Elsevier

Resuscitation

Volume 71, Issue 2, November 2006, Pages 137-145
Resuscitation

Clinical paper
Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest

https://doi.org/10.1016/j.resuscitation.2006.04.008Get rights and content

Summary

Background

Cardiopulmonary resuscitation (CPR) and electrical defibrillation are the primary treatment options for ventricular fibrillation (VF). While recent studies have shown that providing CPR prior to defibrillation may improve outcomes, the effects of CPR quality remain unclear. Specifically, the clinical effects of compression depth and pauses in chest compression prior to defibrillation (pre-shock pauses) are unknown.

Methods

A prospective, multi-center, observational study of adult in-hospital and out-of-hospital cardiac resuscitations was conducted between March 2002 and December 2005. An investigational monitor/defibrillator equipped to measure compression characteristics during CPR was used.

Results

Data were analyzed from 60 consecutive resuscitations in which a first shock was administered for VF. The primary outcome was first shock success defined as removal of VF for at least 5 s following defibrillation. A logistic regression analysis demonstrated that successful defibrillation was associated with shorter pre-shock pauses (adjusted odds ratio 1.86 for every 5 s decrease; 95% confidence interval 1.10–3.15) and higher mean compression depth during the 30 s of CPR preceding the pre-shock pause (adjusted odds ratio 1.99 for every 5 mm increase; 95% confidence interval 1.08–3.66).

Conclusions

The quality of CPR prior to defibrillation directly affects clinical outcomes. Specifically, longer pre-shock pauses and shallow chest compressions are associated with defibrillation failure. Strategies to correct these deficiencies should be developed and consideration should be made to replacing current-generation automated external defibrillators that require long pre-shock pauses for rhythm analysis.

Introduction

Although rapid defibrillation remains the cornerstone of treatment for ventricular fibrillation (VF), a number of studies have supported the notion that cardiopulmonary resuscitation (CPR), especially in the time preceding defibrillation, may also play a key therapeutic role.1, 2 However, the effect of CPR quality on clinical outcomes remains poorly understood.

Recent work, relying on new technology capable of sensing compression rate and depth, has shown that CPR quality is inconsistent in actual clinical practice, with frequent pauses and shallow compression depth.3, 4 Using this technology, the effects of these CPR variables on clinical outcomes can now be evaluated. Of particular interest are the duration of time from the end of chest compressions until the defibrillation shock is given (i.e., the pre-shock pause) and the measured depth of chest compressions preceding defibrillation. Both have been shown to have significant impact on outcomes in animal studies,5, 6, 7, 8 yet neither has been rigorously investigated in the clinical setting.

Understanding the effects of these variables has significant public health and policy implications. Pre-shock pauses are particularly important as automated external defibrillators (AEDs), that generally require long pre-shock pauses for rhythm analysis,8, 9, 10 have gained widespread acceptance and have been implemented in a variety of settings.11, 12, 13, 14 Additionally, understanding the relative importance of these variables of CPR quality on outcomes will have implications for resuscitation guidelines and training. We therefore examined whether pre-shock pause and compression depth, two likely determinants of blood flow preceding defibrillation, affect the ability of a shock to terminate VF.

Section snippets

Study design

An international, multi-center, observational study of in-hospital and out-of-hospital cardiac arrests occurring between March 2002 and December 2005 was conducted. Approval was granted by the Institutional Review Board of the University of Chicago Hospitals and the regional ethics committee in Akershus, with mechanisms to satisfy waiver of consent provisions at both sites. Additionally, an oral consent process was used for rescuers in Chicago.

Details of the study design and methods have been

Results

A total of 60 patients received a first electrical shock for VF during the study period. Table 1 summarizes the baseline characteristics of the entire cohort. Characteristics of successful and unsuccessful shocks are compared in Table 2, Table 3. There were no statistically significant differences in age, sex, arrest location or time to shock by first shock success. However, successful shocks were associated with a shorter median pre-shock pause duration (11.9 s versus 22.7 s; p = 0.002) and higher

Discussion

Using technology that measures multiple variables of CPR quality accurately, our international study group has gathered data that demonstrate a significant association between termination of VF and two variables that have received little formal evaluation during human cardiac arrest, pre-shock pause duration and compression depth. Specifically, we have shown that each 5 mm increase in compression depth and each 5 s decrease in pre-shock pause portend an approximate two-fold increase in the

Conclusions

Using objective measurements of CPR quality during actual cardiac arrest, we have found that longer pre-shock pauses and shallower chest compressions are correlated significantly with decreased shock success. The opportunity to improve the quality of CPR in clinical practice is now practically available and may significantly improve resuscitation success. Approaches to minimize (or eliminate) pre-shock pauses and optimize compression depth should be made and consideration should be given to the

Conflict of interest

The sponsor had no role in data collection, interpretation of results or drafting of the manuscript. One author at the study sponsor (Mr. Myklebust) was involved in study conception and design. Drs. Abella and Becker have received honoraria and research support from Philips Medical Systems (Andover, MA) and Laerdal Medical Corporation (Stavanger, Norway) while Drs. Steen, Wik and Kramer-Johansen have received research support from Laerdal Medical Corporation (Stavanger, Norway).

Acknowledgements

We thank Jason Alvarado, Nicholas O’Hearn, Kuang-Ning Huang, Salem Kim, Nate Teisman and David Snyder, PhD for assistance during data collection and manuscript preparation; Ronald Thisted, MD for advice and statistical expertise; and Lynne Harnish for administrative assistance. We also thank the paramedics and instructors in the Akershus Ambulance Service and the members of the cardiac arrest resuscitation team at the University of Chicago. This work was supported by a grant from the Laerdal

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    A Spanish translated version of the summary of this article appears as Appendix in the online version at 10.1016/j.resuscitation.2006.04.008.

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