"like pumping oxygen directly into the blood and then trying to hold your breath - even though you technically don't need to breathe" It's not that simple. You

"like pumping oxygen directly into the blood and then trying to hold your breath - even though you technically don't need to breathe" It's not that simple. You need to get gases in and OUT. You also need more than O2. You need to clear CO2 as well as lactic acid and other biproducts. Some CO in the mix greatly assists exchange. Simply bubbling 02 into your blood is going to kill you with a blood clot. And, RBC's actually curl up into a cylinder shape in your pulmonary capillaries to maximize gas transfer, unlike when they're flying around your circulatory system. Pick up a physio textbook, they're a fun read.