The Chain of Survival is a five-step process for providing treatment to victims of sudden cardiac arrest (SCA). It was first developed by the American Heart Association (AHA) in 1990 after several decades of research into SCA and was designed in recognition of the fact that most episodes of SCA occur outside of a hospital, with death occurring within minutes of onset without treatment. Quick execution of each and every link is critical because the chances of survival decrease 7 to 10% with each passing minute.
Emergency systems that can effectively implement these links can achieve ventricular fibrillation cardiac arrest survival of almost 50%. Indeed, a recent study of school-based AED programs found that the overall survival rate can be increased to over 70% and to nearly 90% among student-athletes resuscitated with an on-site AED.
More people can survive SCA if the following steps occur in rapid succession:
- Cardiac arrest is immediately recognized and the emergency response system is activated;
- Early cardiopulmonary resuscitation (CPR) is started with an emphasis on chest compression;
- Rapid defibrillation occurs;
- Effective advanced life support is begun; and
- Integrated post-cardiac arrest care is provided.
The AHA developed the Chain of Survival concept to communicate this sequence in a useful and easy-to-understand way.
Five links in chain of survival:
1. Immediate recognition that the victim has experienced a cardiac arrest, based on unresponsiveness and lack of normal breathing, immediate activation of the emergency response system (e.g. call 911), and get an AED/defibrillator.
- Immediate call crucial. The sooner 911 or your local emergency number is called the sooner early advanced life support arrives. A delay of just a few minutes could prove fatal.
- Sets Chain of Survival in motion. Calling 911 gives the next two links, CPR and Early Defibrillation, the greatest opportunity for success.
2. Early CPR. Once an SCA victim collapses and a bystander calls 911, the next step in the Chain is to immediately begin chest compressions (Cardiopulmonary Resuscitation or CPR). The AHA now recommends that all rescuers, regardless of training, or skill level, victim charactheristics, or available resources, should provide chest compressions to all cardiac arrest victims, with rescuers who are able adding ventilations (mouth-to-mouth) to chest compressions. Rescuers should start CPR immediately. The directive to "look, listen, and feel for breathing" is no longer recommended.
- Focus should be on delivering high-quality CPR:
- providing chest compressions of adequate rate (at least 100/minute)
- providing chest compressions of adequate depth
- adults: a compression depth of at least 2 inches
- infants and children: a depth of at least 1 1/2 inches in infants and about 2 inches in children
- allowing complete chest recoil after each compression
- minimizing interruptions in compression
- avoiding excessive ventilation
- Hands-Only (compression only) CPR for untrained rescuer.
- Buys time: During SCA, the heart twitches irregularly, most often due to ventricular fibrillation (VF), and cannot pump oxygenated blood efficiently to the brain, lungs, and other organs. The victim quickly stops breathing and loses consciousness. Prompt CPR can help sustain life during VF. Chest compressions help oxygenated blood flow to the person's brain and heart until an AED can be used to attempt to restore normal heart pumping or advanced medical personnel arrive.
- Ineffective by itself:
Only when combined with early defibrillation and early advanced care
can CPR significantly increase an SCA victim's chance for long-term
- CPR alone cannot fully resuscitate a person in SCA because it does nothing to restore normal heart rhythm
- While better than no treatment, the survival rate for victims in SCA treated by CPR alone is very small (between 2 to 5%);
- The longer CPR is performed, the less the chance of survival.
Strength of link depends on increased training. Lay people initiate CPR in more than half of SCA cases in which someone has witnessed the incident. The strength of this link is dependent on the number of lay people trained in CPR and the number of training programs in your schools and community.