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In moments of cardiac emergencies, Cardiopulmonary Resuscitation (CPR) stands as a critical intervention. This technique is usually best performed by trained CPR givers (whom we like to call “Heartstrong Heroes”). They offer manual chest compressions to preserve brain function until further measures can be taken to restore spontaneous blood circulation and breathing in a person experiencing cardiac arrest.
During a cardiac crisis, every second counts. While the basic premise of CPR is widely understood, its underlying scientific principles, particularly in relation to cardiac physiology, are less commonly discussed.
In this blog, we aim to examine the mechanics of how CPR maintains blood flow, its critical role in ensuring that blood reaches not only the brain but also other vital organs, and the overall systemic response during its application.
Understanding these intricacies is not just academic – it forms the foundation for effective and informed CPR application, potentially improving its success rate in critical scenarios.
According to the British Heart Foundation (BHF), the human heart is a remarkable muscle. It serves as the engine of the circulatory system. It operates tirelessly, pumping blood throughout the body. Its primary role is to ensure that oxygen-rich blood reaches every cell and organ.
The heart achieves this through a rhythmic sequence of contractions and relaxations that propel blood into the vast network of arteries, veins, and capillaries.
The right side of the heart is responsible for pumping deoxygenated blood to the lungs for oxygenation, while the left side pumps oxygenated blood to the rest of the body.
Cardiac arrest (or heart stoppage) represents a dire emergency when there is a sudden halt to heart function. Unlike a heart attack, which is typically caused by a blockage that stops blood flow to the heart, cardiac arrest is often a result of an electrical disturbance that disrupts the heart’s rhythm.
This disruption leads to an immediate stoppage in the heart’s ability to pump blood, cutting off the vital supply of oxygen and nutrients to the organs, most critically to the brain.
The lack of oxygenated blood can cause loss of consciousness and stopping of breathing, making immediate intervention crucial. Without prompt and effective CPR, the chances of survival diminish rapidly.
According to the American Heart Association (AHA), the essence of CPR lies in its ability to simulate the heart’s pumping mechanism through chest compressions. When the heart stops beating during cardiac arrest, chest compressions become a manual substitute for the heart’s natural rhythm.
The primary goal is to maintain blood flow, particularly to the brain and other vital organs, until normal heart rhythm is restored.
This is achieved by rhythmically pressing down on the chest, which compresses the heart, forcing blood out into circulation.
The efficacy of chest compressions hinges on two key factors: depth and rhythm. Compressions need to be deep enough, typically about two inches in adults, to adequately compress the heart and create sufficient blood flow.
Equally important is the rhythm, usually recommended at a rate of 100 to 120 compressions per minute. This specific rate ensures that the heart is compressed and released at a frequency that maximizes blood flow while also allowing the heart to refill with blood between compressions.
This careful balance of depth and rhythm is crucial for the effectiveness of CPR in an emergency scenario.
According to Nisha Chibber Chandra, MD, writing in the Annals of Emergency Medicine, during cardiac arrest, the heart’s inability to pump blood causes a cessation in “systemic circulation,” i.e., the process by which blood travels from the heart to all parts of the body and back again. CPR plays a critical role here.
By performing chest compressions, CPR attempts to mimic the heart’s pumping action ¬ but it does this less effectively than the heart can. Nevertheless, this manual intervention helps maintain a minimal (yet vital) flow of blood to the body’s organs.
However, while CPR doesn’t fully replicate the normal cardiac output, even this reduced blood flow achieved through non-stop chest compressions can be life-saving, supplying essential oxygen and nutrients to organs, especially the brain and heart.
“Perfusion” is a medical term that refers to the passage of blood through the circulatory system to an organ or a tissue. It’s the process by which organs receive the blood (and hence oxygen and nutrients) they need to function.
In the event of cardiac arrest, perfusion is severely compromised. Therefore, CPR’s role in sustaining perfusion is vital. Effective chest compressions ensure that blood continues to flow to major organs (even if it is at a lower rate than before).
According to the American CPR Care Association, the brain is highly sensitive to oxygen deprivation. In the event of cardiac arrest, the absence of adequate circulation leads to an immediate drop in the oxygen supply to the brain, which can result in irreversible brain damage within minutes.
CPR plays a vital role in reducing this risk. By performing chest compressions, CPR practitioners help maintain a minimal but critical flow of blood to the brain. This flow carries oxygen, which is crucial for brain cells’ survival.
Although the oxygen delivered via CPR is less than what the brain would receive under normal circulatory conditions, it can be sufficient to prevent widespread brain cell death.
While chest compressions are primarily focused on maintaining blood flow, they also indirectly support lung function. During cardiac arrest, the lungs are no longer able to effectively exchange gases (oxygen and carbon dioxide) due to the cessation of normal breathing and blood flow.
Chest compressions help by creating a passive form of ventilation. Each compression slightly inflates the lungs, allowing some air exchange to occur. This helps in maintaining a reasonable level of gas exchange in the lungs, ensuring that the blood being circulated carries at least some minimal oxygen to the body’s tissues.
According to Jacob DeLaRosa, MD, writing in the Portneuf Heart and Vascular Institute website, the old adage that “prevention is better than cure” holds profound truth. People with chronic ailments such as obesity, cholesterol, diabetes, and hypertension – along with other hereditary factors – must understand that these can all have a multiplicative impact on the heart.
By controlling these chronic conditions through lifestyle changes, medication, and regular health check-ups, individuals can significantly reduce their risk of experiencing a cardiac emergency.
This approach of preventive healthcare, focusing on regular monitoring and lifestyle adjustments, serves as a crucial strategy in safeguarding heart health and preventing the need for emergency interventions like CPR.
In the final analysis, both factors are important: recognizing the power of prevention of heart emergencies and understanding the science behind effective CPR and its role in cardiac physiology.
Even as we stay responsible for our own health and encourage everyone around us to engage in proactive heart care, it is vital for all of us to equip ourselves with CPR training. We need to commit to the mantra: Be CPR-aware. Save lives. Be a Heartstrong Hero.
