CPR First? Or Defibrillation First?

Ventricular Fibrillation is considered the most favorable cardiac arrest rhythm, and if treated promptly can result in ROSC with a favorable neurological outcome. Most survival rates are reported using witnessed arrest with a shockable rhythm as opposed to asystole or PEA, as the outcomes of these rhythms are comparatively very poor.

The Resuscitation Academy mantra “everyone in VF survives” has been adopted by many EMS systems around the world to emphasize that these patients can and do survive, and it’s up to us to save them.

Major advances have been made over the past 10 years but CPR and defibrillation are still the bedrock of resuscitation science. The attributes of high-quality CPR were re-affirmed in the 2015 AHA ECC Guidelines.

  • Ensuring adequate rate (100-120)

  • Ensuring adequate depth (2 to 2.4” or 5 to 6 cm)

  • Allowing full chest recoil (avoid leaning)

  • Minimizing interruptions to chest compressions

  • Avoiding excessive ventilations

Is CPR Before Defibrillation Dogmatic?

In the context of a witnessed arrest by a trained first responder or bystander who has an AED or manual defibrillator, the importance of early defibrillation is irrefutable. We have been told repeatedly that early defibrillation saves lives.

I initially began my research under the assumption that providing 1.5 to 3 minutes of CPR before defibrillation provides oxygen and nutrients to the heart therefore making defibrillation more likely to be successful. However, recent evidence suggests that performing chest compressions while setting up the defibrillator and charging the capacitor may be adequate.

A “CPR first” approach is rooted in evidence suggesting the existence of 3 time-sensitive phases of VF arrest.

  1. Electrical phase (0-4 minutes)

  2. Circulatory phase (5-10 minutes)

  3. Metabolic Phase (> 10 minutes)

Researchers suggested that a period of CPR prior to defibrillation might confer a benefit during the so-called “circulatory phase” of the cardiac arrest.

Evolution of American Heart Association Recommendations

Because it is rare for EMS to arrive on scene during the electrical phase, the 2005 AHA ECC Guidelines made this recommendation:

When an out-of-hospital cardiac arrest is not witnessed by EMS personnel, they may give about 5 cycles of CPR before checking the ECG rhythm and attempting defibrillation (Class IIb). One cycle of CPR consists of 30 compressions and 2 breaths. When compressions are delivered at a rate of about 100 per minute, 5 cycles of CPR should take roughly 2 minutes (range: about 1½ to 3 minutes). This recommendation regarding CPR prior to attempted defibrillation is supported by 2 clinical studies (LOE 2, LOE 3) of adult out-of-hospital VF SCA. In those studies when EMS call-to-arrival intervals were 4 to 5 minutes or longer, victims who received 1½ to 3 minutes of CPR before defibrillation showed an increased rate of initial resuscitation, survival to hospital discharge, and 1-year survival when compared with those who received immediate defibrillation for VF SCA. One randomized study, however, found no benefit to CPR before defibrillation for non-paramedic-witnessed SCA.

Fast forward 10 years to the 2015 Guidelines.