The math of calculating AHI

[sptrout]

The one thing that throws a wrench into any AHI calculation is that the amount of "sleep" time used is never correct (the same can be said for the machine's recorded number of apnea hits which are known to be questionable). The machine's sleep time is just the number of hours/minutes that it was on, which is not the amount of actual sleep time. In my case, I know that my machine is on for at least 60 minutes more than my actual sleep time, which will provide an AHI calculation that is better than actual. IMO, caulated (or machine measured) AHI will always be better than actual even if by only a small amount (you fall asleep rapidly, and wake-up with an alarm clock). The best AHI will always be in bed, with the machine on, and never falling asleep at all; for real in my case sometimes. Not the best way to get a perfect "0" AHI, but it works every time. Only a sleep lab setup is able to correctly calculate AHI since they can measure brain waves to be able to know exactly when a person is asleep or not.

[jjtisch3]

Appreciate your consideration but this has nothing to do with the question I posted. I am really having problems with this site. I get emails that an answer to my post has been summitted. First I cannot find the answers, then what I do find is the answers are not related to my question. Sorry. Can someone help me navigate here.
Thank You  
John

[Gideon]

Show us the data you are using to calculate your AHI.
I suspect that it doesn't report hypopneas.

[OpalRose]

I can see total events, the time, oxygen levels and so forth on my wrist oximeter printout. I know the hypopnea events have to be added to the total events to get started to find my AHI. But, I cannot find anything that says hypopneas on my printout. 
Thank You
John

Hi and welcome back!  Just looking at this thread from 2018.  You are asking the same question as you did three years ago.
I assume you are trying to calculate your AHI from an overnight oximeter data.  As bonjour stated, showing us the data or printout you are using would be helpful. 

Prior thread from 2018:
http://www.apneaboard.com/forums/Thread-...#pid248321

Sorry, you are not getting the answer you want, but you need to give us a little more to go on.

[jjtisch3]

The current oximeter is different than the one I had three years ago. The current company told me they cannot give me the answers of what I want because they cannot interpret. I do not need an interpretation, just show me where are the number of hypopneas I need to add to the events. I know how to calculate it.  I have it set up as a Word document I hope is attached.. Thank you


This from a CMf50 wrist oximeter
Time length 04:37.49
Event Data                          Sp02
Total Events                        124
Time in Events (min)          83.9
Avg. Event Dur (secs)         40.6
Index 1 hr.                          26.8
Artifact (%)                            0.0
Adjusted index 1 hr.          26.8
Sp02 Data
Basil sp02                            92.6
Time min.<88%                    7.0
Events <88%                          25
Average low%                    89.4
Avg. low<88%                    85.1
PR Data
Avg. Pulse                          53.3
Low Pulse                            43

[Sleepster]

A hypopnea is an event, so hypopneas are included in the 124 events. Divide that by the 4.62 hours and you get a AHI of 26.8.

I'm not sure that an oximeter can accurately measure these things, though.

[SarcasticDave94]

I'm just seeing 124 events of some sort. It does not state what these events are. I am not certain an oximeter would be giving any hypopnea info as this is in reference to oxygen levels in the blood as opposed to apnea events.

[jjtisch3]

Thank you very much for your help. That's the way I have been doing it so I guess it is OK..
John

[Boroma]

Your Oximeter should give you Heartbeat rate, Perfusion index and SpO2 %.
None of those are used to calculate the Apnea/Hypoapnea index. Unless your SpO2 is well under 88% in which case your AHI would likely be 0.
Your machine should display the AHI and a couple of red or green icons when you turn it off.
The AHI is a fairly crude description of the quality of sleep. It lumps obstructive apneas (which are major events) together with hypoapneas (which could just be a hicup) and central apneas (breathing has stopped). It also does not take into consideration the duration of the apneas.
If you want to get a better picture of your sleep download Sleepyhead/OSCAR and transfer the data on the SD card in your machine to OSCAR. You will need a SD card reader of some kind. OSCAR will do most of the rest.
Then take a look at your daily reports by clicking on the displayed calendar.

[Crimson Nape]

None of the data you listed has anything to do with AHI or apnea. AHI is based solely on breathing and its cessation. The SpO2 software is listing an event as a SpO2 change of 4%, of its current value, for at least 10 seconds or a change in your pulse of 6 bpm, from it current rate, for at least 8 seconds. While both the CPAP and the oximeter use the term "Event" within their respective analysis, it is based on different data and parameters.