复旦大学：《循证医学》课程教学资源（参考教材）Unit 07 系统综述与meta分析（主讲教师：张博恒）.pdf_大学文库

2.小组讨论 (1)Rapid critical appraisal ofa systematic review How well was the research done?-F.A.I.T.H.method Question Does the systematic review address a focused question(PICO)? What is best? Where do I find the information? The main question being addressed should be The Title, paragraph clearly stated.The expsresuchasa therapy of the Introduction should clearly state diagnostic test,and the outcome(s)of interest the question. will often be expressed in terms of a simple relationship This paper:Yes No Unclear Comment .and use it to direct the search and select articles for inclusion? What is best? Where do Ifind the information? The inclusion or exclusion of studies in a The Methods section should describe in systematic review should be clearly defined a detail the inclusion and exclusion oriori The eligibility criteria used should specify criteria Normally.this will include the he patients. ter entions or expo ures and study design. mes of in terest.In many cases the type of study design will also be a key component of the eligibility criteria. This paper:.Yes▣No▣Unclear▣ Comment FDid the search find all the relevant evidence? What is best? Where do I find the information? The starting point for comprehensive search for section should describ all relevant studies is the major bibliographic the search strategy,including the terms databases (e.g.,Medline,Cochrane,EMBASE used,in some detail.The Resulrs etc)but should also include a search of reference section will outline the number of titles lists from relevant studies,use of Science and abstracts reviewed,the number of Citation Index, and contact with experts full-text studies retrievec and the particularly to inquire about unpublished studies number of studies excluded together The search should not be limited to English with the reasons for exclusion.This language only.The search strategy should information may be presented in a include both MESH terms and text words figure of flow chart. This paper:Yes▣ No▣Unclear Comment:

2. 小组讨论 (1) Rapid critical appraisal of a systematic review How well was the research done? ----F.A.I.T.H. method Question Does the systematic review address a focused question (PICO) ? What is best? Where do I find the information? The main question being addressed should be clearly stated. The exposure, such as a therapy or diagnostic test, and the outcome(s) of interest will often be expressed in terms of a simple relationship. The Title, Abstract or final paragraph of the Introduction should clearly state the question. This paper: Yes □ No □ Unclear □ Comment: … and use it to direct the search and select articles for inclusion? What is best? Where do I find the information? The inclusion or exclusion of studies in a systematic review should be clearly defined a priori. The eligibility criteria used should specify the patients, interventions or exposures and outcomes of interest. In many cases the type of study design will also be a key component of the eligibility criteria. The Methods section should describe in detail the inclusion and exclusion criteria. Normally, this will include the study design. This paper: Yes □ No □ Unclear □ Comment: F Did the search find all the relevant evidence? What is best? Where do I find the information? The starting point for comprehensive search for all relevant studies is the major bibliographic databases (e.g., Medline, Cochrane, EMBASE, etc) but should also include a search of reference lists from relevant studies, use of Science Citation Index, and contact with experts, particularly to inquire about unpublished studies. The search should not be limited to English language only. The search strategy should include both MESH terms and text words. The Methods section should describe the search strategy, including the terms used, in some detail. The Results section will outline the number of titles and abstracts reviewed, the number of full-text studies retrieved, and the number of studies excluded together with the reasons for exclusion. This information may be presented in a figure of flow chart. This paper: Yes □ No □ Unclear □ Comment:

A Have the studies been critically appraised? What is best? Where do I find the information? The article should describe how the quality of each study was assessed using predetermined quality criteria appropriate to the type of clinical question (e.g., randomization, blinding and completeness of follow-up for intervention questions). The Methods section should describe the assessment of quality and the criteria used. This paper: Yes □ No □ Unclear □ Comment: I Did they only include high quality studies? What is best? Where do I find the information? The inclusion should only be of studies at that have low risk of bias for that question type, e.g., good RCTs for therapy, good cohorts for prognosis(“good” may include generic issues such as blinding or % follow up). The Results section should provide information on the quality of the individual studies. This paper: Yes □ No □ Unclear □ Comment: T Have the results been totaled up with appropriate summary tables and plots? What is best? Where do I find the information? The results of included studies should at least be presented in a summary table. If the results are similar, there may be a meta-analysis with the results presented in a “forest plot”. Ideally, this should also include a heterogeneity analysis. The Results section should include all the summary tables and plots and an explanation of the results This paper: Yes □ No □ Unclear □ Comment: H …and heterogeneity between studies assessed and explained? What is best? Where do I find the information? Ideally, the results of the different studies should be similar or homogeneous. If heterogeneity exists the authors may estimate whether the differences are significant (chi-square test). Possible reasons for the heterogeneity should be explored. The Results section should state whether the results are heterogeneous and discuss possible reasons. The forest plot should show the results of the chi-square test for heterogeneity and discuss reasons for heterogeneity, if present. This paper: Yes □ No □ Unclear □ Comment:

Articles 1552 www.thelancet.com Vol 376 November 6, 2010 Lancet 2010; 376: 1552–57 Published Online October 15, 2010 DOI:10.1016/S0140- 6736(10)61454-7 See Comment page 1522 Department of Anesthesiology, Critical Care and Pain Therapy, Medical University of Vienna, Vienna, Austria (M Hüpfl MD, H F Selig MD, P Nagele MD); and Department of Anesthesiology, Washington University School of Medicine, St Louis, MO, USA (P Nagele) Correspondence to: Dr Peter Nagele, Department of Anesthesiology, Washington University School of Medicine, 660 S Euclid Ave, Box 8054, St Louis, MO 63110, USA nagelep@wustl.edu Chest-compression-only versus standard cardiopulmonary resuscitation: a meta-analysis Michael Hüpfl , Harald F Selig, Peter Nagele Summary Background In out-of-hospital cardiac arrest, dispatcher-assisted chest-compression-only bystander CPR might be superior to standard bystander CPR (chest compression plus rescue ventilation), but trial fi ndings have not shown signifi cantly improved outcomes. We aimed to establish the association of chest-compression-only CPR with survival in patients with out-of-hospital cardiac arrest. Methods Medline and Embase were systematically reviewed for studies published between January, 1985, and August, 2010, in which chest-compression-only bystander CPR was compared with standard bystander CPR for adult patients with out-of-hospital cardiac arrest. In the primary meta-analysis, we included trials in which patients were randomly allocated to receive one of the two CPR techniques, according to dispatcher instructions; and in the secondary meta-analysis, we included observational cohort studies of chest-compression-only CPR. All studies had to supply survival data. The primary outcome was survival to hospital discharge. A fi xed-eff ects model was used for both meta-analyses because of an absence of heterogeneity among the studies (I²=0%). Findings In the primary meta-analysis, pooled data from three randomised trials showed that chest-compression-only CPR was associated with improved chance of survival compared with standard CPR (14% [211/1500] vs 12% [178/1531]; risk ratio 1·22, 95% CI 1·01–1·46). The absolute increase in survival was 2·4% (95% CI 0·1–4·9), and the number needed to treat was 41 (95% CI 20–1250). In the secondary meta-analysis of seven observational cohort studies, no difference was recorded between the two CPR techniques (8% [223/2731] vs 8% [863/11 152]; risk ratio 0·96, 95% CI 0·83–1·11). Interpretation For adults with out-of-hospital cardiac arrest, instructions to bystanders from emergency medical services dispatch should focus on chest-compression-only CPR. Funding US National Institutes of Health and American Heart Association. Introduction The optimal method for out-of-hospital bystander cardiopulmonary resuscitation (CPR) is controversial.1,2 Recommended standard basic life support combines chest compression and rescue ventilation.3,4 During the last decade, evidence from studies in animals5,6 and humans7–13 has questioned the usefulness of rescue ventilation during adult CPR. In these studies, chestcompression-only CPR was either equivalent or superior to standard CPR with chest compression plus rescue ventilation. However, the evidence was largely inconclusive, mostly because of the observational study design or small sample size. In a trial published in 2000, 520 patients with out-of-hospital cardiac arrest were randomly assigned to receive either dispatcher-assisted chest-compression-only or standard CPR.14 Chest-compression-only CPR was associated with a survival benefi t, although the diff erence was not signifi cant (relative diff erence 40%; absolute diff erence 4·2%, p=0·18).14 Two subsequent randomised trials reported a similar benefi t with dispatcher-assisted chest-compression-only CPR: Rea and colleagues15 recorded a 14% increase in survival to hospital discharge (1·5% absolute increase, p=0·31) in 1941 patients with cardiac arrest; and Svensson and co-workers16 reported a 24% improvement in 30-day survival (1·7% absolute increase, p=0·29) in 1276 patients with cardiac arrest. Despite results favouring chest-compression-only CPR in all three trials, assessment of which dispatcher-assisted CPR method is superior was inconclusive. Therefore, we aimed to systematically review existing evidence regarding chest-compression-only CPR and compare the fi ndings with standard CPR in a meta-analysis. In the meta-analysis, we followed the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guideline17 for randomised trials and the MOOSE (Metaanalysis Of Observational Studies in Epidemiology) guideline18 for observational cohort studies. Methods Search strategy and selection criteria We searched Medline and Embase for studies published between January, 1985, and August, 2010, with the search terms “chest compression-only”, “compression alone”, “hands-only”, and “bystander CPR”. Additionally, we manually checked the reference list of every article for further suitable studies. We considered articles published in English and German for inclusion in the analysis; despite this restriction, we did not identify studies published in any other languages

Articles www.thelancet.com Vol 376 November 6, 2010 1553 We separated the systematic review and meta-analysis into two parts: primary analysis of randomised trials, and secondary analysis of observational cohort studies. All studies that were eligible for inclusion compared chest-compression-only bystander CPR with standard bystander CPR by chest compression plus rescue ventilation, were done in adult patients with out-ofhospital cardiac arrest, and supplied survival data. In randomised trials that were eligible for inclusion, patients were randomly assigned to receive one of the two CPR techniques according to instructions from a dispatcher. Observational studies that were eligible for inclusion had a cohort design (no case series), and used an unstratifi ed cohort (eg, arrests of non-cardiac origin only). Data extraction In addition to information about study design, characteristics, and sample size, we extracted actual numbers of survivors and corresponding cohort sizes and event rates. Survival to hospital discharge was the primary outcome variable, but we also obtained outcome data on return of spontaneous circulation, 30-day survival, and favourable neurological outcome. If data for survival to hospital discharge were not available, we used 30-day survival as the primary outcome. Statistical analysis All analyses were done with Biostat Comprehensive MetaAnalysis software (version 2.2.050). Risk ratios (RR) and Figure 1: Selection of studies for the meta-analysis CPR=cardiopulmonary resuscitation. 754 records identified through database searching 74 full-text articles assessed for eligibility 682 articles excluded based on title and abstract 756 potentially relevant articles identified 10 studies included in meta-analysis 3 randomised controlled trials 7 observational cohort studies 64 full-text articles excluded because they did not report any data for chestcompression-only CPR 2 additional records identified through other sources Study design Patients receiving chestcompression-only CPR Patients receiving standard CPR Primary outcome Secondary outcome Patients with missing outcome data Randomised trials* Hallstrom et al (2000)14 Randomised 240 278 Survival to hospital discharge Admission to hospital; neurological status of survivors 2/520 (<1%) Rea et al (2010)15 Randomised 978 956 Survival to hospital discharge Favourable neurological outcome at discharge 7/1941 (<1%) Svensson et al (2010)16 Randomised 282 297 30-day survival† 1-day survival; survival to hospital discharge 0/1276 for 30-day survival; 697/1276 (55%) for survival to hospital discharge Observational cohort studies‡ Bohm et al (2007)7 Retrospective 1145 8209 Admission to hospital; 30-day survival ·· 0/11 275 Iwami et al (2007)8 Prospective 544 783 Favourable neurological outcome 1 year after cardiac arrest Return of spontaneous circulation; admission to hospital; 1-week, 30-day, and 1-year survival 25/23 436 (<1%) Olasveengen et al (2008)9 Retrospective 145 281 Survival to hospital discharge Return of spontaneous circulation; admission to hospital Not reported Ong et al (2008)10 Prospective 154 287 Survival to hospital discharge 30-day survival Not reported SOS-KANTO Study Group (2007)11 Prospective 439 712 Favourable neurological outcome 30 days after cardiac arrest 30-day survival 0/4068 Van Hoeyweghen et al (1993)12 Retrospective 263 443 Awake 14 days after CPR ·· Not reported Waalewijn et al (2001)13 Prospective 41 437 Admission to hospital; survival to hospital discharge ·· Not reported Data are number or n/N (%). CPR=cardiopulmonary resuscitation. *In randomised studies, patients and the study investigators were masked to CPR technique, but the bystander, the emergency medical services team, and the dispatcher were not. †For consistency between the three randomised trials, survival to hospital discharge was assessed in the meta-analysis, but for the primary outcome of 30-day survival in Svensson and colleagues’ study,16 54/620 (9%) patients survived in the group receiving chest-compression-only CPR and 46/656 (7%) survived in the group receiving standard CPR. ‡Data for survival to hospital discharge were used for the meta-analysis except for studies in which this information was unavailable: 30-day survival was used for Bohm and colleagues study,7 and SOS-KANTO Study Group's studies;11 1-week survival was used for Iwami and colleagues study;8 and awake after 14 days was used for Van Hoeyweghen and colleagues study.12 Table: Study characteristics

Articles 1554 www.thelancet.com Vol 376 November 6, 2010 95% CIs were calculated for every study and pooled in both fi xed-eff ects and random-eff ects models. However, the heterogeneity within the primary and secondary metaanalyses was negligible, as indicated by an I² of 0%, so we report only the results of the fi xed-eff ects model. Comprehensive Meta-Analysis software uses the inversevariance method for weighting studies; other methods can be selected, such as Mantel-Haenszel, but the results in our meta-analyses did not diff er between these methods. Heterogeneity among studies was formally assessed by the Q and I² statistics. Publication bias was tested with the Egger’s regression test. Role of the funding source Both funding organisations had no role in study design, data collection, data analysis, data interpretation, writing of the report, or the decision to submit for publication. The corresponding author had full access to all the data and had the fi nal decision to submit for publication. Results In the systematic review, we identifi ed three randomised trials that were eligible for inclusion in the primary metaanalysis (fi gure 1, table).14–16 The quality of these trials was high; all trials reported outcomes in an intention-to-treat analysis, had few missing data, and had a low rate of intervention crossovers. For the primary outcome of survival to hospital discharge, all three trials individually showed a small benefi t in patients who received chestcompression-only CPR, but the diff erences were not signifi cant (fi gure 2). Meta-analysis of these studies showed a signifi cantly increased chance of survival with chest-compression-only CPR compared with standard CPR (fi gure 2), with an absolute increase in survival of 2·4% (95% CI 0·1–4·9). The number needed to treat was 41 (95% CI 20–1250). Systematic review also identifi ed seven observational cohort studies that were eligible for the secondary metaanalysis (fi gure 1, table). Notably, of 64 observational cohort studies deemed ineligible because they did not investigate chest-compression-only CPR, none investigated dispatcher-assisted CPR. All seven studies prospectively or retrospectively investigated the association between bystander CPR technique and survival. Apart from one study,12 none of the observational studies showed a signifi cant survival diff erence between the two CPR techniques (fi gure 3). Despite our intention to use survival to hospital discharge as the primary outcome in the meta-analysis, this outcome was not reported in four studies, so instead we used 30-day survival,7,11 1-week survival,8 or awake after 14 days.12 In the meta-analysis of these studies, chest-compressiononly CPR was not associated with a diff erence in survival compared with standard CPR (fi gure 3). Furthermore, Figure 2: Primary analysis of survival to hospital discharge in randomised trials CPR=cardiopulmonary resuscitation. 0·15 0·31 0·17 0·040 1·43 1·02 1·39 2·06 1·40 (0·88–2·22) 1·14 (0·89–1·45) 1·29 (0·90–1·86) 1·22 (1·01–1·46) 35/240 (15%) 122/978 (12%) 54/282 (19%) 211/1500 (14%) 29/278 (10%) 105/956 (11%) 44/297 (15%) 178/1531 (12%) Chest-compressiononly CPR Standard CPR Hallstrom et al (2000)14 Rea et al (2010)15 Svensson et al (2010)16 Overall Risk ratio (95% CI) Z value p value Favours standard CPR Favours chest-compressiononly CPR 0·01 0·1 1 10 100 0·56 0·69 0·52 0·91 0·76 0·025 0·91 0·54 0·58 –0·39 –0·64 –0·12 0·30 –2·24 0·12 –0·61 1·07 (0·86–1·34) 0·94 (0·67–1·30) 0·83 (0·47–1·47) 0·93 (0·29–3·05) 1·06 (0·72–1·57) 0·62 (0·40–0·94) 1·05 (0·48–2·28) 0·96 (0·83–1·11) 82/1145 (7%) 52/544 (10%) 15/145 (10%) 4/154 (3%) 38/439 (9%) 26/263 (10%) 6/41 (15%) 223/2731 (8%) 550/8209 (7%) 80/783 (10%) 35/281 (12%) 8/287 (3%) 58/712 (8%) 71/443 (16%) 61/437 (14%) 863/11152 (8%) Chest-compressiononly CPR Standard CPR Bohm et al (2007)7 Iwami et al (2007)8 Olasveengen et al (2008)9 Ong et al (2008)10 SOS-KANTO Study Group (2007)11 Van Hoeyweghen et al (1993)12 Waalewijn et al (2001)13 Overall Risk ratio (95% CI) Z value p value Favours standard CPR Favours chest-compressiononly CPR 0·01 0·1 1 10 100 Figure 3: Secondary analysis of survival outcomes in observational cohort studies CPR=cardiopulmonary resuscitation

Articles www.thelancet.com Vol 376 November 6, 2010 1555 chest-compression-only CPR did not improve the rate of return of spontaneous circulation (fi gure 4). Discussion The results of this meta-analysis show that dispatcherassisted chest-compression-only bystander CPR is associated with improved survival in adults with out-of-hospital cardiac arrest compared with standard CPR (chest compression plus rescue ventilation; panel). Since meta-analyses are used to pool existing evidence, we should consider the strength of the evidence favouring chest-compression-only CPR. Despite the small number of trials included in this meta-analysis,14–16 the evidence favouring dispatcher-assisted chest-compression-only CPR seems to be robust since all randomised trials reported similar positive eff ects of this CPR technique on survival, although diff erences were not signifi cant. The pooled eff ect size of about 22% might seem small, but rates of survival after out-of-hospital cardiac arrest have been about 4–8% for the past few decades, so our result could represent important progress. The incidence of cardiac arrest is about 0·5 cases per 1000 people per year in the USA and Canada.19 Extrapolation of this number to include the USA, Canada, and the European Union (combined population of about 850 million), with an absolute increase in survival of 2% as recorded in our meta-analysis (eg, from 10% to 12%, which is equivalent to a 20% relative increase), an additional 8000 lives could be saved per year. None of the randomised trials individually showed a signifi cant improvement with dispatcher-assisted chestcompression-only CPR compared with standard CPR, which was probably because of inadequate statistical power. The fact that only three randomised trials have been done is testament to the diffi culties associated with well designed prospective studies in this setting, such as obtaining of informed consent, the little time available to randomise patients, adherence to the study protocol, tracking of patients and outcomes, and masking of investigators, study personnel, and patients from the allocated intervention. Because survival rates after out-of-hospital cardiac arrest are low and large treatment eff ects are unlikely, very large sample sizes are needed to show a signifi cant survival benefi t. No trial of chest-compression-only CPR had more than 125 events of survival in a study group, which is a fairly small number for statistical analyses. We should also address the plausibility of our fi ndings. Several independent lines of evidence support a survival benefi t associated with dispatcher-assisted chestcompression-only CPR compared with standard bystander CPR in out-of-hospital cardiac arrest. The best CPR technique for survival is a controversial issue and has been intensively discussed over the past few years,20,21 so only the most pertinent explanations will be mentioned. First, uninterrupted, high-quality chest compression is very important for successful CPR.11,22,23 Minimal hands-off time, both for lay people and healthcare professionals, is an important predictor for improved survival after cardiac arrest. By avoidance of rescue ventilation during CPR, which is often fairly time consuming for lay bystanders,24 a continuous uninterrupted coronary perfusion pressure is maintained, which increases the probability of a successful outcome.6 These considerations were the main reason to increase the compression-to-ventilation ratio for standard basic life support from 15:2 to 30:2 in the 2005 resuscitation guidelines.3,4 All three dispatcher-assisted CPR trials used the 15:2 ratio, and whether use of the 30:2 ratio would have changed the results is unclear. Second, provision of oxygenation and ventilation during the fi rst minutes after cardiac arrest, particularly witnessed cardiac arrest, might be less important than is high-quality chest compression. Third, chest-compression-only CPR is easier to teach, learn, and do than is the fairly complex standard CPR algorithm, thus increasing the probability that a bystander will intervene and provide CPR. Although our secondary meta-analysis of observational cohort studies did not show any benefi t of chest-compression-only bystander CPR compared with standard bystander CPR, these studies did not investigate dispatcher-assisted CPR. Chestcompression-only CPR had not been taught to bystanders in any of the studies; rather, the lay bystander made the deliberate decision to avoid mouthto-mouth rescue ventilation. Although our fi ndings Figure 4: Analysis of return of spontaneous circulation CPR=cardiopulmonary resuscitation. 0·99 (0·85–1·15) 0·98 (0·75–1·27) 1·05 (0·68–1·61) 0·96 (0·60–1·54) 0·99 (0·88–1·12) –0·12 –0·17 0·22 –0·16 –0·15 0·91 0·87 0·83 0·87 0·88 188/544 (35%) 53/145 (37%) 27/154 (18%) 13/41 (32%) 281/884 (32%) 273/783 (35%) 105/281 (37%) 48/287 (17%) 144/437 (33%) 570/1788 (32%) Chest-compressiononly CPR Standard CPR Iwami et al (2007)8 Olasveengen et al (2008)9 Ong et al (2008)10 Waalewijn et al (2001)13 Overall Risk ratio (95% CI) Z value p value Favours standard CPR Favours chest-compressiononly CPR 0·01 0·1 1·0 10 100

Articles 1556 www.thelancet.com Vol 376 November 6, 2010 suggest that dispatcher-assisted chest-compressiononly CPR increases survival compared with standard CPR in adults with out-of-hospital cardiac arrest, several circumstances exist in which this CPR technique might not be benefi cial. Findings from a large-scale prospective cohort study suggest that standard CPR might actually improve survival compared with chest-compression-only CPR in cardiac arrest from non-cardiac causes (eg, drowning, trauma, or asphyxia).25 Moreover, in children with out-ofhospital cardiac arrest, which is often of non-cardiac origin, standard CPR might confer a similar benefi t.26 Therefore, the benefi ts of chest-compression-only bystander CPR seem to be largest in adult patients with sudden cardiac death. Our fi ndings support the idea that emergency medical services dispatch should instruct bystanders to focus on chest-compression-only CPR in adults with out-ofhospital cardiac arrest. However, whether chestcompression-only CPR should be recommended for unassisted lay bystander CPR is unclear. Contributors MH and PN were responsible for the study concept and design, and provided administrative, technical, or material support. PN was responsible for obtaining of funding, supervision of the study, acquisition of data, and statistical analysis. All authors contributed to analysis and interpretation of data. MH and PN drafted the report, and all authors contributed to revision of the report. Confl icts of interest PN's institution has received research support from Roche Diagnostics, unrelated to this study; PN has received consultancy fees from Gerson Lehrman Group; and PN and his institution have received grants from the US National Institutes of Health and American Heart Association. MH is receiving a salary and has received payment for development of educational presentations from St John’s Ambulance Service, Vienna, Austria; and has received research support, lecture fees, and travel support from Novo Nordisk. HFS declares that he has no confl icts of interest. Acknowledgments We thank J Philipp Miller, director division of Biostatistics, Washington University School of Medicine, St Louis, MO, USA, for his statistical contributions during report preparation and revision. PN is supported by grants from the National Institute of General Medical Sciences, National Institutes of Health, and from the American Heart Association. References 1 Koster RW. Mouth-to-mouth ventilation and/or chest compression in basic life support: The debate continues. Resuscitation 2008; 77: 283–85. 2 Nolan J. Push, blow or both: is there a role for compression-only CPR? Anaesthesia 2010; 65: 771–74. 3 EEC Committee, Subcommittees and Task Forces of the American Heart Association. 2005 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation 2005; 112: IV1–203. 4 Handley AJ, Koster R, Monsieurs K, Perkins GD, Davies S, Bossaert L. European Resuscitation Council guidelines for resuscitation 2005: section 2. Adult basic life support and use of automated external defi brillators. Resuscitation 2005; 67 (suppl 1): S7–23. 5 Ewy GA, Zuercher M, Hilwig RW, et al. Improved neurological outcome with continuous chest compressions compared with 30:2 compressions-to-ventilations cardiopulmonary resuscitation in a realistic swine model of out-of-hospital cardiac arrest. Circulation 2007; 116: 2525–30. 6 Sanders AB, Kern KB, Berg RA, Hilwig RW, Heidenrich J, Ewy GA. Survival and neurologic outcome after cardiopulmonary resuscitation with four diff erent chest compression-ventilation ratios. Ann Emerg Med 2002; 40: 553–62. 7 Bohm K, Rosenqvist M, Herlitz J, Hollenberg J, Svensson L. Survival is similar after standard treatment and chest compression only in out-of-hospital bystander cardiopulmonary resuscitation. Circulation 2007; 116: 2908–12. 8 Iwami T, Kawamura T, Hiraide A, et al. Eff ectiveness of bystanderinitiated cardiac-only resuscitation for patients with out-of-hospital cardiac arrest. Circulation 2007; 116: 2900–07. 9 Olasveengen TM, Wik L, Steen PA. Standard basic life support vs. continuous chest compressions only in out-of-hospital cardiac arrest. Acta Anaesthesiol Scand 2008; 52: 914–19. 10 Ong MEH, Ng FSP, Anushia P, et al. Comparison of chest compression only and standard cardiopulmonary resuscitation for out-of-hospital cardiac arrest in Singapore. Resuscitation 2008; 78: 119–26. 11 SOS-KANTO Study Group. Cardiopulmonary resuscitation by bystanders with chest compression only (SOS-KANTO): an observational study. Lancet 2007; 369: 920–26. 12 Van Hoeyweghen RJ, Bossaert LL, Mullie A, et al. Quality and effi ciency of bystander CPR. Resuscitation 1993; 26: 47–52. 13 Waalewijn RA, Tijssen JG, Koster RW. Bystander initiated actions in out-of-hospital cardiopulmonary resuscitation: results from the Amsterdam Resuscitation Study (ARRESUST). Resuscitation 2001; 50: 273–79. 14 Hallstrom A, Cobb L, Johnson E, Copass M. Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation. N Engl J Med 2000; 342: 1546–53. 15 Rea TD, Fahrenbruch C, Culley L, et al. CPR with chest compression alone or with rescue breathing. N Engl J Med 2010; 363: 423–33. 16 Svensson L, Bohm K, Castrèn M, et al. Compression-only CPR or standard CPR in out-of-hospital cardiac arrest. N Engl J Med 2010; 363: 434–42. 17 Moher D, Liberati A, Tetzlaff J, Altman DG, and the PRISMA Group. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Ann Intern Med 2009; 151: 264–69. 18 Stroup DF, Berlin JA, Morton SC, et al. Meta-analysis of observational studies in epidemiology: a proposal for reporting. JAMA 2000; 283: 2008–12. 19 Nichol G, Thomas E, Callaway CW, et al. Regional variation in out-of-hospital cardiac arrest incidence and outcome. JAMA 2008; 300: 1423–31. 20 Ewy GA. Continuous-chest-compression cardiopulmonary resuscitation for cardiac arrest. Circulation 2007; 116: 2894–96. 21 Gold LS, Eisenberg M. Chest-compression-only vs. standard cardiopulmonary resuscitation: shouldn’t we wait for more evidence? Prehosp Emerg Care 2008; 12: 406–09. Panel: Research in context Systematic review For this article, a rigorous search strategy was used to identify all clinical trials that prospectively randomised adults with out-of-hospital cardiac arrest to receive dispatcher-assisted chest-compression-only or standard CPR (including rescue ventilation), and all observational studies that distinguished between chest-compression-only and standard CPR in adults with out-of-hospital cardiac arrest. Interpretation Dispatcher-assisted chest-compression-only bystander CPR is associated with a 22% improved survival rate in adults with out-of-hospital cardiac arrest compared with standard CPR. CPR=cardiopulmonary resuscitation