A systematic review of the evidence supporting the use of priority dispatch of emergency ambulances

Symptom-Based Dispatching in an Emergency Medical Communication Centre: Sensitivity, Specificity, and the Area under the ROC Curve

Measuring the performance of emergency medical dispatch tools used in paramedic-staffed emergency medical communication centres (EMCCs) is rarely performed. The objectives of our study were, therefore, to measure the performance and accuracy of Geneva's dispatch system based on symptom assessment, in particular, the performance of ambulance dispatching with lights and sirens (L&S) and to measure the effect of adding specific protocols for each symptom. Methods: We performed a prospective observational study including all emergency calls received at Geneva's EMCC (Switzerland) from 1 January 2014 to 1 July 2019. The risk levels selected during the emergency calls were compared to a reference standard, based on the National Advisory Committee for Aeronautics (NACA) scale, dichotomized to severe patient condition (NACA ≥ 4) or stable patient condition (NACA < 4) in the field. The symptom-based dispatch performance was assessed using a receiver operating characteristic (ROC) curve. Contingency tables and a Fagan nomogram were used to measure the performance of the dispatch with or without L&S. Measurements were carried out by symptom, and a group of symptoms with specific protocols was compared to a group without specific protocols. Results: We found an acceptable area under the ROC curve of 0.7474, 95%CI (0.7448-0.7503) for the 148,979 assessments included in the study. Where the severity prevalence was 21%, 95%CI (20.8-21.2). The sensitivity of the L&S dispatch was 87.5%, 95%CI (87.1-87.8); and the specificity was 47.3%, 95%CI (47.0-47.6). When symptom-specific assessment protocols were used, the accuracy of the assessments was slightly improved. Conclusions: Performance measurement of Geneva's symptom-based dispatch system using standard diagnostic test performance measurement tools was possible. The performance was found to be comparable to other emergency medical dispatch systems using the same reference standard. However, the implementation of specific assessment protocols for each symptom may improve the accuracy of symptom-based dispatch systems.

Safety of Tiered-Dispatch for 911 Calls for Abdominal Pain

Introduction

Many dispatch systems send Advanced Life Support (ALS) resources to patients complaining of abdominal pain even though the majority of these incidents require only Basic Life Support (BLS). With increasing 911-call volume, resource utilization has become more important to ensure that ALS resources are available for time-critical emergencies. In 2015, a large, urban fire department implemented an internally developed, tiered-dispatch system. Under this system, patients reporting a chief complaint of abdominal pain received the closest BLS ambulance dispatched alone emergency if located within three miles of the incident. The objective of this study was to determine the safety of BLS-only dispatch to abdominal pain by determining the frequency of time-sensitive events.

Methods

This was a retrospective review of electronic health records of one emergency medical service provider agency from May 2015–2018. Inclusion criteria were a chief complaint of abdominal pain from a first- or second-party caller, age over 15, and the patient was reported to be alert and breathing normally. The primary outcome was the prevalence of time-sensitive events, including cardiopulmonary resuscitation (CPR), defibrillation, or airway management. Secondary outcomes were hypotension (systolic blood pressure < 90 mmHg); or a prehospital 12 lead-electrocardiogram (ECG) demonstrating ST-elevation myocardial infarction (STEMI) criteria or a wide complex arrhythmia. Descriptive statistics were used.

Results

During the study period, there were 1,220,820 EMS incidents, of which 33,267 (2.72%) met inclusion criteria. The mean age was 49.9 years (range 16–111, standard deviation [SD] 19.6); 14,556 patients (56.2%) were female. Time-sensitive events occurred in seven cases (0.021%), mean age was 75.3 years (range 30–86, SD18.7); 85.7% were female. Airway management was required in seven cases (0.021%), CPR in six cases (0.018%), and defibrillation in one case (0.003%). Two of the seven (28.6%) cases involved dispatch protocol deviations. Hypotension was present in 240 (0.72%) cases; six (0.018%) cases had 12-lead ECGs meeting STEMI criteria; and no cases demonstrated wide complex arrhythmia.

Conclusion

Among adult 911 patients with a dispatch chief complaint of abdominal pain, time-sensitive events were exceedingly rare. Dispatching a BLS ambulance alone appears to be safe.

Does the prehospital National Early Warning Score predict the short-term mortality of unselected emergency patients?

OBJECTIVES

The prehospital research field has focused on studying patient survival in cardiac arrest, as well as acute coronary syndrome, stroke, and trauma. There is little known about the overall short-term mortality and its predictability in unselected prehospital patients. This study examines whether a prehospital National Early Warning Score (NEWS) predicts 1-day and 30-day mortalities.

METHODS

Data from all emergency medical service (EMS) situations were coupled to the mortality data obtained from the Causes of Death Registry during a six-month period in Northern Finland. NEWS values were calculated from first clinical parameters obtained on the scene and patients were categorized to the low, medium and high-risk groups accordingly. Sensitivities, specificities, positive predictive values (PPVs), negative predictive values (NPVs), and likelihood ratios (PLRs and NLRs) were calculated for 1-day and 30-day mortalities at the cut-off risks.

RESULTS

A total of 12,426 EMS calls were included in the study. The overall 1-day and 30-day mortalities were 1.5 and 4.3%, respectively. The 1-day mortality rate for NEWS values ≤12 was lower than 7% and for values ≥13 higher than 20%. The high-risk NEWS group had sensitivities for 1-day and 30-day mortalities 0.801 (CI 0.74-0.86) and 0.42 (CI 0.38-0.47), respectively.

CONCLUSION

In prehospital environment, the high risk NEWS category was associated with 1-day mortality well above that of the medium and low risk NEWS categories. This effect was not as noticeable for 30-day mortality. The prehospital NEWS may be useful tool for recognising patients at early risk of death, allowing earlier interventions and responds to these patients.

A comparison of two emergency medical dispatch protocols with respect to accuracy

Background

Emergency medical dispatching should be as accurate as possible in order to ensure patient safety and optimize the use of ambulance resources. This study aimed to compare the accuracy, measured as priority level, between two Swedish dispatch protocols – the three-graded priority protocol Medical Index and a newly developed prototype, the four-graded priority protocol, RETTS-A.

Methods

A simulation study was carried out at the Emergency Medical Communication Centre (EMCC) in Stockholm, Sweden, between October and March 2016. Fifty-three voluntary telecommunicators working at SOS Alarm were recruited nationally. Each telecommunicator handled 26 emergency medical calls, simulated by experienced standard patients. Manuscripts for the scenarios were based on recorded real-life calls, representing the six most common complaints. A cross-over design with 13 + 13 calls was used. Priority level and medical condition for each scenario was set through expert consensus and used as gold standard in the study.

Results

A total of 1293 calls were included in the analysis. For priority level, n = 349 (54.0%) of the calls were assessed correctly with Medical Index and n = 309 (48.0%) with RETTS-A (p = 0.012). Sensitivity for the highest priority level was 82.6% (95% confidence interval: 76.6–87.3%) in the Medical Index and 54.0% (44.3–63.4%) in RETTS-A. Overtriage was 37.9% (34.2–41.7%) in the Medical Index and 28.6% (25.2–32.2%) in RETTS-A. The corresponding proportion of undertriage was 6.3% (4.7–8.5%) and 23.4% (20.3–26.9%) respectively.

Conclusion

In this simulation study we demonstrate that Medical Index had a higher accuracy for priority level and less undertriage than the new prototype RETTS-A. The overall accuracy of both protocols is to be considered as low. Overtriage challenges resource utilization while undertriage threatens patient safety. The results suggest that in order to improve patient safety both protocols need revisions in order to guarantee safe emergency medical dispatching.

Medical priority dispatch codes-comparison with National Early Warning Score

Background

In Finland, calls for emergency medical services are prioritized by educated non-medical personnel into four categories—from A (highest risk) to D (lowest risk)—following a criteria-based national dispatch protocol. Discrepancies in triage may result in risk overestimation, leading to inappropriate use of emergency medical services units and to risk underestimation that can negatively impact patient outcome. To evaluate dispatch protocol accuracy, we assessed association between priority assigned at dispatch and the patient’s condition assessed by emergency medical services on the scene using an early warning risk assessment tool.

Methods

Using medical charts, clinical variables were prospectively recorded and evaluated for all emergency medical services missions in two hospital districts in Northern Finland during 1.1.2014–30.6.2014. Risk assessment was then re-categorized as low, medium, or high by calculating the National Early Warning Score (NEWS) based on the patients’ clinical variables measured at the scene.

Results

A total of 12,729 emergency medical services missions were evaluated, of which 616 (4.8%) were prioritized as A, 3193 (25.1%) as B, 5637 (44.3%) as C, and 3283 (25.8%) as D. Overall, 67.5% of the dispatch missions were correctly estimated according to NEWS. Of the highest dispatch priority missions A and B, 76.9 and 78.3%, respectively, were overestimated. Of the low urgency missions (C and D), 10.7% were underestimated; 32.0% of the patients who were assigned NEWS indicating high risk had initially been classified as low urgency C or D priorities at the dispatch.

Discussion and conclusion

The present results show that the current Finnish medical dispatch protocol is suboptimal and needs to be further developed. A substantial proportion of EMS missions assessed as highest priority were categorized as lower risk according to the NEWS determined at the scene, indicating over-triage with the protocol. On the other hand, only a quarter of the high risk NEWS patients were classified as the highest priority at dispatch, indicating considerable under-triage with the protocol.

Electronic supplementary material

The online version of this article (doi:10.1186/s13049-016-0336-y) contains supplementary material, which is available to authorized users.

Prehospital triage accuracy in a criteria based dispatch centre

BACKGROUND

Priority dispatch accuracy is a key issue in optimizing the match between patients' medical needs and pre-hospital resources. This study measures the accuracy of a Criteria Based Dispatch (CBD) system, by evaluating discrepancies between dispatch priorities and ambulance crews' severity evaluations.

METHODS

This is a retrospective study conducted from January 2011 to December 2011. We ruled that a National Advisory Committee for Aeronautics (NACA) score > 3 (injuries/diseases which can possibly lead to deterioration of vital signs) to 7 (lethal injuries/ diseases) should require a priority dispatch with lights and siren (L&S), while NACA scores < 4 should require a priority dispatch without L&S. Over triage was defined as the proportion of L&S dispatches with a NACA score < 4, and under triage as the proportion of dispatches without L&S with a NACA score > 3.

RESULTS

There were 29,008 primary missions in 2011, 1122 were excluded. Of the 15,749 L&S missions, 12,333 patients had a NACA score < 4, leading to an over triage rate of 78 %; 561 missions out of 12,137 missions without L&S had a NACA score > 3, leading to an under triage rate of 4.6 %. Sensitivity was 86 % (95 % confidence interval: 85.6-86.4 %), specificity 48 % (47.4-48.6 %), positive predictive value 21.7 % (21.2-22.2 %), and negative predictive value 95.4 % (95.2-95.6 %).

CONCLUSION

The rates of over triage and under triage in our CBD are 78 and 4.6 % respectively. The lack of consistent or universal metrics is perhaps the most important limitation in dispatch accuracy research. This is mainly due to the large heterogeneity of dispatch systems and prehospital emergency system.

Patient safety in ambulance services: a scoping review

Background

The role of ambulance services has changed dramatically over the last few decades with the introduction of paramedics able to provide life-saving interventions, thanks to sophisticated equipment and treatments available. The number of 999 calls continues to increase, with adverse events theoretically possible with each one. Most patient safety research is based on hospital data, but little is known concerning patient safety when using ambulance services, when things can be very different. There is an urgent need to characterise the evidence base for patient safety in NHS ambulance services.

Objective

To identify and map available evidence relating to patient safety when using ambulance services.

Design

Mixed-methods design including systematic review and review of ambulance service documentation, with areas for future research prioritised using a Delphi process.

Setting and participants

Ambulance services, their staff and service users in UK.

Data sources

A wide range of data sources were explored. Multiple databases, reference lists from key papers and citations, Google and the NHS Confederation website were searched, and experts contacted to ensure that new data were included in the review. The databases MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, Science Direct, Emerald, Education Resources Information Center (ERIC), Applied Social Sciences Index and Abstracts, Social Services Abstracts, Sociological Abstracts, International Bibliography of the Social Sciences (IBSS), PsycINFO, PsycARTICLES, Health Management Information Consortium (HMIC), NHS Evidence, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects (DARE), NHS Economic Evaluation Database (NHS EED),Health Technology Assessment, the FADE library, Current Awareness Service for Health (CASH), OpenDOAR (Directory of Open Access Repositories) and Open System for Information on Grey Literature in Europe (OpenSIGLE) and Zetoc (The British Library's Electronic Table of Contents) were searched from 1 January 1980 to 12 October 2011. Publicly available documents and issues identified by National Patient Safety Agency (NPSA), NHS Litigation Authority (NHSLA) and coroners’ reports were considered. Opinions and perceptions of senior managers, ambulance staff and service users were solicited.

Review methods

Data were extracted from annual reports using two-stage thematic analysis, data from quality accounts were collated with safety priorities tabulated and considered using thematic analysis, NPSA incident report data were collated and displayed comparatively using descriptive statistics, claims reported to NHSLA were analysed to identify number and cost of claims from mistakes and/or poor service, and summaries of coroners’ reports were assessed using thematic analysis to identify underlying safety issues. The depth of analysis is limited by the remit of a scoping exercise and availability of data.

Results

We identified studies exploring different aspects of safety, which were of variable quality and with little evidence to support activities currently undertaken by ambulance services. Adequately powered studies are required to address issues of patient safety in this service, and it appeared that national priorities were what determined safety activities, rather than patient need. There was inconsistency of information on attitudes and approaches to patient safety, exacerbated by a lack of common terminology.

Conclusion

Patient safety needs to become a more prominent consideration for ambulance services, rather than operational pressures, including targets and driving the service. Development of new models of working must include adequate training and monitoring of clinical risks. Providers and commissioners need a full understanding of the safety implications of introducing new models of care, particularly to a mobile workforce often isolated from colleagues, which requires a body of supportive evidence and an inherent critical evaluation culture. It is difficult to extrapolate findings of clinical studies undertaken in secondary care to ambulance service practice and current national guidelines often rely on consensus opinion regarding applicability to the pre-hospital environment. Areas requiring further work include the safety surrounding discharging patients, patient accidents, equipment and treatment, delays in transfer/admission to hospital, and treatment and diagnosis, with a clear need for increased reliability and training for improving handover to hospital.

Funding

The National Institute for Health Research Health Services and Delivery Research programme.

Analysis of emergency medical services triage and dispatch errors by registered nurses in Italy

INTRODUCTION

The major elements of an effective emergency medical services (EMS) system include a single telephone access number, accurate assessment of the urgency of the health problem, and timely dispatch of appropriate personnel and equipment. In Italy, EMS calls are managed by emergency operations centers by registered nurses who have received specialized education in this function. The nurses determine the criticality of the situations and assign an EMS response priority level identified by a color code, ranging from red (very critical) to green (not critical). At times, the severity of a situation may be underestimated, resulting in assignment of a lower EMS response priority and the potential for patient death (code black). The purpose of this study was to analyze factors associated with registered nurse under-triage of EMS calls subsequently found to be associated with deaths, termed "green-black code" cases.

METHODS

We carried out a retrospective qualitative analysis of EMS telephone conversations using Fele's conversation analysis method. The characteristics of green-black code calls were compared with the characteristics of the population of all EMS calls during the study period.

RESULTS

The study patients were older, with a mean age of 81.6 years. The callers were individuals calling on behalf of the patients, rather than the patients themselves. The callers reported symptoms that were not life-threatening. Nurse operators did not always inquire about the patients' vital signs as required by the Medical Priority Dispatch System protocol. The phone conversations were shorter than normal (54.26 seconds vs 65 seconds).

DISCUSSION

Although the importance of dispatch system protocols is wellknown, it is also important that nurse triage operators have proper training to ensure that major parameters such as vital signs and symptomatology are obtained and to reduce caller stress level.

Emergency Nursing Staff Dispatch: Sensitivity and Specificity in Detecting Prehospital Need for Physician Interventions During Ambulance Transport in Rovigo Emergency Ambulance Service, Italy

Introduction

In Italy, administration of medications or advanced procedures dictates the prehospital presence of a physician to initiate treatment. Nursing staff is often used as dispatchers in Italian emergency medical ambulance services. There is little data about nursing dispatch performance in detecting high-acuity patients who need prehospital medications and procedures.

Objective

To determine the ability of a dispatch center staffed by emergency ambulance nurses to detect prehospital need for physician interventions in the context of a semi-rural area Emergency Medical Services system.

Methods

A retrospective analysis of 53,606 calls from the Rovigo Emergency Ambulance Services’ database was undertaken. Physician prehospital interventions were defined as the administration of medications or procedures (advanced airway management and ventilation, pneumothorax decompression, fluid replacement therapy, external defibrillation, cardioversion and pacing). The dispatch codes (assigned by a subjective decision-making process as Red, Yellow, or Green) of all transported prehospital patient calls were matched with an out-of-hospital triage system staffed by clinicians to determine the number of correctly identified prehospital need of physician interventions. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated.

Results

The sensitivity of subjective experience-based nursing dispatch in detecting the need for physician interventions was 78.0% (95% CI, 76.9%-79.1%), with a PPV of 36.6% (95% CI, 35.8%-37.5%). Specificity was 83.8% (95% CI: 83.4%-84.1%), with an NPV of 96.9% (95% CI, 96.8%-97.1%).

Conclusion

A dispatch center staffed by nurses with six years of experience and three months of training correctly identified when not to send a doctor to the scene in the absence of need for physician interventions, using a subjective decision-making process. The nurses staffing the dispatch center also worked in the field. Dispatch center staff were not able to predict when there was no need for physician interventions in high-acuity dispatch code patients, resulting in an over-triage and use of emergency physicians on scene.

LeopardiM, SommacampagnaM.Emergency nursing staff dispatch: sensitivity and specificity in detecting prehospital need for physician interventions during ambulance transport in Rovigo Emergency Ambulance Service, Italy. Prehosp Disaster Med. 2013;28(5):1-6.

The barbados emergency ambulance service: high frequency of nontransported calls

Objectives. There are no published studies on the Barbados Emergency Ambulance Service and no assessment of the calls that end in nontransported individuals. We describe reasons for the nontransport of potential clients. Methods. We used the Emergency Medical Dispatch (Medical Priority Dispatch System) instrument, augmented with five local call types, to collect information on types of calls. The calls were categorised under 7 headings. Correlations between call types and response time were calculated. Results. Most calls were from the category medical (54%). Nineteen (19%) percent of calls were in the non-transported category. Calls from call type Cancelled accounted for most of these and this was related to response time, while Refused service was inversely related (P = 0.01). Conclusions. The Barbados Ambulance Service is mostly used by people with a known illness and for trauma cases. One-fifth of calls fall into a category where the ambulance is not used often due to cancellation which is related to response time. Other factors such as the use of alternative transport are also important. Further study to identify factors that contribute to the non-transported category of calls is necessary if improvements in service quality are to be made.

D ERIVATION OF E MERGENCY M EDICAL S ERVICES D ISPATCH C ODES A SSOCIATED WITH L OW - ACUITY P ATIENTS

OBJECTIVE

To identify emergency medical services (EMS) dispatch codes associated with basic life support (BLS) level of prehospital care, a proxy for low illness acuity.

METHODS

This retrospective cohort study was conducted in an urban city with a single advanced life support level EMS provider. The 911 center was certified in using dispatch protocols from Priority Dispatch Corporation (Salt Lake City, UT). Dispatch data on all transported EMS patients from August 2001 to April 2002 were abstracted. The authors prospectively defined a low-acuity patient as one who received BLS-level care and defined a low-acuity dispatch code as one in which at least 90% of coded patients required only BLS care. For each dispatch code or code group, the authors calculated the fraction of patients who received BLS-level care. For each "A"-level (lowest category) dispatch code group, the fraction of patients receiving BLS-level care was also evaluated.

RESULTS

A total of 19,332 calls met inclusion criteria and were categorized into 118 dispatch codes or code groups. Twenty-eight codes or code groups with 7,801 patients met the authors' definition of low acuity. Overall, 7,394 patients received only BLS care (94.8%, 95% confidence interval: 94.3%-95.3%). Analysis of "A"-level dispatch code groups found BLS use rates of 52.8% to 99.3%.

CONCLUSIONS

Certain dispatch codes are associated with the delivery of BLS-level care, indicating identification of patients likely to be low acuity. These codes are not necessarily "A"-level dispatch codes, which are commonly considered to represent the lowest-acuity patients. Future studies are needed to prospectively validate that these codes do represent low-acuity patients.

Low Acuity EMS Dispatch Criteria Can Reliably Identify Patients without High-Acuity Illness or Injury

OBJECTIVE

This retrospective study evaluated the appropriateness of requests assigned the alpha determinant at the time of dispatch by Emergency Medical Dispatchers using the Medical Priority Dispatch System (MPDS).

METHODS

The primary end point was the proportion of EMS calls assigned the alpha dispatch determinant that resulted in a high-acuity patient encounter. Patient care reports from January 1 to June 30, 2004, were eligible for inclusion; reports with known errors in data entry or those that were not the result of caller interrogation via the 9-1-1 emergency medical dispatch center (EMDC) were excluded. High-acuity patients were defined as those who met trauma triage criteria or received treatment for acute coronary syndrome, respiratory distress, altered mental status, acute stroke, allergic reaction, or abnormal vital signs. Secondary end points included call-processing time, the proportion of included patients who were transported emergently to hospital, and the adherence of the EMDC to National Academy of Emergency Dispatch (NAED) quality assurance guidelines.

RESULTS

There were 23,939 dispatches; 2,703 were recorded as alpha dispatches in the electronic patient care report (ECR), of which 582 were excluded. Twenty-one of 2,121 calls (<1%) meeting inclusion criteria met high-acuity criteria and were considered as inappropriate alpha dispatches. Fourteen of 2,121 (<1%) were transported emergently to the hospital, eight of whom also met the high-acuity criteria. The call-processing time at the 90th percentile was 2 minutes and 29 seconds. The EMDC demonstrated 99% compliance with NAED quality assurance standards.

CONCLUSION

The use of standard MPDS protocols can successfully identify patients who do not demonstrate high-acuity illness or injury more than 99% of the time.

A descriptive analysis of Emergency Medical Service Systems participating in the Resuscitation Outcomes Consortium (ROC) network

BACKGROUND

The optimal Emergency Medical Services (EMS) system characteristics have not been defined, resulting in substantial variability across systems. The Resuscitation Outcomes Consortium (ROC) is a United States-Canada research network that organized EMS agencies from 11 different systems to perform controlled trials in cardiac arrest and life-threatening trauma resuscitation.

OBJECTIVES

To describe EMS systems participating in ROC using a novel framework.

METHODS

Standardized surveys were created by ROC investigators and distributed to each site for completion. These included separate questions for individual hospitals, EMS agencies, and dispatch centers. Results were collated and analyzed by using descriptive statistics.

RESULTS

A total of 264 EMS agencies, 287 hospitals, and 154 dispatch centers were included. Agencies were described with respect to the type (fire-based, non-fire governmental, private), transport status (transport/non-transport), and training level (BLS/ALS). Hospitals were described with regard to their trauma designation and the presence of electrophysiology and cardiac catheterization laboratories. Dispatch center characteristics, including primary versus secondary public safety answering point (PSAP) status and the use of prearrival instructions, were also described. Differences in EMS system characteristics between ROC sites were observed with multiple intriguing patterns. Rural areas and fire-based agencies had more EMS units and providers per capita. This may reflect longer response and transport distances in rural areas and the additional duties of most fire-based providers. In addition, hospitals in the United States typically had catheterization laboratories, whereas Canadian hospitals generally did not. The vast majority of both primary and secondary PSAPs use computer-aided dispatch.

CONCLUSIONS

Similarities and differences among EMS systems participating in the ROC network were described. The framework used in this analysis may serve as a template for future EMS research.

A study of police operated dispatch to acute coronary syndrome cases arising from 112 emergency calls in Aarhus county, Denmark

BACKGROUND

The accuracy of the Danish police operated "112" emergency call system was studied. Dispatch of the anaesthesiologist staffed mobile emergency care unit (MECU) to acute coronary syndrome (ACS) cases was used as an indicator of accuracy of dispatch to life threatening emergencies.

METHODS

This was an observational cohort study of patients given a 112 system report of heart attack and patients with a provisional diagnosis of ACS made on scene by the MECU. Sensitivity, specificity, and positive predictive value with 95% confidence intervals (CI) were calculated.

RESULTS

There were 341 reports of "heart attack" and 205 patients with ACS. Sensitivity was 75% (95% CI 68% to 80%) specificity 90% (89% to 92%) and positive predictive value 45% (40% to 50%).

CONCLUSION

The accuracy of 112 dispatch of the MECU was found to be moderate. We suggest more training of dispatch staff and medical supervision.

Accuracy in identifying patients with loss of consciousness in a police-operated emergency call centre - first step in the chain of survival

BACKGROUND

The first link in the 'chain of survival' is the activation of Emergency Medical Services (EMS). In the major part of Denmark, police officers operate the alarm 1-1-2 centre, including calls for EMS. Our aim was to study the police 1-1-2 operators' accuracy in identifying calls concerning patients with loss of consciousness as a key symptom of life-threatening conditions. 'Unconsciousness' was defined as patients with a Glasgow Coma Scale (GCS) score of < 9, scored by the on-scene anaesthesiologist from the Mobile Emergency Care Unit (MECU).

METHODS

This study was an observational cohort study based on data from the Police 1-1-2 Database and the Aarhus County Pre-hospital Database containing data from MECU cases during 6 months in 2004-05.

RESULTS

Two thousand, three hundred and forty-three emergency calls with MECU dispatch were identified. In 1655 cases, both 1-1-2 data and the GCS score were recorded. Two hundred and ninety-five patients were found with a GCS score of < 9 at MECU arrival, 243 of whom were reported 'unconscious' by 1-1-2, giving a sensitivity of 82%. One thousand, three hundred and sixty patients were found with a GCS score of > or = 9, 972 of whom were reported 'awake', giving a specificity of 72%. The positive predictive value (percentage of patients found with a GCS score of < 9 at MECU arrival amongst patients reported as 'unconscious') was 39%.

CONCLUSIONS

The accuracy was moderate with room for improvement. The positive predictive value was low, indicating over-triage of MECU.

The Cochrane Library as a resource for evidence on out-of-hospital health care interventions

STUDY OBJECTIVE

Although the Cochrane Library is promoted as a rigorous source of evidence, the relevance of this evidence to the out-of-hospital setting has not been assessed. The objective of this study is to identify existing controlled trials and systematic reviews in the Cochrane Library that have been conducted in or are relevant to out-of-hospital health care. The scope of out-of-hospital care, the years and trends of out-of-hospital research publication, and the journals of publication are also examined.

METHODS

Using a search strategy developed by the Cochrane Prehospital and Emergency Health Field, 2 reviewers searched issue 4, 2005 of the Cochrane Library to identify reports of controlled trials and systematic reviews on out-of-hospital interventions. Three independent reviewers screened the titles identified by the search strategy and applied predetermined criteria to classify the reported study as out-of-hospital based or not out-of-hospital based. The out-of-hospital-based studies were then categorized as randomized or nonrandomized trials.

RESULTS

Screening of the 19,759 titles retrieved by the search strategy identified 4,016 studies that were potentially out-of-hospital based. Abstract and full-text analysis of the 4,016 studies identified 400 reports of trials and 13 reviews or protocols that were out-of-hospital based. Of the 400 reports of trials identified, 299 (75%) were randomized trials. The number of out-of-hospital trials published increased steadily from the 1970s to the late 1990s, with the majority of trials (63%) covering interventions related to resuscitation and cardiac care. Annals of Emergency Medicine published more out-of-hospital trials than any other journal, followed by Resuscitation and Journal of the American Medical Association.

CONCLUSION

The Cochrane Library provides a useful resource of health care evidence; however, the relatively small number of out-of-hospital-based systematic reviews and trials does not comprehensively cover the broad scope of out-of-hospital health care.

Could a computer-based system including a prevalence function support emergency medical systems and improve the allocation of life support level?

OBJECTIVES

To evaluate whether a computer-based decision support system could be useful for the emergency medical system when identifying patients with acute myocardial infarction (AMI) or life-threatening conditions and thereby improve the allocation of life support level.

METHODS

Patients in the Municipality of Göteborg who dialled the dispatch centre due to chest pain during a period of 3 months. To analyse the relationship between patient characteristics (according to a case record form used during an interview) and the response variables (AMI or life-threatening condition), multivariate logistic regression was used. For each patient, the probability of AMI/life-threatening condition was estimated by the model. We used these probabilities retrospectively to allocate advanced life support or basic life support. This model allocation was then compared with the true allocation made by the dispatchers.

RESULTS

The sensitivity, that is, the percentage of AMI patients allocated to advanced life support, was 85.7% in relation to the true allocation made by the dispatchers. The corresponding sensitivity regarding allocation made by the model was 92.4% (P=0.17). The specificity was also slightly higher for the model allocation than the dispatcher allocation. Among the 15 patients with AMI who were allocated to basic life support by the dispatchers, nine died (eight during and one after hospitalization). Among the eight patients with AMI allocated to basic life support by the model, only one patient died (in hospital) (P=0.02).

CONCLUSION

A computer-based decision support system including a prevalence function could be a valuable tool for allocating the level of life support. The case record form, however, used for the interview can be refined and a model based on a larger sample and confirmed in a prospective study is recommended.

The demand for prehospital advanced life support and the appropriateness of dispatch in Taipei

INTRODUCTION

Implementing prehospital advanced life support (ALS) services requires more medical and societal resources in training and equipment. The actual demand for ALS services in our communities was not clear. To ensure good use of expensive resources, it is important to evaluate the demand and appropriateness of ALS services before full-scale implementation takes place.

OBJECTIVE

To evaluate the rate and characteristics of demand for ALS, and the appropriateness of ALS dispatch of the emergency medical service (EMS) system in metropolitan Taipei City.

METHODS

A retrospective, cross-sectional analysis of the EMS records of Taipei City Fire Department from April 1999 to December 2000 was conducted. Stratified random sampling of all EMS records in the second week of January, April, July and October of 2000 were obtained, along with the corresponding ALS dispatch records. Retrospective ALS demand criteria, including the chief complaints, mechanisms of injury/illness, initial vital signs and types of care rendered, were developed to estimate the rate of ALS demand. ALS demand is expressed as the percentage of cases fulfilling ALS criteria over the total number of EMS cases. Appropriate ALS dispatches were those ALS dispatches determined as fulfilling the ALS demand criteria.

RESULTS

Among the sampled 5433 EMS cases, 490 (9.02%) were determined as a demand for ALS care. ALS demands varied from region to region, and were higher during winter months and afternoon rush hours. There were 175 actual ALS dispatches, accounting for 3.22% of the sampled EMS services. The triage performance was suboptimal: the appropriateness of ALS dispatch was 37.14%; the overtriage rate was 72.86%.

CONCLUSION

Around nine percent of EMS calls demand ALS services. The current triage performance for proper ALS dispatch was suboptimal. A correct ALS dispatch protocol and more dispatcher training programmes should be established in the communities to ensure best use of valuable ALS resources.

Comparison of the medical priority dispatch system to an out-of-hospital patient acuity score

BACKGROUND

Although the Medical Priority Dispatch System (MPDS) is widely used by emergency medical services (EMS) dispatchers to determine dispatch priority, there is little evidence that it reflects patient acuity. The Canadian Triage and Acuity Scale (CTAS) is a standard patient acuity scale widely used by Canadian emergency departments and EMS systems to prioritize patient care requirements.

OBJECTIVES

To determine the relationship between MPDS dispatch priority and out-of-hospital CTAS.

METHODS

All emergency calls on a large urban EMS communications database for a one-year period were obtained. Duplicate calls, nonemergency transfers, and canceled calls were excluded. Sensitivity and specificity to detect high-acuity illness, as well as positive predictive value (PPV) and negative predictive value (NPV), were calculated for all protocols.

RESULTS

Of 197,882 calls, 102,582 met inclusion criteria. The overall sensitivity of MPDS was 68.2% (95% confidence interval [CI] = 67.8% to 68.5%), with a specificity of 66.2% (95% CI = 65.7% to 66.7%). The most sensitive protocol for detecting high acuity of illness was the breathing-problem protocol, with a sensitivity of 100.0% (95% CI = 99.9% to 100.0%), whereas the most specific protocol was the one for psychiatric problems, with a specificity of 98.1% (95% CI = 97.5% to 98.7%). The cardiac-arrest protocol had the highest PPV (92.6%, 95% CI = 90.3% to 94.3%), whereas the convulsions protocol had the highest NPV (85.9%, 95% CI = 84.5% to 87.2%). The best-performing protocol overall was the cardiac-arrest protocol, and the protocol with the overall poorest performance was the one for unknown problems. Sixteen of the 32 protocols performed no better than chance alone at identifying high-acuity patients.

CONCLUSIONS

The Medical Priority Dispatch System exhibits at least moderate sensitivity and specificity for detecting high acuity of illness or injury. This performance analysis may be used to identify target protocols for future improvements.

Sensitivity and specificity of the medical priority dispatch system in detecting cardiac arrest emergency calls in Melbourne

INTRODUCTION

In Australia, cardiac arrest kills 142 out of every 100,000 people each year; with only 3-4% of out-of-hospital patients with cardiac arrest in Melbourne surviving to hospital discharge. Prompt initiation of cardiopulmonary resuscitation (CPR), defibrillation, and advanced cardiac care greatly improves the chances of survival from cardiac arrest. A critical step in survival is identifying by the emergency ambulance dispatcher potential of the probability that the person is in cardiac arrest. The Melbourne Metropolitan Ambulance Service (MAS) uses the computerized call-taking system, Medical Priority Dispatch System (MPDS), to triage incoming, emergency, requests for ambulance responses. The MPDS is used in many emergency medical systems around the world, however, there is little published evidence of the system's efficacy.

OBJECTIVE

This study attempts to undertake a sensitivity/specificity analysis to determine the ability of MPDS to detect cardiac arrest.

METHODS

Emergency ambulance dispatch records of all cases identified as suspected cardiac arrest by MPDS were matched with ambulance, patient-care records and records from the Victorian Ambulance Cardiac Arrest Registry to determine the number of correctly identified cardiac arrests. Additionally, cases that had cardiac arrests, but were not identified correctly at the point of call-taking, were examined. All data were collected retrospectively for a three-month period (01 January through 31 March 2003).

RESULTS

The sensitivity of MPDS in detecting cardiac arrest was 76.7% (95% confidence interval (CI): 73.6%-79.8%) and specificity was 99.2% (95% CI: 99.1-99.3%). These results indicate that cardiac arrests are correctly identified in 76.7% of cases.

CONCLUSION

Although the system correctly identified 76.7% of cardiac arrest cases, the number of false negatives suggests that there is room for improvement in recognition by MPDS to maximize chances for survival in out-of-hospital cardiac arrest. This study provides an objective and comprehensive measurement of the accuracy of MPDS cardiac-arrest detection in Melbourne, as well as providing a baseline for comparison with subsequent changes to the MPDS.

Prehospital mortality in an EMS system using medical priority dispatching: a community based cohort study

OBJECTIVES

This study was planned to record prehospital death rates in four medical priority categories (A, B, C and D) and to evaluate if deaths in lower urgency categories C and D (target response times 20 and 90 min) could have been avoided by a faster ambulance response.

METHODS

The design was a community based cohort study including an expert panel evaluation of the deaths. The study was conducted in the Emergency Medical Services in Helsinki, Finland. All consecutive ambulance calls excluding interhospital patient transfers between 1 January 1999 and 31 December 2002 were included. Prehospital mortality and avoidability of prehospital deaths by a faster ambulance response (maximum 8 min) were used as main outcome measures.

RESULTS

A total of 151928 calls were prioritized in the dispatching centre (category A 8677 calls, B 41005, C 71991 and D 30255). Prehospital death occurred 451 times in category A, 468 times in category B, 73 times in category C and 8 times in category D calls. Respectively, the prehospital death rates per 1000 calls were 52.0 (A), 11.4 (B), 1.0 (C) and 0.3 (D) (P < 0.0001). The expert panel judged that 1 (1.3%) of category C deaths would have been avoidable, 24 (32.9%) potentially avoidable and 48 (65.8%) not avoidable by a more rapid ambulance response. The corresponding figures for category D deaths were 0 (0%), 5 (62.5%) and 3 (37.5%), respectively.

CONCLUSIONS

The use of medical priority dispatching was associated with very low prehospital mortality in lower urgency categories C and D. Approximately, one-third of those deaths could probably be prevented by a faster ambulance response but the price would be a three-fold increase in calls with blue lights and siren. Further studies are needed to find out if our results are applicable to other types of EMS systems.