[Health] Pulse oximeter readings while asleep and awake - what do these readings mean?

[SleepyButHopeful]

Hi all!  I'm new to the forum. 

I was recently diagnosed with sleep apnea, and am trying a bunch of different devices to see if there is an effective alternative to CPAP for me.  I'm experimenting with tracking my SpO2 at night using an overnight pulse oximeter.  I'm using the CMS50F, brand name FaceLake, and analyzing the data using Smart Device Assistant.

The data shows that my SpO2 drops by 3%, for a minimum duration of 10 seconds, many times per hour.  The number of 3% drops per hour ranges from 15 to 47.  This makes sense, since I have sleep apnea and am still doing trial-and-error on treatment devices.

I started to notice something interesting: there were time periods in the data when I knew that I was lying awake in bed with the pulse oximeter on.  Usually this would be time when I was trying to fall asleep.  There would be a clear pattern where the SpO2 was more stable, but still showed some variation.  I zoomed in on just this data, and it showed that my SpO2 dropped by 3% (for a minimum duration of 10 seconds) about 15 times per hour while I was awake.

This seems important for two reasons: first, if this shouldn't be happening at all while I'm awake, I should probably talk to a doctor about it.  Second, if it means my pulse ox readings are inaccurate, it would affect my measuring of my sleep apnea at night.

I did a little experiment, where I wore the pulse oximeter for about 30 minutes while doing my normal desk job during the day.  It also showed about 15 drops per hour.

I realized that the data might be bad because I was moving my hand a lot, so I did another test, resting my pulse-oximeter hand on the desk and keeping it still for an 8-minute reading.  The data showed 4 drops (meaning the 3% drops for at least 10 seconds) during those 8 minutes.

I can see four possibilities:
1. My SpO2 is intermittently dropping in an abnormal way, even while I am awake, and I should investigate this as a possible symptom of a health issue other than sleep apnea.
2. It's normal and healthy to have 3% drops happening every few minutes, while awake, so this isn't a problem.
3. My pulse oximeter is inaccurate, or I'm using it improperly, and it's showing 3% drops that aren't really happening.
4. Pulse oximeters aren't supposed to be that precise, and it's normal for a working pulse oximeter under ideal conditions to show false 3% drops every few minutes.

I've been looking for answers online, and haven't found anything.

Has anyone else run into this?  Any advice?

Thanks so much!

[srlevine1]

All pulse oximeters are sensitive to movement and artificial noise and can show variations that are artifacts. Do you have AFib or wear nail polish on the area used for measurement? My first non-professional pulse-ox was squirrelly, so I just looked at trends over a week or so.

[TechieHippie]

I tried to manage my sleep issues with an oxygen monitor also, for over a year, and have since started using the CPAP. Sounds like you have enough drops per hour that you may need to switch to CPAP, but I understand what you're trying to do here. Everyone's experience will be different. Mine, though, show that just monitoring oxygen was not enough of an intervention; I wasn't getting the deep and REM sleep that I needed.

My experience with managing this through oxygen monitoring alone is that you have to use more data than just the number of drops. The info I look at are number of drops per hour, average SPO2, lowest O2, time under 90%, and time under 94%. What are these numbers typically for you? Before starting CPAP, if my average was 95% or greater, time under 90% was less than 2 minutes, and 75% of my time was above 94%, I called that a good night. But it's only since using my CPAP and getting my average up to 96% and my number of drops down that I'm starting to see more longer term improvement.

3% is measured from a baseline that the device is calculating. If your baseline is 97 or 98, a 3% drop is not as significant especially went awake. So your 3% drop rate is telling you about the variability of your oxygenation, which is important but not everything.

It's normal for oxygen to fluctuate some during the day as well.
I too get oxygen drops when I'm awake and lying down. The airway still relaxes in certain positions and my breath becomes very shallow sometimes. When I get drops during the day, that generally indicates that my nights have not been great and so my overall oxygen saturation is compromised. I think you need to address the sleep apnea and you might see your daytime drops improve.

My suggestion would be to read about positional apnea and soft cervical collars on this board and try some of those for a while and see what happens with your numbers. Also factor in how you are feeling, but realize that if you've had this a long time, you're norm might not be as good as it could be, and you may be having long-term damage to your body.

You can use the alarm if you have one on your oxygen monitor to stop you from going super low at night. I have mine currently set it 87%. If it buzzes I just remind myself to breathe and change positions. But this is a trade-off because you are sacrificing sleep quality for better oxygenation quality.

Lisa

[dataq1]

3% is measured from a baseline that the device is calculating. 

so you need to know what the baseline is first, correct?

How is that baseline value determined?

[TechieHippie]

Reading further, I might have misspoken. It may be just dependent on the previous level, one article said a drop from 97% to 94% would be considered a 3% drop.

[dataq1]

@ Techie,
It would be foolish to give that kind of weight to a single instantantanous reading , because the algorithm to detect a 3 unit shift would be VERY sensitive to artifacts.
But you correctly highlight a problem in that there does not seem to a a consensus standard that defines how a 3 or 4 unit shift is calculated.

[SleepyButHopeful]

Hi all! Thanks so much for the replies. I'll have to read and think about all this at greater length another day, but just wanted to let you all know I appreciate the info.

srlevine1 - Thank you, those are good things to think about. I don't believe I have AFib, but not 100% sure. No nail polish or fake nails or anything like that. The 3% drops show up even when I am awake and deliberately holding my hand completely still. I bought a second pulse oximeter, a hard plastic one that just gives the numbers in realtime, and recorded the variation manually for a few minutes. I saw a number of 3% drops with that one, too; it looked pretty consistent with the readings from the overnight oximeter.

I've started doing an hour-by-hour analysis of each night's data for all the stats available in the Smart Device Assistant. Basal SpO2 (I think this is average or some type of calculated baseline?), minimum SpO2, etc. Basal SpO2 is typically between 95 and 98. I will typically have a handful of spikes (between one and four per night) where it goes below 88. When it does, it spikes down to 81 for I think 30 seconds or less, and then goes back up. I used the BongoRX EPAP last night, and it seemed to reduce or eliminate those low spikes.

I can see significant differences in my oxygen readings at different times of night. Still figuring out whether these different patterns are me lying awake vs asleep, or light sleep vs REM vs deep sleep, or something else.

TechieHippie - I read through your thread and see some commonalities with my overall health. I'm glad CPAP is working for you; that may be where I end up as well! But I want to know how I respond to a wide variety of treatments first.

dataq1 - I agree, I need to learn more about the algorithm and how accurate the monitor is supposed to be.

[srlevine1]

I will leave you with the advice I got from an eminent cardiologist who was a mentor when I thought I wanted to study medicine. He told me to quit obsessing over the numbers because you treat the patient, not the machine. It's all about how you feel.

[TechieHippie]

SleepyButHopeful - yes, I totally understand about trying other things first. That makes sense.

The BongoRX looks interesting. I'm interested for my son who has mild apnea but will not wear a mask. He might be willing to try the BongoRX though, someday.I did a quick search and found that there is another one that looks promising, the ULTepap. The ULTepap has a headstrap but looks stronger pressure-wise according to one source, an article in ScienceDirect titled "Comparison of expiratory pressures generated by four different EPAP devices in a laboratory bench setting" that concludes:
ULTepap generates substantially higher expiratory pressures than Bongo Rx and Theravent.

[SleepyButHopeful]

Hello again!

I will leave you with the advice I got from an eminent cardiologist who was a mentor when I thought I wanted to study medicine. He told me to quit obsessing over the numbers because you treat the patient, not the machine. It's all about how you feel.

Thank you, that is good advice. I think it's a balance, especially since I've been fatigued for so long that I don't trust my ability to notice if I don't feel well. I.e. I might miss a signal from my body, but see it as a reading from some device or other. It is true that ultimately, what matters is good health, and I need to be able to notice directly if I'm feeling better.

Why did you decide not to study medicine?

SleepyButHopeful - yes, I totally understand about trying other things first. That makes sense.

The BongoRX looks interesting. I'm interested for my son who has mild apnea but will not wear a mask. He might be willing to try the BongoRX though, someday.I did a quick search and found that there is another one that looks promising, the ULTepap. The ULTepap has a headstrap but looks stronger pressure-wise according to one source, an article in ScienceDirect titled "Comparison of expiratory pressures generated by four different EPAP devices in a laboratory bench setting" that concludes:
ULTepap generates substantially higher expiratory pressures than Bongo Rx and Theravent.

I had a good experience with the BongoRX. It significantly reduces my number of oxygen drops per hour while sleeping, especially combined with positional therapy (forced side sleeping). Out of the many, many devices I tried, the most successful combo for me personally was the tennis ball attached to the back of my sleep shirt to avoid back sleeping, plus the bongos. However, it didn't fully solve the problem. My next step is trying CPAP again.

I learned that the heated tubing feature on my brand new CPAP machine is broken - didn't work out of the box. Unfortunately, it's the machine itself, not the tube. Replacement tube had the same problem, and the machine shows a heating error. In a way, this is good news for me, because it means my severe congestion issues with CPAP may be limited to that machine.

I've ordered a new machine (ResMed 10) that also has a heated tube, and will begin the process of attempting to get a refund or store credit for the broken ResMed 11. I figured that if I tried for an exchange, the process might take a while, so I just directly ordered it. Not the smartest financial move, but I'm tired of being sleepy and wanted to try the new machine fast with a minimum of hassle.

Eventually, I want to do a long writeup about all the devices I tried, and how I measured my results using pulse oximetry.