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Wilderness injuries and illnesses
ORIGINAL CONTRIBUTION
wilderness, illness and injury
Wilderness Injuriesand Illnesses From the Department of
Douglas A Gentile, MD*
Study objective:T0determine injury and illness patterns and occur-
Surgery, Division of Emergency
John A Morris, MO t
rence rates during wilderness recreation.
Medicine, Stanford University School of Medicine, Stanford,
Tod Schimelpfenig, MS ~
California;* Department of Surgery, Division of Trauma, Vanderbilt University School of Medicine, Nashville, Tennessee;t and National Outdoor Leadership School, Lander, Wyoming/: Receivedfor publication" November22, 1991. Acceptedfor publication January 22, 1992.
Sue M Bass, ScM t Paul S Auerbach, MD, FACEP*
Design: Prospective injury and illness surveillance study. Setting:
Wilderness areas throughout the Western hemisphere.
Type of participants: All students and instructors on National Outdoor Leadership School courses over a five-year period. Main results: A single fatality occurred, resulting in a death rate of 0.28 per 100,000 person-days of exposure. Injuries occurred at a rate of 2.3 per 1,000 person-days of exposure. Sprains and strains and soft tissue injuries accounted for 80% of the injuries. The illness rate was 1.5 per 1,000 person-days of exposure. Sixty percent of illnesses were due to nonspecific viral illnesses or diarrhea; hygiene appeared to have a significant impact on the incidence of these illnesses. Thirty-nine percent of the injuries and illnesses required evacuation (1.5 per 1,000 person-days of exposure). Conclusion: The injury and illness patterns indicate that wilderness medical efforts should concentrate on wilderness hygiene and management of musculoskeletal injuries and soft tissue wounds. The data also indicate that wilderness activities can be conducted relatively safely, but the decision to participate should be individualized, with an understanding of risks versus benefits. [Gentile OA, Morris JA, Schimelpfenig T, Bass SM, Auerbach PS: Wilderness injuries and illnesses. Ann EmergMedJuly 1992;21:853-861 .]
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ANNALS OF EMERGENCY MEDICINE 21:7 JULY 1992
WILDERNESS Gentile et al
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INTRODUCTION The past two decades have seen a surge of interest in wilderness recreational activities. Mthough precise numbers of participants are not available, a survey by the National Sporting Goods Association determined that more than 9 million Americans participated in backpacking/wilderness camping in 1988.1 The American Alpine Club estimates that more than 100,000 active rock and mountain climbers in the United States spend between 1 and 2 million person-days per year hiking and climbing in the mountains. 2 Millions of other people engage each year in such wilderness activities as horsepacking, white water kayaking, and Nordic skiing. Despite the public health considerations attendant to the growing n u m b e r of participants in wilderness recreation, little validated information is available on the epidemiology of wilderness injuries and illnesses. Data on populations at risk, types and severity of incidents, occurrence rates, exposure history, skill level of participants, and comparative risks of different wilderness activities are fundamental to developing effective strategies for prevention and managemeni of wilderness injuries and illnesses. This information is critical if physicians are to rationally advise individuals or groups contemplating wilderness recreation. This study describes the types and severities of injuries and illnesses encountered during a variety of wilderness activities, establishes incidence rates, and looks at injury and illness patterns. MATERIALS AND METHODS From September 1984 to September 1989, a comprehensive safety data base was compiled from all National Outdoor Leadership School wilderness courses conducted in the Western hemisphere. The National Outdoor Leadership School is an educational corporation and licensed private school h e a d q u a r t e r e d in Lander, Wyoming, with North American branches in Alaska, Washington, and Mexico. The school provides outdoor leadership training in remote environments (Figure 1) and teaches fundamental and advanced Figure 1. Locations f o r courses
Wyoming Wind River Range Absaroka Range Beartooth Range Teton Range Alaska Denali National Park Gates of the Arctic National Park Brooks Range Arctic National Wildlife Refuge Alaska Range Chugach Range Talkeetna Range Prince William Sound
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Desert Southwest Gila Wilderness Chihauhaun Desert Canyonlands,Utah Sonoran Desert Carlsbad Caverns Rio Grande River Washington Waddington Range Cascade Range Olympic Mountains Foreign Sites Waddington Range, British Columbia, Canada Aconcagua, Chile/Argentina BaD Peninsula, Mexico
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skills to individuals for a wide a r r a y of wilderness activities. Courses range in length from two weeks to three months. 1 All courses emphasize a core curriculum of minimumimpact camping, backcountry travel techniques, outdoor living skills, wilderness safety, environmental awareness, and expedition dynamics. Individual courses or course sections focus on a specific wilderness activity (Figure 2). Nordic skiing includes advanced Nordic downhill techniques such as linked telemark turns. Rock climbing differs from mountaineering in emphasis, concentrating on technical rock climbing skills. Expedition mountaineering involves ascents of Mount Waddington in British Columbia (4,041 m or 13,260 ft), Denali (Mount McKinley) in Alaska (6,193 m or 20,320 ft), and Aconcagua in Chile, the highest mountain in the Western hemisphere (6,960 m or 22,834 ft). This study separately considered mountaineering courses with climbing primarily on snow and ice, because previous research indicated that snow and ice climbing might be more hazardous. 3 Incidents were entered prospectively into the data base if they prevented the individual from participating in normal course activities for 12 hours or longer. Incidents were categorized as injuries, illnesses, or nonmedical events. Nonmedical incidents included behavioral and motivational problems and personal or family difficulties unrelated to course activities. One of the course instructors recorded detailed information regarding the incident in the field, and the information was subsequently entered into a computerized data base (R-base"~). When an injured or ill participant was examined by a physician, we obtained a medical r e p o r t from which a diagnosis was recorded. F o r incidents not requiring physician involvement, injury and illness diagnoses were deduced from the instructor descriptions. Because courses varied in length and some individuals, particularly instructors, participated in more than one course, incident rates were calculated p e r 1,000 person-days of exposure. We calculated injury and illness rates by age for students only. Most of the instructors were in the 20- to 29year age group; including them would have had an impact on the rates for that age group out of proportion to the other groups. In addition, because many instructors participated in courses in multiple years, classifying them by age presented problems in determining denominator totals. In the injury category, "sprain/strain/tendon" included all muscle strains and ligamentous and tendon injuries. "Soft tissue injuries" included contusions, abrasions, and lacerations. "Immersion foot" (trench foot) referred to neurovasFigure 2. Course activities
Backpacking Nordic skiing White water paddling Sea kayaking/sailing Caving
Horsepacking Rock climbing Expedition mountaineering Mountaineering Mountaineering--snow/ice
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cular damage occurring after prolonged exposure of wet feet to temperatures of 0 to 10 C. This study defined "anaphylaxis" as a systemic allergic reaction severe enough to require p a r e n t e r a l administration of epinephrine. " R e s p i r a t o r y " illnesses included asthma, severe bronchitis, and pneumonia. The wide a r r a y of injuries and illnesses encountered made using an objective severity scale problematic. However, the need for evacuation provided a general measure of incident severity and was particularly pertinent to wilderness activities. Course instructors made the decision to evacuate an individual based on the actual or projected inability of the victim to continue with normal course activities after receiving medical care in the field. If individuals were unable to travel under their own power (assisted evacuations), an increased grade of severity was inferred. All instructors complete the National Outdoor Leadership School instructor course, which includes wilderness first aid and search and rescue skills. Instructors are required to have first responder certification; 40% have emergency medical technic.Jan certification. Instructors c a r r y a comprehensive first aid kit and evacuation equipment on all courses. Incidence rates were compared using the Z 2 test for R by C contingency tables. 4 Ninety-five percent confidence intervals (CIs) were calculated for population proportions. Trends in incidence with increasing age were tested with the X2 test for trend in binomial proportions.4 RESULTS S t u d y P 0 p u I a t i 0 n The National Outdoor Leadership School safety data base encompassed five years and included 10,977 course participants. Table 1 outlines the demographics and depicts the ineident distributions. During the five-year period, students and instruetors participated in 358,210 person-days of wilderness activities, incurring an injury rate of 2.3 per 1,000 person-days of exposure (CI, 2.2 to 2.5), an illness rate of 1.5 (CI, 1.4 to 1.6), and a nonmedical incident
rate of 0.3 (CI, 0.3 to 0.4). There was one fatality resulting in a mortality rate of 0.28 per 100,000 person-days of exposure. Students became ill and injured more often than did instructors (P < .001). Overall, women suffered higher injury and illness rates than did men (P < .001), although the rates for female instructors did not differ significantly from the rates for male instructors (illness rate: male instructors, 0.62; female instructors, 0.51; injury rate: male instructors, 1.37; female instructors, 1.86). Although the injury incidence rose for students more than 40 years old, the increase did not reach statistical significance. However, there was a significant decline in the illness incidence with increasing age (P < .05). I n j 0 r i e s Table 2 shows the types of injuries sustained and the number of victims who required evacuation. The 839 wilderness injuries included 443 sprain/strain/tendon injuries (53%), 226 soft tissue injuries (27%), and 39 fractures or dislocations (4.6%). Table 3 shows the most common types of injuries for each anatomic location. Most injuries involved the lower extremities ( 56% ), although one-half of the fractures and dislocations involved the u p p e r extremities. More than 50% of dislocations involved the shoulder, and 64% of sprain/strain/tendon injuries involved the knee or ankle. I l l n e s s e s Illnesses caused 529 incidents (36%) and 181 evacuations (28%). Nonspecific viral syndromes and d i a r r h e a accounted for 60% of the illnesses (Table 4). Of 23 cases of acute mountain sickness, three individuals developed potentially life-threatening complications. Two demonstrated symptoms of high-altitude pulmonary edema; both remained ambulatory during evacuation. One individual developed high-altitude cerebral edema near the summit of Aconcagua (6, 644 m, 21,800 ft). He was evacuated successfully by members of the climbing party. Of three cases of anaphylaxis, one resulted from a bee sting in an individual with known hymenoptera sensitivity;
Table !. Demographics and incidence rates Person-Days of Exposure Total 358,210 Sex Male 242,181 Female 116,029 Status Student 293,904 Instructor 64,306 Ageof Students 10 to 19 117,712 20 to 29 152,767 30 to 39 17,413 40 to 49 4,703 49 and up 1,309 * All ratesare per 1,000person-daysof exposure.
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Course Participants
Injury (Rate, CI)*
Illness (Rate, C|)*
10,977
839 (2.3, 2.2 to 2.5)
529 (1,5, 1.4 to 1.6)
111 (0.3, 0.3 to 0.4)
7,407 3,570
505 (2.1, 1.9 to 2.3) 334 (2.9, 2.6 to 3.2)
301 (1,2, 1.1 to 1.4) 228 (2.0, 1.7 to 2.2)
76 (0.3, 0.2 to 0.4) 35 (0.3, 0.3 to 0.4)
8,094 2,883
742 (2.5, 2.3 to 2.7) 97 (1.5, 1.2 to 1.8)
491 (1,7, 1.5 to 1.8) 38 (0,6, 0.4 to 0.8)
110 (0.4, 0.3 to 0.4) 1 (0.01)
3,238 3,797 744 242 73
317 (2.7, 2.4 to 3.0) 366 (2.4, 2.2 to 2.6) 38 (2.2, 1.5 to 2.9) 16 (3.4, 1.7 to 5.1) 5 (3.8, 0.5 to 7.2)
211 (1.8, 1.6 to 2.0)
42 (0.4, 0.2 to 0.4)
253 (1.7, 1.5 to 1.9) 22 (1.3, 0.7 to 1.8) 5 (1.1, 0.1 to 2.0) 0
45 (0.3, 0.2 to 0.4) 19 (1.1, 0.6 to 1.6) 4 (0.9, 0.07 to 1.7) 0
Nonmedical (Rate, CI)*
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WILDERNESS Gentile et al
the other two were of unknown etiology. All three cases responded to epinephrine administered in the field. Of five cases of abdominal pain, three were evaluated by a physician after evacuation. The diagnoses included peptic ulcer disease, u r i n a r y tract infection, and nonspecific abdominal pain that resolved after 24 hours in the hospital. Table 5 lists the illness type by b r a n c h headquarter. The Mexico and Wyoming branches r e p o r t e d significantly higher illness rates than did the Alaska or Washington branches (P < .001). Viral syndromes occurred more frequently in the Mexico b r a n c h (P < .001), and d i a r r h e a afflicted more participants on courses from Mexico and Wyoming (P < .001). Alaska reported significantly fewer cases of d i a r r h e a than did the other branches (P < .001). Field experience suggested that younger students were less likely to adhere to wilderness hygiene guidelines. To see if hygiene practices correlated with the incidence of viral syndromes and d i a r r h e a , we combined the two categories and compared the rate by status and age. The rate for viral and diarrheal illnesses combined for students was significantly higher than for instructors (students, 1.0 p e r 1,000 persondays of exposure; CI, 0.9 to 1.1; instructors, 0.4; CI, 0.2 to 0.5; P < .001), and the rate was inversely related to age (P < .01). Of 1,479 incidents, 634 (43%) required evacuation (Table 6). Students required evacuation more often than did instructors (P < .001), and women needed evacuation more often than did men (P < .001). Only 29 victims (2%) were unable to evacuate u n d e r their own power (assisted evacuations). Twenty-four of the assisted evacuations were for injuries: sprains and strains (12), fractures/dislocations (ten), soft tissue injuries (two), and other (one). Five individuals required assisted evacuation for an illness: high-altitude illness (two), abdominal pain (one), and nonspecified illnesses (two). History of Injury or I l l n e s s A history of the specific injury or illness was obtained at the time of the incident for 16% of injuries and 10.5% of illnesses, o f those individuals who gave a history of the incident, 93% had listed the history on the precourse medical form. A history existed for 25% of sprain/strain/tendon injuries and 13% of fractures. Ten percent of persons developing symptoms of high-altitude illness had a history of the illness. Table 2. Type of injury (column~rowpercentage) Injury Total Sprains/strains Soft tissue Wound infections Fractures Immersion foot Burns Dislocations Frostbite Blisters Other
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Evacuations (%)
839 (100/100) 443 (53/100) 226 (27/100) 36 (4/100)
348 ( 100/41) 183 (53/41) 69 (20/30) 20 (6/55) 25 (7/96) 12(3/52) 4 (1/22) 10 (3/77) 1 (0.4/12) 2 (0.6/29) 22 (6/56)
23(3/100) 18 (2/100) 13 (1/100) 8 (1/100) 7 (1/100) 39 (5/100)
Table 3. Anatomic location of injuries Location Foot Ankle Lower leg Knee Thigh
Hip
Total (%)
26 (3/100)
W i I d e r n e s s A c t i v i t i e s Because courses or course sections focused on a specific wilderness activity, we were able to compare injury, illness, and evacuation rates by major course activity (Table 7; Figure 3), In this study, backpacking was the most commonly performed wilderness activity (43% of total person-days of exposure) and is generally considered a low-risk activity. We therefore used the injury, illness, and evacuation rates incurred on backpacking courses as a baseline for comparing the other activities. Both white water paddling and Nordic skiing had significantly higher injury rates than did backpacking courses (P < .001), and horsepacking courses generated significantly fewer injuries (P < .001). Rock climbing, a wilderness activity traditionally associated with high risk, also generated lower injury rates than did backpacking (P < .05). Illness rates were significantly higher for rock climbing (P < .001), Nordic skiing (P < .001), white water paddling (P < .001), and caving courses (P < .001). Although the pattern of activity-specific injury rates for students conformed to that of the group as a whole, the pattern for instructors differed dramatically (Figure 4). Caving incurred the highest instructor injury rate and was the only activity with a significantly higher rate than backpacking (P < .05). Instructor injury rates for Nordic skiing and white water paddling were comparable with the rate for b a c k p a c k ing. On rock climbing courses, instructors sustained a higher injury rate (2.9 p e r 1,000 person-days of exposure; CI, 1.0 to 4.8) than did students (1.4 per 1,000 person-days of exposure; CI, 0.8 to 2.0) with the difference approaching statistical significance (P = .052). Although instructors also sustained higher injury rates on caving courses, the difference was not significant (P = .205).
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Assisted Evacuations(%) 24 (100/3) 12 (50/3) 2 (8/1) 0 8 (33/31) 0. 0 2 (8/15) 0 0 0
Pelvis Lower back Upper back Neck Face Head Shoulder Upper arm Elbow Forearm Wrist Hand Chest Missing
Sprain/ Strain
Soft Tissue
Fracture/ Dislocation
Other
Total
13 143 5 139 6 5 1 41 25 7 3 0 21 1 1 1 16 9 2 4
32 8 16 19 9 4 6 5 3 0 37 13 2 1 4 4 0 55 2 6
3 8 0 1 1 2 0 0 0 0 2 0 7 0 2 1 2 8 1 1
43 4 8 1 4 0 2 4 0 0 27 4 1 2 0 0 0 15 0 26
91 163 29 160 20 11 9 50 28 7 69 17 31 4 7 6 18 87 5 37
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WILDERNESS Gentile et al
DISCUSSION Wilderness is defined as a region uncultivated and uninhabited by human beings. 5 Because wilderness activities take place in remote areas distant from usual sources of medical care, a much higher level of medical seE-sufficiency is required than with most other recreational activities. When professional medical care is available, rescue and treatment are made more difficult by the remote setting. Knowledge of likely problems may prepare both lay and medical personnel to approach Victims with greater speed and better equipment. The injury and illness patterns described in this study have important implications for all wilderness recreationists. Eighty percent Of injuries fell into the categorie s of soft tissue injuries and sprain/strain/tendon. Clearly, essential medical skills for wilderness recreation include wound management, early recognition and intervention for overuse injuries, and treatment of sprains and strains to prevent further injury and potentially allow continued participation. Dealing effectively with these problems in remote environments often requires approaches and equipment different from those used in health care facilities. Diarrhea was the most common illness (30%), followed closely by nonspecific viral syndromes (30%). As discussed below, data from this study suggest that strict hygien e and water disinfection practices may reduce the incidence of diarrheal and viral illnesses during wilderness recreation. Acute mountain sickness, hypothermia, and heat illness occurred infrequently despite considerable exposure to harsh environments , and most victims did not require evacuation. These entities and certainly their severe manifestations can be largely prevented with p r o p e r equipment (hypothermia), acclimatization (acute mountain sickness and heat illness), and close attention to early signs and symptoms. All participants in wilderness recreation should
Table 4. Types of illnesses and related evacuations (column~row percentage) Illness Total Virus Oiarrhea Udnarytract infection Respiratory Allergy Anaphylaxis Colorado tick fever Acute mountain sickness Abdominal pain Gynecologic Cardiac Heat i!lness Hypothermia Ear infections Dental Dermatitis Other
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Total (%) 529 152 (30/100) 161 (30/100) 11 (2/100) 7 (1/100) 11 (2/100) 3 (1/100) 2 (1/100) 23 (4/!00) 5 (1/100 17 (3/100 3 (I/100 8 (1/100 18 (3/100 15 (3/100 18 (3/1001 20 (4/1001 55 (10/10(]
Evacuation (%) 18i (100/34) 51 (28/33) 31 (17/19) 4 (2/36) 4 (2/57) 4 (2/36) 2 (!/67) 2 (1/100) 9 (5/39) 3 (2/60) 6 (3/35) 3 (2/100) 1 (1/12) 1 (i/5) 5 (3/33) 10 (5/56) 3 (2/15) 42 (23/76)
Assisted Evacuation (%) 5(100/1) 0 0 0 0 0 0 0 2 (40/9) 1 (20/20) 0 0 0 o 0 0 0 2 (40/4)
be familiar with the prevention and early recognition and management of these illnesses. Studying structured courses m wilderness recreation allowed us to accurately define a population at H s k and gather precise exposure information for a variety of wilderness activities. The structured course format also provided a consistent and realistic wilderness experience. Courses took place in remote wilderness environments, and all participants functioned as active team members, taking responsibility for their own equipment and sharing in camping, cooking, and other course tasks. However, a limitation of studying structured wilderness courses is the inability to generalize the incident rates to other populations, particularly those participating in wilderness recreational activities without the supervision of trained instructors. Although task demands were high for many activities (expedition mountaineering, rock climbing, white water paddling), the courses emphasized mastery of wilderness skills through a progressive, graduated program to minimize injuries. Less-experienced individuals and groups, persons tempted to exceed their performance capability, or expeditions operating u n d e r extreme environmental conditions may suffer higher rates. The injury and illness rates in this study are notable, however, because they demonstrate that with proper safety procedures, training, and equipment, wilderness activities can be conducted safely. We defined incidents by time lost from participation to standardize inclusion criteria and to facilitate uniform and complete data collection in the field. This definition had the a d d e d advantage of focusing on incidents most likely to affect performance, while eliminating minor complaints. However, this type of operational definition introduces some biases. First, incidents may be activity specific. F o r exampie, a h a n d injury that prevents participation in rock climbing may not interfere with backpacking. Second, the definition assumes that all individuals respond to an incident in a similar manner; in fact, one individual may participate with a given injury or illness whereas another will not. In discussions with instructors, lack of motivation was felt to be a frequent contributor to time lost from participation.
Table 5. National Outdoor Leadership School illnesses by brunch Alaska (Rate, CI)*
Mexico (Rate, CI)*
Washington (Rate, CI)*
Wyoming (Rate, Cl)*
Person-days ofexposure Totalillnesses
541490 25,289 26,616 251,815 40 56 23 410 (0.7, 0.5 to 1.0) (2.2, 1.6 to 2.8)~ (0.9, 0.5 to 1.2) (1.6, 1.5 to 1.8)t Viral 14 24 8 106 (0.3, 0.! to 0.4) (0.9, 0.6 to 1.3)~ (0.3, 0.1 to 0.5) (0.4, 0.3 to 0.5) Diarrhea 2 13 6 140 (0.4) (0.5, 0.2 to 0.8) ~ (0.2, 0.004 to 0.4) ' (0.6, 0.5 to 0.6) t * All rates are per 1,000 person-days of exposure. P< .001.
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WILDERNESS Gentile et al
It was not surprising that students sustained higher injury, illness, and evacuation rates than did instructors. As a group, instructors are more skilled, experienced, and conditioned all qualities that would be expected to reduce incident rates. In fact, we suspect that the instructor incident and evacuation rates in this study a p p r o a c h the lowest achievable rates given current practices and technology. Although this study did not specifically examine reasons for the higher illness and injury rates observed in female students, several observations are worth noting. Although statistically significant, the practical implications of the higher incident rates for female participants are less clear; female participants suffered less than one additional injury or illness p e r 1,000 days of exposure. The fact that rates for female and male instructors did not differ significantly suggests that the difference among students might have been due to remediable factors such as conditioning. Alternatively, instructors might have been more inclined to enforce cessation of activities for female students who were injured or ill than fo.r male students. Although the National Outdoor Leadership School attempts to place a female instructor on every course, this is frequently not possible because of difficulties in recruiting female staff. We also cannot rule out subjective factors; male students may have been more motivated to continue p a r t i c i p a t i o n despite injury or illness. M 0 r t a I i t y The one fatality during this study deserves special comment. The incident occurred on a climb of Mount W a r r e n in the Wind River Range of Wyoming. A different route was chosen for descent, because it presented less hazard than the narrow and technically more difficult ascent route. As the students were being sequentially lowered over a steep section, a rock "the size of a watermelon" was dislodged, bounced out of the fall line, and struck a student waiting below. The victim was wearing an a p p r o v e d helmet and had moved well to the side of the descent fall line. He died from an i n t r a c e r e b r a l hemorrhage before he could be evacuated from the mountain. Both internal and external
inquiries into the death concluded that the route and equipment were a p p r o p r i a t e for the group and that correct safety procedures were adhered to throughout the climb. 6 Wilderness travel by definition involv~es the potential for encounters with n a t u r a l forces that are unpredictable and uncontrollable. Although many wilderness fatahties p r o b a b l y occur because obvious warning signs and safety procedures are ignored or because individuals choose to engage in extremely hazardous activities, some occur despite p r u d e n t precautions. Although the low mortality rate i n c u r r e d in this study will be acceptable to many individuals, participants should be fully informed regarding the risk of not only injury and illness but also death. Wilderness activities should not be promoted or advertised as risk free. | n j u r i e s Differences in injury definition, d a t a collection, and exposure time prevent direct comparison of injury rates from this study with those published for other recreational activities. Despite this limitation, studying rates for other activities does add an intuitive perspective to the wilderness injury rates. There were 7.6 injuries and 3.2 injury evacuations p e r 100 National Outdoor Leadership School participants. Reported injury rates for football range between 14.5 and 81 p e r 100 participants. 7 Gymnastics injuries range from 28 to 138 p e r 100 participants. 7 Unfortunately, calculating incidence rates by number of participants does not take into account differences in exposure time. Although athletic seasons may last three to five months, exposure is usually limited to a few hours p e r day. One recreational activity for which comparable exposure data exists is downhill skiing. Reported injury rates for downhill skiing range from 2.8 to 5.9 p e r 1,000 person-days of exposure versus 2.3 injuries p e r 1,000 person-days for National Outdoor Leadership School.7 Rock climbing and mountaineering are often regarded as high-risk activities. Climbing and mountaineering injury rates in this study, however, were lower than or the same as Table 7.
Activity-specifw incidents (all rates tested against backpacking for significance) Table 6.
Evacuations
Activity
Demographics Total Status Student Instuctor Sex Male Female Incident Type Injury Illness Nonmedical
illness (Rate, CI)*
Evacuations (Rate, CI)*
24,346
91 (3.7, 3.0 to 4.5)*
89 (3.7, 2.9 to 4.4)t
55 (2.3,1.7 to 2.9p
6.678
41 (6.1, 4.3 to 8.0)t
21 (3.1,1.8 to 4.5)*
24 (3.6, 2.2 to 5.0)t
74 (1.8,1.4 to 2.3)§ 37 (2.7,1.8 to 3.6) 5 (0.3, 0.04 to 0.6)t 370 (2.4, 2.2 to 2.6) 31 (1.6,1.1 to 2.2)
53 (1.3,1.0 to 1.7) 46 (3.4, 2.4 to 4.4}t 5 (0.3, 0.04 to 0.6)t 164 (1.1, 0.9 to 1.2) 54 (2.8, 2.1 to 3.6)t
26 (0.6, 0.4 to 0.9)t 33 (2.4,1.6 to 3.3)t 6 (0.3, 0.1 to 0.6)t 216 (1.4,1.2 to 1.6) 35 (1.8,1.2 to 2.4)
Incidents
1,479
634 (1.8,1.6 to 1.9)
29 (0.08, 0.05 to 0.1 )
1,343 136
570 (1.9,1.8 to 2.1 )t 64 (1.0, 0.8 to 1.2)
25 (0.08, 0.05 to 0.1) 4 (0.06, 0.001 to 0.1)
882 597
398 (1.6,1.5 to 1.8) 236 (2.0, 1.8 to 2.3) t
23 (0.09, 0.06 to 0.1) 6 (0.05, 0.001to 0.09)
Sea kayaking] sailing 40,005 Caving 13,566 Hersepacking 16,996 Backpacking 154,066 Rock climbing 19,038 Expedition mountaineering 7,566
24 (0.07, 0.04 to 0.09) 5 (0.01, 0.002 to 0.03) 0
Mountaineering 50,275 Snow/ice climbing 25,674 Missing
839 529 111
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Nordic skiin9 White water paddling
Injup/ (Rate. CI)*
Evacuations (Rate, CI)*
348 (1.0, 0.9 to 1.1 ) 181 (0.5, 0.4 to 0.6) 105 (0.3, 0.2 to 0.3)
* All rates are per 1,000 person-days of exposure. t p< .OOl.
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Assisted Evacuations (Rate, CI)*
Exposure Days
ANNALS OF EMERGENCY MEDICINE
11 (1.4, 0.6 to 2.3)
7 (0.9, 0.2 to 1.6)
6 (0.8, 0.2 to 1.4)
103 (2.1,1.7 to 2.4)
54 (1.1, 0.8 to 1.4)
78 (1.5,1.2 to 1.9)
57 (2.2,1.6 to 2.8) 19
21 (0.8, 0.5 to 1.2) 15
35 (1.4, 0.9 to 1.8) 15
* All ratesare per 1,000person-days of exposure. 1"P < .001; * P < .0t; § P < .05,
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WILDERNESS Gentile et al
injury rates for backpacking. Evacuation rates were also comparable, suggesting that i n j u r y severity did not differ significantly. The results indicate that learning these technically demanding wilderness skills need not entail excessive risk if appropriate attention is directed to training, equipment, and safety. The higher i n j u r y rate for instructors versus students on rock climbing courses may reflect an increased risk associated with leading muhipitch climbs. This hypothesis is being investigated. Until additional research is completed, we can only speculate as to why i n j u r y rates were significantly higher from Nordic skiing and white water paddling courses. It is interesting to note that despite the differences between the two activities, there are pertinent similarities. Both activities are technically demanding and, at times, conducted at high rates of speed, requiring rapid reaction times. Both use levers (skis and paddles), which serve to increase the forces applied to the most commonly injured h u m a n body parts. The fact that injury rates for instructors on these courses were not increased suggests that training and skill can compensate for the high demands of these activities. ] I I n e s s e s Viral syndromes and diarrhea accounted for 60% of the illnesses and 45% of the illness evacuations. We
suspect that some of these illnesses are hygiene related. Virtually all students in this study were from Western countries where sanitation is taken for granted: However, remote wilderness travel requires leaving behind modern sanitation and reliably disinfected tap water. Although surveys reveal widespread contamination of surface water in wilderness areas, 8 convincing students to maintain strict wilderness hygiene and water disinfection practices during a long Stay in apparently pristine wilderness areas is problematic. Data on illnesses by the National Outdoor Leadership School branch suggest a causal role for transmissible pathogens and hygiene in viral illnesses and diarrhea in the wilderness. The Alaska branch generated significantly lower rates of these illnesses than did the other branches. Alaska trip leaders enforce particularly strict cooking and camping hygiene practices because of the threat of grizzly bear attacks. The bear threat also provides strong motivation for students to adhere to hygiene guidelines. However, courses in Mexico, a high-risk area for traveler's illnesses, reported the highest total illness rate, with a particularly high rate of viral illnesses. Diarrhea was equally Figure 4.
Figure 3.
Instructor and student activity-specific injury rates (per 1,000 person-days of exposure)
Activity-specific injury and illness rates (per 1,000 person-days of exposure)
•
Backpacking
Injuries
Total Backpacking
Students
Illnesses
Instructors Skiing Skiing
White water paddling
White water I paddling
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Sailing/kayaking
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•
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Sailing/kayaking
Cavir~g
Caving
Horsepacking
Horsepacking
Rock climbing
Rock climbing
Expedition mountaineerin
Expedition mountaineerinc
Mountaineering
Mountaineering
Snow/ice climbing
I
: ~ ::': : iiiiiiiiiiiiiiii!iiii!iiiiiiUiiii~iiiiiiiii!iiiiiiiiiii~ii~j
Snow/ice climbing ~ii!iii~ii~ii~i~i~iiiliiii~i:i~i~i~@!iiiii~i~i~i~iiiii~i~i~iii~iiiiit
m
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7
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common during the Mexico and Wyoming courses. Most of the three-month semester courses are conducted out of the Wyoming branch; the length of the courses and the absence of overt risk factors add to the difficulty in maintaining hygiene standards among students. Field observations confirm deterioration in hygiene practices during longer courses. The decrease in illness rates with increasing age resulted primarily from lower rates for viral illnesses and d i a r r h e a in older age groups. Field observations strongly suggest that older individuals adhere t ° wilderness hygiene guidelines more closely. Confirming the link between wilderness hygiene and illnesses requires further study, but information on travelers' d i a r r h e a suggests that hygiene precautions may be effective in reducing the spread of transmissible pathogens .9 E v a c u a t i o u s Evacuation rates provide critical information on incident severity for wilderness activities. The need to evacuate an individual from a remote environment not only jeopardizes the objectives of the group but may place group members at increased risk. Mountain, white water, or ocean rescues are frequently hazardous for the rescuers as well as the victims. An incident severe enough to require evacuation will likely impair the victim's ability to carry a load or assist with other tasks. Even if a victim is able to leave the wilderness under his or her own power, safety generally dictates that the victim be accompanied by at least one other group member. Assisted evacuations place extreme demands on the entire group. Transporting a nonambulatory victim over wilderness terrain generally requires six to eight people p e r mile, multiplying the logistic Problems of food, shelter, and rest. Helicopter rescues are expensive and often dangerous. This study demonstrates that wilderness activities require evacuation with sufficient frequency (1.8 per 1,000 persondays of exposure) that the need must be anticipated. Evacuation plans should be formulated before embarking, and an itinerary should be recorded with someone who will recognize when a trip is overdue. A p p r o p r i a t e evacuation equipment should be included in the trip provisions. I n j u r y / i l l n e s s P r e v e n t i o n This study suggests several mechanisms for reducing wilderness injuries and illnesses and provides direction for further research. Two injury categories--sprain/strain/tendon and soft tissue i n j u r i e s - - a c c o u n t e d for 80% of the injuries and 72% of the injury evacuations in this study. Clearly, to effect a substantial reduction in wilderness injury rates, injury prevention strategies must focus on these two categories. A significant number of sprain/strain/tendon incidents represented r e c u r r e n t injuries. A history was confirmed for 25% of sprain/strain/tendon injuries and for 16% of all injuries and 11% of all illnesses. This raises the possibility of directing interventions at specific problems before and during the p r o g r a m to prevent recurrences. F o r example, recurrent ankle injuries might be prevented by high-top boots, an air splint, taping, or simply emphasizing trail awareness.
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Some preventive measures have already been implemented in National Outdoor Leadership School courses as a result of this study. In an attempt to improve hygiene and reduce the incidence of viral illnesses and diarrhea, instructors now use group cooking and wash stations on the Mexico and Wyoming semester courses. Biodegradable soap is issued to students, and in group cooking situations utensils are rinsed in a chlorine solution after each use. Course instructors are urged to be aggressive in education and oversight of hygiene and water disinfection practices. The impact of these changes is being investigated. The high injury rate (6.1 p e r 1,000 person-days of exposure) on white water courses p r o m p t e d a review of those activities. Most of the white water courses took place at the end (days 65 to 90) of a 95-day semester course. The itinerary for those courses was demanding and fast paced, and both the weather and water were often cold. Because fatigue may have been an important factor in the injury rate, the pace of the white water courses has been reduced and rest days have been built into the itinerary. Because 58% of the white water injuries were in the sprain/strain/tendon category, staff now receive training in early intervention of overuse injuries, and a program of stretching and warm-up exercises has been initiated. If close attention to fatigue factors and early field intervention for overuse syndromes is effective in lowering injury rates in white water courses, the same principles may be transferable to other activities.
CONCLUSION The low injury and illness rates in this study demonstrate that with a p p r o p r i a t e training and equipment, wilderness activities can be conducted safely. However, the isolated environment in which they occur requires anticipating and p r e p a r i n g for likely problems if effective early medical intervention is to be instituted. Determining the types and frequencies of wilderness injuries and illnesses should facilitate this process and will hopefully lead to successful preventive strategies. We believe that the challenges and attractions of wilderness activities outweigh the relatively low risks r e p o r t e d in this study. However, defining acceptable rates of injury and illness is of necessity an individual determination and depends on the perceived benefits of the activity versus the individual's willingness to take risks. This study, by beginning to delineate the risks of wilderness activities, provides essential information in allowing prospective participants to make informed decisions regarding participation.
REFERENCES 1. National Sporting 6oods Association: Sports Participation in 1988:Series L Mt Prospect, Illinois, NSGA. 2. Williamson JE (ed): Accidents in North American Mountaineering 1985.New York, American Alpine Club, 1985.
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3. Schussman LC, Lutz LJ, Shaw RR, et al: The epidemiology of mountaineering and rock climbing accidents. J Wilderness Med 1990;1:235-248.
Address for reprints: Douglas A Gentile, MD, Emergency Department, Stanford University Hospital, 300 Pasteur Drive, Stanford. California 94305.
4. Rosner B: FundamentalsofBiostatistics, ed 2. Boston, Duxbury Press, 1986. 5. Mish FC (ed): Webster's Ninth New Collegiate Dictionary. Springfield, Massachusetts, Merriam-Webster, 1983. 6. Williamson JE (ed): Accidents in North American Mountaineering 1990.New York, American Alpine Club, 1990. 7. Kraus JF, Conroy C: Mortality and morbidity from injuries in sports and recreation. Annu Rev Public Health 1984;5:163-192. 8. Backer HD: Field water disinfection, in Auerbach PS, Geehr EC (eds): Management of Wilderness and Environmental Emergencies. St Louis, CV M osby Co, 1989, p 805-827. g. Kozicki M, Steffen R, Sher M: "Boil it, cook it, peel it, or forget it": Does this rule prevent travelers' diarrhoea? IntJ Epidemio11985;14:169-172.
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wilderness, illness and injury
Wilderness Injuriesand Illnesses From the Department of
Douglas A Gentile, MD*
Study objective:T0determine injury and illness patterns and occur-
Surgery, Division of Emergency
John A Morris, MO t
rence rates during wilderness recreation.
Medicine, Stanford University School of Medicine, Stanford,
Tod Schimelpfenig, MS ~
California;* Department of Surgery, Division of Trauma, Vanderbilt University School of Medicine, Nashville, Tennessee;t and National Outdoor Leadership School, Lander, Wyoming/: Receivedfor publication" November22, 1991. Acceptedfor publication January 22, 1992.
Sue M Bass, ScM t Paul S Auerbach, MD, FACEP*
Design: Prospective injury and illness surveillance study. Setting:
Wilderness areas throughout the Western hemisphere.
Type of participants: All students and instructors on National Outdoor Leadership School courses over a five-year period. Main results: A single fatality occurred, resulting in a death rate of 0.28 per 100,000 person-days of exposure. Injuries occurred at a rate of 2.3 per 1,000 person-days of exposure. Sprains and strains and soft tissue injuries accounted for 80% of the injuries. The illness rate was 1.5 per 1,000 person-days of exposure. Sixty percent of illnesses were due to nonspecific viral illnesses or diarrhea; hygiene appeared to have a significant impact on the incidence of these illnesses. Thirty-nine percent of the injuries and illnesses required evacuation (1.5 per 1,000 person-days of exposure). Conclusion: The injury and illness patterns indicate that wilderness medical efforts should concentrate on wilderness hygiene and management of musculoskeletal injuries and soft tissue wounds. The data also indicate that wilderness activities can be conducted relatively safely, but the decision to participate should be individualized, with an understanding of risks versus benefits. [Gentile OA, Morris JA, Schimelpfenig T, Bass SM, Auerbach PS: Wilderness injuries and illnesses. Ann EmergMedJuly 1992;21:853-861 .]
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i
INTRODUCTION The past two decades have seen a surge of interest in wilderness recreational activities. Mthough precise numbers of participants are not available, a survey by the National Sporting Goods Association determined that more than 9 million Americans participated in backpacking/wilderness camping in 1988.1 The American Alpine Club estimates that more than 100,000 active rock and mountain climbers in the United States spend between 1 and 2 million person-days per year hiking and climbing in the mountains. 2 Millions of other people engage each year in such wilderness activities as horsepacking, white water kayaking, and Nordic skiing. Despite the public health considerations attendant to the growing n u m b e r of participants in wilderness recreation, little validated information is available on the epidemiology of wilderness injuries and illnesses. Data on populations at risk, types and severity of incidents, occurrence rates, exposure history, skill level of participants, and comparative risks of different wilderness activities are fundamental to developing effective strategies for prevention and managemeni of wilderness injuries and illnesses. This information is critical if physicians are to rationally advise individuals or groups contemplating wilderness recreation. This study describes the types and severities of injuries and illnesses encountered during a variety of wilderness activities, establishes incidence rates, and looks at injury and illness patterns. MATERIALS AND METHODS From September 1984 to September 1989, a comprehensive safety data base was compiled from all National Outdoor Leadership School wilderness courses conducted in the Western hemisphere. The National Outdoor Leadership School is an educational corporation and licensed private school h e a d q u a r t e r e d in Lander, Wyoming, with North American branches in Alaska, Washington, and Mexico. The school provides outdoor leadership training in remote environments (Figure 1) and teaches fundamental and advanced Figure 1. Locations f o r courses
Wyoming Wind River Range Absaroka Range Beartooth Range Teton Range Alaska Denali National Park Gates of the Arctic National Park Brooks Range Arctic National Wildlife Refuge Alaska Range Chugach Range Talkeetna Range Prince William Sound
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Desert Southwest Gila Wilderness Chihauhaun Desert Canyonlands,Utah Sonoran Desert Carlsbad Caverns Rio Grande River Washington Waddington Range Cascade Range Olympic Mountains Foreign Sites Waddington Range, British Columbia, Canada Aconcagua, Chile/Argentina BaD Peninsula, Mexico
ANNALS OF EMERGENCY MEDICINE
skills to individuals for a wide a r r a y of wilderness activities. Courses range in length from two weeks to three months. 1 All courses emphasize a core curriculum of minimumimpact camping, backcountry travel techniques, outdoor living skills, wilderness safety, environmental awareness, and expedition dynamics. Individual courses or course sections focus on a specific wilderness activity (Figure 2). Nordic skiing includes advanced Nordic downhill techniques such as linked telemark turns. Rock climbing differs from mountaineering in emphasis, concentrating on technical rock climbing skills. Expedition mountaineering involves ascents of Mount Waddington in British Columbia (4,041 m or 13,260 ft), Denali (Mount McKinley) in Alaska (6,193 m or 20,320 ft), and Aconcagua in Chile, the highest mountain in the Western hemisphere (6,960 m or 22,834 ft). This study separately considered mountaineering courses with climbing primarily on snow and ice, because previous research indicated that snow and ice climbing might be more hazardous. 3 Incidents were entered prospectively into the data base if they prevented the individual from participating in normal course activities for 12 hours or longer. Incidents were categorized as injuries, illnesses, or nonmedical events. Nonmedical incidents included behavioral and motivational problems and personal or family difficulties unrelated to course activities. One of the course instructors recorded detailed information regarding the incident in the field, and the information was subsequently entered into a computerized data base (R-base"~). When an injured or ill participant was examined by a physician, we obtained a medical r e p o r t from which a diagnosis was recorded. F o r incidents not requiring physician involvement, injury and illness diagnoses were deduced from the instructor descriptions. Because courses varied in length and some individuals, particularly instructors, participated in more than one course, incident rates were calculated p e r 1,000 person-days of exposure. We calculated injury and illness rates by age for students only. Most of the instructors were in the 20- to 29year age group; including them would have had an impact on the rates for that age group out of proportion to the other groups. In addition, because many instructors participated in courses in multiple years, classifying them by age presented problems in determining denominator totals. In the injury category, "sprain/strain/tendon" included all muscle strains and ligamentous and tendon injuries. "Soft tissue injuries" included contusions, abrasions, and lacerations. "Immersion foot" (trench foot) referred to neurovasFigure 2. Course activities
Backpacking Nordic skiing White water paddling Sea kayaking/sailing Caving
Horsepacking Rock climbing Expedition mountaineering Mountaineering Mountaineering--snow/ice
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cular damage occurring after prolonged exposure of wet feet to temperatures of 0 to 10 C. This study defined "anaphylaxis" as a systemic allergic reaction severe enough to require p a r e n t e r a l administration of epinephrine. " R e s p i r a t o r y " illnesses included asthma, severe bronchitis, and pneumonia. The wide a r r a y of injuries and illnesses encountered made using an objective severity scale problematic. However, the need for evacuation provided a general measure of incident severity and was particularly pertinent to wilderness activities. Course instructors made the decision to evacuate an individual based on the actual or projected inability of the victim to continue with normal course activities after receiving medical care in the field. If individuals were unable to travel under their own power (assisted evacuations), an increased grade of severity was inferred. All instructors complete the National Outdoor Leadership School instructor course, which includes wilderness first aid and search and rescue skills. Instructors are required to have first responder certification; 40% have emergency medical technic.Jan certification. Instructors c a r r y a comprehensive first aid kit and evacuation equipment on all courses. Incidence rates were compared using the Z 2 test for R by C contingency tables. 4 Ninety-five percent confidence intervals (CIs) were calculated for population proportions. Trends in incidence with increasing age were tested with the X2 test for trend in binomial proportions.4 RESULTS S t u d y P 0 p u I a t i 0 n The National Outdoor Leadership School safety data base encompassed five years and included 10,977 course participants. Table 1 outlines the demographics and depicts the ineident distributions. During the five-year period, students and instruetors participated in 358,210 person-days of wilderness activities, incurring an injury rate of 2.3 per 1,000 person-days of exposure (CI, 2.2 to 2.5), an illness rate of 1.5 (CI, 1.4 to 1.6), and a nonmedical incident
rate of 0.3 (CI, 0.3 to 0.4). There was one fatality resulting in a mortality rate of 0.28 per 100,000 person-days of exposure. Students became ill and injured more often than did instructors (P < .001). Overall, women suffered higher injury and illness rates than did men (P < .001), although the rates for female instructors did not differ significantly from the rates for male instructors (illness rate: male instructors, 0.62; female instructors, 0.51; injury rate: male instructors, 1.37; female instructors, 1.86). Although the injury incidence rose for students more than 40 years old, the increase did not reach statistical significance. However, there was a significant decline in the illness incidence with increasing age (P < .05). I n j 0 r i e s Table 2 shows the types of injuries sustained and the number of victims who required evacuation. The 839 wilderness injuries included 443 sprain/strain/tendon injuries (53%), 226 soft tissue injuries (27%), and 39 fractures or dislocations (4.6%). Table 3 shows the most common types of injuries for each anatomic location. Most injuries involved the lower extremities ( 56% ), although one-half of the fractures and dislocations involved the u p p e r extremities. More than 50% of dislocations involved the shoulder, and 64% of sprain/strain/tendon injuries involved the knee or ankle. I l l n e s s e s Illnesses caused 529 incidents (36%) and 181 evacuations (28%). Nonspecific viral syndromes and d i a r r h e a accounted for 60% of the illnesses (Table 4). Of 23 cases of acute mountain sickness, three individuals developed potentially life-threatening complications. Two demonstrated symptoms of high-altitude pulmonary edema; both remained ambulatory during evacuation. One individual developed high-altitude cerebral edema near the summit of Aconcagua (6, 644 m, 21,800 ft). He was evacuated successfully by members of the climbing party. Of three cases of anaphylaxis, one resulted from a bee sting in an individual with known hymenoptera sensitivity;
Table !. Demographics and incidence rates Person-Days of Exposure Total 358,210 Sex Male 242,181 Female 116,029 Status Student 293,904 Instructor 64,306 Ageof Students 10 to 19 117,712 20 to 29 152,767 30 to 39 17,413 40 to 49 4,703 49 and up 1,309 * All ratesare per 1,000person-daysof exposure.
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Course Participants
Injury (Rate, CI)*
Illness (Rate, C|)*
10,977
839 (2.3, 2.2 to 2.5)
529 (1,5, 1.4 to 1.6)
111 (0.3, 0.3 to 0.4)
7,407 3,570
505 (2.1, 1.9 to 2.3) 334 (2.9, 2.6 to 3.2)
301 (1,2, 1.1 to 1.4) 228 (2.0, 1.7 to 2.2)
76 (0.3, 0.2 to 0.4) 35 (0.3, 0.3 to 0.4)
8,094 2,883
742 (2.5, 2.3 to 2.7) 97 (1.5, 1.2 to 1.8)
491 (1,7, 1.5 to 1.8) 38 (0,6, 0.4 to 0.8)
110 (0.4, 0.3 to 0.4) 1 (0.01)
3,238 3,797 744 242 73
317 (2.7, 2.4 to 3.0) 366 (2.4, 2.2 to 2.6) 38 (2.2, 1.5 to 2.9) 16 (3.4, 1.7 to 5.1) 5 (3.8, 0.5 to 7.2)
211 (1.8, 1.6 to 2.0)
42 (0.4, 0.2 to 0.4)
253 (1.7, 1.5 to 1.9) 22 (1.3, 0.7 to 1.8) 5 (1.1, 0.1 to 2.0) 0
45 (0.3, 0.2 to 0.4) 19 (1.1, 0.6 to 1.6) 4 (0.9, 0.07 to 1.7) 0
Nonmedical (Rate, CI)*
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the other two were of unknown etiology. All three cases responded to epinephrine administered in the field. Of five cases of abdominal pain, three were evaluated by a physician after evacuation. The diagnoses included peptic ulcer disease, u r i n a r y tract infection, and nonspecific abdominal pain that resolved after 24 hours in the hospital. Table 5 lists the illness type by b r a n c h headquarter. The Mexico and Wyoming branches r e p o r t e d significantly higher illness rates than did the Alaska or Washington branches (P < .001). Viral syndromes occurred more frequently in the Mexico b r a n c h (P < .001), and d i a r r h e a afflicted more participants on courses from Mexico and Wyoming (P < .001). Alaska reported significantly fewer cases of d i a r r h e a than did the other branches (P < .001). Field experience suggested that younger students were less likely to adhere to wilderness hygiene guidelines. To see if hygiene practices correlated with the incidence of viral syndromes and d i a r r h e a , we combined the two categories and compared the rate by status and age. The rate for viral and diarrheal illnesses combined for students was significantly higher than for instructors (students, 1.0 p e r 1,000 persondays of exposure; CI, 0.9 to 1.1; instructors, 0.4; CI, 0.2 to 0.5; P < .001), and the rate was inversely related to age (P < .01). Of 1,479 incidents, 634 (43%) required evacuation (Table 6). Students required evacuation more often than did instructors (P < .001), and women needed evacuation more often than did men (P < .001). Only 29 victims (2%) were unable to evacuate u n d e r their own power (assisted evacuations). Twenty-four of the assisted evacuations were for injuries: sprains and strains (12), fractures/dislocations (ten), soft tissue injuries (two), and other (one). Five individuals required assisted evacuation for an illness: high-altitude illness (two), abdominal pain (one), and nonspecified illnesses (two). History of Injury or I l l n e s s A history of the specific injury or illness was obtained at the time of the incident for 16% of injuries and 10.5% of illnesses, o f those individuals who gave a history of the incident, 93% had listed the history on the precourse medical form. A history existed for 25% of sprain/strain/tendon injuries and 13% of fractures. Ten percent of persons developing symptoms of high-altitude illness had a history of the illness. Table 2. Type of injury (column~rowpercentage) Injury Total Sprains/strains Soft tissue Wound infections Fractures Immersion foot Burns Dislocations Frostbite Blisters Other
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Evacuations (%)
839 (100/100) 443 (53/100) 226 (27/100) 36 (4/100)
348 ( 100/41) 183 (53/41) 69 (20/30) 20 (6/55) 25 (7/96) 12(3/52) 4 (1/22) 10 (3/77) 1 (0.4/12) 2 (0.6/29) 22 (6/56)
23(3/100) 18 (2/100) 13 (1/100) 8 (1/100) 7 (1/100) 39 (5/100)
Table 3. Anatomic location of injuries Location Foot Ankle Lower leg Knee Thigh
Hip
Total (%)
26 (3/100)
W i I d e r n e s s A c t i v i t i e s Because courses or course sections focused on a specific wilderness activity, we were able to compare injury, illness, and evacuation rates by major course activity (Table 7; Figure 3), In this study, backpacking was the most commonly performed wilderness activity (43% of total person-days of exposure) and is generally considered a low-risk activity. We therefore used the injury, illness, and evacuation rates incurred on backpacking courses as a baseline for comparing the other activities. Both white water paddling and Nordic skiing had significantly higher injury rates than did backpacking courses (P < .001), and horsepacking courses generated significantly fewer injuries (P < .001). Rock climbing, a wilderness activity traditionally associated with high risk, also generated lower injury rates than did backpacking (P < .05). Illness rates were significantly higher for rock climbing (P < .001), Nordic skiing (P < .001), white water paddling (P < .001), and caving courses (P < .001). Although the pattern of activity-specific injury rates for students conformed to that of the group as a whole, the pattern for instructors differed dramatically (Figure 4). Caving incurred the highest instructor injury rate and was the only activity with a significantly higher rate than backpacking (P < .05). Instructor injury rates for Nordic skiing and white water paddling were comparable with the rate for b a c k p a c k ing. On rock climbing courses, instructors sustained a higher injury rate (2.9 p e r 1,000 person-days of exposure; CI, 1.0 to 4.8) than did students (1.4 per 1,000 person-days of exposure; CI, 0.8 to 2.0) with the difference approaching statistical significance (P = .052). Although instructors also sustained higher injury rates on caving courses, the difference was not significant (P = .205).
ANNALS OF EMERGENCY MEDICINE
Assisted Evacuations(%) 24 (100/3) 12 (50/3) 2 (8/1) 0 8 (33/31) 0. 0 2 (8/15) 0 0 0
Pelvis Lower back Upper back Neck Face Head Shoulder Upper arm Elbow Forearm Wrist Hand Chest Missing
Sprain/ Strain
Soft Tissue
Fracture/ Dislocation
Other
Total
13 143 5 139 6 5 1 41 25 7 3 0 21 1 1 1 16 9 2 4
32 8 16 19 9 4 6 5 3 0 37 13 2 1 4 4 0 55 2 6
3 8 0 1 1 2 0 0 0 0 2 0 7 0 2 1 2 8 1 1
43 4 8 1 4 0 2 4 0 0 27 4 1 2 0 0 0 15 0 26
91 163 29 160 20 11 9 50 28 7 69 17 31 4 7 6 18 87 5 37
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DISCUSSION Wilderness is defined as a region uncultivated and uninhabited by human beings. 5 Because wilderness activities take place in remote areas distant from usual sources of medical care, a much higher level of medical seE-sufficiency is required than with most other recreational activities. When professional medical care is available, rescue and treatment are made more difficult by the remote setting. Knowledge of likely problems may prepare both lay and medical personnel to approach Victims with greater speed and better equipment. The injury and illness patterns described in this study have important implications for all wilderness recreationists. Eighty percent Of injuries fell into the categorie s of soft tissue injuries and sprain/strain/tendon. Clearly, essential medical skills for wilderness recreation include wound management, early recognition and intervention for overuse injuries, and treatment of sprains and strains to prevent further injury and potentially allow continued participation. Dealing effectively with these problems in remote environments often requires approaches and equipment different from those used in health care facilities. Diarrhea was the most common illness (30%), followed closely by nonspecific viral syndromes (30%). As discussed below, data from this study suggest that strict hygien e and water disinfection practices may reduce the incidence of diarrheal and viral illnesses during wilderness recreation. Acute mountain sickness, hypothermia, and heat illness occurred infrequently despite considerable exposure to harsh environments , and most victims did not require evacuation. These entities and certainly their severe manifestations can be largely prevented with p r o p e r equipment (hypothermia), acclimatization (acute mountain sickness and heat illness), and close attention to early signs and symptoms. All participants in wilderness recreation should
Table 4. Types of illnesses and related evacuations (column~row percentage) Illness Total Virus Oiarrhea Udnarytract infection Respiratory Allergy Anaphylaxis Colorado tick fever Acute mountain sickness Abdominal pain Gynecologic Cardiac Heat i!lness Hypothermia Ear infections Dental Dermatitis Other
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Total (%) 529 152 (30/100) 161 (30/100) 11 (2/100) 7 (1/100) 11 (2/100) 3 (1/100) 2 (1/100) 23 (4/!00) 5 (1/100 17 (3/100 3 (I/100 8 (1/100 18 (3/100 15 (3/100 18 (3/1001 20 (4/1001 55 (10/10(]
Evacuation (%) 18i (100/34) 51 (28/33) 31 (17/19) 4 (2/36) 4 (2/57) 4 (2/36) 2 (!/67) 2 (1/100) 9 (5/39) 3 (2/60) 6 (3/35) 3 (2/100) 1 (1/12) 1 (i/5) 5 (3/33) 10 (5/56) 3 (2/15) 42 (23/76)
Assisted Evacuation (%) 5(100/1) 0 0 0 0 0 0 0 2 (40/9) 1 (20/20) 0 0 0 o 0 0 0 2 (40/4)
be familiar with the prevention and early recognition and management of these illnesses. Studying structured courses m wilderness recreation allowed us to accurately define a population at H s k and gather precise exposure information for a variety of wilderness activities. The structured course format also provided a consistent and realistic wilderness experience. Courses took place in remote wilderness environments, and all participants functioned as active team members, taking responsibility for their own equipment and sharing in camping, cooking, and other course tasks. However, a limitation of studying structured wilderness courses is the inability to generalize the incident rates to other populations, particularly those participating in wilderness recreational activities without the supervision of trained instructors. Although task demands were high for many activities (expedition mountaineering, rock climbing, white water paddling), the courses emphasized mastery of wilderness skills through a progressive, graduated program to minimize injuries. Less-experienced individuals and groups, persons tempted to exceed their performance capability, or expeditions operating u n d e r extreme environmental conditions may suffer higher rates. The injury and illness rates in this study are notable, however, because they demonstrate that with proper safety procedures, training, and equipment, wilderness activities can be conducted safely. We defined incidents by time lost from participation to standardize inclusion criteria and to facilitate uniform and complete data collection in the field. This definition had the a d d e d advantage of focusing on incidents most likely to affect performance, while eliminating minor complaints. However, this type of operational definition introduces some biases. First, incidents may be activity specific. F o r exampie, a h a n d injury that prevents participation in rock climbing may not interfere with backpacking. Second, the definition assumes that all individuals respond to an incident in a similar manner; in fact, one individual may participate with a given injury or illness whereas another will not. In discussions with instructors, lack of motivation was felt to be a frequent contributor to time lost from participation.
Table 5. National Outdoor Leadership School illnesses by brunch Alaska (Rate, CI)*
Mexico (Rate, CI)*
Washington (Rate, CI)*
Wyoming (Rate, Cl)*
Person-days ofexposure Totalillnesses
541490 25,289 26,616 251,815 40 56 23 410 (0.7, 0.5 to 1.0) (2.2, 1.6 to 2.8)~ (0.9, 0.5 to 1.2) (1.6, 1.5 to 1.8)t Viral 14 24 8 106 (0.3, 0.! to 0.4) (0.9, 0.6 to 1.3)~ (0.3, 0.1 to 0.5) (0.4, 0.3 to 0.5) Diarrhea 2 13 6 140 (0.4) (0.5, 0.2 to 0.8) ~ (0.2, 0.004 to 0.4) ' (0.6, 0.5 to 0.6) t * All rates are per 1,000 person-days of exposure. P< .001.
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It was not surprising that students sustained higher injury, illness, and evacuation rates than did instructors. As a group, instructors are more skilled, experienced, and conditioned all qualities that would be expected to reduce incident rates. In fact, we suspect that the instructor incident and evacuation rates in this study a p p r o a c h the lowest achievable rates given current practices and technology. Although this study did not specifically examine reasons for the higher illness and injury rates observed in female students, several observations are worth noting. Although statistically significant, the practical implications of the higher incident rates for female participants are less clear; female participants suffered less than one additional injury or illness p e r 1,000 days of exposure. The fact that rates for female and male instructors did not differ significantly suggests that the difference among students might have been due to remediable factors such as conditioning. Alternatively, instructors might have been more inclined to enforce cessation of activities for female students who were injured or ill than fo.r male students. Although the National Outdoor Leadership School attempts to place a female instructor on every course, this is frequently not possible because of difficulties in recruiting female staff. We also cannot rule out subjective factors; male students may have been more motivated to continue p a r t i c i p a t i o n despite injury or illness. M 0 r t a I i t y The one fatality during this study deserves special comment. The incident occurred on a climb of Mount W a r r e n in the Wind River Range of Wyoming. A different route was chosen for descent, because it presented less hazard than the narrow and technically more difficult ascent route. As the students were being sequentially lowered over a steep section, a rock "the size of a watermelon" was dislodged, bounced out of the fall line, and struck a student waiting below. The victim was wearing an a p p r o v e d helmet and had moved well to the side of the descent fall line. He died from an i n t r a c e r e b r a l hemorrhage before he could be evacuated from the mountain. Both internal and external
inquiries into the death concluded that the route and equipment were a p p r o p r i a t e for the group and that correct safety procedures were adhered to throughout the climb. 6 Wilderness travel by definition involv~es the potential for encounters with n a t u r a l forces that are unpredictable and uncontrollable. Although many wilderness fatahties p r o b a b l y occur because obvious warning signs and safety procedures are ignored or because individuals choose to engage in extremely hazardous activities, some occur despite p r u d e n t precautions. Although the low mortality rate i n c u r r e d in this study will be acceptable to many individuals, participants should be fully informed regarding the risk of not only injury and illness but also death. Wilderness activities should not be promoted or advertised as risk free. | n j u r i e s Differences in injury definition, d a t a collection, and exposure time prevent direct comparison of injury rates from this study with those published for other recreational activities. Despite this limitation, studying rates for other activities does add an intuitive perspective to the wilderness injury rates. There were 7.6 injuries and 3.2 injury evacuations p e r 100 National Outdoor Leadership School participants. Reported injury rates for football range between 14.5 and 81 p e r 100 participants. 7 Gymnastics injuries range from 28 to 138 p e r 100 participants. 7 Unfortunately, calculating incidence rates by number of participants does not take into account differences in exposure time. Although athletic seasons may last three to five months, exposure is usually limited to a few hours p e r day. One recreational activity for which comparable exposure data exists is downhill skiing. Reported injury rates for downhill skiing range from 2.8 to 5.9 p e r 1,000 person-days of exposure versus 2.3 injuries p e r 1,000 person-days for National Outdoor Leadership School.7 Rock climbing and mountaineering are often regarded as high-risk activities. Climbing and mountaineering injury rates in this study, however, were lower than or the same as Table 7.
Activity-specifw incidents (all rates tested against backpacking for significance) Table 6.
Evacuations
Activity
Demographics Total Status Student Instuctor Sex Male Female Incident Type Injury Illness Nonmedical
illness (Rate, CI)*
Evacuations (Rate, CI)*
24,346
91 (3.7, 3.0 to 4.5)*
89 (3.7, 2.9 to 4.4)t
55 (2.3,1.7 to 2.9p
6.678
41 (6.1, 4.3 to 8.0)t
21 (3.1,1.8 to 4.5)*
24 (3.6, 2.2 to 5.0)t
74 (1.8,1.4 to 2.3)§ 37 (2.7,1.8 to 3.6) 5 (0.3, 0.04 to 0.6)t 370 (2.4, 2.2 to 2.6) 31 (1.6,1.1 to 2.2)
53 (1.3,1.0 to 1.7) 46 (3.4, 2.4 to 4.4}t 5 (0.3, 0.04 to 0.6)t 164 (1.1, 0.9 to 1.2) 54 (2.8, 2.1 to 3.6)t
26 (0.6, 0.4 to 0.9)t 33 (2.4,1.6 to 3.3)t 6 (0.3, 0.1 to 0.6)t 216 (1.4,1.2 to 1.6) 35 (1.8,1.2 to 2.4)
Incidents
1,479
634 (1.8,1.6 to 1.9)
29 (0.08, 0.05 to 0.1 )
1,343 136
570 (1.9,1.8 to 2.1 )t 64 (1.0, 0.8 to 1.2)
25 (0.08, 0.05 to 0.1) 4 (0.06, 0.001 to 0.1)
882 597
398 (1.6,1.5 to 1.8) 236 (2.0, 1.8 to 2.3) t
23 (0.09, 0.06 to 0.1) 6 (0.05, 0.001to 0.09)
Sea kayaking] sailing 40,005 Caving 13,566 Hersepacking 16,996 Backpacking 154,066 Rock climbing 19,038 Expedition mountaineering 7,566
24 (0.07, 0.04 to 0.09) 5 (0.01, 0.002 to 0.03) 0
Mountaineering 50,275 Snow/ice climbing 25,674 Missing
839 529 111
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Nordic skiin9 White water paddling
Injup/ (Rate. CI)*
Evacuations (Rate, CI)*
348 (1.0, 0.9 to 1.1 ) 181 (0.5, 0.4 to 0.6) 105 (0.3, 0.2 to 0.3)
* All rates are per 1,000 person-days of exposure. t p< .OOl.
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Assisted Evacuations (Rate, CI)*
Exposure Days
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11 (1.4, 0.6 to 2.3)
7 (0.9, 0.2 to 1.6)
6 (0.8, 0.2 to 1.4)
103 (2.1,1.7 to 2.4)
54 (1.1, 0.8 to 1.4)
78 (1.5,1.2 to 1.9)
57 (2.2,1.6 to 2.8) 19
21 (0.8, 0.5 to 1.2) 15
35 (1.4, 0.9 to 1.8) 15
* All ratesare per 1,000person-days of exposure. 1"P < .001; * P < .0t; § P < .05,
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injury rates for backpacking. Evacuation rates were also comparable, suggesting that i n j u r y severity did not differ significantly. The results indicate that learning these technically demanding wilderness skills need not entail excessive risk if appropriate attention is directed to training, equipment, and safety. The higher i n j u r y rate for instructors versus students on rock climbing courses may reflect an increased risk associated with leading muhipitch climbs. This hypothesis is being investigated. Until additional research is completed, we can only speculate as to why i n j u r y rates were significantly higher from Nordic skiing and white water paddling courses. It is interesting to note that despite the differences between the two activities, there are pertinent similarities. Both activities are technically demanding and, at times, conducted at high rates of speed, requiring rapid reaction times. Both use levers (skis and paddles), which serve to increase the forces applied to the most commonly injured h u m a n body parts. The fact that injury rates for instructors on these courses were not increased suggests that training and skill can compensate for the high demands of these activities. ] I I n e s s e s Viral syndromes and diarrhea accounted for 60% of the illnesses and 45% of the illness evacuations. We
suspect that some of these illnesses are hygiene related. Virtually all students in this study were from Western countries where sanitation is taken for granted: However, remote wilderness travel requires leaving behind modern sanitation and reliably disinfected tap water. Although surveys reveal widespread contamination of surface water in wilderness areas, 8 convincing students to maintain strict wilderness hygiene and water disinfection practices during a long Stay in apparently pristine wilderness areas is problematic. Data on illnesses by the National Outdoor Leadership School branch suggest a causal role for transmissible pathogens and hygiene in viral illnesses and diarrhea in the wilderness. The Alaska branch generated significantly lower rates of these illnesses than did the other branches. Alaska trip leaders enforce particularly strict cooking and camping hygiene practices because of the threat of grizzly bear attacks. The bear threat also provides strong motivation for students to adhere to hygiene guidelines. However, courses in Mexico, a high-risk area for traveler's illnesses, reported the highest total illness rate, with a particularly high rate of viral illnesses. Diarrhea was equally Figure 4.
Figure 3.
Instructor and student activity-specific injury rates (per 1,000 person-days of exposure)
Activity-specific injury and illness rates (per 1,000 person-days of exposure)
•
Backpacking
Injuries
Total Backpacking
Students
Illnesses
Instructors Skiing Skiing
White water paddling
White water I paddling
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Sailing/kayaking
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•
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Sailing/kayaking
Cavir~g
Caving
Horsepacking
Horsepacking
Rock climbing
Rock climbing
Expedition mountaineerin
Expedition mountaineerinc
Mountaineering
Mountaineering
Snow/ice climbing
I
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Snow/ice climbing ~ii!iii~ii~ii~i~i~iiiliiii~i:i~i~i~@!iiiii~i~i~i~iiiii~i~i~iii~iiiiit
m
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2
3
4
6
7
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I
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4
5
6
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common during the Mexico and Wyoming courses. Most of the three-month semester courses are conducted out of the Wyoming branch; the length of the courses and the absence of overt risk factors add to the difficulty in maintaining hygiene standards among students. Field observations confirm deterioration in hygiene practices during longer courses. The decrease in illness rates with increasing age resulted primarily from lower rates for viral illnesses and d i a r r h e a in older age groups. Field observations strongly suggest that older individuals adhere t ° wilderness hygiene guidelines more closely. Confirming the link between wilderness hygiene and illnesses requires further study, but information on travelers' d i a r r h e a suggests that hygiene precautions may be effective in reducing the spread of transmissible pathogens .9 E v a c u a t i o u s Evacuation rates provide critical information on incident severity for wilderness activities. The need to evacuate an individual from a remote environment not only jeopardizes the objectives of the group but may place group members at increased risk. Mountain, white water, or ocean rescues are frequently hazardous for the rescuers as well as the victims. An incident severe enough to require evacuation will likely impair the victim's ability to carry a load or assist with other tasks. Even if a victim is able to leave the wilderness under his or her own power, safety generally dictates that the victim be accompanied by at least one other group member. Assisted evacuations place extreme demands on the entire group. Transporting a nonambulatory victim over wilderness terrain generally requires six to eight people p e r mile, multiplying the logistic Problems of food, shelter, and rest. Helicopter rescues are expensive and often dangerous. This study demonstrates that wilderness activities require evacuation with sufficient frequency (1.8 per 1,000 persondays of exposure) that the need must be anticipated. Evacuation plans should be formulated before embarking, and an itinerary should be recorded with someone who will recognize when a trip is overdue. A p p r o p r i a t e evacuation equipment should be included in the trip provisions. I n j u r y / i l l n e s s P r e v e n t i o n This study suggests several mechanisms for reducing wilderness injuries and illnesses and provides direction for further research. Two injury categories--sprain/strain/tendon and soft tissue i n j u r i e s - - a c c o u n t e d for 80% of the injuries and 72% of the injury evacuations in this study. Clearly, to effect a substantial reduction in wilderness injury rates, injury prevention strategies must focus on these two categories. A significant number of sprain/strain/tendon incidents represented r e c u r r e n t injuries. A history was confirmed for 25% of sprain/strain/tendon injuries and for 16% of all injuries and 11% of all illnesses. This raises the possibility of directing interventions at specific problems before and during the p r o g r a m to prevent recurrences. F o r example, recurrent ankle injuries might be prevented by high-top boots, an air splint, taping, or simply emphasizing trail awareness.
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Some preventive measures have already been implemented in National Outdoor Leadership School courses as a result of this study. In an attempt to improve hygiene and reduce the incidence of viral illnesses and diarrhea, instructors now use group cooking and wash stations on the Mexico and Wyoming semester courses. Biodegradable soap is issued to students, and in group cooking situations utensils are rinsed in a chlorine solution after each use. Course instructors are urged to be aggressive in education and oversight of hygiene and water disinfection practices. The impact of these changes is being investigated. The high injury rate (6.1 p e r 1,000 person-days of exposure) on white water courses p r o m p t e d a review of those activities. Most of the white water courses took place at the end (days 65 to 90) of a 95-day semester course. The itinerary for those courses was demanding and fast paced, and both the weather and water were often cold. Because fatigue may have been an important factor in the injury rate, the pace of the white water courses has been reduced and rest days have been built into the itinerary. Because 58% of the white water injuries were in the sprain/strain/tendon category, staff now receive training in early intervention of overuse injuries, and a program of stretching and warm-up exercises has been initiated. If close attention to fatigue factors and early field intervention for overuse syndromes is effective in lowering injury rates in white water courses, the same principles may be transferable to other activities.
CONCLUSION The low injury and illness rates in this study demonstrate that with a p p r o p r i a t e training and equipment, wilderness activities can be conducted safely. However, the isolated environment in which they occur requires anticipating and p r e p a r i n g for likely problems if effective early medical intervention is to be instituted. Determining the types and frequencies of wilderness injuries and illnesses should facilitate this process and will hopefully lead to successful preventive strategies. We believe that the challenges and attractions of wilderness activities outweigh the relatively low risks r e p o r t e d in this study. However, defining acceptable rates of injury and illness is of necessity an individual determination and depends on the perceived benefits of the activity versus the individual's willingness to take risks. This study, by beginning to delineate the risks of wilderness activities, provides essential information in allowing prospective participants to make informed decisions regarding participation.
REFERENCES 1. National Sporting 6oods Association: Sports Participation in 1988:Series L Mt Prospect, Illinois, NSGA. 2. Williamson JE (ed): Accidents in North American Mountaineering 1985.New York, American Alpine Club, 1985.
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3. Schussman LC, Lutz LJ, Shaw RR, et al: The epidemiology of mountaineering and rock climbing accidents. J Wilderness Med 1990;1:235-248.
Address for reprints: Douglas A Gentile, MD, Emergency Department, Stanford University Hospital, 300 Pasteur Drive, Stanford. California 94305.
4. Rosner B: FundamentalsofBiostatistics, ed 2. Boston, Duxbury Press, 1986. 5. Mish FC (ed): Webster's Ninth New Collegiate Dictionary. Springfield, Massachusetts, Merriam-Webster, 1983. 6. Williamson JE (ed): Accidents in North American Mountaineering 1990.New York, American Alpine Club, 1990. 7. Kraus JF, Conroy C: Mortality and morbidity from injuries in sports and recreation. Annu Rev Public Health 1984;5:163-192. 8. Backer HD: Field water disinfection, in Auerbach PS, Geehr EC (eds): Management of Wilderness and Environmental Emergencies. St Louis, CV M osby Co, 1989, p 805-827. g. Kozicki M, Steffen R, Sher M: "Boil it, cook it, peel it, or forget it": Does this rule prevent travelers' diarrhoea? IntJ Epidemio11985;14:169-172.
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