Cardiopulmonary Resuscitation, or CPR, is an emergency procedure performed when someone’s heart has stopped beating effectively. This life-saving technique provides artificial circulation and breathing until professional medical help can take over. CPR aims to maintain a minimal level of blood flow to the body’s most sensitive organs.
How a Healthy Heart Pumps Blood
A healthy heart functions as a powerful, efficient pump, circulating oxygenated blood throughout the body. The amount of blood the heart pumps in one minute is known as cardiac output. This measurement is determined by multiplying the heart rate, or the number of beats per minute, by the stroke volume, which is the amount of blood ejected with each beat.
For a healthy adult at rest, the heart typically beats between 60 to 100 times per minute. The heart’s stroke volume can vary, but it generally pushes out around 70 milliliters of blood with each beat. This results in a resting cardiac output of approximately 5 to 6 liters of blood per minute. This continuous circulation ensures that all tissues and organs receive the oxygen and nutrients necessary for their proper function.
How Chest Compressions Circulate Blood
During CPR, chest compressions artificially circulate blood throughout the body. When a rescuer presses down on the center of the chest, it creates pressure within the chest cavity. This pressure squeezes the heart between the sternum (breastbone) and the spine, directly propelling blood forward into the arteries.
Another mechanism is the “thoracic pump” theory, where changes in overall intrathoracic pressure during compressions and decompressions also contribute to blood movement. As the chest recoils after a compression, the pressure decreases, allowing the heart to refill with blood. This manual action mimics the heart’s natural pumping to provide some circulation.
Blood Flow During CPR Versus a Normal Heartbeat
The blood flow achieved through effective chest compressions during CPR is significantly less than that of a healthy, beating heart. While a normal heart can pump 5 to 6 liters of blood per minute at rest, CPR typically generates only a fraction of this amount. Effective chest compressions usually produce about 25% to 30% of normal cardiac output.
Despite this reduced flow, the artificial circulation provided by CPR is designed to deliver just enough oxygenated blood to the brain and other organs. This minimal circulation helps maintain cellular life and prevent rapid damage.
Why Every Compression is Vital
Even with the limited blood flow generated, every compression during CPR is important. The primary goal of these compressions is to sustain minimal perfusion to the brain and heart muscle. Without this artificial circulation, brain cells can begin to die within minutes due to a lack of oxygen.
Maintaining even a fraction of normal blood flow helps preserve brain function and the viability of the heart muscle. This buys time until advanced medical interventions, such as defibrillation or medication, can restore the heart’s natural rhythm. Therefore, consistent and high-quality chest compressions are important for improving the chances of survival and reducing long-term disability following cardiac arrest.