Resuscitation 93 (2015) A7–A8
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Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Editorial
One swallow does not make a summer
More studies continue to be published on the outcome of mechanical chest compression. Not only do these devices deliver uninterrupted high quality chest compressions, but they also enable chest compressions to be performed continuously, even during defibrillation, enabling the delivery of a high chest compression fraction. Additionally, the load-distributing band (LDB) can, with some defibrillators, synchronise defibrillation to the relaxation phase, when it is thought to be more successful. Our understanding of the pathophysiology of cardiac arrest, animal studies and some clinical data would suggest that these attributes would combine to enhance outcome from mechanical CPR, but studies to date have failed to demonstrate any difference in overall survival to hospital discharge between the mechanical and manual CPR groups.1–3 The reasons for this are unclear and further analysis of some of these studies may help understand why this is the case. In this edition of Resuscitation, Olsen et al. present further analysis of the original Circulation Improving Resuscitation Care (CIRC) trial data, which compared high quality manual cardiopulmonary resuscitation (M-CPR) with Autopulse integrated load-distributing band CPR (LDB-CPR) in out-of-hospital cardiac arrest.4 Based on previous studies which demonstrated that pre-shock pauses adversely affect the success of the ensuing defibrillation, the authors specifically investigated the effect of pre-shock chest compression pauses on the termination of fibrillation (TOF) and return of organised rhythm (ROOR) for CIRC patients in both the mechanical and manual CPR groups. Both LINC,5 PARAMEDIC6 and the present CIRC–trial7 protocols specified that defibrillation should be attempted without stopping chest compressions. The authors proposed that shorter pre-shock pauses in both LDB-CPR and MCPR patients would be associated with higher rates of termination of fibrillation (TOF) and a return of an organised rhythm (ROOR), and specifically that patients within the LDB-CPR group with no pre-shock pause would have the highest TOF of all. This secondary analysis concluded that for first shocks with LDB-CPR, TOF was associated with pre-shock pause duration, but there was no association with the rate of ROOR. However, for M-CPR, where chest compressions were interrupted to give defibrillation shocks, there was no association between pre-shock pause duration and TOF or ROOR, contrary to other studies of M-CPR demonstrating a convincing relation between pre-shock pause with TOF and ROSC.8 Since 2010, both European and American the resuscitation guidelines have emphasised the need to minimise peri-shock interruptions to chest compressions.9,10 These recommendations were based on a number of studies showing that peri-shock interruption
http://dx.doi.org/10.1016/j.resuscitation.2015.05.006 0300-9572/© 2015 Elsevier Ireland Ltd. All rights reserved.
of CPR is associated with a decreased probability of conversion of VF to another rhythm,11 defibrillation failure,12 reduced ROSC and survival,11 and immediate resumption of chest compressions after defibrillation is associated with better survival rates and/or survival with favourable neurological outcome.13,14 However, results have not been consistent across all studies and a previous AED study, which included CPR during charging, and immediate resumption of chest compressions after shock delivery, did not show significantly improved survival to admission or to discharge.15 The results of Olsen’s study have also failed to demonstrate a relationship between pre-shock pause and TOF or ROOR during M-CPR, although the relationship with TOF when using LDB-CPR was consistent with studies on which recommendations to minimise peri-shock pauses were based. Understanding these inconsistent results is challenging and adds to the difficulties in interpreting the results of studies of mechanical chest compression during CPR. Uninterrupted chest compressions delivered by mechanical devices may improve shock success, but perhaps adversely affect overall outcome by making the myocardium more prone to recurrent VF. Although not demonstrated by all studies,16 there is some evidence that immediate resumption of chest compressions after defibrillation is associated with earlier VF recurrence,17 which may be a mechanism to at least consider when interpreting these results. Olsen et al. did not analyse post-shock pauses in their post hoc analysis, which might be helpful in interpreting these results further. Recent studies have also demonstrated that defibrillation may be more successful during the relaxation phase of each chest compression,18 and it is unclear from these results whether shocks delivered to the LDBCPR group were synchronised to the upstroke. Both the pre-shock and post-shock components of the resuscitation sequence may contribute to overall outcome and in order to better understand the complexities of mechanical CPR outcomes, perhaps both need examining as independent variables rather than the assumption that they both contribute adversely to outcome. However, one swallow does not make a summer and it is important that the emphasis on minimising peri-shock pauses remains. Despite current guidelines recommendations, interruptions to chest compressions during CPR remain significant, even in well-trained teams.19 A common cause of these interruptions is defibrillation, as the team stands back while the shock is delivered. Attempts to perform hands-on defibrillation, thereby mimicking that achieved with M-CPR are unsafe when using clinical examination gloves,20–22 but may be possible when using appropriately
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Editorial / Resuscitation 93 (2015) A7–A8
rated safety gloves.23,24 Maximising chest compression fraction is, and will remain, a priority in the delivery of high quality CPR and mechanical devices can certainly achieve this, even if not an improved outcome. Conflict of interest statement CDD was a researcher and member of the clinical steering group for the Pre-hospital Randomised Assessment of Mechanical compression Device In Cardiac arrest PaRAMeDIC Trial. http://www. controlled-trials.com/ISRCTN08233942. References 1. Perkins GD, Lall R, Quinn T, et al. Mechanical versus manual chest compression for out-of-hospital cardiac arrest (PARAMEDIC): a pragmatic, cluster randomised controlled trial. Lancet 2015;385:947–55. 2. Rubertsson S, Lindgren E, Smekal D, et al. Mechanical chest compressions and simultaneous defibrillation vs conventional cardiopulmonary resuscitation in out-of-hospital cardiac arrest: the LINC randomized trial. JAMA 2014;311:53–61. 3. Wik L, Hansen TB, Fylling F, et al. Delaying defibrillation to give basic cardiopulmonary resuscitation to patients with out-of-hospital ventricular fibrillation: a randomized trial. JAMA 2003;289:1389–95. 4. Olsen JA, Brunborg C, Steinberg M, et al. Pre-shock chest compression pause effects on termination of ventricular fibrillation/tachycardia and return of organized rhythm within mechanical and manual cardiopulmonary resuscitation. Resuscitation 2015;93:158–63. 5. Rubertsson S, Silfverstolpe J, Rehn L, et al. The study protocol for the LINC (LUCAS in cardiac arrest) study: a study comparing conventional adult out-ofhospital cardiopulmonary resuscitation with a concept with mechanical chest compressions and simultaneous defibrillation. Scand J Trauma Resusc Emerg Med 2013;21:5. 6. Perkins GD, Woollard M, Cooke MW, et al. Prehospital randomised assessment of a mechanical compression device in cardiac arrest (PaRAMeDIC) trial protocol. Scand J Trauma Resusc Emerg Med 2010;18:58. 7. Lerner EB, Persse D, Souders CM, et al. Design of the Circulation Improving Resuscitation Care (CIRC) Trial: a new state of the art design for out-of-hospital cardiac arrest research. Resuscitation 2011;82:294–9. 8. Tomkins WG, Swain AH, Bailey M, Larsen PD. Beyond the pre-shock pause: the effect of prehospital defibrillation mode on CPR interruptions and return of spontaneous circulation. Resuscitation 2013;84:575–9. 9. 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: S685–705. 10. Koster RW, Baubin MA, Bossaert LL, et al. European Resuscitation Council Guidelines for Resuscitation 2010 Section 2. Adult basic life support and use of automated external defibrillators. Resuscitation 2010;81: 1277–92.
11. Eftestol T, Sunde K, Steen PA. Effects of interrupting precordial compressions on the calculated probability of defibrillation success during out-of-hospital cardiac arrest. Circulation 2002;105:2270–3. 12. Edelson DP, Abella BS, Kramer-Johansen J, et al. Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest. Resuscitation 2006;71:137–45. 13. Rea TD, Helbock M, Perry S, et al. Increasing use of cardiopulmonary resuscitation during out-of-hospital ventricular fibrillation arrest: survival implications of guideline changes. Circulation 2006;114:2760–5. 14. Steinmetz J, Barnung S, Nielsen SL, Risom M, Rasmussen LS. Improved survival after an out-of-hospital cardiac arrest using new guidelines. Acta Anaesthesiol Scand 2008;52:908–13. 15. Jost D, Degrange H, Verret C, et al. DEFI 2005: a randomized controlled trial of the effect of automated external defibrillator cardiopulmonary resuscitation protocol on outcome from out-of-hospital cardiac arrest. Circulation 2010;121:1614–22. 16. Conover Z, Kern KB, Silver AE, Bobrow BJ, Spaite DW, Indik JH. Resumption of chest compressions after successful defibrillation and risk for recurrence of ventricular fibrillation in out-of-hospital cardiac arrest. Circ Arrhythm Electrophysiol 2014;7:633–9. 17. Berdowski J, Tijssen JG, Koster RW. Chest compressions cause recurrence of ventricular fibrillation after the first successful conversion by defibrillation in out-of-hospital cardiac arrest. Circ Arrhythm Electrophysiol 2010;3:72–8. 18. Steinberg MT, Olsen J-A, Brunborg C, et al. Abstract 85: defibrillation during mechanical chest compressions should be avoided during the downstroke phase of the chest compression cycle. Circulation 2014;130(Suppl. 2):A85. 19. Cheskes S, Hillier M, Byers A, et al. The association between manual mode defibrillation, pre-shock pause duration and appropriate shock delivery when employed by basic life support paramedics during out-of-hospital cardiac arrest. Resuscitation 2015;90:61–6. 20. Deakin CD, Lee-Shrewsbury V, Hogg K, Petley GW. Do clinical examination gloves provide adequate electrical insulation for safe hands-on defibrillation? I: Resistive properties of nitrile gloves. Resuscitation 2013;84:895–9. 21. Lemkin DL, Witting MD, Allison MG, Farzad A, Bond MC, Lemkin MA. Electrical exposure risk associated with hands-on defibrillation. Resuscitation 2014;85:1330–6. 22. Petley GW, Deakin CD. Do clinical examination gloves provide adequate electrical insulation for safe hands-on defibrillation? II: Material integrity following exposure to defibrillation waveforms. Resuscitation 2013;84:900–3. 23. Kerber RE. Hands-on defibrillation: “Gloves as sweet as damask roses” (William Shakespeare: The Winter’s Tale). Resuscitation 2015;90:A6–7. 24. Deakin CD, Thomsen JE, Lofgren B, Petley GW. Achieving safe hands-on defibrillation using electrical safety gloves – a clinical evaluation. Resuscitation 2015;90:163–7.
Charles D. Deakin NIHR Southampton Respiratory Biomedical Research Unit, University Hospital Southampton, Southampton, SO16 6YD, United Kingdom E-mail address:
[email protected] 12 May 2015
