AHI Calculation

WillSucceed · Post by **WillSucceed** » Mon Apr 25, 2005 3:14 pm

Anyone care to suggest how to calculate AHI from the data that one gets from the 420E - Silverlining?

For example, from Silverlining I get:

Events of complete sessions

session number / analysis period: 13
added util duration / analysis period: 95h 52min
Apneas: 49 number 0.5 index/h
Apneas with Cardiac oscill: 25 number 0.3 index/h
Hypopneas: 44 number / 0.5 index/h
FlowLimited Hypopnea: 9 number / 0.1 index/h
Acoustical Vibrations: 131 number / 1.4 index/h
Flow Limitations - Runs: 474 number / 4.9 index/h

Cycle states
Flow limited cycle: 5%
Invalid cycle: 0%
Normal cycle: 94%
Intermediate cycle: 1%
[/b]

-SWS · Post by **-SWS** » Mon Apr 25, 2005 3:41 pm

This is one of the questions I have for PB tech support. The answer might not be as straight forward as one might suspect. The off-the-shelf answer is "add up all the apneas and hypopneas then divide by hours slept". However, "hypopneas + FL" always gets scored in the ordinary "hypopnea" category as well. Then to complicate the scoring and tallying issue, there are some apnea tick marks that show up only under the "apnea/CA" category, some that show up only under the obstructive "apnea" category, and some that show up simultaneously under both apnea categories. I assume the simultaneous tic marks represent mixed apneas----part duration with cardiac oscillation and part duration without cardiac oscillation.

For sure the "hypopneas + FL" should be disregarded in the AHI tally since they are also represented in the ordinary hypopnea index. With some, but not all, apneas showing up in both apnea categories, there doesn't seem to be a precise way to calculate an exact AHI every time. That is unless Silver Lining happens to numerically incorporate mixed apneas in one "synthesized" index or the other (exclusively AI or exclusively CAI, or even equitably distrubuted between the two categories versus simple numerical duplication in both apnea indices).

Anyone know for sure? Any thoughts or SL3 data set interpretations regarding the "synthesized" apnea indices in particular?

gailzee · Post by **gailzee** » Mon Apr 25, 2005 6:15 pm

Hi WS:
I check my #'s daily, and add all the numbers, just in case. It's not clear in the guide (Franglish remember?) So I just add them and divide by my hours slept for a nightly total. I just mainly want to see how I'm doing, as opposed to how I'm feeling, because truthfully, I'm stil tired in the afternoon, my initial diabetes lower glucose numbers are up, and I'm having trouble staying asleep, so I shoot the all h--- the theory that after a few wks or mos. that'll I be ''refreshed, energized and alert". I am not, and the cynic in me is not expecting to feel better. I say this only because for a few short wks I felt much more energized, and now I'm back to my slothful craving a nap self, even after only an hr or two of waking up.

But I figure the damage to my system might be even worse, if I didn't use the darn beast every night.

For example, this morning's report for me went as follows:

ap's = 4
ap's w/cardiac 2
hypop's 4
pop's w/fllow==0 (what is this anyhow?)

So I calculate my grand total of events for the night as 10, divided by the 6 hours, I come up with
I just add the whole

WillSucceed wrote:Anyone care to suggest how to calculate AHI from the data that one gets from the 420E - Silverlining?

For example, from Silverlining I get: 1.67 I think I've done this correctly.
I am only assuming that my #'s are pretty good, as I've never really heard what is a good range, obviously the lesser the better.
My range is 6-14 on auto.

I hope I am doing this correctly, and maybe this info helps you? I hope so.
GZ

Events of complete sessions

session number / analysis period: 13
added util duration / analysis period: 95h 52min
Apneas: 49 number 0.5 index/h
Apneas with Cardiac oscill: 25 number 0.3 index/h
Hypopneas: 44 number / 0.5 index/h
FlowLimited Hypopnea: 9 number / 0.1 index/h
Acoustical Vibrations: 131 number / 1.4 index/h
Flow Limitations - Runs: 474 number / 4.9 index/h

Cycle states
Flow limited cycle: 5%
Invalid cycle: 0%
Normal cycle: 94%
Intermediate cycle: 1%
[/b]

TXKajun · Post by **TXKajun** » Tue Apr 26, 2005 7:53 am

I'm a big "KISS" fan.........Keep It Simple, Stupid.

I just add the index numbers from the right side of the listings, for instance (using the numbers from above):

Apneas: 49 number 0.5 index/h
Apneas with Cardiac oscill: 25 number 0.3 index/h
Hypopneas: 44 number / 0.5 index/h
FlowLimited Hypopnea: 9 number / 0.1 index/h

Gives an AHI of: 0.5 + 0.3 + 0.5 + 0.1 = 1.4 which is pretty darn good! It may be erring a bit on the high side by using the FlowLimited Hypopnea numbers, but this gives a conservative AHI result.

I agree, it sure would be nice if the Silverlining software had a single number that simply said "AHI: XXXX"

This therapy WORKS!! (But only if you USE it!)

-SWS · Post by **-SWS** » Tue Apr 26, 2005 8:11 am

FWIW I add 'em up too. Then I tell myself that although that simple total might not be accurate, at least it represents my "worst case" AHI as far as the 420e can synthesize a score.

Pickwickian · Post by **Pickwickian** » Fri Jun 29, 2007 5:18 pm

I am very interested in this stuff. I have been searching for definitions for the metrics that are used in the Silverlining software. Can someone point me to a link or two where I can learn all about this stuff? Much thanks in advance!

Compliance

Apneas:
Apneas with Cardiac oscill:
Hypopneas:
FlowLimited Hypopnea:
Acoustical Vibrations:
Flow Limitations - Runs:

Cycle states
Flow limited cycle:
Invalid cycle:
Normal cycle:
Intermediate cycle:

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): Hypopnea

rested gal · Post by **rested gal** » Fri Jun 29, 2007 10:43 pm

Hi Pickwickian,

I don't know where there would be explanations of those things all neatly together, but you can learn a lot about the 420E and many of those terms from the posts by -SWS and by ozij.

Here's a link to quite a few old topics -SWS participated in. Good sound info about the workings of the 420E from him in a lot of those discussions:

LINKS to message board discussions with "-SWS"

BrianRT · Post by **BrianRT** » Fri Jun 29, 2007 11:09 pm

Pickwickian.....that is the coolest name!!

For those of you who don't know, Charles Dickens accurately described a classic sleep apneic boy name Pickwick in Great Expectations......around a century before SA was introduced into the medical literature.

Anyway...just thought I'd acknowledge your reference.

ozij · Post by **ozij** » Fri Jun 29, 2007 11:31 pm

BrianRT wrote:Pickwickian.....that is the coolest name!!

For those of you who don't know, Charles Dickens accurately described a classic sleep apneic boy name Pickwick in Great Expectations......around a century before SA was introduced into the medical literature.

Anyway...just thought I'd acknowledge your reference.

Check your facts, Brian.

The book is "The Posthumous Papers Of The Pickwick Club", not "Great Expectations" and the boy is called Joe.

The object that presented itself to the eyes of the astonished clerk, was a boy--a wonderfully fat boy--habited as a serving lad, standing upright on the mat, with his eyes closed as if in sleep. He had never seen such a fat boy, in or out of a travelling caravan; and this, coupled with the calmness and repose of his appearance, so very different from what was reasonably to have been expected of the inflicter of such knocks, smote him with wonder.

'What's the matter?' inquired the clerk.

The extraordinary boy replied not a word; but he nodded once, and seemed, to the clerk's imagination, to snore feebly.

'Where do you come from?' inquired the clerk.

The boy made no sign. He breathed heavily, but in all other respects was motionless.

The clerk repeated the question thrice, and receiving no answer, prepared to shut the door, when the boy suddenly opened his eyes, winked several times, sneezed once, and raised his hand as if to repeat the knocking. Finding the door open, he stared about him with astonishment, and at length fixed his eyes on Mr. Lowten's face.

'What the devil do you knock in that way for?' inquired the clerk angrily.

'Which way?' said the boy, in a slow and sleepy voice.

'Why, like forty hackney-coachmen,' replied the clerk.

'Because master said, I wasn't to leave off knocking till they opened the door, for fear I should go to sleep,' said the boy.

http://dickens.thefreelibrary.com/The-P ... -Club/1-54

O.

BrianRT · Post by **BrianRT** » Sat Jun 30, 2007 10:27 am

LOL....what would I do without all of this help?

I REALLY need to quit posting at 1am

Only synapse connections I was making was....Pickwick=Dickens=Great Exp.

I knew it was the Posthumous Papers, just couldn't conciously recall that.

Just thought I'd bring Dickens' observations to the other forum members

ozij · Post by **ozij** » Sat Jun 30, 2007 10:53 am

Well, thanks to you I discovered the freelibrary, which has tons of classics just waiting to be read! Including Conan Doyle.

Yippee!

O.

BrianRT · Post by **BrianRT** » Sat Jun 30, 2007 7:38 pm

Well that's cool.

I just discovered myself that a good number of older books are now in the public domain, free for the public.

Just finished "Think and Grow Rich" by Napoleon Hill as a free online PDF. Beats going to the bookstore and shelling out the $$ for things that are already free!

AHI Calculation

AHI Calculation

Re: AHI Calculation