I bought a Contec CMS50D pulse oximeter on eBay, based on a review published recently in Aviation Consumer. It arrived yesterday. Today, a planned all-day meeting finished at lunch time, and the weather was good, so I took some banked time off in the afternoon. I installed the Aerox oxygen tank in the forward baggage bay, ran the O2 lines into the cockpit, and went flying.

I measured the blood oxygen satuation at 9,500 ft, with the oxygen OFF, and found that it was about 94% of my sea level baseline reading. I donned the cannula, adjusted the O2 regulator, waited a couple of minutes then measured the oxygen saturation again. I found that it had increased to 99% of the sea level baseline. I climbed to 12,500 ft, and found the blood oxygen saturation was 98% of the sea level value with the oxygen ON and 86% of the sea level value with the oxygen OFF.

Conclusion: The oxygen system is working as expected. It should prove usful on some cross country flights, either where there are strong tailwinds available above 10,000 ft, or climbing above 10,000 ft will avoid icing conditions at lower altitude.