Length of AHIs

[iSnooze]

I've been on CPAP therapy for a year now and have been happy to see that my AHI has been below 1 every night except once. The therapy is definitely working.

Just today I started looking at more than just the number of AHIs. I looked at the length as reported in SleepyHead. Can someone tell me why according to the graph below it appears that I had an AHI for almost 2 hours, and then 2 more for about 45 minutes each?
   

Edit: Dang, that attachment is tiny. Click on it and it should open another window and with a size that you can read the details.

[TheWerkz]

Can someone tell me why according to the graph below it appears that I had an AHI for almost 2 hours, and then 2 more for about 45 minutes each?

Hi iSnooze,

The duration on the AHI graph is actually how many apnea's you had per hour, in this case it's 3 apnea's over about a 6 hour timeframe, that gives you an AHI of about 0.5, or one apnea every two hours approximately, but AHI is the average number apnea events per hour for how ever long your sleep session lasted, in this case close to 6 hours.

On the log graph, after an apnea occurrs, it waits for somewhere close to an hour before it falls back down to 0, if you had another event within the same one hour timeframe the line jumps up to 2 or 3 etc., indicating how many apnea's you had during the same one hour timeframe since the first apnea occurred, since none of your events happened within the approximately one hour timeframe of each other, the green line drops back down to 0 until the next apnea event occurs.

The actual time duration of each apnea type is listed in SleepyHead in the "Events" tab, just expand the type of event and in the expanded view it shows the timestamp where each event occurred and the duration of the apnea in parenthesis, if you click on one of the event times it will show the Flow Rate graph in a zoomed-in view so you can see what the event looked like to the machine as far as your breathing pattern was concerned.

Does that even make sense?

Ren

[iSnooze]

Thanks, Ren. I didn't look at the events tab. If I understand you correctly, the length of time on the AHI graph doesn't really matter. That does show me how many AHIs I've had in an hour. The info under the events tab will tell me how long the apnea actually is. The event from last night reads:
Hypopnea 1 event
#001: 00:32:16 (22)
Does this mean that I only had 1 even last night at 32 minutes after midnight and it lasted for 22 seconds. Is that what the (22) means?

iSnooze

[JudgeMental]

Not to answer for Ren.. He gave you a good reply but just in casse he misses your question.. Yes..the 22 is the duration in seconds. You appear to be getting very good CPAP therapy.. good luck.

[TheWerkz]

Thanks, Ren. I didn't look at the events tab. If I understand you correctly, the length of time on the AHI graph doesn't really matter. That does show me how many AHIs I've had in an hour.

Correct! If you were to have say 3 events in close proximity you'd see a stair-step in the graph indicating how many apnea event's occurred within an hour instead of a flat line like your graph showed.

This is a simplified explanation but, if you were to have multiple apnea events like 10 every hour, then the green line on the graph would look more like stair-steps going up and then going down and then back up and it could go on for hours without ever dropping back down to 0 on the scale since it's displaying the number of apnea's per hour approximately.

The info under the events tab will tell me how long the apnea actually is. The event from last night reads:
Hypopnea 1 event
#001: 00:32:16 (22)
Does this mean that I only had 1 even last night at 32 minutes after midnight and it lasted for 22 seconds. Is that what the (22) means?

Yes! That's exactly what I meant when I said "the duration of the apnea in parenthesis".

Now, if you click on that timestamp it will show the zoomed-in view of that event on the Flow Rate graph so you can view your breathing pattern when it happened.

JudgeMental is absolutely correct, you really are getting good therapy if your AHI is consistently this low.

Ren

[PaulaO2]

At the bottom of the events tab is a slider with a number at the right. When you click the event, that number is the number of minutes the graph narrows down to. I think the default is the highest, 30 minutes. You can slide the slider to make the graph cover less time which shows more detail. Whatever you set it to is the new default for each dataset.

[iSnooze]

Thanks JudgeMental, Ren, and Paula. I've learned new things about how to look at the data. Knowledge is power. All 3 of you gave clear explanations.

I know that I am fortunate to have consistently low daily AHIs. I'll gladly take the F16 fighter pilot look over how I felt a year ago before CPAP therapy.

[TheWerkz]

At the bottom of the events tab is a slider with a number at the right. When you click the event, that number is the number of minutes the graph narrows down to. I think the default is the highest, 30 minutes.

Good catch Paula!

I've had mine set to 1 since I first started using SleepyHead and I had totally forgotten what the default setting was.

[PaulaO2]

I think mine is 10 or 15. Mine tend to be clustered together so a wider zoom means I can see them together.