Does APAP work?

I asked my doctor about APAP a couple of days ago and she said she won't prescribe them because they don't work well. She says that the automatic adjustment in pressure comes after the apnea event has already occurred - too late to be of help.

I'm not convinced, but have little else to go on. Can anyone in the forum comment on their experience with APAP relative to CPAP?

schwawi wrote:I asked my doctor about APAP a couple of days ago and she said she won't prescribe them because they don't work well. She says that the automatic adjustment in pressure comes after the apnea event has already occurred - too late to be of help.

I'm not convinced, but have little else to go on. Can anyone in the forum comment on their experience with APAP relative to CPAP?

It's not supposed to fix the "current" event, it is designed to alter the pressure throughout the night to give you enough pressure to prevent most of the apneas. So suppose you set a lower limit of 6 and an upper of 8. If you have apneas at 6, the machine will auto adjust up to 8 in small increments to prevent future apneas. If you analyze the data youself you can also use the data to tweak your own pressure so that if you know the machine gets up to 7.5 every night, you can change the range to be 7.25 to 8.5 or whatever. The goal is to allow the machine some flexibility. As an example if you have a pressure of 10, getting an APAP with a pressure range from 4 to 15 wouldn't be good at all, since it would start each night at 4 and have to slowly increase. On the other hand if you set it to 9 to 12 the machine would have some flexibility.

Think about it this way... if you have a CPAP set to 10 and it works most of the time that fine. But now suppose you have an APAP for 9 to 11. One night you might need just 9.5 and the next you might need 10.5. The CPAP wouldn't adjust so you would still have a lot of apneas, but the APAP would adjust to 10.5 to help you on that night.

It seems to me that as long as it is used PROPERLY there is really no downside to a APAP. In fact an APAP set with the same upper and lower limit is just a CPAP (basically). My $0.02.

schwawi wrote:I asked my doctor about APAP a couple of days ago and she said she won't prescribe them because they don't work well. She says that the automatic adjustment in pressure comes after the apnea event has already occurred - too late to be of help.

I'm not convinced, but have little else to go on. Can anyone in the forum comment on their experience with APAP relative to CPAP?

For the most part, your doctor is correct.
APAP/Auto machines have to have "events" (indicators) to determine when to make pressure adjustments.......Leaks, Snores, Flow Limitations, Hypopneas and Apneas. To be "effective", the minimum pressure setting needs to be high enough to take care of almost all of the events. If it's set too low, it can take far too long for the machine to raise the pressure high enough......and by that time, there have been too many events taking place......and your blood oxygen can desaturate enough to be problematic. Most APAPs are handed out with their pressure settings set to 4 - 20 cm. (the full range of pressures).

On the other hand, APAPs can be configured in straight CPAP (single pressure) mode or to a more effective range of pressures (minimum pressure high enough and maximum pressure to a setting that can allow for some other events).

All APAPs and CPAPs have the very same insurance code......E0601. Since it is ultimately YOUR therapy and if you're planning to be in control of YOUR therapy, your doctor shouldn't have a problem with prescribing one. The doctors work for US......we're paying their fees through our insurance premiums and co-pays.
You can always purchase an APAP online with a straight CPAP prescription.
At the very least, get a FULLY data-capable CPAP (and the software to interpret the data)......which it appears you have with the Elite II.

Personally, I have several Autos but mainly use them in CPAP mode because the pressure changes tend to disturb my sleep. Others have used them with a range of pressures with no apparent problems.


Den

For the most part, your doctor is correct.
APAP/Auto machines have to have "events" (indicators) to determine when to make pressure adjustments.......Leaks, Snores, Flow Limitations, Hypopneas and Apneas. To be "effective", the minimum pressure setting needs to be high enough to take care of almost all of the events. If it's set too low, it can take far too long for the machine to raise the pressure high enough......and by that time, there have been too many events taking place......and your blood oxygen can desaturate enough to be problematic. Most APAPs are handed out with their pressure settings set to 4 - 20 cm. (the full range of pressures).

On the other hand, APAPs can be configured in straight CPAP (single pressure) mode or to a more effective range of pressures (minimum pressure high enough and maximum pressure to a setting that can allow for some other events).
Den[/quote]


This is all very interesting to me. Its pretty clear what triggers the APAP to increase pressure, but do you have any idea how the APAP knows to reduce it? Or does it stay at this higher pressure once the trigger to move up is recognized? Am asking because at higher pressures, I get central apneas which are just as bad.

Here is my last night's example of APAP at work. Bear in mind that I know that I am much worse in REM sleep and being on my back also makes it worse. I woke up a few times on my back last night though I think I stayed on my side for the most part.

I am one of those who is not bothered at all when the machine increases pressure in response to event precursors which in this particular report seems to be flow limitations. Please ignore my crappy leak line. It is ugly but still within acceptable limits. I think my nasal pillows are getting tired and it is getting harder to keep a good seal.

Just look at the mostly pretty constant pressure with the exception of the one main increase. This report is a common occurrence for me. I need pressures in the 12 to 15 range maybe once or twice a night. I would much rather have a lower minimum pressure for the majority of the night and let the machine try to deal with the occasional increased pressure needs than have to use 12 to 15 constantly just to ward off the "maybe" events.

This regiment seems to work quite well for me. The pressure increases do not cause me to wake up. I don't use any exhalation relief. APAP isn't for everyone but depending on the individual and their pattern of event needs, it can be a very workable solution.

schwawi wrote:This is all very interesting to me. Its pretty clear what triggers the APAP to increase pressure, but do you have any idea how the APAP knows to reduce it? Or does it stay at this higher pressure once the trigger to move up is recognized? Am asking because at higher pressures, I get central apneas which are just as bad.

In the case of the ResMed APAPs, they will NOT increase pressures beyond 10 cm. to respond to a "frank" (sudden/abrupt) Apnea. This is because they use the "A10 algorithm". In ResMed's design and patent, it is their determination that 10 cm. is the threshold for Central Apneas. If you go to the Search line (above) and type in "A10", you'll find many, many threads where it has been discussed (or argued).

Each company has their own algorithms to deal with different events and how (and when) they increase and decrease pressures.

If you're susceptible to Centrals, it would be questionable (in my opinion) as to whether an Auto would be in your best interests or be of much benefit.

Do you have a prescribed pressure? (I presume you do since you have a machine listed in your profile)


Den

schwawi wrote:Its pretty clear what triggers the APAP to increase pressure, but do you have any idea how the APAP knows to reduce it? Or does it stay at this higher pressure once the trigger to move up is recognized?

If you see my report you will see that the machine will drop the pressure when it feels it is no longer needed.
Respironics address these things a little differently than ResMed machines. I don't know all the technical jargon but basically it "tests" with its sensors and pressure probes if the potential event triggers are still present or if there is any response. Sometimes it will switch automatically to CPAP mode for 15 minutes if it feels that it is unsure of what is going on (ie a common non response or possibly a central).

Once it senses that the higher pressure is no longer needed it will drop in increments so as not to disrupt sleep.
For a really technical explanation you will need to do some reading or wait for someone that understands the inner mechanics much better than I do and can verbalize it better. I understand the concept, I just can't put it into words well.

I don't have any history of central apneas. This is another reason why I am comfortable giving my machine its lead.
If I had a history of centrals I wouldn't want to let it go chasing things willy nilly. I would be more inclined to use the machine with a very, very narrow window which would be very close to CPAP mode and then watch data very closely.

My $0.02 worth using CPAP for 17 months and an APAP for 5 nights (gather new data sorta like a mini sleep study). Titrated to 10 which caught all my events and maintainted Sp02 at 92%, so I ended up with CPAP set to 11 (I'm assuming they thought I might sleep better at home so upped pressure by 1 with followup appt in 60 days to evaluate progress); unfortuately, my machine is not an efficacy data machine only compliance date...I was too muddle-headed at the time to understand anything more than that I needed CPAP therapy...BIG MISTAKE!!!

The goal of APAP machines is to deliver the least amt of air that maintains your normal breathing patterns. It calculates the air it delivers based on a rolling 5-breath basis; this allows the device to pick up subtle variations and respond appropriately. If flow limitations occur, the device increases pressure in an attempt to abort the potential event. ResMed machines do not chase events beyond a pressure of 10 on the theory that 10 is the theshold for creating 'high pressure' centrals. After a ResMed machine reaches 10, it will not increase pressure for that event yet it still continues to monitor your 5 rolling breaths for flucuations, so if you need more pressure to maintain your breathing pattern it will increase pressure up to the max set in your device. After it reaches 10 for an event, over the next 20 mins it reduces pressure to get to the lowest pressure needed to eliminate events (its goal). More knowledgeable users can correct this if I have this wrong. I understand that Respironics uses the 90thcentile as opposed to RedMed's 95thcentile.

Personally, I loved the so much easier breathing on an APAP, so much less pressure to exhale against! Now, my pressures are moderate, so this might not be the same for folks who require more pressure to stent open their airways. Because I've lost so much weight, my airways have been physically changed, thus I need different pressure to eliminate events. Over my 5 nights, my 95thcentile (where 95% of the time it delivered up to this number) varied from 6.9 to 9.8 (I did go higher but that was in that 5% of the time not reported), less than my CPAP setting of 11. While my CPAP has been re-set to a lower pressure, I am still having events and arousals.

I also had a lot of reported leaks. To try to eliminate the most obvious source, I have switched from my minimal nasal pillow OptiLife mask (which I love) to the Hybrid. Only had it for 2 nights and it seems to have taken care of the leaks BUT without efficacy data, I'm guessing.

Wulfman wrote:

schwawi wrote:This is all very interesting to me. Its pretty clear what triggers the APAP to increase pressure, but do you have any idea how the APAP knows to reduce it? Or does it stay at this higher pressure once the trigger to move up is recognized? Am asking because at higher pressures, I get central apneas which are just as bad.

In the case of the ResMed APAPs, they will NOT increase pressures beyond 10 cm. to respond to a "frank" (sudden/abrupt) Apnea. This is because they use the "A10 algorithm". In ResMed's design and patent, it is their determination that 10 cm. is the threshold for Central Apneas. If you go to the Search line (above) and type in "A10", you'll find many, many threads where it has been discussed (or argued).

Each company has their own algorithms to deal with different events and how (and when) they increase and decrease pressures.

If you're susceptible to Centrals, it would be questionable (in my opinion) as to whether an Auto would be in your best interests or be of much benefit.

Do you have a prescribed pressure? (I presume you do since you have a machine listed in your profile)


Den

Thanks for your response.

My prescribed pressure is 8. In the past, I was set and 10 and 11, and both resulted in higher AHI over an extended period of time - which I concluded to be due to central apneas since I was getting worse as more pressure was added. I suspect I could benefit from an APAP in a narrow range, say 8 - 9.5. Once I get my CPAP software so I can track my own nights, I think I will have a better idea.

I thought that ResMed APAPs will not increase the pressure above 10 in response to an apnea, to avoid chasing centrals, but that they will go above 10 (up to the set maximum pressure) in response to flow limitations or snores. And from what I understood, ResMed APAPs do not ever respond to hypopneas.

Am I wrong?