I have the Vivoactive 5. My VO2 max has alway been toward the upper end of the scale 49-51. I've just recently enabled the Pulse oximeter (two weeks ago). The reading are at the low end of good and outside the ideal range, 93-95% This seems to be odd. No breathing problems or other underlying issues. Had heart stents installed three years ago (no issues), and Prostae remeoved (cancer) no PSA levels showing as of yesterday. So I don't see any issues. How accurate is the Vivoactive 5 for both those catagories?