Abstract Background Bystander automated external defibrillator (BAED) use improves out-of-hospital cardiac arrest (OHCA) outcomes but remains uncommon globally. This study evaluated the outcomes of Singapore’s 11-year public-access AED expansion and volunteer-responder implementation in terms of trends in BAED application, associated factors, and clinical outcomes. Methods This population-based, retrospective cohort study used Singapore Pan-Asian Resuscitation Outcomes Study (SG-PAROS) data (2010–2020) for adult, non-traumatic OHCAs. The primary outcome was bystander AED application. Multivariable logistic regression identified factors associated with use. Secondary outcomes included favorable neurological status (CPC 1–2), survival to discharge, and prehospital return of spontaneous circulation (ROSC). Results Of 21,439 included OHCA cases (median age 70.0 years; 63.8% male), BAED application increased from 1.7% to 9.6% over 11 years, with a corresponding increase in overall survival from 2.4 to 4.0%. Malay ethnicity (aOR 1.25, 1.06–1.49), calendar year (aOR 1.26, 1.22–1.29), and delayed emergency medical services (aOR 1.24, 1.06–1.45) were positive predictors of BAED application. Conversely, BAED application was lower among females (aOR 0.80, 95% CI 0.69–0.94), at night (aOR 0.69, 0.56–0.86), and in residential settings (aOR 0.06, 0.05–0.07). Volunteer arrival strongly increased application (aOR 4.16, 3.41–5.09), with a significant interaction (p<0.001); the effect was greater in residential (aOR 7.38, 5.81–9.38) than non-residential settings (aOR 1.71, 1.22–2.40). AED use predicted favorable neurological outcome (aOR 2.80, 2.24–3.50; NNT 8.7), survival (aOR 2.30, 1.89–2.80), and ROSC (aOR 2.11, 1.81–2.46). Conclusion Over 11 years, we saw a significant increase in BAED application and favorable neurological survival. This success was associated with the implementation of an integrated strategy combining widespread AED deployment, national training, and smartphone-activated volunteer responders. Singapore’s experience provides a scalable model for urban centers seeking to expand their AED strategy.

Introduction The earliest and impactful intervention for out-of-hospital cardiac arrest (OHCA) patients is cardiopulmonary resuscitation (CPR) delivered by a community first responder (CFR). However, the CFRs often fail to meet the established performance targets for compression rate and depth throughout the event, thereby defeating the purpose of instituting the CFR system. While telephone CPR has been shown to help, certain aspects cannot be improved with a voice-only guidance. Therefore, a trial has been designed to evaluate an enhanced CFR support system (eCSS) intervention that comprises a) audio/video communication between a CFR and dispatcher, in addition to b) relaying compression depth and rate data to the dispatcher in real time through a battery-operated Bluetooth-enabled motion sensor-mounted CPR card connected to a smart phone through an application over 5G mobile phone network. Both these features of eCSS will allow the dispatchers to better guide the CFR, ensuring high-quality CPR. The control group will have voice-only dispatcher assistance as per the current standard of care. Objective: This protocol paper describes the rationale, methodology, and run-in period recruitment experience of the trial, where all non-pregnant adult suspected OHCA patients will be eligible for the study, on whom CFR provides CPR engaging the eCSS . CFRs will be recruited from a volunteers’ registry maintained by the Singapore Civic Defence Force, the largest publicly funded EMS agency. This trial protocol has been registered in the ClinicalTrials.gov registry [ID NCT06530433].

OBJECTIVE:To assess the cumulative effect of multiple interventions on time interval to first chest compression and survival outcomes of out-of-hospital cardiac arrest (OHCA). METHODS:We conducted a secondary analysis of a prospective national cohort study on adult, non-traumatic OHCA in Singapore. Six nationwide interventions were implemented sequentially, including the introduction of fire-bikers, dispatch-assisted cardiopulmonary resuscitation, a first responder public cardiopulmonary resuscitation training program, the myResponder phone application, the Save-A-Life public access defibrillation program and first responder high-performance cardiopulmonary resuscitation training, dividing the study period into seven distinct time periods. The outcomes were system-level estimate of time interval to first chest compression and survival outcomes. RESULTS:The time interval to first chest compression for OHCA patients was 10.6 (8.5, 13.4), 10.9 (8.8, 13.9), 7.5 (0.0, 11.9), 5.0 (0.0, 12.1), 5.0 (2.4, 11.9), 4.3 (2.0, 10.5) and 4.5 (2.1, 11.3) minutes from period 1 to 7, respectively. Interventions were significantly associated with reduced time interval to first chest compression (β-estimate -4.09, 95 % confidence interval (CI): -4.81, -3.37), and increased likelihood of survival to hospital discharge (odds ratio (OR) 2.09; 95 % CI, 1.39-3.14) and survival with favorable neurological outcomes (OR 3.06; 95 % CI, 1.79-5.25) after implementation of the six nationwide interventions, compared with pre-intervention. The time interval to first chest compression significantly explained 21.17 % and 22.67 % of the relationship between interventions and survival to discharge and favorable neurological outcomes, respectively. CONCLUSION:The implementation of cumulative multiple interventions was significantly associated with reduced time to first chest compression and improved OHCA survival outcomes.

BACKGROUND:The smartphone application to activate a community first responder (myResponder) was launched in 2015 to activate volunteer first responders for Out-of-Hospital Cardiac Arrest (OHCA) patients in Singapore. This study aimed to investigate the impact of myResponder on provision of bystander CPR, bystander AED, and patient survival outcomes. METHODS:This was a retrospective analysis using the Singapore Pan-Asian Resuscitation Outcomes Study between 2016 and 2019 that included adult non-traumatic OHCA patients. Patients were categorized into myResponder activated and non-activated groups. The primary outcomes were bystander CPR and bystander AED. The secondary outcome was survival at 30-days with favourable neurological outcomes (cerebral performance category 1-2). A multivariable logistic regression analysis was performed and we reported adjusted odds ratio [aOR] and 95% confidence interval for the effect of activation. RESULTS:9,167 patients were included in this analysis. The median (Interquartile range, IQR) age was 71 (59-82) years. The activated group comprised 5,499 (60%) of cases. The activated group was associated with higher bystander CPR (aOR [95%CI]: 5.69 [4.89-6.62]) and bystander AED (aOR [95% CI]: 2.23 [1.82-2.74]) compared to non-activated group. The activated group was associated with better survival at 30 days with favourable neurological outcomes (aOR [95% CI]: 1.54 [1.11-2.15]). CONCLUSION:We found that the implementation of technology-activated first responders was associated with an improvement in the performance of bystander CPR, bystander AED application, and OHCA outcomes in an urban area. Further efforts should be made to promote the use of activated first responders in EMS systems.

BACKGROUND:We aimed to investigate the association between the time taken to start dispatcher-assisted cardiopulmonary resuscitation (DA-CPR) and survival outcomes for OHCA. METHODS:This was a retrospective analysis using the Singapore Pan-Asian Resuscitation Outcomes Study data between 2012 and 2021. We included all adult, witnessed, non-traumatic OHCA patients who received DA-CPR. The exposure of interest was time interval from emergency call to start of DA-CPR. Patients were divided into three groups based on previous studies. The outcome was defined as survival to 30-days with favorable neurological outcomes. Multivariable logistic regression analysis was performed. Restricted cubic spline curves were used to explore non-linear relationships. RESULTS:3,861 OHCA patients were included in this analysis. Patients were grouped as follows: short (0-179 s), medium (180-239 s), and long (≥240 s) to start DA-CPR. Adjusted odds ratios [95% CI] for survival to 30-days with favorable neurological outcomes were: medium 0.82 [0.52-1.28], long 0.63 [0.40-0.98]. The restricted cubic spline curve showed a monotonic decrease in the odds ratio for survival to 30-days with favorable neurological outcomes. CONCLUSIONS:This study found that among non-traumatic, witnessed OHCA patients who received DA-CPR, a shorter time to start DA-CPR was associated with better 30-day survival with favorable neurological outcomes.

Background:Shock-refractory ventricular fibrillation (VF) or ventricular tachycardia (VT) is a treatment challenge in out-of-hospital cardiac arrest (OHCA). This study aimed to develop and validate machine learning models that could be implemented by emergency medical services (EMS) to predict refractory VF/VT in OHCA patients. Methods:This was a retrospective study examining adult non-traumatic OHCA patients brought into the emergency department by Singapore EMS from the Pan-Asian Resuscitation Outcomes Study (PAROS) registry. Data from April 2010 to March 2020 were extracted for this study. Refractory VF/VT was defined as VF/VT persisting or recurring after at least one shock. Features were selected based on expert clinical opinion and availability to dispatch prior to arrival at scene. Multivariable logistic regression (MVR), LASSO and random forest (RF) models were investigated. Model performance was evaluated using receiver operator characteristic (ROC) area under curve (AUC) analysis and calibration plots. Results:20,713 patients were included in this study, of which 860 (4.1%) fulfilled the criteria for refractory VF/VT. All models performed comparably and were moderately well-calibrated. ROC-AUC were 0.732 (95% CI, 0.695 - 0.769) for MVR, 0.738 (95% CI, 0.701 - 0.774) for LASSO, and 0.731 (95% CI, 0.690 - 0.773) for RF. The shared important predictors across all models included male gender and public location. Conclusion:The machine learning models developed have potential clinical utility to improve outcomes in cases of refractory VF/VT OHCA. Prediction of refractory VF/VT prior to arrival at patient's side may allow for increased options for intervention both by EMS and tertiary care centres.

BACKGROUND:Historically in Singapore, all out-of-hospital cardiac arrests (OHCA) were transported to hospital for pronouncement of death. A 'Termination of Resuscitation' (TOR) protocol, implemented from 2019 onwards, enables emergency responders to pronounce death at-scene in Singapore. This study aims to evaluate the cost-effectiveness of the TOR protocol for OHCA management. METHODS:Adopting a healthcare provider's perspective, a Markov model was developed to evaluate three competing options: No TOR, Observed TOR reflecting existing practice, and Full TOR if TOR is exercised fully. The model had a cycle duration of 30 days after the initial state of having a cardiac arrest, and was evaluated over a 10-year time horizon. Probabilistic sensitivity analysis was performed to account for uncertainties. The costs per quality adjusted life years (QALY) was calculated. RESULTS:A total of 3,695 OHCA cases eligible for the TOR protocol were analysed; mean age of 73.0 ± 15.5 years. For every 10,000 hypothetical patients, Observed TOR and Full TOR had more deaths by approximately 19 and 31 patients, respectively, compared to No TOR. Full TOR had the least costs and QALYs at $19,633,369 (95% Uncertainty Interval (UI) 19,469,973 to 19,796,764) and 0 QALYs. If TOR is exercised for every eligible case, it could expect to save approximately $400,440 per QALY loss compared to No TOR, and $821,151 per QALY loss compared to Observed TOR. CONCLUSION:The application of the TOR protocol for the management of OHCA was found to be cost-effective within acceptable willingness-to-pay thresholds, providing some justification for sustainable adoption.

BACKGROUND:Bystander cardiopulmonary resuscitation (CPR) for out-of-hospital cardiac arrest (OHCA) has increased in Singapore, Japan, and South Korea following the implementation of several public health, bystander-focused interventions, such as dispatcher-assisted CPR and community CPR training. It is unclear whether bystander CPR prevalence will continue on this trajectory over time. This study aimed to investigate the temporal trends of bystander CPR prevalence over a ten-year period in these three Asian countries. METHOD:Using the national OHCA registries of Singapore, Japan and South Korea, we included witnessed, non-traumatic adult OHCA registered between 2010 and 2020 in Singapore and Japan, and between 2012 and 2020 in South Korea. We excluded those for whom resuscitation was not attempted or was terminated at scene. The study analysed the proportion of bystander CPR in the three countries, presenting the data annually and further breaking it down by age and gender. RESULTS:This study included 491,067 patients in Japan [male 59 %, median, age 79 years (Q1-Q3, 69-87)], 13,143 patients in Singapore [male 66 %, median, age 69 years (Q1-Q3, 57-80)], and 87,997 patients in South Korea [male 64 %, median age 72 years (Q1-Q3, 59-81)]. The proportion of bystander CPR in each country had increased (Japan: 39 % in 2010 to 45 % in 2015, Singapore: 22 % in 2010 to 53 % in 2015, and South Korea: 37 % in 2012 to 56 % in 2015); however, these proportions have plateaued in 2020 (Japan: 46 %, Singapore: 54 %, and South Korea: 57 %) despite continued efforts. These trends were consistent across different age groups, gender and location. CONCLUSION:This study investigated the trend of bystander CPR over 10 years in three Asian countries. Although the proportion of bystander CPR has increased, it has now plateaued between 50-60 %. Further research is necessary to identify the contributing factors and advance beyond this "invisible ceiling".

Objectives:With more elderly presenting with Out-of-Hospital Cardiac Arrests (OHCAs) globally, neurologically intact survival (NIS) should be the aim of resuscitation. We aimed to study the trend of OHCA amongst elderly in a large Asian registry to identify if age is independently associated with NIS and factors associated with NIS. Methods:All adult OHCAs aged ≥18 years attended by emergency medical services (EMS) from April 2010 to December 2019 in Singapore was extracted from the Pan-Asian Resuscitation Outcomes Study (PAROS) registry. Cases pronounced dead at scene, non-EMS transported, traumatic OHCAs and OHCAs in ambulances were excluded. Patient characteristics and outcomes were compared across four age categories (18-64, 65-79, 80-89, ≥90). Multivariable logistic regression analysis determined the factors associated with NIS. Results:19,519 eligible cases were analyzed. OHCA incidence increased with age almost doubling in octogenarians (from 312/100,000 in 2011 to 652/100,000 in 2019) and tripling in those ≥90 years (from 458/100,000 in 2011 to 1271/100,000 in 2019). The proportion of patients with NIS improved over time for the 18-64, 65-79- and 80-89-years age groups, with the greatest improvement in the youngest group. NIS decreased with each increasing year of age and minute of response time. NIS increased in the arrests of presumed cardiac etiology, witnessed and bystander CPR. Conclusions:Survival with good outcomes has increased even amongst the elderly. Regardless of age, NIS is possible with good-quality CPR, highlighting its importance. End-of-life planning is a complex yet necessary decision that requires qualitative exploration with elderly, their families and care providers.

OBJECTIVES:The relationship between the bystander witness type and receipt of bystander CPR (BCPR) is not well understood. Herein we compared BCPR administration between family and non-family witnessed out-of-hospital cardiac arrest (OHCA). BACKGROUND:In many communities, interventions in the past decade have contributed to an increased receipt of BCPR, for example in Singapore from 15% to 60%. However, BCPR rates have plateaued despite sustained and ongoing community-based interventions, which may be related to gaps in education or training for various witness types. The purpose of this study was to investigate the association between witness type and BCPR administration. METHODS:Singapore data from 2010-2020 was extracted from the Pan-Asian Resuscitation Outcomes Study (PAROS) network registry (n = 25,024). All adult, layperson witnessed, non-traumatic OHCAs were included in this study. RESULTS:Of 10,016 eligible OHCA cases, 6,895 were family witnessed and 3,121 were non-family witnessed. After adjustment for potential confounders, BCPR administration was less likely for non-family witnessed OHCA (OR 0.83, 95% CI 0.75, 0.93). After location stratification, non-family witnessed OHCAs were less likely to receive BCPR in residential settings (OR 0.75, 95% CI 0.66, 0.85). In non-residential settings, there was no statistically significant association between witness type and BCPR administration (OR 1.11, 95% CI 0.88, 1.39). Details regarding witness type and bystander CPR were limited. CONCLUSION:This study found differences in BCPR administration between family and non-family witnessed OHCA cases. Elucidation of witness characteristics may be useful to determine populations that would benefit most from CPR education and training.

BACKGROUND:Community first responders (CFRs) strengthen the Chain of Survival for out-of-hospital cardiac arrest (OHCA) care. Considerable efforts have been invested in Singapore's CFR program, during the years 2016-2020, by developing an app-based activation system called myResponder. This paper reports on national CFR response indicators to evaluate the real-world impact of these efforts. METHODS:We matched data from the Singapore Civil Defence Force's CFR registry with the Pan Asian Resuscitation Outcomes Study (PAROS) registry data to calculate performance indicators. These included the number of CFRs receiving and accepting an issued alert per OHCA event. Also calculated were the fraction of OHCA events where CFRs received an issued alert, or accepted the alert, and arrived at the scene either before or after EMS. We also present trends of these indicators and compare the prevalence of these fractions between the CFR-attended and CFR-unattended OHCA events. RESULTS:Of 6577 alerted OHCA events, 42.7% accepted an alert, 50% of these arrived at the scene and 71% of them arrived before EMS. Almost all CFR response indicators improved over time even for the pandemic year (2020). The fraction of OHCA events where >2 CFRs received an alert increased from 62% to 96%; the same figure for accepting an alert did not change much but >2 CFRs arriving at the scene increased from 0% to 7.5%. The fraction of OHCA events with an automated external defibrillator applied and defibrillation performed by CFR increased from 4.2% to 10.3% and 1.6% to 3%, respectively. Statistically significant differences were observed in these indicators when CFR-attended and CFR-unattended OHCA events were compared. CONCLUSION:This real-world study shows that activating CFRs using mobile technology can improve community response to OHCA and are bearing fruit in Singapore at a national level. Some targets for improvement and future research are highlighted in this report.

Abstract Background Singapore and Osaka in Japan have comparable population sizes and prehospital management; however, the frequency of ECPR differs greatly for out-of-hospital cardiac arrest (OHCA) patients with initial shockable rhythm. Given this disparity, we hypothesized that the outcomes among the OHCA patients with initial shockable rhythm in Singapore were different from those in Osaka. The aim of this study was to evaluate the outcomes of OHCA patients with initial shockable rhythm in Singapore compared to the expected outcomes derived from Osaka data using machine learning-based prediction models. Methods This was a secondary analysis of two OHCA databases: the Singapore PAROS database (SG-PAROS) and the Osaka-CRITICAL database from Osaka, Japan. This study included adult (18–74 years) OHCA patients with initial shockable rhythm. A machine learning-based prediction model was derived and validated using data from the Osaka-CRITICAL database (derivation data 2012–2017, validation data 2018–2019), and applied to the SG-PAROS database (2010–2016 data), to predict the risk-adjusted probability of favorable neurological outcomes. The observed and expected outcomes were compared using the observed–expected ratio (OE ratio) with 95% confidence intervals (CI). Results From the SG-PAROS database, 1,789 patients were included in the analysis. For OHCA patients who achieved return of spontaneous circulation (ROSC) on hospital arrival, the observed favorable neurological outcome was at the same level as expected (OE ratio: 0.905 [95%CI: 0.784–1.036]). On the other hand, for those who had continued cardiac arrest on hospital arrival, the outcomes were lower than expected (shockable rhythm on hospital arrival, OE ratio: 0.369 [95%CI: 0.258–0.499], and nonshockable rhythm, OE ratio: 0.137 [95%CI: 0.065–0.235]). Conclusion This observational study found that the outcomes for patients with initial shockable rhythm but who did not obtain ROSC on hospital arrival in Singapore were lower than expected from Osaka. We hypothesize this is mainly due to differences in the use of ECPR.

Background Previous research indicated outcomes among refractory out-of-hospital cardiac arrest (OHCA) patients with initial shockable rhythm were different in Singapore and Osaka, Japan, possibly due to the differences in access to extracorporeal cardiopulmonary resuscitation. However, this previous study had a risk of selection bias. To address this concern, this study aimed to evaluate the outcomes between Singapore and Osaka for OHCA patients with initial shockable rhythm using only population-based databases. Methods This was a secondary analysis of two OHCA population-based databases in Osaka and Singapore, including adult OHCA patients with initial shockable rhythm. A machine-learning-based prediction model was derived from the Osaka data ( n = 3088) and applied to the PAROS-SG data ( n = 2905). We calculated the observed-expected ratio (OE ratio) for good neurological outcomes observed in Singapore and the expected derived from the data in Osaka by dividing subgroups with or without prehospital ROSC. Results The one-month good neurological outcomes in Osaka and Singapore among patients with prehospital ROSC were 70% (791/1,125) and 57% (440/773), and among patients without prehospital ROSC were 10% (196/1963) and 2.8% (60/2,132). After adjusting patient characteristics, the outcome in Singapore was slightly better than expected from Osaka in patients with ROSC (OE ratio, 1.067 [95%CI 1.012 to 1.125]), conversely, it was worse than expected in patients without prehospital ROSC (OE ratio, 0.238 [95%CI 0.173 to 0.294]). Conclusion This study showed the outcomes of OHCA patients without prehospital ROSC in Singapore were worse than expected derived from Osaka data even using population-based databases. (249/250 words).

Introduction: Female sex is associated with lower receipt of bystander cardiopulmonary resuscitation (BCPR) in public. Telephone-assisted CPR (TCPR) may attenuate this known sex difference. It is unknown whether the introduction of community-wide, bystander-focused interventions may reduce this known sex difference and improve outcomes for females. Objectives: We sought to assess whether implementation of bystander-focused, out-of-hospital cardiac arrest (OHCA) interventions attenuated the sex difference seen in receipt of BCPR. We hypothesized that implementation of bystander-focused interventions would reduce the known difference observed in males compared to females in receipt of BCPR in public. Methods: We conducted a retrospective study of adult, non-traumatic OHCAs from the Singapore OHCA registry (1/2011-12/2020). Bystander-focused interventions included TCPR (7/2012 - present), CPR/AED training (04/2014 - present), and myResponder (4/2015 - present). We examined the differences between males vs females in receipt of BCPR in public using descriptive statistics, a sex-intervention interaction term, and hierarchical regression modeling. Results: The registry contained 19,321 events (2011-2020). Excluding pediatric, traumatic, EMS witnessed, and healthcare facility arrests, 18,925 events were analyzed. Of these, mean age was 68±16 and 64% were male. BCPR was administered in 56% of the events, with 61% of males and 54% of females receiving BCPR in public (p-value <0.01). Females had a 29% decreased odds of receiving BCPR compared to males in public (OR: 0.72 (95% CI: 0.58-0.90), p-value <0.01). With inclusion of implementation of bystander-focused interventions as an interaction term with sex, the difference in receipt of BCPR between males and females was no longer observed (p-value: ns). The sex-intervention interaction term was statistically significant (p-value<0.01). No sex differences were observed when modelling survival as an outcome. Conclusion: The introduction of community-wide, bystander-focused interventions may lessen differences seen in receipt of BCPR by males and females in public. Further research on OHCA interventions is needed to increase provision of BCPR and consider addressing this disparity.

Background Termination-of-resuscitation rules (TORRs) in out-of-hospital cardiac arrest (OHCA) patients have been applied in western countries; in Asia, two TORRs were developed and have not been externally validated widely. We aimed to externally validate the TORRs using the registry of Pan-Asian Resuscitation Outcomes Study (PAROS). Methods PAROS enrolled 66,780 OHCA patients in seven Asian countries from 1 January 2009 to 31 December 2012. The American Heart Association-Basic Life Support and AHA-ALS (AHA-BLS), AHA-Advanced Life Support (AHA-ALS), Goto, and Shibahashi TORRs were selected. The diagnostic test characteristics and area under the receiver operating characteristic curve (AUC) were calculated. We further determined the most suitable TORR in Asia and analysed the variable differences between subgroups. Results We included 55,064 patients in the final analysis. The sensitivity, specificity, negative predictive value, positive predictive value, and AUC, respectively, for AHA-BLS, AHA-ALS, Goto, Shibashi TORRs were 79.0%, 80.0%, 19.6%, 98.5%, and 0.80; 48.6%, 88.3%, 9.8%, 98.5%, and 0.60; 53.8%, 91.4%, 11.2%, 99.0%, and 0.73; and 35.0%, 94.2%, 8.4%, 99.0%, and 0.65. In countries using the Goto TORR with PPV<99%, OHCA patients were younger, had more males, a higher rate of shockable rhythm, witnessed collapse, pre-hospital defibrillation, and survival to discharge, compared with countries using the Goto TORR with PPV ≥99%. Conclusions There was no single TORR fit for all Asian countries. The Goto TORR can be considered the most suitable; however, a high predictive performance with PPV ≥99% was not achieved in three countries using it (Korea, Malaysia, and Taiwan).