Which variables raise/lower the AHI ?

[Physician]

mind stages.
tiredness.
eat too late.
no exercise.
drinking.
humidity.
sleep position.
temperature of the room.
position of your mask.

Good list. Thanks.

[jlk]

Very good thought DoriC. You seem very pro-active with hubby's therapy..he's very lucky there. There is so much to learn and what works for some don't work for all. I was at 7.2 on cpap until recently getting apap. I set minimum at 6 and maximum at 12. I have never hit bottom or top limit, but have been close. I will raise my minimum closer to my 95% and see if my osa times are shorter. I only have 0 to 12 per night now, but the nice thing about having the software and a data capable unit is tweaking settings for optimal sleep quality. Thanks, jlk

[Wulfman]

• Autoset range 8-16, pressure titrates at 12-13 consistently.

• No humidifier


That right there explains to me why you have such a variance in your AHI.

Huh ? Why would the humidifier play a role here ?

And as for the range, it's the same range which gave me zero leak and zero AHI with the Activa, and the same settings since 7/1/2010. The Autoset gets to the titrated pressure within 30 minutes so it's similar to RAMPing.

Last night I changed from the very comfortable Comfort Classic back my usual Activa, and AHI was 0.1, again keeping the Auto set range 8-16, and as always, no humidifier.

I didn't highlight the humidifier part in my original post.......just the wide range setting.

The longer you're BELOW the optimum pressure (whether it's Ramp or lower pressure range), the more chance there is for events to occur. Some nights you have them and some nights you don't......and it could be due to a MULTITUDE of reasons. What doesn't make sense is why a person would use a much lower pressure setting than they "need".


Den

[torontoCPAPguy]

• Autoset range 8-16, pressure titrates at 12-13 consistently.

• No humidifier


That right there explains to me why you have such a variance in your AHI.

Huh ? Why would the humidifier play a role here ?

And as for the range, it's the same range which gave me zero leak and zero AHI with the Activa, and the same settings since 7/1/2010. The Autoset gets to the titrated pressure within 30 minutes so it's similar to RAMPing.

Last night I changed from the very comfortable Comfort Classic back my usual Activa, and AHI was 0.1, again keeping the Auto set range 8-16, and as always, no humidifier.

More clues.... it appears to me that your Comfort Classic is more "leaky" by design or otherwise, that your Activa, thus the higher pressures trying to compensate perhaps. OTOH, with the Activa your AHI was 0.1 which is about as good as it gets and I would suggest that you take a look at the pressures with the Activa... inquiring minds want to know!

[jdm2857]

The Autoset gets to the titrated pressure within 30 minutes so it's similar to RAMPing.

It's my understanding that APAP do not just determine an effective pressure and stay there. Instead, after increasing pressure to eliminate events (and/or precursors like flow limitations or snores), they slowly back off on the pressure, as it may no longer be necessary. The pressure falls (usually by exponential decay) until either the minimum pressure is reached or the machine detects an an event or precursor which causes the machine to start raising it again. Since your numbers are so good, you pressure is probably oscillating -- dropping until the machine detects precursors (which are not scored into your AHI) and not actual events, then increasing until the snores or flow limitations cease, and then dropping again.

Thus, you would be better off setting your minimum pressure at or just below the pressure that eliminates the vast majority of your events. This will prevent the pressure oscillation game while still allowing the algorithm to respond to occasional events that require more pressure, like those caused by moving to the supine position or REM sleep.

[williamco]

Last night I changed from the very comfortable Comfort Classic back my usual Activa, and AHI was 0.1, again keeping the Auto set range 8-16, and as always, no humidifier.

First. Thanks for starting this topic, it is very interesting.
but as long as the only variable in your case is the mask itself then why we go far and widen the search about pressure range, humidifier, Auto versus CPAP,..etc lets just decifer the mask issue:
1- It is interesting to know the AHI average of each mask in your case (you said it different but I don't remember seeing the numbers, how much different? )

2- Also, what is the leak rate of each mask?

I am sure others see different factors that affect their own AHI that are still interesting to know everyone's experience about these variables

[torontoCPAPguy]

Yes, worthy of note. Zeroing in on your ideal range is important as it does minimize the time it is going to take for the machine to reach the pressure being sought to alleviate the 'event'. Also worthy of note is that the 'ideal range' is not static but rather I believe it is a moving target and this is where APAP beats CPAP IMHO. On a night where I have not eaten heavily before bed, am dead tired after working a 24 hour shift, have had 6 drinks on getting home and then took a sleeping pill to ensure a good night of sleep..... you can bet your bippy that my 'ideal pressure range' is going to be different that it normally is. I am set for 12 - 16 cm H2O and have begun infusing about 3L/M O2 into the air line. I note that for whatever reason, my pressure seems to sit mostly at 12 and only rises occasionally to 13 or 14 and then return to 12 again. Soooooo. My next project is to reduce the pressure range down a tad. I am finding that the S9 Auto does not respond as quickly to events or pending events as my S8 Auto II did (I think.... hard to tell). The S9 Auto just 'FEELS DIFFERENT'. Even the EPR seems different on it.

So, there are many physical and environmental issues that will affect AHI, but we need to keep in mind that the pressure or pressure range on an APAP machine also comes into play; and that said pressure range is a moving target depending on the physical and environmental issues. Sorta like a dog chasing its tail it seems to me.

Even your mask is going to affect AHI and ideal pressures... and it can change from night to night as well. Some nights my Quattro FFM is sealed like an airlock all night. Other nights I haven't taken the full time necessary for precise fit and adjustment or have forgotten to give the mask a 'pluck' to make sure it is sitting as best it can on my face and PRESTO... my leak rate varies during the night. With the data coming out of your machine (assuming you have a data capable machine) you can follow some of these things and make allowances and educated decisions. Sometimes you just have to 'guess'. And I really don't think the MD's have it much better... mine applaud my efforts to pursue this affliction with dilligence. Some shrug.

[Physician]

The Autoset gets to the titrated pressure within 30 minutes so it's similar to RAMPing.

It's my understanding that APAP do not just determine an effective pressure and stay there. Instead, after increasing pressure to eliminate events (and/or precursors like flow limitations or snores), they slowly back off on the pressure, as it may no longer be necessary. The pressure falls (usually by exponential decay) until either the minimum pressure is reached or the machine detects an an event or precursor which causes the machine to start raising it again. Since your numbers are so good, you pressure is probably oscillating -- dropping until the machine detects precursors (which are not scored into your AHI) and not actual events, then increasing until the snores or flow limitations cease, and then dropping again.

Thus, you would be better off setting your minimum pressure at or just below the pressure that eliminates the vast majority of your events. This will prevent the pressure oscillation game while still allowing the algorithm to respond to occasional events that require more pressure, like those caused by moving to the supine position or REM sleep.

JDM, as always, you are of great help. How about trying the following:

1. Change the range to 11-16 and leave on AUTO

OR

2. See if a straight 15 fixed is tolerable

OR

3. Set the range to 11-16 with a 15-30 minute RAMP

[DoriC]

Very good thought DoriC. You seem very pro-active with hubby's therapy..he's very lucky there. There is so much to learn and what works for some don't work for all. I was at 7.2 on cpap until recently getting apap. I set minimum at 6 and maximum at 12. I have never hit bottom or top limit, but have been close. I will raise my minimum closer to my 95% and see if my osa times are shorter. I only have 0 to 12 per night now, but the nice thing about having the software and a data capable unit is tweaking settings for optimal sleep quality. Thanks, jlk

By Jove, I think you've got it!! Keep us updated.

[jdm2857]

All three plans sound reasonable to me.

With 1 and 3, you might find that you want to raise the minimum a bit after watching your data.

With 2, 15 sounds a bit high to start. Why not start at 13 and work up from there if you need to? As you know, the goal it to minimize the therapy pressure and your AHI. With a bit of trial and error (and patience) you can get close to that goal.

[jdm2857]

JDM, as always, you are of great help. How about trying the following:

You're giving me the credit? I just said what Dori said first, just less succinctly:

I'm not a physician but I wonder why you've got your minimum set so low when your avg pressure is 12-13? Your machine sure has a long way to go to prevent or eliminate your apneas. Have you tried raising your minimum? JMHO.

[Physician]

All three plans sound reasonable to me.

With 1 and 3, you might find that you want to raise the minimum a bit after watching your data.

With 2, 15 sounds a bit high to start. Why not start at 13 and work up from there if you need to? As you know, the goal it to minimize the therapy pressure and your AHI. With a bit of trial and error (and patience) you can get close to that goal.

My 30 day average pressure is 16.

[DoriC]

Correct Pressure settings are difficult to calculate if your mask is leaking so that's the #1 fix.

[Physician]

Correct Pressure settings are difficult to calculate if your mask is leaking so that's the #1 fix.

Set minimum to 13, max to 16, and this AM AHI = 0.5 and titrated pressure 14
Leak was 4.0 last night. Is that acceptable ? ResMed allows up to a whopping 24.0 !!!

[LinkC]

Thus, you would be better off setting your minimum pressure at or just below the pressure that eliminates the vast majority of your events. This will prevent the pressure oscillation game...

It will certainly LESSEN the oscillation game. To "prevent oscillation", why not set to CPAP at the 95% pressure. That's the logical conclusion to your strategy.