Trial of Continuous or Interrupted Chest Compressions During CPR

Princess Igwe, Mercer University College of Pharmacy

According to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, high-quality conventional cardiopulmonary resuscitation (manual chest compressions with rescue breaths) generates about 25% to 33% of normal cardiac output and oxygen delivery. The American Heart Association recommends that during resuscitation, chest compressions must be of adequate rate and depth, allowing complete recoil of the chest after each compression. It is also recommended that interruptions in chest compressions and excessive ventilation be avoided. [1]

The Centers for Disease Control and Prevention state that 7% of people who experience an out-of-hospital cardiac arrest in the United States each year survive. It is suggested that early cardiopulmonary resuscitation (CPR) with an emphasis on chest compressions is one of the key components to survival post-cardiac arrest. [2]

Title: Trial of Continuous or Interrupted Chest Compressions During CPR [3]
Design Cluster-randomized trial with crossover; N= 23,711
Objective To assess whether outcomes after continuous compressions with positive-pressure ventilation differed from those after compressions that were interrupted for ventilations at a ratio of 30 compressions to two ventilations
Study Groups Intervention group: received continuous chest compressions; n= 12,653

Control group: received interrupted chest compressions; n= 11,058

Methods *Eight Resuscitation Outcomes Consortium (ROC) sites and 114 Emergency Medical Services (EMS) agencies participated in this trial.

*The trial included adults with non–trauma-related out-of-hospital cardiac arrest who received chest compressions performed by providers from participating EMS agencies who were dispatched to the scene.

*The 114 participating EMS agencies were grouped into 47 clusters. Clusters were randomly assigned, in a 1:1 ratio, to perform continuous chest compressions or interrupted chest compressions during all the out-of-hospital cardiac arrests to which they responded.

*Patients assigned to the intervention group received continuous chest compressions at a rate of 100 compressions per minute, with asynchronous positive-pressure ventilations delivered at a rate of 10 ventilations per minute.

*Patients assigned to the control group were to receive compressions that were interrupted for ventilations at a ratio of 30 compressions to two ventilations; ventilations were to be given with positive pressure during a pause in compressions of less than 5 seconds in duration.

Duration June 6, 2011 to May 28, 2015
Primary Outcome Measure The rate of survival to hospital discharge
Baseline Characteristics   Intervention Group

(n= 12,653)

Control Group

(n= 11,058)

Age — yr 66.4 ± 17.2 66.2 ± 17.0
Male sex — no. (%) 8,029 (63.5) 7,126 (64.4)
Bystander-initiated CPR — no./total no. (%) 5,859/12,491 (46.9) 5,129/10,901 (47.1)
Time from dispatch to first arrival of EMS (Mean — min) 5.9 ± 2.5 5.9 ± 2.6
Receipt of advanced life support at the scene — no. (%) 12,286 (97.1) 10,741 (97.1)
Results   Intervention Group Control Group Adjusted Difference (95% CI) p-value
Primary outcome: survival to discharge — no./total no. (%) 1,129/12,613 (9.0) 1,072/11,035 (9.7) −0.7 (−1.5 to 0.1) 0.07
Transport to hospital — no. (%)


6,686 (52.8) 6,066 (54.9) −2.0 (−3.6 to −0.5) 0.01
Return of spontaneous circulation at ED arrival — no./total no. (%) 3,058/12,646 (24.2) 2,799/11,051 (25.3) −1.1 (−2.4 to 0.1) 0.07
Admission to hospital — no./total no. (%) 3,108/12,653 (24.6) 2,860/11,058 (25.9) −1.3 (−2.4 to −0.2) 0.03
Survival to 24 hr — no./total no. (%) 2,816/12,614 (22.3) 2,569/11,031 (23.3) −1.0 (−2.1 to 0.2) 0.10
Hospital-free survival — days 1.3 ± 5.0 1.5 ± 5.3 −0.2 (−0.3 to −0.1) 0.004
Discharge home — no./total no. (%) 844/12,613 (6.7) 794/11,034 (7.2) −0.5 (−1.2 to 0.2) 0.15
Modified Rankin scale score ≤ 3 — no./total no. (%)


883/12,560 (7.0) 844/10,995 (7.7) −0.6 (−1.4 to 0.1) 0.09
Results (continued) ·         Hospital-free survival was defined as the number of days alive and permanently out of the hospital during the first 30 days after the cardiac arrest.

·         Scores on the modified Rankin scale range from 0, indicating no symptoms, to 6, indicating death; a score of 3 or less indicates favorable neurologic function.

Adverse Events Common Adverse Events:
Pre-Hospital Events Intervention Group Control Group Difference p-value
Emesis – n (%) 1,311 (10.4%) 1,197 (10.8%) -0.5% (-1.0%, 0.1%) 0.11
Airway bleeding – n (%) 881 (7.0%) 765 (6.9%) 0.0% (-0.8%, 0.8%) 0.91
Airway complications – n (%) 218 (1.7%) 212 (1.9%) -0.2% (-0.5%, 0.2%) 0.28
Serious Adverse Events: Death (9.2% in Intervention Group, 9.9% in Control Group, Difference 0.7% (-0.1%, 1.4%), p = 0.09)
Percentage that Discontinued due to Adverse Events: Not applicable
Study Author Conclusions In patients with out-of-hospital cardiac arrest, continuous chest compressions during CPR performed by EMS providers did not result in significantly higher rates of survival or favorable neurologic function than did interrupted chest compressions.

This study did not find continuous chest compressions to be more effective than interrupted chest compressions at improving patients’ survival to discharge post-cardiac arrest. In fact, per-protocol analyses revealed that patients who received continuous chest compressions had lower survival rates than patients who received interrupted chest compressions. In previous interventional studies, it was shown that continuous chest compressions improved survival; however this observed improvement may have been due to improved CPR procedure rather than implementation of continuous compressions alone. Given that the CPR procedure was consistent in both treatment groups in this study, good quality CPR administered by EMS responders should continue to be an important component of positive clinical outcomes.


  1. Berg RA, Hemphill R, Abella BS, et al. Part 5: adult basic life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010; 122: Suppl 3: S685-705.
  2. CARES Strengthens Links in Chain of Survival. Centers for Disease Control and Prevention website Updated March 19, 2014. Accessed November 30, 2015.
  3. Nichol G, Leroux B, Wang H, et al. Trial of Continuous or Interrupted Chest Compressions during CPR. N Engl J Med. 2015. doi: 10.1056/NEJMoa1509139.




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