Definitely can attest to a CPAP helping sleep quality and have often though of a further increase in RBC from sleep apnea. Ive had one for a year,, and only the last 3 months Ive been using it and way better sleeps where I actually reach the dream state, but wake up now with out headaches or still feeling tired despite sleeping for 7 hours. I will have to see what my lab values are throughout the year, as ive needed to donate 2-3x a year to keep hematocrit in range. Doesn't help I have asthma as well which prob already makes it worse/