The routine of cardiac resuscitation is now so standard that few people realize how recent it is. The basic principle of closed cardiac massage was first properly described in modern times in 1960. (It had been described in the nineteenth century but was not commonly practiced.) Prior to that time, a cardiac arrest was almost certainly fatal. The only treatment was thought to be open massage, in which the surgeon incised the chest and squeezed the heart directly with his fingers. Although frequently successful, open massage rarely produced long-term benefit; one study in 1951 indicated that of patients who underwent open massage, only 1 per cent survived to be discharged from the hospital. That figure still stands; open massage is now a last-ditch effort only.

Closed cardiac massage depends upon the anatomical fact that the heart is tightly packed in the chest between breastbone and backbone. Rhythmic pressure upon the breastbone will squeeze the heart enough to produce a pulse. Direct open massage is therefore not necessary, and the hazards of this surgery are avoided.

The purpose of cardiac massage is to maintain blood circulation which, in conjunction with artificial respiration, provides blood oxygenation for the brain. The brain is the organ most sensitive to lack of oxygen; under most circumstances brain damage will begin after three minutes of circulatory arrest. In contrast, the heart itself is much more durable and can resume beating after ten or more minutes. But by this time, unless resuscitation has already been begun, the brain will be irreversibly damaged.

In some situations, mere compression of the heart is enough to start it beating again, but the massage is generally accompanied by a variety of other maneuvers to correct metabolic changes from the arrest. This includes the injection of Adrenalin, calcium, and sodium bicarbonate. The experience of the last decade, utilizing these techniques, has demonstrated that cardiac arrest is reversible to an astonishing extent.