3-phase model of cardiopulmonary resuscitation (CPR)

3-phase model of cardiopulmonary resuscitation (CPR)

Three phase model of cardiopulmonary resuscitation (CPR) reflects the time-sensitive progression of resuscitation physiology. The phases are as follows [1]:

1. Electrical phase: from the time of cardiac arrest to approximately 4 minutes following the arrest
2. Circulatory phase: from approximately 4 to approximately 10 minutes after cardiac arrest
3. Metabolic phase: extending beyond approximately 10 minutes after cardiac arrest

Electrical phase

Early defibrillation is currently an ILCOR (and European Resuscitation Council and American Heart Association) class I recommendation in the electrical phase. This can occur when an implanted cardioverter defibrillator detects ventricular fibrillation and delivers a shock within 15 to 20 seconds and the response is nearing cent per cent. Next best is the situation in a monitored setting like an intensive care unit or in special circumstances like in-flight or airport where an automatic external defibrillator (AED) is used to deliver a shock soon after the onset of sudden cardiac arrest due to ventricular fibrillation. The early defibrillation in a public place with AED may get survival rates up to 50%.

Circulatory phase

In the circulatory phase from 4 to 10 minutes after the onset of cardiac arrest, the most important aspect is to initiate CPR to provide oxygen delivery to tissues, followed by defibrillation, which may be delayed by 1-3 minutes. One study showed that immediate defibrillation after five minutes of cardiac arrest resulted in 30% successful defibrillation and zero percent return of spontaneous circulation (ROSC), where as one minute CPR plus epinephrine before defibrillation resulted in 70% successful defibrillation and 40% ROSC. The concept is that defibrillation of a globally ischemic heart beyond four minutes may be harmful and the results are better with partial restoration of circulation by CPR.

Metabolic phase

Metabolic phase is beyond ten minutes from the onset of cardiac arrest. The effectiveness of both defibrillation and CPR followed by defibrillation are declining in this phase. During the metabolic phase, tissue injury from global ischemia can worsen with reperfusion. Initiation of apoptosis can occur with reperfusion of cardiomyocytes after prolonged ischemia. Cell death can be reduced by immediate induction of targeted temperature management after reperfusion.

Reference

1. Weisfeldt ML, Becker LB. Resuscitation after cardiac arrest: a 3-phase time-sensitive model. JAMA. 2002 Dec 18;288(23):3035-8.