Question About HI Scoring

[Weezer]

Yikes! I'm still getting crazy high AHI numbers on my ResMed Autoset Vantage – higher than my original sleep study. This makes no sense to me.

I've tried setting it "wide open," limiting my range closer to my titrated pressure of 11, and running it on straight CPAP at 11. While my AI numbers look decent – last night: 1.0 on straight CPAP – those HI numbers are off the charts. What is going on here?

Is it that the Vantage is A.) hypersensitive to hypoapneas – more so than in my original split sleep study? B.) Scoring HIs while I'm still awake and breathing "normally"? (It sometimes takes me awhile to fal asleep). Or C.) god forbid, somehow causing these hypoapneas to occur?

I'd really like to get these numbers under control.

Is this something to worry about? What should I do???

[Bookbear]

First, yes, the Vantage IS more aggressive in scoring hypopneas. Apparently, all the ResMed machines are. What other machines might ignore, the ResMed's count. Another way of looking at this is that the threshold for what counts as a hypopnea is lower in the ResMed algorithm, i.e. a lesser flow limitation or a shorter time period.

Second, if you are using the Vantage in Auto mode, check to see what your 'Settling' setting is. It takes the place of the Cpap mode's ''Ramp' setting, and is the time (in 5 min. increments) that the machine gradually works up to your lower pressure, and ignores any apneas or hypopneas. So, if you have Settling enabled, and its time setting matches the time it takes for you to fall asleep, it is NOT scoring hypopneas while you are awake. But if you take a half an hour to fall asleep, and Settling is set at 10 minutes, the machine is scoring (and treating) for 20 of those thirty minutes.

Ideally, then, your Settling setting should be at or just slightly longer that the time it takes for you to get to sleep. Don't make it too much longer though... you aren't getting any therapy while Settling is active. I am lucky in that I fall asleep quickly. My Vantage is set for 5 min. of Settling time.

Sleeping position affects both apnea and hypopnea events. They are more common if you sleep on your back, and less when you sleep on your side. I notice a marked difference in my numbers when spend more time on my back; my AHI goes from low 2's to mid 3's, nearly all hypopneas.

Hope this helps!

[rested gal]

While my AI numbers look decent – last night: 1.0 on straight CPAP – those HI numbers are off the charts. What is going on here?

Weezer, when you say the HI numbers are off the chart, what are some of those HI numbers you've been seeing?

If you're talking about things like AI 1.0 and HI 6.0, that kind of difference (adding up to an AHI of 7.0) it might not be anything to worry about.

I've used autopaps, bi-levels, and cpap made by the the three major manufacturers. ResMed S8 machines are the only ones that always reported a much higher Hypopnea Index for me than any of the other manufacturers' machines. Double, triple, quadruple even, what the HI report was from other brands.

Since I felt just as rested the next morning no matter whether it was a Resmed S8 machine, or a Respironics, or a Puritan Bennett, I chalked up the higher HI reported by a ResMed S8 as simply the way that manufacturer chose to define "hypopnea." Calling something an hypopnea when Respironics and Puritan Bennett might call that same scenario "flow limitation."

That doesn't mean that one manufacturer is letting more "hypopneas" slip by than another. Nor does it mean that another manufacturer is missing seeing some "hypopneas" than another. It's simply a difference in the way each manufacturer designs their machines to interpret various degrees of limited air flow in a person's breathing.

As I understand it, each manufacturer has their own arbitrary definition of the degree of reduction of air flow and duration before they mark it as "hypopnea." Lacking pulse oximetry to see if there is a drop in SpO2, our machines can't look for "hypopneas" in the same way a PSG sleep study does.

In a sleep study, I believe there has to be a 4% drop in O2 before it's scored as an hypopnea -- if the study is being scored by Medicare requirements. If I'm not mistaken (and I sure could be!) I think many (most?) sleep labs report hypopneas both ways separately -- with, and without, that amount of desat. I don't believe there's much way to truly compare what kind of hypopnea index you see at home with what was reported for hypopneas in the sleep study titration.

Some brands of autopaps suit some people better than other brands do. To me, it's normal for Resmed S8 machines to report a higher HI than other brands, so if I felt good and rested after using that machine, I wouldn't worry about it. If the hypopneas are really "off the charts" consistently high, another brand of machine might suit you better. Dunno. If another brand showed similar unusually high hypopnea results, that could be your cue to check back with the sleep doctor to see what's going on.

My edit: Added "S8" to all my references to ResMed machines in this old post, since the definition of hypopnea was changed by ResMed in the later S9 series machines.

[Weezer]

Thanks for the advice, Rested Gal and Bookbear.

I will continue to use Settling – though it usually takes me a pretty long time to fall asleep and then the machine wakes me up after two or three hours, so it's scoring those hypos again.

Worse, I find I'm taking off the mask and sleeping the rest of the night without it, which could also skew my results. It's really hard for me to sleep the whole night on CPAP. How long did it take for you? Any tips for me?

I've been on CPAP for about three weeks – and the truth is, I don't feel better. Still exhausted during the day, plus the stress of falling asleep at night isn't helping. The Swift II is pretty comfortable, but the Vantage can be LOUD. I have to cover it with a towel to quiet the whistling/wheezing.

I've requested a copy of my original sleep study, so I can compare HIs. All I know so far is that my AHI is 10.2, 11.8 supine, but they haven't told me anymore than that.

What troubles me is that my AHI numbers on the Vantage are significantly higher than that – consistently over 15 and sometimes more than 20, though my highest AI has been 5.5. Would you consider those adequate results?

I've thought about trying another machine, but apparently the RemStar Auto (a favorite on this board, I've noticed) has been discontinued – and I've heard a lot of complaints about the M Series.

Sorry for the long post, but I am getting desperate here – and I'm tired of being tired!

[billbolton]

but the Vantage can be LOUD. I have to cover it with a towel to quiet the whistling/wheezing.

I suppose it depends on what you think is "LOUD", but in then normal course of events a S8 Vantage shouldn't be producing whistles and wheezes, so that suggests that something else may be wrong with your set up?!?

I've thought about trying another machine

You really need to understand what is happening (or not happening) with your whole set up before you go changing anything. Otherwise you will just be thrashing and not actually working to solve identifiable problems.

Without seeing specific chart information its hard to say what your issues might be, but the sprt of HI your are seeing would seem to indicate that you may be having leakage issues.

Cheers,

Bill

[track]

I have a resmed machine...S7 auto spirit. My HI typically run about 3- 4 times the AI. I don't pay any attention to the HI as it records them about the same, no matter what the pressure. It's the AI that I focus on. I strive to keep it under 1 and when I do that the AHI will be under 5.

[track]

I use the settling for 45 minutes to keep the pressure lower so as to have less air in the stomach. It doesn't seem to effect my numbers much as most of my events occur closer to early morning when I get in a deeper sleep. The first hour is not usually a deep sleep.

[Organplayer]

Thanks for these comments. Lately, I have had virtually no AI (.2 to .4) but 2-3 on the Hi scale. As I run an S8 Elite, it was bothering me to not be able to get the Hi down. I have very little leak (.12 last night) so I know Im getting there.
And yes, I feel REALLY good.

Too bad we do not have a uniform definition and algorithm for hyponeas.
On the other hand, Cpap is business.

Kevin