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Session Information AHI
#1
Question 
Hi, I am Curious re the Session Information, I do shift worker, sleep at various times and or may just turn off APAP for short period. On average may have say 3 sleep sessions register for each night. I see that although each individual sleep sessions AHI may be reasonable, my actual AHI for combined 3 sleep sessions will show quite high.

It appears both Sleepyhead & Encore do this and add the individual sleep session AHI together to give a Total AHI which I cant quite understanding how this would be correct, I would have thought that Total AHI for the night " 3 sleep sessions" wouldn't be any more than the highest individual session ?

Example say sleep 1300-1500hrs AHI 2.9, then 2200-300hrs AHI 2.4 then 0320-0630hrs AHI 4.3 if add session AHI's together will give AHI Total "9.6" Yet the e the highest individual session has AHI 4.3 which would be less than 1/2 the total session accumulative AHI ? and considered treated, If some could please explain what I am missing.
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#2
Hi ICEMAN,
WELCOME! to the forum.!
I don't use the data-management software but, hang in there, someone will be along to help you, soon.
Much success to you with your CPAP therapy.
trish6hundred
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#3
[quote='trish6hundred' pid='153507' dateline='1457668177']
Hi ICEMAN,
WELCOME! to the forum.!
I don't use the data-management software but, hang in there, someone will be along to help you, soon.
Much success to you with your CPAP therapy.


Yeah Thanks Trish
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#4
Hi Iceman

Welcome to the forum.

If you take the total hours that you slept (2 hrs +5 hrs+3 hrs 10 mins as per your post = 10 hrs 10 minutes 10.16667) and divide the total number of all reported apneas by this time should be your AHI for that sleep session. The AHI is an average of all reported apneas for one sleep session, even if it is broken into segments.

AHI = Total number of Apneas / Total Session Hours

An example; if you slept for a total of 8 hours in 3 segments being comprised of 4 hours, 3 hours, and 1 hour. If you had 8 apneas only in the first segment and no other apneas for the remainder of the night, your AHI would be 1.0.

I hope this may help.
______________________
Useful Links -or- When All Else Fails:
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#5
[quote='Crimson Nape' pid='153512' dateline='1457669525']
Hi Iceman

Welcome to the forum.

If you take the total hours that you slept (2 hrs +5 hrs+3 hrs 10 mins as per your post = 10 hrs 10 minutes 10.16667) and divide the total number of all reported apneas by this time should be your AHI for that sleep session. The AHI is an average of all reported apneas for one sleep session, even if it is broken into segments.

AHI = Total number of apneas / Total Session Hours

An example; if you slept for a total of 8 hours in 3 segments being comprised of 4 hours, 3 hours, and 1 hour. If you had 8 apneas only in the first segment and no other apneas for the remainder of the night, your AHI would be 1.0.

I hope this may help.

Thanks Crimson, think Ive go it now, each individual session AHI time is not the actual AHI for the individual session, apneas/Session hours, but the total night AHI averaged % split up over the individual sessions hours.

Cheers
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#6
I'll take a stab at it.
Sleep in 3 periods of duration T1, T2, and T3. You have an AHI number for each period AHI1, AHI2, AHI3.
The total AHI is not AHI1+AHI2+AHI3

It's ( (AHI1 x T1) + (AHI2 x T2) +(AHI3 x T3) ) / ( T1 + T2 + T3 )
[Image: 1F4m9Ift.jpg]
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#7
(03-11-2016, 12:44 AM)justMongo Wrote: I'll take a stab at it.
Sleep in 3 periods of duration T1, T2, and T3. You have an AHI number for each period AHI1, AHI2, AHI3.
The total AHI is not AHI1+AHI2+AHI3

It's ( (AHI1 x T1) + (AHI2 x T2) +(AHI3 x T3) ) / ( T1 + T2 + T3 )

Thanks Mongo I thought I had it worked for while but still confused. Example:Sleepyhead shows:
Single session (1) 3hrs 41min or 3.68hrs "AHI" 0.78 is 6 apnea events
Single session (2) 4hrs 01min or 4.02hrs " AHI" 1.94 is 15 apnea events

Total session shows AHI= 2.72 and total hrs as 7.70hrs if I calculate the 21 events / 7.70 hrs = 2.72 AHI same as Sleepy head.

But cant calculate the individual sessions to match? must be averaging it on the No Events per session can any one explain ?

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#8
(03-11-2016, 04:21 AM)ICEMAN Wrote: Thanks Mongo I thought I had it worked for while but still confused. Example:Sleepyhead shows:
Single session (1) 3hrs 41min or 3.68hrs "AHI" 0.78 is 6 apnea events
Single session (2) 4hrs 01min or 4.02hrs " AHI" 1.94 is 15 apnea events

Total session shows AHI= 2.72 and total hrs as 7.70hrs if I calculate the 21 events / 7.70 hrs = 2.72 AHI same as Sleepy head.

But cant calculate the individual sessions to match? must be averaging it on the No Events per session can any one explain ?

6 events/3.68 hours = 1.63 ahi
15 events/4.02 hours = 3.73 ahi
21 events / 7.7 hours= 2.72 ahi

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#9
(03-11-2016, 05:39 AM)palerider Wrote: [quote='ICEMAN' pid='153529' dateline='1457688097']Thanks Mongo I thought I had it worked for while but still confused. Example:Sleepyhead shows:
Single session (1) 3hrs 41min or 3.68hrs "AHI" 0.78 is 6 apnea events
Single session (2) 4hrs 01min or 4.02hrs " AHI" 1.94 is 15 apnea events

Total session shows AHI= 2.72 and total hrs as 7.70hrs if I calculate the 21 events / 7.70 hrs = 2.72 AHI same as Sleepy head.

But cant calculate the individual sessions to match? must be averaging it on the No Events per session can any one explain ?

6 events/3.68 hours = 1.63 ahi
15 events/4.02 hours = 3.73 ahi
21 events / 7.7 hours= 2.72 ahi

Yes Palerider that is what con fuses me if Sleep head shows Information session shows
Single session (1) 6 apnea events / 3hrs 41min or 3.68hrs as "AHI" 0.78 ?
Single session (2) 15 apnea events 4hrs 01min or 4.02hrs " AHI" 1.94 ?

But total of sessions 21 events / 7.70 hrs = 2.72 AHI
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#10
(03-11-2016, 06:48 AM)ICEMAN Wrote: 6 events/3.68 hours = 1.63 ahi
15 events/4.02 hours = 3.73 ahi
21 events / 7.7 hours= 2.72 ahi

Yes Palerider that is what con fuses me if Sleep head shows Information session shows
Single session (1) 6 apnea events / 3hrs 41min or 3.68hrs as "AHI" 0.78 ?
Single session (2) 15 apnea events 4hrs 01min or 4.02hrs " AHI" 1.94 ?

But total of sessions 21 events / 7.70 hrs = 2.72 AHI

you are leaving the middle session out of your calculation and it has a higher AHI and has skewed the average (which is for 3 sessions and not 2)
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Practising during the day can help you to keep it at night

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