Chest compressions are a manual, life-saving technique designed to address cardiac arrest, a state where the heart has stopped circulating blood effectively. This intervention forces blood from the chest cavity to the brain and other vital organs, artificially maintaining circulation until a normal heart rhythm can be restored. Cardiopulmonary resuscitation (CPR) is intended for a patient who is unresponsive and whose heart is no longer functioning. Applying this forceful, rhythmic pressure to a person whose heart is already beating introduces significant risk and is contrary to its intended purpose.
Assessing the Need for Compressions
The decision to begin chest compressions rests on a rapid assessment of the patient’s condition. Compressions should only be initiated if the individual is unresponsive, not breathing normally, and lacks a pulse. Checking for responsiveness involves gently tapping the person and shouting to see if they react.
The next step involves quickly checking for normal breathing and a pulse simultaneously. Rescuers should look for chest rise and listen for breaths, recognizing that gasping or agonal breaths are not considered normal breathing. The rescuer must also check for a pulse, typically by feeling the carotid artery in the neck for at least five seconds but no more than ten seconds.
If a pulse is present, even if the person is breathing abnormally, compressions must be withheld. In this scenario, the heart is still generating effective pressure, and the patient may only require rescue breathing. The ten-second limit on the pulse check prevents delay for those who need CPR, but it also reinforces the requirement to confirm cardiac arrest before proceeding. Beginning compressions without this confirmation places the patient at significant risk of injury.
Mechanical Injuries from Unnecessary Compressions
When chest compressions are applied to a person with a beating heart, the force encounters a chest cavity with normal muscle tone and internal pressure, leading to structural damage. The high-force, high-rate pushes—recommended at a depth of 5 to 6 centimeters (about 2 to 2.4 inches)—are designed for a body with reduced rigidity. This force, when applied incorrectly, frequently results in fractured ribs, which occur in 30% to 60% of adult patients even when compressions are performed correctly during cardiac arrest.
Fractures of the sternum, the long flat bone in the center of the chest, are also common mechanical injuries. The force required to compress the chest deep enough to circulate blood can cause the sternum to break or separate from the ribs. These skeletal injuries increase the risk of severe complications, such as a pneumothorax, which is a collapsed lung caused by a broken rib piercing the lung tissue.
The downward force of compressions can be transmitted to the organs situated beneath the rib cage. The liver and spleen, located in the upper abdomen, are at risk of laceration or contusion from the mechanical trauma. In an individual who is not in cardiac arrest, the force required for compressions can cause these organs to bleed internally, resulting in a life-threatening internal hemorrhage.
Disrupting Normal Heart Rhythm
The most serious consequence of performing chest compressions on a beating heart involves direct interference with the heart’s electrical and mechanical function. The heart maintains its precise rhythm, known as sinus rhythm, through a coordinated electrical cycle that dictates contraction and relaxation. Applying an external mechanical shock to the chest at a rate of 100 to 120 times per minute can disrupt this natural cycle.
This external mechanical pressure can introduce instability to the heart’s electrical system, potentially inducing life-threatening arrhythmias. The mechanical force can trigger ventricular fibrillation (V-Fib) or ventricular tachycardia (V-Tach), turning a stable heart into a chaotic, quivering organ that cannot pump blood. This condition, known as iatrogenic cardiac arrest, is medically induced and creates the situation CPR is meant to address.
Hemodynamically, a beating heart is optimized to fill with blood and pump it out efficiently. External compressions interrupt this natural process, severely reducing the heart’s perfusion. The compressions can impede the coronary perfusion pressure, which is the pressure gradient necessary to supply the heart muscle with oxygenated blood. By interfering with the heart’s filling phase, unnecessary compressions can lead to a drop in blood pressure and reduced blood flow to the brain, causing more harm than the underlying issue.