>>the body’s immune system requires oxygen to do repairs on injuries

This is also why wound care is so important for diabetics. Not only is hemoglobin impaired by glycolytic damage(A1C), but long term higher-than-normal glucose levels also changes RBC morphology, leading to anemia, particularly in the extremities (after the blood is oxygenated, each tissue takes O2 as the blood passes, the extremities are at the end of the supply line).

I'm still surprised that standard of care does not include ubiquinol with any statin. And, to the extent that heart failure is a mitochondrial issue, I wonder why I'm not finding clinical studies examining methylene blue for heart failure. There's evidence for neuronal support (many dementias) - and it's standard of care for cardiac surgery.

Finally, the heart doesn't so much pump blood back up from the legs as it's done my muscular activity (e.g. walking) The veins have one-way valves that enable vein compression by muscular activity to move the blood towards the heart. It's an issue in a weightless environment.