EMERGENCY MEDICAL SERVICES/ORIGINAL RESEARCH
Maryland’s Helicopter Emergency Medical Services Experience From 2001 to 2011: System Improvements and Patients’ Outcomes Jon Mark Hirshon, MD, PhD*; Samuel M. Galvagno, Jr, DO, PhD; Angela Comer, MPH; Michael G. Millin, MD, MPH; Douglas J. Floccare, MD, MPH; Richard L. Alcorta, MD; Benjamin J. Lawner, DO; Asa M. Margolis, DO, MPH; Jose V. Nable, MD, NRP; Robert R. Bass, MD *Corresponding Author. E-mail: [email protected], Twitter: @DrJonMark.
Study objective: Helicopter emergency medical services (EMS) has become a well-established component of modern trauma systems. It is an expensive, limited resource with potential safety concerns. Helicopter EMS activation criteria intended to increase efficiency and reduce inappropriate use remain elusive and difficult to measure. This study evaluates the effect of statewide field trauma triage changes on helicopter EMS use and patient outcomes. Methods: Data were extracted from the helicopter EMS computer-aided dispatch database for in-state scene flights and from the state Trauma Registry for all trauma patients directly admitted from the scene or transferred to trauma centers from July 1, 2000, to June 30, 2011. Computer-aided dispatch flights were analyzed for periods corresponding to field triage protocol modifications intended to improve system efficiency. Outcomes were separately analyzed for trauma registry patients by mode of transport. Results: The helicopter EMS computer-aided dispatch data set included 44,073 transports. There was a statewide decrease in helicopter EMS usage for trauma patients of 55.9%, differentially affecting counties closer to trauma centers. The Trauma Registry data set included 182,809 patients (37,407 helicopter transports, 128,129 ambulance transports, and 17,273 transfers). There was an increase of 21% in overall annual EMS scene trauma patients transported; ground transports increased by 33%, whereas helicopter EMS transports decreased by 49%. Helicopter EMS patient acuity increased, with an attendant increase in patient mortality. However, when standardized with W statistics, both helicopter EMS– and ground-transported trauma patients showed sustained improvement in mortality. Conclusion: Modifications to state protocols were associated with decreased helicopter EMS use and overall improved trauma patient outcomes. [Ann Emerg Med. 2016;67:332-340.] Please see page 333 for the Editor’s Capsule Summary of this article. A feedback survey is available with each research article published on the Web at www.annemergmed.com. A podcast for this article is available at www.annemergmed.com. 0196-0644/$-see front matter Copyright © 2015 by the American College of Emergency Physicians. http://dx.doi.org/10.1016/j.annemergmed.2015.07.503
INTRODUCTION Background With more than 3.9 million deaths and 138 million disability-adjusted life-years worldwide, intentional and unintentional injuries remain a public health crisis and the primary cause of death for individuals younger than 45 years in the United States.1 Helicopter emergency medical services (EMS) has become a well-established component of modern trauma systems.2 The rapid growth of helicopter EMS during the past 30 years has been predicated on purported benefits derived from enhanced crew expertise and decreased time to deliver seriously injured patients to definitive trauma care.3-6 332 Annals of Emergency Medicine
However, helicopter EMS is an expensive and limited resource with potential safety concerns.7,8 After 9 fatal helicopter EMS crashes killed 35 people in 2008, the National Transportation Safety Board added helicopter EMS safety to its priority list.9 Helicopter EMS has been shown to cost 5 to 15 times the rate of ground transportation.10,11 Because of safety and cost concerns, the National Transportation Safety Board has recommended to the Federal Interagency Committee on EMS that national helicopter EMS guidelines be developed to reduce unnecessary aeromedical transport of patients.9 Furthermore, there is an ever-increasing movement to develop a “culture of safety” in EMS.12 For both safety Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Editor’s Capsule Summary
What is already known on this topic Helicopter emergency medical services (EMS) is a widely used—but expensive, limited, and potentially dangerous—trauma care resource. What question this study addressed Do statewide triage policies affect helicopter EMS use and trauma outcomes? What this study adds to our knowledge In this analysis of 182,809 Maryland trauma patients transported between 2000 and 2011, statewide trauma triage guidelines reduced helicopter EMS use by 49%. There was a corresponding statewide decrease in adjusted trauma mortality. How this is relevant to clinical practice Trauma triage policies can significantly reduce helicopter EMS use without adversely affecting patient outcomes.
and cost concerns, therefore, there has been increasing pressure nationwide to limit helicopter EMS use to patients who are likely to benefit from air rather than ground transportation to a trauma center. Importance Many EMS systems have attempted to develop helicopter EMS activation criteria and additional requirements to reduce inappropriate use though robust triage tools, but efficient use remains elusive and difficult to measure. Guidelines for appropriate use of helicopter EMS have been developed by Medicare13 and industry stakeholders14-16; however, these guidelines have not evolved quickly and field triage criteria to determine which patients will benefit the most from helicopter EMS require further refinement.15 Concurrent with the increasing safety concerns has been an improved understanding of the importance of trauma centers for the care of injured patients,2,17 as well as the role helicopter EMS plays in improving outcomes for patients with major trauma.2,18,19 Identification of how to use the valuable but limited and potentially dangerous resource of helicopter EMS remains a vitally important area of study. Development and dissemination of field triage guidelines for the appropriate use of helicopter EMS is a relatively nascent field of study. Field trauma triage guidelines were first developed by the American College of Surgeons, evolving during 25 years from a 3-category Volume 67, no. 3 : March 2016
system into a more comprehensive 4-step process designed to help field providers triage and transport patients, whether by air or ground, to a trauma center versus a closer nontrauma center.20,21 In 2009, and then in 2012, the Centers for Disease Control and Prevention (CDC) published guidance on the field triage of injured patients.22 These guidelines, based on national expert panel review, are intended to provide guidance in the triage and destination decisions of EMS field providers. Goals of This Investigation We conducted the present study to determine the effect of statewide field triage changes on helicopter EMS use and patient outcomes. MATERIALS AND METHODS Study Design We used 2 distinct databases for this study. The first (helicopter EMS computer-aided dispatch) component specifically examined helicopter EMS use, and the second (Trauma Registry) component evaluated patient outcomes. There was no common unique identifier linking the databases, although the Trauma Registry database includes mode of transport. The State of Maryland covers 12,407 square miles, stretching from the Atlantic Ocean to the Appalachian Mountains, and is bisected by the Chesapeake Bay. Central Maryland is largely urban; the rest of the state is rural. In the state-funded EMS system in Maryland, helicopter EMS leaders are strongly motivated to enhance safety and mitigate costs while maintaining a system that provides equal opportunity for expeditious, definitive trauma and medical care for every citizen, regardless of geographic or socioeconomic status. The Maryland helicopter EMS program is the oldest civilian medevac operation in the United States, with the first patient transported on March 19, 1970, and more than 140,000 transported since. With statewide distribution of helicopters, this multimission-capable system is operated by the Maryland State Police, with specially trained trooper-flight paramedics and dedicated medical oversight. Maryland initially incorporated trauma triage guidelines based on the American College of Surgeons Field Trauma Triage Guidelines in 1998, with the goal of reducing overuse and overtriage statewide. Just as the science of field triage has evolved since then, so also has the system in Maryland. A series of changes were made in the Maryland statewide protocols for EMS providers from 2004 to 2008 in an effort to address concerns for overuse and overtriage, intended to optimize helicopter EMS use while maintaining excellent patient outcomes. Annals of Emergency Medicine 333
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Hirshon et al
Figure 1. Consort diagrams for patient selection, using the helicopter EMS computer-aided dispatch data (A) and the Trauma Registry Data (B). CAD, Computer-aided dispatch.
Maryland has a statewide regionalized system of emergency and trauma care, coordinated by the Maryland Institute for Emergency Medical Services Systems since 1972. The institute is an independent state agency that is overseen by an 11-member governor-appointed EMS board and a physician executive director.23 Public safety 911 response is provided by 24 jurisdictions, each with its own medical oversight. All jurisdictions report to the state and follow the same statewide EMS protocols.24 Statewide protocols for EMS include a field trauma triage decision tree that is largely consistent with the American College of Surgeons field trauma triage guidelines.22 The Maryland Institute for Emergency Medical Services Systems uses American College of Surgeons criteria to verify and designate 9 adult and 2 pediatric trauma centers. The institute maintains the state trauma registry and EMS data system. A system of 7 helicopter sections, operated by the Maryland State Police Aviation Command, works in concert with several thousand career and volunteer out-of-hospital providers to provide care and expeditiously deliver seriously injured patients to the closest appropriate trauma or specialty care center. The Maryland Institute for Emergency Medical Services Systems maintains the statewide communications system that enables communications between helicopters, field EMS providers, and hospitals. The Maryland State Police Aviation Command dispatches all helicopter EMS scene flights from a single statewide dispatch center (Systems Communications, as known as SYSCOM) at the Maryland Institute for Emergency Medical Services Systems, whereas helicopter EMS interfacility transports are conducted by commercial helicopter EMS services that are licensed by the institute. 334 Annals of Emergency Medicine
We extracted data from the computer-aided dispatch database for the Maryland State Police Medevac program from July 1, 2000, to June 30, 2011. These dates were chosen to include 11 complete fiscal or administrative years (July to June) for the Maryland Institute for Emergency Medical Services Systems, and a period during which a number of significant field triage changes and performance improvements were made to the system. Significant field triage changes instituted during this period were as follows: 1. July 2004: Recommendation in the state protocols that trauma patients within a 30-minute drive to a trauma center meeting category C (mechanism of injury) or D (comorbid factors) in the state trauma decision tree be transported by ground rather than helicopter (Figure E1, available online at http://www.annemergmed.com); these categories correspond to the mechanism of injury and special circumstances criteria in the American College of Surgeons field triage trauma criteria, respectively; helicopter EMS is used for category A and B patients only if quicker and of clinical benefit 2. July 2007: Requirement in state protocol that the 30-minute drive rule be followed 3. October 2008: Requirement for direct medical consultation for physician authorization of aeromedical transport for patients meeting category C or D in the state trauma decision tree, regardless of distance to a trauma center Only helicopter activations that resulted in actual patient transports were included (Figure 1A). Helicopter EMS use trends were analyzed at both the statewide and county level. To Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure 2. Maryland EMS regions with percentage change in number of patients flown weekly by county from July 1, 2000, to June 30, 2011. A 30-minute drive time polygon is drawn around each trauma center and counties are shaded to show which were considered within the 30-minute drive times. TC, Trauma center.
assess the effect of the 30-minute trauma center drive time recommendation and requirement, counties were categorized by whether there was a trauma center within a 30-minute drive. We obtained data from the State of Maryland Trauma Registry for all trauma patients for the study period of July 1, 2000, to June 30, 2011 (Figure 1B). The state trauma registry is a comprehensive injury database that collects data on all trauma patients admitted to Maryland trauma and specialty care centers.23 The fields requested from the registry allowed the tracking of patients once entered into the trauma system, the evaluation of injury severity, and the outcomes of patients over time. Selection of Participants Within the computer-aided dispatch data, all patients flown by the Maryland State Police helicopter EMS program directly from the injury scene to a trauma center were included. Patients were excluded from the analysis if they were flown from an out-of-state scene, between hospitals by helicopter for an interhospital transfer, or for nontraumatic (medical) conditions. For the trauma registry analysis, all patients transported from scene by helicopter or ambulance, or transferred from a nontrauma hospital to a trauma center, were included. Transferred patients were included to assess whether trauma patients were differentially being brought to nontrauma centers according to the system changes. Primary Data Analysis The total number of in-state scene flights from July 1, 2000, to June 30, 2011, was determined with the Volume 67, no. 3 : March 2016
helicopter EMS computer-aided dispatch data, and those flights were restricted as noted above. The number of flights was then compared during the periods when EMS field triage protocols were implemented. The percentage change in weekly flights was calculated per period with linear regression for periods 1, 2, 3, and 5 and negative binomial regression for period 4 because the data were not normally distributed in this period. Spline regression models were created with 4 knots at June 30, 2004; June 30, 2007; June 30, 2008; and June 30, 2009, and plotted to demonstrate the predicted values of number of flights per week. These analyses were evaluated for counties less than and greater than 30 minutes from a trauma center. We obtained data from the Maryland Trauma Registry Data for all trauma patients directly admitted or transferred to a trauma center from July 1, 2000, to June 30, 2011, and restricted as noted previously. Descriptive analyses were used to determine the annual statistics for patient outcomes by mode of transport. Spline regression models were again created with 4 knots at June 30, 2004; June 30, 2007; June 30, 2008; and June 30, 2009, and plotted to demonstrate the weekly predicted values for the number of admissions, the number of patients discharged within 24 hours, the mean Injury Severity Score (ISS), the percentage mortality, and the W statistic, which compares the predicted mortality for patients according to their Trauma Injury Severity Score (TRISS) against their observed mortality, ie, survivorsexpected number of survivors 25,26 . W ¼ actual number ofnumber of patients=100 A positive value indicates better patient outcomes than predicted (ie, fewer deaths) according to their TRISS scores. Annals of Emergency Medicine 335
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure 3. Helicopter EMS trauma patients transported per week in Maryland from July 1, 2000, to June 30, 2011. Overall, Maryland helicopter EMS transports per week are compared with Maryland counties less than and greater than a 30-minute drive from a trauma center. Curves result from spline regressions predicting the number of transports, using Maryland computeraided dispatch data. July 1, 2004: Recommendation in the state protocol that trauma patients within a 30-minute drive to a trauma center and meeting C or D categories be transported by ground rather than helicopter. July 1, 2007: Recommendation becomes a requirement. July 1, 2008: Beginning of fiscal year 2008 and helicopter crash in October 2008. July 1, 2009: Beginning of fiscal year 2009, with the requirement for direct medical consultation for physician authorization of helicopter EMS transport for C or D category trauma patients.
These statistics were evaluated for patients transported by ambulance and patients transported by helicopter. Data analysis was performed with SAS (version 9.2; SAS Institute, Inc., Cary, NC). The computer-aided dispatch analysis was deemed not human subjects research by the institutional review boards at the University of Maryland, Baltimore and Johns Hopkins University. The trauma registry analysis was reviewed and approved by the Maryland Institute for Emergency Medical Services Systems and the institutional review board at the University of Maryland, Baltimore. RESULTS From July 1, 2000, to June 30, 2011, the Maryland State Police helicopter EMS program had a total of 64,025 activations for air medical transport. The final analysis of the computer-aided dispatch data set included 44,073 calls (Figure 1A). Overall, we found a decrease in helicopter EMS usage for trauma patients of 55.9% (95% confidence interval 51.2% to 60.5%) during the 11-year study period in 336 Annals of Emergency Medicine
Hirshon et al
Maryland (Figures 2 and 3; Table E1, available online at http://www.annemergmed.com). At the county level, helicopter use in counties with less than a 30-minute drive time to a trauma center decreased by 78.2% (95% confidence interval 74.3% to 82.1%) compared with a decrease of 12.9% (95% confidence interval 5.1% to 20.7%) in counties with a greater than 30-minute drive time. The recommendation for ground transportation occurred just before a sustained decrease in the number of flights from counties with less than a 30-minute drive time (July 2004). Counties located greater than 30 minutes from a trauma center experienced a further decrease in the number of flights when this recommendation became a requirement (July 2007). A state helicopter crash in September 2008, and the requirement beginning the following month for physician consultation before helicopter transport of trauma category C (mechanism of injury) or D (comorbid conditions or provider discretion) patients, occurred just before an overall significant statewide decrease in helicopter transports. The percentage of change in number of helicopter EMS transports for each period can be found in Table E1 (available online at http://www. annemergmed.com). From July 1, 2000, to June 30, 2011, there were a total of 196,045 patients entered into the State of Maryland Trauma Registry. The final analysis of the Trauma Registry data set included 182,809 patients, of whom 37,407 were transported by helicopter, 128,129 were transported by ambulance, and 17,273 were transferred from nontrauma hospitals (Figure 1B). From July 1, 2001, to June 30, 2011, overall annual EMS volume of trauma patients transported from the scene increased 21%, which was driven by an increase of 33% in ambulance transports in contrast to a decrease of 49% in helicopter transports (Table E2, available online at http://www.annemergmed.com; Figure 4A). Although the number of trauma patients transported by helicopter EMS decreased, patient acuity increased, as indicated by the decreasing percentage of patients discharged within 24 hours (Figure 4B) and the increasing mean ISS for patients flown to the hospital (Figure 4C). As injury severity increased among helicopter EMS trauma patients, not unexpectedly patient mortality increased (Figure 4D). Both helicopter and overall trauma patient weekly W statistics improved, showing decreased patient mortality from that predicted and likely indicating overall system improvement, although helicopter EMS trauma patients’ W statistics increased substantially more than that of ground EMS patients (Figure 5). Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure 4. Maryland Trauma Registry patients transported from the scene or transferred from a nontrauma hospital to a trauma center, July 1, 2000, to June 30, 2011. A, Number of patients transported weekly by mode of transport. B, Weekly percentage of patients discharged within 24 hours by mode of transport. C, Weekly mean ISS by mode of transport. D, Weekly percentage mortality by mode of transport. Curves result from spline regressions predicting weekly outcomes using Maryland Trauma Registry data. July 1, 2004: Recommendation in the state protocol that trauma patients within a 30-minute drive time to a trauma center and meeting C or D categories be transported by ground rather than helicopter. July 1, 2007: Recommendation becomes a requirement. July 1, 2008: Beginning of fiscal year 2008 and helicopter crash in October 2008. July 1, 2009: Beginning of fiscal year 2009, with the requirement for direct medical consultation for physician authorization of helicopter EMS transport for C or D category trauma patients.
LIMITATIONS There are several limitations to this work. Although overall expected mortality improved throughout all periods according to the W statistic, we used parallel analysis to understand the effect of system changes on patient outcomes. In this analysis, we were not able to directly link the 2 data sets because there was no unique identifier allowing a hard linkage. However, because the trauma registry data included mode of transport, this was not an ecologic study in which population metrics of helicopter use were applied to individual subjects. Therefore, the computer-aided dispatch analysis allowed an augmented understanding of the effect of system changes observed within the trauma registry analysis. Additionally, the W statistic has not been validated in penetrating trauma. We therefore calculated it for only patients with blunt trauma. Our trauma population included 82% of patients with blunt injuries and 13% with penetrating injuries. Even though mean ISS of helicopter EMS patients increased over time, other unmeasured or omitted variables may fallaciously lead to the conclusion that Volume 67, no. 3 : March 2016
fewer helicopter EMS flights did not have an effect on expected mortality. Although the assignment mechanism—statewide protocols governing the use of helicopter EMS—was known, estimation of causal effects was not possible because statistical techniques from the field of causal inference could not be applied according to the nature of the available data.27 Two different data sources were used, and individual patient data were not linkable between them. Furthermore, the validity of our analysis, like that of all observational studies, relies on the assumption that all relevant confounders were taken into account. It is possible the residual confounders such as advances in vehicular safety and changes in trauma care account for the decreased mortality over time despite higher injury severity. Moreover, TRISS methodology, which was used to assess mortality, has significant limitations.28 Although it has been the most commonly used technique for calculating the probability of survival for an individual trauma patient, TRISS has not been updated, and it may not be as accurate for prediction Annals of Emergency Medicine 337
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure 5. W statistic for Maryland Trauma Registry patients with blunt injuries transported from the scene or transferred from a nontrauma hospital to a trauma center from July 1, 2000, to June 30, 2011. The W statistic was calculated by mode of transport for all trauma patients with blunt injuries. Curves result from spline regressions predicting the weekly W statistic with Maryland Trauma Registry data. July 1, 2004: Recommendation in the state protocol that trauma patients within a 30-minute drive to a trauma center and meeting C or D categories be transported by ground rather than helicopter. July 1, 2007: Recommendation becomes a requirement. July 1, 2008: Beginning of fiscal year 2008 and helicopter crash in October 2008. July 1, 2009: Beginning of fiscal year 2009, with the requirement for direct medical consultation for physician authorization of helicopter EMS transport for C or D category trauma patients.
of survival now as it was when it was developed in the 1980s.29-31 Despite these limitations, TRISS remains a standard tool for objective evaluation of trauma care, and at least 1 recent study has validated the utility of TRISS for predicting the outcomes of trauma patients requiring intensive care.32 Future outcomes studies comparing helicopter and ground EMS should use individual patient data and state-of-the art study designs and statistical techniques to adjust for additional explanatory variables. Finally, the fact that Maryland is a state-funded publicsafety-based system may make the results of this study less externally generalizable compared with other systems that use commercial helicopter EMS systems or hybrid systems. DISCUSSION To our knowledge, this study represents the largest longitudinal statewide effort aimed at safely reducing helicopter EMS flights ever reported in the literature. From 2001 to 2011, the Maryland EMS system implemented a series of changes in the statewide protocols for EMS providers to address a documented increase in the number of helicopter transports for 338 Annals of Emergency Medicine
Hirshon et al
patients with nonlife-threatening injuries and mechanisms of injury with unclear significance. Throughout this period, the number of helicopter EMS transports for trauma patients was reduced by more than 55%, yet mortality did not appear to increase despite a statistically significant increase in mean ISS. Although recent reports have demonstrated an association with improved survival when helicopter EMS is used for patients with severe injuries,2,18,19,33 there is a paucity of literature on how to best balance the risks and benefits of helicopter EMS to minimize costs and maximize benefits.15 In our study, when implemented properly, statewide protocols had an effect on use patterns of helicopter EMS assets, allowing minimization of overtriage without an attendant increase in population-level detrimental patient outcomes. The Maryland system, by virtue of its integration with a public-safety-based EMS system and regional trauma centers, was highly motivated to decrease the number of helicopter EMS flights but was even more concerned with ensuring optimal patient outcomes. A series of protocol changes were implemented to address a trend of increased use of helicopter EMS for patients with nonlife-threatening injuries and unclear mechanisms of injury. A fatal aircraft mishap in 2008 provided an additional impetus to reduce safety risks without affecting timely access to trauma centers for severely injured patients. Evidence-based triage guidelines, out-of-hospital pointof-care testing, and continual study of trauma epidemiology remain high research priorities to help reduce helicopter EMS overtriage.34 To date, sensitive and specific out-ofhospital trauma triage tools for use in reducing overtriage remain elusive.15,35 The current iteration of field triage used in Maryland (Figure E1, available online at http://www. annemergmed.com), based on modified American College of Surgeons field triage criteria, was implemented judiciously over time while the system was concomitantly monitored for evidence of adverse outcomes. The first effect of the protocol changes likely corresponded to the mandate that helicopter EMS be considered for category C and D patients only if located beyond a 30-minute drive to a trauma center and for all trauma patients if helicopter EMS was deemed to be quicker and of clinical benefit. The second and perhaps more significant effect corresponded to the 2008 crash and the requirement for online consultation for category C and D patients. Yet multiple other changes occurred at the same time, including improved system quality assurance efforts, enhanced out-of-hospital provider education, road traffic changes, and improved safety of motor vehicles. During the late 1990s and early 2000s, Maryland’s increased helicopter use occurred in parallel with the incorporation of the American College of Surgeons’ field trauma triage guidelines into the Maryland EMS Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
protocols.36 At the time, the American College of Surgeons guidelines recommended transportation of patients with certain mechanisms of injury and comorbidities. Subsequently, these guidelines were recognized as contributing to overtriage; yet without these categories, the guidelines would produce significant undertriage, resulting in preventable deaths at hospitals not prepared to provide timely and definitive trauma care. Current guidance from the American College of Surgeons recommends up to a 50% overtriage rate to avoid missing preventable deaths.37 Although within acceptable range in accordance with current American College of Surgeons guidelines, the proportion of patients discharged within 24 hours in this study remains high and signifies the need for ongoing process improvement.38 In this study, modifications to state EMS protocols in Maryland were associated with decreased use of helicopters. Concurrently, there was an improvement in patient outcomes. Protocols that mandated physician consultations for aeromedical transport or required ground transport based on distance from a trauma center were associated with a decreased number of flights. Future research is required to confirm these findings and to determine which elements of helicopter EMS provide the greatest benefit. Supervising editor: Henry E. Wang, MD, MS Author affiliations: From the Department of Emergency Medicine, University of Maryland School of Medicine, Baltimore City, MD (Hirshon, Floccare, Lawner, Nable); the Charles McC Mathias, Jr. National Study Center for Trauma & EMS, University of Maryland School of Medicine, Baltimore City, MD (Hirshon, Comer); the Department of Anesthesiology, University of Maryland School of Medicine, Baltimore City, MD (Galvagno); the Department of Emergency Medicine, The Johns Hopkins University School of Medicine, Baltimore City, MD (Millin, Margolis); and the Maryland Institute for Emergency Medical Service Systems, Baltimore City, MD (Floccare, Alcorta, Bass). Author contributions: JMH, SMG, MGM, DJF, and RRB were responsible for the concept and design of the article and acquisition of the data. AC was responsible for the analysis and interpretation of the data. JMH, SMG, AC, MGM, DJF, and RRB were responsible for drafting the article. RLA, BL, AMM, and JVN were responsible for critical intellectual content around data interpretation. All authors were responsible for article revision and final approval. JMH takes responsibility for the paper as a whole. Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist. Publication dates: Received for publication December 30, 2014. Revisions received May 18, 2015, and July 13, 2015. Accepted for publication July 20, 2015. Available online September 30, 2015. Volume 67, no. 3 : March 2016
Presented as a poster at the Society for Academic Emergency Medicine conference, May 2013, Atlanta, GA.
REFERENCES 1. Chandran A, Hyder AA, Peek-Asa C. The global burden of unintentional injuries and an agenda for progress. Epidemiol Rev. 2010;32: 110-120. 2. Galvagno SM Jr, Thomas S, Stephens C, et al. Helicopter emergency medical services for adults with major trauma. Cochrane Database Syst Rev. 2013;(3):CD009228. 3. Berlot G, La Fata C, Bacer B, et al. Influence of prehospital treatment on the outcome of patients with severe blunt traumatic brain injury: a single-centre study. Eur J Emerg Med. 2009;16:312-317. 4. Brown JB, Stassen NA, Bankey PE, et al. Helicopters and the civilian trauma system: national utilization patterns demonstrate improved outcomes after traumatic injury. J Trauma. 2010;69:1030-1034; discussion 1034-1036. 5. Davis DP, Peay J, Good B, et al. Air medical response to traumatic brain injury: a computer learning algorithm analysis. J Trauma. 2008;64: 889-897. 6. Sullivent EE, Faul M, Wald MM. Reduced mortality in injured adults transported by helicopter emergency medical services. Prehosp Emerg Care. 2011;15:295-302. 7. Baker SP, Grabowski JG, Dodd RS, et al. EMS helicopter crashes: what influences fatal outcome? Ann Emerg Med. 2006;47:351-356. 8. Taylor CB, Stevenson M, Jan S, et al. A systematic review of the costs and benefits of helicopter emergency medical services. Injury. 2010;41:10-20. 9. National Transportation Safety Board. Safety Recommendation. Washington, DC: NTSB; 2009;A-09-87 through -96. 10. Hafner JW, Downs M, Cox K, et al. Inappropriate helicopter emergency medical services transports: results of a national cohort utilization review. Prehosp Emerg Care. 2012;16:434-442. 11. Delgado MK, Staudenmayer KL, Wang NE, et al. Cost-effectiveness of helicopter versus ground emergency medical services for trauma scene transport in the United States. Ann Emerg Med. 2013;62: 351-364. 12. National EMS Advisory Council. Reducing adverse events in EMS: creating a culture of safety. Available at: http://www.nhtsa.gov/ staticfiles/nti/pdf/811705.pdf. Accessed August 16, 2015. 13. Centers for Medicare & Medicaid Services. Medicare benefit policy manual. Chapter 10—ambulance services. Available at: https://www. cms.gov/Regulations-and-Guidance/Guidance/Manuals/downloads/ bp102c10.pdf. Accessed August 16, 2015. 14. Air Medical Physician Association. Medical condition list and appropriate use of air medical transport. Position statement of the Air Medical Physician Association. Prehosp Emerg Care. 2002;6:464-470. 15. Floccare DJ, Stuhlmiller DF, Braithwaite SA, et al. Appropriate and safe utilization of helicopter emergency medical services: a joint position statement with resource document. Prehosp Emerg Care. 2013;17(4):521-525. 16. Thomson DP, Thomas SH; 2002-2003 Air Medical Services Committee of the National Association of EMS Physicians. Guidelines for air medical dispatch. Prehosp Emerg Care. 2003;7:265-271. 17. MacKenzie EJ, Rivara FP, Jurkovich GJ, et al. A national evaluation of the effect of trauma-center care on mortality. N Engl J Med. 2006;354:366-378. 18. Galvagno SM Jr, Haut ER, Zafar SN, et al. Association between helicopter vs ground emergency medical services and survival for adults with major trauma. JAMA. 2012;307:1602-1610. 19. Andruszkow H, Lefering R, Frink M, et al. Survival benefit of helicopter emergency medical services compared to ground emergency medical services in traumatized patients. Crit Care. 2013;17:R124. 20. Kennedy K, Aghababian RV, Gans L, et al. Triage: techniques and applications in decision making. Ann Emerg Med. 1996;28:136-144.
Annals of Emergency Medicine 339
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011 21. Mackersie RC. History of trauma field triage development and the American College of Surgeons criteria. Prehosp Emerg Care. 2006;10:287-294. 22. Sasser SM, Hunt RC, Faul M, et al. Guidelines for field triage of injured patients: recommendations of the national expert panel on field triage, 2011. MMWR Recomm Rep. 2012;61:1-20. 23. Maryland State Emergency Services Board. State of Maryland Emergency Medical Services Plan. Available at: https://www.miemss. org/home/Portals/0/Docs/OtherPDFs/EMS_Plan2006.pdf. Accessed August 16, 2015. 24. Maryland Institute for Emergency Medical Services Systems. Maryland medical protocols for emergency medical services providers. Available at: http://www.miemss.org/home/EMSProviders/EMSProviderProtocols/ tabid/106/Default.aspx. Effective July 1, 2015. Accessed August 16, 2015. 25. Schluter PJ, Nathens A, Neal ML, et al. Trauma and Injury Severity Score (TRISS) coefficients 2009 revision. J Trauma. 2010;68: 761-770. 26. Champion HR, Copes WS, Sacco WJ, et al. The Major Trauma Outcome Study: establishing national norms for trauma care. J Trauma. 1990;30:1356-1365. 27. Robins JM, Hernan MA, Brumback B. Marginal structural models and causal inference in epidemiology. Epidemiology. 2000;11: 550-560. 28. Moore L, Lavoie A, Turgeon AF, et al. The trauma risk adjustment model: a new model for evaluating trauma care. Ann Surg. 2009;249:1040-1046. 29. Champion HR, Sacco WJ, Carnazzo AJ, et al. Trauma score. Crit Care Med. 1981;9:672-676.
Hirshon et al
30. Norris R, Woods R, Harbrecht B, et al. TRISS unexpected survivors: an outdated standard? J Trauma. 2002;52:229-234. 31. Cayten CG, Stahl WM, Murphy JG, et al. Limitations of the TRISS method for interhospital comparisons: a multihospital study. J Trauma. 1991;31:471-481; discussion 481-482. 32. Hwang SY, Lee JH, Lee YH, et al. Comparison of the Sequential Organ Failure Assessment, Acute Physiology and Chronic Health Evaluation II scoring system, and Trauma and Injury Severity Score method for predicting the outcomes of intensive care unit trauma patients. Am J Emerg Med. 2012;30:749-753. 33. Desmettre T, Yeguiayan JM, Coadou H, et al. Impact of emergency medical helicopter transport directly to a university hospital trauma center on mortality of severe blunt trauma patients until discharge. Crit Care. 2012;16:R170. 34. Bledsoe BE, Wesley AK, Eckstein M, et al. Helicopter scene transport of trauma patients with nonlife-threatening injuries: a meta-analysis. J Trauma. 2006;60:1257-1265; discussion 1265-1266. 35. Petrie DA, Tallon JM, Crowell W, et al. Medically appropriate use of helicopter EMS: the mission acceptance/triage process. Air Med J. 2007;26:50-54. 36. National Association of EMS Physicians, American College of Surgeons–Committee on Trauma. Field triage of the injured patient. Prehosp Emerg Care. 2011;15:541. 37. American College of Surgeons–Committee on Trauma. In: Resources for the Optimal Care of the Injured Patient: 2006. Chicago, IL: American College of Surgeons; 2006. 38. Newgard CD, Staudenmayer K, Hsia RY, et al. The cost of overtriage: more than one-third of low-risk injured patients were taken to major trauma centers. Health Aff (Millwood). 2013;32:1591-1599.
Images in Emergency Medicine The Annals Web Site (www.annemergmed.com) contains a collection of hundreds of emergency medicine-related images, complete with brief discussion and diagnosis, in 18 categories. Go to the Images pull-down menu and test your diagnostic skill today. Below is a selection from the Dermatology Images.
“Woman With Painful Swelling in Fingers” by Habboushe and Newman, May 2011, Volume 57, #5, pp. 434, 441. 340 Annals of Emergency Medicine
Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure E1. Maryland Trauma Decision Tree. The Maryland Trauma Decision Tree is similar to CDC’s Guidelines for the Field Triage for Injured Patients. Both schemes incorporate evidence-based anatomic and physiologic criteria into a transport algorithm. Mechanistic criteria and patient-specific characteristics are also factored into decision points about destination.22,24
Volume 67, no. 3 : March 2016
Annals of Emergency Medicine 340.e1
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Hirshon et al
Table E1. Percentage changes in the number of trauma patients transferred by helicopter EMS from fiscal year 2001 to fiscal year 2011: overall percentage change during the entire time and by periods specific to policy changes and helicopter crash. A, Maryland. Maryland, by Fiscal Year Overall 2001 to 2004 2005 to 2007 2008 2009* 2010 to 2011
Percentage Change
95% CI
–55.9 20.5 –12.8 –22.9 –51.4 7.4
–60.5 to –51.27 7.0 to 34.0 –22.7 to –2.9 –40.4 to –5.4 –55.6 to –47.1 –14.0 to 28.8
B, Counties less than a 30-minute drive to a trauma center. Counties 30-Minute Drive to Trauma Center Overall 2001 to 2004 2005 to 2007 2008 2009* 2010 to 2011
Percentage Change
95% CI
–12.9 46.9 5.7 –13.0 –51.6 8.9
–20.7 to –5.1 28.0 to 65.8 –8.3 to 19.6 –32.9 to 6.8 –58.7 to –44.4 –14.1 to 31.9
CI, Confidence interval. *Calculated with negative binomial regression for this period. Linear regression was used to calculate percentage change for the other periods.
340.e2 Annals of Emergency Medicine
Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Table E2. Maryland Trauma Registry patients transported to a trauma center from July 1, 2000, to June 30, 2011.* Fiscal Year System Parameters Overall system Transports, No. Patients’ mean ISS (SD) No. of patients discharged within 24 No. of patients who died (%) Helicopter EMS from scene Transports, No. (%) Patients’ mean ISS (SD) No. of patients discharged within 24 No. of patients who died (%) Ground ambulance from scene Transports, No. (%) Patients’ mean ISS (SD) No. of patients discharged within 24 No. of patients who died (%) Transfers from nontrauma hospitals Transports, No. (%) Patients’ mean ISS (SD) No. of patients discharged within 24 No. of patients who died (%)
h (%)
h (%)
h (%)
h (%)
2001–2004
2005–2007
60,951 8.4 (9.9) 30,747 (50.4) 2,347 (3.9)
50,719 8.5 (9.9) 25,764 (50.8) 1,967 (3.9)
16,232 10.3 7,275 655
(26.6) (10.6) (44.8) (4.0)
12,156 10.8 5,288 459
39,818 7.4 21,945 1,509
(65.3) (9.5) (55.1) (3.8)
4,901 10.5 1,527 183
(8.0) (9.0) (31.2) (3.7)
2008
2009
2010–2011
17,725 8.1 (9.7) 9,377 (52.9) 621 (3.3)
17,933 8.1 (9.8) 9,608 (53.6) 645 (3.4)
35,481 8.3 (9.9) 18,510 (52.2) 1,249 (3.3)
(22.9) (10.8) (43.5) (3.8)
3,450 10.4 1,591 127
(18.4) (10.7) (46.1) (3.7)
2,049 12.2 882 100
(10.7) (12.2) (43.1) (4.9)
3,520 12.9 1,433 158
(9.3) (12.5) (40.7) (4.5)
34,015 7.4 19,065 1,390
(64.0) (9.5) (56.0) (4.1)
12,562 7.1 7,254 434
(67.2) (9.3) (57.8) (3.5)
14,111 7.2 8,166 472
(74.0) (9.3) (58.6) (3.4)
27,623 7.2 15,680 930
(73.2) (9.5) (56.8) (3.4)
4,548 10.9 1,411 118
(9.0) (9.2) (31.0) (2.6)
1,713 10.9 532 56
(9.6) (9.6) (31.1) (3.3)
1,773 10.6 560 70
(9.9) (8.8) (31.6) (4.0)
4,338 10.9 1,397 133
(12.2) (8.7) (32.2) (2.6)
*The periods correspond to the system changes. June 30, 2004: Recommendation in the state protocol that trauma patients within a 30-minute drive to a trauma center and meeting C or D categories be transported by ground rather than helicopter. June 30, 2007: Recommendation becomes a requirement. June 30, 2008: Beginning of fiscal year 2008 and helicopter crash in October 2008. June 30, 2009: Beginning of fiscal year 2009, with the requirement for direct medical consultation for physician authorization of helicopter EMS transport for C or D category trauma patients.
Volume 67, no. 3 : March 2016
Annals of Emergency Medicine 340.e3
Maryland’s Helicopter Emergency Medical Services Experience From 2001 to 2011: System Improvements and Patients’ Outcomes Jon Mark Hirshon, MD, PhD*; Samuel M. Galvagno, Jr, DO, PhD; Angela Comer, MPH; Michael G. Millin, MD, MPH; Douglas J. Floccare, MD, MPH; Richard L. Alcorta, MD; Benjamin J. Lawner, DO; Asa M. Margolis, DO, MPH; Jose V. Nable, MD, NRP; Robert R. Bass, MD *Corresponding Author. E-mail: [email protected], Twitter: @DrJonMark.
Study objective: Helicopter emergency medical services (EMS) has become a well-established component of modern trauma systems. It is an expensive, limited resource with potential safety concerns. Helicopter EMS activation criteria intended to increase efficiency and reduce inappropriate use remain elusive and difficult to measure. This study evaluates the effect of statewide field trauma triage changes on helicopter EMS use and patient outcomes. Methods: Data were extracted from the helicopter EMS computer-aided dispatch database for in-state scene flights and from the state Trauma Registry for all trauma patients directly admitted from the scene or transferred to trauma centers from July 1, 2000, to June 30, 2011. Computer-aided dispatch flights were analyzed for periods corresponding to field triage protocol modifications intended to improve system efficiency. Outcomes were separately analyzed for trauma registry patients by mode of transport. Results: The helicopter EMS computer-aided dispatch data set included 44,073 transports. There was a statewide decrease in helicopter EMS usage for trauma patients of 55.9%, differentially affecting counties closer to trauma centers. The Trauma Registry data set included 182,809 patients (37,407 helicopter transports, 128,129 ambulance transports, and 17,273 transfers). There was an increase of 21% in overall annual EMS scene trauma patients transported; ground transports increased by 33%, whereas helicopter EMS transports decreased by 49%. Helicopter EMS patient acuity increased, with an attendant increase in patient mortality. However, when standardized with W statistics, both helicopter EMS– and ground-transported trauma patients showed sustained improvement in mortality. Conclusion: Modifications to state protocols were associated with decreased helicopter EMS use and overall improved trauma patient outcomes. [Ann Emerg Med. 2016;67:332-340.] Please see page 333 for the Editor’s Capsule Summary of this article. A feedback survey is available with each research article published on the Web at www.annemergmed.com. A podcast for this article is available at www.annemergmed.com. 0196-0644/$-see front matter Copyright © 2015 by the American College of Emergency Physicians. http://dx.doi.org/10.1016/j.annemergmed.2015.07.503
INTRODUCTION Background With more than 3.9 million deaths and 138 million disability-adjusted life-years worldwide, intentional and unintentional injuries remain a public health crisis and the primary cause of death for individuals younger than 45 years in the United States.1 Helicopter emergency medical services (EMS) has become a well-established component of modern trauma systems.2 The rapid growth of helicopter EMS during the past 30 years has been predicated on purported benefits derived from enhanced crew expertise and decreased time to deliver seriously injured patients to definitive trauma care.3-6 332 Annals of Emergency Medicine
However, helicopter EMS is an expensive and limited resource with potential safety concerns.7,8 After 9 fatal helicopter EMS crashes killed 35 people in 2008, the National Transportation Safety Board added helicopter EMS safety to its priority list.9 Helicopter EMS has been shown to cost 5 to 15 times the rate of ground transportation.10,11 Because of safety and cost concerns, the National Transportation Safety Board has recommended to the Federal Interagency Committee on EMS that national helicopter EMS guidelines be developed to reduce unnecessary aeromedical transport of patients.9 Furthermore, there is an ever-increasing movement to develop a “culture of safety” in EMS.12 For both safety Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Editor’s Capsule Summary
What is already known on this topic Helicopter emergency medical services (EMS) is a widely used—but expensive, limited, and potentially dangerous—trauma care resource. What question this study addressed Do statewide triage policies affect helicopter EMS use and trauma outcomes? What this study adds to our knowledge In this analysis of 182,809 Maryland trauma patients transported between 2000 and 2011, statewide trauma triage guidelines reduced helicopter EMS use by 49%. There was a corresponding statewide decrease in adjusted trauma mortality. How this is relevant to clinical practice Trauma triage policies can significantly reduce helicopter EMS use without adversely affecting patient outcomes.
and cost concerns, therefore, there has been increasing pressure nationwide to limit helicopter EMS use to patients who are likely to benefit from air rather than ground transportation to a trauma center. Importance Many EMS systems have attempted to develop helicopter EMS activation criteria and additional requirements to reduce inappropriate use though robust triage tools, but efficient use remains elusive and difficult to measure. Guidelines for appropriate use of helicopter EMS have been developed by Medicare13 and industry stakeholders14-16; however, these guidelines have not evolved quickly and field triage criteria to determine which patients will benefit the most from helicopter EMS require further refinement.15 Concurrent with the increasing safety concerns has been an improved understanding of the importance of trauma centers for the care of injured patients,2,17 as well as the role helicopter EMS plays in improving outcomes for patients with major trauma.2,18,19 Identification of how to use the valuable but limited and potentially dangerous resource of helicopter EMS remains a vitally important area of study. Development and dissemination of field triage guidelines for the appropriate use of helicopter EMS is a relatively nascent field of study. Field trauma triage guidelines were first developed by the American College of Surgeons, evolving during 25 years from a 3-category Volume 67, no. 3 : March 2016
system into a more comprehensive 4-step process designed to help field providers triage and transport patients, whether by air or ground, to a trauma center versus a closer nontrauma center.20,21 In 2009, and then in 2012, the Centers for Disease Control and Prevention (CDC) published guidance on the field triage of injured patients.22 These guidelines, based on national expert panel review, are intended to provide guidance in the triage and destination decisions of EMS field providers. Goals of This Investigation We conducted the present study to determine the effect of statewide field triage changes on helicopter EMS use and patient outcomes. MATERIALS AND METHODS Study Design We used 2 distinct databases for this study. The first (helicopter EMS computer-aided dispatch) component specifically examined helicopter EMS use, and the second (Trauma Registry) component evaluated patient outcomes. There was no common unique identifier linking the databases, although the Trauma Registry database includes mode of transport. The State of Maryland covers 12,407 square miles, stretching from the Atlantic Ocean to the Appalachian Mountains, and is bisected by the Chesapeake Bay. Central Maryland is largely urban; the rest of the state is rural. In the state-funded EMS system in Maryland, helicopter EMS leaders are strongly motivated to enhance safety and mitigate costs while maintaining a system that provides equal opportunity for expeditious, definitive trauma and medical care for every citizen, regardless of geographic or socioeconomic status. The Maryland helicopter EMS program is the oldest civilian medevac operation in the United States, with the first patient transported on March 19, 1970, and more than 140,000 transported since. With statewide distribution of helicopters, this multimission-capable system is operated by the Maryland State Police, with specially trained trooper-flight paramedics and dedicated medical oversight. Maryland initially incorporated trauma triage guidelines based on the American College of Surgeons Field Trauma Triage Guidelines in 1998, with the goal of reducing overuse and overtriage statewide. Just as the science of field triage has evolved since then, so also has the system in Maryland. A series of changes were made in the Maryland statewide protocols for EMS providers from 2004 to 2008 in an effort to address concerns for overuse and overtriage, intended to optimize helicopter EMS use while maintaining excellent patient outcomes. Annals of Emergency Medicine 333
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Hirshon et al
Figure 1. Consort diagrams for patient selection, using the helicopter EMS computer-aided dispatch data (A) and the Trauma Registry Data (B). CAD, Computer-aided dispatch.
Maryland has a statewide regionalized system of emergency and trauma care, coordinated by the Maryland Institute for Emergency Medical Services Systems since 1972. The institute is an independent state agency that is overseen by an 11-member governor-appointed EMS board and a physician executive director.23 Public safety 911 response is provided by 24 jurisdictions, each with its own medical oversight. All jurisdictions report to the state and follow the same statewide EMS protocols.24 Statewide protocols for EMS include a field trauma triage decision tree that is largely consistent with the American College of Surgeons field trauma triage guidelines.22 The Maryland Institute for Emergency Medical Services Systems uses American College of Surgeons criteria to verify and designate 9 adult and 2 pediatric trauma centers. The institute maintains the state trauma registry and EMS data system. A system of 7 helicopter sections, operated by the Maryland State Police Aviation Command, works in concert with several thousand career and volunteer out-of-hospital providers to provide care and expeditiously deliver seriously injured patients to the closest appropriate trauma or specialty care center. The Maryland Institute for Emergency Medical Services Systems maintains the statewide communications system that enables communications between helicopters, field EMS providers, and hospitals. The Maryland State Police Aviation Command dispatches all helicopter EMS scene flights from a single statewide dispatch center (Systems Communications, as known as SYSCOM) at the Maryland Institute for Emergency Medical Services Systems, whereas helicopter EMS interfacility transports are conducted by commercial helicopter EMS services that are licensed by the institute. 334 Annals of Emergency Medicine
We extracted data from the computer-aided dispatch database for the Maryland State Police Medevac program from July 1, 2000, to June 30, 2011. These dates were chosen to include 11 complete fiscal or administrative years (July to June) for the Maryland Institute for Emergency Medical Services Systems, and a period during which a number of significant field triage changes and performance improvements were made to the system. Significant field triage changes instituted during this period were as follows: 1. July 2004: Recommendation in the state protocols that trauma patients within a 30-minute drive to a trauma center meeting category C (mechanism of injury) or D (comorbid factors) in the state trauma decision tree be transported by ground rather than helicopter (Figure E1, available online at http://www.annemergmed.com); these categories correspond to the mechanism of injury and special circumstances criteria in the American College of Surgeons field triage trauma criteria, respectively; helicopter EMS is used for category A and B patients only if quicker and of clinical benefit 2. July 2007: Requirement in state protocol that the 30-minute drive rule be followed 3. October 2008: Requirement for direct medical consultation for physician authorization of aeromedical transport for patients meeting category C or D in the state trauma decision tree, regardless of distance to a trauma center Only helicopter activations that resulted in actual patient transports were included (Figure 1A). Helicopter EMS use trends were analyzed at both the statewide and county level. To Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure 2. Maryland EMS regions with percentage change in number of patients flown weekly by county from July 1, 2000, to June 30, 2011. A 30-minute drive time polygon is drawn around each trauma center and counties are shaded to show which were considered within the 30-minute drive times. TC, Trauma center.
assess the effect of the 30-minute trauma center drive time recommendation and requirement, counties were categorized by whether there was a trauma center within a 30-minute drive. We obtained data from the State of Maryland Trauma Registry for all trauma patients for the study period of July 1, 2000, to June 30, 2011 (Figure 1B). The state trauma registry is a comprehensive injury database that collects data on all trauma patients admitted to Maryland trauma and specialty care centers.23 The fields requested from the registry allowed the tracking of patients once entered into the trauma system, the evaluation of injury severity, and the outcomes of patients over time. Selection of Participants Within the computer-aided dispatch data, all patients flown by the Maryland State Police helicopter EMS program directly from the injury scene to a trauma center were included. Patients were excluded from the analysis if they were flown from an out-of-state scene, between hospitals by helicopter for an interhospital transfer, or for nontraumatic (medical) conditions. For the trauma registry analysis, all patients transported from scene by helicopter or ambulance, or transferred from a nontrauma hospital to a trauma center, were included. Transferred patients were included to assess whether trauma patients were differentially being brought to nontrauma centers according to the system changes. Primary Data Analysis The total number of in-state scene flights from July 1, 2000, to June 30, 2011, was determined with the Volume 67, no. 3 : March 2016
helicopter EMS computer-aided dispatch data, and those flights were restricted as noted above. The number of flights was then compared during the periods when EMS field triage protocols were implemented. The percentage change in weekly flights was calculated per period with linear regression for periods 1, 2, 3, and 5 and negative binomial regression for period 4 because the data were not normally distributed in this period. Spline regression models were created with 4 knots at June 30, 2004; June 30, 2007; June 30, 2008; and June 30, 2009, and plotted to demonstrate the predicted values of number of flights per week. These analyses were evaluated for counties less than and greater than 30 minutes from a trauma center. We obtained data from the Maryland Trauma Registry Data for all trauma patients directly admitted or transferred to a trauma center from July 1, 2000, to June 30, 2011, and restricted as noted previously. Descriptive analyses were used to determine the annual statistics for patient outcomes by mode of transport. Spline regression models were again created with 4 knots at June 30, 2004; June 30, 2007; June 30, 2008; and June 30, 2009, and plotted to demonstrate the weekly predicted values for the number of admissions, the number of patients discharged within 24 hours, the mean Injury Severity Score (ISS), the percentage mortality, and the W statistic, which compares the predicted mortality for patients according to their Trauma Injury Severity Score (TRISS) against their observed mortality, ie, survivorsexpected number of survivors 25,26 . W ¼ actual number ofnumber of patients=100 A positive value indicates better patient outcomes than predicted (ie, fewer deaths) according to their TRISS scores. Annals of Emergency Medicine 335
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure 3. Helicopter EMS trauma patients transported per week in Maryland from July 1, 2000, to June 30, 2011. Overall, Maryland helicopter EMS transports per week are compared with Maryland counties less than and greater than a 30-minute drive from a trauma center. Curves result from spline regressions predicting the number of transports, using Maryland computeraided dispatch data. July 1, 2004: Recommendation in the state protocol that trauma patients within a 30-minute drive to a trauma center and meeting C or D categories be transported by ground rather than helicopter. July 1, 2007: Recommendation becomes a requirement. July 1, 2008: Beginning of fiscal year 2008 and helicopter crash in October 2008. July 1, 2009: Beginning of fiscal year 2009, with the requirement for direct medical consultation for physician authorization of helicopter EMS transport for C or D category trauma patients.
These statistics were evaluated for patients transported by ambulance and patients transported by helicopter. Data analysis was performed with SAS (version 9.2; SAS Institute, Inc., Cary, NC). The computer-aided dispatch analysis was deemed not human subjects research by the institutional review boards at the University of Maryland, Baltimore and Johns Hopkins University. The trauma registry analysis was reviewed and approved by the Maryland Institute for Emergency Medical Services Systems and the institutional review board at the University of Maryland, Baltimore. RESULTS From July 1, 2000, to June 30, 2011, the Maryland State Police helicopter EMS program had a total of 64,025 activations for air medical transport. The final analysis of the computer-aided dispatch data set included 44,073 calls (Figure 1A). Overall, we found a decrease in helicopter EMS usage for trauma patients of 55.9% (95% confidence interval 51.2% to 60.5%) during the 11-year study period in 336 Annals of Emergency Medicine
Hirshon et al
Maryland (Figures 2 and 3; Table E1, available online at http://www.annemergmed.com). At the county level, helicopter use in counties with less than a 30-minute drive time to a trauma center decreased by 78.2% (95% confidence interval 74.3% to 82.1%) compared with a decrease of 12.9% (95% confidence interval 5.1% to 20.7%) in counties with a greater than 30-minute drive time. The recommendation for ground transportation occurred just before a sustained decrease in the number of flights from counties with less than a 30-minute drive time (July 2004). Counties located greater than 30 minutes from a trauma center experienced a further decrease in the number of flights when this recommendation became a requirement (July 2007). A state helicopter crash in September 2008, and the requirement beginning the following month for physician consultation before helicopter transport of trauma category C (mechanism of injury) or D (comorbid conditions or provider discretion) patients, occurred just before an overall significant statewide decrease in helicopter transports. The percentage of change in number of helicopter EMS transports for each period can be found in Table E1 (available online at http://www. annemergmed.com). From July 1, 2000, to June 30, 2011, there were a total of 196,045 patients entered into the State of Maryland Trauma Registry. The final analysis of the Trauma Registry data set included 182,809 patients, of whom 37,407 were transported by helicopter, 128,129 were transported by ambulance, and 17,273 were transferred from nontrauma hospitals (Figure 1B). From July 1, 2001, to June 30, 2011, overall annual EMS volume of trauma patients transported from the scene increased 21%, which was driven by an increase of 33% in ambulance transports in contrast to a decrease of 49% in helicopter transports (Table E2, available online at http://www.annemergmed.com; Figure 4A). Although the number of trauma patients transported by helicopter EMS decreased, patient acuity increased, as indicated by the decreasing percentage of patients discharged within 24 hours (Figure 4B) and the increasing mean ISS for patients flown to the hospital (Figure 4C). As injury severity increased among helicopter EMS trauma patients, not unexpectedly patient mortality increased (Figure 4D). Both helicopter and overall trauma patient weekly W statistics improved, showing decreased patient mortality from that predicted and likely indicating overall system improvement, although helicopter EMS trauma patients’ W statistics increased substantially more than that of ground EMS patients (Figure 5). Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure 4. Maryland Trauma Registry patients transported from the scene or transferred from a nontrauma hospital to a trauma center, July 1, 2000, to June 30, 2011. A, Number of patients transported weekly by mode of transport. B, Weekly percentage of patients discharged within 24 hours by mode of transport. C, Weekly mean ISS by mode of transport. D, Weekly percentage mortality by mode of transport. Curves result from spline regressions predicting weekly outcomes using Maryland Trauma Registry data. July 1, 2004: Recommendation in the state protocol that trauma patients within a 30-minute drive time to a trauma center and meeting C or D categories be transported by ground rather than helicopter. July 1, 2007: Recommendation becomes a requirement. July 1, 2008: Beginning of fiscal year 2008 and helicopter crash in October 2008. July 1, 2009: Beginning of fiscal year 2009, with the requirement for direct medical consultation for physician authorization of helicopter EMS transport for C or D category trauma patients.
LIMITATIONS There are several limitations to this work. Although overall expected mortality improved throughout all periods according to the W statistic, we used parallel analysis to understand the effect of system changes on patient outcomes. In this analysis, we were not able to directly link the 2 data sets because there was no unique identifier allowing a hard linkage. However, because the trauma registry data included mode of transport, this was not an ecologic study in which population metrics of helicopter use were applied to individual subjects. Therefore, the computer-aided dispatch analysis allowed an augmented understanding of the effect of system changes observed within the trauma registry analysis. Additionally, the W statistic has not been validated in penetrating trauma. We therefore calculated it for only patients with blunt trauma. Our trauma population included 82% of patients with blunt injuries and 13% with penetrating injuries. Even though mean ISS of helicopter EMS patients increased over time, other unmeasured or omitted variables may fallaciously lead to the conclusion that Volume 67, no. 3 : March 2016
fewer helicopter EMS flights did not have an effect on expected mortality. Although the assignment mechanism—statewide protocols governing the use of helicopter EMS—was known, estimation of causal effects was not possible because statistical techniques from the field of causal inference could not be applied according to the nature of the available data.27 Two different data sources were used, and individual patient data were not linkable between them. Furthermore, the validity of our analysis, like that of all observational studies, relies on the assumption that all relevant confounders were taken into account. It is possible the residual confounders such as advances in vehicular safety and changes in trauma care account for the decreased mortality over time despite higher injury severity. Moreover, TRISS methodology, which was used to assess mortality, has significant limitations.28 Although it has been the most commonly used technique for calculating the probability of survival for an individual trauma patient, TRISS has not been updated, and it may not be as accurate for prediction Annals of Emergency Medicine 337
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure 5. W statistic for Maryland Trauma Registry patients with blunt injuries transported from the scene or transferred from a nontrauma hospital to a trauma center from July 1, 2000, to June 30, 2011. The W statistic was calculated by mode of transport for all trauma patients with blunt injuries. Curves result from spline regressions predicting the weekly W statistic with Maryland Trauma Registry data. July 1, 2004: Recommendation in the state protocol that trauma patients within a 30-minute drive to a trauma center and meeting C or D categories be transported by ground rather than helicopter. July 1, 2007: Recommendation becomes a requirement. July 1, 2008: Beginning of fiscal year 2008 and helicopter crash in October 2008. July 1, 2009: Beginning of fiscal year 2009, with the requirement for direct medical consultation for physician authorization of helicopter EMS transport for C or D category trauma patients.
of survival now as it was when it was developed in the 1980s.29-31 Despite these limitations, TRISS remains a standard tool for objective evaluation of trauma care, and at least 1 recent study has validated the utility of TRISS for predicting the outcomes of trauma patients requiring intensive care.32 Future outcomes studies comparing helicopter and ground EMS should use individual patient data and state-of-the art study designs and statistical techniques to adjust for additional explanatory variables. Finally, the fact that Maryland is a state-funded publicsafety-based system may make the results of this study less externally generalizable compared with other systems that use commercial helicopter EMS systems or hybrid systems. DISCUSSION To our knowledge, this study represents the largest longitudinal statewide effort aimed at safely reducing helicopter EMS flights ever reported in the literature. From 2001 to 2011, the Maryland EMS system implemented a series of changes in the statewide protocols for EMS providers to address a documented increase in the number of helicopter transports for 338 Annals of Emergency Medicine
Hirshon et al
patients with nonlife-threatening injuries and mechanisms of injury with unclear significance. Throughout this period, the number of helicopter EMS transports for trauma patients was reduced by more than 55%, yet mortality did not appear to increase despite a statistically significant increase in mean ISS. Although recent reports have demonstrated an association with improved survival when helicopter EMS is used for patients with severe injuries,2,18,19,33 there is a paucity of literature on how to best balance the risks and benefits of helicopter EMS to minimize costs and maximize benefits.15 In our study, when implemented properly, statewide protocols had an effect on use patterns of helicopter EMS assets, allowing minimization of overtriage without an attendant increase in population-level detrimental patient outcomes. The Maryland system, by virtue of its integration with a public-safety-based EMS system and regional trauma centers, was highly motivated to decrease the number of helicopter EMS flights but was even more concerned with ensuring optimal patient outcomes. A series of protocol changes were implemented to address a trend of increased use of helicopter EMS for patients with nonlife-threatening injuries and unclear mechanisms of injury. A fatal aircraft mishap in 2008 provided an additional impetus to reduce safety risks without affecting timely access to trauma centers for severely injured patients. Evidence-based triage guidelines, out-of-hospital pointof-care testing, and continual study of trauma epidemiology remain high research priorities to help reduce helicopter EMS overtriage.34 To date, sensitive and specific out-ofhospital trauma triage tools for use in reducing overtriage remain elusive.15,35 The current iteration of field triage used in Maryland (Figure E1, available online at http://www. annemergmed.com), based on modified American College of Surgeons field triage criteria, was implemented judiciously over time while the system was concomitantly monitored for evidence of adverse outcomes. The first effect of the protocol changes likely corresponded to the mandate that helicopter EMS be considered for category C and D patients only if located beyond a 30-minute drive to a trauma center and for all trauma patients if helicopter EMS was deemed to be quicker and of clinical benefit. The second and perhaps more significant effect corresponded to the 2008 crash and the requirement for online consultation for category C and D patients. Yet multiple other changes occurred at the same time, including improved system quality assurance efforts, enhanced out-of-hospital provider education, road traffic changes, and improved safety of motor vehicles. During the late 1990s and early 2000s, Maryland’s increased helicopter use occurred in parallel with the incorporation of the American College of Surgeons’ field trauma triage guidelines into the Maryland EMS Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
protocols.36 At the time, the American College of Surgeons guidelines recommended transportation of patients with certain mechanisms of injury and comorbidities. Subsequently, these guidelines were recognized as contributing to overtriage; yet without these categories, the guidelines would produce significant undertriage, resulting in preventable deaths at hospitals not prepared to provide timely and definitive trauma care. Current guidance from the American College of Surgeons recommends up to a 50% overtriage rate to avoid missing preventable deaths.37 Although within acceptable range in accordance with current American College of Surgeons guidelines, the proportion of patients discharged within 24 hours in this study remains high and signifies the need for ongoing process improvement.38 In this study, modifications to state EMS protocols in Maryland were associated with decreased use of helicopters. Concurrently, there was an improvement in patient outcomes. Protocols that mandated physician consultations for aeromedical transport or required ground transport based on distance from a trauma center were associated with a decreased number of flights. Future research is required to confirm these findings and to determine which elements of helicopter EMS provide the greatest benefit. Supervising editor: Henry E. Wang, MD, MS Author affiliations: From the Department of Emergency Medicine, University of Maryland School of Medicine, Baltimore City, MD (Hirshon, Floccare, Lawner, Nable); the Charles McC Mathias, Jr. National Study Center for Trauma & EMS, University of Maryland School of Medicine, Baltimore City, MD (Hirshon, Comer); the Department of Anesthesiology, University of Maryland School of Medicine, Baltimore City, MD (Galvagno); the Department of Emergency Medicine, The Johns Hopkins University School of Medicine, Baltimore City, MD (Millin, Margolis); and the Maryland Institute for Emergency Medical Service Systems, Baltimore City, MD (Floccare, Alcorta, Bass). Author contributions: JMH, SMG, MGM, DJF, and RRB were responsible for the concept and design of the article and acquisition of the data. AC was responsible for the analysis and interpretation of the data. JMH, SMG, AC, MGM, DJF, and RRB were responsible for drafting the article. RLA, BL, AMM, and JVN were responsible for critical intellectual content around data interpretation. All authors were responsible for article revision and final approval. JMH takes responsibility for the paper as a whole. Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist. Publication dates: Received for publication December 30, 2014. Revisions received May 18, 2015, and July 13, 2015. Accepted for publication July 20, 2015. Available online September 30, 2015. Volume 67, no. 3 : March 2016
Presented as a poster at the Society for Academic Emergency Medicine conference, May 2013, Atlanta, GA.
REFERENCES 1. Chandran A, Hyder AA, Peek-Asa C. The global burden of unintentional injuries and an agenda for progress. Epidemiol Rev. 2010;32: 110-120. 2. Galvagno SM Jr, Thomas S, Stephens C, et al. Helicopter emergency medical services for adults with major trauma. Cochrane Database Syst Rev. 2013;(3):CD009228. 3. Berlot G, La Fata C, Bacer B, et al. Influence of prehospital treatment on the outcome of patients with severe blunt traumatic brain injury: a single-centre study. Eur J Emerg Med. 2009;16:312-317. 4. Brown JB, Stassen NA, Bankey PE, et al. Helicopters and the civilian trauma system: national utilization patterns demonstrate improved outcomes after traumatic injury. J Trauma. 2010;69:1030-1034; discussion 1034-1036. 5. Davis DP, Peay J, Good B, et al. Air medical response to traumatic brain injury: a computer learning algorithm analysis. J Trauma. 2008;64: 889-897. 6. Sullivent EE, Faul M, Wald MM. Reduced mortality in injured adults transported by helicopter emergency medical services. Prehosp Emerg Care. 2011;15:295-302. 7. Baker SP, Grabowski JG, Dodd RS, et al. EMS helicopter crashes: what influences fatal outcome? Ann Emerg Med. 2006;47:351-356. 8. Taylor CB, Stevenson M, Jan S, et al. A systematic review of the costs and benefits of helicopter emergency medical services. Injury. 2010;41:10-20. 9. National Transportation Safety Board. Safety Recommendation. Washington, DC: NTSB; 2009;A-09-87 through -96. 10. Hafner JW, Downs M, Cox K, et al. Inappropriate helicopter emergency medical services transports: results of a national cohort utilization review. Prehosp Emerg Care. 2012;16:434-442. 11. Delgado MK, Staudenmayer KL, Wang NE, et al. Cost-effectiveness of helicopter versus ground emergency medical services for trauma scene transport in the United States. Ann Emerg Med. 2013;62: 351-364. 12. National EMS Advisory Council. Reducing adverse events in EMS: creating a culture of safety. Available at: http://www.nhtsa.gov/ staticfiles/nti/pdf/811705.pdf. Accessed August 16, 2015. 13. Centers for Medicare & Medicaid Services. Medicare benefit policy manual. Chapter 10—ambulance services. Available at: https://www. cms.gov/Regulations-and-Guidance/Guidance/Manuals/downloads/ bp102c10.pdf. Accessed August 16, 2015. 14. Air Medical Physician Association. Medical condition list and appropriate use of air medical transport. Position statement of the Air Medical Physician Association. Prehosp Emerg Care. 2002;6:464-470. 15. Floccare DJ, Stuhlmiller DF, Braithwaite SA, et al. Appropriate and safe utilization of helicopter emergency medical services: a joint position statement with resource document. Prehosp Emerg Care. 2013;17(4):521-525. 16. Thomson DP, Thomas SH; 2002-2003 Air Medical Services Committee of the National Association of EMS Physicians. Guidelines for air medical dispatch. Prehosp Emerg Care. 2003;7:265-271. 17. MacKenzie EJ, Rivara FP, Jurkovich GJ, et al. A national evaluation of the effect of trauma-center care on mortality. N Engl J Med. 2006;354:366-378. 18. Galvagno SM Jr, Haut ER, Zafar SN, et al. Association between helicopter vs ground emergency medical services and survival for adults with major trauma. JAMA. 2012;307:1602-1610. 19. Andruszkow H, Lefering R, Frink M, et al. Survival benefit of helicopter emergency medical services compared to ground emergency medical services in traumatized patients. Crit Care. 2013;17:R124. 20. Kennedy K, Aghababian RV, Gans L, et al. Triage: techniques and applications in decision making. Ann Emerg Med. 1996;28:136-144.
Annals of Emergency Medicine 339
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011 21. Mackersie RC. History of trauma field triage development and the American College of Surgeons criteria. Prehosp Emerg Care. 2006;10:287-294. 22. Sasser SM, Hunt RC, Faul M, et al. Guidelines for field triage of injured patients: recommendations of the national expert panel on field triage, 2011. MMWR Recomm Rep. 2012;61:1-20. 23. Maryland State Emergency Services Board. State of Maryland Emergency Medical Services Plan. Available at: https://www.miemss. org/home/Portals/0/Docs/OtherPDFs/EMS_Plan2006.pdf. Accessed August 16, 2015. 24. Maryland Institute for Emergency Medical Services Systems. Maryland medical protocols for emergency medical services providers. Available at: http://www.miemss.org/home/EMSProviders/EMSProviderProtocols/ tabid/106/Default.aspx. Effective July 1, 2015. Accessed August 16, 2015. 25. Schluter PJ, Nathens A, Neal ML, et al. Trauma and Injury Severity Score (TRISS) coefficients 2009 revision. J Trauma. 2010;68: 761-770. 26. Champion HR, Copes WS, Sacco WJ, et al. The Major Trauma Outcome Study: establishing national norms for trauma care. J Trauma. 1990;30:1356-1365. 27. Robins JM, Hernan MA, Brumback B. Marginal structural models and causal inference in epidemiology. Epidemiology. 2000;11: 550-560. 28. Moore L, Lavoie A, Turgeon AF, et al. The trauma risk adjustment model: a new model for evaluating trauma care. Ann Surg. 2009;249:1040-1046. 29. Champion HR, Sacco WJ, Carnazzo AJ, et al. Trauma score. Crit Care Med. 1981;9:672-676.
Hirshon et al
30. Norris R, Woods R, Harbrecht B, et al. TRISS unexpected survivors: an outdated standard? J Trauma. 2002;52:229-234. 31. Cayten CG, Stahl WM, Murphy JG, et al. Limitations of the TRISS method for interhospital comparisons: a multihospital study. J Trauma. 1991;31:471-481; discussion 481-482. 32. Hwang SY, Lee JH, Lee YH, et al. Comparison of the Sequential Organ Failure Assessment, Acute Physiology and Chronic Health Evaluation II scoring system, and Trauma and Injury Severity Score method for predicting the outcomes of intensive care unit trauma patients. Am J Emerg Med. 2012;30:749-753. 33. Desmettre T, Yeguiayan JM, Coadou H, et al. Impact of emergency medical helicopter transport directly to a university hospital trauma center on mortality of severe blunt trauma patients until discharge. Crit Care. 2012;16:R170. 34. Bledsoe BE, Wesley AK, Eckstein M, et al. Helicopter scene transport of trauma patients with nonlife-threatening injuries: a meta-analysis. J Trauma. 2006;60:1257-1265; discussion 1265-1266. 35. Petrie DA, Tallon JM, Crowell W, et al. Medically appropriate use of helicopter EMS: the mission acceptance/triage process. Air Med J. 2007;26:50-54. 36. National Association of EMS Physicians, American College of Surgeons–Committee on Trauma. Field triage of the injured patient. Prehosp Emerg Care. 2011;15:541. 37. American College of Surgeons–Committee on Trauma. In: Resources for the Optimal Care of the Injured Patient: 2006. Chicago, IL: American College of Surgeons; 2006. 38. Newgard CD, Staudenmayer K, Hsia RY, et al. The cost of overtriage: more than one-third of low-risk injured patients were taken to major trauma centers. Health Aff (Millwood). 2013;32:1591-1599.
Images in Emergency Medicine The Annals Web Site (www.annemergmed.com) contains a collection of hundreds of emergency medicine-related images, complete with brief discussion and diagnosis, in 18 categories. Go to the Images pull-down menu and test your diagnostic skill today. Below is a selection from the Dermatology Images.
“Woman With Painful Swelling in Fingers” by Habboushe and Newman, May 2011, Volume 57, #5, pp. 434, 441. 340 Annals of Emergency Medicine
Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Figure E1. Maryland Trauma Decision Tree. The Maryland Trauma Decision Tree is similar to CDC’s Guidelines for the Field Triage for Injured Patients. Both schemes incorporate evidence-based anatomic and physiologic criteria into a transport algorithm. Mechanistic criteria and patient-specific characteristics are also factored into decision points about destination.22,24
Volume 67, no. 3 : March 2016
Annals of Emergency Medicine 340.e1
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Hirshon et al
Table E1. Percentage changes in the number of trauma patients transferred by helicopter EMS from fiscal year 2001 to fiscal year 2011: overall percentage change during the entire time and by periods specific to policy changes and helicopter crash. A, Maryland. Maryland, by Fiscal Year Overall 2001 to 2004 2005 to 2007 2008 2009* 2010 to 2011
Percentage Change
95% CI
–55.9 20.5 –12.8 –22.9 –51.4 7.4
–60.5 to –51.27 7.0 to 34.0 –22.7 to –2.9 –40.4 to –5.4 –55.6 to –47.1 –14.0 to 28.8
B, Counties less than a 30-minute drive to a trauma center. Counties 30-Minute Drive to Trauma Center Overall 2001 to 2004 2005 to 2007 2008 2009* 2010 to 2011
Percentage Change
95% CI
–12.9 46.9 5.7 –13.0 –51.6 8.9
–20.7 to –5.1 28.0 to 65.8 –8.3 to 19.6 –32.9 to 6.8 –58.7 to –44.4 –14.1 to 31.9
CI, Confidence interval. *Calculated with negative binomial regression for this period. Linear regression was used to calculate percentage change for the other periods.
340.e2 Annals of Emergency Medicine
Volume 67, no. 3 : March 2016
Hirshon et al
Maryland’s Helicopter Emergency Medical Services Experience, 2001-2011
Table E2. Maryland Trauma Registry patients transported to a trauma center from July 1, 2000, to June 30, 2011.* Fiscal Year System Parameters Overall system Transports, No. Patients’ mean ISS (SD) No. of patients discharged within 24 No. of patients who died (%) Helicopter EMS from scene Transports, No. (%) Patients’ mean ISS (SD) No. of patients discharged within 24 No. of patients who died (%) Ground ambulance from scene Transports, No. (%) Patients’ mean ISS (SD) No. of patients discharged within 24 No. of patients who died (%) Transfers from nontrauma hospitals Transports, No. (%) Patients’ mean ISS (SD) No. of patients discharged within 24 No. of patients who died (%)
h (%)
h (%)
h (%)
h (%)
2001–2004
2005–2007
60,951 8.4 (9.9) 30,747 (50.4) 2,347 (3.9)
50,719 8.5 (9.9) 25,764 (50.8) 1,967 (3.9)
16,232 10.3 7,275 655
(26.6) (10.6) (44.8) (4.0)
12,156 10.8 5,288 459
39,818 7.4 21,945 1,509
(65.3) (9.5) (55.1) (3.8)
4,901 10.5 1,527 183
(8.0) (9.0) (31.2) (3.7)
2008
2009
2010–2011
17,725 8.1 (9.7) 9,377 (52.9) 621 (3.3)
17,933 8.1 (9.8) 9,608 (53.6) 645 (3.4)
35,481 8.3 (9.9) 18,510 (52.2) 1,249 (3.3)
(22.9) (10.8) (43.5) (3.8)
3,450 10.4 1,591 127
(18.4) (10.7) (46.1) (3.7)
2,049 12.2 882 100
(10.7) (12.2) (43.1) (4.9)
3,520 12.9 1,433 158
(9.3) (12.5) (40.7) (4.5)
34,015 7.4 19,065 1,390
(64.0) (9.5) (56.0) (4.1)
12,562 7.1 7,254 434
(67.2) (9.3) (57.8) (3.5)
14,111 7.2 8,166 472
(74.0) (9.3) (58.6) (3.4)
27,623 7.2 15,680 930
(73.2) (9.5) (56.8) (3.4)
4,548 10.9 1,411 118
(9.0) (9.2) (31.0) (2.6)
1,713 10.9 532 56
(9.6) (9.6) (31.1) (3.3)
1,773 10.6 560 70
(9.9) (8.8) (31.6) (4.0)
4,338 10.9 1,397 133
(12.2) (8.7) (32.2) (2.6)
*The periods correspond to the system changes. June 30, 2004: Recommendation in the state protocol that trauma patients within a 30-minute drive to a trauma center and meeting C or D categories be transported by ground rather than helicopter. June 30, 2007: Recommendation becomes a requirement. June 30, 2008: Beginning of fiscal year 2008 and helicopter crash in October 2008. June 30, 2009: Beginning of fiscal year 2009, with the requirement for direct medical consultation for physician authorization of helicopter EMS transport for C or D category trauma patients.
Volume 67, no. 3 : March 2016
Annals of Emergency Medicine 340.e3
