I Have Data - Am I Understanding the Numbers?

Hi, now that I have ResScan and a card reader, I can see that I'm having problems with leaks, not to mention too high an AHI. I'm posting the data from last night, which is in two segments. I've been having sinus/congestion problems lately, not to mention a sore nose, so I'd stopped wearing my Swift LT, in favor of my nasal mask. Last night I felt a bit better, so I started out the night with the Swift LT. I woke up a bit after 3:00am with a terrible coughing fit, and the mask leaking badly from my nose. Shortly before 4:00am, I switched to my F&P 406 nasal mask. You can see all the apneas occurred while I was wearing the Swift LT. Once I switched to the nasal mask, all I had were hyponpneas.

When I first got used to the Swift LT, leaks were almost nonexistent, and my AHI was between 3 and 5, but that was only a few nights before I started with the sinus/congestion and puffing air out my mouth. I'd really appreciate any comments and/or advice you have. (BTW, flow rate at 9cm for each mask is ~29.75l/min for the Swift and 32l/min for the F&P 406.)





TIA!

The leak rate doesn't look bad at all to me. Ideal with a ResMed machine is 0.0 leak rate, but anything that's not getting above .25 would seem very good to me, and yours are staying well below that for the most part. A leak rate of .40 and higher is what's considered unacceptable. Yes, keep working on controlling leaks, but yours really don't look like a problem. Unless the sound of leaks or the feel of leaks on your face are waking you up a lot.

The extremely jagged appearance of your leak line could very well be not only the mask leaks you noticed, but also a lot of mouth breathing or mouth air leaks due to your sinus-congestion issues. The report can't really tell us where leaks come from, so we have to be our own detectives to determine if it's mask leaks, mouth leaks (if not wearing a Full Face mask) or...both.

This next is just my opinion. Others may disagree. Or, it could be different for different people. My personal opinion is that the index to pay attention to with a ResMed machine is not the overall AHI (apnea/hypopnea index.) The index to pay attention to with a ResMed machine is the AI...the apnea index. Your AI is nice and low at only 0.7. That averages out to less than one "apnea" per hour.

Of course, when you see those apneas on your software printout, you may see them happening in a few clusters -- not scattered out uniformly as "one per hour." But even the clusters on your chart, twokatmew, are just a few, and of short durations. You can easily hold your breath for 10 or 20 seconds a few times without causing any harm.

The overall AHI you see of 7.7 is made up mostly of hypopneas, not apneas. My personal belief for a long time now has been (still is) that ResMed machines will mark more flow limitations as "hypopnea" than do other brands. That doesn't mean one brand is right and another brand is wrong about "hypopneas."

The difference in how many hypopneas one machine might "identify and record" for a person, compared to the number of hypopneas another machine might show can be simply a difference in the definitions each manufacturer has for "hypopnea."

Each manufacturer draws a different line in the sand, saying....

"On this side of the line are the restricted airflows that we are going to call 'flow limitations.' On the other side of the line are the restricted airflows that we are going to call 'hypopneas.' "

Chart posted by Velbor showing the differing definitions used by the different manufacturers:
April 2, 2009
viewtopic.php?p=356255#p356255

You'll read repeatedly on the message board about how it's best to get your AHI down to below 5.0. That's generally true, imho, EXCEPT when you are looking at results from ResMed machines. With a ResMed machine, I mentally cut the HI (hypopnea index) in half and then add that "half" hypopnea figure to the AI (apnea index.) I consider THAT total to be my "AHI" with a ResMed machine.

If you do that with your HI, twokatmew, you'll get an HI of 3.5 instead of 7.0.

Add that revised HI of 3.5 to your AI of 0.7, and your revised total AHI is now 4.2.
Nice.

I'd consider that to be my AHI ... " 4.2 "

More about the hypopnea stuff:

High HI affecting AHI rating. Should I be worried - topic started by ChrisC
Mar. 30, 2009
viewtopic.php?p=355205


Alternative ways to decrease the AHI - topic started by christo
Dec. 21, 2008
viewtopic.php?p=324087#p324087


I need to stop chasing 0 AHI. - topic started by fortomorrow
Dec. 4, 2008
viewtopic.php?p=319432#p319432


Hubby's AHI sucks... - topic started by Debjax
Feb. 15, 2009
viewtopic.php?p=339278#p339278

Yep! That's what I say too Rested Gal. I learned, from you, about Resmed machines and Hypopneas and it is continually proven by Resmed data posts here.

twokatmew- you're doing twice as well as you think!

Glad to see that you've obtained the software! Just a few additional comments:

I agree completely with RestedGal that your leak NUMBERS are NOT necessarily a problem. (Any leak MAY be a problem, if it annoys you, if it awakens you. Best to have zero. But that's not a requirement.) Note the red line on the leak graph at 24 L/m (=0.40 L/s). As long as you're below that line, you're well within the machine's ability to maintain pressure and sense what's going on (and, if you were using Auto, to act upon it). Note that the two "spikes" above the line appear coincident with the machine turning off. Those sorts of spurious entries are common (to all machines, especially if you're using the "auto-off" option to turn the machine off by simply removing your mask).

You may or may not have already discovered that you can "rescale" the time axis on your graphs; you can show, for example, a 12 hour period instead of the full 24. That would "spread out" some of the "densely packed" information being displayed.

Note also that all of your apneas occured during your first sleep period, with none during other three sleep periods. Your position, or who knows what else, may have been different. You had NO apneas for MOST of the night. (If you had not stayed in bed so long, your index numbers would have been higher, demonstrating that the numbers ALWAYS have to be taken in context.)

You have already run into the ResMed "10-hour limit". For reasons beyond mortal understanding (though there may indeed be good reasons), the machine stops outputing pressure and leak data after about ten hours. Note that the graphs for apneas and hypopneas continue even after that time; the machine is still working and tracking efficacy, even after the 10-hour cut-off.

Regards, Velbor

Thanks for the comments and reassurance, everyone! Rested Gal, thanks for the links. I'll have to check them out thoroughly.

Last night I slept with the Quattro FFM (got it off cpapauction for $25 + shipping!), and leaks were a bit better, with an ~1.0 improvement in
AHI. Apneas were spread out through the night, which is more typical than them being clustered. But, I had to strap the mask down pretty tight to avoid leaks into my eyes and at each side of the mask's bottom edge. I also don't particularly like the "sticky" silicone -- I prefer the smoother silicone on the F&P 406 nasal. Still, the Quattro will be good for those nights I have bad sinus issues. I picked up some 3M gentle paper tape at the store today, so if I can bring myself to tape my mouth shut, I'll compare last night's data with tonight's. I plan to use the F&P 406.

Had I realized that Resmed machines lump flow limitations and hypops together, I might have gotten a different machine: My initial sleep study showed 1 central apnea, while everything else was hypopneas. I'll have to get the results of my titration study to compare.

Stay tuned.

And thanks again!