Exact survival rates are difficult to come by, as studies generally look at specific populations. A 2012 study showed that only about 2% of adults who collapse on the street and receive CPR recover fully. Another from 2009 (PDF) showed that anywhere from 4% to 16% of patients who received bystander CPR were eventually discharged from the hospital. About 18% of seniors who receive CPR at the hospital survive to be discharged, according to a third study (PDF).

So when did the misconception about the effectiveness of CPR begin? Some researchers argue that television created the myth. Between 1994 and 1995, researchers from Duke University watched 97 episodes of “ER,” “Chicago Hope” and “Rescue 911,” taking note of when CPR was administered during each show.

In these dramas, 75% of patients survived immediate cardiac arrest, and two-thirds were discharged from the hospital with full brain function, a stark contrast to the much smaller percentage found by medical studies.