"Oxygen homeostasis" is the best I can think of.
Don't forget the other half of the oxygen equation: carbon dioxide is an important waste gas and failing to remove carbon dioxide is just as much a problem as failing to deliver enough oxygen.
You could refer to "oxygen homeostasis" if you wanted to just refer to keeping enough oxygen in distal tissues; as you describe, both respiratory and circulatory systems are relevant for oxygen homeostasis. However, it's hard to separate from the rest of the gas exchange system. Carbon dioxide is very important in determining the rate of respiration, for example, as well as the release of oxygen in peripheral capillaries. Therefore, even if you want to focus on just oxygen, carbon dioxide is going to come up no matter what! As is the function of the vasculature, heart, and lungs: even if these organs have roles outside of delivering oxygen, their functions apply to all gasses exchanged and everything that is transported in the circulatory system. Very little happens in these systems that will only affect oxygen delivery without affecting anything else.
The efficiency of oxygen delivery also depends on what exactly you're inhaling; I find it a bit bizarre to include "smoking" as seemingly part of ordinary biological function, but if you want to go there it's reasonable to consider the role of carbon monoxide and anything else that may interfere with oxygen binding to hemoglobin.