Cardiopulmonary resuscitation (CPR) is an emergency medical procedure for a victim of cardiac arrest (that is, the heart has stopped) and respiratory arrest. CPR consists of artificial blood circulation and artificial respiration, for example, chest compressions and lung ventilation. (A person who is in respiratory arrest has a pulse but is not breathing; therefore, artificial respiration is appropriate. If it is difficult to detect a pulse, CPR may be used in both cases.)
CPR is generally continued, usually in the presence of advanced life support, until the patient regains a heartbeat or is declared dead. (In the absence of advanced life support, basic life support can be provided, using the principles of airway, breathing, and circulation, or the ABCs.) CPR is unlikely to restart the heart, but it is used to maintain a flow of oxygenated blood to the brain and heart, preventing tissue death. Defibrillation and advanced life support are usually needed to restart the heart.
Defibrillation is the treatment for life-threatening cardiac arrhythmias of ventricular fibrillation, and it consists of delivering a therapeutic dose of electrical energy to the heart with an external device called an automated external defibrillator (AED). This device allows normal rhythm to be re-established. Divers can use the unit successfully with little to no training.
The brain may sustain damage after blood flow has ceased for about 4 minutes and irreversible damage after about 7 minutes. If blood flow ceases for 1 to 2 hours, the brain cells will start to die. The heart loses the ability to maintain a normal rhythm. Low body temperatures, as sometimes seen in drowning, prolong the time the brain survives. CPR is likely to be only effective if commenced within 6 minutes after the blood flow stops.
Studies have shown the importance of immediate CPR followed by defibrillation within 3 to 5 minutes. The survival rate is about 30%, but without these two actions, the survival rate is only about 2%.
Here are a few key points about CPR.
- The patient with a bystander performing CPR can have a survival rate of 4 to 5% until emergency medical service (EMS) arrive.
- CPR does result in a few complete recoveries but is less effective without defibrillation.
- CPR does not revive the patient but preserves the body for defibrillation and advanced life support.
Hypothermia seems to protect the victim by slowing down metabolic and physiologic processes, greatly decreasing oxygen requirements of tissues. There are cases in which CPR, defibrillation, and advanced warming techniques have revived victims after substantial periods of hypothermia.
CPR training is essential for divers by a recognized training authority. Further training in first aid, CPR, and AED is highly recommended. See your diver center to find out more. Remember, CPR cannot be performed in the water, and there must be a stable base or platform available.