Background

In cardiopulmonary resuscitation (CPR), chest compressions are frequently interrupted to provide rescue breathing. It has been documented in several pig models that these pauses are associated with a decrease in coronary perfusion pressure. Furthermore, it may take several minutes of chest compressions to restore perfusion pressures to adequate values. Other studies have found interruptions to be associated with decreased survival in animals with cardiac arrest. At this time, the 2015 AHA guidelines emphasize high quality chest compressions while minimizing interruptions, but continue to recommend pausing for rescue breaths.

Clinical Question

Do continuous chest compressions, as compared with chest compressions interrupted for ventilation, during CPR performed by emergency medical service (EMS) providers effect the rate of survival, neurologic function or rate of adverse events?

Population

Adult patients with out-of-hospital, atraumatic cardiac arrest (OHCA)

Intervention

Continuous chest compressions (at rate of 100/minute) with asynchronous ventilation (at 10 breaths/minute)

Control

Chest compressions with interruptions for ventilation at ratio of 30 compressions to 2 rescue breaths

Outcomes

Primary: Rate of survival to hospital discharge
Secondary:
1. Favorable neurologic outcome at time of discharge, defined by a modified Rankin score of ≤3.
2. Rate of adverse events.
3. Hospital-free survival, defined as the number of days alive and permanently out of the hospital during the first 30 days after cardiac arrest.

Design

Cluster-randomized trial with crossover

Excluded

Traumatic injury, known pregnancy, EMS witnessed arrest, prisoners, a written advanced directive against resuscitation, asphyxial cause of arrest, uncontrolled bleeding/exsanguination, pre-existing tracheostomy, treated with mechanical chest compression device, initial CPR performed by non-participating EMS, advanced airway placed prior to participating EMS arrival

Primary Results

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

Survival to hospital discharge

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

Favorable neurologic function (Modified Rankin ≤3)

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

Critical Findings: No significant difference in primary and secondary outcomes between continuous chest compressions and interrupted chest compressions as performed by EMS in atraumatic out-of-hospital cardiac arrest patients.

Strengths

  • Pretreatment and post-treatment characteristics were similar
  • High quality chest compressions were performed consistently in both groups
  • Patients enrolled from multiple urban sites in the United States and Canada

Limitations

  • External validity: chest compression fractions were high in both groups but the excellent CPR provided here regardless of continuous vs interrupted CPR may not reflect what occurs in the “real-world”
  • The rate of transfer and subsequent admission to hospital was higher in the interrupted CPR group. It is unclear why this occurred.
  • Post-resuscitation management was not included in the study

Discussion

The CPR protocols performed by the intervention and control groups were only different in the first 6 minutes of resuscitation. Three 2 minute cycles of compressions (either continuous or interrupted) were performed by each group with ventilations delivered via bag valve mask. After the first 6 minutes, advanced airways were then placed followed by both intervention and control groups continuing thereon with continuous chest compressions.

Since 6 minutes can be a relatively short time for a resuscitation, this may not be enough to generate a significant difference between the continuous and interrupted strategies.

Author's Conclusions

“In conclusion, among patients with out-of-hospital cardiac arrest in whom CPR was performed by EMS providers, a strategy of continuous chest compressions with positive-pressure ventilation did not result in significantly higher rates of survival or favorable neurologic status than the rates with a strategy of chest compressions interrupted for ventilation.”

Our Conclusions

In this well-designed trial, there was no difference in survival to hospital discharge for patients with OHCA who received either continuous or interrupted chest compressions. However, given the significant training and quality assurance to ensure consistent chest compressions, external validity of this trial is unclear. Regardless of the approach to chest compressions, providers should ensure a high compression fraction to maximize good outcomes.

Potential Impact To Current Practice

As majority of these cardiac arrest patients arrive with EMS placed advanced airways, ED providers are likely already performing continuous chest compressions. But as this study did not find significant outcome differences between continuous chest compressions, as compared to interrupted, for patients without advanced airways the priority should continue to focus on the importance of high-quality CPR while minimizing the number and duration of pauses.

Bottom Line

The key to successful resuscitation in cardiac arrest continues to be high-quality CPR with a high compression fraction.

Read More

REBEL EM: December 2015 All Cardiology REBEL Cast

The Bottom Line: ROC-CCC: Trial of Continuous or Interrupted Chest Compressions During CPR

References

Cunningham LM et al. Cardiopulmonary Resuscitation for Cardiac Arrest: The Importance of Uninterrupted Chest Compressions in Cardiac Arrest Resuscitation. American Journal of Emergency Medicine. 2012; 30: 1630-1638. PMID: 22633716

Neymar RW et al. Part 1: Executive Summary: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2015; 132: 1-36. PMID: 26472989