In a scene in the film Dumb and Dumber, Lloyd Christmas, played by Jim Carrey, sees a fellow diner collapse in a restaurant. The man clutches his abdomen and complains of an ulcer. “It’s OK,” Christmas reassures the victim, “I know CPR.” The man resists mouth to mouth resuscitation. “It’s a lot easier if you just lay back,” Christmas notes.

While perhaps not quite as ignorant as the well meaning Christmas, many non-clinicians hold rosy views about the nature and effectiveness of cardiopulmonary resuscitation (CPR). Several studies have underlined their misplaced optimism: in one, the 269 respondents reported a mean expected survival rate for CPR of 65%1; in another, 81% of respondents over 70 years old believed the likelihood of leaving the hospital after a cardiac arrest to be at least 50%.2 The real figure, for all in-hospital cardiac arrests, is roughly 14%, and many survivors will have new functional or neurological impairments.3

The illusion of CPR’s effectiveness can lead patients and relatives to make ill informed choices about care at the end of …