Also posted over at Rogue Medic (now at EMS Blogs).
Continuing, after a 6 month delay, a discussion of an EMS 12 Lead article from Part I. ACLS (Advanced Cardiac Life Support) recommends charging the defibrillator during compressions. This is no less of a recommendation than giving epinephrine. How many people ignore ACLS guidelines for compressions during charging, but claim that it is evil to disobey anything ACLS recommends on epinephrine, amiodarone, or ventilations?
Analyses of VF waveform characteristics predictive of shock success have documented that the shorter the time interval between the last chest compression and shock delivery, the more likely the shock will be successful.141 A reduction of even a few seconds in the interval from pausing compressions to shock delivery can increase the probability of shock success.142 
Extra pauses in compressions add to the time without compressions.
If the medic/nurse/doctor using a manual defibrillator recognizes a shockable rhythm, why not provide compressions while charging the defibrillator?
Some people will say that this is dangerous.
But if someone accidentally delivers a shock during compressions, people will be killed!
In a systematic review, Hoke et al. summarized 29 reports of accidental deﬁbrillator discharges, of which only 15 occurred during resuscitation attempts.21 Symptoms included tingling sensations, discomfort, and minor burns, but no long term effects or major consequences were reported.
Where are the dead bodies we hear so much about?
Where are the medics/nurses/doctors needing to be defibrillated back to life?
There was only one incident where a shock was delivered while a rescuer was actively performing chest compressions. However, the compression transcript continued without any visible change to CPR administration, suggesting that the rescuer was unaffected by the event. Review of clinical records and audio transcripts revealed no evidence of inadvertent shocks to rescuers. In addition, there was no signiﬁcant difference in the incidence of inappropriate shocks to patients associated with charging during compressions (20.0% vs 20.1%; p = 0.97). 
In this study, there was one case of a shock being delivered during compressions, but nobody seems to have been affected by this shock.
What happened to the automatic death that ACLS instructors spend so much time describing?
Where is the evidence?
In the current study, charging during compressions decreased median pre-shock pause by over 10 s, which previous studies suggest could have a dramatic effect on clinical outcomes. We previously reported an almost two-fold increase in the chances of successful deﬁbrillation for every 5 s reduction in the pre-shock pause.9 Similarly, Eftestøl et al. found that a 10 s hands-off period prior to deﬁbrillation would roughly halve the probability of obtaining ROSC.6 
The risk to rescuers appears to be minimal, but the possible benefit to patients may be dramatic.
The difference in time without compressions is significant.
Interestingly, we found that the most efﬁcient technique with regard to minimizing pauses was not the AHA recommended method of pausing to analyze, resuming CPR to charge, and then pausing again to deﬁbrillate. Rather, charging at the end of every 2 min CPR cycle in anticipation of a shockable rhythm and then pausing only once, brieﬂy, to both analyze and either shock or disarm was associated with signiﬁcantly shorter total pause duration in the 30 s preceding deﬁbrillation. 
If we see asystole, we do not deliver a shock. We cancel the shock.
If we see PEA (Pulseless Electrical Activity, such as sinus rhythm, sinus tachycardia, sinus bradycardia, or any other non-shockable rhythm), we do not deliver a shock. We cancel the shock.
Cancelling the shock is not going to be the same for each defibrillator, but we do need to know how to cancel the shock for each machine we use. We can read the instructions.
We can turn on the monitor, charge it up to the setting we would use to defibrillate, and try to figure out ways to get the charged defibrillator to turn the shock off. We should already know how to do this.
All that appears to be required is competence. Why is that so difficult?
Why do we keep making excuses for misbehavior?
 CPR Before Defibrillation
2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science
Part 8: Adult Advanced Cardiovascular Life Support
Rhythm-Based Management of Cardiac Arrest
Free Full Text from Circulation with links to Free Full Text PDF
 Safety and efficacy of defibrillator charging during ongoing chest compressions: a multi-center study.
Edelson DP, Robertson-Dick BJ, Yuen TC, Eilevstjønn J, Walsh D, Bareis CJ, Vanden Hoek TL, Abella BS.
Resuscitation. 2010 Nov;81(11):1521-6.
PMID: 20807672 [PubMed - indexed for MEDLINE]