From Angela Morrow, RN, former About.com Guide
Make your wishes regarding end-of-life care known.
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Instituting a Do Not Resuscitate or a No Code Order
In a hospital, an order to withhold resuscitation is commonly called “no code." Only a doctor can write an order for a patient to be “no code."
(...) If you or your loved one is in a nursing home, you would need to sign a Do Not Resuscitate - DNR form to formally let the nursing home’s staff know that you don’t want to be resuscitated. (...) Most nursing homes have forms in addition to DNRs, sometimes called "Preferred Intensity of Care" (PIC) forms. These forms allow you to make decisions about whether or not to be hospitalized or receive antibiotics, IVs and artificial nutrition.
More: http://dying.about.com/od/planningahead/a/DNR.htm