God created man with “extra” capacities. At rest, humans only
use a small part of their lungs. While you are sitting reading
this, the lowest part of your own lungs are not well ventilated.
Likewise, the upper part of your own lungs are well ventilated,
but not well supplied with blood. We call this in physiology a
ventilation (air)-perfusion (blood) mismatch. But, at rest we
don’t have to use a high volume of oxygen, so the mismatch
between available air and blood flow (to pick up and deliver the
oxygen) doesn’t matter. When we exercise hard, we have maximal
ventilation (air available) coupled with maximal cardiac output
(blood flow designed to pick up the oxygen). I am fairly certain
that exactly the same thing happens with whitetails. At rest,
they use only a small portion of their lungs and cardiac
capacity. When running all-out, they are making maximal use of
their heart and lungs. So, what a deer is doing physically at
the time it is shot, and what it does for the next minutes and
hours may determine it