CPAP versus APAP

[Ugly]

Rick--The sleep doc I see has mentioned to me that there is no "medical benefit" of an APAP over a CPAP machine. I understand that to imply that the CPAP is set at the proper pressure for the patient at that point in time.

I'm still waiting to duke it out with my doctor over the correct pressure. He said 8 was and is sufficient. After using an APAP for the past two week I just took a tally and averaged out the pressure readings and currently it's at approximately 10.42 - considerably different. In fact if he won't agree to upgrade my machine I'll just set it at that and see how it goes.

[IDRIck]

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.

I will agree that an APAP machine can provide relief from osa but disagree that it is vastly superior to a cpap. Perhaps in certain situations not yet adequately defined but to use "most" is a stretch IMHO. Can you provide references that demonstrate this superiority? I would like to read them. My AHI is 1.5 or less. Will an APAP change that? I don't see how it can nor do I believe there would any practical biological differences. If there are biological significant differences, you all need set the the docs straight since they believe 5 or less normal...

[JJJ]

I will agree that an APAP machine can provide relief from osa but disagree that it is vastly superior to a cpap. Perhaps in certain situations not yet adequately defined but to use "most" is a stretch IMHO. Can you provide references that demonstrate this superiority? I would like to read them. My AHI is 1.5 or less. Will an APAP change that? I don't see how it can nor do I believe there would any practical biological differences. If there are biological significant differences, you all need set the the docs straight since they believe 5 or less normal.

I haven't read any studies published in peer-reviewed journals about how superior an APAP is over a CPAP, but it seems to me that the main advantage is compliance. An APAP allows a lower initial pressure, which is easier for the patient to tolerate.

And having said that, APAPs have one disadvantage over a CPAP, assuming the patient's pressure has been properly titrated. I.e., APAPs supposedly adjust to whatever the patient needs, but in real life practice they do not react fast enough. Suppose your APAP is set to, say, a 10-16 range. You are cruising along happily asleep at 10, and suddenly you have an apnea that requires 14 cm. to overcome. The machine will take 20-30 seconds to get all the way up from 10 to 14 because it keeps trying in 0.5 cm increments, waiting for the software to evaluate the results each time. If you had been running a straight CPAP at 16 that event would never have happened.

I complained about the reaction time of my machine at my last visit with my sleep doc a couple of weeks ago. She immediately agreed that they don't react fast enough and suggested that I might want to set my machine to straight CPAP mode. I haven't done so yet, but I might eventually.

[PaulaO2]

The thing is, what will you do when your AHI starts creeping up? Since you run yours on straight CPAP, you will be wildly guessing as to if you need to increase or decrease. Your doc would be guessing as well. What about if you have a bad night? Like if you are taking a new medication? Or if you are having a good night and don't need 15? With the guessing, you'll be taking a minimum of 10 days between each change to see if it helps anything or not. If you are depending on your doctor to decide, it will be at least a month between visits and changes. That's time wasted.

An autoPAP can adjust for you, night after night after night. Just look at my own data. I had a dumb machine so I don't know what the AHI was but I felt awful. It was set to 12. I could have bumped it up to 13, waited to see if I felt better, then maybe bumped it up again, waited some more. Rinse, repeat. With my Autoset, I start the night out at 11 but spend most of the time at 13 with the machine going up to over 15 several times a night, sometimes nearly all night, sometimes not at all.

It is the same thing as with a diabetic. Very few insulin dependent diabetics inject themselves with the same amount, day after day. They use their glucose meter along with knowing that the heavy meal they plan to have will need more versus the light meal.

It is the same with doing exercises. If you want to get muscles all over, you don't use just one machine or one routine. You use several, varying them to get the best out of the sweat.

A regular CPAP can't adjust depending on what you need. Yes, the AHI will be below 5 regardless, but that's not the point. The point is you are probably not getting the best treatment. Your body will change. Your pressure need will change. An autoPAP can adjust to that. Along with the data, you'll be getting the best treatment you can possibly get. And that is the point to using a CPAP to begin with, isn't it?

[archangle]

If you don't realize that an APAP machine is superior to CPAP, you simply haven't been paying attention. Anyone who argues otherwise has to be comparing "dumb APAP" to "smart CPAP."

First, the APAP machine can always be set to run manually, or to a narrow pressure range. If you can't get equal or better results with an APAP machine, you need to step aside and let someone who knows something about CPAP do your job.

As to how to manage changing needs with a manual CPAP, you do it exactly like you do with an in-lab titration study. Periodically mail in the SD card, or use the modem if available. If AHI goes up or other problems occur, make small adjustments in pressure and study the results. Adjust pressure until you get good results.

If you have an Auto CPAP, do the same, but try a pressure range, and see how the patients results vary with pressure. You will normally get the "right" pressure in fewer tries.

In either case, if you can't get good results with "remote" tinkering, you still have the option of a sleep study, but don't forget sleep studies have LOTS of problems such as not sleeping, sleeping badly, high cost, and the fact that you're measuring the patient in a vastly different environment from his actual sleeping environment.

[archangle]

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.

Meta analysis is also a very powerful to to attempt to legitimize poorly done research by putting together a bunch of badly done studies. It's also a very powerful tool to manipulate results by introducing a selection bias.

Preparing a table of 24 badly done or irrelevant studies doesn't make the data any more correct.

[Sleepster]

The thing is, what will you do when your AHI starts creeping up? Since you run yours on straight CPAP, you will be wildly guessing as to if you need to increase or decrease.

Again, I don't wish to argue that a good CPA is better than a APAP. But the guessing is not wild. These are adjustments based on solid information. And when you think about, that's all a APAP is doing. It makes its adjustments using algorithms, and those algoritms are written by people who are making the same type of "guesses" you are talking about.

[archangle]

I haven't taken the time to dig into all 24 reports, but it's pretty clear to me that most of them are studying "APAP setup by monkeys" to "CPAP with followup by skilled professionals."

In one sense, I'll agree. If you set an APAP to a wide pressure range and ignore the results, you do not get better average results than a manual CPAP with pressure set in an in-lab PSG sleep test.

However, you can turn this around and state it the other way around. From this study, it appears that an APAP set wide open works as well as a manual CPAP properly set for the individual patient with proper followup care.

I looked at two of the studies.

1) d'Ortho used 6-16 auto on all of the APAP patients. No tuning to the individual CPAP users.

2) In D. Damjanovic, it's not clear to me what APAP pressure was used, but it sounds to me like it was set "full open" for all the patients.

I haven't felt sufficiently motivated to dig through all 24 studies, but for these two studies, it seems to me that you could draw the conclusion that "An APAP machine with neither initial pressure customization for the patient nor followup pressure adjustment works as well as a CPAP set for the individual patient's needs with followup adjustments."

If an unconfigured APAP machine with no followup care works as well as a CPAP with proper configuration and followup, just imagine how well an APAP will work if you followup and adjust the pressure settings to the patient's needs.

Or, if you want to twist it around the other way, you could claim "APAP is better for the patient because you can get equally good outcome without the expense and inconvenience of titration and followup pressure adjustments."

[Sleepster]

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.

If it were me I can imagine how I would have raised the pressure myself, eventually to 18. I agree that it's guesswork, but the APAP algorithms are guesswork, too.

I'm not trying to argue that a good CPAP is better than a APAP. Given the choice, I'd pick a APAP, especially if I were at a pressure as high as 18 cm.

However, if I've got a good CPAP, and my AHI is under control, I'm not going to go out and spend good money on a APAP.

In my case I'd be upgrading from a good BiPAP to a auto-BiPAP at a cost of lots of money. I'm not about to do that. However, if I can adjust my way to setting my BiPAP in CPAP mode, and it's time for an upgrade, I'd do everything I could to get my insurance to pay for a APAP, even if it raised my copay. And if I had no insurance and the choice was between a good CPAP and a APAP, I'd find a way to afford the few extra bucks a APAP would cost.

[Dawei]

JJJ wrote:

I haven't read any studies published in peer-reviewed journals about how superior an APAP is over a CPAP, but it seems to me that the main advantage is compliance. An APAP allows a lower initial pressure, which is easier for the patient to tolerate.

And having said that, APAPs have one disadvantage over a CPAP, assuming the patient's pressure has been properly titrated. I.e., APAPs supposedly adjust to whatever the patient needs, but in real life practice they do not react fast enough. Suppose your APAP is set to, say, a 10-16 range. You are cruising along happily asleep at 10, and suddenly you have an apnea that requires 14 cm. to overcome. The machine will take 20-30 seconds to get all the way up from 10 to 14 because it keeps trying in 0.5 cm increments, waiting for the software to evaluate the results each time. If you had been running a straight CPAP at 16 that event would never have happened.