Heart attack patients whose hearts have stopped beating and who receive cardiopulmonary resuscitation (CPR) from bystanders fare better if their resuscitators skip the rescue breaths and do only chest compression, according to a study led by researchers at Washington University School of Medicine in St. Louis.
The study, published online on Oct. 15 in The Lancet, determined that the chest compression-only method of CPR improved survival rates over standard CPR.
Standard CPR involves alternating chest compressions with rescue breaths.
“We looked at data from three studies,” says principal investigator Peter Nagele, MD. “Individually, the studies were ‘underpowered’ statistically and could not show a survival benefit. Basically, there were too few study subjects to determine whether one method of CPR improved survival more than another, but when we combined all three studies, there was a significant increase in survival when witnesses were told by 911 dispatchers to provide chest compression only.”
Nagele, an assistant professor of anesthesiology and chief of trauma anesthesiology at Barnes-Jewish Hospital in St. Louis, and his team combined the data from the three studies in a meta-analysis and were able to analyze survival rates in more than 3,700 cardiac arrest patients who received either standard CPR or chest compression only. Those smaller studies had suggested chest compression-only CPR may improve survival – one noted a 14 percent increased survival to hospital discharge, while a second reported a 24 percent improvement in 30-day survival – but because of relatively small numbers in those studies, it was impossible to conclusively determine which of the two CPR methods was actually better.
But analyzing all three studies, Nagele’s team determined that survival improved by 22 percent when bystanders called 911 and were advised by the dispatcher to do chest compression-only CPR.
“When a person goes into cardiac arrest because of a problem with the heart, that individual normally has plenty of oxygen in the body,” Nagele explains. “So rescue breaths aren’t as vital to survival as trying to keep blood flowing as regularly as possible. However, if cardiac arrest is secondary to trauma, drowning or a problem not directly related to heart function, then it is advisable to do standard CPR that includes rescue breaths. In those cases, getting oxygen into the system is crucial.”
The findings do not apply to children with cardiac arrest, Nagele stresses.
“It is very uncommon for kids to go into cardiac arrest due to a primary heart problem,” Nagele says. “If cardiac arrest does occur, it’s likely to be secondary to a severe asthma attack, an allergic reaction or something else unrelated to the heart. Under those circumstances, the body needs oxygen. I strongly recommend chest compression and rescue breaths in kids.”
Whether a bystander had previous training in CPR had no effect on patient survival in this study. When emergency dispatchers recommend only chest compression, it is relatively easy for a bystander to find the proper area of the chest, begin doing compressions and keep going until emergency medical technicians arrive, Nagele says.
Part of the reason earlier studies could not verify a statistical benefit from the chest-compression-only technique was that the patient survival rate hovers around 10 percent. Even with 1,000 or 2,000 patients in a study, the total number of survivors was small. Only by combining data from all three studies to generate larger numbers were the investigators able to confirm improved survival.
The research team, which included investigators from the Medical University of Vienna in Austria, determined that a 20 percent improvement in survival related to chest compression-only CPR in cardiac arrest patients in North America and the European Union could save as many as 5,000 to 10,000 lives each year.
The new study also found that the benefit occurred only when 911 dispatchers coached bystanders to use chest compression-only CPR. In several uncontrolled studies that simply asked bystanders whether they did only chest compressions or standard CPR, the investigators found no survival benefit with the chest compression-only technique.
Nagele says his findings suggest that if someone nearby has a heart attack, it’s important to first call 911, and then begin chest compressions. He says if it takes several minutes for help to arrive, it also may become necessary to begin rescue breaths, but for the first five to 10 minutes, chest compressions are more important.
“The heart doesn’t literally stop during cardiac arrest,” he says. “It gets super excited and electrically very active, and the only way to get it back into rhythm is with an electrical shock, a defibrillation. By doing chest compression-only CPR, a bystander is basically buying time until a paramedic with a defibrillator can jump-start the heart.”
Whether by coincudence or as a result of this study, the American Heart Association has announced that it is re-arranging the ABCs of cardiopulmonary resuscitation (CPR) in its 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, published in Circulation: Journal of the American Heart Association.
Recommending that chest compressions be the first step for lay and professional rescuers to revive victims of sudden cardiac arrest, the association said the A-B-Cs (Airway-Breathing-Compressions) of CPR should now be changed to C-A-B (Compressions-Airway-Breathing).
"For more than 40 years, CPR training has emphasized the ABCs of CPR, which instructed people to open a victim's airway by tilting their head back, pinching the nose and breathing into the victim's mouth, and only then giving chest compressions," said Michael Sayre, M.D., co-author of the guidelines and chairman of the American Heart Association's Emergency Cardiovascular Care (ECC) Committee. "This approach was causing significant delays in starting chest compressions, which are essential for keeping oxygen-rich blood circulating through the body. Changing the sequence from A-B-C to C-A-B for adults and children allows all rescuers to begin chest compressions right away."
In previous guidelines, the association recommended looking, listening and feeling for normal breathing before starting CPR. Now, compressions should be started immediately on anyone who is unresponsive and not breathing normally.
All victims in cardiac arrest need chest compressions. In the first few minutes of a cardiac arrest, victims will have oxygen remaining in their lungs and bloodstream, so starting CPR with chest compressions can pump that blood to the victim's brain and heart sooner. Research shows that rescuers who started CPR with opening the airway took 30 critical seconds longer to begin chest compressions than rescuers who began CPR with chest compressions.
The change in the CPR sequence applies to adults, children and infants, but excludes newborns.
Other recommendations, based mainly on research published since the last AHA resuscitation guidelines in 2005:
- During CPR, rescuers should give chest compressions a little faster, at a rate of at least 100 times a minute.
- Rescuers should push deeper on the chest, compressing at least two inches in adults and children and 1.5 inches in infants.
- Between each compression, rescuers should avoid leaning on the chest to allow it to return to its starting position.
- Rescuers should avoid stopping chest compressions and avoid excessive ventilation.
- All 9-1-1 centers should assertively provide instructions over the telephone to get chest compressions started when cardiac arrest is suspected.
"Sudden cardiac arrest claims hundreds of thousands of lives every year in the United States, and the American Heart Association's guidelines have been used to train millions of people in lifesaving techniques," said Ralph Sacco, M.D., president of the American Heart Association. "Despite our success, the research behind the guidelines is telling us that more people need to do CPR to treat victims of sudden cardiac arrest, and that the quality of CPR matters, whether it's given by a professional or non-professional rescuer."
Since 2008, the American Heart Association has recommended that untrained bystanders use Hands-Only CPR — CPR without breaths — for an adult victim who suddenly collapses. The steps to Hands-Only CPR are simple: call 9-1-1 and push hard and fast on the center of the chest until professional help or an AED arrives.
Key guidelines recommendations for healthcare professionals:
Effective teamwork techniques should be learned and practiced regularly.
Professional rescuers should use quantitative waveform capnography — the monitoring and measuring of carbon dioxide output — to confirm intubation and monitor CPR quality.
Therapeutic hypothermia, or cooling, should be part of an overall interdisciplinary system of care after resuscitation from cardiac arrest.
Atropine is no longer recommended for routine use in managing and treating pulseless electrical activity (PEA) or asystole.
Pediatric advanced life support (PALS) guidelines provide new information about resuscitating infants and children with certain congenital heart diseases and pulmonary hypertension, and emphasize organizing care around two-minute periods of uninterrupted CPR.
The CPR and ECC guidelines are science-based recommendations for treating cardiovascular emergencies — particularly sudden cardiac arrest in adults, children, infants and newborns. The American Heart Association established the first resuscitation guidelines in 1966.
The year 2010 marks the 50th anniversary of Kouwenhoven, Jude, and Knickerbocker's landmark study documenting cardiac arrest survival after chest compressions.