don't have to use it every night, you don't have to use it at all but having it set up it is there, it is there to help you when you find you are 30 minutes into falling asleep still thinking the pressure blowing in your face is simply annoying. Press the button it is now lower, there is less noise from the machine, there is less noise from the mask, there is less pressure to exhale against. Lay there too long where pressure builds back up, simply hit the button again it starts lower again.

With an auto, the Ramp is automatic, set your low pressure where it is easy to fall asleep, where there is less noise and the auto will start there and return there automatically. Newer machines have Auto-Ramp which offers you even more flexibility and options, but overall they work the same offering you a lower pressure for greater tolerance especially falling asleep.

I spend half my time here "undoing" what many of the experienced here have done. They try to turn a autopap into a CPAP. Well if you are going to buy an autopap and set the Minimum to your CPAP pressure you just wasted a lot of money. It goes back to my very first sentence, depends on WHAT you are trying to fix.

IF a patients is having difficulty with CPAP, don't suggest an Autopap to them then set the Minimum pressure to what their CPAP pressure was, because you have accomplished NOTHING!!

If you do that, then about the only thing you can expect to gain is the ability to generate reports and monitor therapy.

it IS how you use it and what you are trying to fix. If an Auto can keep a patient on therapy where they were going to give up, then the auto has great value.

If you are without insurance, an Autopap is ALWAYS the best way to go. At any price the upfront cost is minimal over 5 years. You can see what your therapy is doing, there is no guessing that your pressure needs have changed, the machine knows that and adjusts on its own. If you change positions the machine will adjust up or down.

What Ozij and Dreamstalker say is true BUT use the Auto how it will benefit you the best not what it does for someone else.

Back to your 13 cm CPAP pressure. What was said about the machine NOT responding directly to Apnea above 10 cm is true, in fact it is true with nearly all the autos on the market. Some offer limited response above 10 such as with the Remstars or the 420e and I suspect some of the newer machines do also such as the Intellipap and Sandman.

But depending on your SDB, that may not matter, if you snore that will drive up pressure above 10 cm, if you have Flow Limitation, that may drive up pressure above 10 cm. Increase pressure where you eliminate all snore and/or all Flow Limitation and the chance of a frank apnea appearing is remote or not enough to worry about.

Use any pressure over 5 cm and you are probably restoring O2 levels back to near normal.

In the olden days they didn't have PSG's, they gave every patient a CPAP machine set to 10 cm and sent them on their way. And it worked fine for a lot of people, the ones that had difficulty handing 10 cm pressure didn't stay with therapy. It didn't matter if there was still residual apnea, pressure kept O2 levels up to acceptable levels. So what they had an AHI=12, machine didn't report that anyway.

Today you have more options for comfort, more options to remain on therapy, more options to make falling asleep easier.

jnk · Post by **jnk** » Fri Jul 11, 2008 12:56 pm

I hesitate to jump into a discussion among the big dogs, but all that you longtime posters are saying to each other on this subject is so informative to me that I need to at least try to ask some questions that your discussion has raised in my mind. I know you are discussing CPAP vesus Auto-PAP, but how does it all apply to auto bilevels, like the VPAP Auto, then?

In the manual for the ResMed VPAP Auto, the "10 cm" figure is described as a "conceptual" number called "AutoSet pressure," which I think is just a fancy way of saying 'the midpoint between ipap and epap.' So does that mean that if a person has the pressure support set to 4 cm (which would keep what I believe would be the standard protocol of 4 cm between actual ipap and epap), the machine would only raise epap to 8 cm in reaction to an apnea, instead of 10 cm?

And doesn't ResMed's general theory and approach with its auto bilevel algorithm hinge on the fact that it assumes flow limitations will generally precede most apneas, and that that will get the pressure up? Are some of you saying that isn't working in practice?

And if a patient can read his/her AHI number every morning, wouldn't it quickly become clear whether the machine was, or wasn't, reacting to events quickly enough, so that the person could then decide to try a narrower range between maximum ipap and minimum epap?

If those questions are too off-base to answer, I will understand.

BTW, I just this moment got a call from my DME that they aren't gonna be able to get the promised VPAP Auto out to me until next week sometime. They say they accidentally ordered the wrong machine! Poor people. They must be very busy over there.

jnk

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): resmed, CPAP, DME, AHI, auto

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): resmed, CPAP, DME, AHI, auto

CPAP versus APAP

CPAP versus APAP

Re: CPAP versus APAP