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Chest Compression Fraction and Survival from Cardiac Arrest

Minimizing interruption of chest compressions is associated with improved survival.

Previous studies have shown that chest compression is performed only about 50% of the applicable time during prehospital cardiopulmonary resuscitation efforts. In this multicenter, observational cohort study, researchers assessed the fraction of CPR time spent on chest compressions and its effect on survival in patients with out-of-hospital cardiac arrest who had an initial rhythm of ventricular fibrillation or ventricular tachycardia and who had received CPR for at least 1 minute prior to shock. The authors analyzed records for 506 patients who were treated by 78 emergency medical services systems in Canada and the U.S. from 2005 to 2007. The proportion of time dedicated to chest compressions during 1-minute intervals was measured by changes in thoracic impedance recorded from the defibrillator electrodes.

Overall, 23% of patients survived to hospital discharge. Patients were categorized into five groups according to the average proportion of time spent on chest compressions: 0%–20% (100 patients), 21%–40% (74), 41%–60% (117), 61%–80% (143), and 81%–100% (72). After adjustment for potentially confounding variables, the odds ratio for survival to discharge was 3.01 in the group with an average chest compression fraction of 61%–80% compared with the group with the lowest fraction. The authors estimate that a 10% increase in chest compression fraction would result in an OR for survival of 1.11.

Comment: The group with a chest compression fraction of 81%–100% in this study was small, and the associated OR for survival was not statistically significant; however, the finding of improved survival in the group with an average fraction of 61%–80% is compelling. Increasing the proportion of CPR time dedicated to chest compression is associated with a modest improvement in survival. Although this type of study cannot prove causation, a causal relation is plausible and makes biological sense.

— Aaron E. Bair, MD, MSc, FAAEM, FACEP

Published in Journal Watch Emergency Medicine October 30, 2009

Citation(s):

Christenson J et al. Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation. Circulation 2009 Sep 29; 120:1241.

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Reader Remarks:

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• CPR
  Gene J Blanchfield, 2 Nov 2009 1:55 PM EST
  Has anyone used or done a study on automatic cnest compression devices (Lucus) and rate of survivability? Just the fact... [more]
• Chest compression = sufficient ventilation
  Mark Hays, 13 Nov 2009 1:10 PM EST
  As a number of new studies have shown, 100% chest compression is the most effective onsite treatment.
  
  Those who have... [more]