Nearly 383,000 cardiac arrests occur outside of hospitals each year in the U.S., 88 percent of which occur at home. Effective cardiopulmonary resuscitation (CPR), even when administered by an untrained bystander, can double or even triple a patient's chances of survival. Unfortunately, only about 8 percent of people who suffer cardiac arrest outside of the hospital survive.
The depth and rate of chest compressions during CPR affects the recovery and survival rates of patients, according to a review presented by UT Southwestern Medical Center emergency physicians.
The researchers from UT Southwestern published their findings from two independent studies in Circulation and Critical Care Medicine. The studies underscored the importance of quality CPR, including both chest compression depth and the rate at which they are given, on survival rates.
Compression depth: Deeper is not necessarily better
Previous research and guidelines suggested deeper compressions were superior. In fact, the American Heart Association (AHA) recommends a compression depth of at least 5 cm (2 inches) in adults, and gives no upper limit for compression depth.
Investigators in the UT Southwestern review found that compressions greater than 5.5 cm resulted in decreased survival rates. The researchers say the reduced survival rates may be due to collateral damage inflicted on internal organs during these deep compressions.
The reviewers say it takes about 60 pounds of pressure to move the sternum 5 cm, which requires quite a bit of thrust. Under pressure to save a life, however, a strong firefighter or overly enthusiastic volunteer may exceed that pressure and compress the chest too deeply.
Compression rate: Staying alive by rowing your boat
The research group, headed by Professor of Emergency Medicine and Internal Medicine at UT Southwestern Dr. Ahamed Idris, determined that the rate of chest compressions was the most important factor in administering CPR. The group found that the rate of 100 to 120 compressions per minute is optimal for patient survival.
The AHA recommends applying at least 100 compressions per minute but does not list an upper limit. Idris and his group of researchers found that more than half of all responders give compressions too fast.
In their review, the scientists determined that only about a third of all responders performed 100 compressions per minute and that a full 20 percent of responders applied compressions at a rate greater than 140 compressions per minute.
The AHA recommends using the song, "Staying Alive" by the BeeGees, as a way to measure chest compressions. Idris, who is also director of the Dallas-Fort Worth Center for Resuscitation Research, says that the song, "Row, Row, Row Your Boat" is a good measure to reach the 100 to 120 compression mark.
The AHA's guidelines suggest a two-step procedure: Call 911 then begin chest compressions. Idris would like to add that chest compressions should continue until paramedics arrive.
The research team at UT Southwestern will continue to participate in and oversee clinical trials aimed at testing early delivery interventions for cardiac arrest and serious trauma as part of a federally funded consortium that intends to advance prehospital emergency care. These studies can improve the quality of cardiopulmonary resuscitation and patient survival rates.
