Survival models for out-of-hospital cardiopulmonary resuscitation from the perspectives of the bystander, the first responder, and the paramedic

Enhancing the accuracy of shock advisory algorithms in automated external defibrillators during ongoing cardiopulmonary resuscitation using a cascade of CNNEDs

Delivery of continuous cardiopulmonary resuscitation (CPR) plays an important role in the out-of-hospital cardiac arrest (OHCA) survival rate. However, to prevent CPR artifacts being superimposed on ECG morphology data, currently available automated external defibrillators (AEDs) require pauses in CPR for accurate analysis heart rhythms. In this study, we propose a novel Convolutional Neural Network-based Encoder-Decoder (CNNED) structure with a shock advisory algorithm to improve the accuracy and reliability of shock versus non-shock decision-making without CPR pause in OHCA scenarios. Our approach employs a cascade of CNNEDs in conjunction with an AED shock advisory algorithm to process the ECG data for shock decisions. Initially, a CNNED trained on an equal number of shockable and non-shockable rhythms is used to filter the CPR-contaminated data. The resulting filtered signal is then fed into a second CNNED, which is trained on imbalanced data more tilted toward the specific rhythm being analyzed. A reliable shock versus non-shock decision is made when both classifiers from the cascade structure agree, while segments with conflicting classifications are labeled as indeterminate, indicating the need for additional segments to analyze. To evaluate our approach, we generated CPR-contaminated ECG data by combining clean ECG data with 52 CPR samples. We used clean ECG data from the CUDB, AFDB, SDDB, and VFDB databases, to which 52 CPR artifact cases were added, while a separate test set provided by the AED manufacturer Defibtech LLC was used for performance evaluation. The test set comprised 20,384 non-shockable CPR-contaminated segments from 392 subjects, as well as 3744 shockable CPR-contaminated samples from 41 subjects with coarse ventricular fibrillation (VF) and 31 subjects with rapid ventricular tachycardia (rapid VT). We observed improvements in rhythm analysis using our proposed cascading CNNED structure when compared to using a single CNNED structure. Specifically, the specificity of the proposed cascade of CNNED structure increased from 99.14% to 99.35% for normal sinus rhythm and from 96.45% to 97.22% for other non-shockable rhythms. Moreover, the sensitivity for shockable rhythm detection increased from 90.90% to 95.41% for ventricular fibrillation and from 82.26% to 87.66% for rapid ventricular tachycardia. These results meet the performance thresholds set by the American Heart Association and demonstrate the reliable and accurate analysis of heart rhythms during CPR using only ECG data without the need for CPR interruptions or a reference signal.

Improving EMS response times for out-of-hospital cardiac arrest in urban areas using drone-like vertical take-off and landing air ambulances: An international, simulation-based cohort study

BACKGROUND

Advances in vertical take-off and landing (VTOL) technologies may enable drone-like crewed air ambulances to rapidly respond to out-of-hospital cardiac arrest (OHCA) in urban areas. We estimated the impact of incorporating VTOL air ambulances on OHCA response intervals in two large urban centres in France and Canada.

METHODS

We included adult OHCAs occurring between Jan. 2017-Dec. 2018 within Greater Paris in France and Metro Vancouver in Canada. Both regions utilize tiered OHCA response with basic (BLS)- and advanced life support (ALS)-capable units. We simulated incorporating 1-2 ALS-capable VTOL air ambulances dedicated to OHCA response in each study region, and computed time intervals from call reception by emergency medical services (EMS) to arrival of the: (1) first ALS unit ("call-to-ALS arrival interval"); and (2) first EMS unit ("call-to-first EMS arrival interval").

RESULTS

There were 6,217 OHCAs included during the study period (3,760 in Greater Paris and 2,457 in Metro Vancouver). Historical median call-to-ALS arrival intervals were 21 min [IQR 16-29] in Greater Paris and 12 min [IQR 9-17] in Metro Vancouver, while median call-to-first EMS arrival intervals were 11 min [IQR 8-14] and 7 min [IQR 5-8] respectively. Incorporating 1-2 VTOL air ambulances improved median call-to-ALS arrival intervals to 7-9 min and call-to-first EMS arrival intervals to 6-8 min in both study regions (all P < 0.001).

CONCLUSION

VTOL air ambulances dedicated to OHCA response may improve EMS response intervals, with substantial improvements in ALS response metrics.

Prediction Models for Return of Spontaneous Circulation in Patients with Cardiac Arrest: A Systematic Review and Critical Appraisal

Objectives

Prediction models for the return of spontaneous circulation (ROSC) in patients with cardiac arrest play an important role in helping physicians evaluate the survival probability and providing medical decision-making reference. Although relevant models have been developed, their methodological rigor and model applicability are still unclear. Therefore, this study aims to summarize the evidence for ROSC prediction models and provide a reference for the development, validation, and application of ROSC prediction models.

Methods

PubMed, Cochrane Library, Embase, Elsevier, Web of Science, SpringerLink, Ovid, CNKI, Wanfang, and SinoMed were systematically searched for studies on ROSC prediction models. The search time limit was from the establishment of the database to August 30, 2022. Two reviewers independently screened the literature and extracted the data. The PROBAST was used to evaluate the quality of the included literature.

Results

A total of 8 relevant prediction models were included, and 6 models reported the AUC of 0.662-0.830 in the modeling population, which showed good overall applicability but high risk of bias. The main reasons were improper handling of missing values and variable screening, lack of external validation of the model, and insufficient information of overfitting. Age, gender, etiology, initial heart rhythm, EMS arrival time/BLS intervention time, location, bystander CPR, witnessed during sudden arrest, and ACLS duration/compression duration were the most commonly included predictors. Obvious chest injury, body temperature below 33°C, and possible etiologies were predictive factors for ROSC failure in patients with TOHCA. Age, gender, initial heart rhythm, reason for the hospital visit, length of hospital stay, and the location of occurrence in hospital were the predictors of ROSC in IHCA patients.

Conclusion

The performance of current ROSC prediction models varies greatly and has a high risk of bias, which should be selected with caution. Future studies can further optimize and externally validate the existing models.

Assessing the weak links - Necessity and impact of regional cardiac arrest awareness campaigns for laypersons

Introduction

Public knowledge of out-of-hospital cardiac arrest (OHCA), and initiation of basic life support (BLS) is crucial to increase survival in OHCA.

Methods

The study analysed the knowledge and willingness to perform BLS of laypersons passing an AED at a public train station. Interviewees were recruited at two time points before and after a four year-long structured regional awareness campaign, which focused on call, compress, shock in a mid-size European city (270,000 inhabitants). Complete BLS was defined as multiple responses for call for help; initiation of chest compressions; and usage of an AED, without mentioning recovery position. Minimal BLS was defined as call for help and initiation of chest compressions.

Results

A total of 784 persons were interviewed, 257 at baseline and 527 post-campaign. Confronted with a fictional OHCA, at baseline 8.5% of the interviewees spontaneously mentioned actions for complete BLS and 17.9% post-campaign (p = 0.009). An even larger increase in knowledge was seen in minimal BLS (34.6% vs 60.6%, p < 0.001).

Conclusion

After a regional cardiac arrest awareness campaign, we found an increase in knowledge of BLS actions in the lay public. However, our investigation revealed severe gaps in BLS knowledge, possibly resulting in weak first links of the chain of survival.

Out-of-Hospital Cardiac Arrest Bystander Defibrillator Search Time and Experience With and Without Directional Assistance: A Randomized Simulation Trial in a Community Setting

INTRODUCTION

Probability of survival after out-of-hospital cardiac arrest (OHCA) doubles when a bystander initiates cardiopulmonary resuscitation and uses an automated external defibrillator (AED) rapidly. National, state, and community efforts have increased placement of AEDs in public spaces; however, bystander AED use remains less than 2% in the United States. Little is known about the effect of giving bystanders directional assistance to the closest public access AED.

METHODS

We conducted 35 OHCA simulations using a life-sized manikin with participants aged 18 through 65 years who searched for public access AEDs in 5 zones on a university campus. Zones varied by challenges to pedestrian AED acquisition and number of fixed AEDs. Participants completed 2 searches-first unassisted and then with verbal direction to the closest AED-and we compared AED delivery times. We conducted pretest and posttest surveys.

RESULTS

In all 5 zones, the median time from simulated OHCA onset to AED delivery was lower when the bystander received directional assistance. Time savings (minutes:seconds) varied by zone, ranging from a median of 0:53 (P = 0.14) to 3:42 (P = 0.02). Only 3 participants immediately located the closest AED without directional assistance; more than half reported difficulty locating an AED.

CONCLUSIONS

These findings may inform strategies to ensure that AEDs are consistently marked and placed in visible, accessible locations. Continued emphasis on developing strategies to improve lay bystanders' ability to locate and use AEDs may improve AED retrieval times and OHCA outcomes.

Impact of Using Drones in Emergency Medicine: What Does the Future Hold?

The use of unmanned aerial vehicles or "drones" has expanded in the last decade, as their technology has become more sophisticated, and costs have decreased. They are now used routinely in farming, environmental surveillance, public safety, commercial product delivery, recreation, and other applications. Health-related applications are only recently becoming more widely explored and accepted. The use of drone technology in emergency medicine is especially promising given the need for a rapid response to enhance patient outcomes. The purpose of this paper is to describe some of the main current and expanding applications of drone technology in emergency medicine and to describe challenges and future opportunities. Current applications being studied include delivery of defibrillators in response to out-of-hospital cardiac arrest, blood and blood products in response to trauma, and rescue medications. Drones are also being studied and actively used in emergency response to search and rescue operations as well as disaster and mass casualty events. Current challenges to expanding their use in emergency medicine and emergency medical system (EMS) include regulation, safety, flying conditions, concerns about privacy, consent, and confidentiality, and details surrounding the development, operation, and maintenance of a medical drone network. Future research is needed to better understand end user perceptions and acceptance. Continued technical advances are needed to increase payload capacities, increase flying distances, and integrate drone networks into existing 9-1-1 and EMS systems. Drones are a promising technology for improving patient survival, outcomes, and quality of life, particularly for those in areas that are remote or that lack funds or infrastructure. Their cost savings compared with ground transportation alone, speed, and convenience make them particularly applicable in the field of emergency medicine. Research to date suggests that use of drones in emergency medicine is feasible, will be accepted by the public, is cost-effective, and has broad application.

Risk prediction models for out-of-hospital cardiac arrest outcomes in England

AIMS

The out-of-hospital cardiac arrest (OHCA) outcomes project is a national research registry. One of its aims is to explore sources of variation in OHCA survival outcomes. This study reports the development and validation of risk prediction models for return of spontaneous circulation (ROSC) at hospital handover and survival to hospital discharge.

METHODS AND RESULTS

The study included OHCA patients who were treated during 2014 and 2015 by emergency medical services (EMS) from seven English National Health Service ambulance services. The 2014 data were used to identify important variables and to develop the risk prediction models, which were validated using the 2015 data. Model prediction was measured by area under the curve (AUC), Hosmer-Lemeshow test, Cox calibration regression, and Brier score. All analyses were conducted using mixed-effects logistic regression models. Important factors included age, gender, witness/bystander cardiopulmonary resuscitation (CPR) combined, aetiology, and initial rhythm. Interaction effects between witness/bystander CPR with gender, aetiology and initial rhythm and between aetiology and initial rhythm were significant in both models. The survival model achieved better discrimination and overall accuracy compared with the ROSC model (AUC = 0.86 vs. 0.67, Brier score = 0.072 vs. 0.194, respectively). Calibration tests showed over- and under-estimation for the ROSC and survival models, respectively. A sensitivity analysis individually assessing Index of Multiple Deprivation scores and location in the final models substantially improved overall accuracy with inconsistent impact on discrimination.

CONCLUSION

Our risk prediction models identified and quantified important pre-EMS intervention factors determining survival outcomes in England. The survival model had excellent discrimination.

Deep Neural Network Approach for Continuous ECG-Based Automated External Defibrillator Shock Advisory System During Cardiopulmonary Resuscitation

Background Because chest compressions induce artifacts in the ECG, current automated external defibrillators instruct the user to stop cardiopulmonary resuscitation (CPR) while an automated rhythm analysis is performed. It has been shown that minimizing interruptions in CPR increases the chance of survival. Methods and Results The objective of this study was to apply a deep-learning algorithm using convolutional layers, residual networks, and bidirectional long short-term memory method to classify shockable versus nonshockable rhythms in the presence and absence of CPR artifact. Forty subjects' data from Physionet with 1131 shockable and 2741 nonshockable samples contaminated with 43 different CPR artifacts that were acquired from a commercial automated external defibrillator during asystole were used. We had separate data as train and test sets. Using our deep neural network model, the sensitivity and specificity of the shock versus no-shock decision for the entire data set over the 4-fold cross-validation sets were 95.21% and 86.03%, respectively. This result was based on the training and testing of the model using ECG data in both the presence and the absence of CPR artifact. For ECG without CPR artifact, the sensitivity was 99.04% and the specificity was 95.2%. A sensitivity of 94.21% and a specificity of 86.14% were obtained for ECG with CPR artifact. In addition to 4-fold cross-validation sets, we also examined leave-one-subject-out validation. The sensitivity and specificity for the case of leave-one-subject-out validation were 92.71% and 97.6%, respectively. Conclusions The proposed trained model can make shock versus nonshock decision in automated external defibrillators, regardless of CPR status. The results meet the American Heart Association's sensitivity requirement (>90%).

Using firefighters as medical first responders to shorten response time in rural areas in Sweden

OBJECTIVE

To map out and describe an earlier response by using firefighters as medical first responders on while waiting for the ambulance and first incident person assignments focusing on frequency, event time and survival >30 days after performed cardiopulmonary resuscitation.

DESIGN

Retrospective descriptive design.

SETTING

Ambulance service in a county of southern Sweden with a population of 200 000 inhabitants (23/km² ).

PARTICIPANTS

Data were collected from four data systems within different organizations; emergency medical communication centre, fire deparment, ambulance services and conty hospital analysis unit.

MAIN OUTCOME MEASURE(S)

Data from 600 while waiting for the ambulance assignments, whereof 120 with first incident person present, collected between 1 January 2012 and 31 December 2016. Between 1 June 2014 and 1 October 2015, the two fire departments were dually dispatched on out-of-hospital cardiac arrests.

RESULTS

Three main findings were made: there was a prolonged process time for dispatching fire fighters on while waiting for the ambulance assignments. Dual dispatches did not shorten the process time for dispatching full-time firefighters, and, in a majority of while waiting for the ambulance assignments where cardiopulmonary resuscitation was performed, firefighters or first incident persons arrived first on the scene.

CONCLUSION

Minimising every minute that delays the performance of life-saving actions is crucial. By dispatching firefighters on while waiting for the ambulance assignments in rural areas, the response time in a majority of assignments was shortened. However, there was substantial delay in dispatching firefighters due to prolonged process time at the emergency medical communication centre. The emergency medical communication centre operator's ability to quickly assess the need for while waiting for the ambulance assignments plays a crucial role in the chain of survival.

Towards the Prediction of Rearrest during Out-of-Hospital Cardiac Arrest

A secondary arrest is frequent in patients that recover spontaneous circulation after an out-of-hospital cardiac arrest (OHCA). Rearrest events are associated to worse patient outcomes, but little is known on the heart dynamics that lead to rearrest. The prediction of rearrest could help improve OHCA patient outcomes. The aim of this study was to develop a machine learning model to predict rearrest. A random forest classifier based on 21 heart rate variability (HRV) and electrocardiogram (ECG) features was designed. An analysis interval of 2 min after recovery of spontaneous circulation was used to compute the features. The model was trained and tested using a repeated cross-validation procedure, on a cohort of 162 OHCA patients (55 with rearrest). The median (interquartile range) sensitivity (rearrest) and specificity (no-rearrest) of the model were 67.3% (9.1%) and 67.3% (10.3%), respectively, with median areas under the receiver operating characteristics and the precision–recall curves of 0.69 and 0.53, respectively. This is the first machine learning model to predict rearrest, and would provide clinically valuable information to the clinician in an automated way.

Predictive model of return of spontaneous circulation among patients with out-of-hospital cardiac arrest in Thailand: The WATCH-CPR Score

BACKGROUND

Out-of-hospital cardiac arrest is an emergency that requires immediate management to save lives. However, some predictive scores for the immediate outcomes of patients with out-of-hospital cardiac arrest are difficult to use in clinical practice.

AIMS

This study aimed to identify predictors of sustained return of spontaneous circulation and to develop a predictive score.

METHODS

This prospective observational study evaluated sustained return of spontaneous circulation among out-of-hospital cardiac arrest patients in a Thai emergency department between July 2014 and March 2018. The baseline characteristics and prehospital and hospital findings were analysed.

RESULTS

Of 347 patients, 126 (36.3%) had sustained return of spontaneous circulation and 20 (5.8%) were discharged. Witnessed arrest (odds ratio = 2.9, 95% confidence interval 1.3-6.2), time from arrest to chest compression <15 min (odds ratio = 3.0, 95% confidence interval 1.3-7.0) and chest compression duration <30 min (odds ratio = 15.6, 95% confidence interval 8.7-28.0) predicted sustained return of spontaneous circulation; these were developed into the WATCH-CPR (Witnessed Arrest, Time from arrest to CHest compression-CPR duration) score. A score of ≥2 was optimal for predicting sustained return of spontaneous circulation, which provided an area under the receiver operating characteristic of 0.775 (95% confidence interval 0.724-0.825) and a sensitivity of 72.2% (95% confidence interval 63.4-79.6%) and specificity of 76.0% (95% confidence interval 69.8-81.4%).

CONCLUSIONS

The factors including witnessed arrest, time from arrest to chest compression and chest compression duration were developed as the WATCH-CPR score for predicting sustained return of spontaneous circulation among patients with out-of-hospital cardiac arrest.

Knowledge and Attitudes toward Basic Life Support among Medical Students in Oman

Background

This study aimed to assess the level of knowledge regarding the basic life support (BLS) and attitudes related to BLS training and to identify the factors affecting these among medical students in Oman.

Materials and methods

This prospective cross-sectional questionnaire-based study was carried out during the period July 2017 to February 2018 at Medical College of Sultan Qaboos University, Muscat, Oman. Validated questionnaires in English were distributed among undergraduate medical students from 1st to 7th years.

Results

A total of 304 medical students completed the questionnaire with a response rate of 82.7%. The mean knowledge score of the participants was slightly high (5.5 ± 2.1) and median score of 5. About 53.6% of the participants had insufficient knowledge level. The scores increased with increase in the year of training. More than half (64.5%) of the participants had no previous BLS training. Students who attended previous BLS training showed higher knowledge scores (p < 0.001). Majority of the participants (97.4%) supported including of BLS in the undergraduate medical curriculum. Majority of the students (74%) were not reluctant to perform BLS on a stranger, although there was some reluctance among the female students.

Conclusion

Our findings show that medical students in Oman had insufficient knowledge about BLS. However, they showed positive attitudes toward BLS training and were not reluctant to provide BLS to a stranger if required. These highlights the importance to provide sufficient BLS training for medical students early in their course.

How to cite this article

Albadi S, Al-Hadi H, Nadar SK. Knowledge and Attitudes toward Basic Life Support among Medical Students in Oman. Indian J Crit Care Med 2020;24(7):599–600.

First-response treatment after out-of-hospital cardiac arrest: a survey of current practices across 29 countries in Europe

Background

In Europe, survival rates after out-of-hospital cardiac arrest (OHCA) vary widely. Presence/absence and differences in implementation of systems dispatching First Responders (FR) in order to arrive before Emergency Medical Services (EMS) may contribute to this variation. A comprehensive overview of the different types of FR-systems used across Europe is lacking.

Methods

A mixed-method survey and information retrieved from national resuscitation councils and national EMS services were used as a basis for an inventory. The survey was sent to 51 OHCA experts across 29 European countries.

Results

Forty-seven (92%) OHCA experts from 29 countries responded to the survey. More than half of European countries had at least one region with a FR-system. Four categories of FR types were identified: (1) firefighters (professional/voluntary); (2) police officers; (3) citizen-responders; (4) others including off-duty EMS personnel (nurses, medical doctors), taxi drivers. Three main roles for FRs were identified: (a) complementary to EMS; (b) part of EMS; (c) instead of EMS. A wide variation in FR-systems was observed, both between and within countries.

Conclusions

Policies relating to FRs are commonly implemented on a regional level, leading to a wide variation in FR-systems between and within countries. Future research should focus on identifying the FR-systems that most strongly influence survival. The large variation in local circumstances across regions suggests that it is unlikely that there will be a ‘one-size fits all’ FR-system for Europe, but examining the role of FRs in the Chain of Survival is likely to become an increasingly important aspect of OHCA research.

The effect of automatic external defibrillator with a real-time feedback on quality of bystander cardiopulmonary resuscitation: A before-and-after simulation study

High-quality bystander cardiopulmonary resuscitation (CPR) and early defibrillation in the community are important for survival in out-of hospital-cardiac-arrest, but maintaining the quality of CPR in bystanders is difficult. We aimed to determine the effect of an automated external defibrillator (AED) with real-time feedback on the quality of bystander CPR in a community setting. A before-and-after simulation study was designed. Trainees of basic life support education were recruited for the simulation experiment. Each team consisted of two bystanders with different roles (initial witness and CPR supporter). 82 teams performed simulation scenarios with the real-time feedback function of AED disabled initially, and then repeated it with feedback function enabled. Quality measures of chest compression depth and no-flow fraction were compared between each of the two simulation scenarios. CPR quality data from 82 teams were analysed. The mean percentage of chest compressions with adequate depth was significantly higher in simulations with real-time feedback (78.1% vs. 89.3%, p < 0.01). Similarly, no-flow fractions were lower in simulation scenarios with real-time feedback (32.0% vs. 30.3% p = 0.05). In a subgroup with the lowest percentage of adequate depth performance in the initial simulation without real-time feedback, a mean increase of 47.7% (95% CI 31.3-64.0) in the fraction of chest compressions with adequate depth was seen with real-time feedback. Use of an AED with real-time feedback improves the quality of bystander CPR in a simulated community setting. The positive effect of real-time feedback is greatest among people with a low level of CPR skill.

Circumstances, outcome and quality of cardiopulmonary resuscitation by lifeboat crews

BACKGROUND

Little is known regarding circumstances, outcomes and quality of cardiopulmonary resuscitation (CPR) and the use of automated external defibrillators (AEDs) performed by operational lifeboat crews. Our aim is to evaluate circumstances, outcomes and quality of CPR performed by the Royal Dutch Lifeboat Institution (KNRM) in out-of-hospital cardiac arrest (OHCA).

METHODS

The internal KNRM database has been used to identify and analyse all OHCA cases between July 2011 and December 2017. A limited set of AED data was available to study the quality of CPR.

RESULTS

In 37 patients the lifeboat crew members have performed CPR, of which 29 (78.4%) occurred under hostile conditions. The median response time to arrive at the location was 15min. In 11 (29.7%) patients return of spontaneous circulation was achieved at any moment during CPR and 3 (8.1%) patients were still alive after one month. The lifeboat AED was used in 12 patients. Their recordings show a high median compression frequency (120, IQR 111-131) and prolonged median interruption periods (pre-analysis pause 11s (IQR 10-13), post-analysis pause 4s (IQR 3-8), pre-shock pause 24s (IQR 19-26), post-shock pause 6s (IQR 6-11), ventilation pause 6s (IQR 4-8) and other pauses 9s (IQR 4-17)).

CONCLUSIONS

Compared to most out-of-hospital resuscitations, resuscitations by lifeboat crews have a low incidence, occur under difficult circumstances and in a younger population. AED's on lifeboats have not contributed to any of the survivals. Analysis of AED information can be used to study the quality of CPR and provide input for improving future training of lifeboat crews.

Maternal cardiac arrest in the Netherlands: A nationwide surveillance study

BACKGROUND

Maternal cardiac arrest is a complex and demanding clinical situation requiring a well-attuned team effort of healthcare workers of multiple disciplines. A recent report on maternal cardiac arrest in the United Kingdom reported a rise in incidence over a span of 10 years, while maternal mortality increased in the United States between 2000 and 2014. However, reported causes of maternal cardiac arrest differed between both countries.

OBJECTIVE(S)

To determine the incidence, causes and management of maternal cardiac arrest in the Netherlands and compare incidence with previous estimates in the Netherlands and the United Kingdom.

STUDY DESIGN

Using the Netherlands Obstetric Surveillance System, all Dutch cases of maternal cardiac arrest during a three-year period (2013-2016) were prospectively collected. Complete casefile copies were obtained for analysis. Main outcome measures were incidence of maternal cardiac arrest and cardiac arrest in pregnancy, use of perimortem caesarean section if appropriate and maternal death.

RESULTS

The monthly card return rate was 97%; 18 women with cardiac arrest during pregnancy and 20 postpartum met the inclusion criteria. Incidence of maternal cardiac arrest was 7.6 per 100,000 pregnancies and 3.6 per 100,000 pregnancies excluding postpartum maternal cardiac arrest. Main causes were pulmonary embolism (n = 9), major obstetric hemorrhage (n = 7) and amniotic fluid embolism (n = 6). Aortocaval compression relief and perimortem caesarean section were performed in 9/14 (29%) and 11/14 (79%) respectively in pregnancies 20 weeks gestational age onwards. Twenty-two women died, representing a case fatality rate of 58% (95% CI 42-72%).

CONCLUSION(S)

There is a higher incidence of cardiac arrest in pregnancy compared to both previous estimates in the Netherlands and recently established figures in the United Kingdom. Main causes of maternal cardiac arrest are potentially preventable and/or treatable complications of pregnancy. Insufficient use of critical elements of obstetric resuscitation identifies the need for enhanced obstetric emergency training for obstetric and non-obstetric first responders.

Peers versus professional training of basic life support in Syria: a randomized controlled trial

BACKGROUND

Peer training has been identified as a useful tool for delivering undergraduate training in basic life support (BLS) which is fundamental as an initial response in cases of emergency. This study aimed to (1) Evaluate the efficacy of peer-led model in basic life support training among medical students in their first three years of study, compared to professional-led training and (2) To assess the efficacy of the course program and students' satisfaction of peer-led training.

METHODS

A randomized controlled trial with blinded assessors was conducted on 72 medical students from the pre-clinical years (1st to 3rd years in Syria) at Syrian Private University. Students were randomly assigned to peer-led or to professional-led training group for one-day-course of basic life support skills. Sixty-four students who underwent checklist based assessment using objective structured clinical examination design (OSCE) (practical assessment of BLS skills) and answered BLS knowledge checkpoint-questionnaire were included in the analysis.

RESULTS

There was no statistically significant difference between the two groups in delivering BLS skills to medical students in practical (P = 0.850) and BLS knowledge questionnaire outcomes (P = 0.900). Both groups showed statistically significant improvement from pre- to post-course assessment with significant statistical difference in both practical skills and theoretical knowledge (P-Value < 0.001). Students were satisfied with the peer model of training.

CONCLUSION

Peer-led training of basic life support for medical students was beneficial and it provided a quality of education which was as effective as training conducted by professionals. This method is applicable and desirable especially in poor-resource countries and in crisis situation.

Emerging and Future Technologies in Out-of-Hospital Cardiac Arrest Care

The care for victims of out-of-hospital cardiac arrest is evolving and will be influenced by future and emerging technologies that will play a role in the systems of care for these patients. Recent advances in extracorporeal life support and point-of-care ultrasound imaging, both in-hospital and out-of-hospital, may offer a therapeutic solution in some systems for patients with refractory or recurrent cardiac arrest. Drones capable of delivering automated external defibrillators to the scene of an out-of-hospital cardiac arrest, advances in digital and mobile technologies to notify and leverage bystander response, and wearable life detection technologies may improve survival.

Witnessed out-of-hospital cardiac arrest- effects of emergency dispatch recognition

BACKGROUND

Survival from an out-of-hospital cardiac arrest (OHCA) depends on the sequence of interventions in "the chain of survival". If OHCA is recognized in the emergency medical communication centre (EMCC), the proper emergency medical service (EMS) should be dispatched and cardiopulmonary resuscitation (CPR) instructions should be given to a bystander. The study aimed to examine the impact of OHCA recognition in the EMCC on survival rates and the main elements of the chain of survival.

METHODS

Data from the Helsinki University Hospital's registry of OHCA patients between 1997 and 2013 were studied. Altogether, 2054 EMCC-handled and bystander-witnessed OHCA proven events of cardiac origin were analysed.

RESULTS

In 80.5% of the victims, two EMS units were correctly dispatched and the OHCA was classified as recognized. Achieved return of spontaneous circulation (ROSC) and survival to hospital discharge were 49% and 23%, respectively, if cardiac arrest was recognized by the EMCC and 40% and 16% when it was not (P = 0.003 and 0.002). Dispatchers gave CPR instructions in 60% of the recognized OHCA cases. Bystander-performed CPR increased over time and was given in 58% of the recognized OHCAs and also in 17% of the unrecognized events. EMS delays were shorter if OHCA was recognized as opposed to unrecognized (8 min with an IQR 6.5-10 min vs. 9 min with an IQR 6.5-11 min; P = 0.001).

CONCLUSIONS

Recognition of OHCA by the EMCC was significantly associated with an increased rate of bystander-performed CPR, reduced EMS response time, and increased OHCA patient ROSC and survival rates.

The Comparison between two Methods of Basic Life Support Instruction: Video Self-Instruction versus Traditional Method

Introduction

Medical education is changing and evolving. Teachers need to re-evaluate their medical teaching practice to enhance student learning. The data about the ideal training method of Basic Life Support (BLS) is lacking. The goal of this study was to analyse the use and performance of video self-instruction (VSI) method in BLS, in order to develop an efficient BLS training method.

Methods

Eighty-one undergraduate medical interns were enrolled in a prospective clinical study in 2011. They were divided into VSI group and traditional group. We provided the first group with a DVD containing a 20-minute training video while the second group took part in a 4-hour training class of BLS. Subjects participated in a pre-test and post-test based on 2010 American Heart Association Resuscitation guideline.

Results

The average scores of VSI group and the traditional group before training were 8.85±2.42 and 8.57±2.22 respectively (p=0.592). After training, the average scores of the VSI and the traditional group were 20.24±0.83 and 18.05±1.86 respectively. VSI group achieved slightly better scores compared with the traditional group (p<0.001).

Conclusions

Training through VSI achieves more satisfying results than the traditional lecture method. VSI method can be considered a useful technique in undergraduate educational programs. Developing VSI can increase significantly the access to the BLS training. (Hong Kong j.emerg.med. 2015;22:291-296)

Shocking the system: AEDs in military resuscitation

Automated external defibrillator (AED) devices have been in routine clinical use since the early 1990s to deliver life-saving shocks to appropriate patients in non-clinical environments. As expectations of survival from out-of-hospital cardiac arrest increase, and evidence incontrovertibly points to reduced timelines as the most crucial factor in achieving return of spontaneous circulation, questions regarding the availability and location of AEDs in the UK military need to be readdressed. This article explores the background of AEDs and reviews their history, life-saving potential and defines current and best practice. It goes on to review the evidence surrounding training and looks to identify knowledge gaps that might be addressed effectively by future research. Finally, it makes recommendations regarding training, availability of AEDs on military bases and locations most likely to deliver good outcomes for military personnel in the future.

Consciousness, unconsciousness and death in the context of slaughter. Part II. Evaluation methods

This second review describes indicators of consciousness and unconsciousness that can be used in the abattoir. These indicators evaluate different aspects of cerebral functioning, but only indirectly. It is therefore necessary to monitor several indicators. Animals are considered unconscious if signs of consciousness are absent, and signs of unconsciousness are present. Given that the unconscious state may be reversible it is further necessary to monitor these indicators until the end of bleeding. The techniques used to diagnose brain death in humans cannot be used in the slaughterhouse. Under field conditions, at the end of bleeding, the absence of breathing and of brainstem reflexes and the adequacy of the exsanguination are verified. If these three aspects are confirmed, in the context of the slaughterhouse and at this stage of the slaughter process the loss of vital functions is irreversible and the animal can be considered dead.

Feedback on the Rate and Depth of Chest Compressions during Cardiopulmonary Resuscitation Using Only Accelerometers

Background

Quality of cardiopulmonary resuscitation (CPR) is key to increase survival from cardiac arrest. Providing chest compressions with adequate rate and depth is difficult even for well-trained rescuers. The use of real-time feedback devices is intended to contribute to enhance chest compression quality. These devices are typically based on the double integration of the acceleration to obtain the chest displacement during compressions. The integration process is inherently unstable and leads to important errors unless boundary conditions are applied for each compression cycle. Commercial solutions use additional reference signals to establish these conditions, requiring additional sensors. Our aim was to study the accuracy of three methods based solely on the acceleration signal to provide feedback on the compression rate and depth.

Materials and Methods

We simulated a CPR scenario with several volunteers grouped in couples providing chest compressions on a resuscitation manikin. Different target rates (80, 100, 120, and 140 compressions per minute) and a target depth of at least 50 mm were indicated. The manikin was equipped with a displacement sensor. The accelerometer was placed between the rescuer’s hands and the manikin’s chest. We designed three alternatives to direct integration based on different principles (linear filtering, analysis of velocity, and spectral analysis of acceleration). We evaluated their accuracy by comparing the estimated depth and rate with the values obtained from the reference displacement sensor.

Results

The median (IQR) percent error was 5.9% (2.8–10.3), 6.3% (2.9–11.3), and 2.5% (1.2–4.4) for depth and 1.7% (0.0–2.3), 0.0% (0.0–2.0), and 0.9% (0.4–1.6) for rate, respectively. Depth accuracy depended on the target rate (p < 0.001) and on the rescuer couple (p < 0.001) within each method.

Conclusions

Accurate feedback on chest compression depth and rate during CPR is possible using exclusively the chest acceleration signal. The algorithm based on spectral analysis showed the best performance. Despite these encouraging results, further research should be conducted to asses the performance of these algorithms with clinical data.

A new method without reference channels used for ventricular fibrillation detection during cardiopulmonary resuscitation

Ventricular fibrillation (VF) is observed as the initial rhythm in the majority of patients suffering from sudden cardiac arrest. It is vitally important to accurately recognize the initial VF rhythm and then implement electrical defibrillation. However, artifacts produced by chest compression during cardiopulmonary resuscitation (CPR) make the VF detection algorithms utilized by current automated external defibrillators (AEDs) unreliable. CPR must be traditionally interrupted for a reliable diagnosis. However, interruptions in chest compression have a deleterious effect on the success of defibrillation. The elimination of the CPR artifacts would enable compressions to continue during AED VF detection and thereby increase the likelihood of resuscitation success. We have estimated a model of this artifact by adaptively incorporating noise-assisted multivariate empirical mode decomposition (NA-MEMD) and least mean squares (LMS) and then removing the artifact from the corrupted ECGs. The simulation experiment indicated that the CPR artifact could be accurately modeled without any reference channels. We constructed a BP neural network to evaluate the results. A total of 372 VF and 645 normal sinus rhythm (SR) ECG samples were included in the analysis, and 24 CPR artifact signals were used to construct corrupted ECGs. The results indicated that at different SNR levels ranging from 0 to -12 dB, the sensitivity and specificity were always above 95 and 80 %, respectively.

The Use of Automated External Defibrillators in Infants: A Report From the American Red Cross Scientific Advisory Council

OBJECTIVE

Automated external defibrillators (AEDs) have been used successfully in many populations to improve survival for out-of-hospital cardiac arrest. While ventricular fibrillation and pulseless ventricular tachycardia are more prevalent in adults, these arrhythmias do occur in infants. The Scientific Advisory Council of the American Red Cross reviewed the literature on the use of AEDs in infants in order to make recommendations on use in the population.

METHODS

The Cochrane library and PubMed were searched for studies that included AEDs in infants, any external defibrillation in infants, and simulation studies of algorithms used by AEDs on pediatric arrhythmias.

RESULTS

There were 4 studies on the accuracy of AEDs in recognizing pediatric arrhythmias. Case reports (n = 2) demonstrated successful use of AED in infants, and a retrospective review (n = 1) of pediatric pads for AEDs included infants. Six studies addressed defibrillation dosages used. The algorithms used by AEDs had high sensitivity and specificity for pediatric arrhythmias and very rarely recommended a shock inappropriately. The energy doses delivered by AEDs were high, although in the range that have been used in out-of-hospital arrest. In addition, there are data to suggest that 2 to 4 J/kg may not be effective defibrillation doses for many children.

CONCLUSIONS

In the absence of prompt defibrillation for ventricular fibrillation or pulseless ventricular tachycardia, survival is unlikely. Automated external defibrillators should be used in infants with suspected cardiac arrest, if a manual defibrillator with a trained rescuer is not immediately available. Automated external defibrillators that attenuate the energy dose (eg, via application of pediatric pads) are recommended for infants. If an AED with pediatric pads is not available, the AED with adult pads should be used.

The survival benefit of dual dispatch of EMS and fire-fighters in out-of-hospital cardiac arrest may differ depending on population density--a prospective cohort study

BACKGROUND

Outcome after out-of-hospital cardiac arrest (OHCA) varies between contexts. Dual dispatching of fire-fighters or police in addition to emergency medical services (EMS) has the potential to increase survival, but the effect in urban vs. rural areas is unknown. The aim of this study was to determine the effects of dual dispatching on response times and outcome in regions with different population density.

METHODS AND RESULTS

The study design was a prospective cohort study of EMS-treated OHCAs from 2004 (historical controls, only EMS dispatch) and 2006-2009 (intervention, dual dispatch of EMS and fire-fighters), with data on exact geographical coordinates. Patients were divided into four subgroups depending on population density: rural (<250 persons/km2), suburban (250-2999/km2), urban (3000-5999/km2) and downtown (≥6000/km2). Totally, 2513 OHCAs were included (historical controls, n=571 and intervention, n=1942). Median time to arrival of first unit shortened significantly in all subgroups, ranging from 0.8 to 3.2 min, with the main time gain in the rural area. There were significant differences in 30-day survival between the historical controls vs. the intervention group in the suburban population (3.1% vs. 7.0%, p=0.02) and in downtown (4.1 vs. 14.6, p=0.04). In the urban population the difference was 2.7 vs. 6.9% (p=0.06) and in the rural population (4.7 vs. 5.3, p=0.82).

CONCLUSIONS

Dual dispatch of fire-fighters and EMS in OHCA significantly reduced response times in all studied regions. The 30-day survival increased significantly in the downtown and suburban populations, while a limited impact was seen in the rural areas.

Rhythm analysis during cardiopulmonary resuscitation: past, present, and future

Survival from out-of-hospital cardiac arrest depends largely on two factors: early cardiopulmonary resuscitation (CPR) and early defibrillation. CPR must be interrupted for a reliable automated rhythm analysis because chest compressions induce artifacts in the ECG. Unfortunately, interrupting CPR adversely affects survival. In the last twenty years, research has been focused on designing methods for analysis of ECG during chest compressions. Most approaches are based either on adaptive filters to remove the CPR artifact or on robust algorithms which directly diagnose the corrupted ECG. In general, all the methods report low specificity values when tested on short ECG segments, but how to evaluate the real impact on CPR delivery of continuous rhythm analysis during CPR is still unknown. Recently, researchers have proposed a new methodology to measure this impact. Moreover, new strategies for fast rhythm analysis during ventilation pauses or high-specificity algorithms have been reported. Our objective is to present a thorough review of the field as the starting point for these late developments and to underline the open questions and future lines of research to be explored in the following years.

Use of automated external defibrillators in patients with traumatic out-of-hospital cardiac arrest

BACKGROUND

Because out-of-hospital cardiac arrests (OHCAs) due to a major trauma rarely present with shockable rhythms, the potential benefits of using automated external defibrillators (AEDs) at the scene of traumatic OHCAs have not been examined.

METHODS

We conducted an observational, retrospective cohort study using an Utstein-style analysis in Tainan city, Taiwan. The enrollees were adult patients with traumatic OHCAs accessed by emergency medical technicians (EMTs) from January 1, 2004 to December 31, 2010. The exposure was the use or non-use of AEDs at the scene, as determined by the clinical judgment of the EMTs. The primary outcome evaluated was a sustained (≥2h) return of spontaneous circulation (ROSC), and the secondary outcomes were prehospital ROSC, overall ROSC, survival to hospital admission, survival at one month and favorable neurologic status at one month.

RESULTS

A total of 424 patients (313 males) were enrolled, of whom 280 had AEDs applied, and 144 did not. Only 25 (5.9%) patients had received bystander cardiopulmonary resuscitation (CPR), and merely 21 (7.5%) patients in the AED group presented with shockable rhythms. Compared to the non-AED group, the primary and secondary outcomes of the AED group were not significantly different, except for a significantly lower prehospital ROSC rate (1.1% vs. 4.9%, p<0.05). Multivariate analysis showed no significant interactions between the use of AEDs and other key variables. Use of the AED was not associated with sustained ROSC (OR 1.33; 95% CI 0.75-2.38, p=0.33).

CONCLUSIONS

In a community with a low prevalence of shockable rhythms and administration of bystander CPR in patients with traumatic OHCA, we found no significant differences in the sustained ROSC between the AED and the non-AED groups. Considering scene safety and the possible interruption of CPR, we do not encourage the routine use of AEDs at the scene of traumatic OHCAs.