Early prehospital mechanical cardiopulmonary resuscitation use for out-of-hospital cardiac arrest: an observational study.

BACKGROUND: The use of mechanical cardiopulmonary resuscitation device has been very prevalent in out-of-hospital cardiac arrest rescue. This study aimed to investigate whether the timing of mechanical cardiopulmonary resuscitation device set-up correlated with the the outcome of cardiac arrest patients. METHODS: We retrospectively reviewed adult nontrauma cardiac arrest cases in New Taipei City, Taiwan, from January to December 2022. Demographic data, intervention-related factors, and the time variables of mechanical cardiopulmonary resuscitation were collected. The outcomes included the return of spontaneous circulation and 24-hour survival. We compared patients who achieved spontaneous circulation and those who did not with univariate and multivariable regression analyses. RESULTS: In total, 1680 patients who received mechanical cardiopulmonary resuscitation were included in the analysis. Reducing the time interval from manual chest compression initiation to device setup was independently associated with the return of spontaneous circulation and 24-hour survival, especially in the subgroup of patients of initial shockable rhythm. Receiver operating characteristic analysis revealed that the outcome of patients with an initial shockable rhythm could be predicted by the mechanical cardiopulmonary resuscitation setup time, with areas under the curve of 60.8% and 63.9% for ROSC and 24-hour survival, respectively. The cutoff point was 395.5 s for patients with an initial shockable rhythm. CONCLUSION: A positive correlation was found between early mechanical cardiopulmonary resuscitation intervention and the outcomes of out-of-hospital cardiac arrest patients. The time between manual chest compression and device setup could predict the return of spontaneous circulation and 24-hour survival in the subgroup of patients with initially shockable rhythm with the optimal cutoff point at 395.5 s.

Association Between Admission Systolic Blood Pressure and Outcomes in Patients with Isolated Traumatic Brain Injury: A Cross-National Multicenter Cohort Study.

The optimal prehospital blood pressure in patients following traumatic brain injury (TBI) remains controversial. We aimed to assess the association between the systolic blood pressure (SBP) at emergency department triage and patient outcomes following isolated moderate-to-severe TBI. We conducted a cross-national multicenter retrospective cohort study using the Pan-Asia Trauma Outcomes Study database from January 1, 2016, to November 30, 2018. The enrollees were adult patients with isolated moderate-to-severe TBI defined by the International Classification of Diseases code, a Glasgow Coma Scale (GCS) <13 at triage, and a nonhead Abbreviated Injury Scale ≤3. The studied variables were SBPs at triage categorized into different ranges. The primary outcome was 30-day mortality, and the secondary outcome was poor functional status at hospital discharge defined by the modified Rankin Scale ≥4. Multivariable logistic regression was applied to adjust for confounders including country, sex, age, mechanism of injury, prehospital vascular access, respiratory rate, GCS, oxygen saturation, intubation, Injury Severity Score, head surgery, intensive care unit admission, and length of hospital stay. Subgroup analyses were performed on different severity of TBI. A total of 785 patients (median age, 42 years; male patients 77.5%; mean SBP at triage, 136.3 ± 33.1 mmHg) were included in the primary analysis. The lowest 30-day mortality rate existed in patients with SBP of 100-119 mmHg. Taking it as baseline, the adjusted odds ratios (aORs) and 95% confidence intervals (CIs) of SBP <100 mmHg, 120-139 mmHg, 140-159 mmHg, and ≥160 mmHg were 7.05 (2.51-19.78), 3.14 (1.14-8.65), 2.91 (1.04-8.17), and 3.28 (1.14-9.42). As for the secondary outcome, the aORs and 95% CIs were 1.36 (0.68-2.68) of <100 mmHg, 0.99 (0.57-1.70) of 120-139 mmHg, 1.23 (0.67-2.25) of 140-159 mmHg, and 1.52 (0.78-2.95) of ≥160 mmHg. Subgroup analyses revealed trends of the best outcomes in both moderate and severe TBI patients with SBP 100-119 mmHg, whereas statistical significance appeared only in patients with severe TBI. SBP of 110-119 mmHg at triage is associated with the lowest 30-day mortality in patients following isolated moderate-to-severe TBI and possibly related to a better functional outcome.

Intraosseous versus intravenous vascular access in upper extremity among adults with out-of-hospital cardiac arrest: cluster randomised clinical trial (VICTOR trial).

OBJECTIVE: To compare the effectiveness of intraosseous versus intravenous vascular access in the treatment of adult patients with out-of-hospital cardiac arrest. DESIGN: Cluster randomised controlled trial. SETTING: The VICTOR (Venous Injection Compared To intraOsseous injection during resuscitation of patients with out-of-hospital cardiac arrest) trial involved emergency medical service agencies with all four advanced life support ambulance teams in Taipei City, Taiwan. The enrolment period spanned 6 July 2020 to 30 June 2023 and was temporarily suspended between 20 May 2021 and 31 July 2021 owing to the covid-19 pandemic. PARTICIPANTS: Adult (age 20-80 years) patients with non-traumatic out-of-hospital cardiac arrest. INTERVENTIONS: Biweekly randomised clusters of four participating advanced life support ambulance teams were assigned to insert either intravenous or intraosseous access. MAIN OUTCOME MEASURES: The primary outcome was survival to hospital discharge. Secondary outcomes included return of spontaneous circulation, sustained return of spontaneous circulation (≥2 hours), and survival with favourable neurological outcomes (cerebral performance category score ≤2) at hospital discharge. RESULTS: Among 1771 enrolled patients, 1732 (741 in the intraosseous group and 991 in the intravenous group) were included in the primary analysis (median age 65.0 years; 1234 (71.2%) men). In the intraosseous group, 79 (10.7%) patients were discharged alive, compared with 102 (10.3%) patients in the intravenous group (odds ratio 1.04, 95% confidence interval 0.76 to 1.42; P=0.81). The odds ratio of intraosseous versus intravenous access was 1.23 (0.89 to 1.69; P=0.21) for pre-hospital return of spontaneous circulation, 0.92 (0.75 to 1.13; P=0.44) for sustained return of spontaneous circulation, and 1.17 (0.82 to 1.66; P=0.39) for survival with favourable neurological outcomes. CONCLUSIONS: Among adults with non-traumatic out-of-hospital cardiac arrest, initial attempts to establish vascular access through the intraosseous route did not result in different outcomes compared with intravenous access in terms of the proportion of patients surviving to hospital discharge, pre-hospital return of spontaneous circulation, sustained return of spontaneous circulation, and favourable neurological outcomes. TRIAL REGISTRATION: NCT04135547ClinicalTrials.gov NCT04135547.

Cardiopulmonary Resuscitation Without Aortic Valve Compression Increases the Chances of Return of Spontaneous Circulation in Out-of-Hospital Cardiac Arrest: A Prospective Observational Cohort Study.

OBJECTIVES: Following current cardiopulmonary resuscitation (CPR) guidelines, which recommend chest compressions at "the center of the chest," ~50% of patients experiencing out-of-hospital cardiac arrest (OHCA) undergo aortic valve (AV) compression, obstructing blood flow. We used resuscitative transesophageal echocardiography (TEE) to elucidate the impact of uncompressed vs. compressed AV on outcomes of adult patients experiencing OHCA. DESIGN: Prospective observational cohort study. SETTING: Single center. PATIENTS: This study included adult OHCA patients undergoing resuscitative TEE in the emergency department. Patients were categorized into AV uncompressed or AV compressed groups based on TEE findings. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The primary outcome was sustained return of spontaneous circulation (ROSC). The secondary outcomes included end-tidal co2 (Et co2 ) during CPR, any ROSC, survival to ICU and hospital discharge, post-resuscitation withdrawal, and favorable neurologic outcomes at discharge. Additional analyses on intra-arrest arterial blood pressure (ABP) were also conducted. The sample size was pre-estimated at 37 patients/group. From October 2020 to January 2023, 76 patients were enrolled, 39 and 37 in the AV uncompressed and AV compressed groups, respectively. Intergroup baseline characteristics were similar. Compared with the AV compressed group, the AV uncompressed group had a higher probability of sustained ROSC (53.8% vs. 24.3%; adjusted odds ratio [aOR], 4.72; p = 0.010), any ROSC (56.4% vs. 32.4%; aOR, 3.30; p = 0.033), and survival to ICU (33.3% vs. 8.1%; aOR, 6.74; p = 0.010), and recorded higher initial diastolic ABP (33.4 vs. 11.5 mm Hg; p = 0.002) and a larger proportion achieving diastolic ABP greater than 20 mm Hg during CPR (93.8% vs. 33.3%; p < 0.001). The Et co2 , post-resuscitation withdrawal, and survival to discharge revealed no significant intergroup differences. No patients were discharged with favorable neurologic outcomes. Uncompressed AV seemed critical for sustained ROSC across all subgroups. CONCLUSIONS: Absence of AV compression during OHCA resuscitation is associated with an increased chance of ROSC and survival to ICU. However, its effect on long-term outcomes remains unclear.

The FIB-4 scores in the emergency department to predict the outcomes of COVID-19 patients in taiwan.

Objective: We aimed to determine the reliability of using the Fibrosis-4 (FIB-4) index in COVID-19 patients without underlying liver illness. Method: We employed multivariate logistic regression to identify variables that exhibited statistically significant influence on the ultimate outcome. Multilayer perceptron analysis was employed to develop a prediction model for the FIB-4 index concerning ICU admission and intubation rates. However, the scarcity of cases rendered the assessment of the mortality rate unfeasible. We plotted ROC curves to analyze the predictive strength of the FIB-4 index across various age groups. Result: In univariate logistic regression, only the FIB-4 index and respiratory rate demonstrated statistical significance on all poor outcomes. The FIB-4 index for mortality prediction had an ROC and AUC of 0.863 (95% CI: 0.781-0.9444). It demonstrates predictive power across age groups, particularly for age ≥65 (AUC: 0.812, 95% CI: 0.6571-0.9673) and age <65 (AUC: 0.878, 95% CI: 0.8012-0.9558). Its sensitivity for intubation and ICU admission prediction is suboptimal. Conclusion: FIB-4 index had promising power in prediction of mortality rate in all age groups.

Effect of resuscitative endovascular balloon occlusion of the aorta in nontraumatic out-of-hospital cardiac arrest: a multinational, multicenter, randomized, controlled trial.

BACKGROUND: Out-of-hospital cardiac arrest (OHCA) is a significant public health issue worldwide and is associated with low survival rates and poor neurological outcomes. The generation of optimal coronary perfusion pressure (CPP) via high-quality chest compressions is a key factor in enhancing survival rates. However, it is often challenging to provide adequate CPP in real-world cardiopulmonary resuscitation (CPR) scenarios. Based on animal studies and human trials on improving CPP in patients with nontraumatic OHCA, resuscitative endovascular balloon occlusion of the aorta (REBOA) is a promising technique in these cases. This study aims to investigate the benefits of REBOA adjunct to CPR compared with conventional CPR for the clinical management of nontraumatic OHCA. METHODS: This is a parallel-group, randomized, controlled, multinational trial that will be conducted at two urban academic tertiary hospitals in Korea and Taiwan. Patients aged 20-80 years presenting with witnessed OHCA will be enrolled in this study. Eligible participants must fulfill the inclusion criteria, and written informed consent should be collected from their legal representatives. Patients will be randomly assigned to the intervention (REBOA-CPR) or control (conventional CPR) group. The intervention group will receive REBOA and standard advanced cardiovascular life support (ACLS). Meanwhile, the control group will receive ACLS based on the 2020 American Heart Association guidelines. The primary outcome is the return of spontaneous circulation (ROSC). The secondary outcomes include sustained ROSC, survival to admission, survival to discharge, neurological outcome, and hemodynamic changes. DISCUSSION: Our upcoming trial can provide essential evidence regarding the efficacy of REBOA, a mechanical method for enhancing CPP, in OHCA resuscitation. Our study aims to determine whether REBOA can improve treatment strategies for patients with nontraumatic OHCA based on clinical outcomes, thereby potentially providing valuable insights and guiding further advancements in this critical public health area. TRIAL REGISTRATION: ClinicalTrials.gov NCT06031623. Registered on September 9, 2023.

Development and External Validation of Clinical Features-based Machine Learning Models for Predicting COVID-19 in the Emergency Department.

Introduction: Timely diagnosis of patients affected by an emerging infectious disease plays a crucial role in treating patients and avoiding disease spread. In prior research, we developed an approach by using machine learning (ML) algorithms to predict serious acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection based on clinical features of patients visiting an emergency department (ED) during the early coronavirus 2019 (COVID-19) pandemic. In this study, we aimed to externally validate this approach within a distinct ED population. Methods: To create our training/validation cohort (model development) we collected data retrospectively from suspected COVID-19 patients at a US ED from February 23-May 12, 2020. Another dataset was collected as an external validation (testing) cohort from an ED in another country from May 12-June 15, 2021. Clinical features including patient demographics and triage information were used to train and test the models. The primary outcome was the confirmed diagnosis of COVID-19, defined as a positive reverse transcription polymerase chain reaction test result for SARS-CoV-2. We employed three different ML algorithms, including gradient boosting, random forest, and extra trees classifiers, to construct the predictive model. The predictive performances were evaluated with the area under the receiver operating characteristic curve (AUC) in the testing cohort. Results: In total, 580 and 946 ED patients were included in the training and testing cohorts, respectively. Of them, 98 (16.9%) and 180 (19.0%) were diagnosed with COVID-19. All the constructed ML models showed acceptable discrimination, as indicated by the AUC. Among them, random forest (0.785, 95% confidence interval [CI] 0.747-0.822) performed better than gradient boosting (0.774, 95% CI 0.739-0.811) and extra trees classifier (0.72, 95% CI 0.677-0.762). There was no significant difference between the constructed models. Conclusion: Our study validates the use of ML for predicting COVID-19 in the ED and demonstrates its potential for predicting emerging infectious diseases based on models built by clinical features with temporal and spatial heterogeneity. This approach holds promise for scenarios where effective diagnostic tools for an emerging infectious disease may be lacking in the future.

Development of a prediction model for emergency medical service witnessed traumatic out-of-hospital cardiac arrest: A multicenter cohort study.

BACKGROUND/PURPOSE: To develop a prediction model for emergency medical technicians (EMTs) to identify trauma patients at high risk of deterioration to emergency medical service (EMS)-witnessed traumatic cardiac arrest (TCA) on the scene or en route. METHODS: We developed a prediction model using the classical cross-validation method from the Pan-Asia Trauma Outcomes Study (PATOS) database from 1 January 2015 to 31 December 2020. Eligible patients aged ≥18 years were transported to the hospital by the EMS. The primary outcome (EMS-witnessed TCA) was defined based on changes in vital signs measured on the scene or en route. We included variables that were immediately measurable as potential predictors when EMTs arrived. An integer point value system was built using multivariable logistic regression. The area under the receiver operating characteristic (AUROC) curve and Hosmer-Lemeshow (HL) test were used to examine discrimination and calibration in the derivation and validation cohorts. RESULTS: In total, 74,844 patients were eligible for database review. The model comprised five prehospital predictors: age <40 years, systolic blood pressure <100 mmHg, respiration rate >20/minute, pulse oximetry <94%, and levels of consciousness to pain or unresponsiveness. The AUROC in the derivation and validation cohorts was 0.767 and 0.782, respectively. The HL test revealed good calibration of the model (p = 0.906). CONCLUSION: We established a prediction model using variables from the PATOS database and measured them immediately after EMS personnel arrived to predict EMS-witnessed TCA. The model allows prehospital medical personnel to focus on high-risk patients and promptly administer optimal treatment.

Characteristic of school injuries in Asia: a cross-national, multi-center observational study.

BACKGROUND: To prevent school injuries, thorough epidemiological data is an essential foundation. We aimed to investigate the characteristics of school injuries in Asia and explore risk factors for major trauma. METHODS: This retrospective study was conducted in the participating centers of the Pan-Asian Trauma Outcome Study from October 2015 to December 2020. Subjects who reported "school" as the site of injury were included. Major trauma was defined as an Injury Severity Score (ISS) value of ≥16. RESULTS: In total, 1305 injury cases (1.0% of 127,715 events) occurred at schools. Among these, 68.2% were children. Unintentional injuries were the leading cause and intentional injuries comprised 7.5% of the cohort. Major trauma accounted for 7.1% of those with documented ISS values. Multivariable regression revealed associations between major trauma and factors, including age, intention of injury (self-harm), type of injury (traffic injuries, falls), and body part injured (head, thorax, and abdomen). Twenty-two (1.7%) died, with six deaths related to self-harm. Females represented 28.4% of injuries but accounted for 40.9% of all deaths. CONCLUSIONS: In Asia, injuries at schools affect a significant number of children. Although the incidence of injuries was higher in males, self-inflicted injuries and mortality cases were relatively higher in females. IMPACT: Epidemiological data and risk factors for major trauma resulting from school injuries in Asia are lacking. This study identified significant risk factors for major trauma occurring at schools, including age, intention of injury (self-harm), injury type (traffic injuries, falls), and body part injured (head, thoracic, and abdominal injuries). Although the incidence of injuries was higher in males, the incidence of self-harm injuries and mortality rates were higher in females. The results of this would make a significant contribution to the development of prevention strategies and relative policies concerning school injuries.

Comparison of on-scene Glasgow Coma Scale with GCS-motor for prediction of 30-day mortality and functional outcomes of patients with trauma in Asia.

BACKGROUND AND IMPORTANCE: This study compared the on-scene Glasgow Coma Scale (GCS) and the GCS-motor (GCS-M) for predictive accuracy of mortality and severe disability using a large, multicenter population of trauma patients in Asian countries. OBJECTIVE: To compare the ability of the prehospital GCS and GCS-M to predict 30-day mortality and severe disability in trauma patients. DESIGN: We used the Pan-Asia Trauma Outcomes Study registry to enroll all trauma patients >18 years of age who presented to hospitals via emergency medical services from 1 January 2016 to November 30, 2018. SETTINGS AND PARTICIPANTS: A total of 16,218 patients were included in the analysis of 30-day mortality and 11 653 patients in the analysis of functional outcomes. OUTCOME MEASURES AND ANALYSIS: The primary outcome was 30-day mortality after injury, and the secondary outcome was severe disability at discharge defined as a Modified Rankin Scale (MRS) score ≥4. Areas under the receiver operating characteristic curve (AUROCs) were compared between GCS and GCS-M for these outcomes. Patients with and without traumatic brain injury (TBI) were analyzed separately. The predictive discrimination ability of logistic regression models for outcomes (30-day mortality and MRS) between GCS and GCS-M is illustrated using AUROCs. MAIN RESULTS: The primary outcome for 30-day mortality was 1.04% and the AUROCs and 95% confidence intervals for prediction were GCS: 0.917 (0.887-0.946) vs. GCS-M:0.907 (0.875-0.938), P  = 0.155. The secondary outcome for poor functional outcome (MRS ≥ 4) was 12.4% and the AUROCs and 95% confidence intervals for prediction were GCS: 0.617 (0.597-0.637) vs. GCS-M: 0.613 (0.593-0.633), P  = 0.616. The subgroup analyses of patients with and without TBI demonstrated consistent discrimination ability between the GCS and GCS-M. The AUROC values of the GCS vs. GCS-M models for 30-day mortality and poor functional outcome were 0.92 (0.821-1.0) vs. 0.92 (0.824-1.0) ( P  = 0.64) and 0.75 (0.72-0.78) vs. 0.74 (0.717-0.758) ( P  = 0.21), respectively. CONCLUSION: In the prehospital setting, on-scene GCS-M was comparable to GCS in predicting 30-day mortality and poor functional outcomes among patients with trauma, whether or not there was a TBI.

Modified physiologic criteria for the field triage scheme: Efficacy of major trauma recognition in different age groups in Asia.

BACKGROUND: Major trauma is a leading cause of unexpected death globally, with increasing age-adjusted death rates for unintentional injuries. Field triage schemes (FTSs) assist emergency medical technicians in identifying appropriate medical care facilities for patients. While full FTSs may improve sensitivity, step-by-step field triage is time-consuming. A simplified FTS (sFTS) that uses only physiological and anatomical criteria may offer a more rapid decision-making process. However, evidence for this approach is limited, and its performance in identifying all age groups requiring trauma center resources in Asia remains unclear. METHODS: We conducted a multinational retrospective cohort study involving adult trauma patients admitted to emergency departments in the included countries from 2016 to 2020. Prehospital and hospital data were reviewed from the Pan-Asia Trauma Outcomes Study database. Patients aged ≥18 years transported by emergency medical services were included. Patients lacking data regarding age, sex, physiological criteria, or injury severity scores were excluded. We examined the performance of sFTS in all age groups and fine-tuned physiological criteria to improve sFTS performance in identifying high-risk trauma patients in different age groups. RESULTS: The sensitivity and specificity of the physiological and anatomical criteria for identifying major trauma (injury severity score ≥ 16) were 80.6% and 58.8%, respectively. The modified sFTS showed increased sensitivity and decreased specificity, with more pronounced changes in the young age group. Adding the shock index further increased sensitivity in both age groups. CONCLUSIONS: sFTS using only physiological and anatomical criteria is suboptimal for Asian adult patients with trauma of all age groups. Adjusting the physiological criteria and adding a shock index as a triage tool can improve the sensitivity of severely injured patients, particularly in young age groups. A swift field triage process can maintain acceptable sensitivity and specificity in severely injured patients.

Emergency Medical Services in Taiwan: Past, Present, and Future.

This review assessed the development of Taiwan's emergency medical services (EMS) and focused on the optimizing initiatives of the EMS systems, the current state of Taiwan's EMS system, EMS benchmarks in different regions of Taiwan, EMS response during the coronavirus disease 2019 (COVID-19) pandemic, and future design. In the past decade, there has been a noticeable increase in prehospital services, numerous optimizing initiatives to improve patient prognosis, and the medical oversight model. Taiwan's current EMS system, including the dispatch system, out-of-hospital cardiac arrest (OHCA) patient management, time-sensitive critical illness in prehospital settings, and disaster response, has undergone significant improvements. These improvements have been demonstrated to have a measurable impact on patient outcomes, as supported by medical literature. Each region in Taiwan has developed a unique EMS system with local characteristics, such as the implementation of the Global Resuscitation Alliance 10 steps for OHCA-related quality control, hearing automated external defibrillator program, a five-level prehospital triage system, an island-hopping strategy for patients with major trauma, dispatcher-assisted teamwork for OHCA resuscitation, and optimized prehospital care for acute coronary syndrome patients. In response to the COVID-19 pandemic from 2019 to 2023, Taiwan's EMS implemented measures to combat the outbreak such as interagency collaboration to obtain patient's personal information, to optimize prehospital management initiatives, and to provide financial compensation and personal insurance for emergency medical technicians. The areas that need focus include integrating prehospital and in-hospital information to build a national-level database (One-Stop Emergency Management), increasing public awareness of first responders and emergency casualty care, and evolving the EMS system by incorporating private EMS system, initiating school-based education of paramedicine, and legally recognizing paramedics as medical and health care personnel. By improving these areas, we can better prepare for the future and ensure that Taiwan's EMS system continues to provide high-quality care to those in need.

Effect of crew ratio of advanced life support-trained personnel on patients with out-of-hospital cardiac arrest: A systematic review and meta-analysis.

BACKGROUND/PURPOSE: This review aimed to investigate the effect of crew ratios of on-scene advanced life support (ALS)-trained personnel on patients with out-of-hospital cardiac arrest (OHCA). METHODS: We systematically searched PubMed, Ovid EMBASE, and the Cochrane Central Register of Controlled Trials databases from the inception date until September 30, 2022, for eligible studies. Two reviewers independently screened the studies for relevance, extracted data, and quality. We compared the effect of the ratio of on-scene ALS-trained personnel >50 % to those with a ratio ≤50 % among prehospital personnel on the clinical outcomes of OHCA patients. The primary outcome was survival-to-discharge and secondary outcomes were any return of spontaneous circulation (ROSC), sustained ROSC (≥2 h), and favourable neurological outcome at discharge (cerebral performance category scores: 1 or 2). Pooled odds ratios (ORs) were calculated, and the certainty of evidence was assessed. RESULTS: From 10,864 references, we identified four non-randomised studies, including 16,475 patients. Two studies were performed in Japan and two in Taiwan. There were significant differences in survival-to-discharge (OR: 1.24, 95 % confidence interval [CI]: 1.07-1.44, I2: 7 %), any ROSC (OR:1.22, 95 % CI: 1.04-1.43, I2: 74 %) and sustained ROSC (OR: 1.39, 95 % CI: 1.16-1.65, I2: 40 %), but insignificant differences in favourable neurological outcome at discharge. The overall certainty of evidence was rated as very low for all outcomes. CONCLUSION: Prehospital ALS care with a ratio of on-scene ALS-trained personnel >50 % could improve OHCA patient outcomes than crew ratios ≤50 %. Further studies are required to reach a robust conclusion.