Oxygen lowers co2 levels, gives the lungs high oxygen levels to oxygen deprived muscles and organs. Lowers the acidic pH your body is in when in a cardio intense fight I'm aware of Carwin using an o2 inhaler, but this is a fad and isn't therapeutic enough to have an effect on an air sucking athlete. Oxygen by non-rebreather mask or simple mask between rounds would significantly help the athlete recover along with their corners cooling the body with ice. is it not allowed by athletic commissions? UFC? hell is it considered a PED nowadays?