I am new to the forum and newly diagnosed. I have been seeing a hematologist to determine a cause for a high RBC count. After a chest x-ray, blood gas, and other blood tests that had negative results, the hematologist recommended a sleep apnea test under the theory that I was not getting enough oxygen at night and thus my body would produce additional red blood cells to compensate for the lack of oxygen needed by my brain. The sleep study showed about an 88% oxygen level and 5 to 6 events per hour. Thus, I have been using a CPAP machine for about 8 days. I was just tested for RBC and it was still high. I am wondering how long do I have to use the CPAP before my RBC count comes down, in fact that is the cause?