Cardiopulmonary resuscitation (CPR) is an emergency intervention used during cardiac arrest, when the heart is no longer producing effective circulation. It consists of repeated chest compressions, usually combined with assisted ventilation, to maintain some blood flow and oxygen delivery until circulation can be restored. CPR is a central component of basic life support, alongside recognition of cardiac arrest, activation of emergency services, and use of an automated external defibrillator (AED). (cpr.heart.org)
Physiological basis
During cardiac arrest, inadequate blood flow deprives organs of oxygen. Chest compressions generate pressure that moves blood through the circulation; release of that pressure allows the chest to recoil and supports blood returning to the heart. Compression depth, rate, recoil, and interruptions therefore affect the circulation produced by CPR. This circulation is only a temporary substitute for effective cardiac function. (cpr.heart.org)
Ventilation moves air into the lungs, allowing oxygen uptake and removal of carbon dioxide. Its importance varies with the cause of arrest: oxygen depletion is particularly significant in arrests preceded by respiratory failure or asphyxia. In infants and children, asphyxial arrest is more common than arrest from a primary cardiac event, making ventilation an especially important part of resuscitation. (cpr.heart.org)
CPR and defibrillation have different functions. CPR supports circulation; defibrillation delivers an electrical shock to terminate certain abnormal heart rhythms. Ventricular fibrillation and pulseless ventricular tachycardia are shockable rhythms, whereas asystole and pulseless electrical activity are not. An AED analyzes the rhythm and determines whether a shock is indicated. (cpr.heart.org)
Recognition and forms of CPR
Clinical and community protocols identify suspected cardiac arrest through unresponsiveness and absent or abnormal breathing. Agonal gasps—irregular gasping movements—can occur during arrest and do not constitute normal breathing. Lay-rescuer protocols do not depend on a pulse check, because pulse assessment can be unreliable and delay recognition. (cpr.heart.org)
Two principal forms are distinguished:
- Conventional CPR combines chest compressions with rescue breaths. Breaths may be delivered mouth-to-mouth, through a barrier device, or with ventilation equipment.
- Compression-only CPR, also called hands-only CPR, uses chest compressions without rescue breaths. It is incorporated into community responses to adult cardiac arrest, particularly when bystanders are untrained or unable to provide ventilation. (resus.org.uk)
Compression-only CPR is not a universal substitute for conventional CPR. Pediatric resuscitation and arrests involving substantial oxygen depletion place greater emphasis on ventilation. Newborn resuscitation at birth is addressed by separate neonatal protocols rather than ordinary infant CPR protocols. (cpr.heart.org)
Characteristics of high-quality CPR
Resuscitation guidelines describe high-quality CPR in terms of adequate compression depth and rate, complete chest recoil, minimal interruptions, and avoidance of excessive ventilation. The 2025 adult guidelines specify a compression rate of 100–120 per minute and a depth of approximately 5–6 cm. Conventional adult CPR before placement of an advanced airway commonly uses a compression-to-ventilation ratio of 30:2. These are standardized training and clinical parameters, rather than measures of normal cardiac output. (resus.org.uk)
Pediatric techniques account for body size and the greater importance of respiratory causes. Compression depth is approximately one-third of the chest’s front-to-back diameter. American Heart Association pediatric protocols distinguish single-rescuer CPR, generally using 30:2, from two-rescuer CPR, generally using 15:2 when no advanced airway is present. (cpr.heart.org)
Place within emergency care
CPR is one link in the chain of survival, an organizational model connecting recognition of arrest, emergency response, resuscitation, defibrillation, advanced treatment, and recovery. The response involves bystanders, emergency dispatchers, ambulance personnel, and hospital teams. Dispatcher-assisted CPR connects emergency-call recognition with instructions for the person at the scene. Public-access AED programs provide another connection between community action and professional care. (cpr.heart.org)
Advanced life support adds interventions such as rhythm assessment, advanced airway management, vascular access, and medications including epinephrine. It also addresses reversible causes of arrest. These measures supplement rather than replace the foundational roles of chest compressions and, when indicated, defibrillation. (cpr.heart.org)
Mechanical compression devices can deliver repeated compressions, but large randomized trials have not established a survival advantage over manual CPR in routine use. Extracorporeal CPR uses extracorporeal circulation in selected patients and requires specialized personnel, equipment, and systems of care. It is distinct from ordinary manual CPR. (cpr.heart.org)
Outcomes and limitations
A key immediate outcome is return of spontaneous circulation: restoration of circulation through the patient’s own cardiac function. This is not equivalent to survival to hospital discharge or recovery with preserved neurological function. Resuscitation research therefore evaluates these outcomes separately. (cpr.heart.org)
After circulation returns, patients may remain critically ill. Post-arrest care addresses oxygenation, ventilation, blood pressure, temperature, seizures, the cause of arrest, and complications. Injury to the brain from inadequate oxygen and blood flow is an important determinant of outcome. Neurological prognosis involves multiple assessments rather than a single finding. (cpr.heart.org)
Longer-term recovery may involve physical, cognitive, and emotional difficulties. Rehabilitation and follow-up are consequently part of the wider resuscitation pathway, not merely consequences separate from emergency treatment. Survival also depends on patient characteristics and the performance of the surrounding health system, so no single survival percentage describes all CPR situations. (cpr.heart.org)
Historical development
Modern CPR emerged from the combination of techniques developed separately. In the 1950s, James Elam and Peter Safar helped establish the effectiveness of expired-air and mouth-to-mouth ventilation. Research associated with William Kouwenhoven, James Jude, and Guy Knickerbocker established the practical role of closed-chest compressions. Around 1960, ventilation and external chest compressions were brought together into modern cardiopulmonary resuscitation. (cpr.heart.org)
Subsequent development included standardized training, practice manikins, organized emergency-care systems, and public instruction. Later changes emphasized early defibrillation, compression quality, and simplified community participation. CPR became both a clinical procedure and a coordinated public health activity. (cpr.heart.org)
Consent and treatment limitations
Decisions about CPR are addressed within medical ethics, advance care planning, and emergency-treatment policy. A do-not-resuscitate order, also termed a do-not-attempt-CPR order, records a limitation specifically concerning resuscitation. It does not by itself mean that all other treatment or comfort care is withheld. Documentation and implementation depend on the applicable clinical and legal framework. (cpr.heart.org)
References
- Adult basic life support Guidelinesresus.org.uk