Effect of mobile paramedic units on outcome in patients with myocardial infarction

Barriers to EMS System Evaluation: Problems Associated with Field Data Collection

For more than two decades, emergency medical services (EMS) systems have proliferated primarily based upon governmental impetus and funding at the federal, state, and local levels. Although many of the foundations of patient care rendered in these systems have been based upon intuitive logic, the understanding of the impact on patient outcome is poor, at best. The reasons for the current status are varied, but five issues are preeminent:

1) The authority for the development of these medical systems has been based primarily in political and bureaucratic institutions which have little or no medical expertise;

2) Little attention has been paid to system evaluation, particularly in the area of cost-effectiveness;

3) Few academic medical institutions have become involved in EMS research;

4) Traditional approaches to medical research primarily are disease-specific and are not multidisciplinary. Thus these are not useful for evaluating and understanding the highly complex and uncontrolled environmental interactions that typify EMS systems; and

5) The process of efficiently and reliably collecting accurate data in the prehospital setting is extremely difficult.

A personal perspective: can legislated state regional STEMI centers provide timely STEMI treatment while overlooking early fibrinolysis?

Because a patient's odds of surviving a ST-Elevation Myocardial Infarction (STEMI) depend on how much myocardium is salvaged by treatment, this article presents information about whether the Missouri Regional STEMI Center Program, created by state law, can provide STEMI treatment in time to preserve the ischemic heart muscle. The law states that "Patients who suffer a STEMI, as defined in Section 190.100, shall be transported to a STEMI Center." Administration is by the Missouri Department of Health and Senior Services (DHSS) which states that the preferred treatment for STEMI is percutaneous coronary intervention (PCI) and does not mention fibrinolysis when eligible. Level I and II receiving centers are hospitals with catheterization laboratories that perform a high volume of PCI procedures. Level I centers have heart surgery facilities. Level II centers may have such services or may have prompt access to nearby facilities. The law states that the smaller level III and IV hospitals are to stabilize patients for transport to a level I or II center. Although the law lists no patients to be excluded from transport, DHSS is limiting the program to patients picked up at the scene by ambulance. The majority of STEMI patients going to community hospitals by car are not included. Data are presented, showing that when blood flow is restored to the ischemic muscle during infarction before the end of the second hour of symptoms most can be saved. Data also show that only a small fraction of patients with PCI receives it before the end of the second hour of symptoms, whereas many more fibrinolysis patients were treated within 2 hours. Clinical practice data are given, showing mortality rates to increase with longer times to treatment. This information clearly defines timely treatment of STEMI to be that carried out before the end of the second hour of symptoms. Setting forth details of how long after symptom onset will be required to get to the catheterization laboratory shows that not many Missouri Program STEMI patients will get there before the end of the second hour of symptoms when salvageable heart muscle remains. The second thrust of this article is to draw attention to the seriousness of the Missouri Program overlooking the extremely important early fibrinolysis option for achieving treatment during the first 2 hours of symptoms.

The Efficacy of Advanced Life Support: A Review of the Literature

Introduction:

Jurisdictions throughout the United States and some other parts of the world have invested substantial time and resources into creating and sustaining a prehospital advanced life support (ALS) system without knowing whether the efficacy of ALS-level care had been validated scientifically. In recent years, it has become fashionable for speakers before large audiences to declare that there is no scientific evidence for the clinical effectiveness of ALS-level care in the out-of-hospital setting. This study was undertaken to evaluate the evidence that pertains to the efficacy of ALS-level care in the current scientific literature.

Methods:

An extensive review of the available literature was accomplished using computerized and manual means to identify all applicable articles from 1966 to October, 1995. Selected articles were read, abstracted, analyzed, and compiled Each article also was categorized as presenting evidence supporting or refuting the clinical efficacy of ALS-level care, and a list was constructed that pointed to where the preponderance of the evidence lies.

Results:

Research in this field differs widely in terms of methodological sophistication. Of the 51 articles reviewed, eight concluded that ALS-level care is not any more effective than is basic life support, seven concluded that it is effective in some applications but not for others, and the remainder demonstrated effectiveness. The strongest support for ALS-level care was in the area of responses to victims of cardiac arrest, whereas somewhat more divergent findings related to trauma or non condition-specific studies.

Conclusion:

While not unanimous, the predominant finding of recent research into the clinical effectiveness of advanced life support demonstrates improved effectiveness over basic life support for patients with certain pathologies. More outcomes-based research is needed.

A personal perspective: at the crossroads of heart attack care: designing an effective nationwide public education program to hasten patient hospital arrival

This report presents a field-tested approach to the greatest health care problem facing our country, the fact that two-thirds of the deaths from acute myocardial infarction occur before hospital admission. Scores of fundraising appearances for the Missouri Heart Association during the 1950s and 1960s throughout the 1,000,000 population rural/urban Southwest Missouri region gave an ideal setting for teaching the public the early symptoms of heart attack. Audiences were advised that if any of these appeared they should immediately call their doctor or quickly get to the nearest hospital emergency room. These presentations led to a steady increase in hospital admissions. The Missouri Heart Association responded by launching the Early Warning Signs of Heart Attack Public and Professional Education Program in July 1971, incorporating these messages in radio, TV, and newspaper Public Service Announcements. In less than 6 months, analysis of consecutive admissions to the cardiovascular intensive care unit of the base hospital showed that the median time from the onset of symptoms to starting to the hospital was reduced from 4 to 2.2 hours; 64% of those patients called their doctor as their first step in seeking help and 58% went to the hospital by car. This message content was carried through the 1980s and 1990s under other auspices. The methods of the successful Missouri program are contrasted with others that have failed, establishing essential features in designing a nationwide program effective in hastening acute myocardial infarction patient hospital arrival.

A Meta-Analysis of Prehospital Care Times for Trauma

BACKGROUND

Time to definitive care is a major determinant of trauma patient outcomes yet little is empirically known about prehospital times at the national level. We sought to determine national averages for prehospital times based on a systematic review of published literature.

METHODS

We performed a systematic literature search for all articles reporting prehospital times for trauma patients transported by helicopter and ground ambulance over a 30-year period. Forty-nine articles were included in a final meta-analysis. Activation time, response time, on-scene time, and transport time were abstracted from these articles. Prehospital times were also divided into urban, suburban, rural, and air transports. Statistical tests were computed using weighted arithmetic means and standard deviations.

RESULTS

The data were drawn from 20 states in all four U.S. Census Regions and represent the prehospital experience of 155,179 patients. Average duration in minutes for urban, suburban, and rural ground ambulances for the total prehospital interval were 30.96, 30.97, and 43.17; for the response interval were 5.25, 5.21, and 7.72; for the on-scene interval were 13.40, 13.39, and 14.59; and for the transport interval were 10.77, 10.86, and 17.28. Average helicopter ambulance times were response 23.25, on-scene 20.43, and transport 29.80 minutes.

CONCLUSIONS

Despite the emphasis on time in the prehospital and trauma literature there has been no national effort to empirically define average prehospital time intervals for trauma patients. We provide points of reference for prehospital intervals so that policymakers can compare individual emergency medical systems to national norms.

Initial cardiac rhythm correlated to emergency department survival

BACKGROUND

This study attempted to correlate the initial cardiac rhythm and survival from prehospital cardiac arrest, as a secondary end-point.

METHODS

Prospective, randomized, double-blinded clinical intervention trial where bicarbonate was administered to 874 prehospital cardiopulmonary arrest patients in prehospital urban, suburban, and rural emergency medical service environments.

RESULTS

This group's manifested an overall survival rate of 13.9% (110 of 793) of prehospital cardiac arrest patients. The most common presenting arrhythmia was ventricular fibrillation (VF) (45.0%), asystole (ASY) (34.4%), and pulseless electrical activity (PEA) (15.7%). Less commonly found were normal sinus rhythm (NSR) (1.8%), other (1.8%), ventricular tachycardia (VT) (0.6%), and atrioventricular block (AVB) (0.5%) as prearrest rhythms. The best survival was noted in those with a presenting rhythm of AVB (57.1%), VT (33.3%), VF (15.7%), NSR (14.3%), PEA (11.2%), and ASY (11.1%) (p = 0.02). However, there was no correlation between the final cardiac rhythm and outcome, other than an obvious end-of-life rhythm.

CONCLUSION

The most common presenting arrhythmia was VF (45%), while survival is greatest in those presenting with AVB (57.1%).

Survival from prehospital cardiac arrest is critically dependent upon response time

STUDY OBJECTIVE

This study correlated the delay in initiation of bystander cardiopulmonary resuscitation (ByCPR), basic (BLS) or advanced cardiac (ACLS) life support, and transport time (TT) to survival from prehospital cardiac arrest. This was a secondary endpoint in a study primarily evaluating the effect of bicarbonate on survival.

DESIGN

Prospective multicenter trial.

SETTING

Patients treated by urban, suburban, and rural emergency medical services (EMS) services.

PATIENTS

Eight hundred and seventy-four prehospital cardiac arrest patients.

INTERVENTIONS

This group underwent conventional ACLS intervention followed by empiric early administration of sodium bicarbonate noting resuscitation times. Survival was measured as the presence of vital signs on emergency department (ED) arrival. Data analysis utilized Student's t-test and logistic regression (p<0.05).

RESULTS

Survival was improved with decreased time to BLS (5.52 min versus 6.81 min, p=0.047) and ACLS (7.29 min versus 9.49 min, p=0.002) intervention, as well as difference in time to return of spontaneous circulation (ROSC). The upper limit time interval after which no patient survived was 30 min for ACLS time, and 90 min for transport time. There was no overall difference in survival except at longer arrest times when considering the primary study intervention bicarbonate administration.

CONCLUSION

Delay to the initiation of BLS and ACLS intervention influenced outcome from prehospital cardiac arrest negatively. There were no survivors after prolonged delay in initiation of ACLS of 30 min or greater or total resuscitation and transport time of 90 min. This result was not influenced by giving bicarbonate, the primary study intervention, except at longer arrest times.

The influence of urban, suburban, or rural locale on survival from refractory prehospital cardiac arrest

There are many variables that can have an effect on survival in cardiopulmonary arrest. This study examined the effect of urban, suburban, or rural location on the outcome of prehospital cardiac arrest as a secondary end point in a study evaluating the effect of bicarbonate on survival. The proportion of survivors within a type of EMS provider system as well as response times were compared. This prospective, randomized, double-blind clinical intervention trial enrolled 874 prehospital cardiopulmonary arrest patients encountered by prehospital urban, suburban, and rural regional EMS area. Population density (patients per square mile) calculation allowed classification into urban (>2000/mi2), suburban (>400/mi2), and rural (0-399/mi2) systems. This group underwent standard advanced cardiac life support (ACLS) intervention with or without early empiric administration of bicarbonate in a 1-mEq/kg dose. A group of demographic, diagnostic, and therapeutic variables were analyzed for their effect on survival. Times were measured from collapse until onset of medical intervention and survival measured as the presence of ED vital signs on arrival. Data analysis used chi-squared with Pearson correlation for survivorship and Student t test comparisons for response times. The overall survival rate was approximately 13.9% (110 of 793), ranging from 9% rural, 14% for suburban, and 23% for urban sites for 372 patients (P=.007). Survival differences were associated with classification of arrest locale in this sample-best for urban, suburban, followed by rural sites. There was no difference in time to bystander cardiopulmonary resuscitation, but medical response time (basic life support) was decreased for suburban or urban sites, and intervention (ACLS) and transport times were decreased for suburban sites alone. Although response times were differentiated by location, they were not necessarily predictive of survival. Factors other than response time such as patient population or resuscitation skill could influence survival from cardiac arrest occurring in diverse prehospital service areas.

Prehospital cardiac arrest and the adverse effect of male gender, but not age, on outcome

OBJECTIVE

To analyze the incidence and outcome of prehospital cardiac arrest as it correlated to gender and age as a secondary end point in an interventional clinical trial.

METHODS

This prospective, randomized, double-blinded clinical intervention trial enrolled 874 prehospital cardiopulmonary arrest patients encountered by prehospital urban, suburban, and rural regional emergency medical service (EMS) areas. This trial evaluated outcome and profiled demographic predictors of cardiac arrest patients refractory to defibrillation with intravenous access who underwent standard advanced cardiac life support (ACLS) intervention and empiric early administration of bicarbonate. Survival was measured to the emergency department (ED), and data analysis used chi-square with Pearson correlation.

RESULTS

The overall survival rate was 14.2%. There was no age correlate to survival, with an average age of 67.4 for both groups. Male patients had a 2.4-fold increased incidence (70.7 vs. 29.3%, p = 0.001) of arrest, which was associated with a 60% increase in mortality (19.6% vs. 11.8, p = 0.004) compared with women. The risk of unfavorable outcome was increased for men (OR 1.826, 95% CI 1.182-2.821; RR 1.097, 95% CI 1.025-1.180) on univariate analysis. There appeared to be no intergroup differences found with other historical variables, such as the presence of myocardial infarction (MI), hypertension (HTN), diabetes mellitus (DM), congestive heart failure (CHF), and chronic obstructive pulmonary disease (COPD), which were analyzed. However, HTN was found more commonly (2.2 times) in men (69.1 vs. 30.9%) than in women but did not correlate with survival.

CONCLUSIONS

Male gender, but not age, is associated with both an increased incidence and a worsened outcome in prehospital cardiac arrest.

Patients with chest pain calling 9-1-1 or self-transporting to reach definitive care: which mode is quicker?

OBJECTIVE

We examined differences in transport times for patients with chest pain who used private transportation compared with patients who used emergency medical services (EMS) to reach definitive medical care.

METHODS

This was a retrospective cohort study with data used from the Rapid Early Action for Coronary Treatment (REACT) trial conducted in 20 US cities. Elapsed time to care was examined through the use of (1) decision to seek care to initial care (emergency department [ED] arrival versus EMS arrival on scene [n=1209]); (2) decision to ED arrival (for both groups [n=2388]); (3) time to thrombolytic therapy once admitted to the ED (for both groups [n=309]); and (4) decision to seek care to thrombolytic therapy (n=276). Elapsed travel times were ranked within Zip Codes and submitted to a nested analysis of variance model to determine if elapsed times were different between modes of transport.

RESULTS

Private transportation (35 minutes) resulted in faster ED arrival than using EMS (39 minutes, P =.0014). However, if one considers EMS treatment to be initial care, calling 9-1-1 (6 minutes) resulted in much quicker care than patients using private transportation to the ED (32 minutes, P <.001). Transport by EMS resulted in a shorter elapsed time to thrombolytic administration compared with patients using private transportation when considering ED "door-to-needle" time (32 vs 49 minutes, respectively [P <.001]) or time from decision to seek care until administration of thrombolytic therapy (75 vs 92 minutes, respectively, [P =.042]).

CONCLUSIONS

Although private transportation results in a faster trip to the ED, quicker care is obtained with the use of EMS.

Eight minutes or less: does the ambulance response time guideline impact trauma patient outcome?

Emergency Medical Services (EMS) agencies are increasingly being held to an ambulance response time (RT) criterion of responding to a medical emergency within 8 min for at least 90% of calls. This recommendation resulted from one study of outcome after nontraumatic cardiac arrest and has never been studied for any other emergency. This retrospective study evaluates the effect of exceeding the 8 min RT guideline on patient survival for victims of traumatic injury treated by an urban paramedic ambulance EMS system and transported to a single Level I trauma center. Of 3576 patients identified by the hospital trauma registry, 3490 (97.6%) had complete records available. Patients were grouped according to ambulance RT: < or = 8 min (n = 2450) or > 8 min (n = 1040). After controlling for other significant predictors, there was no difference in survival after traumatic injury when the 8 min ambulance RT criteria was exceeded (mortality odds ratio 0.81, 95% CI 0.43-1.52). There was also no significant difference in survival when patients were stratified by injury severity score group. Exceeding the ambulance industry response time criterion of 8 min does not affect patient survival after traumatic injury.

Advanced life support vs basic life support field care: an outcome study

OBJECTIVE

To determine whether the provision of advanced life support (ALS) field care has any impact on patient outcome in the urban Canadian environment.

METHODS

A convenience cohort study was conducted of all emergent ambulance transfers of adults to an urban Canadian hospital from May 22 to July 31, 1996. Data were collected from ambulance call reports regarding presenting complaint and field interventions applied, and from hospital records regarding time in the ED, hospital length of stay (LOS), and discharge disposition. Patient outcomes were compared within 7 presenting complaint groups (chest pain, altered level of consciousness, shortness of breath, abdominal pain, motor vehicle crash, falls, and other) by field care level: level 1--BLS (basic life support) vs levels 2 and 3--ALS.

RESULTS

The study population consisted of 1,397 patients. No significant differences were seen between BLS and ALS patients on baseline demographics. ED triage score did not depend on field care level for any group, implying that those in the ALS group were not inherently sicker. Outcome measures (ED LOS, admission rates, and hospital LOS) showed no significant differences between BLS and ALS for each presenting complaint group. Discharge dispositions were analyzed by chi2 but were not varied enough to allow reliable analysis. Observation of trends suggested no difference between BLS and ALS.

CONCLUSIONS

There was no beneficial impact on the measured patient outcomes found in association with the provision of ALS vs BLS field care in Metropolitan Toronto for patients who were brought to a nontrauma center.

Designing a prehospital system for a developing country: estimated cost and benefits

Many of the costs associated with prehospital care in developed countries are covered in budgets for fire suppression, police services, and the like. Determining these costs is therefore difficult. The costs and benefits of developing a prehospital care system for Kuala Lumpur, Malaysia, which now has essentially no emergency medical services (EMS) system, were estimated. Prehospital therapies that have been suggested to decrease mortality were identified. A minimal prehospital system was designed to deliver these treatments in Kuala Lumpur. The potential benefit of these therapies was calculated by using statistics from the United States corrected for demographic differences between the United States and Malaysia. Costs were extrapolated from the current operating budget of the Malaysian Red Crescent Society. Primary dysrhythmias are responsible for almost all potentially survivable cardiac arrests. A system designed to deliver a defibrillator to 85% of arrests within 6 minutes would require an estimated 48 ambulances. Kuala Lumpur has approximately 120 prehospital arrhythmic deaths per year. A 6% resuscitation rate was chosen for the denominator, resulting in seven survivors. Half of these would be expected to have significant neurological damage. Ambulances cost $53,000 (US dollars) to operate per year in Kuala Lumpur; 48 ambulances would cost a total of $2.5 million. Demographic factors and traffic problems would significantly increase the cost per patient. Other therapies, including medications, airway management, and trauma care, were discounted because both their additional cost and their benefit are small. Transport of patients (including trauma) is now performed by police or private vehicle and would probably take longer by ambulance. A prehospital system for Kuala Lumpur would cost approximately $2.5 million per year. It might save seven lives, three of which would be marred by significant neurological injury. Developing countries would do well to consider alternatives to a North American EMS model.

Does basic life support in a rural EMS system influence the outcome of patients with respiratory distress?

PURPOSE

The purpose of this study was to determine whether basic life support, prehospital emergency medical care in a rural area affects the hospital course of patients with respiratory distress.

METHODS

Medical records for patients admitted from the emergency department with a discharge diagnosis related to respiratory disease were reviewed. Data collected included: 1) mode of arrival; 2) initial symptom; 3) vital signs; 4) prehospital interventions applied; 5) hospital days; 6) discharge status; and 7) principal diagnosis. Multiple logistic regression analysis was used to predict length of hospital stay.

RESULTS

Charts for 603 patients were reviewed. Complete data for all variables included in the logistic regression analysis were available for 471 patients (78.1%). Because 55 patients died, only 416 (69.0%) were included in the multiple regression analysis conducted to predict length of hospital stay. Logistic regression analysis demonstrated that patients who arrived by ambulance and older patients were more likely to die; patients with higher systolic blood pressures were more likely to survive. Only patient age predicted length of hospital stay, with older patients having longer stays.

CONCLUSIONS

Basic life support prehospital care in this rural emergency medical services system does not result in a lower mortality rate or a shorter hospital stay for a broad group of patients with respiratory distress who require hospital admission. Although this study is limited to a single population and a single emergency medical services system, it is one of only a few studies of outcome in basic life support systems.

Outcomes in severely ill patients transported without prehospital ALS

Because of the debate regarding the impact of advanced life support (ALS) care on the outcome of prehospital patients, we monitored the influence of lack of sophisticated prehospital treatment in cases of severe illness arriving by ambulance to the emergency department (ED). A prospective cohort study to examine and compare the outcome of trauma- and nontrauma-induced "ALS-eligible" cases in the setting of no prehospital care was carried out from August 1, 1993 through May 31, 1994. On arriving at the ED, patients meeting the criteria for ALS cases and sent by EMS public prehospital personnel were assessed for subjective and objective status and change in severity by triage nurses as well as being followed up for neurological status until discharged from the hospital. Chi-Square method was used to compare the data between two groups and P < .05 was considered statistically significant. Of 667 studied ALS cases (155 trauma and 512 nontrauma), < 20% had their condition change subjectively and < 10% had their condition change objectively; 68% of medical patients and 60% of trauma cases were discharged from the hospital (neurologically intact). However, subgroup analysis showed that objective measures worsened in transit in nearly 18% of trauma victims, a rate nearly 3 times greater than that of medical cases. Moreover, neurological outcome was particularly poor in trauma cases. These results suggest that ALS care may be valuable for severely ill trauma victims.

Effects of prehospital care on outcome in patients with cardiac illness

STUDY OBJECTIVE

To compare outcomes of patients with acute cardiac illness transported by ambulance for whom prehospital care was provided by emergency medical technician-paramedics (EMT-Ps) or EMTs trained in defibrillation (EMT-Ds).

DESIGN

A prospective chart review carried out over 3.5 years.

SETTING

The Hamilton-Wentworth region of Ontario, Canada, which covers 1,136 km2 and includes five receiving hospitals.

PARTICIPANTS

We prospectively identified 8,720 potentially eligible patients from approximately 30,000 who presented to the ambulance service. We reviewed hospital charts to confirm eligibility. The group of 8,720 patients yielded 3,066 patients with acute cardiac illness who met all other eligibility requirements. We excluded patients in cardiac arrest.

RESULTS

Incidence of myocardial infarction (MI), length of hospital stay, and mortality were evaluated. Analysis was performed with chi 2 tests for association, linear regression, and logistic regression. Of the eligible patients who received prehospital EMS care, 783 sustained MIs. The proportions of people discharged alive with the diagnosis of MI did not differ between crew types (P = .16). Average hospital stay was 13 days in both groups for patients with the discharge diagnosis of MI; hospital stay ranged from 9 (EMT-D) to 11 days (EMT-P) for any patient with a discharge diagnosis other than MI. These values were statistically similar. The odds ratio of having had an MI after treatment by an EMT-D crew was 1.02 (95% confidence interval, .86 to 1.21) compared with that for treatment by an EMT-P crew.

CONCLUSIONS

In an urban setting with short (less than 10 minutes) average transport times, the availability of prehospital paramedic care does not affect occurrence of MI, length of hospital stay, or mortality of patients presenting to the EMS system with cardiac illness.

Effects of EMS transportation on time to diagnosis and treatment of acute myocardial infarction in the emergency department

INTRODUCTION

Recent studies have documented decreased time to emergency department (ED) thrombolytic therapy with the use of prehospital electrocardiography.

PURPOSE

Is the time to ED diagnosis and treatment of acute myocardial infarction (AMI) patients with thrombolytic agents decreased by emergency medical services (EMS) transport when compared with those transported by other means (non-EMS)?

DESIGN

Retrospective, case-control study.

POPULATION

The AMI patients treated with thrombolytic agents at a 34,000-visit, community hospital ED during 1992.

METHODS

Review of records of patients who received thrombolytic therapy for AMI. Statistical analysis was performed using "Student's" t-test and Yates corrected Chi-square (chi 2).

RESULTS

Eighty-seven patients received thrombolytic agents for AMI during 1992; 33 arrived by ambulance, 54 arrived by other methods. There were no differences in age, gender, or time of ED arrival among these groups. Ambulance patients received standard advanced life support (ALS) care, but not a 12-lead electrocardiogram (ECG) or thrombolytic agents. Ambulance patients experienced a significantly shorter time to first ECG (12.9 +/- 9.1 min. versus 20.8 +/- 25.3 min.; p = .028) and received thrombolytic therapy sooner than did controls (56.0 +/- 31.5 min. versus 78.0 +/- 63.4 min.; p = .018). There was no difference in time from diagnosis to treatment between these groups.

CONCLUSION

Emergency medical services transport of AMI patients in this study decreased time to diagnosis and treatment and may be a confounder in studies that assess the value of field EMS interventions. Non-EMS AMI patients did not receive as rapid diagnosis and treatment, and emergency physicians should evaluate and address this issue in their departments.

Differential prehospital benefit from paramedic care

STUDY OBJECTIVES

To determine whether prehospital outcome of patients who receive care from emergency medical technicians-paramedic (EMT-Ps) differs from that of patients who receive care from emergency medical technicians-defibrillation (EMT-Ds), as rated by the treating EMTs using standardized scales, and to determine whether the patient's seriousness of illness is relevant to any differential benefit of one level of care over the other.

DESIGN

Historical (retrospective) cohort.

SETTING

An urban and semiurban region of southwest Ontario comprising an area of 1,136 square kilometers (438 square miles) with a population of more than 445,000.

TYPE OF PARTICIPANTS

Patients (10,291) who were transported by the Hamilton-Wentworth EMS system between January 1, 1991, and December 31, 1991.

METHODS AND MEASUREMENTS

EMTs rated the prehospital outcome of their own patients, using scales that had been tested in a previous study. Comparisons between EMT-P- and EMT-D-treated patients were made by chi 2, chi 2 by trend, and Fisher's exact test as appropriate.

RESULTS

More seriously ill or injured EMT-P-treated patients were rated as improved and fewer EMT-P-treated patients were rated as worsened compared with similar patients who were cared for and rated by EMT-Ds. The differential benefit from EMT-P to EMT-D care ranged from 8% to 25% for patients rated as "severe" and from 27% to 49% for patients rated as "life-threatened."

CONCLUSION

According to the ratings of prehospital care providers, patients classified as "severe" or "life-threatened" had their conditions "improve" by the time they arrived at the hospital more often when care was provided by an EMT-P team than when it was provided by an EMT-D team.

Prospective validation of a new model for evaluating emergency medical services systems by in-field observation of specific time intervals in prehospital care

STUDY OBJECTIVE

To develop and validate a new time interval model for evaluating operational and patient care issues in emergency medical service (EMS) systems. DESIGN/SETTING/TYPE OF PARTICIPANT: Prospective analysis of 300 EMS responses among 20 advanced life support agencies throughout an entire state by direct, in-field observation.

RESULTS

Mean times (minutes) were response, 6.8; patient access, 1.0; initial assessment, 3.3; scene treatment, 4.4; patient removal, 5.5; transport, 11.7; delivery, 3.5; and recovery, 22.9. The largest component of the on-scene interval was patient removal. Scene treatment accounted for only 31.0% of the on-scene interval, whereas accessing and removing patients took nearly half of the on-scene interval (45.8%). Operational problems (eg, communications, equipment, uncooperative patient) increased patient removal (6.4 versus 4.5; P = .004), recovery (25.4 versus 20.2; P = .03), and out-of-service (43.0 versus 30.1; P = .007) intervals. Rural agencies had longer response (9.9 versus 6.4; P = .014), transport (21.9 versus 10.3; P < .0005), and recovery (29.8 versus 22.1; P = .049) interval than nonrural. The total on-scene interval was longer if an IV line was attempted at the scene (17.2 versus 12.2; P < .0001). This reflected an increase in scene treatment (9.2 versus 2.8; P < .0001), while patient access and patient removal remained unchanged. However, the time spent attempting IV lines at the scene accounted for only a small part of scene treatment (1.3 minutes; 14.1%) and an even smaller portion of the overall on-scene interval (7.6%). Most of the increase in scene treatment was accounted for by other activities than the IV line attempts.

CONCLUSION

A new model reported and studied prospectively is useful as an evaluative research tool for EMS systems and is broadly applicable to many settings in a demographically diverse state. This model can provide accurate information to system researchers, medical directors, and administrators for altering and improving EMS systems.

Prehospital care: the future of emergency medical services

Most prehospital interventions, both pharmacologic and procedural, have been accepted without clear demonstrations of their abilities to impact patient outcomes or without clear indications that withholding or delaying the intervention pending arrival at a definitive emergency department will adversely affect the patient. Interventions that have the benefit of supportive research have been applied equally to urban and nonurban emergency medical services environments. In selecting interventions, inadequate consideration has been given to the differences in emergency medical services personnel training, frequencies of their exposure to patients, frequencies of skill use, and availabilities of effective continuing education programs in the urban and nonurban environments. These issues are discussed, and the necessary focus of the future of emergency medical services in urban, suburban, and rural environments is predicted.

Efficacy of computer-assisted instruction in the continuing education of paramedics

STUDY OBJECTIVE

To determine the relative effectiveness of lecture, video, and computer-assisted instruction (CAI) for the continuing education of paramedics.

DESIGN

The study was a statewide, cross-sectional, and prospective. It used premethod, post method and 60-day evaluations addressing both cognitive knowledge and attitude toward the method. Subjects were required to complete a 20-question cognitive examination and a ten-point satisfaction inventory. Each study site was randomly assigned a method by a computer-generated table.

SETTING

The study involved 11 sites, systematically distributed throughout Michigan.

TYPE OF PARTICIPANTS

111 Michigan licensed paramedics.

RESULTS

CAI subjects scored an average of 79.6% on the post-test, while lecture and video subjects scored 70.5% and 68.9%, respectively. At 60 days, CAI subjects scored 70.9%, while lecture and video subjects averaged 59.4 and 59.1, respectively. The difference among the scores was significant post method (P = .01) and at 60 days (P = .02). The subject method preference was lecture, video, and CAI premethod; lecture, CAI, and video immediately post method; and lecture, CAI, and video at 60 days.

CONCLUSION

Although lecture was the preferred method, CAI was best able to impart knowledge and enhance participant knowledge retention.

Prehospital data entry compliance by paramedics after institution of a comprehensive EMS data collection tool

OBJECTIVE

To determine the completeness of data entry by paramedics after an extensive modification of the prehospital first-care form in an urban emergency medical services (EMS) system.

DESIGN

Comprehensive medical information was added to the EMS data collection tool used by a metropolitan fire department. We evaluated the frequency of failure to enter data pertaining to medical assessment and/or treatment of victims of cardiac arrest after implementation of the system.

RESULTS

Failure to enter data in the first month was compared with two subsequent two-month blocks. A high rate of noncompliance existed in the first month (all medical data were missing in 24.6%). However, the subsequent two months revealed a marked decline in noncompliance (4.4%, P less than .001). This decline was maintained after a three-month interim (5.0%, P less than .001).

CONCLUSION

Data entry noncompliance can be a significant problem after implementation of a new prehospital data collection system. However, compliance can be markedly improved over a relatively short period. Because EMS system evaluation is based on data collected in the field. EMS researchers and administrators must be aware of the data entry compliance rate in their system when attempting to make conclusions from such information.

Evaluation of the injury profile of personnel in a busy urban EMS system

The occupational injury profile of emergency medical technicians (EMTs) and paramedics is not well described. We retrospectively studied 254 injuries over a 3.5-year period in a busy urban EMS system. Low back strain was the most common injury (93/254, 36%), with EMTs suffering a significantly higher injury rate than paramedics (0.33 v 0.17 injuries/person-years at risk, P = .03). Lifting caused 58/93 (62.4%) of back injuries, and most occurred at the scene to which personnel were dispatched (58/93, 62.4%). The back injuries were recurrent in 31% of personnel. The data showed trends toward higher overall injury rates among EMTs compared with paramedics (0.83 v 0.55, P = 0.057) and women compared with men (0.86 v 0.50, P = 0.11). There was a significantly higher injury rate among personnel less than 30 years of age compared with those 30 years or older (0.65 v 0.39, P = 0.01). Over 25% of the personnel injured had more than one injury per year. There was no correlation between injury rates and job experience. Approximately 96 injuries accounted for 481 compensation days with low back strain the cause of 375 days (78%). Our findings suggest a high incidence of occupational injury in EMS personnel with EMTs and persons under 30 years of age at higher risk. Guidelines for prevention programs are suggested.

Characteristics of midsized urban EMS systems

Emergency medical services (EMS) systems in 25 midsized cities (population, 400,000 to 900,000) are described. Information describing EMS system configuration and performance was collected by written and telephone surveys with follow-ups. Responding cities provide either one- or two-tier systems. In a one-tier system, an advanced life support (ALS) unit responds to and transports all patients who use 911 to activate the system. Three types of two-tier systems are identified. In system A, ALS units respond to all calls. Once on scene, an ALS unit can turn a patient over to a basic life support (BLS) unit for transport. In system B, ALS units do not respond to all calls; BLS units may be sent for noncritical calls. In system C, a nontransport ALS unit is dispatched with a transporting BLS unit. For ALS calls, ALS personnel join BLS personnel for transport. Overall, cities staff an average of one ambulance per 51,223 population. One-tier systems average one ambulance per 53,291 compared with two-tier systems, which average one ambulance per 47,546. In the two-tiered system B, the average ALS unit serves 118,956 population. In the 60% of cities that use a one-tier system, one ALS unit serves 58,336 (P less than .0005). Overall, the code 3 response time for all cities is an average of 6.6 minutes. The average response time of two-tier systems is 5.9 minutes versus 7.0 minutes for one-tier systems (.05 less than P less than .1). These data suggest that the two-tiered system B allows for a given number of ALS units to serve a much larger population while maintaining a rapid code 3 response time.