A considerable challenge in the medical profession is to come up with a large number of standard and non-standard abbreviations. NPO in the medical practice stands for “Nil per os” which means nothing by mouth.
Physicians should not only point to medicines in their different forms but also to life acitivities, including food consumption, as for their relevance to the current illness of their patients. Indeed, in many cases of health problems proper shaping of life style and nutrition rules would save doctors and patients as well much unnecessary and dispensable medical prescriptions (see also: Emotional whirl).
Logically, none of the body systems is functioning in separation of the others. Indeed, body systems have to work in a harmony to best enable a certain performance or function at a given time. A dozen of autonomic reflexes (involuntarily) are set up to ensure this functional harmony. Although the extent and intesity of these involuntary reflexes may vary from one person to another and even in the same person depending on the health state for example, it seems that they present inherent physiological rules.
Generally speaking, it is the personal and professional view of the physician whether to consider NPO for a patient where the decision maybe absolutely needed for one case but too superfluous for the other.