NOS3 and myalgic encephalomeyelitis/chronic fatigue syndrome: Oxygen/ozone therapy, therefore, is used as a complementary treatment of many diseases, including conditions characterized by high oxidative stress as chronic fatigue syndrome (CFS) [13], hypoxic state, and ischemic syndromes, in which by increasing the levels of eNOS ozone rends physiological levels of nitric oxide and thus protection from damage [14].