Instead of absolute accuracy, I hope that the pulse oximeter models that people are using are linear with respect to their true saturation level regardless of the actual number presented.
1. Check your level on the ground.
2. Fly up to 12,499 MSL and check your level again.
That is basically what the research article I linked to above did, but without using altitude to bring O2 levels down in the subject (they used some other apparatus to get stable O2 "plateaus"):
METHODS:
The accuracy of 6 low-cost finger pulse oximeters during stable arterial oxygen saturations (Sao2) between 70% and 100% was evaluated...Inspired oxygen, nitrogen, and carbon dioxide partial pressures were monitored and adjusted via a partial rebreathing circuit to achieve 10 to 12 stable target Sao2 plateaus between 70% and 100% and Paco2 values of 35 to 45 mm Hg...
The statement that stands out from the results should be this:
Four of the 6 oximeters tested showed large errors (up to −6.30% mean bias, precision 4.30%, 7.53 ARMS) in estimating saturation when Sao2 was reduced <80%, and half of the oximeters demonstrated large errors when estimating saturations between 80% and 90%
Meaning, they are not linear, and 4 out of 6 fell off in accuracy significantly where you needed it most, 70%-80% saturation levels, which is where cognitive decline really starts to get to you.
The 2 listed as being very accurate were accurate across that critical area, and would be the one I would buy, screen brightness/readability notwithstanding.
Totally agree though, anything above 90% on any of the meters means you are probably fine; on this last flight this weekend though, my wife was at 92% and was getting a headache. A couple of minutes on the O2, headache was gone, so some are more sensitive than others.
If you treat the cheaper/less accurate O2 meters as a binary, I think that would work fine too. As in, anything below 90%, we turn on the O2, don't really care about the particular number.
I was able to get myself set up with an O2 system for less than $200, and refills on a 20cf bottle is about $20, and lasts around 15-20 hours for 2 people at 10k feet.
If you aren't comfortable with DIY oxygen setup, the MH or Aerox are great setups too, and you have it turnkey. For me, it was kind of "I didn't know I wanted it until I had it, now I can't imagine going without it."
You’ve just reached exactly 12,501’ MSL. How long can you cruise there without supplemental oxygen?
A. 30 minutes
B. Forever
C. I need more information.(explain)
Unless this is a trick question, I think the answer is A legally, but you could bump down to 12,499 every 29 minutes and reset the clock
In reality though, I start seeing spots and feel a little breathless at 9k+. Your body actually responds more in correlation to DA than PA.