Normal oxygen saturation levels while sleeping?

Hi all -

New member here.

Trying to get a definitive answer as to whether it’s normal for oxygen saturation to decrease slightly while sleeping, as our respiratory rate generally decreases. I’m pretty sure the answer is yes; but then the question becomes … how much of a decrease is normal, or acceptable?

Been doing a lot of research, and seeing lots of different numbers. Some websites indicate anything below 95% is a desaturation, some say 93, even found one (with citation) that said 90% is normal. Most websites just don’t address it, and treat oxygen saturation as a constant (which maybe it should be.)

I’m asking because I was diagnosed with mild sleep apnea – an AHI of 6. However, since then, I have made a number of adjustments including Breath Right strips, saline nasal spray, side sleeping position, losing weight, tongue exercises, and just better general sleep hygiene. Can’t tolerate CPAP.

I think these are all working. Since none of us can take a sleep test every week, I’ve been relying on an overnight pulse oximeter to at least measure my oxygen saturation levels. Most nights, I am averaging about one event per hour – with the criteria on the oximeter being a drop of 4%. My low oxygen level for the night is usually 89 or 90%, and that is usually for 10-20 seconds at most. From this perspective, I don’t have sleep apnea.

However, I am getting readings of between 90 and 94% saturation that are a little more substantial. Last night for example, I was in that range for 18% of the night … although I think a lot of that time was at 94%. I would have to spend an hour studying the details to break it down exactly. Anyway, it seems to be between 5 and 15% of the night most nights.

Hence my concern. If 90% saturation while asleep is okay, then I don’t really have a problem. At 92%, might still be okay. At 93%, a little concerned. At 94%, it’s something to take a more serious look at.

Any advice/thoughts would be greatly appreciated. Cheers!

The study at the link below concluded that there is strong correlation between oxygen desaturation index (ODI) and sleep apnea hypopnea index (AHI). ODI is defined as a drop of 3% in mean oxygen levels for 10 seconds or more. The study further concluded that ODI was a very economic way of monitoring for sleep apnea, and those with an ODI of 20 or greater should be further evaluated with a formal sleep apnea test.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8889990/

Much appreciated Sierra, and especially relevant since last night, my ODI was 3.6. Good to know that I’m barking up the right tree.

However, I’m not sure it addresses my central question head on. I’ll try stating it another way for the forum:

If a AHI event is defined as a drop of 4% for 10 seconds, would a drop from 98% to 94% for 10 seconds be counted on a sleep test as an event since the lowest level is still an acceptable saturation level?

How about 96% to 92%, or 94% to 90%? I’m trying to determine where the cutoff might be.

The one time I did a sleep study they said my oxygen dropped to 68% and I was in good health at age 49 and not taking any medicine. So yours may not be that bad.