Auto BiPAP fixed PS vs Auto PS - pros and cons?

[Stubert]

Hi,

I changed from APAP to BiPAP because of too low median tidal volume and mixed complex condition, which always left me tired, during the last year, eventhough AHI around 1.

My new machine is a Löwenstein Prisma 25S. It's capable of running Auto pressure support, instead of a fixed pressure support on Resmed AirCurve V10 Auto.

From my perspective, the auto PS, together with auto Trigger, and auto ramp time, must be the a better solution than the Resmed device?

I start the night on Epap 9 and PS 3, that gives me an tidal volume around 600ml after falling a sleep. During the night, P95 Epap will be around 11,5 and P95 Ipap around 15,5.

PS is going up and down between 3 and 6, and Epap and PS is changing differently, in relation too snooring or hypopnias. I see in Oscar that the tidal volume reacts quite good to the automatic changes in PS, and a fixed PS, of example 4, would leave me with a too low tidal volume at higher pressure and reverse at lower pressures.

My height is 190cm, so tidal around 600ml should be fine. I use an O2 ring and my O2 is quite stable with very few drops and a min around 92% (avg. 96%)

What is your opinion on auto PS vs fixed PS, I only see benefits of adding auto PS to the Bipap when a fixed Epap and Ipap is not a good option.

Am I just lucky that my machine has this option and most people on Aircurve V10 Auto have to make a compromise on finding a pressure support which lies in the middle of what is needed?

Thank you in advance.

[Sleeprider]

Several BiPAP machines use a range of PS like Philips and Lowenstein, while others use a fixed PS. Having used both, I think fixed PS is better because the algorithm that controls the variable PS is just not responsive enough to really solve problems, and it can be disruptive. BiPAP machines with variable PS are responsive, not proactive, so they really don't solve a problem on a breath by breath basis. That said, the champion of adaptive or variable PS is the ASV machine, which is also not my recommended choice for obstructive sleep apnea and upper airway resistance syndrome. A fixed PS that provides a therapeutically effective pressure support on every inspiration is better than a variable PS that may have a range both below and above the effective. If settings are optimized, the pressure support requirement should not change much, however there is an argument that changes in sleep position or stage may cause changes in PS requirement. My experience with variable PS was with the Philips BiPAP Auto machine, and I would consider that was a failure compared to the Resmed Aircurve Vauto.

Understanding that comfort and efficacy is often specific to an individual, I think the only way to really establish whether variable or fixed PS works best for you is to experiment with fixed PS (set minimum and maximum the same) and optimize for results, then compare that against variable PS. It seems your PS varies from 3.0 to 4.0, which is not a large range. Try fixing PS a t 4.0 and compare. What works best for you is best for you.

[Stubert]

Thank you so much Sleeprider. I understand your point of view and agree ,that a fixed pressure of 4 could be a solution, in order not to react all the time. I see the potentiel benfits of both solutions. When I look at the data, at a given pressure, sometimes 4 will be fine but another time, during the night too much or too little.

I am only 8 days into the new machine and will off course try out running fixed of 4, as I can see, in Oscar, that it should not be to far off, at epap 9 or higher. I will try it out and get back with data screenshot. One night I tried a fixed PS of 3,5 and that left me with too low O2 30% of the night, and brain fog all day.

Could PS 0,5 matter that much?

I roll from one side to the other quite a lot during the night, and avoid the back, at all cost, as it really gets ugly and no machine have a chance. I have 2 long pillows one each side of me, to support the back, wether left or right side sleeping.

My insp. and exp. also tends to change a lot, from short insp., and longer exp., to longer insp., and shorter exp. I would really like if you and other "specialists" could have a closer look to that later, now my machine is partly supported by Oscar, but as I see it, all data needed is there.

Happy new year and I will get back with some Löwenstein Bipap data!

[Sleeprider]

Our starting pressure range is not very different, and I have EPAP min 9.0, PS 4.0 and max pressure 18.0. I rarely see maximum pressure but often see EPAP pressure rise between 10 and 12. I have used these settings for at least 6 or 7 years and am considering a trial of higher PS based on recent results. Sleep position is not a problem for me, but it sure does affect a lot of the members on this forum, and one of the most common recommendations I make has to do with positional obstruction. As you observed, the solution is not more pressure, but to avoid it.

If a fixed PS of 3.5 cm was inadequate for your needs, then if you're going to use a PS range, it needs to be above that, and yes, a small increment of PS can make the difference between mild or moderate flow limitation and resolving flow limitation. Since you're using Oscar, you might want to correlate your flow limitation with PS and see if there is something to be learned there; however I don't think the Lowenstein tracks FL the same way. You might be able to use one of the user-defined flags (UF) for flow restriction. You can find that in the Oscar Menu under File/Preferences/CPAP. Just enable Custom CPAP Flagging and define the event you want to track. It could be 5% and 20% and Oscar will track reductions in maximum flow rate at those levels. This might help you optimize the minimum PS you need, and whether a higher maximum PS is needed or not.

[Stubert]

I tried some different settings for the past week and now had the best night so far in a long time. Attached Oscar data. My Flow limits are much less but still too much.Leaks rates not optimal but not terrible. I struggle to get them batter.
It seems I need more aggressive trigger, as start of breath is quite long and have a bump. Tidal volume and median a little on the high side? I am 190cm high, should be around 580 median?

Settings on the  Prisma 25S:

Bipap S mode (TriLevel)
Trigger "highest"
Ramp in "highest"
Ti 37%

I think the few CA's are falls flagged. My own take on the night is:

1. Change TriLevel to real BiLevel, for a more aggressive trigger in (see mask pressure data)
2. Lower epap from 10 to 9
3. Set PS to 4.5

I see my self benfit from the Resmed Vauto Bipap, as I can dial settings more in, in auto bipap mode, than the prisma. The drawback of the prisma is, that in auto S mode, I cannot set the trigger and ramp in timings, they can only run in auto mode. I tried it, and it does not turn well out, as some of the night is with high trigger but also some parts with medium triggger and long ramp. It simply cannot perform well enough, as I think I need high settings all the time.

The compromise for me now, is to find the best fixed setting in s mode, where I can set the trigger, ramp in time and Ti %.

[Stubert]

Attached 2 pictures of trigger in setting and ramp in.