Hi Chinnk13..the cause of my chronic hypoxia is from my childhood history of chronic bronchitis..I was always at the hospital, on an outpatient basis for respiratory treatments, as I had bronchitis as a hobby..that seems to have scarred my lungs..I also have had polycythemia (secondary) for at least 13 years..and, along with that, I have hypercalcemia, too ! Have been on oxygen for the past 5 years, but on top of the hypoxia , I now have also developed hypercapnia, so I use the O2 sparingly..ir's alot AND complicated.