CPAP versus APAP

[Sleepster]

From my experience, I've learned that pressure needs definitely do change over time as well as during any one night. The APAP adjusts to those changing needs, and in the process tells me and my doc what those values are. Meanwhile, the CPAP cannot either adapt to those changing pressure needs or keep the pt. and his/her doc informed about what they are!

A good CPAP can keep the patient and the doctor informed about changing pressure needs.

[Sleepster]

I've only used a CPAP for 11 nights and certainly am not an expert. My family Doc has tremendous cred with me and he strongly recommended the sleep doctor. I do feel obligated to follow their advice, especially since it has worked very well and I am in the first 30 days of compliance testing...

You make a very good point. You don't want to go making changes and then get stuck having to explain to your doctor that you screwed things up.

If the settings are working for you, and your doctor agrees, then don't change them. If they're not working, and your doctor agrees, let the doctor recommend the changes.

After you've had a few months of successful CPAP therapy, and you feel like you might want to tweak things a bit on your own, well that's a totally different conversation.

[archangle]

God, I hate "meta studies" like this masquerading as real research.

Inaccuracy is induced because of possible selection bias of which studies get chosen to be included. (Either deliberate or accidental.) Each study has it's limitations, inaccuracies, and bias. While the limitations and inaccuracies may be mentioned and explained in the individual articles, these warnings get lost in the overall study. The bias in the individual study is almost always hidden, and it takes a lot of effort to dig it out.

If some of the studies have methodological problems, they skew the results. Now, in order to find the problems, you have to go through 24 different studies and figure out what's wrong with each one.

There are just so many things that can be wrong with the individual studies. In particular, a lot of bad doctors will simply prescribe an APAP set to the maximum pressure range of 4-20 and never check up on the data. Is "stupid APAP" being compared to "smart CPAP" with an inlab PSG sleep study and followups?

[Dawei]

From my experience, I've learned that pressure needs definitely do change over time as well as during any one night. The APAP adjusts to those changing needs, and in the process tells me and my doc what those values are. Meanwhile, the CPAP cannot either adapt to those changing pressure needs or keep the pt. and his/her doc informed about what they are!

A good CPAP can keep the patient and the doctor informed about changing pressure needs.

Sleepster--You will have to explain to me how a good CPAP can do this without follow up sleep studies?

Also, showing my computer ignorance, I'd like to ask how one uses the "Reply with Quote" feature, since I haven't figured it out yet (still), thanks

[PaulaO2]

As for the Reply with Quote, you did it in your post. Just click the button and start typing away.

http://www.apneaboard.com/forums/Thread-...85#pid3285

[IDRIck]

God, I hate "meta studies" like this masquerading as real research.

Meta analysis is a very powerful research tool for aggregating data and analyzing trends across studies. Is it perfect? No. Is it highly valued and respected research within the scientific community? Yes. For those with an open mind, look at table 3 and you will see the results of 24 comparative studies. PAP therapy clearly reduces AHI and there is little difference in AHI reduction between APAPs and CPAPs.

[Sleepster]

A good CPAP can keep the patient and the doctor informed about changing pressure needs.

Sleepster--You will have to explain to me how a good CPAP can do this without follow up sleep studies?

Here's an example. At a pressure of 11 cm I was still experiencing about one night in ten with a AHI above 5. The AHI was dominated by CA's so the doctor ordered that the pressure be lowered to 10 cm.

BTW, this worked and I found that after a few months I was able to gradually raise the pressure back up to 11 cm and lower my AHI even further. My AHI now stays pretty much between 1 and 2.

Without a good CPAP this would not have been possible because without a good CPAP you can't measure your apnea and hypopnea indices.

[SuperSleeper]

There a BIG problem with studies like this. Arch is absolutely correct to say that we really don't have enough information from each individual study to determine whether each individual conclusion was without bias. Studies like this can easily be used to skew data, or actually "hide" data (by making you search deeply to get the real facts, while most doctors don't have the time to do that). So what happens is doctors take these types of study as a "positive indication" that APAPs are no better than CPAPs in lowering AHI. When the fact is that in most cases, that is simply not true.

Allow me to explain: To fully determine whether or not these individual studies (and therefore the summation conclusion in this article) is accurate, we'd have to fully examine in detail all the variables in each individual study that this meta study utilized.

I suggest that this study is mostly likely biased, because I know for a fact that one APAP study used in this meta study (as listed in Table 3) is the exact same study that was proven to be completely worthless in this thread. I'm talking about the APAP study by Dr. Patruno in 2007.

If the meta study authors didn't bother to look deeper to see that one of their component studies was completely biased, I doubt they checked that deep to see if the other APAP comparative studies were done without bias either.

Also, if you look at this meta study, it's comprised of primarily OLD studies, back when APAP machine algorithms were less effective than they are today. Using older APAPs was one of the problems I had with Dr. Patruno's study. He didn't use newer APAP machines at all, plus his study was done in 2007, and he used an APAP machine that was 5 years old at that time (from 2001). His conclusions were based on old APAP technology that is now nearly 12 years old. And that's not the only one in this meta study.... if you look at Table 3, the other studies used were done in 2000, 2009, 2007, 2008, 2004, 1998, 2003, 2007, 2006, 2007, 2003, 2001, 2004, 2003, and 1997. This meta study has no supporting individual studies that were done using modern APAP machines.... NONE.

From that linked thread where we previously discussed Dr. Patruno's study [HERE], I re-post the replies that shed some light on his particular study:

This study is WORTHLESS.

The major issue I have with this study is that it was designed from the start with conditions that will automatically favor constant-pressure CPAP over Auto-CPAP (APAP) in the outcomes. Hardly a truly scientific study, IMHO.

Two points that prove the bias of this study against APAP machines:

1) Please note this statement from the article: "In this study, fixed CPAP was set at the level determined during titration study, while APAP was set so as to deliver pressure levels from 4 to 15 cm H2O." The problem with this is that (as jdireton pointed out), these APAP pressure ranges are nearly "wide-open" - meaning that there is a very wide range of pressures where the machine is allowed to operate (spanning 11 cmH2O altogether). It's quite known that Auto-CPAP is MUCH more effective at reducing AHI when the range of pressures is tightened up closer to something like 2 under and 2-3 over the titrated pressure. (in other words, if the patient's titrated pressure was 10, the best APAP pressure range for most patients would be 8-12 or 8-13). By operating in such a wide-open pressure range of 4-15, the study participants are bound to have less effective treatment from APAP. This is a biased baseline point that they should have accounted for, but did not.

2) In this study, those who used APAPs were given VERY OLD AUTO-CPAP MACHINES. They state for the auto-CPAP patients, they were using a ResMed AutoSet T, which came out in 2001 for goodness sake! The APAP algorithms and technology has improved dramatically since that machine came out 10 years ago! Please note that this article was written in 2007, and even then, the AutoSet T was older technology.

Again, they seemed to intentionally design the study to come to the conclusion that constant-pressure CPAPs were better, but they can only do that by stacking the deck against APAPs, both in pressure ranges and by using older technology.

Sad attempt... and I almost wonder what agenda they have in doing such a biased study.

From beginning of article:
"However, no data are available on the effects of APAP on cardiovascular risk factors"

From the end of the article:

"Conclusions: Our results suggest that CPAP and APAP, despite significant effects on OSA indexes and symptoms, do not improve cardiovascular risk factors in the same fashion."

That means everything in between is bad science.

It sounds to me like the conclusion should be "Fixed CPAP properly set by a skilled clinician in a PSG sleep study and titration usually gives better results than an APAP set at 4-15 cmH2O."

Unfortunately, it didn't compare fixed CPAP to optimal use of an APAP, i.e.

1) APAP set by a skilled clinician to a proper pressure range for the patient based on a PSG sleep test and titration, or

2) APAP set by a skilled clinician to an proper pressure range based on apnea and airflow data collected by an APAP machine during actual home usage over a period of time.

They should also throw in:

3) Manual CPAP with the average doctors, sleep labs, study, DME, insurance, and followup care an apnea patient is going to receive.

So, I conclude that this meta study is not something we should consider as unbiased and it's definitely not authoritative nor conclusive proof of anything other than the fact that the authors of the study didn't do their homework.

I still hold to my opinion that if used correctly, a modern Auto-CPAP machine is vastly superior (for most OSA patients) in lowering AHI.

[Sleepster]

God, I hate "meta studies" like this masquerading as real research.

Meta analysis is a very powerful research tool for aggregating data and analyzing trends across studies. Is it perfect? No.

You both agree on what I think is the important part of this: It's important to think critically about the results of any study. The naive acceptance of the study's results, without due consideration of the methods used to arrive at those results, is a very dangerous way to proceed.

Is it highly valued and respected research within the scientific community? Yes.

I think this depends on which faction of the scientific community you consult. But I take your point.

For those with an open mind, look at table 3 and you will see the results of 24 comparative studies. PAP therapy clearly reduces AHI and there is little difference in AHI reduction between APAPs and CPAPs.

It may be that for the treatment of OSA with no complications the only real advantage of APAP's is the comfort they provide to patients who require higher pressures. APAP's allow them to spend more time at lower pressures.

[Dawei]

A good CPAP can keep the patient and the doctor informed about changing pressure needs.

Sleepster--You will have to explain to me how a good CPAP can do this without follow up sleep studies?

Here's an example. At a pressure of 11 cm I was still experiencing about one night in ten with a AHI above 5. The AHI was dominated by CA's so the doctor ordered that the pressure be lowered to 10 cm.

BTW, this worked and I found that after a few months I was able to gradually raise the pressure back up to 11 cm and lower my AHI even further. My AHI now stays pretty much between 1 and 2.

Without a good CPAP this would not have been possible because without a good CPAP you can't measure your apnea and hypopnea indices.

Sleepster-- I'd like to respond to your latest on having a good CPAP. So, now I understand that by a "good" CPAP, you're referring to one that is data capable. Okay. In your own case, the doc decided to lower the pressure by 1cm, from 11 to 10 after seeing some AHI numbers above 5. Glad the doc's guess about your needed pressure change worked. But just because a CPAP is data-capable doesn't mean that the doc (or the pt.) knows where to move the pressure for better results.
My second sleep study after 5 years showed I needed a pressure of 11, up from the 7cm I had prior. I had a new S9 Elite. After the change to 11 per the sleep study, I continued to have apneas. So, the doc moved me up to 12cm. Same problem--snoring inside the mask and body struggling with events (reported by my wife) and confirmed by the data printouts from the S9 Elite. Back to the doc who then moved it up to 13cm. Still the same problem. It got to a point where the doc didn't know what to do other than another sleep study. I said no thanks, due to the recent one having failed to find the correct pressure as well as the cost of a study. I suggested an Autoset as a loaner, and he agreed. When the Autoset titrated my actual pressure needs, the doc wrote a Rx for me to have one permanently. By the way, what the Autoset found is that I need in the neighborhood of 18-19 cm!
I don't know how long and how many trips back to the doc for him to guess at pressure changes it would have taken to discover through trial and error what pressure was right. And that's not to mention the $45 co-pay for each office visit as dictated by my insurance.
With a CPAP that is data-capable, you know your AHI numbers, as you said. However, knowing those numbers cannot always direct us to quickly improving them, which can slip into the area of guesswork.