Auto EPAP algorithm reaction time for Aircurve ASV

[Michaely6]

I have coached a lot of users in using ASV, and there are significant differences between Resmed and Philips, but both benefit from optimizing the minimum EPAP pressure.  Starting with EPAP at 4 does work for many people, but EPAP tends to rise when apnea do not respond to pressure support, and the event usually flagged UA.   I see not reason not to optimize EPAP min to a level that mostly resolves OA events, then letting the machine do its job with CA and H.  We even find people suffering persistent hypopnea with ASV are better treated with higher EPAP and sometimes higher minimum PS.  There is one rule of thumb for ASV titration; in spite of the "general rules", people respond as individuals, and optimization may require trial and error.  

Over-simplification of the EPAP min setting will put many people at a disadvantage, and in my opinion a better objective is to set EPAP min in a way that it never varies more than 3-cm.

So from my understanding, EPAP min needs on Resmed ASV auto device can be less than the EPAP needs on a Fixed autoset CPAP and even on the EPAP on the VAuto since pressure support on the ASV attempts to solve obstructive apnea before having to increase the EPAP?

[SarcasticDave94]

My EPAP Min is 9, set just below my median.

How did you determine your EPAP when you titrated on the ASV? Because I notice that my EPAP doesn't change much no matter what I set it to (and yes it is in auto mode). If I set my minute to 4, the med will only be like maybe 5  and if I set it to 9, the medium will be maybe 9.5. I just wanted to know why the EPAP seems like it only stays close to what I set it to no matter what number it is.

I'm not sure what's really best for you, but sharing the reasoning and method behind my EPAP Min 9. Note that I'm on an ASV with COPD.

In my own very long newbie thread started on a DreamStation BiPAP, I transitioned to ResMed ASV. I posted my BPAP sleep study and Sleeprider and others commented on it. I used my doctor's script settings the RT from Apria had set as my initial, which I believe I edited some immediately. I did away with ramp entirely after 1 night, and I think I did a Mode change to ASV Auto from ASV. AB members and I looked at the data and I experimented with pressure bumps that included EPAP Min of 9.

You can visit my newbie thread here for reference if you want.

Keep asking and I'll keep answering as best as I can.

[Michaely6]

Thank you all for the feedback. Yeah sleeprider and a few others have really helped me throughout the years with my journey to PAP therapy so I appreciate all of you guys for contributing!

[SarcasticDave94]

PS my 9 for EPAP Min was set by myself after a bit of trial and error. I'm not certain how long it was, but I'd think probably a bit more than a week. EPAP Min 9 was self determined gauging the best overall consistent AHI numbers and feel. If it didn't feel acceptable, I kept editing after 2 day intervals.

Reference my current settings:
EPAP 9-13
PS 4-15
IPAP equals current value of EPAP + PS
Not implying these are good for anyone but me.

[SarcasticDave94]

I have coached a lot of users in using ASV, and there are significant differences between Resmed and Philips, but both benefit from optimizing the minimum EPAP pressure.  Starting with EPAP at 4 does work for many people, but EPAP tends to rise when apnea do not respond to pressure support, and the event usually flagged UA.   I see not reason not to optimize EPAP min to a level that mostly resolves OA events, then letting the machine do its job with CA and H.  We even find people suffering persistent hypopnea with ASV are better treated with higher EPAP and sometimes higher minimum PS.  There is one rule of thumb for ASV titration; in spite of the "general rules", people respond as individuals, and optimization may require trial and error.  

Over-simplification of the EPAP min setting will put many people at a disadvantage, and in my opinion a better objective is to set EPAP min in a way that it never varies more than 3-cm.

So from my understanding, EPAP min needs on Resmed ASV auto device can be less than the EPAP needs on a Fixed autoset CPAP and even on the EPAP on the VAuto since pressure support on the ASV attempts to solve obstructive apnea before having to increase the EPAP?

I'm under the impression EPAP should be capable of doing the air splint itself in reducing obstructive apnea. Can it be a lower setting than CPAP? Yes, I think so, possibly because of the setting ranges.

[Michaely6]

Thanks Dave

[SarcasticDave94]

Welcome, anything else just keep asking or comment on progress

[Sleeprider]

By PM Michael6 asked:

Hey sleeprider. 

So from my understanding, EPAP min needs on Resmed ASV auto device can be less than the EPAP needs on a Fixed autoset CPAP and even on the EPAP on the VAuto since pressure support on the ASV attempts to solve obstructive apnea before having to increase the EPAP?

I think it is important that questions like this remain on the forum for all to see, and generally will not reply by PM.  Obstructive apnea is not resolved by increasing IPAP pressure or pressure support.  All auto CPAPs are designed NOT to increase pressure during an apnea, but instead increase pressure after the event.  Just as we have seen in positional apnea, an obstructed airway cannot be opened with pressure, instead it is important to prevent the obstruction from happening in the first place.  The ASV and ASVauto protocols are shown below.  In ASV and ASVauto mode, EPAP min must be increased by 1-cm until OA is eliminated.  In auto mode, this will eventually happen, but as I said before, this optimization of the EPAP pressure is an important part of proper titration. Pressure support or raising IPAP will not resolve OA.

In the soft cervical collar wiki (see signature links), we show examples of someone with positional obstruction.  This example was resolved by use of a soft cervical collar rather than pressure, but the effect is the same; the OA event must be prevented, not responded to by the machine.

[Michaely6]

By PM Michael6 asked:

Hey sleeprider. 

So from my understanding, EPAP min needs on Resmed ASV auto device can be less than the EPAP needs on a Fixed autoset CPAP and even on the EPAP on the VAuto since pressure support on the ASV attempts to solve obstructive apnea before having to increase the EPAP?

I think it is important that questions like this remain on the forum for all to see, and generally will not reply by PM.  Obstructive apnea is not resolved by increasing IPAP pressure or pressure support.  All auto CPAPs are designed NOT to increase pressure during an apnea, but instead increase pressure after the event.  Just as we have seen in positional apnea, an obstructed airway cannot be opened with pressure, instead it is important to prevent the obstruction from happening in the first place.  The ASV and ASVauto protocols are shown below.  In ASV and ASVauto mode, EPAP min must be increased by 1-cm until OA is eliminated.  In auto mode, this will eventually happen, but as I said before, this optimization of the EPAP pressure is an important part of proper titration. Pressure support or raising IPAP will not resolve OA.

In the soft cervical collar wiki (see signature links), we show examples of someone with positional obstruction.  This example was resolved by use of a soft cervical collar rather than pressure, but the effect is the same; the OA event must be prevented, not responded to by the machine.

I asked this question on this post on page one but it must have been missed by you which is why I sent a PM . Thanks for the response. The reason why I asked this question was due to your previous comment when you said EPAP only increases on the ASV when apnea is not responding to pressure support so I must have misunderstood that statement cause the way that I took it is that pressure support will also target apneas if it needs to in order to prevent additional EPAP pressure from increasing if it does not have to which is why people can get away with a lower EPAP min on the ASV device compared to a fixed pressure support such as the VAuto. I believe I also read some titration guide stating that if IPAP fails to prevent apnea from occurring, EPAP will then increase as a last measure. Hypothetically, how should one go about setting their EPAP min needs if their min needed to avoid OSA causes expiratory pressure intolerance or aerophagia? This is a hypothetical question because I'm just trying to understand why all the benefits and ins and outs of ASV devices.

[Sleeprider]

The ASV does increase PS for every apnea event, and the ASVauto mode will increase EPAP if the apnea does not respond, to PS.  It appears that EPAP will rise for unresponsive UA (OA) and H events.  The Resmed ASV targets minute vent and if it falls below the recent patient minute vent. The Resmed is unique in that it does not have a setting for respiration rate or tidal volume targets, but adaptively learns the user's natural rhythm and volume and works to maintain that, through pressure support.  You can see the Resmed ASVauto response below.  During obstructive apnea, pressure support up to maximum PS is applied but the apnea does not respond. This results in a drop in minute vent and EPAP pressure rises.

Setting EPAP min properly can avoid the need to go through several apnea event cycles in future sessions or later in this session as pressure will eventually drop back to the minimum.  Like all titration, it is a trial and error process where the minimum setting is adjusted until the OA/UA events are (mostly) prevented.  As I mentioned earlier, in some cases this may be accomplished through positional therapy rather than EPAP pressure.  There is an element of art to this.