Just did a short experiment. I went outside {temp 45F/cloudy-riny} and collected a small cart of fire wood. Perhaps 2-3 min. Result, SOB! so I sat down and did a series of PLB's, while monitoring O2. At first my O2 was 87 {typically I'm above 90}, after a few PLB's claimed up to 90, and on to 96. I plan on doing the insurance ind test of 6min on the treadmill and monitor O2. Is the above effect common?