bmj openfor peer review only 20/27 434 r. lowe, t. brown, j. dreyer, d. davis, a. idris, and i....

For peer review only

Temporal Trends in Out-of-hospital Cardiac Arrest Survival

Outcomes between Two Metropolitan Communities: Seoul–

Osaka Resuscitation Study

Journal: BMJ Open

Manuscript ID: bmjopen-2015-007626

Article Type: Research

Date Submitted by the Author: 11-Jan-2015

Complete List of Authors: Ro, Young Sun; Seoul National University College of Medicine, JW LEE Center for Global Medicine Shin, Sang Do; Seoul National University College of Medicine, Department

of Emergency Medicine Kitamura, Tetsuhisa; Osaka University Graduate School of Medicine, Department of Social and Environmental Medicine Lee, Eui Jung; Seoul National University College of Medicine, Department of Emergency Medicine Kajino, Kentaro; Osaka University, Department of Traumatology and Acute Critical Medicine Song, Kyoung Jun; Seoul National University College of Medicine, Department of Emergency Medicine Nishiyama, Chika; Kyoto University, Department of Critical Care Nursing Kong, So Yeon; Seoul National University Hospital Biomedical Research Institute, Laboratory of Emergency Medical Services

Sakai, Tomohiko; Osaka University, Department of Traumatology and Acute Critical Medicine Nishiuchi, Tatsuya; Kinki University, Department of Acute Medicine Hayashi, Yasuyuki; Osaka Saiseikai Senri Hospital, Senri Critical Care Medical Center Iwami, Taku ; Kyoto University , Health Service

<b>Primary Subject Heading</b>:

Epidemiology

Secondary Subject Heading: Epidemiology

Keywords: Cardiac Epidemiology < CARDIOLOGY, EPIDEMIOLOGY, ACCIDENT & EMERGENCY MEDICINE

For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml

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Temporal Trends in Out-of-hospital Cardiac Arrest Survival Outcomes between Two 1

Metropolitan Communities: Seoul–Osaka Resuscitation Study 2

3

Short title: Trends of OHCA survivals in Seoul and Osaka 4

5

Names of the authors: 6

Young Sun Ro, MD DrPH; Sang Do Shin, MD PhD; Tetsuhisa Kitamura, MD PhD; Eui Jung Lee, 7

MD; Kentaro Kajino, MD PhD; Kyoung Jun Song, MD PhD; Chika Nishiyama, RN PhD; So Yeon 8

Kong, PhD; Tomohiko Sakai, MD PhD; Tatsuya Nishiuchi, MD PhD; Yasuyuki Hayashi MD 9

PhD; Taku Iwami, MD PhD; for Seoul-Osaka Resuscitation Study (SORS) Group 10

11

Institutional affiliation of each author: 12

Young Sun Ro, MD DrPH 13

� JW LEE Center for Global Medicine, Seoul National University College of Medicine, 14

Seoul, Korea 15

� E-mail: [email protected] 16

17

Sang Do Shin, MD PhD 18

� Department of Emergency Medicine, Seoul National University College of Medicine, 19

Seoul, Korea 20


22

Tetsuhisa Kitamura, MD PhD 23

� Division of Environmental Medicine and Population Sciences, Department of Social 24

and Environmental Medicine, Osaka University Graduate School of Medicine, Suita, 25

Japan 26


28

Eui Jung Lee, MD 29

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Seoul, Korea 31


33

Kentaro Kajino, MD PhD 34

� Department of Traumatology and Acute Critical Medicine, Osaka University Graduate 35

School of Medicine, Suita, Japan 36


38

Kyoung Jun Song, MD PhD 39


Seoul, Korea 41


43

Chika Nishiyama, RN PhD 44

� Department of Pharmacoepidemiology, Kyoto University Graduate School of Medicine 45

and Public Health, Kyoto, Japan 46


48

So Yeon Kong, PhD 49

� Laboratory of Emergency Medical Services, Seoul National University Hospital 50

Biomedical Research Institute, Seoul, Korea 51


53

54

Tomohiko Sakai, MD PhD 55




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59

Tatsuya Nishiuchi, MD PhD 60

� Department of Acute Medicine, Kinki University Faculty of Medicine, Osaka-Sayama, 61

Japan 62


64

Yasuyuki Hayashi MD PhD 65

� Senri Critical Care Medical Center, Osaka Saiseikai Senri Hospital, Suita, Japan 66


68

69

Correspondence to Taku Iwami, MD, PhD, 70

Kyoto University Health Service, 71

Yoshida Honmachi, Sakyo-ku, Kyoto 606-8501, Japan. 72

Phone: +81-75-753-2401, Fax: +81-75-753-2424 73

E-mail: [email protected] 74

75

Total word count: 6,030 words (including title page, abstract, main text, acknowledgments, 76

references, figure legends, tables) 77

Total word count of Abstract: 218 words 78

Number of Figures: 2 79

Number of Tables: 5 80

Number of Appendix Tables: 2 81

82

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Funding Source and Disclosure 83

This study was supported by the Japan Pfizer Health Research Foundation and the Korea 84

Centers for Disease Control and Prevention. None of the authors has a relationship with 85

industry that requires disclosure or financial associations that might pose a conflict of interest in 86

connection with the submitted article. The authors alone are responsible for the content and 87

writing of the paper. 88

89

Study group authorship 90

Dr. Ro analysed data and wrote the paper; Dr. Shin and Dr. Iwami designed, analysed, and 91

interpreted data and revised the paper; Dr. Kitamura, Dr. Song, Dr. Lee, and Dr. Kajino 92

analysed and interpreted data and revised the paper; and Dr. Kong, Dr. Nishiyama, Dr. Sakai, 93

Dr. Nishiuchi, and Dr. Hayashi analysed data and revised the paper. 94

95

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ABSTRACT 96

97

Objectives 98

The objective of this study was to compare the temporal trends in survival after out-of-hospital 99

cardiac arrest (OHCA) between two large metropolitan communities in Asia and evaluate the 100

factors affecting survival after OHCA. 101

Design 102

A population-based prospective observational study. 103

Setting 104

The Cardiovascular Disease Surveillance (CAVAS) project in Seoul and the Utstein Osaka 105

Project in Osaka. 106

Participants 107

A total of 36,292 resuscitation-attempted OHCAs with cardiac etiology from 2006 to 2011 in 108

Seoul and Osaka (11,082 in Seoul and 25,210 in Osaka) 109

Primary outcome measures 110

Primary outcome was neurologically favorable survival. Trend analysis and multilevel analysis 111

were conducted to evaluate the temporal trends in survival and to assess the associated factors. 112

Results 113

During the study period, the overall neurologically favorable survival in resuscitation-attempted 114

OHCAs with cardiac etiology were 2.6% in Seoul and 4.6% in Osaka (p <0.01). Age and 115

gender-adjusted rates of neurologically favorable survival were significantly increased in Seoul 116

from 1.4% in 2006 to 4.3% in 2011 (adjusted rate ratio per year, 1.17; p for trend <0.01) whereas 117

no significant improvement was observed in Osaka (3.6% in 2006 and 5.1% in 2011; adjusted 118

rate ratio per year, 1.03; p for trend=0.08). 119

Conclusions 120

Increased survival after OHCA was observed in Seoul while remained constant in Osaka, 121

suggesting both the importance and limitation of improving emergency medical service (EMS) 122

systems in increasing survival after OHCA. Further intervention should be considered to 123

improve survival and surpass the limit of current EMS system. 124

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125

Key Words: Out-of-hospital cardiac arrest; Cardiopulmonary resuscitation; Epidemiology 126

127

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Strengths and limitations of this study 128

� This study demonstrated the differences in survival outcomes between two Asian 129

communities 130

� We used data from two large population-based registry of OHCA 131

� Neurologically and survival outcome in Seoul was significantly increased over the study 132

period 133

� Neurologically and survival outcome in Osaka was steady changed over the study 134

period 135

� Limitation is that information on hospital-based post-resuscitation care of OHCA that 136

might affect outcomes was not available 137

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INTRODUCTION 138

139

Out-of-hospital cardiac arrest (OHCA) is a significant global public health problem, and its 140

overall burden continues to increase [1, 2]. Despite the advances in emergency medical service 141

(EMS) systems and resuscitation technology, however, OHCA survival has not improved over 142

the past several decades leaving only a minority of patients successfully resuscitated and 143

discharged with minimal neurological impairment [2, 3]. 144

The temporal trends of survival outcomes after OHCA show variations across different 145

communities [2-8]. Some nationwide population-based studies have successfully demonstrated 146

significant improvements in the chain of survival and outcomes, while others have shown no 147

improvements over the past 20 years [3-5, 9]. A better understanding of temporal trends in 148

survival outcomes and chain of survival may corroborate evidence-based interventions toward 149

reducing the health burden of OHCA. 150

There have been several EMS-based multicenter studies on OHCAs [10-13], reflecting different 151

regional circumstances, cultural aspects, and EMS practices of participating communities. 152

Thereupon numerous reports have demonstrated considerable regional variations in 153

resuscitation outcomes of OHCA with respect to those factors. Recently, an international, 154

multicenter, prospective registry of OHCA across the Asia-Pacific region was developed with the 155

aims of generating best practice protocols for Asian EMS systems by reflecting on regional 156

characteristics and ultimately to improve OHCA survival [10, 13]. This ongoing international 157

collaboration provides standardized data across different communities and enables researchers 158

to investigate the inherent regional variations in EMS systems and OHCA outcomes [13]. 159

Understanding regional characteristics and temporal trends is critical for developing culturally 160

appropriate interventions [13-15]. 161

The purpose of this study was to compare the temporal trends in survival outcome, chain of 162

survival, and patient factors for OHCAs between two large metropolitan communities in Asia, 163

and to evaluate important factors that affect survival after OHCA, using population-based 164

registries according to the international research guidelines for OHCA. 165

166

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METHODS 167

168

The Seoul-Osaka Resuscitation Study (SORS) group is a volunteer-based collaborating study 169

group of the two communities’ research scientists in Seoul (Korea) and Osaka (Japan). This 170

study was done in those two metropolitan communities which have prospective and 171

population-based registry systems of OHCA. The study was approved by the institutional review 172

boards of the Seoul National University and Osaka University [16]. 173

174

Study setting 175

Total population was 9.6 million in Seoul (2010) and 8.8 million in Osaka (2010). The 176

population structures and EMS characteristics of the two communities are shown in Table 1. 177

In Korea, policies and laws for developing public education and training program for 178

cardiopulmonary resuscitation (CPR) were enacted in 2002, and the actual training program 179

began later in 2006 with the support of the Seoul Metropolitan Government. 180

Government-backed financial support for the supply of automatic external defibrillators (AEDs) 181

in public places became compulsory in 2008 with the Good Samaritan Law and was expanded to 182

more private places in 2012. The fund was also used to support advocacy and education for high 183

quality bystander CPR since 2008 [17]. 184

In Osaka, CPR training for citizens has been offered since 1994, and each year, approximately 185

120,000 citizens participate in conventional CPR training. Citizens gained legal permission to 186

use AED in July 2004, and public access defibrillators (PADs) have become increasingly 187

available in Osaka [9]. 188

In both communities, the EMS providers are of intermediate (EMT-I) level, and under each 189

country’s guideline, are required to continue CPR unless there is a return of spontaneous 190

circulation on the scene. Most patients with OHCA who were treated by EMS providers were 191

transported to a hospital except for those with decapitation, incineration, decomposition, rigor 192

mortis, or postmortem lividity. 193

An EMS system quality control program was initiated in 1998 in Osaka through the Utstein 194

Osaka Project, while the quality control program in Seoul was established in 2011 [8, 18, 19]. 195

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Numbers of ambulance units were 114 (2010) and 212 (2009) in Seoul and Osaka, respectively 196

(Table 1). 197

198

Study population 199

Eligible patients were resuscitation-attempted OHCA with presumed cardiac etiology between 200

January 2006 and December 2011. Resuscitation-attempted OHCAs were defined as those who 201

were attempted with any resuscitation efforts, including defibrillation by a layperson or chest 202

compression or defibrillation by EMS providers or emergency department (ED) healthcare 203

workers. Patients were identified as having an arrest of cardiac etiology by medical record 204

review. Etiology of arrest was presumed cardiac unless it was caused by cerebrovascular disease, 205

respiratory disease, malignant tumors, external factors, or any other non-cardiac etiology 206

according to the international guideline for OHCA [20]. 207

208

Data sources 209

Data were collected from the EMS run sheet in Osaka and from the EMS run sheet and hospital 210

medical record review in Seoul. The following Utstein factors were collected: age, gender, 211

etiology of arrest, place of occurrence, witness, CPR and defibrillation by bystanders, 212

prehospital initial electrocardiogram (ECG), CPR and defibrillation by EMS providers, and 213

survival outcomes. In both communities, the same definitions were used according to the 214

Utstein data report form [20] in which the details of each dataset were described in previous 215

reports [4, 8, 9, 18, 19, 21]. The elapsed time intervals such as from call to wheel arrival at scene, 216

from scene to departure to ED, from call to arrival at ED, and from call to first CPR were 217

standardized and measured in both communities. Also, time intervals from call to first 218

defibrillation of patients with initial shockable ECG were measured in both communities. The 219

time intervals from call to first CPR and from call to first defibrillation were only available in 220

2011 in Seoul. 221

222

Outcome measures 223

Primary outcome was neurologically favorable survival after OHCA with cerebral performance 224

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category 1 or 2. Secondary outcome was survival to discharge (Seoul) and 1-month survival 225

(Osaka). In Seoul, outcomes were collected by hospital medical record review performed after 226

discharge. Medical record review was done by medical record experts employed at the Korea 227

Center for Disease Controls and Prevention. In Osaka, outcomes were collected by EMS 228

providers from hospital via telephone interview or fax report. 229

230

Statistical analyses 231

Demographic characteristics of all eligible cases in the two communities were first explored. 232

Continuous and categorical variables were compared using Wilcoxon rank sum test and 233

chi-square test, respectively. To evaluate the changes in baseline characteristics, p for trend was 234

calculated by the Cochran-Armitage test. 235

To assess the factors associated with temporal trends of favorable neurological survival rates in 236

the two communities, a generalized linear mixed model approach for multilevel analysis was 237

used. Poisson distribution was used to directly estimate rate ratios (RR) instead of odds ratios to 238

avoid its potential exaggeration [22, 23]. RRs for survival outcomes and 95% confidence 239

intervals (CIs) were calculated after adjusting for the following potential confounding factors: 240

community (Seoul vs. Osaka), time (year as a continuous variable), age (elderly (≥65 years old) 241

vs. non-elderly), gender, prehospital initial ECG (shockable vs. non-shockable), place of arrest 242

(public vs. non-public), witnessed, bystander CPR, prehospital defibrillation, and short time 243

intervals from call to EMS arrival (<4 minutes) and from call to ED (<8 minutes). 244

To assess whether survival outcomes had improved over time, multivariable regression models 245

were constructed for the resuscitation attempted OHCAs of cardiac etiology. After calculation of 246

adjusted RR for each calendar year (from 2007 to 2011), we used the year 2006 as reference and 247

multiplied the adjusted RR for each year by the observed survival rate for the reference year to 248

obtain yearly risk-adjusted survival rates for the study period [23]. These rates represent the 249

estimated survival for each year if the patient case mix were identical to that in the reference 250

year [23]. We also evaluated calendar year as a continuous variable to obtain adjusted RRs for 251

year-to-year survival trends. We demonstrated the effect measures of calendar year adjusted for 252

age and gender (Model 1) and all other potential confounders (Model 2). We also examined the 253

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effects of interaction between calendar year and other potential risk factors on main outcome by 254

communities using chunk test, followed by backward elimination process for the full model 255

which included main exposure, potential risk factors, and all interaction products. Because there 256

was no statistically significant interaction product, we simply used the main exposure variable 257

and potential risks for the final model.258

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RESULTS 259

260

During the study period, there were 18,813 and 42,340 EMS-assessed OHCAs in Seoul and 261

Osaka, respectively, in which 11,082 (58.9%) in Seoul and 25,210 (59.5%) in Osaka were selected 262

for analysis as resuscitation-attempted OHCAs with cardiac etiology (Figure 1). The 263

characteristics of the patients, community, and EMS factors based on the Utstein criteria are 264

shown in Table 2. 265

The temporal trends in chain of survival (resuscitation time course) and patient factors affecting 266

outcomes after cardiac arrest are shown in Table 3. The proportion of OHCAs with initial ECG of 267

shockable rhythm was only 0.1% in 2006 but increased to 11.0% in 2011 in Seoul; whereas the 268

proportion in Osaka was 12.6% in 2006 followed by a slight decrease to 9.4% in 2011. In both 269

communities, bystander CPR rates significantly increased from 2006 to 2011 (from 0.1% to 13.1% 270

in Seoul and from 33.3% to 41.7% in Osaka). Bystander defibrillation using PAD was performed 271

in 0.4 to 1.3% of cases annually in Osaka, while only one case was observed in Seoul due to 272

initiation of the PAD program later in 2011. 273

Figure 2 shows temporal trends in survival and neurological outcomes in the two communities. 274


OHCAs with cardiac etiology were 2.6% in Seoul and 4.6% in Osaka (p <0.01); and the 276

proportions in witnessed cardiac arrests were higher as 4.0% in Seoul and 9.5% in Osaka (p 277

<0.01). From 2006 to 2011, the neurologically favorable survival in OHCAs with cardiac etiology 278

significantly increased from 1.4% to 4.0% in Seoul (p for trend <0.01), whereas no significant 279

temporal improvement was observed in Osaka (3.6% in 2006 and 4.8% in 2011; p for 280

trend=0.30). Rates of survival to discharge significantly increased in Seoul from 6.8% in 2006 281

to 10.3% in 2011 (p for trend <0.01), while no significant increase was observed in Osaka (7.2% 282

in 2006 and 7.8% in 2011; p for trend=0.90) (Figure 2A). In the subpopulation of witnessed 283

resuscitation-attempted OHCAs, similar regional trends were observed as in all OHCAs with 284

cardiac etiology; in Seoul, both survival and neurological outcome were significantly enhanced 285

while no significant increase was observed in Osaka (Figure 2B). 286

Table 4 shows patients, community, and EMS factors and their association with neurologically 287

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favorable survival. The following factors were associated with significantly better neurological 288

outcome: incidence in Osaka (vs. Seoul); age less than 65 years (vs. ≥65); initial shockable 289

rhythm (vs. non-shockable); arrest in public place (vs. private); witnessed (vs. non-witnessed); 290

defibrillation by bystanders or EMS providers; and short response and prehospital time. 291

Table 5 shows risk-adjusted temporal trends in survival outcomes in the two communities. In 292

model 1, age and gender-adjusted rates of neurologically favorable survival in 293

resuscitation-attempted OHCAs with cardiac etiology significantly increased in Seoul from 1.4% 294

in 2006 to 4.3% in 2011 (adjusted RR per year, 1.17; 95% CIs 1.09, 1.26; p for trend <0.01); while 295

no significant improvement were observed in Osaka (from 3.6% in 2006 to 5.1% in 2011; 296

adjusted RR per year, 1.03; 95% CIs 1.00, 1.07; p for trend=0.08). However, after further 297

adjustment for all potential confounders (Model 2), the significant increase in both neurological 298

and survival outcomes disappeared in Seoul. 299

In witnessed cardiac arrests, age and gender-adjusted rates of neurologically favorable survival 300

significantly increased from 1.9% to 6.9% in Seoul (adjusted RR per year, 1.21; 95% CIs 1.11, 1.32; 301

p for trend <0.01), whereas no significant change was observed in Osaka (adjusted RR per year, 302

1.03; 95% CIs 0.99, 1.07; p for trend=0.13) (Appendix table 1 and 2). 303

304

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DISCUSSION 305

306

This study demonstrated the differences in temporal trends in survival outcomes between two 307

Asian communities and their associated factors for improving survival after OHCA using data 308

from two large population-based registry of OHCA. Neurologically favorable survival in Seoul 309

was significantly increased over the study period, but still marked relatively low rates. On the 310

other hand, while showing an insignificant and steady change over the years, the overall survival 311

rates remained relatively high in Osaka. We found difficulty in improving survival after OHCA in 312

communities with already existing and developed EMS system in place, such as Osaka, 313

compared to communities with developing EMS system, such as Seoul. 314

Between 2006 and 2011, there have been substantial improvements in community level and 315

EMS system to increase survival outcomes of OHCA in Seoul. Bystander CPR education and 316

advertising campaign were diffused quickly [17], and the proportion of bystander CPR increased 317

rapidly (about 13%) within the 6-year period of this study. For EMS providers, education 318

program and quality control protocols were developed. In line with these efforts, initial ECG 319

check and application of AED by EMS providers improved from 5% in 2006 to 45% in 2011 320

(data were not shown), thereby leading to an increase in the proportion of initial shockable ECG 321

from 0.1% in 2006 to 11.0% in 2011 and defibrillation by EMS. Initial rhythms of ventricular 322

fibrillation has been previously associated with enhanced survival outcomes [2]. In Seoul, 323

median time intervals from call to initial CPR and initial defibrillation were 5 and 11 minutes, 324

respectively in 2011, which were similar to those observed in Osaka. Although resuscitation time 325

course before 2011 was not applicable in Seoul, we assume that it would have been shortened 326

during the study period. In accordance with these improvements in the chain of survival, 327

survival outcomes of OHCAs in Seoul was significantly improved throughout the study period 328

(Model 1 in Table 5). Such significance in temporal improvement was no longer observed after 329

adjustments of multiple known confounding factors (Model 2 in Table 5), which highlights the 330

need for further interventions to surpass the limit of current EMS system. 331

On the other hand, in Osaka, neurologically favorable survival did not increase during the study 332

period. Numerous efforts to improve EMS factors such as bystander CPR and prehospital 333

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defibrillation by EMS personnel had already been implemented in early 2000s in Osaka. 334

Accordingly, a previous study reported significant improvements in bystander CPR, decreased 335

time intervals from collapse to first CPR and first defibrillation, and improvements in survival 336

outcomes during 1998 and 2006 in Osaka [4]. In addition, OHCA incidence in public place 337

and bystander witnessed rates were decreased, which may have been characterized by the aging 338

society of Osaka. Despite continuous efforts in improving EMS factors and maintaining a 339

relatively good EMS system in place, the observed plateau in the survival rates of Osaka may 340

have accounted for a limit of obtainable benefits from current EMS basic-to-intermediate level. 341

Nevertheless, survival in the two metropolitan communities are still less than optimal, 342

suggesting the need to address persistent issues in EMS factors. Although the PAD program in 343

Osaka has been more readily available since 2004, the proportion of bystander defibrillation 344

still remains low that despite the 11% of OHCAs having initial shockable rhythm, only 0.9% 345

receive bystander defibrillation. While more than 300,000 PADs were distributed for use in 346

Japan, the proportion of prehospital defibrillation by layperson was still less than 3% of OHCAs 347

[9]. Further adaptation of PAD program such as distribution of neighborhood-accessible AEDs 348

and widespread deployment of home-based AEDs may save more lives, although its 349

effectiveness is still controversial. Furthermore, proportions of bystander CPR in the two Asian 350

communities were significantly lower compared to other countries such as Norway (76% for 351

resuscitation-attempted OHCA with cardiac etiology) or Sweden (59% for witnessed OHCA) [24, 352

25]. Dispatcher-assisted CPR, practice-based CPR training, and public awareness campaign to 353

promote CPR and AEDs have been shown to improve CPR and AED use by bystanders [9, 10, 17, 354

25, 26]. 355

As the quality of CPR is crucial to improve survival after OHCA, effective and efficient CPR 356

education program and EMS quality control protocols, including real-time feedback program, 357

should be considered [27, 28]. Modification of EMS protocol to improve quality of CPR on 358

ambulance during transport should also be given consideration 359

360

Limitations 361

This study has some limitations. Since this study was performed in two different metropolitan 362

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communities with basic-to-intermediate EMS service level, we cannot generalize the results to 363

communities with different EMS systems. Secondly, the outcomes in the two communities were 364

measured at different times (at discharge in Seoul and at 1 month in Osaka). Furthermore, 365

information on hospital-based post-resuscitation care of OHCA was not available, which may 366

serve as an important factor in survival outcomes. Finally, while we tried to classify he patients 367

using standardized definitions based on international guidelines [20], possible misclassification 368

may have occurred, including the definition of cardiac etiology, which can vary depending on the 369

rigor of the efforts to identify other causes. 370

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CONCLUSION 371

372

In two large metropolitan communities in Asia, the temporal trends in survival outcome and 373

associated factors for improving survival after OHCA were different. In response to 374

enhancement of chain of survival, the survival outcomes after OHCA were significantly 375

increased in Seoul, while these remained steady in Osaka despite ongoing regional efforts to 376

improve community and EMS factors. Further breakthroughs to improve survival outcomes of 377

cardiac arrest may serve to surpass the limit of current EMS system. 378

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complicating interpretation of capnography during advanced life support in cardiac 475

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care. Resuscitation, 2010. 81(4): p. 422-6. 487

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advanced life support service make a difference? Resuscitation, 2007. 74(3): p. 461-9. 491

492

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Table 1 Characteristics of population and EMS system in Seoul and Osaka

Seoul Osaka

Total population, N 9,631,482 8,776,018

Area (km2) 605 1,898

Population density (/km2) 15,914 4,624

Age, year, median (IQR) 37 (23-52) 43 (26-63)

Gender ratio (male : female) 0.96 0.93

Emergency Medical Service, number

Ambulance stations 114 212

Basic EMS providers 382 1,671

Intermittent EMS providers 347 1,204

Ambulance vehicles 117 286

Change in community/EMS effort in improving outcomes after

OHCA, year

Bystander CPR in EMS Act or fire department regulation 2002 1982

Standardization of CPR training and public support program

for CPR training for bystander and first responder 2005 1993

PAD program in EMS Act or fire department regulation 2008 2004

Quality assurance for EMS performance 2005 1998

Special continuous medical education program for EMS

providers 2007 1991

EMS: Emergency Medical Service, OHCA: Out-of-Hospital Cardiac Arrest, CPR:

Cardiopulmonary resuscitation, PAD: Public Access Defibrillator

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Table 2 Epidemiologic characteristics of resuscitation-attempted out-of hospital cardiac arrests

with cardiac etiology in Seoul and Osaka between 2006 and 2011

Seoul Osaka

p-value N % N %

Total 11,082

25,210

Gender, male 7,598 68.6 14,513 57.6 <0.01

Age, years, median (IQR) 67 (54-77) 76 (66-84) <0.01

Prehospital initial shockable ECG 750 6.8 2,772 11.0 <0.01

Place of arrest, public 2,052 18.5 3,106 12.3 <0.01

Witnessed 5,949 53.7 10,307 40.9 <0.01

Bystander CPR 723 6.5 9,907 39.3 <0.01

Bystander defibrillation 1 0.0 231 0.9 <0.01

Defibrillated by EMS 1,225 11.1 4,032 16.0 <0.01

Time interval, minute, median (IQR)

from call to EMS arrival 6 (5-8) 7 (6-9) <0.01

from scene to departure 6 (4-9) 13 (10-17) <0.01

from call to hospital arrival 20 (16-25) 27 (23-33) <0.01

from call to first CPR, n, minute† 1,684 5 (2-8) 25,148 7 (3-9) <0.01

from call to first defibrillation, n, minute†‡ 208 9 (7-12) 1,960 9 (7-12) 0.62

OHCA: Out-of-hospital Cardiac Arrest, EMS: Emergency Medical Service, CPR:

Cardiopulmonary Resuscitation, ECG: Electrocardiogram, IQR: Interquartile Range

p-value were calculated by chi-square test for category variables and Wilcoxon rank sums test

for continuous variables

†Intervals from call to first CPR or defibrillation for Seoul were available in only 2011 data.

‡Interval from call to first defibrillation was calculated for prehospital initial shockable rhythm.

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Table 3. Trend analysis of potential risk factors of resuscitation-attempted out-of hospital cardiac arrests with cardiac etiology

Seoul Osaka

2006 2007 2008 2009 2010 2011 p for trend 2006 2007 2008 2009 2010 2011 p for trend

Total, N 1,054 1,432 1,808 2,107 2,326 2,355

3,559 3,833 4,281 4,367 4,477 4,693

Gender, male, % 66.0 66.6 69.6 69.9 68.7 68.7 0.10 58.7 55.9 58.8 57.6 57.6 56.9 0.40

Age, years, median 65 66 66 66 68 69 <0.01 75 76 76 77 77 77 <0.01

Prehospital initial shockable

ECG, % 0.1 2.3 5.3 7.9 8.3 11.0 <0.01 12.6 11.4 11.7 11.0 10.3 9.4 <0.01

Place of arrest, public, % 12.5 13.6 23.9 19.6 17.5 20.1 <0.01 13.5 13.4 13.0 12.7 11.3 10.5 <0.01

Witnessed, % 58.8 55.1 55.0 54.0 51.9 51.0 <0.01 41.3 42.0 39.7 41.4 41.0 40.1 0.30

Bystander CPR, % 0.1 2.5 3.8 6.3 7.6 13.1 <0.01 33.3 38.0 39.0 42.0 40.3 41.7 <0.01

Bystander defibrillation, % 0.0 0.0 0.0 0.0 0.0 0.0 0.20 0.4 0.7 0.9 1.3 1.1 1.0 <0.01

Defibrillated by EMS, % 0.4 6.6 9.1 11.7 13.1 17.5 <0.01 17.7 17.1 17.4 16.0 14.8 13.7 <0.01

Time interval, minute, median

from call to EMS arrival 6 6 6 6 7 6 0.03 7 7 7 7 8 8 <0.01

from scene to departure 5 6 6 6 6 6 <0.01 12 13 13 13 13 13 <0.01

from call to hospital arrival 19 19 20 20 20 20 <0.01 26 27 27 28 28 28 <0.01

from call to first CPR NA NA NA NA NA 5

7 7 6 7 7 7 <0.01

from call to first defibrillation* NA NA NA NA NA 11 10 9.5 10 9 10 10 0.69

EMS: Emergency Medical Service, CPR: Cardiopulmonary Resuscitation, ECG: Electrocardiogram

*Interval from call to first defibrillation was calculated for prehospital initial shockable rhythm

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Table 4. Association between patients, community, and EMS factors and neurologically

favorable survival

Adjusted RR* 95% CI

Community, Osaka (vs. Seoul) 1.48 1.29 1.70

Time, elapse a year 1.03 1.00 1.06

Age, ≥65 years old (vs. <65 years old) 0.53 0.48 0.60

Gender, Female (vs. male) 0.90 0.79 1.02

Initial shockable ECG (vs. non-shockable) 2.38 2.02 2.81

Public place of arrest (vs. private) 1.54 1.36 1.75

Witnessed (vs. non-witnessed) 2.87 2.47 3.32

Bystander CPR 1.13 0.99 1.28

Bystander defibrillation 5.11 4.13 6.33

Defibrillated by EMS providers 2.91 2.46 3.45

Short response time interval from call to arrival EMS,

<4 min 1.50 1.20 1.87

Short transport time interval from call to hospital, <8

min 1.93 1.02 3.66

RR: Rate Ratio, ECG: Electrocardiogram, CPR: Cardiopulmonary Resuscitation, EMS:

Emergency Medical Service

*Adjusted for community, year, age, gender, initial ECG, place of arrest, witness, bystander CPR,

bystander defibrillation, EMS defibrillation, EMS response time, and prehospital time interval

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Table 5. Risk-adjusted temporal trends in survival outcomes by community

Risk-adjusted Survival Rate*, %

Adjusted Rate Ratio per Year†

p for

trend† 2006 2007 2008 2009 2010 2011 RR 95% CI Model 1‡

Good neurologic outcome

Seoul 1.4 2.5 2.5 2.5 2.4 4.3

1.17 1.09 1.26

<0.01

Osaka 3.6 5.5 4.8 5.1 4.7 5.1

1.03 1.00 1.07

0.08

Survival to discharge

Seoul 6.8 7.3 6.7 8.5 8.6 10.9

1.10 1.06 1.15

<0.01

Osaka 7.2 9.0 8.1 8.6 8.0 8.2

1.01 0.98 1.03

0.53

Model 2§


Seoul 1.4 1.9 1.4 1.3 1.2 1.6

0.99 0.91 1.08

0.85

Osaka 3.6 5.1 4.8 4.6 4.4 5.2

1.03 1.00 1.07

0.05


Seoul 6.8 6.6 4.9 6.0 5.8 6.4

1.00 0.96 1.05

0.84

Osaka 7.2 8.6 8.3 8.3 8.0 8.6

1.02 0.99 1.04

0.21

RR: rate ratio, CI: Confidence Interval

*Risk-adjusted rates for each year were obtained by multiplying the observed rate for the reference year (2006) by the corresponding rate ratios from

a model evaluating year as a categorical variable

†Adjusted rate ratios per year and p for trends were calculated with a model evaluating year as a continuous variable

‡Model 1: Adjusted for age and gender. There was no interaction.

§Model 2: Adjusted for age, gender, initial ECG, place of arrest, witness, bystander CPR, bystander defibrillation, EMS defibrillation, EMS response

time, and prehospital time interval. There was no interaction.

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Legend of Figure

Figure 1. Study flow of out-of-hospital cardiac arrest patients from January 1, 2006 to December

31, 2011. OHCA indicates out-of-hospital cardiac arrest

Figure 2. Temporal trends of survival outcomes by community for resuscitation attempted

out-of-hospital cardiac arrest with cardiac etiology (A) and witnessed cardiac arrests (B) during

the study period

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EMS-assessed OHCA N = 18,813

EMS-assessed OHCA N = 42,340

SEOUL OSAKA

Resuscitation attempted OHCA

N = 15,586

Resuscitation attempted OHCA

N = 39,005

Resuscitation not-attempted

Non-cardiac etiology

Resuscitation attempted with cardiac etiology

N = 11,082

Resuscitation attempted with cardiac etiology

N = 25,210

N = 3,335 (7.9%)

N = 13,795 (32.6%)

N = 3,227 (17.2%)

N = 4,504 (23.9%)

Not-witnessed

Witnessed N = 5,949

Witnessed N = 10,307

N = 14,903 N = 5,133

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Appendix table 1. Association between patients, community, and EMS factors and survival with

minimal neurologic impairment for witnessed OHCA

Adjusted RR* 95% CI

Region, Osaka (vs. Seoul) 1.57 1.34 1.83

Time, elapse a year 1.03 0.99 1.07

Age, ≥65 years old (vs. <65 years old) 0.53 0.47 0.60

Gender, Female (vs. male) 0.94 0.82 1.09

Initial shockable ECG (vs. non-shockable) 2.07 1.74 2.47

Public place of arrest (vs. private) 1.44 1.25 1.65

Bystander CPR 1.29 1.12 1.49

Bystander defibrillation 4.64 3.68 5.86

Defibrillated by EMS providers 2.88 2.40 3.45

Short response time interval from call to arrival EMS,

<4 min 1.54 1.21 1.97

Short transport time interval from call to hospital, <8

min 2.15 1.09 4.23

RR: Rate Ratio, ECG: Electrocardiogram, CPR: Cardiopulmonary Resuscitation, EMS:

Emergency Medical Service

*Adjusted for region, year, age, gender, initial ECG, place of arrest, bystander CPR, bystander

defibrillation, EMS defibrillation, EMS response time, and prehospital time interval

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Appendix table 2. Risk-adjusted temporal trends in survival outcomes for witnessed OHCA by communities



p for

trend† 2006 2007 2008 2009 2010 2011 RR 95% CI Model 1‡


Seoul 1.9 3.5 3.7 3.8 3.7 6.9

1.21 1.11 1.32

<0.01

Osaka 7.3 10.6 10.0 9.4 9.4 10.2

1.03 0.99 1.07

0.13


Seoul 8.1 9.8 9.1 12.4 12.8 15.5

1.14 1.08 1.19

<0.01

Osaka 13.8 16.0 16.3 15.3 15.5 15.8

1.01 0.98 1.04

0.43

Model 2§


Seoul 1.9 2.6 2.0 1.8 1.6 2.3

1.00 0.92 1.10

0.93

Osaka 7.3 10.2 9.9 8.6 8.9 10.5

1.03 0.99 1.07

0.10


Seoul 8.1 8.6 6.4 8.2 8.0 8.4

1.02 0.97 1.07

0.52

Osaka 13.8 15.7 16.5 14.8 15.3 16.5 1.02 0.99 1.05

0.23





‡Model 1: Adjusted for age and gender. There was no interaction.

§Model 2: Adjusted for age, gender, initial ECG, place of arrest, bystander CPR, bystander defibrillation, EMS defibrillation, EMS response time, and

prehospital time interval. There was no interaction.

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1

STROBE Statement—checklist of items that should be included in reports of observational studies

Item

No Recommendation

Title and abstract 1 (a) Indicate the study’s design with a commonly used term in the title or the

abstract

Y

(b) Provide in the abstract an informative and balanced summary of what was

done and what was found

Y

Introduction

Background/rationale 2 Explain the scientific background and rationale for the investigation being

reported

Y

Objectives 3 State specific objectives, including any prespecified hypotheses Y

Methods

Study design 4 Present key elements of study design early in the paper Y

Setting 5 Describe the setting, locations, and relevant dates, including periods of

recruitment, exposure, follow-up, and data collection

Y

Participants 6 (a) Cohort study—Give the eligibility criteria, and the sources and methods of

selection of participants. Describe methods of follow-up

Case-control study—Give the eligibility criteria, and the sources and methods

of case ascertainment and control selection. Give the rationale for the choice of

cases and controls

Cross-sectional study—Give the eligibility criteria, and the sources and

methods of selection of participants

Y

(b) Cohort study—For matched studies, give matching criteria and number of

exposed and unexposed

Case-control study—For matched studies, give matching criteria and the

number of controls per case

Variables 7 Clearly define all outcomes, exposures, predictors, potential confounders, and

effect modifiers. Give diagnostic criteria, if applicable

Y

Data sources/

measurement

8* For each variable of interest, give sources of data and details of methods of

assessment (measurement). Describe comparability of assessment methods if

there is more than one group

Y

Bias 9 Describe any efforts to address potential sources of bias Y

Study size 10 Explain how the study size was arrived at Y

Quantitative variables 11 Explain how quantitative variables were handled in the analyses. If applicable,

describe which groupings were chosen and why

Y

Statistical methods 12 (a) Describe all statistical methods, including those used to control for

confounding

Y

(b) Describe any methods used to examine subgroups and interactions Y

(c) Explain how missing data were addressed Y

(d) Cohort study—If applicable, explain how loss to follow-up was addressed

Case-control study—If applicable, explain how matching of cases and controls

was addressed

Cross-sectional study—If applicable, describe analytical methods taking

account of sampling strategy

Y

(e) Describe any sensitivity analyses

Continued on next page

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Results

Participants 13* (a) Report numbers of individuals at each stage of study—eg numbers potentially eligible,

examined for eligibility, confirmed eligible, included in the study, completing follow-up,

and analysed

Y

(b) Give reasons for non-participation at each stage Y

(c) Consider use of a flow diagram Y

Descriptive

data

14* (a) Give characteristics of study participants (eg demographic, clinical, social) and

information on exposures and potential confounders

Y

(b) Indicate number of participants with missing data for each variable of interest Y

(c) Cohort study—Summarise follow-up time (eg, average and total amount)

Outcome data 15* Cohort study—Report numbers of outcome events or summary measures over time Y

Case-control study—Report numbers in each exposure category, or summary measures of

exposure

Cross-sectional study—Report numbers of outcome events or summary measures

Main results 16 (a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their

precision (eg, 95% confidence interval). Make clear which confounders were adjusted for

and why they were included

Y

(b) Report category boundaries when continuous variables were categorized Y

(c) If relevant, consider translating estimates of relative risk into absolute risk for a

meaningful time period

Y

Other analyses 17 Report other analyses done—eg analyses of subgroups and interactions, and sensitivity

analyses

Y

Discussion

Key results 18 Summarise key results with reference to study objectives Y

Limitations 19 Discuss limitations of the study, taking into account sources of potential bias or

imprecision. Discuss both direction and magnitude of any potential bias

Y

Interpretation 20 Give a cautious overall interpretation of results considering objectives, limitations,

multiplicity of analyses, results from similar studies, and other relevant evidence

Y

Generalisability 21 Discuss the generalisability (external validity) of the study results Y

Other information

Funding 22 Give the source of funding and the role of the funders for the present study and, if

applicable, for the original study on which the present article is based

Y

*Give information separately for cases and controls in case-control studies and, if applicable, for exposed and

unexposed groups in cohort and cross-sectional studies.

Note: An Explanation and Elaboration article discusses each checklist item and gives methodological background and

published examples of transparent reporting. The STROBE checklist is best used in conjunction with this article (freely

available on the Web sites of PLoS Medicine at http://www.plosmedicine.org/, Annals of Internal Medicine at

http://www.annals.org/, and Epidemiology at http://www.epidem.com/). Information on the STROBE Initiative is

available at www.strobe-statement.org.

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Temporal Trends in Out-of-hospital Cardiac Arrest Survival

Outcomes between Two Metropolitan Communities: Seoul–

Osaka Resuscitation Study

Journal: BMJ Open

Manuscript ID: bmjopen-2015-007626.R1

Article Type: Research

Date Submitted by the Author: 02-Apr-2015

Complete List of Authors: Ro, Young Sun; Seoul National University Hospital Biomedical Research Institute, Laboratory of Emergency Medical Services Shin, Sang Do; Seoul National University College of Medicine, Department

of Emergency Medicine Kitamura, Tetsuhisa; Osaka University Graduate School of Medicine, Department of Social and Environmental Medicine Lee, Eui Jung; Seoul National University College of Medicine, Department of Emergency Medicine Kajino, Kentaro; Osaka University, Department of Traumatology and Acute Critical Medicine Song, Kyoung Jun; Seoul National University College of Medicine, Department of Emergency Medicine Nishiyama, Chika; Kyoto University, Department of Critical Care Nursing Kong, So Yeon; Seoul National University Hospital Biomedical Research Institute, Laboratory of Emergency Medical Services

Sakai, Tomohiko; Osaka University, Department of Traumatology and Acute Critical Medicine Nishiuchi, Tatsuya; Kinki University, Department of Acute Medicine Hayashi, Yasuyuki; Osaka Saiseikai Senri Hospital, Senri Critical Care Medical Center Iwami, Taku ; Kyoto University , Health Service

<b>Primary Subject Heading</b>:

Epidemiology

Secondary Subject Heading: Epidemiology

Keywords: Cardiac Epidemiology < CARDIOLOGY, EPIDEMIOLOGY, ACCIDENT & EMERGENCY MEDICINE


BMJ Open on F

ebruary 7, 2021 by guest. Protected by copyright.

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Temporal Trends in Out-of-hospital Cardiac Arrest Survival Outcomes between Two 1

Metropolitan Communities: Seoul–Osaka Resuscitation Study 2

3

Short title: Trends of OHCA survivals in Seoul and Osaka 4

5

Names of the authors: 6

Young Sun Ro, MD DrPH; Sang Do Shin, MD PhD; Tetsuhisa Kitamura, MD PhD; Eui Jung Lee, 7

MD; Kentaro Kajino, MD PhD; Kyoung Jun Song, MD PhD; Chika Nishiyama, RN PhD; So Yeon 8

Kong, PhD; Tomohiko Sakai, MD PhD; Tatsuya Nishiuchi, MD PhD; Yasuyuki Hayashi MD 9

PhD; Taku Iwami, MD PhD; for Seoul-Osaka Resuscitation Study (SORS) Group 10

11

Institutional affiliation of each author: 12

Young Sun Ro, MD DrPH 13




17

Sang Do Shin, MD PhD 18


Seoul, Korea 20


22

Tetsuhisa Kitamura, MD PhD 23

� Division of Environmental Medicine and Population Sciences, Department of Social 24

and Environmental Medicine, Osaka University Graduate School of Medicine, Suita, 25

Japan 26


28

Eui Jung Lee, MD 29

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Seoul, Korea 31


33

Kentaro Kajino, MD PhD 34




38

Kyoung Jun Song, MD PhD 39


Seoul, Korea 41


43

Chika Nishiyama, RN PhD 44

� Department of Pharmacoepidemiology, Kyoto University Graduate School of Medicine 45

and Public Health, Kyoto, Japan 46


48

So Yeon Kong, PhD 49




53

54

Tomohiko Sakai, MD PhD 55




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59

Tatsuya Nishiuchi, MD PhD 60

� Department of Acute Medicine, Kinki University Faculty of Medicine, Osaka-Sayama, 61

Japan 62


64

Yasuyuki Hayashi MD PhD 65

� Senri Critical Care Medical Center, Osaka Saiseikai Senri Hospital, Suita, Japan 66


68

69

Correspondence to Taku Iwami, MD, PhD, 70

Kyoto University Health Service, 71

Yoshida Honmachi, Sakyo-ku, Kyoto 606-8501, Japan. 72

Phone: +81-75-753-2401, Fax: +81-75-753-2424 73

E-mail: [email protected] 74

75

Total word count: 6,030 words (including title page, abstract, main text, acknowledgments, 76

references, figure legends, tables) 77

Total word count of Abstract: 218 words 78

Number of Figures: 2 79

Number of Tables: 5 80

Number of Appendix Tables: 2 81

82

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Funding Source and Disclosure 83

This study was supported by the Japan Pfizer Health Research Foundation and the Korea 84

Centers for Disease Control and Prevention. None of the authors has a relationship with 85

industry that requires disclosure or financial associations that might pose a conflict of interest in 86

connection with the submitted article. The authors alone are responsible for the content and 87

writing of the paper. 88

89

Study group authorship 90

Dr. Ro analysed data and wrote the paper; Dr. Shin and Dr. Iwami designed, analysed, and 91

interpreted data and revised the paper; Dr. Kitamura, Dr. Song, Dr. Lee, and Dr. Kajino 92

analysed and interpreted data and revised the paper; and Dr. Kong, Dr. Nishiyama, Dr. Sakai, 93

Dr. Nishiuchi, and Dr. Hayashi analysed data and revised the paper. 94

95

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ABSTRACT 96

97

Objectives 98

The objective of this study was to compare the temporal trends in survival after out-of-hospital 99

cardiac arrest (OHCA) between two large metropolitan communities in Asia and evaluate the 100

factors affecting survival after OHCA. 101

Design 102

A population-based prospective observational study. 103

Setting 104

The Cardiovascular Disease Surveillance (CAVAS) project in Seoul and the Utstein Osaka 105

Project in Osaka. 106

Participants 107

A total of 36,292 resuscitation-attempted OHCAs with cardiac etiology from 2006 to 2011 in 108

Seoul and Osaka (11,082 in Seoul and 25,210 in Osaka) 109

Primary outcome measures 110

Primary outcome was neurologically favorable survival. Trend analysis and multivariable 111

Poisson regression models were conducted to evaluate the temporal trends in survival of two 112

communities. 113

Results 114

During the study period, the overall neurologically favorable survival was 2.6% in Seoul and 115

4.6% in Osaka (p <0.01). In both communities, bystander CPR rates significantly increased from 116

2006 to 2011 (from 0.1% to 13.1% in Seoul and from 33.3% to 41.7% in Osaka). OHCAs 117

occurred in public places increased in Seoul (12.5% to 20.1%, p-for-trend <0.01) and 118

decreased in Osaka (13.5% to 10.5%, p-for-trend <0.01). The proportion of OHCAs 119

defibrillated by emergency medical service (EMS) providers was only 0.4% in 2006 but 120

increased to 17.5% in 2011 in Seoul, whereas the proportion in Osaka decreased from 17.7% to 121

13.7% (both p-for-trend <0.01). Age and gender-adjusted rates of neurologically favorable 122

survival were significantly increased in Seoul from 1.4% in 2006 to 4.3% in 2011 (adjusted rate 123

ratio per year, 1.17; p for trend <0.01) whereas no significant improvement was observed in 124

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Osaka (3.6% in 2006 and 5.1% in 2011; adjusted rate ratio per year, 1.03; p for trend=0.08). 125

Conclusions 126

Increased survival after OHCA was observed in Seoul while remained constant in Osaka that 127

may have been affected by the improvement of each patient, community, and EMS systems 128

factors. 129

130

Key Words: Out-of-hospital cardiac arrest; Cardiopulmonary resuscitation; Epidemiology 131

132

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Strengths and limitations of this study 133

� This study demonstrated the differences in survival outcomes between two Asian 134

communities 135

� We used data from two large population-based registry of OHCA 136

� Neurologically and survival outcome in Seoul was significantly increased over the study 137

period 138

� Neurologically and survival outcome in Osaka was steady changed over the study 139

period 140

� Limitation is that information on hospital-based post-resuscitation care of OHCA that 141

might affect outcomes was not available 142

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INTRODUCTION 143

144

Out-of-hospital cardiac arrest (OHCA) is a significant global public health problem. [1,2] 145

Despite the advances in emergency medical service (EMS) systems and resuscitation technology 146

over the past several decades, however, only a minority of OHCA patients are successfully 147

resuscitated and discharged with minimal neurological impairment. [1-4] 148

The temporal trends of survival outcomes after OHCA show variations across different 149

communities. [2,5-9] Some nationwide population-based studies have successfully 150

demonstrated significant improvements in the chain of survival and outcomes, while others 151

have shown no improvements over the past 20 years. [5,6,10] A better understanding of 152

temporal trends in survival outcomes and chain of survival may corroborate evidence-based 153

interventions toward reducing the health burden of OHCA. 154

There have been several EMS-based multicenter studies on OHCAs, [11-14] reflecting different 155

regional circumstances, cultural aspects, and EMS practices of participating communities. 156

Thereupon numerous reports have demonstrated considerable regional variations in 157

resuscitation outcomes of OHCA with respect to those factors. Recently, an international, 158

multicenter, prospective registry of OHCA across the Asia-Pacific region was developed with the 159

aims of generating best practice protocols for Asian EMS systems by reflecting on regional 160

characteristics and ultimately to improve OHCA survival. [11,14] This ongoing international 161

collaboration provides standardized data across different communities and enables researchers 162

to investigate the inherent regional variations in EMS systems and OHCA outcomes. [14] 163

Understanding regional characteristics and temporal trends is critical for developing culturally 164

appropriate interventions. [14-16] 165

The purpose of this study was to compare the temporal trends in survival outcome, chain of 166

survival, and patient factors for OHCAs between two large metropolitan communities in Asia, 167

and to evaluate important factors that affect survival after OHCA, using population-based 168

registries according to the international research guidelines for OHCA. 169

170

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METHODS 171

172

The Seoul-Osaka Resuscitation Study (SORS) group is a collaborating study group of the two 173

communities’ research scientists in Seoul (Korea) and Osaka (Japan). This study was done in 174

those two metropolitan communities which have prospective and population-based registry 175

systems of OHCA. The study was approved by the institutional review boards of the Seoul 176

National University and Osaka University. [17] 177

178

Study setting 179

Total population was 9.6 million in Seoul (2010) and 8.8 million in Osaka (2010). The 180

population structures and EMS characteristics of the two communities are shown in Table 1. 181

In Korea, policies and laws for developing public education and training program for 182

cardiopulmonary resuscitation (CPR) were enacted in 2002, and the actual training program 183

began later in 2006 with the support of the Seoul Metropolitan Government. 184

Government-backed financial support for the supply of automatic external defibrillators (AEDs) 185

in public places became compulsory in 2008 with the Good Samaritan Law and was expanded to 186

more private places in 2012. The fund was also used to support advocacy and education for high 187

quality bystander CPR since 2008. [18] 188

In Osaka, CPR training for citizens has been offered since 1994, and each year, approximately 189

120,000 citizens participate in conventional CPR training. Citizens gained legal permission to 190

use AED in July 2004, and public access defibrillators (PADs) have become increasingly 191

available in Osaka. [10] 192

In both communities, the EMS level is intermediate where the highest-qualified emergency 193

medical technicians (EMTs) can give CPR with AED, perform advanced airway management, 194

and inject intravenous fluid or drug. Under each country’s guideline, EMS providers are 195

required to continue CPR unless there is a return of spontaneous circulation on the scene. In 196

Seoul, EMS providers are encouraged to scoop and run to the emergency department (ED) while 197

giving CPR during ambulance transport as soon as possible after giving one cycle of CPR. In 198

Osaka, EMS providers are usually encouraged to stay around 10 min for interventions including 199

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three to four cycles of CPR. [17] EMS providers can withdraw provision of CPR with on-line 200

medical control when there is evident death, such as rigor mortis, postmortem lividity, 201

incineration, decomposition, or decapitation, as well as patients with ‘Do Not Resuscitate’ 202

orders. All patients with OHCA who were assessed by EMS providers were transported to an ED. 203

An EMS system quality control program was initiated in 1998 in Osaka through the Utstein 204

Osaka Project, while the quality control program in Seoul was established in 2011. [9,19,20] 205

Numbers of ambulance per square kilometer were 0.19 (2010) and 0.15 (2009) in Seoul and 206

Osaka, respectively. (Table 1) 207

208

Study population 209

Eligible patients were resuscitation-attempted OHCA with presumed cardiac etiology between 210

January 2006 and December 2011. Resuscitation-attempted OHCAs were defined as those who 211

were attempted with any resuscitation efforts, including defibrillation by a layperson or chest 212

compression or defibrillation by EMS providers or ED healthcare workers. Patients were 213

identified as having an arrest of cardiac etiology by medical record review. Etiology of arrest was 214

presumed cardiac unless it was caused by cerebrovascular disease, respiratory disease, 215

malignant tumors, external factors, or any other non-cardiac etiology according to the 216

international guideline for OHCA. [21] 217

218

Data sources 219

Data were collected from the EMS run sheet in Osaka and from the EMS run sheet and hospital 220

medical record review in Seoul. The following Utstein factors were collected: age, gender, 221

etiology of arrest, place of occurrence, witness, CPR and defibrillation by bystanders, 222

prehospital initial electrocardiogram (ECG), CPR and defibrillation by EMS providers, and 223

survival outcomes. In both communities, the same definitions were used according to the 224

Utstein data report form [21] in which the details of each dataset were described in previous 225

reports. [5,9,10,19,20,22] The elapsed time intervals such as from call to wheel arrival at scene, 226

from scene to departure to ED, from call to arrival at ED, and from call to first CPR were 227

standardized and measured in both communities. Also, time intervals from call to first 228

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defibrillation of patients with initial shockable ECG were measured in both communities. The 229

time intervals from call to first CPR and from call to first defibrillation were only available in 230

2011 in Seoul. 231

232

Outcome measures 233

Primary outcome was neurologically favorable survival after OHCA with cerebral performance 234

category 1 or 2. Secondary outcome was survival to discharge (Seoul) and 1-month survival 235

(Osaka). In Seoul, outcomes were collected by hospital medical record review performed after 236

discharge. Medical record review was done by medical record experts employed at the Korea 237

Center for Disease Controls and Prevention. In Osaka, outcomes were collected by EMS 238

providers from hospital via telephone interview or fax report. 239

240

Statistical analyses 241

Demographic characteristics of all eligible cases in the two communities were first explored. 242

Continuous and categorical variables were compared using Wilcoxon rank sum test and 243

chi-square test, respectively. To evaluate the changes in baseline characteristics, p for trend was 244

calculated by the Cochran-Armitage test. Age- and gender- standardized OHCA and survivor 245

incidence rates per 100,000 person-years for the study population were calculated to compare 246

trends by years and communities. The sum of the 2010 Census data of Seoul and Osaka by age 247

(decade) and gender was used as the standard population (direct standardization method). 248

To assess whether survival outcomes had improved over time in the two communities, a 249

multivariable Poisson regression models were constructed. Poisson distribution was used to 250

directly estimate rate ratios (RR) instead of odds ratios to avoid its potential exaggeration 251

[23,24]. RRs for survival outcomes and 95% confidence intervals (CIs) were calculated after 252

adjusting for age and gender. After calculation of adjusted RR for each calendar year (from 2007 253

to 2011), we used the year 2006 as reference and multiplied the adjusted RR for each year by the 254

observed survival rate for the reference year to obtain yearly risk-adjusted survival rates for the 255

study period [24]. These rates represent the estimated survival for each year if the patient case 256

mix were identical to that in the reference year [24]. We also evaluated calendar year as a 257

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continuous variable to obtain adjusted RRs for year-to-year survival trends. We also examined 258

the effects of interaction between calendar year and other potential risk factors on main 259

outcome by communities using chunk test, followed by backward elimination process for the full 260

model which included main exposure, potential risk factors, and all interaction products. 261

Because there was no statistically significant interaction product, we simply used the main 262

exposure variable and potential risks for the final model.263

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RESULTS 264

265

During the study period, there were 18,813 and 42,340 EMS-assessed OHCAs in Seoul and 266

Osaka, respectively, in which 11,082 (58.9%) in Seoul and 25,210 (59.5%) in Osaka were selected 267

for analysis as resuscitation-attempted OHCAs with cardiac etiology. (Figure 1) The 268

characteristics of the patients, community, and EMS factors based on the Utstein criteria are 269

shown in Table 2. 270

The temporal trends in chain of survival (resuscitation time course) and patient factors affecting 271

outcomes after cardiac arrest are shown in Table 3. The median age of patients with OHCA was 272

younger in Seoul (65 years old) than Osaka (75 years old) in 2006, and increased to 69 (Seoul) 273

and 77 years (Osaka) in 2010. The proportion of OHCAs occurred in public places increased in 274

Seoul (12.5% to 20.1%, p for trend <0.01), whereas the proportion decreased in Osaka (13.5% to 275

10.5%, p for trend <0.01). In both communities, bystander CPR rates significantly increased 276

from 2006 to 2011 (from 0.1% to 13.1% in Seoul and from 33.3% to 41.7% in Osaka). Bystander 277

defibrillation using PAD was performed in 0.4 to 1.3% of cases annually in Osaka, while only one 278

case was observed in Seoul due to initiation of the PAD program later in 2011. The proportion of 279

OHCAs defibrillated by an EMS provider was only 0.4% in 2006 but increased to 17.5% in 2011 280

in Seoul; whereas the proportion in Osaka was 17.7% in 2006 followed by a slight decrease to 281

13.7% in 2011. Age- and gender-standardized OHCA incidence rates per 100,000 person-years 282

increased in both communities during the study period from 15.4 to 37.0 in Seoul and from 30.6 283

to 39.1 in Osaka. Age- and gender-standardized survivor from OHCA rates from OHCA per 284

100,000 person-years also increased in both communities from 1.0 to 3.1 in Seoul and from 2.4 285

to 3.5 in Osaka. 286

Figure 2 shows temporal trends in survival and neurological outcomes in the two communities. 287


OHCAs with cardiac etiology were 2.6% in Seoul and 4.6% in Osaka (p <0.01); and the 289

proportions in witnessed cardiac arrests were higher as 4.0% in Seoul and 9.5% in Osaka (p 290

<0.01). From 2006 to 2011, the neurologically favorable survival in OHCAs with cardiac etiology 291

significantly increased from 1.4% to 4.0% in Seoul (p for trend <0.01), whereas no significant 292

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temporal improvement was observed in Osaka (3.6% in 2006 and 4.8% in 2011; p for 293

trend=0.30). Rates of survival to discharge significantly increased in Seoul from 6.8% in 2006 294

to 10.3% in 2011 (p for trend <0.01), while no significant increase was observed in Osaka (7.2% 295

in 2006 and 7.8% in 2011; p for trend=0.90). (Figure 2A) In the subpopulation of witnessed 296

resuscitation-attempted OHCAs, similar regional trends were observed as in all OHCAs with 297

cardiac etiology; in Seoul, both survival and neurological outcome were significantly enhanced 298

while no significant increase was observed in Osaka. (Figure 2B) 299

Table 4 shows risk-adjusted temporal trends in survival outcomes in the two communities. Age- 300

and gender-adjusted rates of neurologically favorable survival in resuscitation-attempted 301

OHCAs with cardiac etiology significantly increased in Seoul from 1.4% in 2006 to 4.3% in 2011 302

(adjusted RR per year, 1.17; 95% CIs 1.09, 1.26; p for trend <0.01); while no significant 303

improvement were observed in Osaka (from 3.6% in 2006 to 5.1% in 2011; adjusted RR per year, 304

1.03; 95% CIs 1.00, 1.07; p for trend=0.08). In witnessed cardiac arrests, age and 305

gender-adjusted rates of neurologically favorable survival significantly increased from 1.9% to 306

6.9% in Seoul (adjusted RR per year, 1.21; 95% CIs 1.11, 1.32; p for trend <0.01), whereas no 307

significant change was observed in Osaka (adjusted RR per year, 1.03; 95% CIs 0.99, 1.07; p for 308

trend=0.13). 309

310

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DISCUSSION 311

312

This study demonstrated the differences in temporal trends in survival outcomes between two 313

Asian communities and their associated factors for improving survival after OHCA using data 314

from two large population-based registry of OHCA. Neurologically favorable survival in Seoul 315

was significantly increased over the study period, but still marked relatively low rates. On the 316

other hand, while showing an insignificant and steady change over the years, the overall survival 317

rates remained relatively high in Osaka. We found difficulty in improving survival after OHCA in 318

communities with already existing and developed EMS system in place, such as Osaka, 319

compared to communities with developing EMS system, such as Seoul. 320

Between 2006 and 2011, there have been substantial improvements in community level and 321

EMS system to increase survival outcomes of OHCA in Seoul. Bystander CPR education and 322

advertising campaign were diffused quickly, [18] and the proportion of bystander CPR increased 323

rapidly (about 13%) within the 6-year period of this study. Bystander CPR can double the chance 324

of survival from an OHCA event in previous studies. [25,26] For EMS providers, education 325

program and quality control protocols were developed. In line with these efforts, initial ECG 326

check and application of AED by EMS providers improved from 5% in 2006 to 45% in 2011 327

(data were not shown), thereby leading to an increase in the proportion of initial shockable ECG 328

from 0.1% in 2006 to 11.0% in 2011 and defibrillation by EMS from 0.4% in 2006 to 17.7% in 329

2011. Initial rhythms of ventricular fibrillation has been previously associated with enhanced 330

survival outcomes. [2,27] In Seoul, median time intervals from call to initial CPR and initial 331

defibrillation were 5 and 11 minutes, respectively in 2011, which were similar to those observed 332

in Osaka. Although resuscitation time course before 2011 was not applicable in Seoul, we 333

assume that it would have been shortened during the study period. In accordance with these 334

improvements in the chain of survival, survival outcomes of OHCAs in Seoul was significantly 335

improved throughout the study period (Table 4). 336

On the other hand, in Osaka, neurologically favorable survival did not increase during the study 337

period. Numerous efforts to improve EMS factors such as bystander CPR and prehospital 338

defibrillation by EMS personnel had already been implemented in early 2000s in Osaka. 339

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Accordingly, a previous study reported significant improvements in bystander CPR, decreased 340

time intervals from collapse to first CPR and first defibrillation, and improvements in survival 341

outcomes during 1998 and 2006 in Osaka. [5] In addition, OHCA incidence in public place and 342

bystander witnessed rates were decreased, which may have been characterized by the aging 343

society of Osaka. Despite continuous efforts in improving EMS factors and maintaining a 344

relatively good EMS system in place, the observed plateau in the survival rates of Osaka may 345

have accounted for a limit of obtainable benefits from current EMS basic-to-intermediate level. 346

Nevertheless, survival in the two metropolitan communities are still less than optimal, 347

suggesting the need to address persistent issues in EMS factors. Although the PAD program in 348

Osaka has been more readily available since 2004, the proportion of bystander defibrillation 349

still remains low that despite the 11% of OHCAs having initial shockable rhythm, only 0.9% 350

receive bystander defibrillation. While more than 300,000 PADs were distributed for use in 351

Japan, the proportion of prehospital defibrillation by layperson was still less than 3% of OHCAs. 352

[10] Further adaptation of PAD program such as distribution of neighborhood-accessible AEDs 353

and widespread deployment of home-based AEDs may save more lives, although its 354

effectiveness is still controversial. Redistribution of PADs based on coverage rate of OHCA and a 355

coordinated PAD program including AED networks should also be considered. [28,29] 356

Furthermore, proportions of bystander CPR in the two Asian communities were significantly 357

lower compared to other countries such as Norway (76% for resuscitation-attempted OHCA 358

with cardiac etiology) or Sweden (59% for witnessed OHCA). [30,31] Dispatcher-assisted CPR, 359

practice-based CPR training, and public awareness campaign to promote CPR and AEDs have 360

been shown to improve CPR and AED use by bystanders. [10,11,18,26,31] 361

As the quality of CPR is crucial to improve survival after OHCA, effective and efficient CPR 362

education program and EMS quality control protocols, including real-time feedback program, 363

should be considered. [32,33] Modification of EMS protocol to improve quality of CPR on 364

ambulance during transport should also be given consideration 365

366

Limitations 367

This study has some limitations. Since this study was performed in two different metropolitan 368

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communities with basic-to-intermediate EMS service level, we cannot generalize the results to 369

communities with different EMS systems. Secondly, the outcomes in the two communities were 370

measured at different times (at discharge in Seoul and at 1 month in Osaka). Furthermore, 371

information on hospital-based post-resuscitation care of OHCA was not available, which may 372

serve as an important factor in survival outcomes. Finally, while we tried to classify he patients 373

using standardized definitions based on international guidelines, [21] possible misclassification 374

may have occurred, including the definition of cardiac etiology, which can vary depending on the 375

rigor of the efforts to identify other causes. 376

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CONCLUSION 377

378

In two large metropolitan communities in Asia, the temporal trends in survival outcome and 379

associated factors for improving survival after OHCA were different. In response to 380

enhancement of chain of survival, the survival outcomes after OHCA were significantly 381

increased in Seoul, while these remained steady in Osaka despite ongoing regional efforts to 382

improve community and EMS factors. 383

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report from the American Heart Association. Circulation 2015;131(4):e29-322. 387

2. Berdowski J, Berg RA, Tijssen JG, et al. Global incidences of out-of-hospital cardiac arrest 388

and survival rates: Systematic review of 67 prospective studies. Resuscitation 389

2010;81(11):1479-87. 390

3. Wissenberg M, Lippert FK, Folke F, et al. Association of national initiatives to improve 391

cardiac arrest management with rates of bystander intervention and patient survival 392

after out-of-hospital cardiac arrest. JAMA 2013;310(13):1377-84. 393

4. Chan PS, McNally B, Tang F, et al. Recent trends in survival from out-of-hospital cardiac 394

arrest in the United States. Circulation 2014;130(21):1876-82. 395

5. Iwami T, Nichol G, Hiraide A, et al. Continuous improvements in "chain of survival" increased 396

survival after out-of-hospital cardiac arrests: a large-scale population-based study. 397

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6. Kuisma M, Repo J, Alaspaa A. The incidence of out-of-hospital ventricular fibrillation in 399

Helsinki, Finland, from 1994 to 1999. Lancet 2001;358(9280):473-4. 400

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out-of-hospital shockable arrhythmia: bystander CPR and female gender are predictors 402

of improved outcome. Experiences from Sweden in an 18-year perspective. Heart 403

2011;97(17):1391-6. 404

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out-of-hospital cardiac arrest in Japan. Circulation 2012;126(24):2834-43. 406

9. Ro YS, Shin SD, Song KJ, et al. A trend in epidemiology and outcomes of out-of-hospital 407

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10. Kitamura T, Iwami T, Kawamura T, et al. Nationwide public-access defibrillation in Japan. N 410

Engl J Med 2010;362(11):994-1004. 411

11. Ong ME, Shin SD, Tanaka H, et al. Pan-Asian Resuscitation Outcomes Study (PAROS): 412

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journal of the Society for Academic Emergency Medicine 2011;18(8):890-7. 414

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13. Morrison LJ, Nichol G, Rea TD, et al. Rationale, development and implementation of the 418

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incidence and outcome. JAMA 2008;300(12):1423-31. 425

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Ann Emerg Med 2009;54(5):674-83 e2. 427

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outcomes: a propensity score matched analysis. Resuscitation 2012;83(3):313-9. 435

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25. Sasson C, Meischke H, Abella BS, et al. Increasing cardiopulmonary resuscitation provision 454

in communities with low bystander cardiopulmonary resuscitation rates: a science 455

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public health departments, and community leaders. Circulation 2013;127(12):1342-50. 457

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a systematic review and meta-analysis. Circ Cardiovasc Qual Outcomes 459

2010;3(1):63-81. 460

27. Soholm H, Hassager C, Lippert F, et al. Factors Associated With Successful Resuscitation 461

After Out-of-Hospital Cardiac Arrest and Temporal Trends in Survival and Comorbidity. 462

Ann Emerg Med 2014. 463

28. Hansen CM, Lippert FK, Wissenberg M, et al. Temporal trends in coverage of historical 464

cardiac arrests using a volunteer-based network of automated external defibrillators 465

accessible to laypersons and emergency dispatch centers. Circulation 466

2014;130(21):1859-67. 467

29. Folke F, Lippert FK, Nielsen SL, et al. Location of cardiac arrest in a city center: strategic 468

placement of automated external defibrillators in public locations. Circulation 469

2009;120(6):510-7. 470

30. Heradstveit BE, Sunde K, Sunde GA, et al. Factors complicating interpretation of 471

capnography during advanced life support in cardiac arrest--a clinical retrospective 472

study in 575 patients. Resuscitation 2012;83(7):813-8. 473

31. Stromsoe A, Andersson B, Ekstrom L, et al. Education in cardiopulmonary resuscitation in 474

Sweden and its clinical consequences. Resuscitation 2010;81(2):211-6. 475

32. Lund-Kordahl I, Olasveengen TM, Lorem T, et al. Improving outcome after out-of-hospital 476

cardiac arrest by strengthening weak links of the local Chain of Survival; quality of 477

advanced life support and post-resuscitation care. Resuscitation 2010;81(4):422-6. 478

33. Ma MH, Chiang WC, Ko PC, et al. Outcomes from out-of-hospital cardiac arrest in 479

Metropolitan Taipei: does an advanced life support service make a difference? 480

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Table 1 Characteristics of population and EMS system in Seoul and Osaka

Seoul Osaka

Total population, N 9,631,482 8,776,018

Area (km2) 605 1,898

Population density (/km2) 15,914 4,624

Age, year, median (IQR) 37 (23-52) 43 (26-63)

Gender ratio (male : female) 0.96 0.93

Emergency Medical Service, number

Ambulance stations 114 212

Basic EMS providers 382 1,671

Intermittent EMS providers 347 1,204

Ambulance vehicles 117 286

Change in community/EMS effort in improving outcomes after

OHCA, year

Bystander CPR in EMS Act or fire department regulation 2002 1982

Standardization of CPR training and public support program

for CPR training for bystander and first responder 2005 1993

PAD program in EMS Act or fire department regulation 2008 2004

Quality assurance for EMS performance 2005 1998

Special continuous medical education program for EMS

providers 2007 1991

EMS: Emergency Medical Service, OHCA: Out-of-Hospital Cardiac Arrest, CPR:

Cardiopulmonary resuscitation, PAD: Public Access Defibrillator

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Table 2 Epidemiologic characteristics of resuscitation-attempted out-of hospital cardiac arrests

with cardiac etiology in Seoul and Osaka between 2006 and 2011

Seoul Osaka

p-value N % N %

Total 11,082

25,210

Gender, male 7,598 68.6 14,513 57.6 <0.01

Age, years, median (IQR) 67 (54-77) 76 (66-84) <0.01

Prehospital initial shockable ECG 750 6.8 2,772 11.0 <0.01

Place of arrest, public 2,052 18.5 3,106 12.3 <0.01

Witnessed 5,949 53.7 10,307 40.9 <0.01

Bystander CPR 723 6.5 9,907 39.3 <0.01

Bystander defibrillation 1 0.0 231 0.9 <0.01

Defibrillated by EMS 1,225 11.1 4,032 16.0 <0.01

Time interval, minute, median (IQR)

from call to EMS arrival 6 (5-8) 7 (6-9) <0.01

from scene to departure 6 (4-9) 13 (10-17) <0.01

from call to hospital arrival 20 (16-25) 27 (23-33) <0.01

from call to first CPR, n, minute† 1,684 5 (2-8) 25,148 7 (3-9) <0.01

from call to first defibrillation, n, minute†‡ 208 9 (7-12) 1,960 9 (7-12) 0.62

Survival outcomes

Survival on hospital arrival 228 2.1 2,158 8.6 <0.01

Survival to discharge 909 8.2 2,004 7.9 0.48

Good neurological recovery 293 2.6 1,166 4.6 <0.01

OHCA: Out-of-hospital Cardiac Arrest, EMS: Emergency Medical Service, CPR:

Cardiopulmonary Resuscitation, ECG: Electrocardiogram, IQR: Interquartile Range

p-value were calculated by chi-square test for category variables and Wilcoxon rank sums test

for continuous variables

†Intervals from call to first CPR or defibrillation for Seoul were available in only 2011 data.

‡Interval from call to first defibrillation was calculated for prehospital initial shockable rhythm.

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Table 3. Trend analysis of potential risk factors and outcomes of resuscitation-attempted out-of hospital cardiac arrests with cardiac etiology

Seoul Osaka

2006 2007 2008 2009 2010 2011 p for trend 2006 2007 2008 2009 2010 2011 p for trend

Total, N 1,054 1,432 1,808 2,107 2,326 2,355

3,559 3,833 4,281 4,367 4,477 4,693

Gender, male, % 66.0 66.6 69.6 69.9 68.7 68.7 0.10 58.7 55.9 58.8 57.6 57.6 56.9 0.40

Age, years, median 65 66 66 66 68 69 <0.01 75 76 76 77 77 77 <0.01

Prehospital initial shockable

ECG, % 0.1 2.3 5.3 7.9 8.3 11.0 <0.01 12.6 11.4 11.7 11.0 10.3 9.4 <0.01

Place of arrest, public, % 12.5 13.6 23.9 19.6 17.5 20.1 <0.01 13.5 13.4 13.0 12.7 11.3 10.5 <0.01

Witnessed, % 58.8 55.1 55.0 54.0 51.9 51.0 <0.01 41.3 42.0 39.7 41.4 41.0 40.1 0.30

Bystander CPR, % 0.1 2.5 3.8 6.3 7.6 13.1 <0.01 33.3 38.0 39.0 42.0 40.3 41.7 <0.01

Bystander defibrillation, % 0.0 0.0 0.0 0.0 0.0 0.0 0.20 0.4 0.7 0.9 1.3 1.1 1.0 <0.01

Defibrillated by EMS, % 0.4 6.6 9.1 11.7 13.1 17.5 <0.01 17.7 17.1 17.4 16.0 14.8 13.7 <0.01

Time interval, minute, median

from call to EMS arrival 6 6 6 6 7 6 0.03 7 7 7 7 8 8 <0.01

from scene to departure 5 6 6 6 6 6 <0.01 12 13 13 13 13 13 <0.01

from call to hospital arrival 19 19 20 20 20 20 <0.01 26 27 27 28 28 28 <0.01

from call to first CPR NA NA NA NA NA 5

7 7 6 7 7 7 <0.01

from call to first defibrillation* NA NA NA NA NA 11 10 9.5 10 9 10 10 0.69

Survival outcomes

Survival on hospital arrival, n 13 21 31 47 46 70 <0.01 259 359 367 361 370 442 0.06

Survival to discharge, n 72 104 121 179 190 243 <0.01 256 335 342 363 342 366 0.90

Good neurological recovery, n 15 35 45 52 52 94 <0.01 127 204 202 213 196 224 0.30

Population measurements

Standardized incidence rate† 15.4 21.0 26.6 31.3 35.8 37.0 30.6 32.7 36.5 36.8 37.4 39.1

Standardized survivor rate† 1.0 1.3 1.4 2.2 2.5 3.1 2.4 3.2 3.2 3.5 3.2 3.5

EMS: Emergency Medical Service, CPR: Cardiopulmonary Resuscitation, ECG: Electrocardiogram

*Interval from call to first defibrillation was calculated for prehospital initial shockable rhythm

†Age- and gender-standardized OHCA and survivor incidence rates per 100,000 person per year were calculated using sum of two population by age

(decade) and gender as a standard population

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Table 4. Risk-adjusted temporal trends in survival outcomes by community



p for trend† 2006 2007 2008 2009 2010 2011 RR 95% CI Total


Seoul 1.4 2.5 2.5 2.5 2.4 4.3

1.17 1.09 1.26

<0.01

Osaka 3.6 5.5 4.8 5.1 4.7 5.1

1.03 1.00 1.07

0.08


Seoul 6.8 7.3 6.7 8.5 8.6 10.9

1.10 1.06 1.15

<0.01

Osaka 7.2 9.0 8.1 8.6 8.0 8.2

1.01 0.98 1.03

0.53

Witnessed


Seoul 1.9 3.5 3.7 3.8 3.7 6.9

1.21 1.11 1.32

<0.01

Osaka 7.3 10.6 10.0 9.4 9.4 10.2

1.03 0.99 1.07

0.13


Seoul 8.1 9.8 9.1 12.4 12.8 15.5

1.14 1.08 1.19

<0.01

Osaka 13.8 16.0 16.3 15.3 15.5 15.8

1.01 0.98 1.04

0.43


The model was adjusted for age and gender. There was no interaction.




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Legend of Figure

Figure 1. Study flow of out-of-hospital cardiac arrest patients from January 1, 2006 to December

31, 2011. OHCA indicates out-of-hospital cardiac arrest

Figure 2. Temporal trends of survival outcomes by community for resuscitation attempted

out-of-hospital cardiac arrest with cardiac etiology (A) and witnessed cardiac arrests (B) during

the study period

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1

STROBE Statement—checklist of items that should be included in reports of observational studies

Item

No Recommendation

Title and abstract 1 (a) Indicate the study’s design with a commonly used term in the title or the

abstract

Y

(b) Provide in the abstract an informative and balanced summary of what was

done and what was found

Y

Introduction

Background/rationale 2 Explain the scientific background and rationale for the investigation being

reported

Y

Objectives 3 State specific objectives, including any prespecified hypotheses Y

Methods

Study design 4 Present key elements of study design early in the paper Y

Setting 5 Describe the setting, locations, and relevant dates, including periods of

recruitment, exposure, follow-up, and data collection

Y

Participants 6 (a) Cohort study—Give the eligibility criteria, and the sources and methods of

selection of participants. Describe methods of follow-up

Case-control study—Give the eligibility criteria, and the sources and methods

of case ascertainment and control selection. Give the rationale for the choice of

cases and controls

Cross-sectional study—Give the eligibility criteria, and the sources and

methods of selection of participants

Y

(b) Cohort study—For matched studies, give matching criteria and number of

exposed and unexposed

Case-control study—For matched studies, give matching criteria and the

number of controls per case

Variables 7 Clearly define all outcomes, exposures, predictors, potential confounders, and

effect modifiers. Give diagnostic criteria, if applicable

Y

Data sources/

measurement

8* For each variable of interest, give sources of data and details of methods of

assessment (measurement). Describe comparability of assessment methods if

there is more than one group

Y

Bias 9 Describe any efforts to address potential sources of bias Y

Study size 10 Explain how the study size was arrived at Y

Quantitative variables 11 Explain how quantitative variables were handled in the analyses. If applicable,

describe which groupings were chosen and why

Y

Statistical methods 12 (a) Describe all statistical methods, including those used to control for

confounding

Y

(b) Describe any methods used to examine subgroups and interactions Y

(c) Explain how missing data were addressed Y

(d) Cohort study—If applicable, explain how loss to follow-up was addressed

Case-control study—If applicable, explain how matching of cases and controls

was addressed

Cross-sectional study—If applicable, describe analytical methods taking

account of sampling strategy

Y

(e) Describe any sensitivity analyses

Continued on next page

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Results

Participants 13* (a) Report numbers of individuals at each stage of study—eg numbers potentially eligible,

examined for eligibility, confirmed eligible, included in the study, completing follow-up,

and analysed

Y

(b) Give reasons for non-participation at each stage Y

(c) Consider use of a flow diagram Y

Descriptive

data

14* (a) Give characteristics of study participants (eg demographic, clinical, social) and

information on exposures and potential confounders

Y

(b) Indicate number of participants with missing data for each variable of interest Y

(c) Cohort study—Summarise follow-up time (eg, average and total amount)

Outcome data 15* Cohort study—Report numbers of outcome events or summary measures over time Y

Case-control study—Report numbers in each exposure category, or summary measures of

exposure

Cross-sectional study—Report numbers of outcome events or summary measures

Main results 16 (a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their

precision (eg, 95% confidence interval). Make clear which confounders were adjusted for

and why they were included

Y

(b) Report category boundaries when continuous variables were categorized Y

(c) If relevant, consider translating estimates of relative risk into absolute risk for a

meaningful time period

Y

Other analyses 17 Report other analyses done—eg analyses of subgroups and interactions, and sensitivity

analyses

Y

Discussion

Key results 18 Summarise key results with reference to study objectives Y

Limitations 19 Discuss limitations of the study, taking into account sources of potential bias or

imprecision. Discuss both direction and magnitude of any potential bias

Y

Interpretation 20 Give a cautious overall interpretation of results considering objectives, limitations,

multiplicity of analyses, results from similar studies, and other relevant evidence

Y

Generalisability 21 Discuss the generalisability (external validity) of the study results Y

Other information

Funding 22 Give the source of funding and the role of the funders for the present study and, if

applicable, for the original study on which the present article is based

Y

*Give information separately for cases and controls in case-control studies and, if applicable, for exposed and

unexposed groups in cohort and cross-sectional studies.

Note: An Explanation and Elaboration article discusses each checklist item and gives methodological background and

published examples of transparent reporting. The STROBE checklist is best used in conjunction with this article (freely

available on the Web sites of PLoS Medicine at http://www.plosmedicine.org/, Annals of Internal Medicine at

http://www.annals.org/, and Epidemiology at http://www.epidem.com/). Information on the STROBE Initiative is

available at www.strobe-statement.org.

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