Adjust Settings or Leave Them Be?

[Melman]

For the past 30 nights my average AHI has been 1.17 with the values below 3 for every night except 1 (AHI 11.8). The values were below 1 for 19 of the 30 nights. The RERA average has been 0.39 and my RDI has never exceeded 3 (with the exception of the one night with the AHI of 11.8) My therapy is definitely effective but I wonder if there may be some benefit to making some minor adjustments.

As my profile shows, my min. and max. pressure settings are 8 and 14 and I have EPR set full time at 2.

My average 90% pressure for the last 30 nights has been 11.4. Based on the rule of thumb I have seen stated repeatedly in the forum my low pressure setting should be 9 (or 9.4?). My average pressure for the period has been 10.71. So would it make sense to increase the low setting to 9 or, alternatively, change the EPR to 1?

Pressure has risen to 14 on 16 of the 30 nights. So would it make sense to increase the max setting to 15? 

The practical side of my brain says “why fix what ain’t broke”. The OCD side says “play with those settings to optimize the results”.
Which side should I listen to?

Comfort is not a concern. After CPAP with a constant pressure of 10 I doubt I would notice a 1cm increase in initial pressure.
 
I have attached screenshots from three typical nights.

[justMongo]

Melman: Quite difficult to read when you attach the screenshots. Linking to a photosharing serive permits higher resolution.
I really need to read the numbers in the left column.

At first glance, things look good. You have some periods of high leak. And flow limitation is driving your pressure up.

[Melman]

Whoops! Sorry about that. How  are these?  (Reminder to self; post linked BBC code, not BBS code.)

[justMongo]

Good by the AHI numbers. You have good TV, RR and MV. It's not critical that you do so, however, if it were me, I'd inch up the Min Pressure a bit at a time. Likely end target would be around 10 cm-water. The flow limitation would be suppressed.

Leak rate isn't bad. It looked too high until I saw your vertical scale was 0 to 4.

Summary: Things look pretty good. You might experience a "smoother ride" with a higher min pressure.

[Sleeprider]

Your pressures are currently being driven by flow limitations that arise from too low minimum pressure. Your median is around 11 cm and your 90% is 2-cm higher at 13. Your Resmed machine is more forgiving of this than a Philips. If you were using a dreamstation, we would need a minimum pressure of 10-11 to avoid events; on yours 9 should do.

At this point we are improving on what is already good results, so try 9.0 as a minimum, and I think that should work pretty good. After this, any tweaks are going to be in fractional cm H2O increments.

[Melman]

Thanks JustMongo and Sleeprider.

I was pretty sure an increase in min pressure is the right thing and appreciate the confirmation. Obviously I'm still learning or I wouldn't have considered possibly increasing the max pressure as well at this time. It's clear from the graphs that the pressure fluctuations correlate with the changes in flow limitations.

I'll go to 9 starting tonight and let you know in a week or two how it looks.

[Sleeprider]

As you know, your results can sometimes be deceiving due to a tendency for your airway to close if you get into a position that obstructs the airway.  For you, that will always be a part of the solution.  So we may not be able to attribute everything to pressure, but I think you have worked on this with the buckwheat pillow, and a little additional pressure may give you a head-start on potential events.  

Your help to other new members with this problem has been appreciated.

[Melman]

I agree. It's clear I still have flow limitation issues. It seems the buckwheat pillow isn't the complete solution. It works well if I can stay on my side but more and more I'm finding that I roll onto my back and the pillow configuration for side sleeping is not as good for back sleeping. I may try a soft cervical collar next. (The tennis ball in the back of PJs doesn't appeal to me. It seems rolling on to that could be as disruptive to sleep as some the events we're trying to prevent. )

Thanks again

[Marillion]

I use a relatively flat memory foam pillow that I purchased from Costco and it seems to work well for shifting positions but offers enough support and is not too high to make my chin flip forward if I flip onto my back from my side.

[Melman]

At this point we are improving on what is already good results, so try 9.0 as a minimum, and I think that should work pretty good.  After this, any tweaks are going to be in fractional cm H2O increments.

Fourteen nights have passed since I increased the minimum pressure from, 8 to 9 so I’m reporting back as I threatened.

There has been essentially no change in my AHI but the distribution of events has changed. It appears that many of my OAs have been demoted to Hs, which I suspect, is a good thing. The figures below are averages.
                          H               OA                  CA              AHI               RERA               RDI
P 8-14              0.39          0.22              0.11              0.81              0.51                  1.32
P 9-14              0.56          0.14              0.11              0.84              0.70                  1.54               

My average and 90% pressure values since the change (again averaged) are 11.41 and 12.04 respectively.

What surprised me was the 38% increase in RERAs. I would like to reduce them and get rid of more of the Hs if possible. I know I may already have better numbers than many but I would like to get the RDI consistently below 1. Fortunately there's been no increase in CAs.


Would it make sense to change EPR from 2 to 1 or increase minimum pressure by 0.5? I think  I would be comfortable with either.