At 6100 ft in Lake Tahoe I went to 79 on my sats so my husband took me to the ER. They kept me overnight because I failed the walking test plus had a D DIMER level of 823. After a CT found no clots they gave me lovenox injection the next day and sent me back to our condo with supplemental oxyg n. My question is; if I know I will be at higher altitudes and a doc prescribes oxygen will Medicare pay for it