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:
SuperSleeper Wrote: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.
mjbearit Wrote: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.
archangle Wrote: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.