Pulse Oximeter Limits.....
--Interesting you should mention your grandfather's arrangement with the pulse-ox, Jon
(BTW; my condolences on your loss. He sounds like a great man)
--an alarm setting at 85 sounds just right. At 83, the O2 sat is dangerously low. It's not an even-increment type thing. Think in terms of Richter Scale and you get the idea.
I'm sure efattah would explain this better: descending from a sat measurement from 85 to 83 is a major change. As the readings get any lower.....the concern about cerebral hypoxia gets significantly higher, and with good cause.
Just for the sake of interest, Anderson, I'll ask if the CO2 readings are of interest. However, I defer to the pros on the website I mentioned. Specifically, any anesthesiologists. They can tell you far more about the changes (and the significance thereof) than I.
Hope this sparks some thoughts about the overall picture....your body responds to many internal signals......somebody must be doing some ongoing research.....I'll be very interested in your findings Anderson, please keep us posted.