AHI and XPAP Pressure

jrfoster · Post by **jrfoster** » Sun Feb 11, 2007 4:13 pm

I have been discovering that I seem to have a higher AHI when the pressure is higher than when at lower pressure. Last night for instance, when at a pressure of 9cm I had an AHI of 3.4. (At 9cm for 87 minutes) Then at 10cm of pressure had an AHI of 3.5. (At 10cm for 85 minutes) Then at 11.5 cm I had an AHI of 6.2. (At 11.5 for 301 minutes.) For a grand total of an nights AHI of 4.9.

Since I am new to the Encore Pro software, this is the first time I have been seeing this data. Do some folks find higher AHI's at a higher pressure or is it because I spent almost 5 hours at 11.5 while less than 90 minutes on the other lower pressures? I have my machine set at AFLE. Tonight I was going to try the range from 10cm to 12 cm to see the results. Any suggestions?

Jeff in TN

Linda3032 · Post by **Linda3032** » Sun Feb 11, 2007 4:25 pm

Hi Jeff. All you can do is experiment. Cflex on vs cflex off -- that might make a difference.

Are the AHIs mostly HIs or OAs? HIs usually indicate too low of pressure. OAs could be too high. Your Encore Pro (on the bottom of Daily Charts) and MyEncore show you what apneas you have at what pressures. You should check that out and adjust from there.

Just experiment and you will find your "sweet spot".

Linda3032 · Post by **Linda3032** » Sun Feb 11, 2007 4:30 pm

And in speaking only for myself, I use the pressure I feel the best at. My 90% pressure can run at 9 or even 10 (if I have my auto set that high). But, if I run at 9 or 10, my ears hurt and my face and eyelids get puffy (or puffier).

I run at 7 to 7.5, feel great, no ear pain, no puffiness, and keep my AHI below 5. I'm happy with that.

So, as you experient, keep comfort in mind.

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): AHI, auto

Wulfman · Post by **Wulfman** » Sun Feb 11, 2007 5:40 pm

Jeff,

One or two nights' numbers don't necessarily indicate a trend or conclusion.
I've noticed that it can take my system a couple of weeks to get used to a different pressure.
In my case, I experienced higher AHI numbers in Auto mode.....maybe not a huge amount, but somewhat. My Auto was chasing my snoring.....trying to kill that.....and in the process of raising the pressure I seemed to be getting more hypopneas and consistent apneas. I had my Auto in a range of 10 - 15. I also wondered if some of those events were a reflex action in my throat, caused by the pressure changes. Way back last March in '06, I bumped my fixed pressure from 10 to 12......and I actually had a hard time getting to sleep that night with a 2 cm increase in pressure. Consequently, when I did the trial in Auto mode, I reflected back and wondered if the pressure changes might be disturbing my sleep more. It only got to 15 for about 1 1/2 minutes on ONE night, but did hit 13 and 14 a bit. Given the fact that it was making multiple pressure changes (mostly) between 10 and 14......that's the conclusion I came up with. I eventually settled on 12 as it gave me the best overall results.

We're all different and all we can go by is our own personal experiences.

Best wishes,

Den

Goofproof · Post by **Goofproof** » Sun Feb 11, 2007 9:12 pm

Also what pressure range is your APAP set for? More than a 4 to 6 CM spread can cause higher AHI's. Jim

jrfoster · Post by **jrfoster** » Sun Feb 11, 2007 9:19 pm

Thanks for the tips Linda , Jim and Den. My pressure range was set last night from 9-11. Tonight I am trying 10-12. That range shouldn't cause problems since I can fall asleep easily with 10cm. The only problem I've noticed is that at the higher pressures my mask feels different when I breathe and leaks somewhat more. I will tighten the straps some but don't want to overdo it!

Jeff

Snoredog · Post by **Snoredog** » Sun Feb 11, 2007 10:44 pm

It has nothing to do with your pressure range. I would also expect to see snores along with that increasing AHI data, snores cause the machine to drive up the pressure, and can increase the frequency of events seen when not eliminated, meaning you missed your pressure sweet spot. It will probably drop back down again once you get around 16cm pressure, but you would be foolish to leave it there. Get James Skinner's Pro Analyzer and run it against your data, it will show you your sweet spot much faster than doing it manually.

It can be compared to telling your doctor it hurts when I do this...

he obvious answer then is not to do that.

Linda3032 · Post by **Linda3032** » Sun Feb 11, 2007 11:16 pm

So Jeff, did you look to see what kind of apneas you were having at what pressures? That info should lead you in the right direction.

jrfoster · Post by **jrfoster** » Mon Feb 12, 2007 8:45 am

Snoredog wrote:It has nothing to do with your pressure range. I would also expect to see snores along with that increasing AHI data, snores cause the machine to drive up the pressure, and can increase the frequency of events seen when not eliminated, meaning you missed your pressure sweet spot. It will probably drop back down again once you get around 16cm pressure, but you would be foolish to leave it there. Get James Skinner's Pro Analyzer and run it against your data, it will show you your sweet spot much faster than doing it manually.

It can be compared to telling your doctor it hurts when I do this...

he obvious answer then is not to do that.

I do have the Pro Analyzer. The snore index varies widely. The last 3 nights the index went from 16.5 up to last nights 143.2. Someone has said the system reads when I clear my throat or sneeze as snores, so that would not mean actual snoring. Also I was told that since I am always repositioning my hose, I hear it rubbing along the head board, etc, that it reads that movement as snores? Is that true?

Last night was wierd! According to the Pro Analyzer I spent 90% of the time at 2cm! I was set in APAP from 9-12. It said my average APAP was 1cm.
Something went screwy during the night. AHI was 7.7.
Total snores 1247, time in apnea 17.9 minutes with average apnea duration of 22.4 seconds! No wonder I am not my best this morning.

And so it goes!

Jeff

neversleeps · Post by **neversleeps** » Mon Feb 12, 2007 9:01 am

jrfoster wrote:Someone has said the system reads when I clear my throat or sneeze as snores, so that would not mean actual snoring. Also I was told that since I am always repositioning my hose, I hear it rubbing along the head board, etc, that it reads that movement as snores? Is that true?

Yes, that is true. Here is an interesting post by Derek (the author of MyEncore) where he discusses his experiments on RemStar snore detection:

derek wrote:I have been puzzled by what Respironics defined as a "snore" when reporting the Snore Index (SI) in Encore Pro. So between chores today I did a set of simple experiments to find out what was going on. For each experiment I defined a new patient in Encore Pro, put on the mask made a bunch of "snores" or pseudo-snores, then downloaded the data and used the indicated SI and session duration to find the total number of snores that Encore Pro thought it had detected.

In each experiment the APAP pressure started at 5.5 cm H2O. I also recorded the pressure at the end of the experiment to determine the effect of the "snores" on the therapy.

Here are some results:
Experiment 1: Regular snores (one per inhalation): I snored once per breath, for five breaths each minute, for six minutes - giving a total of 30 snores. Encore Pro reported:
Snore Index: 282.9
Duration: 7 mins
APAP pressure at end of experiment: 10.5 cm H2O
Total recorded snores = 282.9x7/60 = 33 snores
Conclusion: Encore Pro slightly over-counted the snores. This activity had a strong effect on the APAP pressure, raising it from 5.5 cm to 10.5 cm

Experiment 2: Short snores (within a single breath). This time I made 5 short snores (snorts) within a single breath, once per minute for six minutes. Total of 30 snorts. I was attempting to determine if the overcounting above may have been caused by interupted snores. Encore Pro detected:
Snore Index: 85.7
Duration: 7 mins
APAP pressure at end of experiment: 7.0 cm H2O
Total recorded snores = 85.7x7/60 = 10 snores
Conclusion: There were 6 groups of 5 snores. Encore Pro overestimated the groups, but did not count all of the short snores. A few times it counted more than a single snore within the breath. This experiment had a slight effect on the APAP pressure.

Experiment 3: Coughing. I wanted to see if a cough might be interpreted as a snore. I coughed once every ten breaths for a total of 20 coughs. Encore Pro reported:
Snore Index: 20
Duration: 9 mins
APAP pressure at end of experiment: 6.5 cm H2O
Total recorded snores: 20x9/60= 3 snores
Conclusion: Coughs are generally not interpreted as snores, and coughing does not significantly affect APAP pressure.

Experiment 4: Talking with the mask on. I wondered if the acoustic energy from the vocal chords would propagate down the hose and trigger the snore detection. Every ten breaths I said very loudly "I love APAP" (now you know how crazy I am ), for a total of 20 times. Encore Pro reported:
Snore Index: 5.2
Duration: 12 mins
APAP pressure at end of experiment: 5.5 cm H2O
Total recorded snores: 5.2x12/60 = 1 snore
Conclusion: Talking does not significantly affect the snore index, and does not affect the APAP pressure.

Experiment 5: Rubbing the hose on a sharp hard surface. I wanted to see if dragging the hose across an edge on furniture might generate sounds that would be interpreted as a snore. Every ten breaths, on inhalation, I took a wooden ruler and dragged it across the corrugations of the hose for a distance of about 9 inches, causing a sound that was somewhat snore like. I did this a total of 20 times. Encore Pro reported:
Snore index: 120
Duration: 11 mins
APAP pressure at the end of experiment: 10.5 cm H20
Total recorded snores: 120x11/60=30
Conclusion: Each stroke of the ruler generated a sound that propagated into the machine and was interpreted as a snore. This then had the same effect on the APAP pressure as true snores, raising it significantly.

Overall conclusions:
The snores reported by Encore Pro are individual snores. If a snore is broken into two during a breath it may or may not count as two. Coughing and talking ("tawgig" in CPAP parlance) do not affect the Snore Index, but the machine is sensitive to sounds caused by a sharp object dragging over the corrugations of the hose.

Now I've bored everybody to sleep... ZZZzzzzzz......
derek

jrfoster · Post by **jrfoster** » Mon Feb 12, 2007 10:09 am

Thanks for the reference to that post concerning snores. That stuff is very interesting!

Jeff