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AHI Data question
#1
So the other night I woke up after 3 hours and saw my machine was indicating an ahi of 6.5, which was very high for me;

I went back to sleep and after another 3 hours, the total nights AHI reading was 2.4

So help me understand the math......

AHI is events per hour..........

so after 3 hours, my ahi was 6.5 .................. and if I had no additional events...... in the forthcoming 3 hours ........ I should think that my ahi would be 6.5 divided by 2 or 3.2 ....... but it was not............... how did I get to a toal ahi of 2.4 for the night?

thanks
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#2
From my very limited experience, are these numbers from ResMed or SleepyHead data? Due to their different algorithms employed, they can and will report differently. I believe it's calculated by length of events/usage time. That way an apnea of 30 seconds carries a higher weighted average than one that lasted 10 seconds.
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#3
I'm not sure exactly what the screen reports. I looked through the manual and couldn't find it. Since it is reporting it "live", it could be reporting the peak AHI vs the actual.

PaulaO2
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.




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#4
From http://www.resmed.com/content/dam/resmed...er_eng.pdf

Apnea Indices
For all indices, the value shown for Statistics is the total number of events divided by Daily Usage.

AHI — Apnea–Hypopnea Index
The total number of events is calculated by adding the number of apnea and hypopnea events.
For graphs, the AHI count is incremented at the occurrence of every event and reset every hour
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#5
Zonk,

Do you have the Resmed web site memorized?? Smile

Best Regards,

PaytonA

Admin Note:
PaytonA passed away in September 2017
Click HERE to read his Memorial Thread

~ Rest in Peace ~
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#6
I have seen the exact same thing in SH when you have more than 1 sleep session in the night. Sometimes, the AHI is lower for each individual session and higher for combined session.

Maybe its a bug in SH.
PRS1 Auto & Dreamstation Auto w/ P10 and straight pressure of 7cm. 
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#7
(11-19-2014, 03:26 PM)PaytonA Wrote: Zonk,

Do you have the Resmed web site memorized?? Smile

Best Regards,

PaytonA
Habit is second nature

[Image: Tea-Pot.jpg]
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#8
(11-19-2014, 02:47 PM)zonk Wrote: From http://www.resmed.com/content/dam/resmed...er_eng.pdf

Apnea Indices
For all indices, the value shown for Statistics is the total number of events divided by Daily Usage.

AHI — Apnea–Hypopnea Index
The total number of events is calculated by adding the number of apnea and hypopnea events.
For graphs, the AHI count is incremented at the occurrence of every event and reset every hour

So that's why it tracks the "peak" AHI. And looking at the screen while the machine is in use is kinda useless.

You're such a good alien, zonk. I like you.
PaulaO2
Apnea Board Moderator
www.ApneaBoard.com


Breathe deeply and count to zen.

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.




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#9
(11-19-2014, 05:28 PM)AshSF Wrote: I have seen the exact same thing in SH when you have more than 1 sleep session in the night. Sometimes, the AHI is lower for each individual session and higher for combined session.

Maybe its a bug in SH.

The OP was seeing this data on the screen of his machine, not within SH.

The problem with combining sessions is the math. The machines (and SH) don't use 60 minutes, they use 3600 seconds, calculate the events, then round it up. Quite often the two sessions AHI added together don't equal the total SH comes up with.

Then there's the way the machine itself comes up the the total vs the way SH comes up with the total. And it can be a mess. But really, unless the two is off by more than 1.0, I'm not gonna be upset.
PaulaO2
Apnea Board Moderator
www.ApneaBoard.com


Breathe deeply and count to zen.

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.




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