Accuracy of SPO2 readings

[WilliamHamilton]

Has anyone compared the SPO2 readings of the Fitbit Versa 2 against against a dedicated oximeter?

My overnight SPO2 scores have ranged from 92 to 97.  I know about needing several hours of "good sleep", wearing it correctly, keeping it well charged, etc, and I'm confident that I have accounted for those variables.

The lower numbers would concern me except that:

• The values are inconsistent from day to day
• It succeeds in reading at 50% of the time at best
• There are no symptoms that you'd expect with low oxygen

Before I purchase an oximeter to validate the fitbit measurement, I thought I'd ask for results by other people who have already done this.  Anyone?

[MrMarv]

@WilliamHamilton -

Just a couple thoughts...

I would expect my SpO2 during sleep to drop from a waking hour measurement as my heart rate as well as respiratory rates both drop and the need for oxygen to support activity dropping.

I would expect my SpO2 to be a little higher on warm evenings as it is common for an individual's heart rate to increase when their core body temperature rises, allowing the blood to spend more time in the outer layers of the skin - and your Resting Heart Rate will also increase during those occasions of warm/humid nights.

Both of the above, including the RHR increase, were my actual observations for the short period of time I used the SpO2 clock face.

I no longer use the clock face. Not because I question the data collected, but because I see no reason to see my SpO2 readings every time I raise my wrist during the day. And to have to tap through to see each stat to find the stat I want and not being able to remove the stats I really don't need to see all of the time was bothersome.

Clean watch face, yes. Well thought out design - - - NO.

[WilliamHamilton]

MrMarv, for what it's worth when I set the clock face to heart rate, steps or whatever it stays there even when the watch toggles to sleep and awake.  I agree it's pointless to see the same number all day, or several days as the case may be.  I like the large number size for the heart rate.

Although your answer was informative, it doesn't really address my question so I can't mark it as the solution but thanks.

[MrMarv · Accepted solution]

@WilliamHamilton 

This has been bugging me - the solution mark isn't the motivation as I have many thanks for the right answer with no solution mark. It is just that I could have sworn that I had read a post that agreed with my observations about heart and respiratory rate during sleep.

I couldn't find the post announcing the clock face and the mention of lower values, but I did find the manual. 

Most of the information that applies to your original post can be found on page eight of the SpO2 manual at:

SpO2 manual 

Page four of the manual may be of interest, as well.

Still no discussion about warmer sleeping conditions, but if the heart rates are higher it follows the SpO2 may be a little higher, too.

You may have found this already, If so, that's good. If not, I hope this helps.

[WilliamHamilton]

Plenty of medical studies show lower SPO2 during sleep, no need to find a post for that.

The question is, has anyone validated their fitbit SPO2 readings against a medical device?  That's all that I'm asking.

I noted variations - just to explain why I'm asking (not asking why there are variations).

[Rksy32]

Yes, I have. Last night I kept getting a reading of 94-96%. I went and got my medical grade device..it read 98-99%   I did a reading off and on through out the day, just to compare. It was on average 3-4 points off Everytime. I'm guessing it's just like a blood pressure monitor you buy from the store vs the machine they use in doctor's offices or hospitals- always off by a few.  

Moderator edit: format. 

[NEPA_MacGuyver]

I have a Versa 3 and have found that it reads about 2.5% lower than a medical grade meter. I really never see a reading over 98% on my Versa, as I’m pretty sure that would actually be 100% by virtue of the 2.5% error and the watch only showing whole numbers, which means 97.5% would round up to 98%. Another thing annoys me it the huge amount of filtering and averaging that it does to the heart rate for the graphing. I have occasional tachycardia, and will feel the increase in my heart rate. I’ll watch the rate on the watch or app and see highs in the 150-160 range, but later the graph shows a peak in the 120-130 range. I’ve come to the conclusion that the Versa is really just a toy, and not suitable for any real health tracking purposes. 

[jtoast]

My wife is in the medical field and, out of an abundance of COVID caution, checks me on a regular basis with a medical grade O2 monitor lol. On the monitor, I am consistantly in the 96-98 range. On the other hand, my watch is consistantly in the 93-94 range.

I'm sure part of that is because it's lower overnight but I'm going to say it's more about the watch just isn't all that accurate.

[Lmh1950]

I have an oximeter and I check it periodically against my FitBit. It is always 4%-5% lower on the fit bit then the actual percentage rate!

[Zaaaaa]

I just had a similar situation where the fit bit says 93 but the medical Device says 99

[Zaaaaa]

Mine is 7 percent lower on the Fitbit 

[Yugogirl]

I am going through the same thing. My fitbit is giving me awful numbers - down to 85% for 4+ mins multiple times a night ...which concerned me as I didn't feel I was getting good sleep, but also didn't think I had sleep apnea. I am going to see my doctor, but bought the O2 ring in the meantime and it's readings are perfect for me - 95+. It is very inconsistent with the fit bit. Will see if I should do a sleep study. My sleep is horrible generally, so even if it isn't sleep apnea hopefully I find something that helps.

[Cathleo5]

It’s possible also that the difference is that the watches are a reflectance based measurement versus finger oximeters that pass light through a finger.

https://indianexpress.com/article/technology/gadgets/pulse-oximeters-vs-spo2-smartwatches-why-you-sh...

SpO2% transmittance measurements were more accurate than reflectance measurements for decades. Not sure if that’s still true of medical grade reflectance versus medical grade finger transmittance instruments used in hospitals. The article above is the first one I found in a 30 second Google search, there are many more but some don’t provide free access. I think the only thing that a watch oximeter should be used for is trending… e.g. do you see a decrease compared to what you normally see with the watch monitor.

Charge4. 95% vs Amazon finger oximeter 97-98% (I don’t seriously think it’s medical grade even though they claim to be.)