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Comparing AHI Severity with Lowest o2 Sat Severity - GoliGoli - 08-01-2022
On my sleep study I had a AHI of 11.6 which is supposedly mild. But I also had a lowest o2 saturation of 75% with an average of 94%. I believe this lowest of 75% puts me in the "Severe" category? Time spent below 85% was 11.7 minutes or 2.5% of sleep time recorded.
Two questions:
1. At first I was glad to hear I only had "mild" apnea due to the AHI. Is this low of a o2 sat something I need to be quite worried about?
2. I see AHI used as a metric a lot here, but not as much mention of o2 saturation levels. Which is the more important metric both for health terms and for tracking results?
RE: Comparing AHI Severity with Lowest o2 Sat Severity - cathyf - 08-01-2022
This is a fundamental weakness of first defining apnea by "events" and then averaging everything together into garbage statistics.
The main problem with trying to use SpO2 is that most people don't have a pulse oximeter and so have no idea what their O2 is doing. We all have cpap machines, so we have the data that the cpap collects.
What you are also touching on is another fundamental problem with our disease: not breathing -- apnea -- is something that everyone sees as a crashing medical emergency, while not sleeping is something that people brag about.
You would have a rare exotic disease if you were in actual danger of dying directly from the lack of oxygen directly caused by your apnea. The way this disease works is that what kills you (slowly, over time) is the sleep disruption and sleep deprivation. What kills you is your body's reaction to the breathing stops.
So, yeah, the answer is that it's complicated and not easy to parametrize with a single simple number.
Probably the most important factor is the level of disruption in your sleep architecture. If every time you fall into deep sleep you stop breathing, and that causes you to wake up to restart the breathing, and then you go back to sleep you aren't in deep sleep. If the breathing halts cause you to wake up instantly, then maybe just a few even get to the 10 second minimum to count as an event. Or as few as one or two very long events might cause you severe symptoms that are debilitating. It's easy to construct examples where fewer events could be FAR more destructive than more events...
RE: Comparing AHI Severity with Lowest o2 Sat Severity - srlevine1 - 08-02-2022
(1) I suggest you get a cheap recording pulse-oximeter to track desaturation events,
(2) I suggest you download, install, and use OSCAR to look at the data recorded by your machine. You can also import pulse-oximeter data into Oscar for a more comprehensive analysis.
(3) Please note: from what I have seen, O2 sensors can give artificially low data and dropouts from movement. Also, dirty or discolored fingernails can affect pulse-oximeter results.
(4) The most important metric is how you feel. What type of Apneas can be more revelatory of problems than just looking at an AHI value. The O2 trend can determine if you need to consider supplemental oxygen at night.
I would not obsess over the snapshot data from your sleep study. Remember, you are treating the patient, not the machine.
Best of luck.