ACLS: Continuous chest compressions versus standard 30:2 CPR

This is a new study, hot off the press, from the resuscitation outcomes consortium. Usually I save up new papers and talk about them all in the articles of the month. However, I have been on a bit of an ACLS kick this month, starting with a summary on the new 2015 ILCOR guidelines and then an update of my approach to neonatal resuscitation to reflect these new guidelines. So when I saw this new cardiac arrest study looking at continuous chest compressions, it seemed worthy of its own post.

The paper

Nichol G, Leroux B, Wang H. Trial of Continuous or Interrupted Chest Compressions during CPR. The New England journal of medicine. 2015. PMID: 26550795 [free full text]

The question

For adult patients with out of hospital cardiac arrest, do continuous chest compressions result in better survival to hospital discharge than the traditional 30:2 ratio of compressions to ventilations?

The bottom line

Yes, everyone is busy, so let’s get the bottom line in here right at the beginning.

No difference. Survival was the same whether patients received continuous or 30:2 chest compressions.

Study Details

Population		Adult patients with non-traumatic out of hospital cardiac arrest
Intervention		Continuous chest compressions at a rate of 100/min with asynchronous ventilations at 10/min
Comparison		Chest compressions with interruptions for ventilations at a ratio of 30 compressions to 2 ventilations
Outcome		Primary outcome: rate of survival to hospital discharge

Results

A total of 23,711 patients were included in the active enrollment stage of the study, 12,653 in the intervention group and 11,058 in the control group

Survival to hospital discharge:

• 9.0% continuous chest compressions
• 9.7% interrupted (30:2)

Neurologically intact survival (Modified Rankin ≤ 3):

• 7.0% continuous chest compressions
• 7.7% interrupted (30:2)

Discussion

Quality of compressions may be different in this study than in real life. Any study can suffer from the Hawthorne effect, but this study group is especially picky about their compressions. They used a run-in period to sort out which EMS agencies were capable of sticking to their definition of good CPR. I also know some ROC investigators, and the quality of CPR was constantly monitored. Individual paramedics received rapid feedback if their performance wasn’t up to par. This might explain why the chest compression fraction was so similar between the two groups (0.83 in the continuous chest compression group and 0.77 in the interrupted group). It’s not surprising the outcomes were similar when the chest compression fraction really wasn’t changed by the intervention.

There are a few exclusion criteria it might make sense to know:

• EMS-witnessed arrest
• A written advance directive to not resuscitate
• Traumatic injury
• Asphyxial cause of arrest
• Uncontrolled bleeding or exsanguination
• Known pregnancy
• Preexisting tracheostomy
• Prisoners
• Initial CPR performed by a nonparticipating EMS provider
• Treated with a mechanical chest-compression device before manual CPR by ROC EMS personnel
• Advanced airway management before ROC EMS agency arrival

Of these, “asphyxial cause of arrest” jumped out at me as being important. Looking at figure 1 in the study, of the 35,904 patients screened for enrollment, 1169 (3.3%) were excluded for asphyxia or an obvious respiratory cause of their arrest. It makes sense that these patients may require a different interventions, with more of a focus on airway and breathing. However, this paper never describes these patients, so I am not sure how to apply this to the patient in front of me.

Also, these were all adult patients. We know pediatric patients are much more likely to have respiratory etiologies to their arrest, and therefore may require a respiratory focus to their resuscitation.

Conclusion

In hospital, I don’t think this is going to change things a great deal. Most ED practitioners are placing some sort of advanced airway, such as an LMA or an endotracheal tube, and therefore are already providing asynchronous ventilations (trying to remember to slow down and stick to 10 breaths a minute.) Based on this data, I think it is reasonable to continue to use a bag valve mask in the emergency department with continuous chest compressions if other priorities preclude the placement of an advanced airway. It will be interesting to see how this shapes EMS practice in the future. I always hated having to count to 30, especially when the adrenaline interfered and I made embarrassing mistakes. Continuous chest compressions make sense to me.