Does chametz apply only to what is eaten orally or to any type of nutrition / food regardless of how it is ingested?
There are really two parts to your question. One is: do the rules of Chametz apply regardless how it is ingested?
On Pesach, one may not consume, own or derive benefit from items that contain derivatives of the chameishes minei dagan - wheat, barley, spelt, oats, and rye.
The second part of your question is regarding an IV, where often the one who gets such nutrition is sick. There it would depend on availability of non-Chametz options, how sick, etc. A question for each individual to his local rabbi.
See also from CRC-Chicago that says that most intravenous does not contain Chometz and even if it did one who is incapacitated is allowed to take it.