[guylhem]

I think you are mistaking parenteral and enteral. The difference is where the tube goes. Feeding someone with a tube is difficult only if the tube goes into the bloodstream.

If it goes to the stomach, a normal meal + a blender is all that is needed (or the fancy and overpriced equivalents sold for a small fortune to the hospitals)

If it goes to the bloodstream, it can't be food, and the problem is we don't exactly know yet everything it should contain.

For example, I remember in ICUs in the 1990s and early 2000, carnithin was the topic of many discussions. See for example http://www.ncbi.nlm.nih.gov/pubmed/2115077

There must be a new fad now.