CONCEPTS, COMPONENTS & CONFIGURATIONS injury, prevention
Injury Control: A Primer for Physicians Injuries are a disease process that costs billions of dollars every year in direct and indirect costs. Despite recent emphasis on prehospital systems and trauma care, prevention of injuries remains an area underutilized by physicians. As a disease process, injuries are amenable to evaluation with epidemiologic tools and subject to prevention by modifying the transmission of energy to human beings. This may occur by either active or passive means of intervention. Physician leadership in the prevention of injuries is importanL yet few physicians have training in injury control. The concepts of injury control are presented by defining the components that create injury and by examining the factors that affect each component. Strategies for identifying countermeasures are described and the merits of each of the applications of countermeasures are discussed. The physician must understand these basic concepts of injury control to an effective leader in developing strategies that mitigate injury in the community. [Martinez R: Injury control: A primer for physicians. Ann Emerg Med January 1990; 19:72-772
Ricardo Martinez, MD, FACEP Stanford, California From the Department of Surgery, Stanford University Medical Center, Stanford, California. Received for publication March 7, 1989. Revision received September 15, 1989. Accepted for publication September 28, 1989. Address for reprints: Ricardo Martinez, MD, Emergency Services, H-1250, Stanford University Hospital, Stanford, California 94305.
INTRODUCTION Injuries account for 12% of hospital admissions and 25% of emergency visits. 1 Injury is the leading cause of physician contacts, ahead of heart and respiratory diseases. 2 The total cost to society in both lives and dollars is enormous. Yet until recently, the emphasis of medical education has traditionally stressed treatment of injuries, not prevention. Nationally, funding for injury control has been lacking. Cardiovascular disease and cancer research receive five to ten times the a m o u n t of money as injury, yet injury is the leading cause of death of Americans under the age 40.1 Of those injured, m a n y are left disabled for life. It is all too c o m m o n to view an injury as an unfavorable outcome of a random event, an "act of God," or the end product of unmindful or foolish behavior. In m a n y minds, the injury is a well-deserved wound that should teach the culprit a lesson. 3 In fact, injury is a disease process. It is the expected result of man's interaction with energy, often in a predictable pattern with predictable effects. This article will discuss h o w an injury occurs and describe the variables that affect the patient's outcome.
DEFINITION OF INJURY An injury is the result of a harmful event that arises from the release of specific forms of physical energy or barriers to normal flow of energy. An injury m a y be intentional or unintentional. Examples of intentional injuries are surgical incisions, suicide, and murder. This article will only consider unintentional injury. In epidemiological terms, an injury is the outcome of the interplay of three components: the agent, the host, and the environment. 4 The causative agent of injury is physical energy. Energy forms that create injury are mechanical, electrical, chemical, thermal, and ionizing and nonionizing radiation. Mechanical (kinetic) energy, the agent of motorvehicle crashes, gunshot wounds, stabbings, and falls, is the m o s t c o m m o n agent found in injury production, s The host, a h u m a n being, varies in predisposition to harm. Variables that make an individual more or less likely to be injured can be divided into
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F I G U R E 1. R e l a t i o n s h i p of perform a n c e to t a s k d e m a n d in controlling energy. W h e n t h e l i n e s cross, an event occurs and energy is free to do
PERFORMANCE AND TASK DEMAND EVENT
harm, g e n e t i c a n d a c q u i r e d factors. 6 Genetic factors include basic intelligence and physical type, sex, react i o n t i m e , a n d c o n g e n i t a l defects. A c q u i r e d f a c t o r s c a n be t r a n s i e n t states such as m e n t a l fatigue, intoxication, drug effects, confusion, and anger, or t h e y can be traits such as judgment, knowledge, social attitudes, lifestyle, and beliefs. Acquired factors can also be permanent changes such as aging and chronic illness. These two factors lead to a lowered t o l e r a n c e to i n j u r y and a decreased ability to recover. T h o u g h t h e a g e n t a n d h o s t are b r o u g h t together, p r o d u c t i o n of disease is not automatic. T h e environm e n t m u s t allow the two to interact. T h e e n v i r o n m e n t m a y enhance or inh i b i t the t r a n s m i s s i o n of energy to the host. But even the act of bringing an agent and host together in a perm i s s i v e e n v i r o n m e n t does n o t i m part disease; the agent m u s t be transm i t t e d to the h o s t b e y o n d the host's t o l e r a b l e l i m i t s . T r a n s m i s s i o n is affected by the total q u a n t i t y and quality of the agent, m o d e of transfer, and the rate of exchange of the agent. Injury to the h o s t depends on the magn i t u d e of these d e t e r m i n a n t s and the properties of the receiving tissue. 7
How Does An Injury Occur? A n i n j u r y occurs w h e n energy is t r a n s m i t t e d to an individual. In order for this to occur, energy m u s t be free or u n c o n t r o l l e d in a permissive environment. As civilization has advanced, mank i n d has i n c r e a s i n g l y h a r n e s s e d energy to serve its needs. Energy is controlled in these settings by a balance between task demand and perform a n c e , s W h e n e n e r g y is u n c o n t r o l l e d , i t b e c o m e s free to c r e a t e
harm, H o w a person executes an action is t h e p e r f o r m a n c e of t h a t t a s k . T h e a m o u n t of skill necessary to execute an a c t i o n is t h e t a s k d e m a n d . As t a s k s differ in c o m p l e x i t y , t a s k dem a n d m a y run the g a m u t from standing in one spot to c l i m b i n g a cliff wall or from reading a b o o k to piloting a rocket. 126/73
PERFORMANCE
TASK DEMAND
EVENT
Because b o t h performance and task d e m a n d f l u c t u a t e over time, p o i n t s occur at w h i c h task d e m a n d will exceed performance: t a s k d e m a n d will suddenly exceed a normal performance, a substandard performance w i l l fall b e l o w a n o r m a l t a s k demand, or a lowered p e r f o r m a n c e . w i l l cross a h i g h e r - t h a n - n o r m a l t a s k demand. Each crossing of the task dem a n d and performance line is called an e v e n t and energy is left u n c o n trolled (Figure 1). In a permissive env i r o n m e n t , t r a n s m i s s i o n of this free energy can occur and an injury m a y result.
Analyzing An Injury Event An injury event usually occurs over a b r i e f t i m e f r a m e . A n a u t o m o b i l e c r a s h , for e x a m p l e , t e r m i nates in less t h a n a t e n t h of a second. Despite this, each injury m a y be analyzed as s u m m a t i o n of t h r e e separate phases:9 Pre-event: the period prior to the liberating of energy. Factors in this phase tend to enhance or inhibit the release of energy. Event: t h e p e r i o d d u r i n g w h i c h e n e r g y is t r a n s m i t t e d to the host. Factors during this phase tend to enhance or in-h i b i t t h e t r a n s m i s s i o n of energy to the host. Post-event: the period imm e d i a t e l y after the event. Factors in this phase tend to amplify or m i n i mize t h e injury. Dividing the injury event into three phases allows the identification of all factors that participate in outcome. Each phase can be further broken d o w n into its c o m p o n e n t parts: agent, h o s t , e n v i r o n m e n t . H a d d o n further crossed t h e s e i n t o a m a t r i x that allows identification of the contributing factors in each phase of the Annals of Emergency Medicine
various components, to A fourth row t h a t t o t a l s the cost of each c o m p o n e n t is often added. N o t e t h a t results of the h u m a n c o m p o n e n t go b e y o n d cost, b u t include pain and suffering, disability, loss of independence, and e m o t i o n a l t r a u m a . A n e x a m p l e of the factors found in the m a t r i x cells is seen (Figure 2). Close e x a m i n a t i o n of t h e m a t r i x reveals t h a t a s i m p l e u n i n t e n t i o n a l injury is really the product of a large n u m b e r of factors and n o t a single identifiable cause. A n u n i n t e n t i o n a l i n j u r y is n o t a r a n d o m o c c u r r e n c e b u t is an expected and foreseen result of a causal chain of factors that bring about an injury.
INJURY PREVENTION Defining the Problem The first step in preventing injury is to recognize its existence as a disease process. Failure to u n d e r s t a n d this has led to inappropriate preventive actions. Second, c o m p l e t e and reliable data m u s t be collected for an i n j u r y p a t t e r n o r m e c h a n i s m to be r e c o g n i z e d . 11 U n f o r t u n a t e l y , d a t a collection tends to be focused on segm e n t s of i n j u r y e v e n t s a n d l i t t l e comprehensive data exist. Emergency d e p a r t m e n t s and t r a u m a registries t e n d to c o l l e c t i n j u r y d a t a by m e c h a n i s m and injuries, b u t abstract f e w c o n t r i b u t i n g f a c t o r s s u c h as r o a d s i d e e l e m e n t s , c o n c o m i t a n t disease, a n d v e h i c l e m o d i f i e r s . C o n v e r s e l y , p o l i c e officers c o l l e c t d a t a f r o m the scene, reconstruct the accident, a n d i n s p e c t t h e v e h i c l e , b u t they are also expected to d e t e r m i n e the n a t u r e and extent of injuries suffered during the crash. In an a t t e m p t to b r o a d e n i n j u r y s u r v e i l l a n c e sys19:1 January 1990
Factors Human
Phases
Vehicle
Pre-event
Impaired capabilities, age, fatigue, alcohol, experience, driving record
Event
Tolerance of human body, injury threshold due to aging, alcohol, chronic disease, etc Type or extent of injury sustained, knowledge of first aid Total physical and mental impairment, grief, pain, emotional trauma
Post-event
Results
Environment
Defective equipment, dirty windows, poor maintenance, improper brake lights Failure of doors, seats, impacting sharp or solid objects, steering column
Narrow road shoulder, poor lighting, road surface type, weather conditions
Bursting gas tank, being trapped inside
Quality of care available, access to emergency service, extrication equipment near Damage to environment, costs to society (loss of lives and income), legal costs
Lack of guardrails; poles and large trees near roadside, oncoming traffic
Sum of costs of vehicular damage and repairs
Prevention Strategy
Example (Automobiles)
Prevent the creation of the particular form of energy in the first place Reduce the amount of energy marshalled Prevent the release of energy that already exists
Banish automobiles, stop producing cars
Modify the rate or spatial distribution of release of energy from its source Separate, in time or space, the energy released from the susceptible structure Interpose a material barrier to block or attenuate the energy transfer Modify contact surfaces, substructures, or basic structures that can be impacted Make susceptible structures more resistant to damage from energy transfer Quickly detect and evaluate damage and counter its continuation or extension. Stabilize, repair, and rehabilitate the object of damage
terns, at least one state is investigating the compilation of accident and a m b u l a n c e reports into one database. 12 Police reports, even for fatal injuries, can be hampered by differences in reporting practices from state to state. A review of death records in California found that the most common location of pedestrian fatalities for children less than 5 years old was private driveways and parking lots, while examination of police data had traditionally found city streets to be the primary location. The traffic po19:1 January 1990
Decrease speeds or weights, produce fewer cars Improve roads and automobile handling, decrease task demand Safety belts, antilock brakes Separate bicycle/pedestrian paths, keep roadside clear of poles and trees Reinforced door panels, guardrails, air bags Padded dashboard, collapsible steering column, breakaway poles Increase human tolerance, strengthen fuel tanks on autos and tanker trucks 911 access, quality emergency services, trauma systems Quality medical care, rehabilitation services
lice did not investigate or report injuries on private property.t3 Despite these flaws, many databases such as public service reports, insurance claims, medical records, and federal registers exist to evaluate injury causation.
3 FIGURE 2. Haddon's matrix. Injuries are the result of complex interactions. This matrix helps identify the factors in each component that inter~ play in the injury event.
Analyzing the Problem
FIGURE 3. Options analysis. These ten rules help to i d e n t i f y possible countermeasures to injury events.
Analysis of the information collected u s u a l l y reveals a high-risk group. 14 This subgroup may be a particular age population, lifestyle, sex, job, or other category. This subgroup may be that population that has the
highest exposure to energy events or those least able to protect themselves when exposed. Haddon's matrix then can be used to identify those factors of each cell
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that may contribute to the injury. Multiple causes may be identified in each cell, and some cells may overlap. A list can be generated that identifies areas where preventive counterm e a s u r e s m a y b r e a k the c a u s a l chain. Another method to generate such a list is called options analysis (Figure 3). Haddon developed a series of ten a p p r o a c h e s for i n j u r y c o u n t e r measures that sequentially parallel the stages from marshalling of energy, through the transmission, and after the creation of an injury. 15 Application of these ten options to a particular problem helps to identify most of the possible preventive interventions. These options do not rely on understanding causation, but are directed at minimizing the harmful effects of energy. The identification of a possible countermeasure and the application of that countermeasure are not synonymous. Once possible interventions are identified, they must be evaluated for applicability in terms of cost, practicality, and effectiveness. 16 In the example with automobiles, the first option, banishing automobiles, does not meet any of these criteria and would be impossible to implement. However, option 5, which separates the energy source from those susceptible, is clearly a practical approach. Because multiple actions affect the end result, multiple interventions are relevant. These countermeasures generally fall into one of three categories: education, enforcement, or engineering. The physician must understand the limitations and capabilities that affect the applicability. Knowledge of these elements is essential to planning injury prevention strategies.
Approaches to Injury Prevention The approaches used for injury prevention may be categorized into two areas: active and passive techniques. 17 Education and enforcement are active techniques because they require the host to do something in order to receive protection. Engineering approaches are considered passive techniques because the host receives protection with use of an object or vehicle.
Education Education is the m o s t c o m m o n method used and probably the easiest 128/75
to implement. The basic concept is that a person, once given information or skill training, will retain what has been taught and use it to reduce the risk of injury. The ultimate purpose of education in injury prevention is to change behavior. To change behavior, the student must be able to comprehend, analyze, judge, and then apply this knowledge. Educational programs have not always been e v a l u a t e d p r o p e r l y in t e r m s of b e h a v i o r and o u t c o m e . When such studies do occur, the evidence may show little improvement in these parameters. Some evidence exists that driver education and motorcycle training courses are linked with an increased mortality of its students. 1s-z1 Those at highest risk, such as drunk drivers or teenagers, are not very likely to be influenced by education programs because they do not perceive that a problem exists for them. 2~ Often, the initial accomplishments of an e d u c a t i o n a l c a m p a i g n are highly touted without a more longt e r m e v a l u a t i o n of effectiveness. Over time, cigarette package warning labels go u n n o t i c e d and seat belt campaigns leave little behind. 23 Despite these drawbacks, education is a powerful tool. Change in social attitudes can occur with education and mass media campaigns. Armed with information, population support for an issue can be cultivated and grow. Medical professionals are in an opportune position to continually educate and reinforce basic concepts of injury prevention to patients. A keen eye must be cast on an injured patients for factors that increase the risk of injury. Constant education directed toward individuals and their families can slowly create a positive and p r o t e c t i v e a t t i t u d e and safe, healthy home environment.
Enforcement Legal and administrative directives are considered active techniqnes. By requiring action to be taken, protection is imparted. Directives are considered more effective than education. For example, it is much more effective to require electrical wiring to meet certain safety codes than to educate the population on electrical safety. There are, however, numerous limitations and restrictions to implementation of legal and administraAnnals of Emergency Medicine
tive directives. 8 Society must see the need for such a rule. Generally, Americans support a directive if they perceive that it will stop someone else from injuring them, but oppose a ruling that prevents one from harming oneself. We tend to s u p p o r t laws r e g u l a t i n g drunk drivers, but dislike safety belt, gun control, or motorcycle helmet laws. Simply put, we like laws that affect other people and dislike those that affect us individually. It is hard to convince people that the increased cost of preventable injuries to society affects them as well. The most c o m m o n arguments against a ruling are those of personal f r e e d o m and c o s t - e f f e c t i v e n e s s . 24 Perhaps the best example of this has been the argument about air bags. First developed in the 1950s and ready for use in the 1960s, air bags were first mandated in 1970. Since that time, debate and political maneuvers have delayed implementation.ZS Legal rulings can be very effective. Motorcycle helmet and childproof container laws have been shown to substantially reduce morbidity and mortality.5, 26 However, rulings are mitigated by three characteristics: exemptions, ability to enforce, and degree of conviction. 6 Exemptions tend to diminish the power of a ruling by making it vague or ambiguous, or abating the intent. Age limitations on motorcycle helmet laws and provisions in seat belt laws that allow enforcement only if the driver is stopped for another offense make these laws virtually useless. Compliance to a ruling is both a function of local resources a n d ease of enforcement. If the p o p u l a t i o n does not believe that apprehension is likely, then there is little reason to abide by a rule. In order to be enforceable, the law must be easily observable. C o m p l i a n c e to m o t o r c y c l e helmet-use laws is nearly 99%, while that of seat belt laws varies substantially.27, 2s From a distance, a p o l i c e officer can easily discern if a helmet is worn, but m a y n o t observe if safety belts are used. The ability to convict those found in violation of a ruling influences the c o m p l i a n c e to it. If apprehension does not lead to conviction, compliance decreases and the ruling bec o m e s ineffective. I n t e r e s t i n g l y , 19:1 January 1990
m o r e s e v e r e p e n a l t i e s t e n d to decrease the conviction rate because t h e y m a k e it less l i k e l y that all the steps necessary for conviction will be completed. Neither education nor enforcem e n t w o r k well in a vacuum. Over t i m e , b o t h are a t t e n u a t e d . T h e r e is s o m e evidence to show a synergistic effect w h e n used in c o n j u n c t i o n . 29,3°
Engineering E n g i n e e r i n g s a f e t y or p r o t e c t i o n i n t o an object being used is considered a passive action. The person receives p r o t e c t i o n w i t h its use. N o additional action is necessary by t h e individual. For example, education about boating safety and rulings that m a k e life vests m a n d a t o r y m a y have l i t t l e effect w h e n a boat capsizes, but engineering a flotation hull will prev e n t sinking and help passengers stay afloat. U n l i k e education and enforcement, this approach can intervene at the event phase. It is the m o s t effective form of injury control, but it too suffers from m u l t i p l e problems w i t h implementation. S t a n d a r d a r g u m e n t s against engin e e r i n g s a f e t y are s i m i l a r to t h o s e u s e d a g a i n s t rulings: p e r s o n a l freed o m and cost-effectiveness.31, 3~ As a m a t t e r of fact, both were used in the a r g u m e n t s against air bags. But few p e o p l e c a n argue t h a t e n g i n e e r i n g p r o t e c t i o n has n o t saved t h o u s a n d s of lives. Again, we as a society tend to d e m a n d safety be built into i t e m s used for us, but not for those we use.
Post-Event Interventions O n c e a n e v e n t is t e r m i n a t e d , prompt action can minimize the h a r m f u l effect. Engineering can help here, too. Use of Haddon's m a t r i x reveals areas of intervention. Gas tanks t h a t do n o t b u r s t can reduce postcrash fires, call-boxes can s u m m o n m e d i c a l care, a n d d e v e l o p m e n t of prehospital and t r a u m a systems can d i m i n i s h the severity of injuries produced by the event.
EVALUATING INTERVENTIONS Despite the best intentions, no preventive intervention should be thought successful without proper a p p r a i s a l of t h e e n d r e s u l t . T h r e e questions m u s t be asked of any educational program: Have attitudes, skills, or j u d g m e n t changed? Has behavior changed? Does behavioral 19:1 January 1990
change lead to a favorable outcome? It is the o u t c o m e that is m o s t important. If the first two questions are answered positively, but o u t c o m e is n o t affected, the program is n o t effective. Legal approaches tend to do best if o n e a c t i o n is d e m a n d e d i n s t e a d of m u l t i p l e actions. If m u l t i p l e actions are required, people tend to develop a l t e r n a t i v e s to get a r o u n d t h e law. R e q u i r i n g s m o k e d e t e c t o r s in a h o u s e requires one a c t i o n to confer protection. Earlier a t t e m p t s to design cars w i t h a seat b e l t s y s t e m connected to the ignition enticed people to a l w a y s k e e p t h e s e a t b e l t s connected. 3a T h e y then sat on top of the belt, rendering it useless. I m p l e m e n t a t i o n of s o m e legal or a d m i n i s t r a tive rulings have shown a positive result, but w h e n the results were comp a r e d to s u r r o u n d i n g areas w i t h o u t the program, no difference was s e e n . 34
THE PHYSICIAN'S ROLE T h e p h y s i c i a n s h o u l d not undere s t i m a t e his position in the c o m m u nity. Despite the popular perception t h a t the p h y s i c i a n has lost t h e est e e m of t h e p u b l i c , t h e p h y s i c i a n w h o speaks out for injury control is heard. T h e physician is in a unique position to initiate injury control strategies on the local and n a t i o n a l level. T h e roles that the physician can play in injury control are many, from data c o l l e c t i o n and p a t i e n t e d u c a t i o n to m o b i l i z i n g c o m m u n i t y s u p p o r t and l e g i s l a t i v e action. E m e r g e n c y medicine does n o t s u b s p e c i a l i z e further into the m e d i c a l organization, b u t instead, reaches into the c o m m u n i t y as p r e h o s p i t a l care, t r a u m a s y s t e m s , and disaster m a n a g e m e n t . Injury control is a n a t u r a l concept for the emergency p h y s i c i a n to grasp and develop in the c o m m u n i t y . Letters to public officials, talks to civic organizations and school groups, and presentations to professional groups are all avenues by w h i c h to educate the c o m m u n i t y and elicit change. P h y s i c i a n leadership can t h u s i m p a r t a t r e m e n d o u s positive influence toward creating a safer c o m m u n i t y .
REFERENCES 1. Committee on Trauma Research: Injury in America: A Continuing Public Health Problem. Washington, DC, National Academy Press, 1985. 2. Centers for Disease Control: Table V. Years
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of potential life lost, deaths, and death rates, by cause of death, and estimated numbers of physician contacts by principal diagnosis, United States. MMWR 1985;34:761. 3. Wigglesworth EC: The fault doctrine and injury control. J Trauma 1978;18:789-794. 4. Waller JA: Injury Control: A Guide to the Causes and Prevention of Trauma. Lexington, Massachusetts, Lexington Books, 1985. 5. Baker SP, O'Neill B, Karpf RS: The Injury Fact Book. Lexington, Massachusetts, Lexington Books, 1985. 6. Robertson LS: Injuries: Causes, Control Strategies, and Public Policy. Lexington, Lex M ington Books, 1983. 7. Viano DC: Cause and control of automotive trauma. Bull N Y Acad Med 1988;64:376-421. 8. Waller JA: Prevention of premature death and disability due to injury, in Last JM (ed): Public Health and Preventive Medicine ed 12. Norwalk, Connecticut, Appleton-CenturyCrofts, 1986. 9. Haddon W Jr: The changing approach to the epidemiology prevention, and amelioration of trauma: The transition to approaches etiologically rather then descriptively based. Am J Public Health 1968;58:1431-1438. 10. Haddon W Jr: A logical framework for categorizing highway safety phenomena and activity. ] Trauma 1972;12:193-207. 11. Bull JP: A strategy for injury prevention. Tex Med 1983;79:51-54. 12. Channell S: West Virginia State EM8. Personal communication. 13. Mueller BA, Rivara FP, Bergman AB: Factors associated with pedestrian-vehicle collision injuries and fatalities. West J Med 1987;146: 243-245. 14. Withers BF, Baker, SP: Epidemiology and prevention of injuries. Emerg Med Cliu North Am 1984;2:701-716. 15. Haddon W Jr: Energy damage and the ten countermeasure strategies. J Trauma 1973;13: 321-331. 16. Haddon W Jr, Baker SP: Injury control, in Clark D, MacMahon B (eds}: Preventive and Corr~munity Medicine, ed 2. Boston, Little, Brown and Co, 1982, p 1-45. 17. Haddon W Jr: Strategy in preventive medicine: Active versus passive approaches to reducing human wastage. J Trauma 1974;14:353-354. 18. Kraus JF~ Riggins RS, Franti CE: Some epidemiologic features of motorcycle collision injuries, I: Introduction, methods, and factors associated with incidence. A m J Epidemiology 1975;102:74-97. 19. Robertson LA, Zador P: Driver education and fatal crash involvement of teenaged drivers. A m J Public Health 1978;68:959-965. 20. Status report: Two studies question value of motorcycle licensing program. Insurance Institute for Highway Safety, August 13, 1988;23: 1-6. 21. Robertson LS: Crash involvement of teenaged drivers when driver education is eliminated from the high school. A m J Public Health 1980; 70:599-603. 22. Ross HL, Gonzales P: Effects of license revocation in drunk driving offenders. Accid Anal Prey 1988;20:379-391.
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23. Richards JW, Fischer P, Conner FG: The warnings on cigarette packages are ineffective. JAMA 1989;261:45.
Motorcycle Helmet Use in Relation to Legal Requirements. Washington DC, Insurance Institute for Highway Safety, t979.
24. Baker SP: On lobbies, liberty, and the public good. A m J Public Health 1980;70:573-575.25.
28. Nelson GD, Moffet PA: Safety belt promotion: Theory and practice. Accid Anal Prey 1988;20:27-38.
25. Air Bags: A Chronological History of Delay. Washington, DC, Insurance Institute for Highway Safety, 198I.
29. Pace BW, Thailer R, Kuratkowski TG: New York state mandatory seatbelt use law: Patterns of seatbeh use before and after legislation. J Trauma 1986;26:1031-1033.
26. Baker SP: Injuries: The neglected epidemic: Stone lecture, 1985 American Trauma Society meeting. J Trauma 1987;27:343-348. 27. Williams AF, Ginsburg MJ, Burchmen PF:
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30. Williams AF, Lund AK: Seatbelt law use and occupant crashing protection in the United States. A m J Public Health 1986;76:1438-1441.
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31. Perkins RJ: Perspective on the public good. Am J Public Health 1981;71:294-295. 32. Baker SP, Teret SP: Freedom and protection: A balancing of interests. A m J Public Health 1981;71:295-297. 33. Robertson LS, Haddon W: The buzzer-light reminder system and safety belt use. A m J Public Health 1974;64:814-815. 34. Campbell D% Ross HL: The Connecticut crackdown on speeding: Time-series data in quasi-experimental analysis. Law and Society Review 1969;3:33-53.
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Injury Control: A Primer for Physicians Injuries are a disease process that costs billions of dollars every year in direct and indirect costs. Despite recent emphasis on prehospital systems and trauma care, prevention of injuries remains an area underutilized by physicians. As a disease process, injuries are amenable to evaluation with epidemiologic tools and subject to prevention by modifying the transmission of energy to human beings. This may occur by either active or passive means of intervention. Physician leadership in the prevention of injuries is importanL yet few physicians have training in injury control. The concepts of injury control are presented by defining the components that create injury and by examining the factors that affect each component. Strategies for identifying countermeasures are described and the merits of each of the applications of countermeasures are discussed. The physician must understand these basic concepts of injury control to an effective leader in developing strategies that mitigate injury in the community. [Martinez R: Injury control: A primer for physicians. Ann Emerg Med January 1990; 19:72-772
Ricardo Martinez, MD, FACEP Stanford, California From the Department of Surgery, Stanford University Medical Center, Stanford, California. Received for publication March 7, 1989. Revision received September 15, 1989. Accepted for publication September 28, 1989. Address for reprints: Ricardo Martinez, MD, Emergency Services, H-1250, Stanford University Hospital, Stanford, California 94305.
INTRODUCTION Injuries account for 12% of hospital admissions and 25% of emergency visits. 1 Injury is the leading cause of physician contacts, ahead of heart and respiratory diseases. 2 The total cost to society in both lives and dollars is enormous. Yet until recently, the emphasis of medical education has traditionally stressed treatment of injuries, not prevention. Nationally, funding for injury control has been lacking. Cardiovascular disease and cancer research receive five to ten times the a m o u n t of money as injury, yet injury is the leading cause of death of Americans under the age 40.1 Of those injured, m a n y are left disabled for life. It is all too c o m m o n to view an injury as an unfavorable outcome of a random event, an "act of God," or the end product of unmindful or foolish behavior. In m a n y minds, the injury is a well-deserved wound that should teach the culprit a lesson. 3 In fact, injury is a disease process. It is the expected result of man's interaction with energy, often in a predictable pattern with predictable effects. This article will discuss h o w an injury occurs and describe the variables that affect the patient's outcome.
DEFINITION OF INJURY An injury is the result of a harmful event that arises from the release of specific forms of physical energy or barriers to normal flow of energy. An injury m a y be intentional or unintentional. Examples of intentional injuries are surgical incisions, suicide, and murder. This article will only consider unintentional injury. In epidemiological terms, an injury is the outcome of the interplay of three components: the agent, the host, and the environment. 4 The causative agent of injury is physical energy. Energy forms that create injury are mechanical, electrical, chemical, thermal, and ionizing and nonionizing radiation. Mechanical (kinetic) energy, the agent of motorvehicle crashes, gunshot wounds, stabbings, and falls, is the m o s t c o m m o n agent found in injury production, s The host, a h u m a n being, varies in predisposition to harm. Variables that make an individual more or less likely to be injured can be divided into
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F I G U R E 1. R e l a t i o n s h i p of perform a n c e to t a s k d e m a n d in controlling energy. W h e n t h e l i n e s cross, an event occurs and energy is free to do
PERFORMANCE AND TASK DEMAND EVENT
harm, g e n e t i c a n d a c q u i r e d factors. 6 Genetic factors include basic intelligence and physical type, sex, react i o n t i m e , a n d c o n g e n i t a l defects. A c q u i r e d f a c t o r s c a n be t r a n s i e n t states such as m e n t a l fatigue, intoxication, drug effects, confusion, and anger, or t h e y can be traits such as judgment, knowledge, social attitudes, lifestyle, and beliefs. Acquired factors can also be permanent changes such as aging and chronic illness. These two factors lead to a lowered t o l e r a n c e to i n j u r y and a decreased ability to recover. T h o u g h t h e a g e n t a n d h o s t are b r o u g h t together, p r o d u c t i o n of disease is not automatic. T h e environm e n t m u s t allow the two to interact. T h e e n v i r o n m e n t m a y enhance or inh i b i t the t r a n s m i s s i o n of energy to the host. But even the act of bringing an agent and host together in a perm i s s i v e e n v i r o n m e n t does n o t i m part disease; the agent m u s t be transm i t t e d to the h o s t b e y o n d the host's t o l e r a b l e l i m i t s . T r a n s m i s s i o n is affected by the total q u a n t i t y and quality of the agent, m o d e of transfer, and the rate of exchange of the agent. Injury to the h o s t depends on the magn i t u d e of these d e t e r m i n a n t s and the properties of the receiving tissue. 7
How Does An Injury Occur? A n i n j u r y occurs w h e n energy is t r a n s m i t t e d to an individual. In order for this to occur, energy m u s t be free or u n c o n t r o l l e d in a permissive environment. As civilization has advanced, mank i n d has i n c r e a s i n g l y h a r n e s s e d energy to serve its needs. Energy is controlled in these settings by a balance between task demand and perform a n c e , s W h e n e n e r g y is u n c o n t r o l l e d , i t b e c o m e s free to c r e a t e
harm, H o w a person executes an action is t h e p e r f o r m a n c e of t h a t t a s k . T h e a m o u n t of skill necessary to execute an a c t i o n is t h e t a s k d e m a n d . As t a s k s differ in c o m p l e x i t y , t a s k dem a n d m a y run the g a m u t from standing in one spot to c l i m b i n g a cliff wall or from reading a b o o k to piloting a rocket. 126/73
PERFORMANCE
TASK DEMAND
EVENT
Because b o t h performance and task d e m a n d f l u c t u a t e over time, p o i n t s occur at w h i c h task d e m a n d will exceed performance: t a s k d e m a n d will suddenly exceed a normal performance, a substandard performance w i l l fall b e l o w a n o r m a l t a s k demand, or a lowered p e r f o r m a n c e . w i l l cross a h i g h e r - t h a n - n o r m a l t a s k demand. Each crossing of the task dem a n d and performance line is called an e v e n t and energy is left u n c o n trolled (Figure 1). In a permissive env i r o n m e n t , t r a n s m i s s i o n of this free energy can occur and an injury m a y result.
Analyzing An Injury Event An injury event usually occurs over a b r i e f t i m e f r a m e . A n a u t o m o b i l e c r a s h , for e x a m p l e , t e r m i nates in less t h a n a t e n t h of a second. Despite this, each injury m a y be analyzed as s u m m a t i o n of t h r e e separate phases:9 Pre-event: the period prior to the liberating of energy. Factors in this phase tend to enhance or inhibit the release of energy. Event: t h e p e r i o d d u r i n g w h i c h e n e r g y is t r a n s m i t t e d to the host. Factors during this phase tend to enhance or in-h i b i t t h e t r a n s m i s s i o n of energy to the host. Post-event: the period imm e d i a t e l y after the event. Factors in this phase tend to amplify or m i n i mize t h e injury. Dividing the injury event into three phases allows the identification of all factors that participate in outcome. Each phase can be further broken d o w n into its c o m p o n e n t parts: agent, h o s t , e n v i r o n m e n t . H a d d o n further crossed t h e s e i n t o a m a t r i x that allows identification of the contributing factors in each phase of the Annals of Emergency Medicine
various components, to A fourth row t h a t t o t a l s the cost of each c o m p o n e n t is often added. N o t e t h a t results of the h u m a n c o m p o n e n t go b e y o n d cost, b u t include pain and suffering, disability, loss of independence, and e m o t i o n a l t r a u m a . A n e x a m p l e of the factors found in the m a t r i x cells is seen (Figure 2). Close e x a m i n a t i o n of t h e m a t r i x reveals t h a t a s i m p l e u n i n t e n t i o n a l injury is really the product of a large n u m b e r of factors and n o t a single identifiable cause. A n u n i n t e n t i o n a l i n j u r y is n o t a r a n d o m o c c u r r e n c e b u t is an expected and foreseen result of a causal chain of factors that bring about an injury.
INJURY PREVENTION Defining the Problem The first step in preventing injury is to recognize its existence as a disease process. Failure to u n d e r s t a n d this has led to inappropriate preventive actions. Second, c o m p l e t e and reliable data m u s t be collected for an i n j u r y p a t t e r n o r m e c h a n i s m to be r e c o g n i z e d . 11 U n f o r t u n a t e l y , d a t a collection tends to be focused on segm e n t s of i n j u r y e v e n t s a n d l i t t l e comprehensive data exist. Emergency d e p a r t m e n t s and t r a u m a registries t e n d to c o l l e c t i n j u r y d a t a by m e c h a n i s m and injuries, b u t abstract f e w c o n t r i b u t i n g f a c t o r s s u c h as r o a d s i d e e l e m e n t s , c o n c o m i t a n t disease, a n d v e h i c l e m o d i f i e r s . C o n v e r s e l y , p o l i c e officers c o l l e c t d a t a f r o m the scene, reconstruct the accident, a n d i n s p e c t t h e v e h i c l e , b u t they are also expected to d e t e r m i n e the n a t u r e and extent of injuries suffered during the crash. In an a t t e m p t to b r o a d e n i n j u r y s u r v e i l l a n c e sys19:1 January 1990
Factors Human
Phases
Vehicle
Pre-event
Impaired capabilities, age, fatigue, alcohol, experience, driving record
Event
Tolerance of human body, injury threshold due to aging, alcohol, chronic disease, etc Type or extent of injury sustained, knowledge of first aid Total physical and mental impairment, grief, pain, emotional trauma
Post-event
Results
Environment
Defective equipment, dirty windows, poor maintenance, improper brake lights Failure of doors, seats, impacting sharp or solid objects, steering column
Narrow road shoulder, poor lighting, road surface type, weather conditions
Bursting gas tank, being trapped inside
Quality of care available, access to emergency service, extrication equipment near Damage to environment, costs to society (loss of lives and income), legal costs
Lack of guardrails; poles and large trees near roadside, oncoming traffic
Sum of costs of vehicular damage and repairs
Prevention Strategy
Example (Automobiles)
Prevent the creation of the particular form of energy in the first place Reduce the amount of energy marshalled Prevent the release of energy that already exists
Banish automobiles, stop producing cars
Modify the rate or spatial distribution of release of energy from its source Separate, in time or space, the energy released from the susceptible structure Interpose a material barrier to block or attenuate the energy transfer Modify contact surfaces, substructures, or basic structures that can be impacted Make susceptible structures more resistant to damage from energy transfer Quickly detect and evaluate damage and counter its continuation or extension. Stabilize, repair, and rehabilitate the object of damage
terns, at least one state is investigating the compilation of accident and a m b u l a n c e reports into one database. 12 Police reports, even for fatal injuries, can be hampered by differences in reporting practices from state to state. A review of death records in California found that the most common location of pedestrian fatalities for children less than 5 years old was private driveways and parking lots, while examination of police data had traditionally found city streets to be the primary location. The traffic po19:1 January 1990
Decrease speeds or weights, produce fewer cars Improve roads and automobile handling, decrease task demand Safety belts, antilock brakes Separate bicycle/pedestrian paths, keep roadside clear of poles and trees Reinforced door panels, guardrails, air bags Padded dashboard, collapsible steering column, breakaway poles Increase human tolerance, strengthen fuel tanks on autos and tanker trucks 911 access, quality emergency services, trauma systems Quality medical care, rehabilitation services
lice did not investigate or report injuries on private property.t3 Despite these flaws, many databases such as public service reports, insurance claims, medical records, and federal registers exist to evaluate injury causation.
3 FIGURE 2. Haddon's matrix. Injuries are the result of complex interactions. This matrix helps identify the factors in each component that inter~ play in the injury event.
Analyzing the Problem
FIGURE 3. Options analysis. These ten rules help to i d e n t i f y possible countermeasures to injury events.
Analysis of the information collected u s u a l l y reveals a high-risk group. 14 This subgroup may be a particular age population, lifestyle, sex, job, or other category. This subgroup may be that population that has the
highest exposure to energy events or those least able to protect themselves when exposed. Haddon's matrix then can be used to identify those factors of each cell
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that may contribute to the injury. Multiple causes may be identified in each cell, and some cells may overlap. A list can be generated that identifies areas where preventive counterm e a s u r e s m a y b r e a k the c a u s a l chain. Another method to generate such a list is called options analysis (Figure 3). Haddon developed a series of ten a p p r o a c h e s for i n j u r y c o u n t e r measures that sequentially parallel the stages from marshalling of energy, through the transmission, and after the creation of an injury. 15 Application of these ten options to a particular problem helps to identify most of the possible preventive interventions. These options do not rely on understanding causation, but are directed at minimizing the harmful effects of energy. The identification of a possible countermeasure and the application of that countermeasure are not synonymous. Once possible interventions are identified, they must be evaluated for applicability in terms of cost, practicality, and effectiveness. 16 In the example with automobiles, the first option, banishing automobiles, does not meet any of these criteria and would be impossible to implement. However, option 5, which separates the energy source from those susceptible, is clearly a practical approach. Because multiple actions affect the end result, multiple interventions are relevant. These countermeasures generally fall into one of three categories: education, enforcement, or engineering. The physician must understand the limitations and capabilities that affect the applicability. Knowledge of these elements is essential to planning injury prevention strategies.
Approaches to Injury Prevention The approaches used for injury prevention may be categorized into two areas: active and passive techniques. 17 Education and enforcement are active techniques because they require the host to do something in order to receive protection. Engineering approaches are considered passive techniques because the host receives protection with use of an object or vehicle.
Education Education is the m o s t c o m m o n method used and probably the easiest 128/75
to implement. The basic concept is that a person, once given information or skill training, will retain what has been taught and use it to reduce the risk of injury. The ultimate purpose of education in injury prevention is to change behavior. To change behavior, the student must be able to comprehend, analyze, judge, and then apply this knowledge. Educational programs have not always been e v a l u a t e d p r o p e r l y in t e r m s of b e h a v i o r and o u t c o m e . When such studies do occur, the evidence may show little improvement in these parameters. Some evidence exists that driver education and motorcycle training courses are linked with an increased mortality of its students. 1s-z1 Those at highest risk, such as drunk drivers or teenagers, are not very likely to be influenced by education programs because they do not perceive that a problem exists for them. 2~ Often, the initial accomplishments of an e d u c a t i o n a l c a m p a i g n are highly touted without a more longt e r m e v a l u a t i o n of effectiveness. Over time, cigarette package warning labels go u n n o t i c e d and seat belt campaigns leave little behind. 23 Despite these drawbacks, education is a powerful tool. Change in social attitudes can occur with education and mass media campaigns. Armed with information, population support for an issue can be cultivated and grow. Medical professionals are in an opportune position to continually educate and reinforce basic concepts of injury prevention to patients. A keen eye must be cast on an injured patients for factors that increase the risk of injury. Constant education directed toward individuals and their families can slowly create a positive and p r o t e c t i v e a t t i t u d e and safe, healthy home environment.
Enforcement Legal and administrative directives are considered active techniqnes. By requiring action to be taken, protection is imparted. Directives are considered more effective than education. For example, it is much more effective to require electrical wiring to meet certain safety codes than to educate the population on electrical safety. There are, however, numerous limitations and restrictions to implementation of legal and administraAnnals of Emergency Medicine
tive directives. 8 Society must see the need for such a rule. Generally, Americans support a directive if they perceive that it will stop someone else from injuring them, but oppose a ruling that prevents one from harming oneself. We tend to s u p p o r t laws r e g u l a t i n g drunk drivers, but dislike safety belt, gun control, or motorcycle helmet laws. Simply put, we like laws that affect other people and dislike those that affect us individually. It is hard to convince people that the increased cost of preventable injuries to society affects them as well. The most c o m m o n arguments against a ruling are those of personal f r e e d o m and c o s t - e f f e c t i v e n e s s . 24 Perhaps the best example of this has been the argument about air bags. First developed in the 1950s and ready for use in the 1960s, air bags were first mandated in 1970. Since that time, debate and political maneuvers have delayed implementation.ZS Legal rulings can be very effective. Motorcycle helmet and childproof container laws have been shown to substantially reduce morbidity and mortality.5, 26 However, rulings are mitigated by three characteristics: exemptions, ability to enforce, and degree of conviction. 6 Exemptions tend to diminish the power of a ruling by making it vague or ambiguous, or abating the intent. Age limitations on motorcycle helmet laws and provisions in seat belt laws that allow enforcement only if the driver is stopped for another offense make these laws virtually useless. Compliance to a ruling is both a function of local resources a n d ease of enforcement. If the p o p u l a t i o n does not believe that apprehension is likely, then there is little reason to abide by a rule. In order to be enforceable, the law must be easily observable. C o m p l i a n c e to m o t o r c y c l e helmet-use laws is nearly 99%, while that of seat belt laws varies substantially.27, 2s From a distance, a p o l i c e officer can easily discern if a helmet is worn, but m a y n o t observe if safety belts are used. The ability to convict those found in violation of a ruling influences the c o m p l i a n c e to it. If apprehension does not lead to conviction, compliance decreases and the ruling bec o m e s ineffective. I n t e r e s t i n g l y , 19:1 January 1990
m o r e s e v e r e p e n a l t i e s t e n d to decrease the conviction rate because t h e y m a k e it less l i k e l y that all the steps necessary for conviction will be completed. Neither education nor enforcem e n t w o r k well in a vacuum. Over t i m e , b o t h are a t t e n u a t e d . T h e r e is s o m e evidence to show a synergistic effect w h e n used in c o n j u n c t i o n . 29,3°
Engineering E n g i n e e r i n g s a f e t y or p r o t e c t i o n i n t o an object being used is considered a passive action. The person receives p r o t e c t i o n w i t h its use. N o additional action is necessary by t h e individual. For example, education about boating safety and rulings that m a k e life vests m a n d a t o r y m a y have l i t t l e effect w h e n a boat capsizes, but engineering a flotation hull will prev e n t sinking and help passengers stay afloat. U n l i k e education and enforcement, this approach can intervene at the event phase. It is the m o s t effective form of injury control, but it too suffers from m u l t i p l e problems w i t h implementation. S t a n d a r d a r g u m e n t s against engin e e r i n g s a f e t y are s i m i l a r to t h o s e u s e d a g a i n s t rulings: p e r s o n a l freed o m and cost-effectiveness.31, 3~ As a m a t t e r of fact, both were used in the a r g u m e n t s against air bags. But few p e o p l e c a n argue t h a t e n g i n e e r i n g p r o t e c t i o n has n o t saved t h o u s a n d s of lives. Again, we as a society tend to d e m a n d safety be built into i t e m s used for us, but not for those we use.
Post-Event Interventions O n c e a n e v e n t is t e r m i n a t e d , prompt action can minimize the h a r m f u l effect. Engineering can help here, too. Use of Haddon's m a t r i x reveals areas of intervention. Gas tanks t h a t do n o t b u r s t can reduce postcrash fires, call-boxes can s u m m o n m e d i c a l care, a n d d e v e l o p m e n t of prehospital and t r a u m a systems can d i m i n i s h the severity of injuries produced by the event.
EVALUATING INTERVENTIONS Despite the best intentions, no preventive intervention should be thought successful without proper a p p r a i s a l of t h e e n d r e s u l t . T h r e e questions m u s t be asked of any educational program: Have attitudes, skills, or j u d g m e n t changed? Has behavior changed? Does behavioral 19:1 January 1990
change lead to a favorable outcome? It is the o u t c o m e that is m o s t important. If the first two questions are answered positively, but o u t c o m e is n o t affected, the program is n o t effective. Legal approaches tend to do best if o n e a c t i o n is d e m a n d e d i n s t e a d of m u l t i p l e actions. If m u l t i p l e actions are required, people tend to develop a l t e r n a t i v e s to get a r o u n d t h e law. R e q u i r i n g s m o k e d e t e c t o r s in a h o u s e requires one a c t i o n to confer protection. Earlier a t t e m p t s to design cars w i t h a seat b e l t s y s t e m connected to the ignition enticed people to a l w a y s k e e p t h e s e a t b e l t s connected. 3a T h e y then sat on top of the belt, rendering it useless. I m p l e m e n t a t i o n of s o m e legal or a d m i n i s t r a tive rulings have shown a positive result, but w h e n the results were comp a r e d to s u r r o u n d i n g areas w i t h o u t the program, no difference was s e e n . 34
THE PHYSICIAN'S ROLE T h e p h y s i c i a n s h o u l d not undere s t i m a t e his position in the c o m m u nity. Despite the popular perception t h a t the p h y s i c i a n has lost t h e est e e m of t h e p u b l i c , t h e p h y s i c i a n w h o speaks out for injury control is heard. T h e physician is in a unique position to initiate injury control strategies on the local and n a t i o n a l level. T h e roles that the physician can play in injury control are many, from data c o l l e c t i o n and p a t i e n t e d u c a t i o n to m o b i l i z i n g c o m m u n i t y s u p p o r t and l e g i s l a t i v e action. E m e r g e n c y medicine does n o t s u b s p e c i a l i z e further into the m e d i c a l organization, b u t instead, reaches into the c o m m u n i t y as p r e h o s p i t a l care, t r a u m a s y s t e m s , and disaster m a n a g e m e n t . Injury control is a n a t u r a l concept for the emergency p h y s i c i a n to grasp and develop in the c o m m u n i t y . Letters to public officials, talks to civic organizations and school groups, and presentations to professional groups are all avenues by w h i c h to educate the c o m m u n i t y and elicit change. P h y s i c i a n leadership can t h u s i m p a r t a t r e m e n d o u s positive influence toward creating a safer c o m m u n i t y .
REFERENCES 1. Committee on Trauma Research: Injury in America: A Continuing Public Health Problem. Washington, DC, National Academy Press, 1985. 2. Centers for Disease Control: Table V. Years
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of potential life lost, deaths, and death rates, by cause of death, and estimated numbers of physician contacts by principal diagnosis, United States. MMWR 1985;34:761. 3. Wigglesworth EC: The fault doctrine and injury control. J Trauma 1978;18:789-794. 4. Waller JA: Injury Control: A Guide to the Causes and Prevention of Trauma. Lexington, Massachusetts, Lexington Books, 1985. 5. Baker SP, O'Neill B, Karpf RS: The Injury Fact Book. Lexington, Massachusetts, Lexington Books, 1985. 6. Robertson LS: Injuries: Causes, Control Strategies, and Public Policy. Lexington, Lex M ington Books, 1983. 7. Viano DC: Cause and control of automotive trauma. Bull N Y Acad Med 1988;64:376-421. 8. Waller JA: Prevention of premature death and disability due to injury, in Last JM (ed): Public Health and Preventive Medicine ed 12. Norwalk, Connecticut, Appleton-CenturyCrofts, 1986. 9. Haddon W Jr: The changing approach to the epidemiology prevention, and amelioration of trauma: The transition to approaches etiologically rather then descriptively based. Am J Public Health 1968;58:1431-1438. 10. Haddon W Jr: A logical framework for categorizing highway safety phenomena and activity. ] Trauma 1972;12:193-207. 11. Bull JP: A strategy for injury prevention. Tex Med 1983;79:51-54. 12. Channell S: West Virginia State EM8. Personal communication. 13. Mueller BA, Rivara FP, Bergman AB: Factors associated with pedestrian-vehicle collision injuries and fatalities. West J Med 1987;146: 243-245. 14. Withers BF, Baker, SP: Epidemiology and prevention of injuries. Emerg Med Cliu North Am 1984;2:701-716. 15. Haddon W Jr: Energy damage and the ten countermeasure strategies. J Trauma 1973;13: 321-331. 16. Haddon W Jr, Baker SP: Injury control, in Clark D, MacMahon B (eds}: Preventive and Corr~munity Medicine, ed 2. Boston, Little, Brown and Co, 1982, p 1-45. 17. Haddon W Jr: Strategy in preventive medicine: Active versus passive approaches to reducing human wastage. J Trauma 1974;14:353-354. 18. Kraus JF~ Riggins RS, Franti CE: Some epidemiologic features of motorcycle collision injuries, I: Introduction, methods, and factors associated with incidence. A m J Epidemiology 1975;102:74-97. 19. Robertson LA, Zador P: Driver education and fatal crash involvement of teenaged drivers. A m J Public Health 1978;68:959-965. 20. Status report: Two studies question value of motorcycle licensing program. Insurance Institute for Highway Safety, August 13, 1988;23: 1-6. 21. Robertson LS: Crash involvement of teenaged drivers when driver education is eliminated from the high school. A m J Public Health 1980; 70:599-603. 22. Ross HL, Gonzales P: Effects of license revocation in drunk driving offenders. Accid Anal Prey 1988;20:379-391.
76/129
INJURY CONTROL Martinez
23. Richards JW, Fischer P, Conner FG: The warnings on cigarette packages are ineffective. JAMA 1989;261:45.
Motorcycle Helmet Use in Relation to Legal Requirements. Washington DC, Insurance Institute for Highway Safety, t979.
24. Baker SP: On lobbies, liberty, and the public good. A m J Public Health 1980;70:573-575.25.
28. Nelson GD, Moffet PA: Safety belt promotion: Theory and practice. Accid Anal Prey 1988;20:27-38.
25. Air Bags: A Chronological History of Delay. Washington, DC, Insurance Institute for Highway Safety, 198I.
29. Pace BW, Thailer R, Kuratkowski TG: New York state mandatory seatbelt use law: Patterns of seatbeh use before and after legislation. J Trauma 1986;26:1031-1033.
26. Baker SP: Injuries: The neglected epidemic: Stone lecture, 1985 American Trauma Society meeting. J Trauma 1987;27:343-348. 27. Williams AF, Ginsburg MJ, Burchmen PF:
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30. Williams AF, Lund AK: Seatbelt law use and occupant crashing protection in the United States. A m J Public Health 1986;76:1438-1441.
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31. Perkins RJ: Perspective on the public good. Am J Public Health 1981;71:294-295. 32. Baker SP, Teret SP: Freedom and protection: A balancing of interests. A m J Public Health 1981;71:295-297. 33. Robertson LS, Haddon W: The buzzer-light reminder system and safety belt use. A m J Public Health 1974;64:814-815. 34. Campbell D% Ross HL: The Connecticut crackdown on speeding: Time-series data in quasi-experimental analysis. Law and Society Review 1969;3:33-53.
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