Journal Report
12/06/2007

Out-of-hospital cardiac arrest survival rates similar after bystanders delivered standard CPR or only chest compressions

American Heart Association rapid access journal reports

DALLAS, Dec. 11 – A simpler version of bystander-delivered cardiopulmonary resuscitation (CPR) that skips mouth-to-mouth resuscitation may be just as effective for out-of-hospital cardiac arrest victims as standard CPR, according to two studies published online in Circulation: Journal of the American Heart Association.

“If you hesitate to do CPR, remember that chest compressions only is better than doing nothing,” said Katarina Bohm, R.N., whose 15-year retrospective study of 11,275 out-of-hospital cardiac arrests in Sweden found similar one-month survival from standard CPR (St-CPR) which includes mouth-to-mouth resuscitation and chest compressions and the simpler version, which uses only chest compressions (CC-CPR).  She conducted the research as part of her doctoral thesis in cardiology at Prehospital Center, Department of Cardiology, Stockholm.

In a separate five-year prospective cohort study in Japan’s Osaka district researchers analyzed 4,902 witnessed cardiac arrests.  They found higher one-year survival with favorable neurological outcome when bystanders provided either the simpler version of compression-only CPR or standard CPR compared to no CPR when emergency medical personnel arrived within 15 minutes to provide additional treatment.  This study also suggests that CC-CPR may be superior to St-CPR when provided within 5 minutes of cardiac arrest, and rescue breathing may be of some help for very prolonged cardiac arrests.  The study was the first investigation of CPR methods in which time frame was a central hypothesis, said Taku Iwami, M.D., Ph.D., an assistant professor at Kyoto University Health Service.

During a cardiac arrest the heart is unable to pump blood, usually because of abnormal electrical signal within the heart, often due to coronary heart disease.  Death usually follows within minutes unless bystanders provide immediate CPR to keep oxygen-rich blood circulating until a device called an automated external defibrillator (AED) can be used to shock the heart to terminate the abnormal rhythm and allow a normal heart rhythm to return.

Standard CPR (St-CPR) features a pattern of breaths delivered mouth-to-mouth plus rhythmic chest compression.  The American Heart Association recommends 30 compressions for every two breaths during bystander CPR.

In the past decade, researchers have investigated whether chest compression only CPR (CC-CPR) might have a role in the chain of survival — the bridge between a witnessed cardiac arrest, the use of an AED and the advanced care of emergency response personnel.

“The advantages of CC-CPR include its simplicity, which in turn may lead to more out-of-hospital cardiac arrest patients receiving CC-CPR from the more hesitant potential rescuer,” Bohm said.

Bohm’s retrospective study used data on 11,275 out-of-hospital cardiac arrest patients compiled in the Swedish Cardiac Arrest Register.  The patients experienced out-of-hospital cardiac arrest from a variety of causes — including heart rhythm disturbances and drowning — from 1990–2005. 

Of those patients, 73 percent (8,209) received St-CPR and 10 percent (1,145) received CC-CPR from bystanders.  Survival among the St-CPR group was 7.2 percent compared to 6.7 percent for CC-CPR cases — a statistically insignificant difference, Bohm said.  The outcome from each method remained similar even after researchers adjusted for differences between the two groups at baseline, such as age and gender, and for differences in ambulance arrival time.

For unknown reasons, 1,921 patients (17 percent of the total) had received only mouth-to-mouth resuscitation, without any chest compressions.  Although excluded from this comparison of St-CPR and CC-CPR, that group had the lowest one-month survival (4.5 percent), researchers said.

“During the 15-year study, St-CPR was the only form recommended or taught,” said Leif Svensson, M.D., Ph.D., senior researcher for the study and associate professor at the Karolinska Institute, Stockholm Sweden.  “From 1990 to 2000, the recommended ratio was one rescue breath for every five chest compressions.  Between 2000 and 2005, it was two breaths for every 15 chest compressions.  The current international guideline is two breaths per 30 chest compressions.”

Both studies sought to address the poor overall survival from out-of-hospital cardiac arrest, and the need to improve the chain of survival.  According to the 2007 Heart Disease and Stroke Statistics Update from the American Heart Association, on average less than one third of out-of-hospital cardiac arrest victims receive bystander CPR and only 6.4 percent of victims survive to hospital discharge.  However, immediate bystander CPR combined with the prompt use of an AED can double or triple a cardiac arrest victim’s chances of survival.

“We consider standard CPR when performed by professionals or well-trained laymen to be the method of choice,” Svensson said.  “However, studies have shown that many rescuers fail to respond or respond insufficiently, which in some cases is due to fear of contagion or repugnance.”

In the Osaka study of 4,902 witnessed cardiac arrests in which cardiac problems were thought to be the cause, 783 patients received St-CPR and 544 received CC-CPR. 

“For cases in which CPR was needed for less than 15 minutes, one-year survival with favorable neurological outcome was virtually the same: 4.3 percent (19/441) for the simpler CC-CPR, and 4.1 percent (25/617) for St-CPR, which is significantly higher than that in cases who received no CPR (2.1 percent),” Iwami said.  “The difference between the two methods fell short of statistical significance, but CC-only CPR had better outcomes than no CPR.”

For cases in which CPR was needed for more than 16 minutes, one-year survival with favorable neurological outcome was very poor irrespective of type of CPR: 0 percent (0/92) for the simpler CC-CPR, 2.2 percent (3/139) for St-CPR, and 0.3 percent (2/624) for no bystander  CPR.   Although mouth-to-mouth resuscitation may be of some help for very prolonged cardiac arrests, our data show that there are few victims who actually received the benefit of bystander started mouth-to-mouth resuscitation, he said.

One of the limitations of the Japanese study is the lack of data on the quality of chest compressions—its force, rate and continuity without interruption—are key to the technique’s effectiveness.

“Currently, the rate of bystander CPR remains low, perhaps because conventional CPR requires that bystanders perform a complicated task in an emotionally intense situation.  Cardiac-only resuscitation [CC-CPR] is a much simpler technique that is easier to teach, learn, remember and perform.  It is impressive that over 40 percent bystanders chose to perform cardiac-only resuscitation despite no training programs for cardiac-only resuscitation,” Iwami said.

“Our findings based on a large-scale population-based study are consistent with previous studies in spite of the substantial differences in study designs, patient populations, and emergency medical systems, which indicate that the clinical data supporting the effectiveness of cardiac-only bystander resuscitation are quite robust.” Iwami said.

Svensson said that although their study suggests a simpler version of CPR that drops mouth-to-mouth resuscitation might be as effective as St.-CPR, it is better to confirm their findings by a prospective, randomized double-blind trial before any discussion on changing guidelines should occur.  

Iwami’s group also agreed further research is needed but added that it is difficult to control the bystander’s performance.  

The Swedish Heart and Lung Foundation and Stockholm County Council funded Bohm and Svensson’s study.  

Svensson and Bohm’s co-authors are: Marten Rosenqvist, M.D., Ph.D.; Johan Herlitz, M.D., Ph.D.; and Jacob Hollenberg, M.D.

Iwami’s study was supported by a grant from the Japanese Ministry of Education, Science, Sports and Culture, and the Ministry of Health, Labor and Welfare. 

Iwami’s co-authors are: Takashi Kawamura, M.D., Ph.D.; Atsushi Hiraide, M.D., Ph.D.; Robert A. Berg, M.D.; Yasuyuki Hayashi, M.D.; Tatsuya Nishiuchi, M.D.; Kentaro Kajino, M.D.; Naohiro Yonemoto, M.P.H.; Hidekazu Yukioka, M.D., Ph.D.; Hisashi Sugimoto, M.D., Ph.D.; Hiroyuki kakuchi, M.D., Ph.D.; Kazuhiro Sase, M.D., Ph.D.; Hiroyuki Yokoyama, M.D., Ph.D.; and Hiroshi Nonogi, M.D., Ph.D.  

Editor’s note: The American Heart Association’s 2005 guidelines recommend compressions-only CPR for anyone who is unwilling or unable to provide ventilations while providing chest compressions.  Experts continue to promote a combination of rescue breathing and chest compressions for victims of cardiac arrest due to non cardiac causes, like near-drowning or electrocution, and almost all victims of pediatric cardiac arrest.   For more information about community CPR training, visit cpranytime.org. 

NR07-1250 (CIRC/Svensson-Bohm-Iwami)

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