Population Based Intervention Trial of Dispatcher-Activated Neighborhood Access Defibrillation and Cardiopulmonary Resuscitation
Phase: NA
Conditions: Out of Hospital Cardiac Arrest
Sponsor: Seoul National University Hospital

Dispatcher-Activated Neighborhood Access 
Defibrillation and Cardiopulmonary Resuscitation 
 
NCT02010151 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2018.5.23 
 
 
 
 

Study setting  
In Korea, the national fire department exclusively operates the EMS system, and EMS CPR protocol 
follows the 2010 and 2015 American Heart Association (AHA) guidelines. Ambulance crews can provide 
CPR at the scene and during transport, but they cannot stop CPR in the field unless the return of 
spontaneous circulation (ROSC) occurs and cannot declare death in the field because only a physician 
can declare death. Seoul is a large metropolitan city with a single-tiered intermediate level EMS. The 
population of Seoul is approximately 10 million in an area of 605 km2. One dispatch center is 
responsible for the entire city, and a DA-CPR protocol was adopted in late 2010. Seoul is composed of 
25 administrative and health districts. each district consists of number of neighborhoods (‘town level’). 
There are average of 17 neighborhoods in each district (total 429 neighborhoods). Average population 
of districts is approximately 400,000 in an average area of 24 km2 and the average population of the 
neighborhoods is 20,000 in an average area of 1.5 km2. 
 
Intervention program 
 In May 2015, Seoul launched the TM alert system, called the dispatch-activated neighborhood access 
defibrillation and cardiopulmonary resuscitation program (“NAD-CPR” program) in 5 districts serving 
a population of 2.2 million (Gangdong-gu, Gangbuk-gu, Nowon-gu, Seocho-gu, and Jungnang-gu). The 
intervention consisted of three major components: registration of volunteers after CPR training, active 
installation and registration of a PAD, and dispatcher activation of registered volunteers for bystander 
CPR and defibrillation. 
 First, the CPR volunteer network was organized for those who agreed to register for the TM alert 
system after completing the CPR training courses provided in participating district health center. The 
CPR network was explained to the all trainee when CPR training was conducted and the trainees 
voluntarily registered themselves to the network after training. They were trained with a 1-hour CPR 
training course and received a certification card from the city mayor. The volunteers’ telephone number, 
workplace address, and home address were collected and transferred to the dispatch center to integrate 
with the EMS call system. For quality control of the CPR trainee, the volunteer registration remained 
valid for 2 years, and after that it was automatically removed. If someone want to remain in the network 
after two years, they should be attend CPR renewal course and register again. The program started in 

2013 as a pilot program and was implemented in 2014.  
Second, the Seoul health authority expanded the installation of PADs. All PADs were registered in the 
National Emergency Medical Center by the EMS Act, and the PAD registry was developed and recorded 
for use. The active installation and registration of the PADs were guided by each district’s health 
authorities at predesignated places by the EMS Act, such as public and commercial buildings, traffic 
stations, sports and cultural areas, and large-sized apartments. The city government provided half of 
the financial support for PADs, and the remainder were deployed by the private sector.  
Third, according to the DA-CPR protocol, the dispatcher asked two key questions regarding altered 
mental status and abnormal breathing. When a suspected arrest occurred, to issue an alert about an 
OHCA event, the dispatchers pushed a button to send a short text message containing the location of 
the cardiac arrest and the location of nearest available PAD to registered all volunteers within one 
geographic town according to a time window. This time window address-matched volunteers to their 
workplace or home address during the intervals from 6 AM to 22PM. The protocol for the TM alert 
service was not applied to all OHCAs, especially in cases which occurred during the time interval from 
00:00-05:59 and 22:00-23:59, because the night was regarded as an ineffective time to alert volunteers 
due to being too late.  
The dispatchers, EMS crew, registered CPR volunteers, and medical record reviewers who were 
employed to review the hospital outcomes by the Korea CDC were blinded to the study intervention.  
 
Study design  
This was a non-randomized, pre- and post-intervention trial. Since the intervention program started in 
May 2015, the period from January 2013 to December 2014 was defined as the pre-intervention period, 
and the period from January 2015 to December 2016 was defined as the post-intervention period. The 
TM cases were defined as the cases for which an TM alert was sent. Other cases were defined as standard 
care cases (non-TM cases). 
 
Study population  
We enrolled all OHCA patients with a presumed cardiac etiology who were more than 15 years old and 

who were treated by an EMS provider between January 2013 and December 2016 within the study area 
in Seoul. Those cases without an attempted resuscitation effort, cases that were witnessed by EMS 
providers or those that occurred at a nursing home or medical facility were excluded.  
 
Data collection and variables  
We collected data from the Korean OHCA Registry including the ambulance run sheet, dispatch record, 
cardiac arrest in-depth registry, and medical records for outcomes from the Korea Centers for Disease 
Control and Prevention. We developed the TM alert system registry by linking the TM cases that had a 
message sent to the registered volunteers. We checked the OHCA registry to confirm whether or not the 
case was a real arrest. Such cases were excluded if they were not a cardiac arrest or death was confirmed 
at the scene and no transfer to the emergency department (ED) occurred.  
The main exposure of interest was the intervention phase (before- and after-intervention periods), and 
the secondary exposure was TM sent from the TM alert system. Demographic factors that were collected 
included the following: date of arrest, time of the call (00:01-05:59, 06:00-11:59, 12:00-17:59, and 
18:00-23:59), age, gender, and comorbidities (diabetes, hypertension, heart disease, and stroke). 
Community and EMS factors that were collected included the following: witness information, location 
of the arrest, bystander CPR, laypersons’ use of a PAD, primary electrocardiogram (ECG) at the scene, 
EMS response time interval (RTI, from the time of the call to the time of EMS arrival at the scene), scene 
time interval (STI, from the time of arrival at the scene to the time of departure from the scene), 
transport time interval (TTI, from the time of departure from the scene to the time of EMS arrival at the 
hospital), prehospital airway management by an EMS provider (endotracheal intubation, supraglottic 
airway device, or bag valve mask). Hospital factors included the emergency department (ED) level 
(regional level 1 ED, local level 2 ED, local level 3 ED) and post-resuscitation care, such as percutaneous 
coronary intervention (PCI), targeted temperature management (TTM), and extracorporeal membrane 
oxygenation (ECMO).  
 
Main outcomes  
The primary endpoint was good neurological outcomes of OHCA patients, which were classified as 

cerebral performance category I or II at discharge. The secondary endpoints were the survival to 
discharge and prehospital ROSC. The tertiary outcomes were the provision of bystander CPR, regardless 
of dispatcher-provided CPR instructions, and bystander defibrillation.  
 
Statistical analysis  
The demographics of the registered volunteers, registered PADs, and the number of TM alerts sent 
during the study period were compared for the study setting. A descriptive analysis was performed to 
determine the distribution of the categorical variables (counts and proportions) and continuous 
variables (medians and inter-quartile ranges). The chi-square test was performed for categorical 
variables, and the Wilcoxon rank-sum test was performed to compare continuous variables across the 
intervention periods.  
Adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for bystander CPR and defibrillation by 
TM versus non-TM were calculated using multivariable logistic regression analysis with adjustment for 
potential confounders. Adjustment for age, gender, and comorbidities were included as confounders in 
Model 1, and time factors (season, weekend, and time of the arrest) and characteristics of the arrest 
(witnessed, location of arrest) in addition to the confounders in Model 1 were added in Model 2.  
Multivariable logistic regression analyses for outcomes (good CPC, survival to discharge, and PROSC) 
were used. Model 1 was adjusted for demographic factors (age, gender, and comorbidities); Model 2 
was adjusted for the demographic factors from Model 1 as well as time factors related to the event 
(season, weekday, and daytime), Utstein factors (initial ECG, witness, and place), and EMS factors (RTI, 
STI, TTI, and prehospital airway); Model 3 was adjusted for the same confounders as Models 1 and 2 as 
well as factors related to advanced hospital care (PCI, TTM, and ECMO). 
For the sensitivity analysis, a final multivariable logistic regression analysis was conducted for the 
subgroup population when the call occurred during the study time (TM sent time), from 6 AM to 10 PM. 
The confounders were same as the main analyses for each outcome. The main exposure was TM (cases 
who received TM alerts) versus non-TM (cases who did not receive TM alerts) for bystander CPR and 
defibrillation during the before- and after-intervention periods for outcomes (PROSC, survival to 
discharge, and good CPC).  

All the statistical analyses were conducted using SAS software, version 9.4 (SAS Institute Inc., Cary, NC, 
USA). P values were based on a two-sided significance level of 0.05.