Why do chest compressions work?

Anyone who’s in ACLS knows the stats (at least the ones needed to pass the test): a ratio of 30:2 compressions to breaths in adults, forceful enough for 2 inches of chest wall depth, and at least a rate of 100 compressions/minute. But why do we do chest compressions? What is so important about these specific numbers?

Consider the goals of ACLS: to resuscitate a patient in cardiac arrest or a lethal arrhythmia.

The basic physiology behind chest compressions has one purpose: to increase blood flow to the heart by increasing coronary perfusion pressure (CPP).Chest compressions literally squeeze the heart, creating pressure that increases blood flow in the coronary arteries.

It’s important to generate a lot of CPP. In fact, some studies show that patients without a CPP >15 mmHg have NO chance of survival. 30:2, 2 inches, and >100 are not entirely arbitrary numbers. They are designed to give us hard-and-fast rules that will most likely generate the necessary CPP.

Factors that increase CPP:
-chest compressions
-medications like epinephrine and lidocaine

Factors that decrease CPP:
-hyperventilation or airway expansion (such as intubating a patient, which is why some patients may become hypotensive/unstable during intubation)

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