Treating critical illness involves treating the patient as a whole

Treatment of a critical illness requires close, constant attention by a team of healthcare professionals with multiple areas of specialty. It also usually involves the use of specialized equipment like monitors, feeding tubes, intravenous (IV) tubes, catheters, and breathing machines, which may be necessary to keep the patient alive.¹ For these reasons, treatment of critical illnesses is most often done in an intensive care unit (ICU) or trauma centre.

While in the intensive care unit, the patient may not be able to eat food by mouth because of a breathing tube or because it is not safe to eat by mouth. In this case, nutrition may be provided by a tube into the stomach or intestine. This is called a tube feeding or enteral nutrition. Tube feeding formulas are designed to completely replace the oral diet so they include carbohydrate, protein, fat and vitamins and minerals. They may also contain nutrients that are important during illness like omega three fatty acids (fish oil). Alternately, the body may have a hard time breaking down nutrients so a formula that has predigested protein and easily absorbed fat may be necessary. The healthcare professional team will decide which formula is right for the patient’s needs and their situation.

http://www.nlm.nih.gov/medlineplus/criticalcare.html