How far below the nipple line should chest compressions be performed on an infant?

Chest compressions on an infant should be performed just below the nipple line to ensure effective compressions that can create adequate blood flow during cardiopulmonary resuscitation (CPR). This placement allows for optimal compression of the heart, which is located centrally in the chest cavity.

Positioning the hands just below the nipple line also helps in achieving the correct depth of compression, which is crucial since infants have relatively small chests compared to adults. The appropriate technique involves using two fingers for compressions, allowing for focused pressure on the heart without the risk of injury to the underlying organs.

Other options do not provide the correct anatomical location for effective compressions. For instance, compressions performed above the shoulder line or at the sternum's base would not effectively target the heart, leading to inadequate resuscitation efforts.