What Is the Difference Between Events/Hr, AHI and Total AI?

I am near the end of the at home titration. The Resmed AirSense 10 Autoset for Her has a report in the little window on the machine. It shows Events/Hr, AHI and Total AHI. What is the difference between them? Last night they read Events /Hr 2.5, AHI 9.1 and Total AI 8.7. These numbers have slowly been coming down during the titration. Even the pressure has come down from 15.0 to 12.6.

I know that I need software but am not a geek and will need help at home to install it. My helpers are reluctant to put personal medical charts on the Internet and can't begin to think about it until after the New Year. I am grateful for all the help here and tell everyone I know who's on CPAP about this site.

Usage hours Number of hours the device has been used during the last session.
Events (AHI) per hour Apneas and hypopneas measured per hour for one day. An apnea is when the
respiratory flow decreases by more than 75% for at least 10 sec. A hypopnea is when
the respiratory flow decreases to 50% for at least 10 sec. The Apnea Index (AI) and
Apnea-Hypopnea Index (AHI) are calculated by dividing the total number of events that
occurred by the total mask-on therapy period in hours.
Note: Under conditions of high leak with EPR enabled, AHI detection may not be
optimal.

More Info
Period Set the time interval covered by the Sleep Report.
The options are: 1 Day / 1 Week / 1 Month / 3 Months / 6 Months / 1 Year
Days Used Number of days the device has been used during the selected period or since the last
compliance data was reset.
Days 4hrs+ Number of days the device has been used for more than 4 hours during the selected
period or since the last compliance data was reset.
Avg. Usage Average number of hours per day the device has been used during the selected period.
Used Hrs Number of hours the device has been used during the selected period or since the last
compliance data reset.
Pressure Average pressure during the selected period (95 th percentile for each day; average of
the 95 th percentile values for periods >1 day).
Leak Average of the 95 th percentile values of leak during the selected period for days with
usage only.
AHI Apnea-Hypopnea Index—average AHI during the selected period. AHI and AI are
calculated for times of low leak only.
Total AI Apnea Index—average total AI during the selected period.
Central AI Central Apnea Index—average CAI of the Days Used in the selected period.

Hey PR, how come
this

Events /Hr 2.5

doesn't equal this

AHI 9.1

I am looking at the clinical manual and I see the same type of difference in the example they are showing..
page 18
Is it a 1 night vs overall average? That appears to be the only logical explanation and I was just wondering so I could better understand what is showing on the LCD screen.

Jaycee....do you have the clinical/provider manual for your machine? If not you might want to get it as it explains a lot of stuff. You can request it here.
http://www.apneaboard.com/adjust-cpap-p ... tup-manual

So with my machine and SleepyHead software if I turn on the machine but read for an hour before the mask goes on and then it comes off an hour before I turn off the machine and it was on 10 hours on but used only 8 really does the number of events get divided by 8 or 10.

Also, seems like a big difference if over an hour of real usage you get a large number of events vs the large number of events spread out through the entire night. How is that accounted for or does it not make a difference?

pgflrob wrote:So with my machine and SleepyHead software if I turn on the machine but read for an hour before the mask goes on and then it comes off an hour before I turn off the machine and it was on 10 hours on but used only 8 really does the number of events get divided by 8 or 10.

It gets divided by the number of hours you were actually attached to the machine and breathing into the mask.
If the machine is running at any time and you aren't attached to it then the machine in record hours used but will say something like "machine on but no breathing detected"...I forget the exact wording.

pgflrob wrote:Also, seems like a big difference if over an hour of real usage you get a large number of events vs the large number of events spread out through the entire night. How is that accounted for or does it not make a difference?

The machine reports the average and what you are describing is what I call "clustering"...where we have some periods of time with no events and then we have a period of time with a truck load of events and the overall average isn't that ugly but maybe that hour was real ugly...and that's why I prefer to look at the nightly detailed graphs to make sure no ugly clusters are showing up.
My OSA is much, much worse in REM stage sleep....so I would have periods of time with not much excitement going on in non REM sleep but a truck load of events in REM sleep...overall AHI was maybe 5 or 6 which isn't horribly horrible over 8 hours when maybe only 2 hours was in REM sleep but those 2 hours were ugly. For this reason I don't just go by AHI when I evaluate things...I look for clusters and if I see them I want to break them up so that I don't have so many events all bunched together. 15 events in 15 minutes is an ugly 15 minutes but 15 events over the 8 hours gives a nice low AHI. Sort of a false sense of security there when just going by AHI alone and not taking into account the ugly time.
The machine can't do this for you...you have to do this part yourself.

Pugsy wrote:Hey PR, how come
this

Events /Hr 2.5

doesn't equal this

AHI 9.1

I am looking at the clinical manual and I see the same type of difference in the example they are showing..
page 18
Is it a 1 night vs overall average? That appears to be the only logical explanation and I was just wondering so I could better understand what is showing on the LCD screen.

Jaycee....do you have the clinical/provider manual for your machine? If not you might want to get it as it explains a lot of stuff. You can request it here.
http://www.apneaboard.com/adjust-cpap-p ... tup-manual

Thank you Palerider.

Pugsy, I did print out the clinical manual but find it confusing. The Period is set for 1 month and I've used it for 29/29. The manual will be good when I start regulating treatment on my own but I don't see an explanation of the difference in the Events/Hr and the AHI. Are you saying that this must be a 1 month average or it's a 1 night?

The leaks have gone down to 36 L/min and it doesn't make any difference if I take the mask off and let the Smart Start turn off the machine or if I do it manually. I know that the leak rate is still too high and have purchased a Padacheek liner to use to see if that makes a difference.

I see the Sleep Medicine doctor next week and I don't expect him to know the ins and outs of the machine.

Pugsy wrote:Hey PR, how come
this

Events /Hr 2.5

doesn't equal this

AHI 9.1

I am looking at the clinical manual and I see the same type of difference in the example they are showing..
page 18
Is it a 1 night vs overall average? That appears to be the only logical explanation and I was just wondering so I could better understand what is showing on the LCD screen.

I believe that the events/hr is the last days AHI, while 'ahi' is for a longer period selected, so it could be an average of a day, week, month, 3 month, 6 month or year period.

jaycee2 wrote: Thank you Palerider.

Pugsy, I did print out the clinical manual but find it confusing. The Period is set for 1 month and I've used it for 29/29. The manual will be good when I start regulating treatment on my own but I don't see an explanation of the difference in the Events/Hr and the AHI. Are you saying that this must be a 1 month average or it's a 1 night?

everything above the 'more info' in the list above is for the most recent night.

everything below 'more info' is an average over the period selected.

jaycee2 wrote: Events/Hr and the AHI. Are you saying that this must be a 1 month average or it's a 1 night?

The Events per hour ...2.5 is the AHI for last night.
The other numbers are from the cumulative total screen and that means the 9.1 is the overall AHI over the period you have chosen to display the results.
Elevated AHI long term (that 9.1) is probably secondary to a lot of initial awake breathing stuff getting flagged by mistake.
What's important is what is going on now...so that 2.5 is good.

The leak number you are seeing...that's a 95 % number which means for 95% of the night you were at OR BELOW that leak number. People tend to forget the "or below" part of the definition and think this is where they at in terms of leak all night and that isn't the case.
What we can't see with the 95% number is how far below that number a person might have been and for how long at any number.
This is where the software leak graphs are critical for leak evaluation.
Obviously 36 L/min is bad but we don't know how much time you spent at that number...or how much time you spent at say 30 L/min or 24 or 10....
So we can't tell just how much time was spent in the really bad leak either. We know some time was spent there but we don't know for how long because we don't know about the other leak number times. Heck, you might have had 2 hours with no leaks at all for all we know.
It's possible that you were only actually in large leak territory half the night or 3/4 the night.
Yeah, 36 is bad but it might not have been bad for the entire night and that is why we really need to see the software leak graphs to know for sure if we can trust that AHI of 2.5 you just got. Over 30 L/min and the machine starts having trouble sensing events...doesn't know what to call them and over 35...it has trouble sensing that something even happened much less knowing what to call it.

Thank you Pugsy.

You nailed it and I will use your explanation to help sell the need for software, a wonderful treatment management tool.

jaycee,

if you roll the wheel knob to highlight period and push the center button and change the period to one day you will see the "Events per Hour" number up above repeated down bellow in the more information section - - they will be the same......ie, Events per hour will equal your AHI in the more info section for a one day period......might eliminate some confusion for you. As you can see the lower section labeled "More Information" you can get averages for different periods like week, month, etc........if you look at those average numbers for anything other than one day they won't match the top section which is just for the last night. If you have a difference in your AHI or Events Per Hour and your AI then that differences is Hypopneas.......for example my last night data showed Events per hour or AHI as 1.0, AI was just .2 so my Hypopneas were the difference between the two numbers so Hypopneas = .8 -- in this example my CA was the .2 so my Apneas were not obstructive, but Central.

I also discovered that in the Clinical Settings Menu you have to have the machine setting for "Essentials" set on "Plus" or you won't get the AHI and other information on the sleep report screen......if it's not set on "Plus" all you'll get is usage hour information and mask fit information. Sounds like your machine is set for the additional info with "Plus" already selected under "Essentials".

TangledHose wrote:jaycee,

if you roll the wheel knob to highlight period and push the center button and change the period to one day you will see the "Events per Hour" number up above repeated down bellow in the more information section - - they will be the same......ie, Events per hour will equal your AHI in the more info section for a one day period......might eliminate some confusion for you. As you can see the lower section labeled "More Information" you can get averages for different periods like week, month, etc........if you look at those average numbers for anything other than one day they won't match the top section which is just for the last night. If you have a difference in your AHI or Events Per Hour and your AI then that differences is Hypopneas.......for example my last night data showed Events per hour or AHI as 1.0, AI was just .2 so my Hypopneas were the difference between the two numbers so Hypopneas = .8 -- in this example my CA was the .2 so my Apneas were not obstructive, but Central.

I also discovered that in the Clinical Settings Menu you have to have the machine setting for "Essentials" set on "Plus" or you won't get the AHI and other information on the sleep report screen......if it's not set on "Plus" all you'll get is usage hour information and mask fit information. Sounds like your machine is set for the additional info with "Plus" already selected under "Essentials".

Wonderful! At the DME the RT I first had added that info because I asked her to. The LPN I subsequently saw said that most people don't want to see that and wasn't happy about it being there but I asked her to leave it and she reluctantly did.

Yeah, the default from the factory when the unit comes out of the box has "Esentials" "Plus" turned off.....I was coming to the AirSense from the S9 and was not familiar with the Essentials terminology until I read about it in the Clinician's Manual.....I am glad I found the setting because I was very disappointed when I couldn't see the AHI numbers and breakdown on the screen at first. Defiantly get either Sleepyhead or Rescan software so you can take further advantage of the data you can analyze with either software package....Sleepyhead is the preferred software.