Kidney cancers can be cystic, and differentiating between a single benign cyst of the kidney and a kidney cancer can occasionally be a problem. When many cysts are present, as in polycystic renal disease, the distinction is easier. Cysts may also be caused by some parasitic infections.
It will actually collect the oxygen in the ambient air (~21%) and convert it into a concentration of around 85-94%. One of the main reasons you would want a concentrator over a tank and regulator would be when you are using a lot of oxygen for taking ozone saunas or ozonating oils.
Discovery Health How much oxygen does a person consume in a day?. A person breathes 7 or 8 liters of air per minute. Air is about 20% oxygen. But when you exhale, your breath is about 15% oxygen, so you consumed about 5%. Therefore, a person uses about 550 liters of pure oxygen each day. As for exhaled CO2, this site.