this would all depend on the need.
30.3 - direct skilled nursing services to patients
"rehabilitation nursing procedures, including the related teaching and adaptive aspects of nursing, that are part of active treatment and require the presence of skilled nursing personnel; e.g., the institution and supervision of bowel and bladder training programs" http://www.cms.hhs.gov/manuals/downloads/bp102c08.pdf
4th bullet, p27
"in instances when a patient requires a skilled restorative nursing program to positively affect his functional well-being, the expectation is that the program be rendered at least 6 days a week. (note that when a patient's skilled status is based on a restorative program, medical evidence must exist to justify the services. in most instances, it is expected that a skilled restorative program will be, at most, only a few weeks in duration.)" same link, last paragraph p32
"a service that is ordinarily considered nonskilled could be considered a skilled service in cases in which, because of special medical complications, skilled nursing or skilled rehabilitation personnel are required to perform or supervise it or to observe the patient. in these cases, the complications and special services involved must be documented by physicians' orders and nursing or therapy notes." same link, p21
30.2.2 - principles for determining whether a service is skilled
same link, pp 21-26