Qi or chi is called the life force. Qi does have oxygen but
oxygen is not the only Qi. There is different types of Qi,
breathing is the most useful Qi since breathing is part of what
keeps humans going in every day life. There are different types of
breathing you can do to use Qi and develop Qi. So if you look at
humans use breathing to get oxygen and release carbon dioxide which
trees use to make more oxygen. Within oxygen there is Qi and within
carbon dioxide there is Qi. This is why Qi is called the life
force. Water also has Qi, food you eat has Qi, and the Body has Qi.
There is a meeting point in the body where all 3 meet which is in
your stomach, its above the navel. So oxygen and breathing do have
Qi but is not the only Qi, its taught that every living and non
living thing has Qi. Even when a human or animal may pass on
his/her Qi is still here its life force never stops or ends it
moves in a different space. They have many books on Qi and
development of Qi either for health or martial arts. Hope this
helps you to understand, but research of Qi is always in
motion.