INTRODUCTION
Out-of-hospital cardiac arrest (OHCA) is a major public health concern and one of the most life-threatening emergencies. The survival-to-discharge rate for OHCA patients has been reported at only 2% to 11% [1], a figure that varies with geography and the efficiency of the response system. The American Heart Association has emphasized the importance of an effective response system, known as the chain of survival [2]. Recent evidence suggests that not all links in this chain contribute equally to outcomes [3]. The first two links—promptly calling for help and rapidly initiating chest compressions—have been shown to improve survival more than other factors.
However, most OHCA events occur at home or in public places [4], where medical providers are not typically present to perform cardiopulmonary resuscitation (CPR). In such situations, community members are required to provide bystander CPR. International literature has emphasized the importance of bystander CPR, leading to expanded efforts in public CPR education [5]. In addition to broad CPR training, several projects have recruited and trained community first responder (CFR) volunteers to initiate CPR before ambulance arrival [6-12]. More recently, activation systems have been implemented to alert nearby CFRs when suspected cardiac arrest cases are reported, aiming to increase bystander CPR and survival rates.
A Swedish randomized controlled trial demonstrated that activating CFRs during OHCA significantly increased bystander CPR compared with controls [13]. Similarly, in the Netherlands, CFR system implementation increased bystander CPR rates from 78% to 91% and improved survival to discharge from 26% to 39% [14]. Although these findings highlight the potential of CFR systems, challenges remain, particularly regarding CFR response rates. Studies in developed countries such as Australia, New Zealand [15], and Singapore [16] have shown that CFRs respond to about one-fourth of OHCA activations, with only 14% assisting in resuscitation. To our knowledge, little evidence is available on CFR response in developing countries.
In Thailand, CFR systems are not yet nationwide. Only a few emergency medical services (EMS) agencies have piloted CFR programs [17,18], and no published data exist on the Thai CFR notification system. The Siriraj Emergency Medical Service (SiEMS) Center launched a CFR program in 2022, using a social media application for activation. The system became operational for real OHCA cases in early 2023. The project involved training CFRs, setting up the activation mechanism, and auditing the response system. After implementation, this study aimed to assess the effectiveness of the CFR program, focusing on response rates and the proportion of CFRs arriving before ambulances. The study also sought to identify factors that promote CFR response as well as barriers to participation in real OHCA events.
METHODS
Study design
This was a prospective observational study that utilized data from SiEMS, covering OHCA patients resuscitated between August 2023 and December 2024. In addition, a telephone survey was conducted to identify promoting factors and barriers influencing CFR response to the scene.
Setting
SiEMS operates as an advanced life support (ALS) unit within the Bangkok-Noi district of the Bangkok EMS system, covering an area of 12 km² [19] with a population of 99,729 [20]. The service responds to more than 1,800 emergency incidents annually, of which approximately 200 involve OHCA patients. The Bangkok dispatch system can be accessed through hotline number 1,669 and is managed by the Bangkok Emergency Medical Center (Erawan Center). It deploys both basic life support and ALS units using a two-tiered Criteria Based Dispatch system [21]. When a call is received, SiEMS staff enter standard data into the Smart EMS system, which sends an SMS link to the caller for GPS location sharing. If GPS data cannot be obtained, callers may enter the location manually. The SiEMS coordinator provides telephone instructions for pre-arrival CPR and identifies nearby CFRs, notifying them through the social media platform LINE (Line Corporation) based on geographic proximity.
CFR program in this study
The CFR program was promoted through the Siriraj EMS Center’s social media platform and included individuals aged 18 years and older. Training consisted of a 3-hour hands-only CPR session, testing, and practice with the activation system. All 90 trained CFRs provided informed consent during the training session. The CFR density in the study population was 9 per 10,000 residents. Participants registered predefined locations in the platform; real-time location tracking was not utilized. Notifications were restricted to the period between 06:00 and 24:00 for convenience and safety at night. CFRs were activated in cases of suspected cardiac arrest or altered consciousness with uncertain breathing within a 500-m radius of their registered location.
Inclusion and exclusion criteria for OHCA patients
The study included patients aged 18 years or older attended by SiEMS. Exclusion criteria were traumatic causes, lack of consent from relatives, inaccessible cases, or inability to obtain consent. Consent forms were obtained after resuscitation, either at the scene or in the emergency department. Study approval was granted by the Siriraj Institutional Review Board (SiIRB) under protocol no. 420/2566 (IRB2).
Data collection system
Data on patient characteristics, community response processes, and prehospital OHCA management were recorded on study forms by on-duty paramedics and nurses after consent was obtained. The case record form followed the Utstein template for OHCA documentation [22]. Variables collected included patient age, sex, date and time of call, dispatch, and arrival, location type, OHCA witness status, performance of bystander CPR, automated external defibrillator (AED) use, initial rhythm, and prehospital management. EMS response time was defined as the interval between the time the call was received by the Bangkok Dispatch Center and EMS arrival at the scene. Scene time was defined as the period between EMS arrival at the patient’s location and departure from the scene. CFR-related data included the number of CFRs notified, the number accepting the notification, and the number arriving at the scene before EMS. Weekly reviews of OHCA cases were conducted to validate data quality. A telephone survey was administered to CFRs notified of an event within 72 hours, focusing on barriers to response. In addition, investigators extracted emergency department management and hospital outcome data from electronic medical records. Return of spontaneous circulation (ROSC) was defined as a sustained palpable pulse lasting more than 20 minutes [22].
Data analysis
Based on prior evidence, we expected the CFR notification acceptance rate in the first year of implementation to be 10% [16]. With a precision level of 0.0725, the estimated sample size was 66 OHCA cases with CFR notification. Acceptance and response rates were reported with 95% confidence intervals. Analyses were conducted using SPSS Statistics version 18 (IBM Corp.), with statistical significance defined as P<0.05.
RESULTS
During the study period (August 2023 to December 2024), SiEMS resuscitated 381 OHCA patients. CFRs were activated in 67 patients (17.6% of total OHCA cases included in the CFR activation system), while 314 patients (82.4%) did not undergo CFR activation. Among these 314 patients, 110 cases (35.0%) occurred outside the CFR activation timeframe, whereas 204 cases (65.0%) had no documented reason for non-activation. The data flow of the study is illustrated in Fig. 1.
Table 1 presents the characteristics of OHCA patients with activated CFRs. In this group, 55.2% were male, 27.8% had heart disease as an underlying condition, 61.5% received bystander CPR, and 7.5% had public AED use. Additionally, 27.3% achieved prehospital ROSC, 12.5% survived to hospital admission following cardiac arrest, and only 1.6% survived to hospital discharge.
The CFR activation system alerted responders in 67 OHCA cases, with a median of 3 CFRs notified per case (Table 2). Among these, 12 patients had CFRs who accepted the notification (20.3%). Of those, 11 CFRs arrived at the scene and either provided first aid or assisted the EMS team (18.6%). Only three CFRs reached the scene before EMS arrival and participated in resuscitation (5.1%).
Of the 90 trained CFRs, 46 were activated and later responded to the survey. Among these, only seven CFRs accepted the notification and responded at the scene. Among survey respondents, 60.1% were male. Education levels were as follows: 21.7% had completed intermediate school, 28.3% secondary school, and 50% held a bachelor’s degree or higher. Employment status showed that 2.2% were unemployed or retired, 84.8% were non-medical office workers, and 13.0% were medical personnel. Regarding CPR experience, 34.8% had performed CPR more than five times, 28.2% had performed CPR 2–5 times, 10.9% had performed CPR once, and 26.1% had never performed CPR on real patients. Table 3 summarizes the characteristics of CFRs who were activated and responded to the survey.
Across the 67 OHCA patients with CFR activation, the system generated 300 notifications. A total of 187 survey responses were received (62.3% response rate). Among respondents, 35.3% reported not seeing the notification. The most common reason was inability to access their phones at the time (40.9%). Of the 64.7% who did see the notifications, 90.1% either did not respond or declined due to being too far from the scene (55.0%) or being unavailable because of work obligations (43.1%). Fig. 2 illustrates survey responses, while Fig. 3 presents reasons for not seeing the notifications.
DISCUSSION
This study identified the response rate of the CFR notification system for OHCA patients within the SiEMS coverage area. Of all notified cases, 20.3% were accepted, and 18.6% of CFRs arrived at the scene. Only 5.1% of CFRs arrived before ambulance personnel and supported the ALS team in resuscitating OHCA patients. To our knowledge, this is the first study in Thailand to report barriers preventing CFRs from responding to the scene.
The response rate of our CFR notification system differed from those in other countries, likely due to several factors, including the notification system used, the number of CFRs, geographic conditions, and economic constraints. In our study, only 20.3% of OHCA cases had CFRs who accepted the notification. By comparison, in Singapore, 11% of OHCA cases had CFR acceptance in 2015, which rose to 43% in 2019. This improvement was attributed to Singapore’s adoption of the “myResponder” mobile application in 2015, which incorporated real-time GPS tracking to activate CFRs [16]. In contrast, our system relied on LINE Official to send notifications, using GPS only during initial registration to determine CFR location [23]. Consequently, the actual location of CFRs at the time of an OHCA often differed from their registered location, which survey results confirmed as a major barrier: 55% of CFRs saw the notification but did not respond because they were too far from the scene. Real-time GPS activation is clearly more accurate, though it requires higher maintenance costs. Singapore allocated significant resources to develop and sustain its mobile app. In Thailand, the cost-effectiveness of such a system was not considered sufficient to justify its use, which led to reliance on LINE Official. Additionally, Singapore recruited a far larger pool of CFRs (9 CFRs per 10,000 population in our study vs. 80 CFRs per 10,000 in Singapore by 2019). This was possible because Singapore did not require CPR training prior to registration, which increased app installations and registered responders. By 2019, Singapore had 47,000 registered CFRs, a major factor contributing to higher notification acceptance rates.
Sweden offers another example. Its CFR notification system, “SMS-lifesaver,” was introduced in 2008. A randomized controlled trial conducted between 2012 and 2013 in Stockholm County (6,519 km², population 2.3 million) activated CFRs via telephone and SMS [13]. Recruitment campaigns and CPR training courses initially registered 5,989 CFRs (26 per 10,000 population), increasing to 9,828 (43 per 10,000) by the trial’s end. This expansion resulted in a 61.6% CFR response rate [13], far higher than the 20.3% observed in our study. In comparison, our CFR program included only 90 volunteers, covering 12 km² with a population of 99,729 (9 CFRs per 10,000). These findings underscore that the number of CFRs is a key determinant of system response. Given that this is the first CFR study in Thailand with a relatively small sample of responders, we recommend that future programs aim to recruit at least 20 CFRs per 10,000 population within the coverage area to achieve a more acceptable response rate.
This study also found that only three CFRs arrived before the ambulance, which may be explained by limitations in system design. Specifically, our CFR notification process was not integrated with the dispatch center. Instead, CFRs were notified from the ambulance station, and the coordinator manually activated them based on distance and protocol. This manual step may have delayed notification. By contrast, the Singaporean and Swedish systems automatically activated CFRs according to real-time proximity [13,16]. This automation allowed more responders to arrive before the ambulance. For future development, we recommend upgrading the CFR system to be automatic and fully integrated with the dispatch center to minimize delays and improve early response rates.
Our study asked CFRs who did not receive notifications about the factors preventing them from doing so. The most common reason was the inability to access a telephone at the time, due to circumstances such as working hours or being in a car. The second reason was that CFRs did not hear or see the notification. These findings were consistent with studies from the United States and New Zealand, where common reasons for not seeing alerts included phones being muted, not hearing the signal, or being away from the device [7,15]. This issue arose in our system because notifications were sent through LINE Official, which required internet access and enabled phone notifications. If either was disabled, CFRs did not receive alerts. From the CFRs’ perspective, keeping mobile internet and notifications active at all times could intrude on privacy, increase data usage, and drain battery life, creating inconvenience for volunteers.
The investigators also surveyed barriers that prevented CFRs from responding and arriving at the scene. The results were consistent with findings from the United States, New Zealand, and Sweden. The most frequently cited reasons for not responding to alerts were work obligations, family or childcare responsibilities, and being located too far from the incident [7,15,24]. The primary barriers were therefore distance to the scene and the availability of CFRs. As noted earlier, our notification system initially included all CFRs within a 500-m radius of the scene. However, during the study period, many CFRs reported being too far away when the notification was received. This occurred because CFRs were often not present at their registered locations, as our system did not employ real-time GPS tracking but instead relied on self-reported locations. Although real-time GPS tracking could provide greater accuracy, it involves higher maintenance costs and raises potential privacy concerns. These considerations were the main reason our study used the LINE Official account to send notifications.
This study represents the first report on CFR response rates and barriers in Thailand. Overall, the data obtained can guide future projects in several ways. Our findings suggest that the program is feasible, with an acceptable initial response rate compared with prior studies. Adjustments to the workflow, such as expanding activation times, modifying distance thresholds, or refining the notification system, could further improve both response rates and response times. We also recommend increasing CFR recruitment. Additional validation studies and further investigations are warranted to support future implementation.
Limitations
This study has several limitations. First, it involved a small number of CFRs and OHCA cases, which may limit the validity and generalizability of the results. As noted above, continuous recruitment of CFRs will be important for expanding the dataset. Second, the system operated only between 06:00 and 24:00 for safety reasons; therefore, results may not reflect performance in a 24-hour system. Third, CFR activation was not automated but depended on personnel primarily assigned to ALS operations. This manual process may have delayed notifications, and some eligible cases may not have triggered alerts. Non-activation may also have occurred when no CFRs were located within 500 meters or when manual activation steps placed additional burdens on the coordinator. Further evaluation of non-activation causes is needed to improve system responsiveness. Fourth, the survey of CFRs was conducted by direct telephone interview, which may have introduced response bias. Fifth, DNAR patients were not excluded, potentially confounding survival outcomes. Sixth, OHCA data were registered by EMS staff after each event, which may have introduced recall bias; however, weekly OHCA reviews were conducted to minimize this limitation. Finally, our system did not capture time intervals between CFR alert, acceptance, and arrival, as no CFRs used the designated confirmation feature on the LINE platform during real emergencies. This limitation hindered assessment of system responsiveness. We suspect that the complexity of interacting with the platform during high-stress situations may have discouraged CFRs from using the confirmation function. Future system enhancements should prioritize simplified user interfaces and automatic real-time data logging to enable more accurate tracking of CFR engagement and response metrics.
Conclusion
This study evaluated the activation of a CFR notification system that used a social media platform to alert nearby volunteers of OHCA cases, with the aim of initiating chest compressions and improving bystander CPR. The system demonstrated a modest response rate but did not yet affect the overall bystander CPR rate. Further adjustments to system workflow and expansion of the CFR network may improve both response rates and bystander CPR in future studies.
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