Understanding AHI value on ResMed S9

I currently have a head cold and am quite congested. This morning when I woke up, I clicked the info button on my S9 and it said my AHI was 4.5. A good night sleep for me is usually around 0.8 to 1.2. A bad night is >1.5. 4.5 is unheard of. Although I'm tired today, I woke up several times throughout the night and am feeling rundown from having a cold.
I don't have the typical headache that comes with a leaking mask/bad night sleep.

My questions are, how is the AHI number calculated and could being congested (can't breath well through nose, although I'm typically a mouth breather anyway) throw the machine off? Is there any other explanation for such a high AHI value?

Thanks!

Mike,

Do you have the ability to download your data and look at the graphs? It would be interesting to see the graph that shows your events. If you normally breathe through your nose, but had issues due to congestion, you could have had many more events than normal. This could have happened for several reasons. One is that if you normally breathe through your nose, and it was somewhat obstructed, your breathing could have been interrupted. Similarly, if you normally breathe through your nose, but had to mouth breathe last night, the air takes a different path that could be more difficult for you to breathe through. You might have also tossed and turned more, and some people record events when they turn over. I know I do because I hold my breath when I turn over.

-john-

AHI of 4.5 isn't high. It's still still as "nil sleep apnea"
i'd say you're more likely to feel crappy since you're already sick

mike45 wrote: My questions are, how is the AHI number calculated..?

That's an easy one, I can answer it.

AHI = (total number of apnea events)/(total hours on CPAP) for the last 24 hours. No differentiation between OA, CA, HA, no difference between awake and asleep, if the machine was running the timer counts.

So IMHO it's an interesting number but not one to rule you life by. To me a small number means things are good, a larger number means look at the details and see what is going on. Small and large are relative to your norms.

When we have a crappy night's sleep for any reason it is common for the AHI to be elevated. I had one last week where my AHI was 6.07 and I knew it was going to be ugly the moment I turned off the machine. There's a lot involved like awake time and the machine maybe scoring some awake breathing irregularities which inflate the AHI or sometimes the general congestion issues will inflate the AHI.
I wouldn't worry about it...you know you weren't feeling well and the numbers reflect it. It's common. When this happens to me I just shrug my shoulders and move on because there really isn't anything to worry about and we can't do much about it anyway because it is just poor sleep in general to not feeling well. It will pass and soon you will be back to your normal self and the AHI will go back to what you normally see.

Mike, I have a horrendous cold too and my AHI was tenfold what it typically runs, but last night, down to normal. When I press on the S9 to flicker, I can see my pressure and leaks were unchanged on this bad night, so this means to me, that is the machine did not increase pressure, I just had lots of clear airways with wake-ups, cough and congestion. The main point is that we are using the machine despite the cold, and our numbers are much better than if we just slept in a recliner. CPAP cold recommendations in previous posts include turning up the humidity a bit and using more Lansinoh around nares, both helped me.

When I am congested, I have two problems that would elevate my ahi.

One, I already have a narrow throat, and congestion just makes it even smaller. So, it doesn't take as much to close off my airway.

Two, I don't feel good, can't breathe as well, so I toss and turn. And that will cause more centrals as we tend to hold our breath when we roll over and readjust.