Chest Compression Rate: Where is the Sweet Spot?

Chest Compression Rate: Where is the Sweet Spot? Running title: Nolan et al.; Chest compression rate Jerry P. Nolan, FRCA, FCEM, FRCP, FFICM 1 ; Gavin D. Perkins, MMEd, MD, FRCP, FFICM 2 ; Jasmeet Soar, FRCA, FFICM 3 1 Royal United Hospital, NHS Trust, Bath; 2 University of Warwick, Warwick Medical School, Warwick; 3 Southmead Hospital, North Bristol NHS Trust, Bristol, United Kingdom Address dres for Correspondence: e Jerry P. Nolan, FRCA, FCEM, FRCP, FFICM Consultant in Anaesthesia & Intensive Care Medicine Royal United Hospital NHS Trust Bath, BA1 3NG United Kingdom Tel: +44-1225-825056 Fax: +44-1225-825061 E-mail: jerry.nolan@nhs.net Journal Subject Code: [25] CPR and emergency cardiac care Key words: cardiac arrest; cardiopulmonary resuscitation; chest compressionresuscitation; Editorials 1

The first description of modern cardiopulmonary resuscitation (CPR) included the instruction to compress the chest about 60 times per minute ; 1 however, the optimal compression rate was unknown. Franz Koenig is credited with describing the original technique for external cardiac massage, which included a compression rate of 30 40 min -1 ; 2 But in the first published description of external cardiac massage in 1892, Friedrich Maass documented a better clinical response with a rate of 120 min -1. 2 To this day, the optimal compression rate is the subject of controversy. Animal data indicate that cardiac output increases with compression rates up to as high as 150 min -1. 3 In a canine model of prolonged cardiac arrest, compression rates of 120 min -1 compared to 60 min -1 increased mean aortic (systolic and diastolic) and coronary perfusion pressures, and 24 hour survival (61% versus 15%, P=0.03). 4 In a study of nine patients ts undergoing CPR, a compression rate of 120 min -1 generated higher aortic peak pressures and coronary ry perfusion pressures compared with a compression rate of 60 min -1 (the rate recommended ended by the 1980 American Heart Association guidelines). ines). This evidence ence is supported by another study of 23 patients in cardiac ac arrest in which compressions sion s at 120 min -1 resulted in significantly higher end-tidal carbon dioxide de values compared with compressions sion ons at 80 min -1. 5 The first large, prospective, observational study of the influence of chest compression rate on patient survival was published in this journal in 2005. 6 The number of delivered chest compressions was recorded by trained observers during in-hospital resuscitation attempts. A higher chest compression rate was associated with a higher rate of return of spontaneous circulation (ROSC). The mean chest compression rate for initial survivors was 90 min -1 (SD 17) versus 79 min -1 (SD 18) in non-survivors (P<0.003). Following a systematic review of the available evidence, the 2010 International Liaison Committee on Resuscitation (ILCOR) consensus on CPR science with treatment 2

recommendations stated chest compression rates for adults in cardiac arrest should be at least 100 min -1, and that there was insufficient evidence to recommend a specific upper limit for compression rate. 7 There was also a recommendation for deeper (>50 mm) chest compressions. Based on the ILCOR statement, the current guidelines from the American Heart Association (AHA) recommend using a chest compression rate of at least 100 min -1 and a compression depth of at least 50 mm. 8 The 2010 European Resuscitation Council (ERC) guidelines differ slightly in that an upper compression rate limit of 120 min -1 and depth of 60 mm are recommended. 9 In this issue of Circulation, Idris and fellow Resuscitation Outcomes Consortium (ROC) investigators report on the relationship between chest compression rates and outcomes following out-of-hospital cardiac arrest in adults in nine North American sites. 10 The authors are to be congratulated on this large observational study, which adds valuable new data to the debate on the optimal compression rate. Compression rates were recorded by monitor-defibrillators from changes in thoracic impedance measured by defibrillation pads or from an accelerometer erom eter placed on the patient s sternum. The authors have importantly provided a precise definition for chest compression rate the actual rate used during each continuous us period of chest compressions sions within a one-minute interval independent of pauses (lasting either 2 or 3 seconds depending on which model of defibrillator-monitor was being used). The delivered chest compressions were defined as the actual number of chest compressions delivered during a one-minute interval, thus taking into account any interruptions in chest compressions. The mean chest compression rates and mean number of delivered chest compressions were determined from data collected during first 5 minutes of CPR after the monitor-defibrillator was attached. Of 15,876 patients receiving CPR, 3098 (19.5%) had analyzable CPR process data. During the 5 minutes of CPR analyzed, the mean compression rate was 112 ± 19 min -1 and the 3

mean number of delivered chest compressions was 74 ± 23. The authors did a post hoc exploratory analysis and plotted the relationship between chest compression rate and survival, and chest compression rate and ROSC on an adjusted natural cubic spline curve. With this analysis, the authors determined that compression rate was associated with ROSC (p =0.012) but not survival to discharge (p =0.63). The curve for ROSC peaks at a compression rate of 125 min - 1. When interruptions to compression were taken into account, the number of delivered compressions each minute was also associated with ROSC (p=0.01) but not with survival (p=0.25). Compared with a reference range of 75 100 delivered compressions min -1, those receiving less than 75 delivered compressions min -1 had a reduced ROSC rate (adjusted odds ratio 0.81; 95% confidence interval 0.68, 0.98; p = 0.03). The authors have identified the principle weaknesses of their study it was a retrospective analysis alys and only 20% of the treated patients had electronic ec CPR process files, and data relating to other chest compression si on variables (compression on depth, leaning [failure to allow lo the chest wall to fully recoil at the end of each compression] and duty cycle [percent ent of time the chest is compressed sed versus time allowed lowe for chest recoil]) is not reported. rted ed. 11 Despite adjustment for confounders and this being the best data available, one should question the validity of conclusions drawn from only the first 5 minutes of monitored CPR from a potentially much longer period of CPR both before or after the period analyzed. There is some selection bias because there are differences in some characteristics between the analyzed and non-analyzed cohorts (not least being the higher rate of ROSC in the analyzed cohort). Furthermore, those ROC emergency medical services (EMS) using recording defibrillator-monitors might conceivably provide CPR of higher quality compared with those not using such devices. A small, but nevertheless significant proportion (12%) of the sample studied had CPR feedback 4

technology devices enabled. This technology measures and provides real time feedback, often with prompts to rescuers, on the quality of CPR such as compression rate, depth, presence of leaning. These devices are known to influence CPR adherence with guideline recommendations but lack robust data for an impact on outcome. 12, 13 Although the authors adjusted for known factors which could influence outcome (gender, age, bystander witnessed arrest, EMS witnessed arrest, first known EMS rhythm, attempted bystander CPR, public location, and site location) it remains possible that some un-measured confounding factor (such as the EMS clinician impression of survivability) might have influenced the compression rates. Finally, this study took place when rescuers were following guidelines published in 2005. At the time of data collection, the recommended rate for chest compressions was about 100 min -1 and the recommended mend ed depth was 40-50 mm. 14 Despite the acknowledged limitations, this study is important because it demonstrates again ain that those receiving eivi fewer er delivered compressions (< 75 min -1 ), because of lower compression rates and/or more frequent interruptions, rupt are less likely to achieve ROSC. The cubic spline curve for ROSC also suggests gests that ROSC rates might decline with compression rates higher than125 min -1. What are the implications of the study findings on practice guidelines for manual CPR? Firstly, one must remember the importance of education and implementation. Studies consistently show a marked variation in CPR quality in the real world despite the content of the guidelines. 15 Indeed, the chest compression rates in the current study varied widely from the rate of 100 min -1 recommended at that time. We need to close the gap between what the guidelines say and what actually happens in practice. Recommendations have to be easily learnt, easy to remember, and easy to apply in actual cardiac arrests and not just in the classroom. 5

Next, when making recommendations for the optimal chest compression rate, the interrelationship between the rate and other chest compression variables must be considered. Human observational studies show deeper chest compressions are associated with improved shock success for terminating ventricular fibrillation, and an increase in survival to hospital admission after out-of-hospital cardiac arrest. 16-18 The impact of different chest compression rates on the other compression variables has been investigated in a randomized controlled cross-over trial using an instrumented manikin. 19 Increasing chest compression rate (range 80-160 min -1 ) during 2 minutes of continuous compressions by trained rescuers increased the number of delivered chest compressions per minute and increased the duty cycle but at a cost of a reduced chest compression depth and an increase in the proportion of compressions with leaning. This study also showed that a chest compression rate of 120 min -1 was feasible whilst maintaining an adequate chest compression depth. The inverse relationship between compression rate and depth has also been en observed during CPR following lowi out-of-hospital cardiac ac arrest. Another large study from the ROC group showed that when the chest compression rate exceeded eede d 120 min -1, most (70%) chest compressions were too shallow according to 2005 guidelines. 20 In a recent study of 133 patients requiring CPR for out-of-hospital cardiac arrest there was a clinically significant decline in chest compression depth once chest compression rates exceeded 120 min -1 (personal communication, Monsieurs KG 14 th May 2012). In the present study, compression depth data was available for only 362 (11.7%) patients but this also showed that compression depth also declined with increasing compression rate. All of these studies concerning the relationship between compression rate and depth followed the 2005 guidelines. Whether these findings hold true when 6

rescuers are asked to compress at a rate of 120 min -1 and a depth of at least 50 mm (AHA) or 50-60 mm (ERC) according to the current guidelines remains to be seen. The current study also reinforces previous evidence from the ROC group for minimizing interruptions to chest compressions. 21 Even with the correct chest compression rate, pauses during CPR will decrease dramatically the number compressions actually delivered. Friedrich Maass published his clinical observations on chest compressions 120 years ago: 'I increased the compression rate to 120. Soon a carotid pulse wave corresponding to the increased chest compression rate was palpable.' 2 The current mantra for those teaching, learning and doing chest compressions is push hard and push fast and this study provides further evidence for how fast. The sweet spot for manual chest compressions is a rate of about 120 min -1 or, to put it simply, two compressions a second. Conflict of Interest Disclosures: sure s: JPN is Editor-in-Chief in-chi of Resuscitation scit ion (honorarium orar received), e a Board Member of the European Resuscitation Council (unpaid) and a member mber of the Executive e Committee of the Resuscitation tion Council (UK) (unpaid). JS is Chair of the Resuscitation Council (UK) (unpaid), Chair of the Advanced Life Support port Working Group of the European Resuscitation scit ion Council (unpaid), Co-chair of the Advanced Life Support Task Force of the International Liaison Committee on Resuscitation tion (unpaid), and an editor of the journal Resuscitation (honorarium received). GDP is a volunteer / unpaid member of the Resuscitation Council (UK); European Resuscitation Council and International Liaison Committee on Resuscitation. He is an editor of the journal Resuscitation (honorarium received). He holds research grants relating to CPR from the National Institute of Health Research. All the authors have been involved in the local, national and international resuscitation guideline development processes and in producing learning materials. References: 1. Kouwenhoven WB, Jude JR, Knickerbocker GG. Closed-chest cardiac massage. JAMA. 1960;173:1064-1067. 2. Figl M, Pelinka LE, Mauritz W. Resuscitation great. Franz koenig and friedrich maass. Resuscitation. 2006;70:6-9. 7

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13. Hostler D, Everson-Stewart S, Rea TD, Stiell IG, Callaway CW, Kudenchuk PJ, Sears GK, Emerson SS, Nichol G. Effect of real-time feedback during cardiopulmonary resuscitation outside hospital: Prospective, cluster-randomised trial. BMJ. 2011;342:d512. 14. 2005 american heart association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care part 4: Adult basic life support. Circulation. 2005;112:IV-19-34. 15. Wik L, Kramer-Johansen J, Myklebust H, Sorebo H, Svensson L, Fellows B, Steen PA. Quality of cardiopulmonary resuscitation during out-of-hospital cardiac arrest. JAMA. 2005;293:299-304. 16. Edelson DP, Abella BS, Kramer-Johansen J, Wik L, Myklebust H, Barry AM, Merchant RM, Hoek TL, Steen PA, Becker LB. Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest. Resuscitation. 2006;71:137-145. 17. Babbs CF, Kemeny AE, Quan W, Freeman G. A new paradigm for human resuscitation research using intelligent devices. Resuscitation. 2008;77:306-315. 18. Kramer-Johansen J, Myklebust H, Wik L, Fellows B, Svensson L, Sorebo H, Steen PA. Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: A prospective interventional study. Resuscitation. 2006;71:283-292. 19. Field RA, Soar J, Davies RP, Akhtar N, Perkins GD. The impact of chest compression rates on quality of chest compressions - a manikin in study. Resuscitation. scit ion. 2012;83:360-364. 360-36 20. Stiell IG, Brown SP, Christenson J, Cheskes S, Nichol G, Powell J, Bigham B, Morrison LJ, Larsen J, Hess E, Vaillancourt C, Davis DP, Callaway awayay CW. What is the role of chest compression depth during out-of-hospital cardiac arrest rest resuscitation?*. tion Crit Care Med. 2012;40:1192-1198. 198. 21. Christenson J, Andrusiek D, Everson-Stewart S, Kudenchuk P, Hostler D, Powell J, Callaway CW, Bishop D, Vaillancourt C, Davis D, Aufderheide TP, Idris A, Stouffer JA, Stiell I, Berg R. Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation. Circulation. 2009;120:1241-1247. 9

Chest Compression Rate: Where is the Sweet Spot? Jerry P. Nolan, Gavin D. Perkins and Jasmeet Soar Circulation. published online May 23, 2012; Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231 Copyright 2012 American Heart Association, Inc. All rights reserved. Print ISSN: 0009-7322. Online ISSN: 1524-4539 The online version of this article, along with updated information and services, is located on the World Wide Web at: http://circ.ahajournals.org/content/early/2012/05/21/circulationaha.112.112722 Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published in Circulation can be obtained via RightsLink, a service of the Copyright Clearance Center, not the Editorial Office. Once the online version of the published article for which permission is being requested is located, click Request Permissions in the middle column of the Web page under Services. Further information about this process is available in the Permissions and Rights Question and Answer document. Reprints: Information about reprints can be found online at: http://www.lww.com/reprints Subscriptions: Information about subscribing to Circulation is online at: http://circ.ahajournals.org//subscriptions/