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CPR - The Why

Cardiopulmonary resuscitation (CPR) is a life-saving emergency procedure performed to maintain circulation and oxygenation in individuals experiencing cardiac arrest. The pathophysiology behind CPR involves understanding the events that occur during cardiac arrest and the mechanisms by which CPR aims to restore normal function.

During cardiac arrest, the heart suddenly stops pumping blood effectively, leading to a lack of oxygen and nutrients being delivered to vital organs, including the brain. The primary causes of cardiac arrest can include heart rhythm disturbances, such as ventricular fibrillation or ventricular tachycardia, as well as other conditions like myocardial infarction (heart attack), respiratory failure, drowning, or severe trauma.

In the initial minutes following cardiac arrest, the body can still contain sufficient oxygen reserves in the blood and tissues. However, without effective circulation, these reserves become depleted, and cells begin to undergo cellular hypoxia, leading to a cascade of detrimental effects.

During CPR, the aim is to manually and temporarily sustain circulation until more definitive interventions can be applied. CPR primarily focuses on two key components: chest compressions and artificial ventilation.

Chest compressions: The chest compressions involve applying force to the sternum (breastbone) in a rhythmic manner, which in turn compresses the heart between the sternum and the spine. The compressions create pressure that can generate blood flow, even in the absence of a coordinated heartbeat. By externally compressing the heart, blood is forced out of the heart chambers and circulated to vital organs, including the brain. The compression and relaxation cycles aim to mimic the natural contraction and relaxation of the heart during normal cardiac function.

Artificial ventilation: In addition to chest compressions, artificial ventilation is provided to deliver oxygen to the lungs and remove carbon dioxide. This involves opening the airway and providing breaths by either mouth-to-mouth resuscitation or using a bag-mask device or a mechanical ventilator. The oxygenated air helps replenish the oxygen supply in the lungs, which can be then transported to the rest of the body through chest compressions.

The combination of chest compressions and artificial ventilation in CPR helps to achieve two important goals. Firstly, chest compressions generate blood flow, which maintains oxygen delivery to vital organs. Secondly, artificial ventilation ensures the oxygenation of blood and the removal of waste gases, such as carbon dioxide, from the body.

However, it is important to note that CPR alone is not a definitive treatment for cardiac arrest. It serves as a temporary measure to sustain circulation until advanced medical interventions, such as defibrillation, can be provided. Defibrillation involves delivering an electrical shock to the heart to restore its normal rhythm. Early defibrillation, along with effective CPR, significantly increases the chances of survival in individuals experiencing cardiac arrest.

Overall, the pathophysiology behind CPR involves the restoration of circulation and oxygenation to vital organs through chest compressions and artificial ventilation. By providing temporary life support, CPR buys time for advanced medical interventions and helps improve the chances of successful resuscitation.

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