CPR by Chest Compression Alone
July 1, 2000 4 minutes read
CPR by Chest Compression Alone
abstract & commentary
Synopsis: Dispatcher-instructed chest compression-plus-ventilation is not superior to dispatcher-instructed chest compression-only in the emergency management of cardiac arrest.
Source: Hallstrom A, et al. N Engl J Med 2000;342: 1546-1553.
For many years, the recommended technique for bystander cardiopulmonary resuscitation (CPR) has involved Airway management, rescue Breathing and chest compression-induced Circulation (ABC CPR). Recently, the advisability of including ventilation in basic CPR has been questioned. In this paper, Hallstrom and colleagues report the results of a study that compared CPR by chest compression with and without mouth-to-mouth ventilation.
The trial was conducted in Seattle, Wash., where fire department dispatchers send an emergency medical service (EMS) team to the site of reported cardiac arrests. During the trial, the dispatcher asked if CPR was already being performed and, if it was not, asked the callers if they were willing to be instructed in CPR. The set of instructions given was for CPR using chest compressions either with or without mouth-to-mouth ventilation as randomly assigned by a computer at the dispatcher’s console. The primary end point of the study was survival-to-hospital discharge with secondary end points of survival-to-hospital admission and estimated late neurologic function in survivors.
This report included data from 520 randomized episodes of cardiac arrest. The average patient age was 68 years, 64% were male, 58% of the episodes were witnessed, and 88% occurred at home. EMS response time averaged 4.0 minutes. Ventricular fibrillation or tachycardia was the first rhythm documented during 43% of the episodes. Asystole or pulseless electrical activity was the first rhythm documented in the remaining cases.
CPR instructions were completed in 80.5% of the cases where only chest compression was advised vs. 61.6% of cases where ventilation was also advised. A total of 64 patients survived to hospital discharge: 10.4% in the compression-plus-ventilation group vs. 14.6% in the compression-only group (P = 0.18). This trend in favor of compression-only instructions persisted after adjustment for characteristics of the episode.
Hallstrom et al conclude that dispatcher-instructed chest compression-plus-ventilation was not superior to dispatcher-instructed chest compression-only in the emergency management of cardiac arrest.
Comment by John P. DiMarco, MD, PhD
It has been shown that bystander CPR can improve cardiac arrest survival. Bystander CPR extends by several minutes the window during which successful restoration of normal rhythm can result in meaningful recovery. Unfortunately, bystander CPR is infrequently performed, and surveys have shown that the quality of CPR is often suboptimal even when performed by individuals previously trained in the technique. Recently, a Bethesda Conference on Emergency Cardiac Care (J Am Coll Cardiol 2000;35:862-880) recommended that simpler techniques be adopted and clinically evaluated.
Inclusion of mouth-to-mouth ventilation in the CPR protocol greatly increases the complexity of CPR performance. Mouth-to-mouth ventilation is unacceptable to many potential rescuers due to hygienic concerns or fear of disease transmission through intimate contact with the arrest victim. Fortunately, animal experiments and limited clinical data have indicated that ventilation is not required in the first minutes of a cardiac arrest. Aortic oxygen content falls little during the first 8-12 minutes of compression-only CPR. A limited amount of gas exchange is also supplied by chest compression and active gasping during CPR.
The data reported here support the recent Bethesda Conference recommendation that mouth-to-mouth ventilation be eliminated from lay instructions for basic life support. Although there was only a trend toward improved survival with the simpler method, it will be easier to teach and to remember and is more likely to be used in the community.
The major limitation of dropping a recommendation for ventilation during CPR is that victims of an arrest due to asphyxia probably should be ventilated. This would include drowning or foreign-body aspiration victims. Asphyxia is also a more common cause of arrest in children. Further efforts to refine algorithms to identify victims of asphyxia will be important.
Early defibrillation remains the key feature in the chain of survival during out-of-hospital cardiac arrest. Recently, President Clinton recommended greater availability of automatic external defibrillation in public settings. Hopefully, simplified CPR and earlier access to defibrillation will improve the rates of successful resuscitation.
Resuscitation research has been difficult to conduct in the United States due to concerns about informed consent. Obviously, the out-of-hospital cardiac arrest victims themselves cannot give consent at the time of study entry. Even if a family member were present, any time spent explaining a protocol might compromise the chance for survival. However, as illustrated by this paper, good clinical trials on resuscitation are important if clinical progress in the field is to move forward. Further efforts by the NIH, medical ethicists, and clinicians to foster investigation in the field are needed.
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