How Can A Sleep Study Produce Reliable Numbers?

RipVW · Post by **RipVW** » Sat Dec 01, 2007 8:50 pm

Okay, here's a question that's been on my mind—looking forward to benefiting from your collective wisdom here—

I've learned from this forum that we should never change settings on our xpap machines based on one or two nights' data. Instead, we need to review at least a week of data, since so many parameters change night to night. So, how can one-night sleep study data be at all reliable? How can that one unique night of numbers really provide a reliable baseline upon which to base one's therapy prescription? Wouldn't we be apt to produce different numbers on another night if we returned for a second, third . . . night?

Slinky · Post by **Slinky** » Sat Dec 01, 2007 8:59 pm

Its a matter of economics. One night's data can get you into the ball park whether by sleep lab titration or on autoPAP. BUT to get to the finer points of pressure needs multiple nights give better more concise information. Anyone want to do 5-7 nights in a sleep lab being titrated? And pay for those nights?

Yet once you have the ballpark (and it really is surprising how accurate to almost right on those sleep lab titrations can be) pressure if you want to start pinpointing more precisely that exact sweet spot of pressure the averages over 7 nights are going to find it quicker and more precisely.

RipVW · Post by **RipVW** » Sat Dec 01, 2007 9:11 pm

Thanks, Slinky!

Slinky · Post by **Slinky** » Sat Dec 01, 2007 9:15 pm

Yer welcome, Ted. Its just my take on it.

ozij · Post by **ozij** » Sat Dec 01, 2007 11:33 pm

It also a matter of history.

The first treatment for sleep apnea - before cpaps - was a tracheotomy.
You had a sleep study, they saw you choked, and the Rx was a hole in your throat. You plugged the hole during the day, and unplugged it for sleep.

Then they invented cpaps.

They're working on home diagnostic sets nowadays and they're making them better - I think that eventually, sets will be good enough to screen for garden variety OSA and those people will not have to go through a full PSG in a lab - since most of the PSG data will be recorded at home. A combined home screening and lab PSG will give much better data for the more complicated cases.

O.

RipVW · Post by **RipVW** » Sun Dec 02, 2007 7:36 am

Thanks, Ozij! That makes sense--I'll bet you're right that in the future there will be data collected from home that will enable a more precise diagnosis. Boy, sure glad Dr. Colin Sullivan invented the CPAP--we all need to send him a Christmas card! Trach--ouch!

ozij · Post by **ozij** » Sun Dec 02, 2007 7:46 am

Boy, sure glad Dr. Colin Sullivan invented the CPAP--we all need to send him a Christmas card! Trach--ouch!

Yeah....
You're welcome, Ted.

O.

Slinky · Post by **Slinky** » Sun Dec 02, 2007 7:53 am

After having to go thru two nights of titration because I didn't sleep long enough at either I've often thought that the PSG to evaluate for any and all possible sleep problems and THEN for those for whom OSA was THE problem a two week auto titration would be the most economical and sensible way to go.

HOWEVER, the problem I see w/that is the mask problem! I've tried masks that SEEMED to work for a night or two and then just could NOT be tolerated any longer. And then there is the humidifier issue. There are those who just do NOT tolerate humidification at all and those who absolutely need not just a humidifier but a HEATED humidifier.

No matter how you look at it the key seems to be patient education and that is problem thru out the medical sleep profession. It is erratic at best and too seldom adequately forthcoming

DreamStalker · Post by **DreamStalker** » Sun Dec 02, 2007 7:58 am

Well one way to get around the mask issue is to surgically install a hose adapter to your face for the two weeks of auto titration. Oh wait a minute, surgery is what we are trying to avoid here isn't it? ... never mind

Slinky · Post by **Slinky** » Sun Dec 02, 2007 8:04 am

There's always SuperGlue, DreamStalker!! What the heck skin is constantly replenishing itself. How long would it take for the SuperGlued skin to slough off?

Wulfman · Post by **Wulfman** » Sun Dec 02, 2007 12:23 pm

Ted,

I thought your question sounded familiar....

viewtopic.php?t=26172

Den

RipVW · Post by **RipVW** » Sun Dec 02, 2007 1:15 pm

Thanks, Den!

Ted

RipVW · Post by **RipVW** » Sun Dec 02, 2007 5:15 pm

Found this article. Apparently there is research indicating that sleep study results can indeed vary significantly from night to night--sometimes OSA is not even diagnosed (even though the patient does in fact suffer from OSA). "Night-to-night variability of apneas on overnight polymnography exists in patients with documented obstructive sleep apnea (OSA)."

http://www.chestjournal.org/cgi/content ... f_ipsecsha

Even a person with severe apnea might not be diagnosed, so those variations might be extreme. (as discussed here by one who experienced this: http://www.apneasupport.org/viewtopic.php?t=10818)

BTW, when I posted this topic, I used the word "reliable" as defined in research terms (i.e., degree to which results are replicable).

Country4ever · Post by **Country4ever** » Sun Dec 02, 2007 5:41 pm

I had my first sleep study about 10 years ago. It started at 11p.m. and I didn't get to sleep until 4:30a.m. They woke me up at 5:30. The doc (a neurologist who had studied sleep medicine at Johns-Hopkins), told me everything was fine and I didn't have any problems. I asked him how that could be, only sleeping so little, and he said "we saw everything we needed to see".
So then I spent about another 8 years so fatigued I could hardly function/migraines/waking up gasping at night, etc., etc.....before a different doc convinced me to have another one, which showed the OSA.
I realize that you can't get everything you need to see in one night of a sleep study, but how can a doc say you don't have a problem, when you only slept a little over an hour??

RipVW · Post by **RipVW** » Sun Dec 02, 2007 6:10 pm

I guess I'm really overly sensitive to this subject, since I, too, was a victim of what I believe was "bad data" from my first study. My OSA was diagnosed as "mild" and I was prescribed a simple CPAP machine with a constant pressure setting of 6. I knew no better. I did ask questions, wondered how reliable the data was, and if my pressures would ever change. I was assured that my therapy needs would remain fairly constant, and my doc never asked for data after the initial study, no mention of a follow-up appointment. Over a year later, still feeling pretty tired all the time, not really noticing any of the anticipated improvement in my energy level . . . I began to do my research, found this forum. I purchased an APAP data capable machine, and it shows that my average pressure is around 12! So, as with all aspects of our personal health, I learned again that we must take responsibility, must do our homework, seek second opinions, and read, read, read. Thank goodness for the internet--we can learn so easily!

So, from my limited personal experience with OSA, sleep tests, and CPAP therapy, I believe everyone should have an APAP, even if it is set to auto mode only occasionally to check the numbers. Those numbers do change, night to night, week to week, month to month, and year to year. Ted's prediction is that eventually the APAP will become the standard, that old CPAP, constant-pressure-only machines will be old technology, no longer manufactured. Had I had an APAP from the beginning, I wouldn't have suffered during that first year from lack of real therapy.

Well, that's my story, and I'm sticking to it :<)

Machine	Mask

Additional Comments: Resmed HumidAir 11 for humidifier