Hi Sam,
a fingertip sensor won't be that useful for freediving as it will tend to drop out due to vasocontriction when you start getting more hypoxic. Do a search because there is plenty on the topic on the DB forum. (I think Eric has tried every pulse oximeter known to man :-) On my friends machine we found an earlobe sensor to work far better. Perhaps you could still atach it to the earlobe, or maybe make some mods. As for how long it takes to see a drop I have atached a graph of a static I did a few years back to give you an idea. It's not a Linear drop, as you can see in my case it doesn't even drop below resting until nearly 3min. In the first few minutes the O2 percent in the lungs starts dropping but blood O2 is still being replaced. This is up until a point where PaO2 becomes too low for efficient oxygen exchange, then blood O2 starts dropping also.
Cheers,
Wal
|
