Elsevier

Resuscitation

Volume 85, Issue 8, August 2014, Pages 1007-1011
Resuscitation

Clinical paper
Compressions during defibrillator charging shortens shock pause duration and improves chest compression fraction during shockable out of hospital cardiac arrest

https://doi.org/10.1016/j.resuscitation.2014.05.001Get rights and content

Abstract

Background

Previous studies have demonstrated significant relationships between shock pause duration and survival to hospital discharge from shockable out-of hospital (OHCA) cardiac arrest. Compressions during defibrillator charging (CDC) has been proposed as a technique to shorten shock pause duration.

Objective

We sought to determine the impact of CDC on shock pause duration and CPR quality measures in shockable OHCA.

Methods

We performed a retrospective review of all treated adult OHCA occurring over a 1 year period beginning August 1, 2011 after training EMS agencies in CDC. We included OHCA patients with an initial shockable rhythm, available CPR process data and shock pause data for up to the first three shocks of the resuscitation. CDC by EMS personnel was confirmed by review of impedance channel measures. We evaluated the relationship between CDC and shock pause duration as the primary outcome measure. Secondary outcome measures investigated the association between CDC and CPR quality measures.

Results

Among 747 treated OHCA 149 (23.4%) presented in a shockable rhythm of which 129 (81.6%) met study inclusion criteria. Seventy (54.2%) received CDC. There was no significant difference between the CDC and no CDC group with respect to Utstein variables. Median pre-shock pause (15.0 vs. 3.5 s; Δ 11.5; 95% CI: 6.81, 16.19), post-shock pause (4.0 vs. 3.0 s; Δ 1.0; 95% CI: −2.57, 4.57), and peri-shock pause (21.0 vs. 9.0 s; Δ 12.0; 95% CI: 5.03, 18.97) were all lower for those who received CDC. Mean chest compression fraction was significantly greater (0.77 vs. 0.70, Δ 0.07; 95% CI: 0.03, 0.11) with CDC. No significant difference was noted in compression rate or depth with CDC. Clinical outcomes did not differ between the two approaches (return of spontaneous circulation 62.7% vs. 62.9% p = 0.98, survival 25.4% vs. 27.1% p = 0.82), although the study was not powered to detect clinical outcome differences.

Conclusions

Compressions during defibrillator charging may shorten shock pause duration and improves chest compression fraction in shockable OHCA. Given the impact on shock pause duration, further study with a larger sample size is required to determine the impact of this technique on clinical outcomes from shockable OHCA.

Introduction

Survival from out-of-hospital cardiac arrest (OHCA) continues to challenge Emergency Medical Services (EMS) systems.1, 2, 3 With the advent of the 2010 American Heart Association-International Liaison Committee on Resuscitation (AHA-ILCOR) guidelines for Cardiopulmonary Resuscitation (CPR), interest has focused on improving survival through improvements in CPR.4, 5 Chest compression fraction (CCF), compression rate and depth, peri-shock pause duration and chest compression release velocity have all been associated with improved survival to hospital discharge from OHCA.6, 7, 8, 9 Shorter peri-shock pause duration and in particular pre-shock pause duration have as well been associated with improved neurological outcome from OHCA.10 Defibrillator mode (automatic or manual mode) is known to have a significant impact on pre-shock pause duration as a result of the mandatory time required for both defibrillator analysis and charging in automatic mode.10, 11 A variety of techniques have been shown to decrease pre-shock pause duration when employed by providers in a simulated resuscitation environment.12 Chest compressions performed during the defibrillator charging phase (CDC) is one technique that has been suggested in an attempt to mitigate the impact of defibrillator charging time on pre-shock pause duration. Edelson et al.13 previously have demonstrated significant improvements in pre-shock pause duration by employing CDC in the inhospital environment. No previous studies have examined the impact of CDC performed by paramedics during OHCA. If CDC consistently shortens pre-shock pause duration, it may have significant impact on both termination of ventricular fibrillation and survival from OHCA. We therefore sought to explore the impact of CDC on shock pause duration and CPR quality metrics during shockable OHCA.

Section snippets

Setting and design

The study took place in the Regions of Peel and Halton in the province of Ontario, Canada. The regions cover an area of 2040 km2 and have a combined population of 1.6 million people. EMS responds to a volume of 100,000 emergency calls per year. Prehospital medical care is provided by advanced care paramedics (full advanced life support skills) and primary care paramedics (basic life support skills with the addition of a small number of medications and manual defibrillation). Both agencies are

Study population

Patients eligible for this study included those 18 years of age and older who sustained non-traumatic OHCA with a first EMS rhythm of ventricular fibrillation or pulseless ventricular tachycardia (VF/VT) for which CPR process data for at least one shock was obtained. The initial rhythm was determined to be VF/VT if the initial rhythm was interpreted as VF/VT by the initial EMS provider and a shock was provided. Patients were excluded if they received public access defibrillation before EMS

Measurement

CPR process data from all eligible resuscitations were reviewed and assessed for duration of pre- and post-shock pauses, CCF, compression rate and compression depth up to and including only the third shock, to minimize confounding by other resuscitation interventions (intubation, intravenous epinephrine or intravenous antiarrythmics). Pre-shock pause was defined as the time interval between chest compression cessation (as detected in the impedance channel waveform) and shock delivery.

Statistical analysis

Descriptive statistics were used to assess whether baseline characteristics remained consistent across study cohorts (CDC and non-CDC). The relationship between CDC and all outcome measures (median shock pause duration, CPR quality metrics, ROSC, and survival to hospital discharge) was calculated by univariate regression analysis using a chi-squared test. To ensure our findings were robust and not cofounded by the limitation of our analysis to the first three shocks of each resuscitation, we

Results

Fig. 1 displays a CONSORT diagram of all cases included in the study. Of 747 treated, unwitnessed cardiac arrest resuscitations, 20% had an initial arrest rhythm of VF/VT. Of those 149, CPR process data was missing on 20 cases leaving 129 for analysis. Seventy (54%) of these cases were identified as CDC cases.

Table 1 compares the baseline characteristics of both study cohorts. No significant differences in Utstein variables or resuscitation duration were noted between the two cohorts. Shocks

Discussion

To our knowledge, this study represents the only out-of-hospital study to date examining the relationship between CDC and shock pause duration, CPR quality metrics and clinical outcome measures. Study data analysis demonstrated significant improvement in both shock pause durations (pre- and peri-) and CCF. These improvements persisted regardless of whether the analysis was performed on a patient based or shock based analysis. As expected, there was no significant association between chest

Conclusion

Compressions during defibrillator charging may shorten shock pause duration and improves chest compression fraction in shockable OHCA. Further study with a larger sample size is required to determine the impact of this technique on clinical outcomes from shockable OHCA.

Conflict of interest statement

Dr. Cheskes has received speaking honorarium from Zoll Medical. Dr. Cheskes has received grant funding as Co PI, Toronto site, Resuscitation Outcomes Consortium. Dr. Morrison has received grant funding as PI, Toronto site, Resuscitation Outcomes Consortium. No other grant disclosures.

Acknowledgements

We would like to acknowledge the hard work and dedication of all paramedics of both the Region of Peel Paramedic Service and Halton EMS. Research in the pre-hospital setting would not be possible without the tireless efforts of their paramedics.

References (22)

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  • Cited by (24)

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      Prior studies have characterized ventilation quality over the entirety of resuscitation without considering shorter but potentially important episodes of hypo- or hyperventilation.3 Previously we demonstrated the feasibility of using the continuous capnography signal from modern portable cardiac monitors to characterize ventilation rate during OHCA.6–12 Important considerations in the analysis of the capnogram include the methods used to calculate the ventilation rate and the resulting estimates of hypo- and hyperventilation.

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      Prior studies characterizing ventilation parameters such as ventilation rate and end-tidal carbon dioxide (ETCO2) levels have relied upon discrete measurements or manual assessment of resuscitation records.4 Modern portable cardiac monitors enable continuous real-time recordings of resuscitation parameters such as thoracic impedance, chest compression depth and ETCO2 levels.7–13 We previously demonstrated the utility of advanced automated signal processing techniques in characterizing chest compressions delivered to OHCA patients.14–16

    • Effect of a resuscitation quality improvement programme on outcomes from out-of-hospital cardiac arrest

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      In particular, our median pre-shock pause of 5 s is considerably lower than what is possible with semi-automatic defibrillation,21–23 and this may be an important factor contributing to the observed increases in survival.24 Some EMS systems have shown that median pre-shock pauses of less than 3 s are possible in manual mode,11,25,26 and this may be an area for future improvement in our system. We made a number of discrete changes to resuscitation practice which may have also contributed to our results.

    • Optimizing CPR performance with CPR coaching for pediatric cardiac arrest: A randomized simulation-based clinical trial

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      CPR Coaches were trained in a standardized fashion, within 48 h prior to the CPA scenario. Coaches were instructed to: (i) point at the CPR feedback output on the defibrillator; (ii) provide corrective verbal feedback based on CPR feedback output (e.g. “press harder, aim for 5.5 cm”); (iii) provide positive feedback for good CPR performance; (iv) coordinate the appropriate compression:ventilation ratio prior to intubation; (v) coordinate key tasks to reduce pause duration (e.g. “in 15 s we will pause to check rhythm, pulse and switch compressors”); and (vi) remind CPR providers to deliver continuous compressions during intubation attempt or defibrillator charging [18,19]. Control arm resuscitation teams had the same team composition and size, but instead of a CPR Coach there was an extra bedside provider.

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    A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.05.001.

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