Use of a geographic information system to determine appropriate means of trauma patient transport

Geospatial Assessment to Improve Time to Treatment (GAITT)

INTRODUCTION

Geographic information systems (GIS) can optimize trauma systems by identifying ways to reduce time to treatment. Using GIS, this study analyzed a system in Maryland served by Johns Hopkins Suburban Hospital and the University of Maryland Capital Region Medical Center. It was hypothesized that including Walter Reed National Military Medical Center (WRNMMC) in the Maryland trauma system in an access simulation would provide increased timely access for a portion of the local population.

MATERIALS AND METHODS

Using ArcGIS Online, catchment areas with and without WRNMMC were built. Catchment areas captured Johns Hopkins Suburban Hospital, University of Maryland Capital Region Medical Center, and WRNMMC at 5-, 10-, 15-, 20-, 25-, 30-, 45-, and 60-min. Various time conditions were simulated (12 am, 8 am, 12 pm, and 5 pm) on a weekday and weekend day. Data was enriched with 19 variables addressing population size, socioeconomic status, and diversity.

RESULTS

All catchment areas benefited on at least one time-day simulation, but the largest increases in mean population coverage were in the 0-5 (10.5%), 5-10 (12.3%), and 10-15 min (5.7%) catchment areas. These areas benefited regardless of time-day simulation. The lowest increase in mean population coverage was seen in the 20-25-min catchment area (0.1%). Subgroup analysis revealed that all socioeconomic status and diversity groups gained coverage.

CONCLUSIONS

This study suggests that incorporating WRNMMC into the Maryland trauma system might yield increased population coverage for timely trauma access. If incorporated, WRNMMC may provide nonstop or flexible coverage, possibly in different traffic scenarios or while civilian centers are on diversion status.

Predictors of Inappropriate Helicopter Transport

Background

Helicopter transport (HT) is an efficient, but costly, means for injured patients to receive life-saving, definitive trauma care. Identifying the characteristics of inappropriate HT presents an opportunity to improve the utilization of this finite medical resource.

Methods

Trauma registry records of all HT for a 3-year period (2016-2018) to an urban Level I trauma center were reviewed. HT was defined as inappropriate for patients who were discharged home from the emergency department or had a hospital length of stay <1 day, and who were discharged alive. Chi-square analysis and Student’s t-test were used for univariate analysis. Predictors with a P value of less than .15 were subject to binary logistic regression analysis. A P value ≤.05 was considered significant.

Results

There were 713 patients who received HT during the study period. One-hundred and forty-eight (20.8%) patients met the criteria as an inappropriate HT. In univariate analysis, Glasgow Coma Scale >8, Shock Index <0.9, and fall mechanism were found to be significantly associated with inappropriate HT. Age >55 was found to be associated with an appropriate HT. The average Injury Severity Score of the inappropriate HT group was 3.86 (±3.85) compared with 16.80 (±11.23) ( P = .0001, Student’s t-test).

Discussion

Our findings suggest that there are evidence-based predictors of patients receiving inappropriate HT. Triage of HT using these predictors has the potential to decrease unnecessary deployments and reduce health care costs.

Is Helicopter Really Faster Than Ambulance? The Padua Helicopter Emergency Medical Services Station Experience

OBJECTIVE

Helicopter transport plays a fundamental role in modern health systems, and, yet, it is not been the focus of scientific research, especially in Italy. Our objective was to analyze Padua helicopter emergency medical services (HEMS) station operations to discover whether this resource has been used correctly and advantageously.

METHODS

The study was conducted considering 115 helicopter air ambulance operations minutes in 2018. Additionally, using geographic information systems and estimated ambulance data, a comparison was drawn between air and ground emergency medical services.

RESULTS

Interfacility transports involved mainly adults. There were 65 (56.52%) "acute transports," 49 (42.61%) "back transports," and 1 "hyperspecialized care transport" (0.87%). The average route distance was 44.23 km; the modal class was 25 to 30 km. The average mission time was 1 hour 26 minutes; the modal class was 1 hour to 1 hour 15 minutes. The Pearson correlation coefficient between flying/traveling time and the route length was 0.92 for helicopter and 0.94 for ambulance, and between mission time and route length, it was 0.05 for helicopter and 0.94 for ambulance.

CONCLUSION

Helicopters are not always the fastest mode of transporting patients, and journey time is variable. Because of the importance of rapid response in emergency situations, we propose not to use helicopters for transports less than 50 km in distance.

Helicopter Emergency Medical Services Utilization

BACKGROUND

The decision to utilize HEMS is a complex process that involves many considerations. Professional associations and agencies have published guidelines to assist providers with decision making for the utilization of helicopter transport.

STUDY OBJECTIVE

Determine if requests for HEMS align with recently published utilization guidelines.

STUDY DESIGN

A retrospective chart review was performed during a six-month period. Reviewers versed in Wisconsin HEMS Utilization, NAEMSP, and CAMTS guidelines determined if transport criteria were met. Charts were categorized according to whether or not criteria for each set of recommendations were followed.

RESULTS

514 charts were reviewed; 439 consisted of completed patient transports. CAMTS, NAEMSP, and WI HEMS guidelines satisfied 85.4%, 83.4%, and 53.1% of requests, respectively. Statistically significant differences existed when comparing rates meeting criteria between WI HEMS and CAMTS and between WI HEMS and NAEMSP guidelines (p-value <0.0001). This was true in all subgroups except STEMI, which did not show significant difference. No difference existed between rates for CAMTS and NAEMSP guidelines in any group.

CONCLUSION

Significant difference between Wisconsin HEMS utilization versus NAEMSP guidelines, and between Wisconsin HEMS utilization and CAMTS guidelines in all subgroups except STEMI patients exist. No statistically significant difference existed between NAEMSP and CAMTS guidelines.

Logistics of air medical transport: When and where does helicopter transport reduce prehospital time for trauma?

BACKGROUND

Trauma is a time sensitive disease. Helicopter emergency medical services (HEMS) have shown benefit over ground emergency medical services (GEMS), which may be related to reduced prehospital time. The distance at which this time benefit emerges depends on many factors that can vary across regions. Our objective was to determine the threshold distance at which HEMS has shorter prehospital time than GEMS under different conditions.

METHODS

Patients in the Pennsylvania trauma registry 2000 to 2013 were included. Distance between zip centroid and trauma center was calculated using straight-line distance for HEMS and driving distance from geographic information systems network analysis for GEMS. Contrast margins from linear regression identified the threshold distance at which HEMS had a significantly lower prehospital time than GEMS, indicated by nonoverlapping 95% confidence intervals. The effect of peak traffic times and adverse weather on the threshold distance was evaluated. Geographic effects across EMS regions were also evaluated.

RESULTS

A total of 144,741 patients were included with 19% transported by HEMS. Overall, HEMS became faster than GEMS at 7.7 miles from the trauma center (p = 0.043). Helicopter emergency medical services became faster at 6.5 miles during peak traffic (p = 0.025) compared with 7.9 miles during off-peak traffic (p = 0.048). Adverse weather increased the distance at which HEMS was faster to 17.1 miles (p = 0.046) from 7.3 miles in clear weather (p = 0.036). Significant variation occurred across EMS regions, with threshold distances ranging from 5.4 to 35.3 miles. There was an inverse but non-significant relationship between urban population and threshold distance across EMS regions (ρ, -0.351, p = 0.28).

CONCLUSION

This is the first study to demonstrate that traffic, weather, and geographic region significantly impact the threshold distance at which HEMS are faster than GEMS. Helicopter emergency medical services was faster at shorter distances during peak traffic while adverse weather increased this distance. The threshold distance varied widely across geographic region. These factors must be considered to guide appropriate HEMS triage protocols.

LEVEL OF EVIDENCE

Therapeutic, level IV.

Multi-Institutional Multidisciplinary Injury Mortality Investigation in the Civilian Pre-Hospital Environment (MIMIC): a methodology for reliably measuring prehospital time and distance to definitive care

The detailed study of prehospital injury death is critical to advancing trauma and emergency care, as circumstance and causality have significant implications for the development of mitigation strategies. Though there is no true 'Golden Hour,' the time from injury to care is a critical element in the analysis matrix, particularly in patients with severe injury. Currently, there is no standard method for the assessment of time to definitive care after injury among prehospital deaths. This article describes a methodology to estimate total prehospital time and distance for trauma patients transported via ground emergency medical services and helicopter emergency medical services using a geographic information system. Data generated using this method, along with medical examiner and field investigation reports, will be used to estimate the potential survivability of prehospital trauma deaths occurring in five US states and the District of Columbia as part of the Multi-Institutional Multidisciplinary Injury Mortality Investigation in the Civilian Pre-Hospital Environment study. One goal of this work is to develop standard metrics for the assessment of total prehospital time and distance, which can be used in the future for more complex spatial analyses to gain a deeper understanding of trauma center access. Results will be used to identify high priority areas for research and development in injury prevention, trauma system performance improvement, and public health.

Out-of-hospital Times Using Helicopters Versus Ground Services for Emergency Patients

OBJECTIVE

Minimizing out-of-hospital time reduces morbidity and mortality in patients with severe trauma, acute coronary syndrome, or acute stroke. Our objective was to compare out-of-hospital times by helicopter versus ground services when the estimated time of arrival on the scene was over 20 minutes.

METHODS

We proposed a retrospective observational monocentric study following 2 cohorts. The helicopter group and the ground group included patients with severe trauma, acute coronary syndrome, or acute stroke transported by helicopter or ground services.

RESULTS

Two hundred thirty-nine patients were included; 118 were in the ground group, and 121 were in the helicopter group. Distances for the helicopter group were higher (62.1 ± 22.5 km vs. 27.6 ± 10.4 km, P < .001). When distances were over 35 km, the helicopter group was faster. We identified distance, need for surgery, and intensive care hospitalization as 3 predicting factors for choosing helicopters over ground modes of transport.

CONCLUSION

In cases of severe trauma, acute coronary syndrome, or acute stroke, emergency medical helicopter transport can be chosen over ground transport when patients are in a severe state and when the distance is further than 35 km from the hospital.

Spatial methods for evaluating critical care and trauma transport: A scoping review

PURPOSE

The objective of this scoping review is to inform future applications of spatial research regarding transportation of critically ill patients. We hypothesized that this review would reveal gaps and limitations in the current research regarding use of spatial methods for critical care and trauma transport research.

MATERIALS AND METHODS

Four online databases, Ovid Medline, PubMed, Embase and Scopus, were searched. Studies were selected if they used geospatial methods to analyze a patient transports dataset. 12 studies were included in this review.

RESULTS

Majority of the studies employed spatial methods only to calculate travel time or distance even though methods and tools for more complex spatial analyses are widely available. Half of the studies were found to focus on hospital bypass, 2 studies focused on transportation (air or ground) mode selection, 2 studies compared predicted versus actual travel times, and 2 studies used spatial modeling to understand spatial variation in travel times.

CONCLUSIONS

There is a gap between the availability of spatial tools and their usage for analyzing and improving medical transportation. The adoption of geospatially guided transport decisions can meaningfully impact healthcare expenditures, especially in healthcare systems looking to strategically control expenditures with minimum impact on patient outcomes.

Spatial analysis for regional behavior of patients with mental disorders in Japan

AIM

The aim of our study was to clarify the geographical movement of patients treated in psychiatric facilities, which can provide important information on the resources and health-care system of psychiatric services.

METHODS

We conducted an analysis of nationwide data on psychiatric patients, collected as an additional survey to the conventional '630 survey' in 2014. For the 151 848 initially admitted inpatients during 6 months and the 144 401 outpatients on a specific day, we identified whether a patient was admitted to a psychiatric facility located in the same medical area as his/her residence. We estimated percentages of being from (i) within the medical area, (ii) within the prefecture, and (iii) outside the prefecture, using a Bayesian statistical approach for each secondary medical area.

RESULTS

The inpatients moved across wider areas than did the outpatients. Almost all inpatients and outpatients received their medical treatment at hospitals/clinics within their prefecture of residence.

CONCLUSION

The current mental health medical system in Japan has been operating according to prefecture unit; thus, it may be appropriate to plan a medical system at a prefectural level.

It's All About Location, Location, Location: A New Perspective on Trauma Transport

OBJECTIVE

To determine the effect of aeromedical transport on trauma mortality when accounting for geographic factors.

BACKGROUND

The existing literature on the mortality benefit of aeromedical transport on trauma mortality is controversial. Studies examining patient and injury characteristics find higher mortality, whereas studies measuring injury severity find a protective effect. Previous studies have not adjusted for the time and distance that would have been traveled had a helicopter not been used.

METHODS

Retrospective analysis of an institutional trauma registry. We compared mortality among adult patients (≥15 years) transported from the scene of injury to our level I trauma center by air or ground (January 1, 2000-December 31, 2010) using univariate comparisons and multivariable logistic regression. Regression models were constructed to incrementally account for patient demographics and injury mechanism, followed by injury severity, and, finally, by network bands for drive time and roadway distance as predicted by geographic information systems.

RESULTS

Of 4522 eligible patients, 1583 (35%) were transported by air. Patients transported by air had higher unadjusted mortality (4.1% vs 1.9%, P < 0.05). In multivariable modeling, including patient demographics and type of injury, helicopter transport predicted higher mortality than ground transport (odds ratio [OR] 2.4, 95% confidence interval [CI] 1.2-4.0). After adding validated injury severity measures to the model, helicopter transport predicted lower mortality (OR 0.7, 95% CI 0.3-0.9). Finally, including geographic covariates found that helicopter transport was not associated with mortality (OR 1.1, 95% CI 0.6-2.3).

CONCLUSIONS

Helicopter transport does not impart a survival benefit for trauma patients when geographic considerations are taken into account.

Helicopter transport improves survival following injury in the absence of a time-saving advantage

BACKGROUND

Although survival benefits have been shown at the population level, it remains unclear what drives the outcome benefits for helicopter emergency medical services (HEMS) in trauma. Although speed is often cited as the vital factor of HEMS, we hypothesized a survival benefit would exist in the absence of a time savings over ground emergency medical services (GEMS). The objective was to examine the association of survival with HEMS compared with GEMS transport across similar prehospital transport times.

METHODS

We used a retrospective cohort of scene HEMS and GEMS transports in the National Trauma Databank (2007-2012). Propensity score matching was used to match HEMS and GEMS subjects on the likelihood of HEMS transport. Subjects were stratified by prehospital transport times in 5-minute increments. Conditional logistic regression determined the association of HEMS with survival across prehospital transport times strata controlling for confounders. Transport distance was estimated from prehospital transport times and average HEMS/GEMS transport speeds.

RESULTS

There were 155,691 HEMS/GEMS pairs matched. HEMS had a survival benefit over GEMS for prehospital transport times between 6 and 30 minutes. This benefit ranged from a 46% increase in odds of survival between 26 and 30 minutes (adjusted odds ratio [AOR], 1.46; 95% CI, 1.11-1.93; P < .01) to an 80% increase in odds of survival between 16 and 20 minutes (AOR, 1.80; 95% CI, 1.51-2.14; P < .01). This prehospital transport times window corresponds to estimated transport distance between 14.3 and 71.3 miles for HEMS and 3.3 and 16.6 miles for GEMS.

CONCLUSION

When stratified by prehospital transport times, HEMS had a survival benefit concentrated in a window between 6 and 30 minutes. Because there was no time-savings advantage for HEMS, these findings may reflect care delivered by HEMS providers.

Differential patterns, trends and hotspots of road traffic injuries on different road networks in Vellore district, southern India

OBJECTIVE

To describe spatial and temporal profiles of Road Traffic Injuries (RTIs) on different road networks in Vellore district of southern India.

METHODS

Using the information in the police maintained First Information Reports (FIRs), daily time series of RTI counts were created and temporal characteristics were analysed with respect to the vehicle, road types and time of the day for the period January 2005 to May 2007. Daily incidence and trend of RTIs were estimated using a Poisson regression analysis.

RESULTS

Of the reported 3262 RTIs, 52% had occurred on the National Highway (NH). The overall RTI rate on the NH was 8.8/100 000 vehicles per day with significantly higher pedestrian involvement. The mean numbers of RTIs were significantly higher on weekends. Thirteen percentage of all RTIs were associated with fatalities. Hotspots are major town junctions, and RTI rates differ over different stretches of the NH.

CONCLUSION

In India, FIRs form a valuable source of RTI information. Information on different vehicle profile, RTI patterns, and their spatial and temporal trends can be used by administrators to devise effective strategies for RTI prevention by concentrating on the high-risk areas, thereby optimising the use of available personnel and resources.

Geographic access to high capability severe acute respiratory failure centers in the United States

OBJECTIVE

Optimal care of adults with severe acute respiratory failure requires specific resources and expertise. We sought to measure geographic access to these centers in the United States.

DESIGN

Cross-sectional analysis of geographic access to high capability severe acute respiratory failure centers in the United States. We defined high capability centers using two criteria: (1) provision of adult extracorporeal membrane oxygenation (ECMO), based on either 2008-2013 Extracorporeal Life Support Organization reporting or provision of ECMO to 2010 Medicare beneficiaries; or (2) high annual hospital mechanical ventilation volume, based 2010 Medicare claims.

SETTING

Nonfederal acute care hospitals in the United States.

MEASUREMENTS AND MAIN RESULTS

We defined geographic access as the percentage of the state, region and national population with either direct or hospital-transferred access within one or two hours by air or ground transport. Of 4,822 acute care hospitals, 148 hospitals met our ECMO criteria and 447 hospitals met our mechanical ventilation criteria. Geographic access varied substantially across states and regions in the United States, depending on center criteria. Without interhospital transfer, an estimated 58.5% of the national adult population had geographic access to hospitals performing ECMO and 79.0% had geographic access to hospitals performing a high annual volume of mechanical ventilation. With interhospital transfer and under ideal circumstances, an estimated 96.4% of the national adult population had geographic access to hospitals performing ECMO and 98.6% had geographic access to hospitals performing a high annual volume of mechanical ventilation. However, this degree of geographic access required substantial interhospital transfer of patients, including up to two hours by air.

CONCLUSIONS

Geographic access to high capability severe acute respiratory failure centers varies widely across states and regions in the United States. Adequate referral center access in the case of disasters and pandemics will depend highly on local and regional care coordination across political boundaries.

The association between air ambulance distribution and trauma mortality

OBJECTIVE

To determine whether increasing distance between helicopter ambulance airbase and either home residence or referring facility is associated with an increased risk of injury-related mortality.

BACKGROUND

A dramatic increase in the absolute number and utilization of Helicopter Emergency Medical Services transports has occurred in the management of the critically injured patients. HEMS are resource intensive, and the most efficient geographic distribution of airbases necessary to improve patient outcomes is unknown.

METHODS

We performed a retrospective analysis of 244,293 adult trauma patients who were treated at a designated trauma center (TC) in Pennsylvania during the period 1997 to 2007, using the Pennsylvania Trauma Outcomes Study data set. We performed a multivariate analysis, adjusting for differences in case mix, to determine whether airbase proximity to either residence or referring facility is associated with injury-related mortality.

RESULTS

For patients residing distant (>20 miles) from a TC, increasing distance from an airbase is associated with an increased risk of death; for each mile, the risk of mortality increases by approximately 1% (adjusted odds ratio, 1.011; 95% confidence interval, 1.002-1.018; P = 0.02). There is no additional benefit to living close (<25 miles) to more than 1 airbase. However, most airbases are positioned near TC and other airbases. Despite the proliferation of helicopter ambulances, 18.1% of patients who did not live near a TC also did not live near airbase.

CONCLUSIONS

For individuals residing distant from a TC, proximity to 1 airbase is associated with reduced risk of death. No additional benefit is observed when airbases are positioned close to a TC or other airbases.

Predicting ambulance time of arrival to the emergency department using global positioning system and Google maps

OBJECTIVE

To derive and validate a model that accurately predicts ambulance arrival time that could be implemented as a Google Maps web application.

METHODS

This was a retrospective study of all scene transports in Multnomah County, Oregon, from January 1 through December 31, 2008. Scene and destination hospital addresses were converted to coordinates. ArcGIS Network Analyst was used to estimate transport times based on street network speed limits. We then created a linear regression model to improve the accuracy of these street network estimates using weather, patient characteristics, use of lights and sirens, daylight, and rush-hour intervals. The model was derived from a 50% sample and validated on the remainder. Significance of the covariates was determined by p < 0.05 for a t-test of the model coefficients. Accuracy was quantified by the proportion of estimates that were within 5 minutes of the actual transport times recorded by computer-aided dispatch. We then built a Google Maps-based web application to demonstrate application in real-world EMS operations.

RESULTS

There were 48,308 included transports. Street network estimates of transport time were accurate within 5 minutes of actual transport time less than 16% of the time. Actual transport times were longer during daylight and rush-hour intervals and shorter with use of lights and sirens. Age under 18 years, gender, wet weather, and trauma system entry were not significant predictors of transport time. Our model predicted arrival time within 5 minutes 73% of the time. For lights and sirens transports, accuracy was within 5 minutes 77% of the time. Accuracy was identical in the validation dataset. Lights and sirens saved an average of 3.1 minutes for transports under 8.8 minutes, and 5.3 minutes for longer transports.

CONCLUSIONS

An estimate of transport time based only on a street network significantly underestimated transport times. A simple model incorporating few variables can predict ambulance time of arrival to the emergency department with good accuracy. This model could be linked to global positioning system data and an automated Google Maps web application to optimize emergency department resource use. Use of lights and sirens had a significant effect on transport times.

Impact of prehospital mode of transport after severe injury: a multicenter evaluation from the Resuscitation Outcomes Consortium

BACKGROUND

There is ongoing controversy about the relative effectiveness of air medical versus ground transportation for severely injured patients. In some systems, air medical crews may provide a higher level of care but may require longer transport times. We sought to evaluate the impact of mode of transport on outcome based on analysis of data from two randomized trials of prehospital hypertonic resuscitation.

METHODS

Injured patients were enrolled based on prehospital evidence of hypovolemic shock (systolic blood pressure ≤70 mm Hg or systolic blood pressure = 71-90 mm Hg with heart rate ≥108 bpm) or severe traumatic brain injury (TBI; Glasgow Coma Scale score ≤8). Patient demographics, injury severity, and physiology were compared based on mode of transport. Multivariate logistic regression was used to determine the impact of mode of transport on 24-hour and 28-day survival for all patients and 6-month extended Glasgow Outcome Scale for patients with TBI, adjusting for differences in injury severity.

RESULTS

Included were 2,049 patients, of which 703 (34%) were transported by air. Patients transported by air were more severely injured (mean Injury Severity Score, 30.3 vs. 22.8; p < 0.001), more likely to be in the TBI cohort (70% vs. 55.4%; p < 0.001), and more likely blunt mechanism (94.0% vs. 78.1%; p < 0.001). Patients transported by air had higher rates of prehospital intubation (81% vs. 36%; p < 0.001), received more intravenous fluids (mean 1.3 L vs. 0.8 L; p < 0.001), and had longer prehospital times (mean 76.1 minutes vs. 43.5 minutes; p < 0.001). Adjusted analysis revealed no significant impact of mode of transport on survival or 6-month neurologic outcome (air transport-28-day survival: odds ratio, 1.11; 95% confidence interval, 0.82-1.51; 6-month extended Glasgow Outcome Scale score ≤4: odds ratio, 0.94; 95% confidence interval, 0.68-1.31).

CONCLUSION

There was no difference in the adjusted clinical outcome according to mode of transport. However, air medical transported more severely injured patients with more advanced life support procedures and longer prehospital time.

LEVEL OF EVIDENCE

III.

Geographical information systems and health: current state and future directions

This paper provides an introduction to Geographical Information Systems (GIS) and how they can be used. It reviews the current state of GIS use in health care before identifying the barriers to more pervasive use of GIS in health. Finally, it makes recommendations for the direction of health GIS research over the next decade and concludes with a call to action to health informatics researchers to stop ignoring a tool and methodology that has such immense potential for improving the health of our communities.

Geographical variation in ambulance calls is associated with socioeconomic status

OBJECTIVES

  The main objective was to explore the relationship between socioeconomic status and the spatial distribution of ambulance calls, as modeled in the island nation of Singapore, at the Development Guide Plan (DGP) level (equivalent to census tracts in the United States).

METHODS

  Ambulance call data came from a nationwide registry from January to May 2006. We used a conditional autoregressive (CAR) model to create smoothed maps of ambulance calls at the DGP level, as well as spatial regression models to evaluate the relationship between the risk of calls with regional measures of socioeconomic status, such as household type and both personal and household income.

RESULTS

  There was geographical correlation in the ambulance calls, as well as a socioeconomic gradient in the relationship with ambulance calls of medical-related (but not trauma-related) reasons. For instance, the relative risk (RR) of medical ambulance calls decreased by a factor of 0.66 (95% credible interval [CrI] = 0.56 to 0.79) for every 10% increase in the proportion of those with monthly household income S$5000 and above. The top three DGPs with the highest risk of medical-related ambulance calls were Changi (RR = 29, 95% CrI = 24 to 35), downtown core (RR = 8, 95% CrI = 6 to 9), and Orchard (RR = 5, 95% CrI = 4 to 6).

CONCLUSIONS

  This study demonstrates the utility of geospatial analysis to relate population socioeconomic factors with ambulance call volumes. This can serve as a model for analysis of other public health systems.

Helicopter evacuation of trauma victims in Los Angeles: does it improve survival?

BACKGROUND

The purpose of this study was to investigate the relationship between the method of transport after injury and survival among trauma patients admitted to a Level 1 trauma facility in Los Angeles, California.

METHODS

The trauma registry of LAC+USC Medical Center was reviewed to identify all injured patients evacuated by emergency medical service (EMS) from the injury scene from 1998 to 2007. The study population was divided into those who were airlifted (HEMS) and those who were transported by ground emergency medical service (GEMS) with transportation time that exceeded 30 minutes (GEMS > 30 minutes).

RESULTS

During the 10-year study period, 1,836 patients were airlifted (helicopters for emergency medical service (HEMS)) and 1,537 patients were ground transported (GEMS > 30 minutes). HEMS patients suffered more frequently a penetrating injury (19% vs. 11%, p < 0.001), presented more often hypotensive to the emergency department (4% vs. 1%, p < 0.001), had more frequently a Glasgow Coma Scale (GCS) < or = 8 (9% vs. 3%, p < 0.001) and required more often an intubation at the injury scene (1.6% vs. 0.4%, p < 0.001). However, the transportation time and the total prehospital time were significantly shorter for airlifted patients. After multivariable analysis, the difference in mortality between the two transport modalities was not significant (adjusted odds ratio (95% confidence interval, 0.72 (0.22, 2.35); p = 0.596).

CONCLUSIONS

In a metropolitan Los Angeles trauma system, EMS helicopter transportation of injured patients does not appear to improve overall adjusted survival after injury. There is however a potential benefit for severely injured subgroups of patients due to the shorter prehospital times.

Landing sites and intubation may influence helicopter emergency medical services on-scene time

BACKGROUND

Reduced transport time of patients from the scene of an accident to definitive surgical treatment is one important reason to employ ambulance helicopters on trauma missions. However, if the helicopter is unable to land close to the scene, the transport time may be increased compared to transport with ground ambulance, due to time-consuming transfer of the patient between vehicles.

OBJECTIVE

The objective of this study was to evaluate how the landing site, as determined by distance from the scene, and rapid sequence intubation (RSI) affected on-scene time (OST).

METHODS

This was a prospective observational study performed during a 12-month period in a mixed urban and rural anesthesiologist-staffed Helicopter Emergency Medical Service in Norway. Data regarding the landing sites, the accident, and patient treatment were recorded.

RESULTS

A total of 252 primary trauma missions were included in the study. In 75% of the missions, the aircraft landed<50 meters from the scene, and in 7% the distance exceeded 200 meters. Mean OST when the patient was not intubated was 14.5 min (median 14 min). When an RSI was performed, the mean OST was significantly higher (22.7 min, median 20 min; p<0.001).

CONCLUSION

Usually, a helicopter can land close to the accident scene and the location of the landing site does not contribute to a delay in arrival of the patient at the hospital. The OST is significantly higher, however, in those patients who receive endotracheal intubation before take-off. This reflects the time needed for intubation, as well as the increased complexity and workload when the patient is severely injured.

Geographic cluster analysis of injury severity and hospital resource use in a regional trauma system

OBJECTIVES

To determine clusters of trauma incidents with high injury severity and resource utilization and to test their association with census demographic information.

METHODS

Using "trauma band" unique identifiers and probabilistic linkage for unmatched cases, we matched injury location information collected from a centralized regional trauma communications center to the state trauma system registry for patients directly transported to two level I trauma centers for the years 2001-2003 in a three-county area. The injury locations were aggregated at the census tract level using a geographic information system (GIS). Moran's I analysis was used to determine clusters of census tracts that had a high incidence of either total trauma injuries, Injury Severity Scores (ISSs) >15, or high resource use (in-hospital mortality, admission to the intensive care unit, or major nonorthopedic surgery). These clusters were then tested for association with census tract demographics using logistic regression.

RESULTS

Eight thousand seven hundred fifty-one injured persons were directly transported from the tricounty area to a trauma center during the study period. The mean (+/- standard deviation) age was 37 +/- 21 years, 67.4% were male, 18.9% had ISSs >15, and 29.8% had a high-resource-use indicator. Moran's I analysis demonstrated a single large cluster of incidents for total injuries, ISS >15, and occurrence of a high-resource-use indictor that overlapped except for one small census tract. Logistic regression revealed that the high-risk cluster was associated with a higher prevalence of nonwhite population and vacant housing and a lower prevalence of foreign-born residents and family housing.

CONCLUSIONS

GIS cluster analysis demonstrated high-risk census tracts for trauma incidents and associated population demographics. Geospatial analyses may assist injury prevention interventions and emergency medical services deployment strategies for trauma.

GIS and injury prevention and control: history, challenges, and opportunities

Intentional and unintentional injury is the leading cause of death and potential years of life lost in the first four decades of life in industrialized countries around the world. Despite surgical innovations and improved access to emergency care, research has shown that certain populations remain particularly vulnerable to the risks and consequences of injury. Recent evidence has shown that the analytical, data linkage, and mapping tools of geographic information systems (GIS) technology provide can further address these determinants and identify populations in need. This paper traces the history of injury prevention and discusses current and future challenges in furthering our understanding of the determinants of injury through the use of GIS.

Geography and travel distance impact emergency department visits

BACKGROUND

Little has been written about the geographic basis of emergency department (ED) visits.

OBJECTIVE

The objective of this study is to describe the impact of geography on ED visits.

METHODS

A retrospective analysis was conducted of ED visits during a 1-year period at a single institution using spatial interaction analysis that models the pattern of flow between a series of origins (census block groups) and a destination (ED). Patients were assigned to census block groups based upon their verified home address. The study hospital is the only Level I trauma, pediatric, and tertiary referral center in the area. There are 11 other hospitals with EDs within a 40-mile radius. Each patient visit within this radius, including repeat visits, was included. Patients with an invalid home address, a post office box address, or those who lived outside a 40-mile radius were excluded. ED visits per 100 population were calculated for each census block group.

RESULTS

There were 98,584 (95%) visits by 63,524 patients that met study inclusion criteria. Visit rates decreased with increasing distance from the ED (p < 0.0001). Nineteen percent of patients lived within 2 miles, 48% within 4 miles, and 92% within 12 miles of the ED. The Connecticut border, 7 miles south of the ED (p < 0.0001), the Connecticut River, 1 mile west of the ED (p < 0.0001), and the presence of a competing ED within 1 mile (p < 0.0001) negatively impacted block group ED visit rates. Travel distance was related to the percentage of visits that were high acuity (p < 0.0001), daytime (p < 0.01), or resulted in admission (p < 0.0001).

CONCLUSIONS

Geography and travel distance significantly impact ED visits.

Urban sprawl and delayed ambulance arrival in the U.S

BACKGROUND

Minimizing emergency medical service (EMS) response time is a central objective of prehospital care, yet the potential influence of built environment features such as urban sprawl on EMS system performance is often not considered.

PURPOSE

This study measures the association between urban sprawl and EMS response time to test the hypothesis that features of sprawling development increase the probability of delayed ambulance arrival.

METHODS

In 2008, EMS response times for 43,424 motor-vehicle crashes were obtained from the Fatal Analysis Reporting System, a national census of crashes involving > or =1 fatality. Sprawl at each crash location was measured using a continuous county-level index previously developed by Ewing et al. The association between sprawl and the probability of a delayed ambulance arrival (> or =8 minutes) was then measured using generalized linear mixed modeling to account for correlation among crashes from the same county.

RESULTS

Urban sprawl is significantly associated with increased EMS response time and a higher probability of delayed ambulance arrival (p=0.03). This probability increases quadratically as the severity of sprawl increases while controlling for nighttime crash occurrence, road conditions, and presence of construction. For example, in sprawling counties (e.g., Fayette County GA), the probability of a delayed ambulance arrival for daytime crashes in dry conditions without construction was 69% (95% CI=66%, 72%) compared with 31% (95% CI=28%, 35%) in counties with prominent smart-growth characteristics (e.g., Delaware County PA).

CONCLUSIONS

Urban sprawl is significantly associated with increased EMS response time and a higher probability of delayed ambulance arrival following motor-vehicle crashes in the U.S. The results of this study suggest that promotion of community design and development that follows smart-growth principles and regulates urban sprawl may improve EMS performance and reliability.

Distance impacts mortality in trauma patients with an intubation attempt

OBJECTIVE

Out-of-hospital endotracheal intubation (OOH-ETI) has been associated with adverse outcomes; whether transport distance changes this relationship is unclear. We sought to determine whether patients injured farther from the hospital benefit more from OOH-ETI than those injured closer.

METHODS

We performed a retrospective cohort analysis of trauma patients > 14 years old transported to two Level 1 trauma centers and surviving to admission from 2000 to 2003. We used probabilistically linked geographic data to calculate transport distance. To adjust for the nonrandom selection of patients for OOH-ETI, we used a propensity score based on clinical variables: prehospital physiology, demographics, transport mode, mechanism, comorbidities, Abbreviated Injury Scale head injury score >or= 3, Injury Severity Score, blood transfusion, and major surgery. Propensity-adjusted multivariable logistic regression with mode of transport was used to test the interaction between distance and OOH-ETI.

RESULTS

8,786 patients were included, 534 with OOH-ETI. Patients with OOH-ETI had higher adjusted mortality (odds ratio [OR] 2.06, 95% confidence interval [CI] 1.33-3.18), and there was a significant interaction between distance and OOH-ETI (p = 0.02). Patients with shortest distances had the highest mortality (OR 3.98, 95% CI 2.08-7.60). Probability of mortality was higher with OOH-ETI across all distances and increased for patients closest to the hospital. Helicopter transport was associated with improved survival.

CONCLUSIONS

Prehospital intubation is associated with increased mortality among trauma patients at all distances from the hospital. Patients with the shortest transport distances had the greatest mortality associated with OOH-ETI, whereas helicopter transport was associated with improved survival. The event location and ensuing distance to the hospital are another factor to consider when instituting and modifying OOH airway protocols.

Regionalization of care for ST-segment elevation myocardial infarction: is it too soon?

Interest in regionalization of the care of acute ST-segment elevation myocardial infarction (STEMI) has gained momentum recently. Optimal treatment of STEMI involves balancing time to treatment and reperfusion options. Primary percutaneous coronary intervention, when performed in a timely fashion, has been shown to be more effective than fibrinolysis. However, numerous practical barriers prevent many STEMI patients from receiving primary percutaneous coronary intervention. In an effort to increase beneficial primary percutaneous coronary intervention administration to STEMI patients, health care leaders have proposed regionalized STEMI care networks with advanced emergency medical services (EMS) involvement. Constructing regionalized STEMI networks presents a policy challenge because this shift in STEMI care would require changes in current EMS and emergency medicine practices. Therefore, we present various perspectives and issues that decisionmakers and system organizers must address properly before deciding whether to adopt this new model of care. Reorganizing STEMI care in a manner analogous to how trauma and stroke care are currently triaged and treated appeals intuitively; however, given the absence of evidence that STEMI regionalization actually improves patient outcomes and is cost-effective, more research is needed to determine whether STEMI regionalization is an efficient model for providing evidence-based care. The concept of STEMI regionalization represents an effort to inform policy according to evidence-based medicine, but real-world quality, geospatial, financial, cost, business, resource, and practice barriers present obstacles to implementing this concept efficiently and effectively.

Optimization of aeromedical base locations in New Mexico using a model that considers crash nodes and paths

In a recent paper, Tokar Erdemir et al. (2008) introduce models for service systems with service requests originating from both nodes and paths. We demonstrate how to apply and extend their approach to an aeromedical base location application, with specific focus on the state of New Mexico (NM). The current aeromedical base locations of NM are selected without considering motor vehicle crash paths. Crash paths are the roads on which crashes occur, where each road segment has a weight signifying relative crash occurrence. We analyze the loss in accident coverage and location error for current aeromedical base locations. We also provide insights on the relevance of considering crash paths when selecting aeromedical base locations. Additionally, we look briefly at some of the tradeoff issues in locating additional trauma centers vs. additional aeromedical bases in the current aeromedical system of NM. Not surprisingly, tradeoff analysis shows that by locating additional aeromedical bases, we always attain the required coverage level with a lower cost than with locating additional trauma centers.

Using geographic information systems in injury research

PURPOSE

To provide an overview of geographic information systems (GIS) and to discuss current and future applications in injury and trauma research.

DESIGN

Literature review and discourse of GIS technology related to injury and trauma research.

METHOD

A search of scientific literature databases, text books, and online resources was undertaken to describe the current and prospective uses of GIS in injury and trauma research.

RESULTS

Geographic information systems are computerized mapping systems that link information from different data sets spatially. The advantage of GIS is the capability to graphically display different attributes of an area in a way that is easily interpretable. Geographic information systems have been used to study injury rates, describe populations at risk for injury, examine access to trauma care, and develop and assess injury prevention programs.

CONCLUSIONS

Geographic information systems are tools for injury researchers to analyze injury rates and risks and to describe their results with colorful maps and graphics that allow the public to see how injuries affect their communities.

A geographic information system to study trauma epidemiology in India

BACKGROUND

Geographic Information Systems (GIS) describe the topography and chronology of events in a defined vector space. GIS may also be used for an integrated analysis of environmental and road-related risk factors for traffic accidents.

METHODS

In a retrospective study, various features of 165 road crashes were linked to a GIS-generated digital map of an area close to a national highway in India. By overlay tools, clusters of accidents were identified, and color-coded according to accident mechanisms and injury patterns.

RESULTS

Spatial analysis revealed a cluster with a high incidence of motorbike injuries resulting in fractures. Examination of the spot demonstrated the risky combination of a speed breaker and a broken traffic light. After fixing the light, no further accidents occurred at the site.

CONCLUSION

GIS is a promising technology for geo-referencing accident data, and may be a valuable tool to identify areas of priority for injury prevention in India.

Determining geographic areas and populations with timely access to cardiac catheterization facilities for acute myocardial infarction care in Alberta, Canada

Background

This study uses geographic information systems (GIS) as a tool to evaluate and visualize the general accessibility of areas within the province of Alberta (Canada) to cardiac catheterization facilities. Current American and European guidelines suggest performing catheterization within 90 minutes of the first medical contact. For this reason, this study evaluates the populated places that are within a 90 minute transfer time to a city with a catheterization facility. The three modes of transport considered in this study are ground ambulance, rotary wing air ambulance and fixed wing air ambulance.

Methods

Reference data from the Alberta Chart of Call were interpolated into continuous travel time surfaces. These continuous surfaces allowed for the delineation of isochrones: lines that connect areas of equal time. Using Dissemination Area (DA) centroids to represent the adult population, the population numbers were extracted from the isochrones using Statistics Canada census data.

Results

By extracting the adult population from within isochrones for each emergency transport mode analyzed, it was found that roughly 70% of the adult population of Alberta had access within 90 minutes to catheterization facilities by ground, roughly 66% of the adult population had access by rotary wing air ambulance and that no population had access within 90 minutes using the fixed wing air ambulance. An overall understanding of the nature of air vs. ground emergency travel was also uncovered; zones were revealed where the use of one mode would be faster than the others for reaching a facility.

Conclusion

Catheter intervention for acute myocardial infarction is a time sensitive procedure. This study revealed that although a relatively small area of the province had access within the 90 minute time constraint, this area represented a large proportion of the population. Within Alberta, fixed wing air ambulance is not an effective means of transporting patients to a catheterization facility within the 90 minute time frame, though it becomes advantageous as a means of transportation for larger distances when there is less urgency.

The Fastest Route Between Two Points is Not Always a Straight Line: An Analysis of Air and Land Transfer of Nonpenetrating Trauma Patients

BACKGROUND

The distance beyond which helicopter transport is faster than ground for interfacility transfer of trauma patients has not been established. Our objective was to determine whether such a threshold exists.

METHODS

A retrospective cohort study was conducted involving 243 patients transported by land and 139 patients by air from 13 sites during a 3-year period. Time intervals between critical events were compared for the two modes of transport at each site.

RESULTS

The time interval between the decision to transfer and the actual departure time was shorter for patients transferred by land from all sites studied (mean 41.3 versus 89.7 minutes, p < 0.001). The travel time was shorter by helicopter from all sites (mean 58.4 versus 78.9 minutes, p < 0.001). The time between the decision to transfer and the arrival at the trauma center was similar at most sites but faster by land overall (mean 120.3 versus 150.0 minutes, p = 0.014). No threshold was detected beyond which helicopter transport was superior.

CONCLUSIONS

Several factors other than the distance to be traveled determine the time required for interfacility transfer of trauma patients. A fixed distance threshold beyond which helicopter transport should be used does not exist. The decision as to which mode of transport to use for emergent trauma patient transfers should be based upon multiple factors including the distance traveled and ambulance availability, and must be individualized for each site that transfers patients.

Is air transport faster? A comparison of air versus ground transport times for interfacility transfers in a regional referral system

INTRODUCTION

Helicopter transport is often considered in an effort to minimize time to critical interventions, such as cardiac catheterization or arterial thrombolysis in stroke patients. However, for interfacility transports, the extra time considerations for helicopter preparation, takeoff, and time to get to the transferring hospital may not offset the slower transport times for local ground ambulances. The purpose of this study was to compare transport times for helicopter with traditional ground ambulance for interfacility transfers within a regional referral system.

METHODS

All patients transported from an outside hospital to the intensive care unit of the University of Wisconsin were eligible for this study. Equal numbers of patients transferred by ground and by helicopter from each facility were sequentially selected. The following intervals were compared: time from call to dispatch, time from dispatch to arrival at the referring hospital, time at the referring hospital, transport time to the receiving hospital, and total transport time.

RESULTS

One hundred forty-five patients were included in this study, transferred from 20 hospitals within the UW referral system. Dispatch times and time at the referring hospital were location independent, and each was shorter for ground transport. Ground dispatch times were 5+/-6 minutes, whereas for helicopter transport dispatch times were 17+/-8 (P<.001). Times at the referral hospital were on average longer for helicopter transport (31+/-11 minutes for air ambulance, 25+/-13 for ground; P=.008). Other intervals were location dependent. Arrivals were much more variable for ground transport, reflecting the fact that private ambulance services may have to travel some distance to reach the referring hospital (helicopter 18+/-8 minutes, ground 19+/-18 minutes). As expected, transport time from the referring hospital was shorter for helicopter transport. From each of the hospitals, average helicopter transport was as fast as the best ground transport.

CONCLUSION

Helicopter transport was faster than ground transport for interfacility transfer of patients from all hospitals studied in our referral system. Under optimal dispatch and transport conditions, the time difference from several hospitals was minimal. For stable patients for whom the only issue is time to critical procedure, it may be reasonable for those hospitals to try ground transport first if timely service is available to transport in that way. Even for those hospitals, helicopter transport should be considered for these patients if ground transport is not optimally available, as well as for patients in whom minimizing time outside of the hospital is a significant consideration, or when transport of such patients impacts emergency medical services availability to the community for a significant time.

Can a simple reminder letter improve numbering of single-family residences?

OBJECTIVE

To determine if a single mailing from the local volunteer fire department can increase the number of homes with proper, visible address numbering. Proper numbering is essential in rapidly locating a house during an emergency response.

METHODS

The study was conducted at a suburban/rural fire department providing EMS and fire suppression services to a 22 square mile area with residential mailboxes located at the street. During a hazard identification pre-plan tour, each house was examined and assigned a classification: (A) No number visible on the house or mailbox (improper); (B) Number on only one side of the mailbox (improper); (C) Number on both sides or the end of the mailbox, or visible on the house (proper). The homeowners of all residences with improper numbering (A or B) were sent a one-page letter, discussing the need for proper numbering. The tour was repeated six weeks later to determine whether deficiencies had been corrected. It was prospectively determined that a 25% improvement was sought.

RESULTS

During the pre-plan tour, 73 houses were classified as type A, 454 as type B, and 1706 as type C. At the re-visit, 135 (26%) of the type A and B homes had been properly numbered. Correction of deficiencies was better at type A homes (37, or 51%) than at type B homes (98, or 22%) (p < 0.001 by Chi-square).

CONCLUSION

For houses with improper numbering, a single mailing from the fire department can be effective in encouraging residents to post proper numbers.

When is the helicopter faster? A comparison of helicopter and ground ambulance transport times

BACKGROUND

A retrospective analysis of 7,854 ground ambulance and 1,075 helicopter transports was conducted.

METHODS

The 911-hospital arrival intervals for three transport methods were compared: ground, helicopter dispatched simultaneously with ground unit, and helicopter dispatched nonsimultaneously after ground unit response.

RESULTS

Compared with ground transports, simultaneously dispatched helicopter transports had significantly shorter 911-hospital arrival intervals at all distances greater than 10 miles from the hospital. Nonsimultaneously dispatched helicopter transport was significantly faster than ground at distances greater than 45 miles, and simultaneous helicopter dispatch was faster than nonsimultaneous at virtually all distances. Ground transport was significantly faster than either air transport modality at distances less than 10 miles from the hospital.

CONCLUSION

Ground ambulance transport provided the shortest 911-hospital arrival interval at distances less than 10 miles from the hospital. At distances greater than 10 miles, simultaneously dispatched air transport was faster. Nonsimultaneous dispatched helicopter transport was faster than ground if greater than 45 miles from the hospital.

How far is that by air? The derivation of an air: ground coefficient

The objective of this study was to derive a simple equation to convert distances between air miles traveled by a helicopter and ground miles traveled by an ambulance. We performed a retrospective analysis of a convenience sampling of 245 "lights and sirens" ground ambulance transports between 1993 and 1997. Ground distances were recorded from odometer miles for each transport. Air miles were calculated using the Global Positioning System (GPS), measuring the distance in a straight line from the scene to the hospital. Air and ground distances were entered into a computerized spreadsheet, and the correlation coefficient and regression equation were derived. A simple approximation equation was developed and compared against the derived regression equation. There was a strong linear correlation between ground miles and air miles at virtually all distances studied (R = 0.932, R(2) = 0.869). Regression analysis revealed the following relationship: Ground miles = 0.94 + 1.25 (air miles). This was simplified to an approximation of: Ground miles = 1.3 (air miles). The approximation equation yielded an answer within 1 mile of the regression equation for distances up to 40 air miles. It is concluded that in a mixed rural and urban EMS system, one may convert air and ground mileage estimates by using the simple relationship: Ground miles = 1.3 (air miles). This conversion coefficient may prove useful for EMS personnel in designing reasonable helicopter utilization policies, making accurate transport decisions and conducting research.

The utility of helicopter transport of trauma patients from the injury scene in an urban trauma system

BACKGROUND

Continuing controversy surrounding the value of scene helicopter evacuation of urban trauma victims led to the present study.

METHODS

A retrospective review was performed of all patients brought to our trauma center from the injury scene by helicopter from 1990 to 2001.

RESULTS

The study included 947 consecutive patients, 911 with blunt trauma and 36 with penetrating injuries. The mean Injury Severity Score (ISS) was 8.9. Fifteen patients died in the emergency department, 312 patients (33.5%) were discharged home from the emergency department (mean ISS, 2.7), and 620 patients were hospitalized (mean ISS, 11.4). Three hundred thirty-nine of the hospitalized patients (54.7%) had an ISS < or = 9; 148 patients had an ISS > or = 16. Eighty-four patients (8.9%) required early operation, mostly for open extremity fractures; only 17 patients (1.8%) underwent surgery for immediately life-threatening injuries. For 54.7% of the patients, the helicopter was judged to be clearly faster than would have been possible by ground transport. In 140 additional patients (14.8%) with prolonged scene time, the helicopter was probably faster than ground ambulance. Considering faster transport time and either the need for early operation or hospitalization with an ISS > or = 9 as advantageous, a maximum of 22.8% of the study population possibly benefited from helicopter transport.

CONCLUSION

The helicopter is used excessively for scene transport of trauma victims in our metropolitan trauma system. New criteria should be developed for helicopter deployment in the urban trauma environment.

Using a geographical information system to map the distribution of dentists in Ohio

BACKGROUND

Studies have reported that dental care is the highest unmet health care need in the United States and have evaluated this in terms of individual determinants of access and utilization. None of these studies took into consideration the provider issues of availability and accessibility or of spatial relations. The aim of this study was to analyze issues of provider availability and accessibility in Ohio using a geographical information system, or GIS.

METHODS

Three Ohio databases were geocoded using GIS software. The databases included all 6,132 dentists licensed to practice in Ohio, 1,898 dentists who had billed the state Medicaid program in 1998 and safety-net clinics that provided free or low-cost care. Each practitioner was mapped at the county and ZIP code levels.

RESULTS

Results are reported using maps at the county and ZIP code levels. The maps showed that 69.4 percent of dentists practiced in 12 metropolitan counties, 14 percent in 17 suburban counties and 16.6 percent in 59 rural counties (rural non-Appalachian counties plus Appalachian counties). In Appalachia, the dentist-to-population ratio was about one-half that of the metropolitan counties.

CONCLUSION

Obvious disparities exist in the distribution of dentists in Ohio, particularly in rural and Appalachian counties. The need to increase the availability of dentists in these counties is evident.

PRACTICE IMPLICATIONS

GIS is a useful tool for evaluating provider distribution and availability and planning programs to attract dentists to areas with small numbers of dentists.

Geographic epidemiology of gonorrhoea and chlamydia on a large military installation: application of a GIS system

OBJECTIVES

The geographic epidemiology of infectious diseases can help in identifying point source outbreaks, elucidating dispersion patterns, and giving direction to control strategies. We sought to establish a geographic information system (GIS) infectious disease surveillance system at a large US military post (Fort Bragg, North Carolina) using STDs as the initial outcome for the model.

METHODS

Addresses of incident cases were plotted onto digitised base maps of Fort Bragg (for on-post addresses) and surrounding Cumberland County, NC (for off-post addresses) using MAPINFO Version 5. We defined 26 geographic sectors on the installation. Active duty soldiers attending the post preventive medicine clinic were enrolled between July 1998 and June 1999.

RESULTS

Gonorrhoea (GC) was diagnosed in 210/2854 (7.4%) and chlamydia (CT) in 445/2860 (15.6%). African-American male soldiers were at higher risk for GC (OR = 4.6 (95% CL 3.0 to 7.2)) and chlamydia (OR = 2.0 (1.4 to 2.7)). For women, there were no ethnic differences in gonorrhoea prevalence, but chlamydia was higher in African-Americans (OR = 2.0 (1.4-2.7)). Rank and housing type were associated with gonorrhoea and chlamydia in men, but were not significant factors in women. For gonorrhoea, two geographic sectors had prevalences between 14.0%-16.5%, three between 10.3%-13.9%, three between 7.1%-10.2%, and five between 3.0%-7.1%. The geographic distribution demonstrated a core-like pattern where the highest sectors were contiguous and were sectors containing barracks housing lower enlisted grade personnel. In contrast, chlamydia prevalence was narrowly distributed.

CONCLUSION

GIS based disease surveillance was easily and rapidly implemented in this setting and should be useful in developing preventive interventions.