How Properly Performed
Chest Compressions Work

There are two ways that chest compressions provide blood circulation.  First, by increasing the pressure inside the chest (intrathoracic) it forces blood out of the chest.  Second, the heart is compressed between the sternum and the spine.  Opening and closing of the heart valves keeps the blood (with oxygen) flowing forward to the brain and other vital organs.

Under the best of circumstances, CPR can provide up to 20% of the normal blood flow. The standards set in the AHA guidelines are aimed at achieving 20% circulation of blood throughout the body, including circulating through the brain. An error in performing any of the component skills which are part of performing compressions will reduce or even stop blood flow. The AHA guidelines specify how to perform chest compressions properly.

Both the heart and thorax respond to compression rate, compression depth, and chest recoil. In reduced depth and/or reduced rate compressions, the heart and thorax are not pumped sufficiently. Without proper recoil the thorax and heart cannot fill with blood, so the next compression will be less effective and if such ineffective compressions continue in succession it will lead to loss of aortic pressure.

For more how this works, click on the links to the right.