Cardiopulmonary resuscitation

Cardiopulmonary resuscitation, commonly known as CPR, is an emergency procedure used during cardiac or respiratory arrest. This occurs when a person's heart stops pumping or they stop breathing. The primary goal of CPR is not to restart the heart, but to maintain circulation. By performing chest compressions, a rescuer can keep oxygenated blood flowing to the brain and heart. This process helps delay tissue death and extends the window of opportunity for professional medical help to arrive.

The mechanism of CPR relies on creating a pressure gradient within the body. When a rescuer pushes on the sternum, which is the bone in the middle of the chest, they are manually pumping the heart. This action generates pressure that moves blood between the arterial and venous vascular beds. To be effective, the rescuer must push deep enough to compress the heart and then allow the chest to fully relax. This relaxation allows the heart to refill with blood before the next compression.

There are different methods of CPR depending on the victim's age and the situation. For adults, the standard approach involves a ratio of 30 chest compressions to 2 rescue breaths. Rescuers use two hands to push to a depth of approximately 5 cm, or 2 inches. For children, one hand may be sufficient, and the compression-to-breathing ratio changes to 15:2 if two trained rescuers are present. Infants require a different technique entirely, using only two fingers to compress the chest to a depth of 4 cm.

History shows that the way we perform CPR has evolved to improve survival. In 2010, the American Heart Association (AHA) and the International Liaison Committee on Resuscitation updated their guidelines. They changed the recommended sequence from ABC (airway, breathing, compressions) to CAB (compressions, airway, breathing). This shift emphasizes that high-quality chest compressions are the most critical part of the process. Modern guidelines also suggest that untrained rescuers can perform "hands-only" CPR, which involves only chest compressions without rescue breaths.

Timing is a critical factor in the success of CPR. The brain can sustain damage after blood flow has stopped for about four minutes. Irreversible damage can occur after approximately seven minutes. If blood flow ceases for one to two hours, body cells will die. Therefore, CPR is most effective when performed within seven minutes of the stoppage of blood flow.

In many cases, CPR is used alongside an automated external defibrillator, or AED. An AED is a portable machine that analyzes a person's heart rhythm. It can deliver an electric shock, a process called defibrillation, to help the heart restore a viable rhythm. This is specifically effective for certain rhythms like ventricular fibrillation or pulseless ventricular tachycardia. However, defibrillation is not effective for rhythms like asystole, which usually requires treating the underlying medical condition.

When responding to an emergency, there is a specific order of operations to follow. A rescuer should first ask bystanders for help and call emergency medical services. If an AED is available nearby, it should be retrieved and used as soon as possible. If a rescuer is alone with a drowning victim or a child, they should perform two minutes of CPR before leaving to call for help. This is because respiratory issues, rather than cardiac ones, are often the cause of arrest in these groups.

CPR connects to many different fields of medical science, including physiology and emergency medicine. It demonstrates how physical pressure can mimic biological functions to sustain life. By understanding the relationship between oxygenation, blood flow, and brain function, medical professionals can better treat patients. CPR remains a vital tool in the chain of survival, bridging the gap between a sudden arrest and professional clinical intervention.