Cardiopulmonary Resuscitation (CPR) combines chest compressions and rescue breathing to maintain circulation when a person’s heart has stopped. The effectiveness of this life-saving measure relies heavily on performing compressions correctly, making accurate hand placement the most important factor. Correctly locating the target area ensures the manual force translates into sufficient blood flow while minimizing the potential for injury. The sternum, or breastbone, is the specific target for compressions.
Anatomy and Purpose of Sternum Compression
The sternum, or breastbone, is a flat bone situated in the center of the chest that connects the ribs via cartilage. It is composed of the manubrium at the top, the body in the middle, and the cartilaginous xiphoid process at the bottom. The heart lies directly beneath the sternum, positioned slightly to the left of the midline.
Compressing the sternum squeezes the heart between the breastbone and the spine. This action generates pressure that forces blood out of the heart’s chambers and into the major blood vessels, initiating artificial circulation. This manual pump delivers oxygen-rich blood, particularly to the brain, delaying tissue death until professional medical care can restore a natural heartbeat.
Applying pressure over the wrong area reduces the force transmitted to the heart and increases the risk of internal injury. Compressing too low, over the xiphoid process, can cause this cartilage to break off and potentially puncture underlying organs such as the liver. Placing hands too high toward the neck or clavicles fails to engage the heart effectively, rendering compressions ineffective.
Locating the Precise Compression Spot
The correct compression spot for an adult is the center of the chest, specifically over the lower half of the breastbone. This location maximizes the mechanical advantage on the heart while leveraging the strongest section of the sternum. Rescuers should aim for the midpoint of the sternum, avoiding the top and the bottom of the bone.
One common method for finding this area is to use the patient’s anatomical landmarks. The target area is roughly aligned with a line drawn between the patient’s nipples. Placing the heel of one hand directly on the sternum, just below this line, centers the pressure over the heart’s location.
Focus the pressure on the center of the chest—the sternum—and not on the ribs to the side. The heel of the hand should be placed along the midline of the body to ensure the force is directed straight down onto the breastbone. This central placement results in accurate hand position for both trained and untrained responders.
Hand Placement and Compression Technique
Once the location on the sternum is identified, establish the correct hand positioning for effective force delivery. Place the heel of one hand directly on the compression spot, with the heel of the second hand placed on top of the first. The fingers of the upper hand should be interlaced with the lower hand, or held up off the chest wall.
This stacked hand position ensures the force is concentrated through the heel of the bottom hand, preventing pressure on the patient’s ribs. Proper body alignment involves the rescuer kneeling beside the patient and positioning their shoulders directly over their hands, with elbows locked straight. This posture allows the rescuer to use their body weight to deliver the necessary force, rather than relying on arm strength.
Compressions must be delivered at a rate of 100 to 120 per minute. For adults, the downward compression depth should be at least 2 inches, but not exceed 2.4 inches (5 to 6 centimeters). Allowing the chest to fully recoil to its normal position after each compression is also important, as this permits the heart to refill with blood.
Positional Adjustments for Infants
Performing CPR on an infant (a child under one year of age) requires modifications to both position and technique. The infant’s smaller, flexible anatomy necessitates a gentler approach to prevent injury while still achieving the required depth. The correct target area remains the center of the chest, on the breastbone.
To locate the spot on an infant, rescuers should visualize a line connecting the infant’s nipples. Compressions are performed on the breastbone just below this line. The most common technique involves using two fingers—the index and middle fingers—placed on the center of the sternum.
Alternatively, some protocols allow for the two-thumb encircling technique, where the thumbs are placed side-by-side on the sternum while the hands wrap around the chest for support. The compression depth for an infant is approximately 1.5 inches (about 4 centimeters), corresponding to about one-third the depth of the chest. The compression rate remains the same as for adults, between 100 and 120 per minute.