April 2011 Archives

Haddon's Matrix factors for EMSP Crashes and Fatalities

Quick look at the Nation's numbers

  • In the United States, between 1999 and 2007, unintentional injuries rank 5th among the leading causes of death (CDC, WISQARS).
  • Motor vehicle traffic (39%) is the leading cause of death for unintentional injury deaths, followed by poisonings (18%) (CDC, WISQARS).
  • From 2000-2009, 371,104 fatal crashes occurred on US roadways, totaling 444,362 fatalities (NHTSA, FARS Encyclopedia).
  • According to the Bureau of Labor Statistics Census for Fatal Occupational Injuries (CFOI), 42% of all occupationally-related deaths were due to highway traffic.
  • The estimated fatality rate for emergency medical services providers is 12.7 / 100,000 workers, which is more than twice the nation's average [Maguire et al., 2002].

Future Research

Motor vehicle crash-related injuries and fatalities will always occur on the roadway due to human error. To address the issue of EV crashes that result in morbidity and mortality, research should focus on the known areas of risk. To do this, efforts made should follow the public health model (Figure 5).

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Figure 5: The Public Health Model, Center for Disease Control and Prevention, Injury Prevention and Control


As stated previously, 85% of all EV injury crashes occur at intersections. Forty-six and 50% of all EV fatal crashes and fatalities occur at intersections. To reduce the risk of intersection collisions with EVs, emergency vehicle preemption systems (EVP) are being adapted throughout the world to provide warning to drivers on the roadway that an EV is approaching. The use of lights and sirens provide an initial warning to drivers that an EV is approaching. This warning, coupled with an EVP system will provide the driver on the roadway with a two-stage gradient level of warning.

Emergency vehicle preemptions systems have shown to be a benefit towards the reduction of EV crashes and increase in response time. EVP systems in the City of Plano, Texas have reduced the number of EV intersection-related crashes from an average of 2.3 per year to less than one intersection crash every five years. Between 1967 through 1976, EVP systems were integrated in the City of Saint Paul, Minnesota. During this time period, a decrease in the number of EV crashes occurred from a high (1967) of eight crashes per year to an average of 3.3 per year for the latter part of the study time period [19].

In addition to intersection technology to reduce collisions, other areas can be researched that can mitigate EMSP risk for vehicle-related injury or fatality. Figure 6 identifies such areas.

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Figure 6: Factors contributing to emergency medical services (EMS) vehicular-related injuries and fatalities. Figure adapted from Slattery & Silver, 2009; Figure 1.

References

1. Maguire, B.J., Hunting, K.L., Smith, G.S., Levick, N.R., Occupational Fatalities in Emergency Medical Services: A Hidden Crisis. Annals of Emergency Medicine, 2002. 40(6): p. 625-32.

2. Clarke, C., Zak, M.J., Fatalities to Law Enforcement Officers and Firefighters, 1992-97, in Compensation and Working Conditions, Bureau of Labor Statistics, Editor. 1999.

3. Studnek, J.R., Ferketich, A., Crawford, J.M., On the job illness and injury resulting in lost work time among a national cohort of emergency medical services professionals. American Journal of Industrial Medicine, 2007. 50: p. 921-31.

4. Custalow, C.B., Gravitz, C.S., Emergency Medical Vehicle Collisions and Potential for Preventive Intervention. Prehospital Emergency Care, 2004. 8(2): p. 175-84.

5. Kahn, C.A., Pirrallo, R.G., Kuhn, E.M., Characteristics of Fatal Ambulance Crashes in the United States: An 11-year Retrospective Analysis. Prehospital Emergency Care, 2001. 5(3): p. 261-9.

6. Lenne, M.G., Triggs, T.J., Mulvihill, C.M., Regan, M.A., Detection of Emergency Vehicles: Driver Responses to Advance Warning in a Driving Simulator. Human Factors, 2008. 50(1): p. 135-44.

7. National Highway Traffic Safety Administration, Fatality Analysis Reporting System Encyclopedia. 2010.

8. Slattery, D.E., Silver, A., The Hazards of Providing Care in Emergency Vehicles: An opportunity for Reform. Prehospital Emergency Care, 2009. 13(3): p. 388-97.

9. Sanddal, N.D., Albert, S., Hansen, J.D., Kupas, D.F., Contributing Factors and Issues Associated with Rural Ambulance Crashes: Literature Review and Annotated Bibliography. Prehospital Emergency Care, 2008. 12(2): p. 257-67.

10. Brown, L.H., Whitney, C.L., Hunt, R.C., Addario, M., Hogue, T., Do warning lights and sirens reduce ambulance response times? Prehospital Emergency Care, 2000. 4(1): p. 70-4.

11. Hunt, R.C., Brown, L.H., Cabinum, E.S., Whitley, T.W., Prasad, N.H., Owens, C.F., Is ambulance transport time with lights and sirens faster than that without? Annals of Emergency Medicine, 1995. 25(4): p. 507-11.

12. Kupas, D.F., Dula, D.J., Pino, B.J., Patient outcome using medical protocol to limit "lights and sirens" transport. Prehospital Disaster Med, 1994. 9(4): p. 226-9.

13. O'Brien, D.J., Price, T.G., Adams, P., The effectiveness of lights and siren use during ambulance transport by paramedics. Prehospital Emergency Care, 1999. 3(2): p. 127-30.

14. Gormley, M., Walsh, T., Fuller, R., Risks in the driving of emergency service vehicle. The Irish Journal of Psychology, 2008. 29(1-2): p. 7-18.

15. Ostensen, G., Improving intersection safety - what's next? ITE, 2003. 73(1): p. 37-9.

16. Becker, L.R., Zaloshnja, E., Levick, N., Li, G., Miller, T.R., Relative risk of injury and death in ambulance and other emergency vehicles. Accident Analysis and Prevention, 2003. 35: p. 941-8.

17. Sanddal, T.L., Sanddal, N.D., Ward, N., Stanley, L., Ambulance Crash Characteristics in the US Defines by the Popular Press: A Retrospective Analysis. Emergency Medicine International, 2010.

18. Blincoe, L., Seay, A., Zaloshnja, E., Miller, T., Romano, E., Luchter, S., Spicer, R., The Economic Impact of Motor Vehicle Crashes, 2000, National Highway Traffic Safety Administration, Report Number DOT HS 809 446, Editor. 2002: Washington D.C.

19. Intelligent Transportation Systems, Traffic Signal Preemption for Emergency Vehicles: A Cross-Cutting Study, U.S. DOT Federal Highway Administration, Report Number FHWA-JPO-05-010,, Editor. 2006: Washington, DC.

Blog is part of a Graduate Course requirement

This blog is based on a paper written to fulfill the requirements for the class Public Health 6120: Injury Prevention in the Workplace, Community and Home, at the University of Minnesota. Students were asked to select an injury-related problem pertinent to their own research area and discuss the magnitude of the problem and related issues. Students were also instructed to use an epidemiological approach in developing strategies for prevention and control of injury, specifically incorporating Haddon's Matrix and Haddon's Ten Strategies.

Haddon's Ten Strategies

1) Prevent the creation of the hazard in the first place.
Due to human error, collisions will always occur on the roadway. To prevent the creation of the hazard is to prevent the collision from occurring. Efforts can be made to reduce the risk of a collision, such as advance warning systems and collision mitigation systems; however, to prevent the creation of the hazard is not realistic.

2) Reduce the amount of the hazard brought into being.
To reduce the amount of the hazard is to reduce the number of collisions. EVP systems have already shown to be a benefit to reduce the rate of collisions; however, research is identifying ways to present advance warnings to drivers for an approaching EV not only at intersections, but on all types of roadways.

Other ways to reduce the amount of the hazard is to assess potential risk factors. "A 2004 report by the Federal Emergency Management Agency (FEMA) stated that the occurrence of accidents can be reduced with intensive driver training and assessment" [8]. Increasing driver training, along with adaptive warning systems can reduce the number of collisions. Other areas have already been identified as risk factors, such as driving with lights and sirens. Standards could be placed which specify under which conditions it's necessary to drive with lights and sirens and without.

3) Prevent the release of the hazard that already exists.
An EV crash inherently produces multiple hazards. Within an ambulance, to prevent further hazards from releasing due to the crash would be to secure rear compartment equipment, illuminate sharp corners and edges and provide adequate safety belts for EMSP.

4) Modify the rate or spatial distribution of release of the hazard from its source.
Modifying the rate has been shown to occur by the use of EVP systems. Other methods would be to provide education to drivers and to the public on how to respond to an EV when approaching an intersection or on any roadway.

5) Separate, in time or space, the hazard and that which is being protected.
Hazards resulting from the collision and not the collision itself can be separated in time or space. To separate the hazard would be to not have dangerous surfaces, unsecured equipment and projectiles present during the collision. Such way to do this is by having locking mechanisms on drawers and equipment so when the EV is engaged in a crash, these potentially hazardous objects due not become unsecure.

6) Separate the hazard and that which is to be protected by interposition of a material barrier.
EMSP can wear protective equipment; however, under critical situations, health providers require mobility, therefore a trade-off will exist.

7) Modify basic relevant qualities of the hazard.
Similar to strategy 8 and 2.

8) Make what is to be protected more resistant to damage from the hazard.
The rear compartment of an ambulance does not follow a crashworthiness standard. The compartment is not capable of withstanding the effects of a collision due to the lack of crumple zones which are designed into passenger vehicles [8]. If the rear compartment is design with such zones, the EMSP and patients will become more resistant to damages resulting from the crash.

9) Begin to counter the damage already done by the hazard.
When an EV is on call, constant electronic communication should be exchanged between dispatch and the EV. Therefore, if an EV is involved in a crash and the EMSP is unable to call it in, dispatch already knows and can send support to the scene.

10) Stabilize, repair, and rehabilitate the object of the damage.
By having an additional EV on-call if the first one is involved in a crash can assist in stabilizing injuries that resulted due to the readiness of the second EV to report to the scene of the crash.

Estimated Cost

The economic cost of motor vehicle crashes is readily published by NHTSA; however, the estimated cost due to emergency vehicles involved in a crash is not easily obtainable. The economic impact of motor vehicle crashes in 2000 totaled $230.6 billion which is equivalent to $820 for every person living in the United States. Total property damage costs for all types of crashes (i.e. fatal, injury, non-injury and property damage only) accounted for 26 percent of the total cost ($59 billion). Property damage crashes only were the most costly type of crash [18]. Overall, in the year 2000, there were 37,526 fatal crashes resulting in 41,945 fatalities. Among EVs in 2000, there were 90 fatal crashes totaling 162 fatalities (Figure 1).

Figure 4 illustrates the property damage scores among ambulance, civilian vehicle and surrounding property. "Forty-one percent of the collisions scored only 2, indicating that on average there was minor damage in two categories or moderate damage in one category. The total cost for repairing ambulances during this time period [1989-1997] was $350,938 or approximately 38,900 per year" [4].

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Figure 4: Property damage scores. Values represent the number of collisions for each property damage score from 0 to 9. Figure adapted from Custalow & Gravitz, 2004; Figure 5.

Environmental Characteristics

According to the 11-year retrospective study on fatal ambulance crashes in the United States, 132 (38.9%) fatal crashes occurred between the hours of 1200-1800hrs [5]. This elevated representation of crashes during these hours is consistent with other studies whether being fatal [17] or non-fatal [4, 17]. These studies surprisingly did not show a significant difference in the number of fatal and non fatal crashes based on the month or season of the year.

Location and restraints

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The risk of morbidity and mortality has been shown to differentiate based on the EMSP's seated position within the EV. Specific to ambulance, most severe and fatal injuries occur in the rear compartment (ORfatal/severe=2.7 [95%CI=2.0-3.7] [5]; RRfatal= 5.3 [95%CI=2.1-10.1] and RRsevere=1.2 [95%CI=1.0-1.4] [16]) compared to the frontal compartment. The rear compartment of an ambulance is traditionally where the patient is treated and transported and as a result, the EMSP has to perform medical procedures within this compartment, often improperly restrained or unrestrained. Unrestrained or improperly restrained occupants compared to properly restrained occupants are 2.5-times higher odds for a fatal injury (95%CI=1.8-3.6). Properly restrained occupants within the rear compartment do not differ for severe/fatal injury compared to properly restrained occupants in the front compartment; however, occupants without proper restraints who are in the rear compartment have almost a 3-fold (95%CI=1.8-4.2) higher odds of severe/fatal injury compared to occupants without proper restraints who are located in the front compartment [5]. In a review for hazards associated with EMSP providing care within EVs, Slattery and Silver [8] documented that 40% of the time health care providers are unable to use restraints during the transport of a patient and that 16% of transports the providers are unrestrained throughout the entire transport.

Roadway Junction

Traffic-related researchers have always had an interest in understanding the operation of intersections [15]. "Intersections, where up to 85% of EV injury crashes occur, pose the greatest safety risk" [6]. Among EVs under emergency use between 2000 and 2009, 46% of all fatal [emphasized for website] crashes and 50% of all fatalities occurred within an intersection [7]. This is consistent with previous studies on earlier periods which indicated that between 50-60% of fatal collisions occur at intersections [5].


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Figure 3: Intersections and collisions resulting in injury. Pie slices represent the percentage of collisions occurring at an intersection versus other locations. Figure adapted from Custalow & Gravitz, 2004; Figure 6.

Lights & Sirens (On or Off when in an emergency?)

Emergency medical services personnel operating under code-3 (i.e. lights and sirens) has been debated for its utility because the risk of collisions that result in injuries and fatalities increase under emergency-use driving (Figure 2). The positions of the National Association of EMS Physicians (NAEMSP) and the National Association of State EMS Directors (NASEMSP) is that EMV should operate under lights and sirens only during life-threatening situations in which savings in transport time might have clinical significance. Sanddal et al. [9] review of the literature on lights and sirens suggest that the time saved when an ambulance operates under code-3, as opposed to no lights and sirens, although may have arrived to its destination significantly faster, the time saved may not have had any clinical significance for majority of the cases (review of [10-13]). Gormley et al. [14] study on emergency service vehicles (ESV) collisions in Dublin, Ireland, showed similar results when operating under blue lights (similar to code-3). In Kahn et al. [5] 11-year retrospective study, 60% of crashes and 58% of crash fatalities occurred during emergency use and compared to non-emergency use fatal crashes, emergency use fatal crashes occurred at intersections more often (p<0.001).


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Figure 2: Warning lights and sirens use and collisions resulting in injury. Pie slices represent the percentage of collisions during warning lights and sirens (WLS) use versus other driving modes. Figure adapted from Custalow & Gravitz, 2004; Figure 4.

Risk Factors

Emergency medical services personnel (EMSP) are inherently engaged in a variety of situations where occupationally-related hazards can develop. Due to the nature of the work, which often involve quick and stress induced reactions along with risky maneuvers to prevent the loss of life, occupational hazards can occur at any time during an emergency event. When EMSP are called to an emergency event, time is a crucial factor; the faster the EMSP arrives at the scene, the higher the chance of preserving life. Often the EMS is engaged in high-risk driving maneuvers which can include driving at higher speeds and driving against the flow of traffic [6]. These factors, along with other risk factors such as rural vs. urban driving, driver training and previous driver citations contribute to the overall risk of EMSP-related morbidity and mortality from EV crashes [8].

Trends

According to the National Highway Traffic Safety Administration (NHTSA), between 1991 and 2000, emergency vehicles (EV) (ambulance, fire, and police) were involved in 301,404 nonfatal crashes and 1,565 fatal crashes [4]. The location where most of the crashes occurred were at intersections [5], which accounted for 85% of all EV injury crashes [6]. Between 2000 and 2009 (refer to Figure 1), EVs were involved in a total of 887 fatal crashes, resulting in 1,568 fatalities [7]. The FARS database for EV-use crashes contains a collection of EMSP, patients, occupants in other vehicles, and pedestrian fatalities. To determine if the fatalities were EMSP-specific, individual case files would have to be analyzed by way of assessing driver seat location, rear compartment (if in ambulance) and type of vehicle.

(Figure 1)Emergency Vehicle Use: Fatal Crashes and Deaths (1994-2009)
Data obtain from the National Highway Traffic Safety Administration's (NHTSA) Fatality Analysis Reporting System (FARS) Encyclopedia

EMS provider injury and fatality statistics

In the United States, there are approximately 900,000 certified emergency medical services personnel (EMSP) with 180,000 working full-time. The estimated fatality rate for EMSP within the United States was estimated at a rate of 12.7 per 100,000 [1]. During this time period (1992-1997), the average national occupational fatality rate was 5.0 per 100,000 employed workers in all industries [2]. The estimated fatality rate was derived based on 3 existing databases; the Census of Fatal Occupational Injuries (CFOI), the Fatality Analysis Reporting System (FARS), and the National EMS Memorial Service database. Quantifying the magnitude of fatal and non-fatal occupational injuries for EMSP is difficult since there is no unique industry or occupational code. In addition, the frequent causes and types of injuries have been described at local levels; however, less is known about the incidence of occupationally-related injuries among EMSP at the national level [3].

Transportation-related events were the leading cause of occupational fatalities for EMSP during the time period in which the overall occupational fatality rate was derived. The transportation-specific fatality rate was 9.6 fatalities per 100,000 EMSP. As a comparison, the transportation-specific occupational fatality rate for all workers within the United States was 2.0 per 100,000 workers during the midpoint of the study time period [1]. The transportation-related fatality rate for EMSP is more than four times the average occupational transportation-related fatality rate and the overall EMSP fatality rate is more than twice the average occupational fatality rate.