[CPAP] Pros & Cons of using ASV for plain old obstructive sleep apnea?

[JoeyWallaby]

Assuming one doesn't have any of the contradicted conditions listed by ResMed & Philips in their documents and ignoring the high cost of ASV, is there anything to be gained in using ASV for treatment of plain obstructive sleep apnea vs auto CPAP and auto BiLevel?

[ApneaQuestions]

It all depends how you define "plain".

[JoeyWallaby]

I'm referring to it as almost entirely obstructive events and very few to no mixed or central events.

[Geer1]

I imagine I might know where this question is coming from. 

I had one potential concern as I thought these were to some degree ASV ventilators but in reality they are just based on the same theory and have some neat assumptions/programming that requires respiratory drive by the patient (namely being that the patient sets their own target minute volume based on a reduced rate of their previous breathing. If you hooked someone that actually needed ventilation to one of these machines there is a chance they would eventually die as the target minute volume would just keep dropping until they were no longer able to function. You can kind of see this earlier in the night when your minute volume starts out higher as transitioning to sleep and keeps slowly dropping until eventually your natural sleep breathing sets a steady state.

It is ultimately a mixture of EPAP, PS min and the patient's respiratory drive that set their target volume. I think in theory it might be possible to set PS min a little too high and cause higher minute volume but not sure that would have any significant issues, maybe discomfort or aerophagia. 

The waveform analysis and increasing EPAP to deal with OAs, snore and flow limitations adds a neat twist as well which would work to stabilize breathing and maintain minute vent at a level that your body just stops struggling to breath. Without this part of the programming your minute vent could fall a bit lower then you would want it but that causes flow limitations etc which in turn raises epap which raises minute vent and thereby minute vent target on the machine. 

I think any possible downsides to Aircurve ASV, as this is the programming functionality I am referencing, are likely minor issues as the backup rate and minute volume compensation would be the two main concerns. I think in most OSA patients a bilevel like VAuto should be enough and ASV is overkill but in some cases like people with severe flow limitations especially ones that are significantly worse say in rem could see advantages with ASV.

I am just talking theoretically as I don't have the personal experience. I am also curious what some of the more experienced members thoughts are on this.

[SarcasticDave94]

My memory isn't up to task in the details, but I'm thinking this was discussed in other threads and there was a reason an ASV wouldn't make a good CPAP substitute. And I think that reason included both running in CPAP mode like my AirCurve 10 can do or setting it to emulate CPAP or BPAP. Part of the issue is probably from not being able to turn off the backup rate on mine.

[70sSanO]

I would not be surprised if a number of years form now, typical CPAP therapy will be an ASV. When it comes to CPAP therapy, we are probably still in the dark age.

I see no downfall to its use as it anticipates the breathing pattern and is able to respond at a faster rate than an APAP. I have used both CPAP (13 years) and APAP (5 years), I have not used any other Bi-Level. I did not use any EPR with CPAP nor APAP as my results always suffered.

At low pressures where the max is well below 10, it might be a moot point and straight CPAP may be fine. At higher pressures, APAP can add comfort, but the response time is sorely lacking. I wear a cervical collar because I drop my chin. With an APAP, no matter the settings, I still had horrific obstructive events when I started to drop my chin. With my ASV and without using my collar, I had no obstructive events. The downside without the collar was having a disruptive sleep, so even with a sub 0.5 AHI, I felt tired. I wear one with my ASV.

Finally, I do have some central apneas, but not at a level that would be a slam dunk for an ASV. Most nights my centrals were 2.0 to 3.0 (were 1.5 for years), although they would jump significantly higher at times. My obstructives were generally 1/4 to 1/3 of the centrals. With my ASV, I am averaging 0.7 AHI with 99.9% of the events as hypopneas. It would be difficult to convince me that I would have not done just as well, if not better, had ASV technology been available in 2001.

John

[ApneaQuestions]

I just posted this
http://www.apneaboard.com/forums/Thread-...#pid326991

It shows why I think ASV is a "win" for everyone with or without centrals. In my case I was chasing RERA-like flow limitations.

[slowriter]

I just posted this
http://www.apneaboard.com/forums/Thread-...#pid326991

It shows why I think ASV is a "win" for everyone with or without centrals. In my case I was chasing RERA-like flow limitations.

But is the latter (your case, and mine) really "standard OSA"?

[ApneaQuestions]

Agreed.. that's why my first response was 'It all depends how you define "plain"'.   ;-)

I'd imagine that anyone who suffers from OAs must also sometimes suffer from RERA-like flow limitations too.
To me it's a continuous spectrum of phenomena.

[JoeyWallaby]

My memory isn't up to task in the details, but I'm thinking this was discussed in other threads and there was a reason an ASV wouldn't make a good CPAP substitute. And I think that reason included both running in CPAP mode like my AirCurve 10 can do or setting it to emulate CPAP or BPAP. Part of the issue is probably from not being able to turn off the backup rate on mine.

What issues does the backup rate cause?