Elsevier

Resuscitation

Volume 67, Issue 1, October 2005, Pages 95-101
Resuscitation

Reducing no flow times during automated external defibrillation

https://doi.org/10.1016/j.resuscitation.2005.04.009Get rights and content

Abstract

There has recently been an increased attention focused on the importance of reducing time without blood flow from chest compressions (no flow time, NFT) during cardiopulmonary resuscitation (CPR). In this study we have analyzed and quantified the NFTs during external automatic defibrillation in 105 cardiac arrest patients. We found that for around half of the time (about 10 min), these patients were not perfused. We have proposed methods to reduce NFT in connection with analyses and shocks. The key factors were rhythm analysis during ongoing CPR, capacitor charging during analysis, 1 min of CPR immediately after a shock (with rhythm analysis during CPR at the end of the 1 min), and distinguishing between asystole and organized rhythm in analyses to skip pulse check if asystole.

The potential reduction in NFT using these methods was calculated theoretically and we found a reduction in the total NFT of about 4.5 and 1 min, respectively, in the subgroups of patients having at least one shock and patients having received no shocks. In the present study, the median NFT ratio could theoretically be reduced from 51% to 34% or 49% to 39% depending on if the patient would have a shockable rhythm or not.

By introducing the proposed methods into an AED, the NFT would be significantly reduced, hopefully increasing the survival.

Introduction

There has recently been focused on increased attention to the importance of reducing time without blood flow from chest compressions (no flow time, NFT) during cardiopulmonary resuscitation (CPR) [1], [2].

Cardiac output up to 20–30% of normal can be achieved with external chest compressions. This can maintain or even improve the probability of restoration of spontaneous circulation (ROSC) [3], while even short pauses in CPR reduce the probability of ROSC in a human study [4] and chance for survival and good neurological outcome in animal studies [5], [6], [7], [8].

Chest compressions and ventilations during CPR introduce artefacts in the electrocardiogram (ECG). For automated external defibrillators (AEDs) to perform reliable ECG signal analysis and make a shock/no-shock decision, CPR must be discontinued, introducing NFT. Other factors such as defibrillator charging, the delivery of shocks, checking for pulse, pauses for ventilations in non-intubated patients, etc. also contribute to the total NFT. In a recent study of 176 patients with out-of-hospital cardiac arrest attended to by paramedics and nurse anaesthetists, CPR was not given 48% of the time; 38% when subtracting the time required for ECG analysis and defibrillation [1].

This study will present a detailed analysis of the NFT time in 105 of these patients and propose possible technical solutions to reduce this time by incorporating new technology in the AED such as rhythm analysis during CPR. This can be done by first filtering the CPR artefacts using a multichannel adaptive filter, e.g. the MC-RAMP (MultiChannel Recursive Adaptive Matching Pursuit) filter previously described for such an application in [9], [10].

Section snippets

Data collection

The data were extracted as part of a prospective study of out-of-hospital cardiac arrest patients in Stockholm, Sweden (52 patients) and London, UK (53 patients) between April 2002 and October 2003. Approximately 40% of the patients in the original study [1] were treated with manual defibrillators and therefore not included. The data were recorded by standard Laerdal HeartStart 40002 defibrillators in semi-automatic mode modified to collect digitally the ECG and

NFT analysis of some common AED situations

For the four common AED situations listed in Section 2.4, we have in Table 1 listed the median NFT as found in the HS4000 data as well as for the proposed alternative solution. In the following, these four situations are further analyzed and illustrated.

When a shockable rhythm followed chest compressions, median NFT in the HS4000 data was 21.4 s (Fig. 1). This theoretically could be reduced to 7.4 s by analyzing the rhythm during compressions followed immediately after end of compressions by

Discussion

When ALS was attempted performed according to the international guidelines [11] by paramedics and nurse anaesthetists, approximately half the time was spent without chest compressions generating blood flow. This is identical to the result in the whole original material [1] whereas the present data were a subset, and similar to that reported by Van Alem et al. [12] for BLS with AEDs by first responders before the ALS team arrived.

We present a solution for reducing this no flow time from median

Conflict of Interest

J. Eilevstjønn, H. Myklebust and M. Stavland are employed by Laerdal Medical AS.

P.A. Steen is a Board member of Laerdal Medical AS.

Reference (23)

  • T. Eftestøl et al.

    Effects of CPR on predictors of VF defibrillation success during out-of-hospital cardiac arrest

    Circulation

    (2002)
  • Cited by (36)

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    • Single-shock defibrillation success in adult cardiac arrest: A systematic review

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      Another critical component to successful CPR is minimizing the time without chest compressions (no flow time [NFT]). Recently, there has been a focus on strategies to reduce NFT during CPR and external defibrillation [6–8]. Two prospective before-and-after studies have shown that there is a significant survival benefit associated with a single-shock defibrillation protocol compared with a three-stacked-shock protocol [9,10].

    • A review of chest compression interruptions during out-of-hospital cardiac arrest and strategies for the future

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      In cases where ECG analysis shows asystole or VF, an additional delay is often added for a confirmatory, and futile, pulse check (27). In such instances, a significant period of NFT could be avoided if the rescuer immediately restarts compressions in cases of asystole or immediately delivers a defibrillation in cases of VF when either of these two rhythms is identified on the ECG (27). Cardiac monitor and AED models that are able to filter out the artifact from compressions for rhythm analysis make compression pauses for traditional rhythm checks obsolete (29).

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    A Spanish translated version of the Abstract of this article appears as Appendix at 10.1016/j.resuscitation.2005.04.009.

    1

    At the time of the study, Joar Eilevstjønn was with the Department of Electrical and Computer Engineering, Stavanger University, Stavanger, Norway.

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