Seatbelt Effectiveness and Cost of Noncompliance Among Drivers Admitted to a Trauma Center BURTON H. KAPLAN, MD, R. ADAMS COWLEY, MD Enactment of seatbelt legislation in Maryland presented the opportunity to compare seatbelt compliance among seriously injured drivers admitled to a Level I trauma center and to establish levels of severity, length of stay, and hospital cost differences among the study population. Fifty-five randomly selected drivers were examined from a total surgical population of 669. Seatbelt compliance rate was 41.6%, reflectlnfj the rate In the community. Seatbelts reduced the total number of injuries by 34%, major Injuries by 57%, and minor injuries by 20%. No deaths occurred among the belted group. The unbelted group had a mean Injury Severity Score two times as great as the belted group and were hospitalized 1.6 times longer at double the cost. Major injuries to the face, chest, and pelvic regions were prevented by the seatbelt. Among the belted group, severe injuries did occur to the head, neck, and abdominal regions. It is recommended that both airbags and automatic restraining devices be required for all drivers If the trauma occurring daily on highways is to be eliminated and acute hospital cost minimized. (Am J Emerg Med 1991;9:4-10. Copyright 0 1991 by W.B. Saunders Company)
The effectiveness of restraint systems in reducing fatal outcomes and severity of injury in motor vehicle occupants injured in crashes is well documented.“4 The National Highway Traffic Safety Administration (NHTSA) estimates that, for every 10% increase in belt use, 1,500 deaths will be prevented, 30,000 moderate-to-serious injuries will be reduced, and 600 to 800 million dollars will be saved annually.5 In 1974, standards promulgated by the Department of Transportration (DOT) required that all passenger vehicles manufactured be equipped with a combination lap and shoulder restraint system. Between 1974 and 1985, national voluntary seatbelt usage rates were approximately 12% and, in Maryland, less than 20% in 1985, despite multiple educational programs aimed toward increasing voluntary use by the public.6 From 1981 to 1984, the requirement for all passenger vehicles manufactured to have “automatic passive restraint systems” was debated and a compromise was made between the automobile manufacturers and DOT.’ Manufacturers would not be required to equip passenger vehicles with automatic passive restraint systems if mandatory state seatbelt legislation would encompass two thirds of the United States population. As of 1987, seatbelt usage legislation has been enacted in 31 states and the District of Columbia; 16 states are in the process of enacting legislation and 2 have repealed From the Maryland Institute for Emergency Medical Services Systems, Baltimore, MD. Manuscript received October 30,1989; revision accepted April 1, 1990. Address reprint requests to Dr. Kaplan: 9318-B Sable Ridge Circle, Boca Raton, FL 33428. Key Words: Seatbelts, trauma, hospital costs. Copyright 0 1991 by W.B. Saunders Company 07356757/91/0901-0002$5.00/O 4
their laws. Usage is influenced by mandatory seatbelt usage laws, enforcement policies, penalties incurred as a result of violating the law, and various educational programs informing the public as to the risks-benefits of seatbelt restraints.‘-” Nationally, mandatory seatbelt usage laws have increased usage from a low of 12% to 46%, with a range of 28.9% to 67.8%.” In states with seatbelt laws, the reduction in motor vehicle fatalities and injuries has not been so great as predicted from observed belt usage rates and the estimated protection of belts in crashes.‘* This observation and the enactment of mandatory seatbelt legislation in Maryland, effective July 1, 1986, afforded the opportunity to study this program and identify the reasons for these differences. A pilot study was designed to determine seatbelt effectiveness in reducing injury and to determine the cost of seatbelt noncompliance among a sample of injured drivers admitted to the Shock Trauma Center of the Maryland Institute for Emergency Medical Services Systems (MIEMSS). MATERIAL AND METHODS
The study was limited to drivers of passenger cars, vans, and light trucks, who were injured as a result of collision with another vehicle or fixed object, rollover, or rear-end collision and directly admitted to the MIEMSS Shock Trauma Center between July 1, 1986 and June 30. 1987. Crash, hospital admission, and disposition data were collected prospectively by senior medical students randomly assigned to one of four trauma teams. These data consisted of demographic information, time of crash, estimated crash speed, type of impact, type and size of vehicle, and restraint status. Medical students contacted the on-scene prehospital care provider within 24 hours to determine restraint status and crash data. Admission data consisted of alcohol levels, admission time, number and types of injuries, and disposition. The hospital course data were collected retrospectivelyl from medical records and consisted of number and severity of injuries, length of stay (LOS), and discharge disposition. Injury severity scores (ISS) were calculated by the author [Kaplan], according to the 1985 revision of the Abbreviated Injury Scale of the American Association for Automotive Medicine. l3 Hospital charges were supplied by the Financial Officer of MIEMSS, and professional fees by the Shock Trauma Associate Physicians Office. Parametric and nonparametric statistical tests were used for data analysis. RESULTS Study Population Description
Demographic information for the 55 subjects is presented in Table 1. Ages ranged from 16 to 76, with a mean of 32
KAPLAN AND COWLEY n SEATBELT COMPLIANCE
5
TABLE1. Population Characteristics and Seatbelt Compliance Rate (SBCR) Parameter Gender Race
Age (yr) Employment
Alcohol use Month of crash Vehicle type
Male Female White Black Asian 30 Yes No Retired Unknown Yes No July-December 1986 JanuaryJune 1987 Auto Van Light truck
N (%)
SBCR (%)
34 (62) 21 (38) 46 (84) 7 (13) 2 (4) 29 (53) 26 (47) 38 (69) 7 (13) 3 (5) 7 (15) 17 (31) 38 (69) 13 (24) 42 (76) 48 (87) 3 (5) 4 (7)
44 38 39 43 100 52 31 37 28 33 88 35 45 54 38 42 67 25
years. Seventeen drivers (31%) were alcohol positive on admission; 12 (71%) of them had alcohol levels above 100 mg/ dL. Forty-eight subjects drove cars (87.3%), three drove vans (5.40/o), and four drove light trucks (7.3%); 27 of the car drivers operated small or mid-sized vehicles (wheel base size cl09 inches) at the time of crash (Table 2). Collisions occurred mostly between 6 PM and midnight, accounting for 44% (24) of all crashes. The overall seatbelt compliance rate (SBCR) was 41.8%. The SBCR was greater from July through December 1986 (54%) than from January through June 1987 (38%). A total of 249 injuries were distributed among the 55 subjects, with an average of 4.53 injuries per subject. There were 164 (66%) AIS l-2 type injuries (minor) and 85 (34%) AIS 3-5 type injuries (major). The average number of minor injuries was 2.98 per subject and, for major injuries, 1.54 per subject (Table 3). Multiple injuries occurred within the study population. The most commonly recorded anatomical region of injury was the head (71%), followed by soft tissue (39%), extremities (38%), chest (33%), pelvis (24%), face (22%), abdomen (18%), and neck (11%). The ISS associated with these anatomical regions ranged from 1 to 66, with a mean of 14.2. The LOS ranged from 1 day to 110 days (mean, 13.5 days). The mean hospital cost was $30,719, with a range of $1,989 to $217,606 (Table 4). On arrival at the trauma facility, 24 subjects were admitted directly to the operating room (OR) (44%), 6 to the critical care recovery unit (CCRU) (ll%), 12 to the intensive care unit (ICU) (22%), and 13 to the general care unit (24%) (Table 5). The majority of the study population, 41 (710/o), were discharged home. Following their hospital course, 10 (18%) required rehabilitative facilities. Four patients expired (7.3%) (Table 6). Characteristics of Belted Subjects There were 23 seatbelt-compliant subjects: 15 males (10 white, 3 black, 2 Asian) and 8 females (white). Their mean
age was 30.4, with a range of 19 to 58 years, 66% (15) of these belted drivers were between the ages of 19 and 29 and 35% (8) were between age 30 and 50. Fourteen were employed, 2 were unemployed or students, 1 was retired, and the employment status of six was unknown. Within this group, 26% (6) were alcohol-positive drivers, three of whom had levels greater than 100 mg/dL, ranging from 154 to 167 mg/dL. The mean age of these alcohol-positive drivers was 22.2 years, with a range of 20 to 24 years. Thirty-nine percent (9) drove small vehicles (wheel base ~99 inches), 26% (6) drove mid-size vehicles, and 13% (3) large vehicles. The vehicle size was unknown for 22% (5) of this group. Seventy-eight percent (18) of belted drivers crashed between 6 PM and 6 AM, 52% (12) between 6 PM and midnight, and 22% (5) between 6 AM and 6 PM. Of the 23 collisions among belted drivers, 74% (17) were frontal impact, 13% (3) side impact, 9% (2) rollover, and 4% (1) rear-end impact. Estimated crash speed determinations were 3 1 to 55 mph for 61% (14) of crashes involving belted drivers and less than or equal to 30 mph in 39% (9). Seven of the belted driver crashes occurred between July and December 1986, and 16 between January and June 1987. Belted Group Injuries Among the 23 belted drivers, there were a total of 80 injuries, averaging 3.4 injuries per driver. Three-fourths (60) were minor injuries (AIS l-2) and one-fourth (20) major injuries (AIS 3-5). The average number of major injuries per driver was 0.87. The nine collisions occurring at less than or equal to 30 mph resulted in 28 injuries, representing 35% of the total belted group injuries; 71% (20) of the injuries were minor and 29% (8) were major. The total injury distribution for this subgroup was 3.1 injuries per driver: 2.2 injuries per driver for minor and 0.89 for major injuries. For crash speeds greater than 30 mph there were 52 injuries, representing 65% of the total injuries in the belted group; 77% (40) were minor TABLE2. Vehicle Characteristics and Seatbelt Compliance Rate Parameter Vehicle (wheel base in inches) Small (c99) Mid (100-109) Large (>109 Unknown Crash time 6 AM-~ PM 6 PM-midnight midnight-6 AM Crash speed (mph) 930 31-55 >55 Unknown Ejections Crash vector Frontal Multiple Side Rear Rollover Unknown
N (%)
SBCR (%)
12 (22) 15 (27) 11 (20) 27 (31)
75 40 27 29
14 (25) 24 (44) 17 (31)
36 50 35
13 (24) 31 (56) 9 (16) 2 (4) 5 (100)
69 47 0 0 0
34 (62) 1 (2) 12 (22) 2 (4) 4 (7) 2 (4)
50 0 17 50 50 0
AMERICAN JOURNAL OF EMERGENCY MEDICINE I Volume 9, Number 1 n January 1991
6
TABLE3. Injury Severity Score, Injuries, and Seatbelt Compliance Rates (SBCR) by Speed and Impact Site No. of Injuries
Crash Speed (mph) ISS
N (%)
Impact
Belted
s30
>30
u
F/M
S
0
U
Yes (%)
l-09 lo-19 20-29 30-39 c40
23 (42) 13 (24) 10 (16) 5 (9) 4 (7)
7 3 2 1 -
16 10 6 4 4
2 -
14 7 7 2 3
7 2 1 1 -
1 2 2 1 -
1 2 1 1
36 (45) 24 (30) 20 (25) -
Total
55(100)
13
40
2
33
11
6
5
60 (1200)
ABBREVIATIONS:
U, unknown; F/M, frontal/multiple;
Total (%)
SBCR (%)
36 (21) 36 (22) 26 (17) 29 (22) 36 (16)
72 (29) 62 (25) 48 (19) 29 (12) 36 (15)
56.5 42.6 40.0 0 0
169 (100)
249 (100)
41.6
S, side; 0, other.
and 33% (12) were major. The total injury distribution in this subgroup was 3.7 injuries per driver: 2.86 for minor and 0.86 for major injuries. The most commonly recorded anatomical regions of injury for the belted group were soft tissue (74%), head (65%), extremities (22%), pelvis (17%), abdomen (13%), chest (13%), neck (14%), and face (9%). The ISS associated with these ranged from 1 to 29, with a mean of 10.8. The mean ISS at crash speeds less than or equal to 30 mph was 9.8, which increased to a mean of 11.4 with crash speeds greater than 30 mph (Tables 3 and 4). The mean ISS of the alcohol-positive belted drivers was 10.8, with a range of 5 to 20. The LOS ranged from 1 to 32 days (mean, 10.8 days). For crash speeds less than or equal to 30 mph, the LOS ranged from 1 to 24 days, with a mean of 9.2; for crash speeds greater than 30 mph the LOS ranged from 1 to 32 days, with a mean of 10.5. For alcohol-positive belted drivers, the mean LOS was 10.8, with a range of 1 to 24 days. The mean hospital cost for belted drivers was $19,414 (range, $2,055 to $57,942). Of the 23 seatbelt-compliant drivers admitted to the trauma facility, 44% (10) were admitted directly to the OR; 4% (1) directly to the CCRU: 22% (5) directly to the ICU; and 31% (7) directly to the general care unit. The mean ISS and mean LOS for direct OR admissions were 13.6 and 16.2, respectively; for the CCRU, 9 and 12, respectively; for ICU admission, 4.2 and 4.4, respectively; and for the general care unit, 3.3 and 4.9, respectively (Table 5). The belted group had a 91.3% (21) disposition to home, and 9.5% (2) went to a rehabilitation facility (both from crashes greater than 30 mph). All of the belted, injured, alcohol-positive patients were discharged home. There were no deaths (Table 6) or ejections among the seatbelt population.
TABLE4. Number of Injuries; Average Injuries per Driver; Mean ISS, LOS, and Cost According to Restraint State Seatbelt Yes (N = 23)
No (N = 32)
Total (N = 55)
Significance
Injuries/driver Mean ISS Mean LOS Mean cost
3.4 10.6 10.6 $19,414
5.3 22.9 17.0 $38,845
4.5 14.2 13.5 $30,719
P < .0005 P < .0005 P< .l P -=z.025
ABBREVIATIONS:
ISS, injury severity score; LOS, length of stay.
Variable
No (%)
Characteristics
of the Unbelted
Subjects
Thirty-two subjects were not wearing seatbelts at the time of their crash: 19 males (17 white, 2 black) and 13 females (11 white, 2 black). The mean age was 34.1 years, with a range of 16 to 76 years; 44% of the unbelted drivers were between the ages of 16 and 29; 56% were aged 30 to 76. Twenty-four were employed, 5 were unemployed or students, 2 were retired, and 1 had an unknown employment status. Within this group, 34% (11) were alcohol-positive drivers, 73% (8) of whom had levels higher than 100 mg/dL, ranging from 115 to 333 mg/dL. The mean age of the alcohol-positive drivers was 21.4 years, with a range of 1 to 45 years. Nine percent (3) operated small vehicles; 28% (9) operated medium-sized vehicles; and 25% (8) large vehicles. The vehicle size was not reported for 38% (12) of this group. Seventy-two percent (23) of the unbelted drivers crashed between 6 PM and 6 AM; 38% (12) of these crashes occurred between 6 PM and midnight and 28% (9) between 6 AM and 6 PM. Of the 32 collisions in this group, 53% (17) were frontal impact, 31% (10) side impacts, 6% (2) rollover, 3% (1) rearend impact, and 6% (2) unknown impact direction. Fifteen percent (5) of the unbelted drivers were ejected from their vehicle during the crash sequence: 2 from rollovers, 2 from frontal collisions, and 1 in an unknown type of impact. Estimated crash speed determinations were 31 to 55 mph for 53% (17), greater than 55 mph for 28% (9). and less than or equal to 30 mph for 12% (4). The crash speed was unknown for 6% (2). Six of the 32 unbelted driver crashes occurred between July and December 1986, and 26 between January and June 1987. The 32 unbelted drivers had a total of 169 injuries, averaging 5.3 injuries per driver. Sixty-two percent (104) were minor injuries and 38% (65) were major injuries (Table 3). Minor injuries averaged 3.25 per driver, and major injuries averaged 2.03 per driver. Collisions occurring at 30 mph or less (4) resulted in 14 injuries, representing 8% of the total injuries in the unbelted group (78% [ll] minor and 22% [3] major). The total injury distribution for this subgroup was 3.5 injuries per driver: 2.75 for minor and 0.75 for major injuries. In the 15 crashes between 31 and 55 mph, there were 77 injuries, representing 46% of the total injuries in the unbelted group; 7% (61) were minor and 21% (16) were major injuries. The total injury distribution for crash speeds between 31 and 55 mph was 5.1 injuries per driver: minor, 4.1, and major, 1.1 per driver. For crashes (8) at greater than 55 mph,
KAPLAN AND COWLEY n SEATBELT COMPLIANCE
7
TABLE 5. Admission Disposition vs Restraint State with Mean ISS and LOS Seatbelt Yes
No
Admission Unit
N,
ISS
LOS
N2
ISS
LOS
Total: N, + N2 (%)
OR CCRU ICU Ward
10 1 5 7
13.6 9.0 4.2 3.3
16.2 12.0 4.4 4.9
14 5 7 6
31.5 17.6 6.7 3.6
25.7 16.6 5.4 3.6
24 (44) 6(11) 12 (22) 13 (24)
42 17 42 54
Total
23
10.6
10.0
32
22.9
17.0
55
41.6
SBCR (%)
ABBREVIATIONS: SBCR, seatbelt compliance rate; ISS, injury severity score; LOS, length of stay; OR, operating room; CCRU, critical care recovery unit; ICU, intensive care unit.
there were 49 injuries, representing 29% of the total injuries in the unbelted group; 39% (19) were minor and 61% (30) were major. The total injury distribution for this subgroup was 6.1 injuries per driver: 2.4 for minor and 3.7 for major injuries. There were 29 injuries (representing 17% of the total injuries in the unbelted group) associated with 5 ejection-type crashes: 2 rollovers (1 at 85 mph), 2 frontal (1 at 45 mph), and 1 unknown type. In this subgroup, 45% (13) were minor and 55% (16) major injuries. The total injury distribution for drivers crashing and being ejected was 5.8 injuries per person: 2.6 for minor and 3.2 for major injuries. The most commonly recorded anatomical regions of injury for the unbelted drivers were head (75%), soft tissue (69%), extremities (50%), chest (47%), face (31%), pelvis (28%), abdomen (22%), and neck (9%). The ISS associated with these regions ranged from 1 to 66, with a mean of 22.9. The mean ISS of unbelted drivers with crash speed less than or equal to 30 mph was 16.0; for crash speeds between 31 and 55 mph, the mean ISS was also 16.0; for crash speeds in excess of 55 mph, the mean ISS was 32.9. The ejected drivers’ mean ISS was 33.0. The mean ISS of the 11 alcoholpositive drivers was 14.2, with a range of 5 to 54. The mean hospital cost for the unbelted driver was $38,845, with a range of $1,989 to $217,606 (Table 4). The LOS for’unbelted drivers ranged from 1 to 110 days, with a mean of 17 days. For crash speeds less than 30 mph, the mean LOS was 9 days; for crash speeds between 3 1 and 55 mph, 18.1 days; for crash speeds greater than 55 mph, 17.8 days. Of the 32 unbelted drivers admitted to the trauma facility, 44% (14) were admitted directly to the OR, 15% (5) directly to the CCRU, 22% (7) directly to the ICU, and 19% (6)
TABLE6. Hospital Disposition on Discharge According to Seatbelt Compliance Rate (SBCR) Seatbelt Discharge Disposition
Yes N (%)
Home Rehabilitation Morgue
21 (91.3) 2 (9.5) 6 (6)
20 (62.5) 6 (25.0) 4 (12.5)
41 (74) 10 (16) 4 (7.3)
51 25 0
Total
23
32
55
41.8
NY;,
Total N (%)
SBCR (%)
directly to the general care unit. The mean ISS and mean LOS for direct OR admissions were 31.5 and 25.7, respectively; for the CCRU admissions, 17.6 and 18.6, respectively; for the ICU admissions, 6.7 and 5.4, respectively; and for the general care unit, 3.6 and 3.6, respectively (Table 5). The unbelted group had a 62.5% (20) home discharge rate and 25% (8) required rehabilitative services at another facility. Of the 11 unbelted, injured, alcohol-positive drivers, 45% (5) were discharged home and 55% (6) required rehabilitative services at another facility. Four patients expired in the unbelted group, yielding a mortality rate of 12.5% (Table 6); three died from head injuries and one from multiple organ failure. Two of the fatalities had frontal collisions at crash speeds greater than 55 mph (ISS, 66; LOS, 1 and 23 days); one was ejected in a frontal collision at a crash speed of 45 mph (ISS, 38; LOS, 18 days). Seatbelt
Effectiveness
(SEE)
For the purpose of this study, seatbelt effectiveness is defined as a measure of a restraining device’s performance in reducing both the number and severity of injuries resulting from motor vehicle crashes. To facilitate the comparison of seatbelt effectiveness between the two subgroups (belted and unbelted drivers) of the study population, a Multiple Injury Distribution Index (MIDI) was developed. This index represents the total number of injuries occurring within the subgroup equally distributed to all subjects within their respective subgroup. The derived number was then multiplied by 100 to reflect the number of injuries expected to occur in a population base of 100 individuals. For example, the 23 victims in the belted group had a total of 80 injuries, 15 of which were to the head region. This equalled 3.48 injuries per individual, or an MIDI of 348 injuries per 100 belted drivers, and 0.652 head injuries per individual, or an MIDI for head injuries of 65.2 per 100 belted drivers (Table 7). The MIDI was calculated for both subgroups (belted and unbelted) and for their respective anatomical regions. The magnitude and direction of the seatbelt effectiveness rate (SBER) was then derived as follows: SBER =
Unbelted
Index - Belted Index x 100 Unbelted Index
A positive value indicates
a reduction
in the number of in-
AMERICAN JOURNAL OF EMERGENCY MEDICINE W Volume 9, Number 1 W January 1991
8
TABLE7. Seatbelt Effectiveness Rate (SBER) in Reduction of Number of Injuries by Anatomical
Location and Severity
Severity AIS l-5 No. Inj/N x 100
AIS l-2 Minor
AIS 3-5 Major
Seatbelt
Seatbelt
Seatbelt
Anatomical Location
Yes N, = 23
No N, = 32
SBER
Yes N, = 23
No N, = 32
SBER (“W
Yes N, = 23
No N, = 32
SBER
(“W
Head Face Neck Chest Abdomen Pelvis Extremities Soft tissue
65.2 13.0 13.0 13.0 47.8 17.4 47.8 130.0
93.8 34.4 15.6 68.8 43.8 37.5 91.6 143.8
30.1 62.2 16.7 81.1 -9.1 53.6 47.8 9.6
39.1 13.0 8.7 13.0 21.7 17.4 21.7 126.1
34.4 21.9 6.2 25.0 15.6 25.0 56.2 140.6
-13.7 29.8 -40.3 48.0 - 39.0 30.4 61.3 10.3
26.1 0 4.3 0 26.1 0 26.1 4.3
59.4 12.5 9.4 43.8 28.1 12.5 34.4 3.1
56 100 54 100 7.1 100 24 -38.7
Total
347.8
528.1
34.0
260.9
325.0
20
87.0
200.0
juries and a negative injuries (Table 7).
value an increase
in the number
of
Total Injuries (AISl-5)SBE For total injuries occurring in the belted group, the MIDI was 348 compared with an MIDI of 528 for the unbelted group, yielding a SBE injury reduction in the belted group of 34%. When the numbers of injuries per anatomical location were compared, positive SBE injury reduction was observed in all regions except the abdomen. The abdomen injury index was 9.1 times greater for belted drivers than unbelted drivers. Specific injury reductions were as follows: 81% chest; 62% face; 54% pelvis; 48% extremity; 30% head; 17% neck, and 9.6% soft tissue (Table 7). Minorlnjuty (AIS1-2)SBE For minor injuries in the belted group, the MIDI was 261 compared with an MIDI of 325 for the unbelted group, indicating an SBE reduction in minor injuries in the belted group of 20%. When the numbers of minor injuries per anatomical location were compared, all were reduced except injuries to the head, neck and abdomen. In the belted group, minor injuries to the head increased by 14%; neck injuries by 40%; and abdominal injuries by 39% compared with the unbelted group. Specific minor injury reductions in the belted group were 30% face; 48% chest; 30% pelvis; 61% extremities; and 10% soft tissue injuries (Table 7). MajorInjuries (AIS3-5)SBE For major injuries in the belted group, the MIDI was 87 compared with an MIDI of 203 in the unbelted group, yielding a 57% SBE reduction in major injuries in the belted group. When the numbers of major injuries per anatomical locations were compared, positive SBE in the reduction of injury was observed in all regions except soft tissues. The incidence of soft tissue injuries in the belted group was 39% times greater than in the unbelted group. Specific major injury reduction in the belted group were the following: 100% chest; 100% pelvis; 100% face; 56% head, 54% neck; 24% extremity; and only 7.1% for abdominal injuries (Table 7).
(“/I
57
DISCUSSION This research demonstrates that the majority of drivers involved in serious crashes and admitted to a trauma facility have seatbelt compliance rates similar to those found in the community.” Noncompliant injured drivers have crashes in larger vehicles at greater speeds; they also have higher injury severity scores, use more hospital resources, have longer hospital stays and incur greater costs, and account for more referrals to rehabilitative facilities. Regardless of seatbelt usage, the majority of crashes are frontal, at moderate crash speeds (31 to 55 mph), and occur between 6 PM and 6 AM. Thirty percent of drivers will be alcohol positive, with 70% having alcohol levels greater than 100 mg/dL. The data verify seatbelt effectiveness in reducing the number of serious injuries,3 hospital deaths, and crash scene ejection in a hospital population and establish differences in the use of hospital resources and in hospital costs between seatbeltcompliant and noncompliant injured drivers. The seatbelt usage rate among seriously injured drivers, like the rate among drivers in the community, varies according to a number of parameters (eg, employment, gender, vehicle size and type). Despite mandatory seatbelt usage legislation and close to a 50% compliance rate, serious injuries will continue to occur to occupants of motor vehicles at a considerable cost to society.‘*‘4*1s Severity of injury to seatbelt-compliant drivers depends on crash dynamics, restraint system configuration, and the interaction of the driver with the passenger compartment. Severe injuries can occur to the head, face, neck, pelvis, and extremities despite proper seatbelt tit. l6 Currently designed seatbelt systems allow forward motion of the driver, permit the driver’s knees to contact the instrument panel, and allow the neck to flex and rotate the head and face forward until contact is made with the steering wheel assembly. If seat mountings fail, the lower extremities may be entrapped, crushed, and fractured when the steering wheel assembly moves upward and rearward. If excessive forces are present, these contacts result in a multiple injury syndrome consisting of head, face, and neck injury associated with joint disruption and fractures to the pelvis and
KAPLAN AND COWLEY B SEATBELT COMPLIANCE
lower extremities. 17-2’ If the seatbelt assembly is not worn properly (loosely or under the shoulder girdle), severe injuries to the chest and abdominal regions may occur, as forces are concentrated to these areas.22-24 People will have crashes and serious injuries will occur regardless of fault, socioeconomic factors, or seatbelt compliance rates. 25 If the present trauma epidemic occurring on public roads is to be controlled, and if hospitalization and rehabilitative costs are to be reduced, motor vehicles must be made more crashworthy and occupants protected by the most cost-effective countermeasures available.L*8*9,26 The Federal Motor Vehicle Safety Standard (FMVSS) 208 requires, as standard equipment, the installation of automatic passive restraint systems (seatbelts or airbags) on all new cars manufactured in 1990. The standard does not require testing at crash speeds greater than 30 mph; does not mandate that all vehicles (light trucks, vans) be equipped with restraint systems; and does not require either a failproof automatic restraint system or mandatory installation of both airbags and automatic seatbelt restraint systems.27 The most cost-effective countermeasure device available today is the airbag-seatbelt combination.28-33 Legislative action directed toward the automotive industry is required to mandate these countermeasures as standard safety equipment in all vehicles. In the interim, if seatbelt usage is to be increased, state laws should be enforced and amended to reflect noncompliance of the law as a primary violation with appropriate penalties and negligent clauses.34 If those recommendations had been enacted by legislative bodies 15 years ago, the authors estimate that over 135 billion dollars would have been saved in acute hospital care and rehabilitative costs, and 150,ooO deaths and 1,537,500 brain and spinal injuries could have been prevented.35”8 The time has come for all health care providers to demand these measures be taken. CONCLUSIONS Injured drivers admitted to trauma facilities reflect the seatbelt compliance rate of the community. When worn correctly, seatbelts reduce the total number of injuries by 34% and their severity by 57%. The restraint state affects the use of hospital resources, severity of injury, length of stay, disposition, and overall cost parameters. Seatbelt-compliant drivers had fewer injuries, required less use of hospital resources with shorter hospital stays, and accounted for fewer rehabilitation referrals. This researcher is cognizant of the small sample size limitations with respect to validity and reliability; however, the findings of this study correlate with those documented by Maull, Christian, and DOT.4*‘1,38 It is recommended for future action that pilot study methodology be applied to a larger population for reliability and validity testing, that statutory regulations mandating both airbags and seatbelts for all vehicles become law, that seatbelt noncompliance laws be enforced and strengthened, and that seatbelt education prevention programs be designed for specific age and gender groups. The authors thank Ellen Doyle, RN, certified emergency nurse, for her help in the manuscript preparations. They are also grateful for the contributions made by the medical students rotating through our institution and the prehospital care providers in the
9
State of Maryland, without whose cooperation
and efforts this study could not have been accomplished, and to Frances Cipriotti for the many hours devoted to manuscript preparation.
REFERENCES 1. Ziperman HH, Cromade JP, Clark JM: Airbags and seatbelts in injury amelioration. J Trauma 1986;16:686-693 2. Bohlin Nl: Statistical analysis of 28,000 accident cases with emphasis on occupant restraint value. Report of the Proceedings of the Stapp Car Crash Conference (Paper #670925), 1967 3. Campbell J: Safety belt injury reduction related to crash severity and front seated position. J Trauma 1987;27:733-739 4. Christian MD: Morbidity and mortality of car occupants: Comparative survey over 24 months. Br Med J 1984;289:15251526 5. American College of Preventive Medicine: Prevention of Motor Vehicle Trauma. Washington, DC, US Department of Transportation, 1986 6. Committee on Trauma Research, National Research Council: Injury in America: A Continuing Public Health Problem. Washington, DC, National Academy Press, 1985 7. Austin RH: Political risk assessment, from an elected safety belt law advocate’s point of view and experience. J Trauma 1987;27:719-725 8. Sleet D: Motor vehicle trauma and safety belt use in the context of public health priorities. J Trauma 1987;27:695-702 9. Withers B, Baker S: Epidemiology and prevention of injuries. Emerg Clin North Am 1984;2:4 10. Petrucelli E: Seatbelt laws: The New York ExperiencePreliminary data and some observations. J Trauma 1987;27:706710 11. US Department of Transportation, Restraint System Usage in the Traffic Population, DOT HS 342, 1987 Annual Report, 1988 12. Gurin DB: Over representation of safety belt non-users in North Carolina traffic crashes: Research notes. NHSTA. DOT. 1989 13. American Association for Automotive Medicine: The Abbreviated Injury Scale, 1985 14. Orsay EM, et al: Prospective study of the effect of safety belts on mortality and health care: Cost in motor vehicle accidents. JAMA 1988;260:3598-3601 15. MacKenzie EJ, Shapiro S, Siegel JH: The economic impact of traumatic injuries. JAMA 1988;260:22 16. MacKay M: Kinematics of vehicle crashes. In Advances in Trauma, vol 2. Chicago, IL, Year Book, 1987, pp 21-42 17. Gallup B, Newman JA: The assessment of facial injury and fully restrained drivers through full-scale car crash testing. J Trauma 1987;27:711-718 18. Borgqvist D, Hedeliz H: Roll seatbelt induced injury of the duodenum. J Trauma 1976;16:390-394 19. Morton J, Jordan G: Traumatic duodenal injuries: Review of 131 cases. J Trauma 1986;8:127-139 20. Myers J, Schmidt C, Kraft R: An unusual seatbelt injury case report. J Trauma 1972;12:529-533 21. Porter S, Green E: Seatbelt injuries. Arch Surg 1968; 96:242-246 22. States JD, et al: Fatal injuries caused by underarm use of shoulder belts. J Trauma 1987;27:740-745 23. Williams J, Kirkpatrick J: The nature of seatbelt injuries. J Trauma 1971 ;11:207-218 24. Williams J, Lies B, Hale H: The automotive safety belt: In saving a life may produce intraabdominal injuries. J Trauma 1966;6:303-315 25. US Department of Transportation, Fatal Accident Reporting System, National Highway Traffic Safety Administration, Annual Report, 1987 26. Hames LN: Airbags. JAMA 1970;214:1109 27. Insurance Institute for Highway Safety: Airbags and belts: 20 years of rulemaking activity and litigation. 1987:22:12-13 28. States JD: Airbags: Some myths dispelled. J Trauma 1972;12:178
10
AMERICAN JOURNAL OF EMERGENCY MEDICINE n Volume 9, Number 1 H January 1991
29. Haddon W: Options for the prevention of motor vehicle crash injury conference and the prevention of motor vehicle crash injuries, Ben Gurion University, Beershebas, Israel. Isr J Med Sci 1980;18:45 30. Clark CC: Rollover crash and laboratory tests of ejection reduction by basic-plastic side windows and wind shields. Technical paper SAE 89OD18, SAE International Conference, Logo Hill, Detroit, MI, 1989 31. States JD: The prevention of injury secondary to motor vehicle accidents. Clin Or-thop 1987;222:21-29 32. Williams AF, Lund AK: Seatbeit use laws and occupant crash protection in the United States. Am J Public Health 1986;76:1438-1442 33. Williams JS: The nature of seatbelt injuries. Report of the
Proceedinas of the Staoo Car Crash Conference. .~(Paoer . #700896) 1970 34. Marburger EA, Friedel B: Seatbelt legislation and seatbelt effectiveness in the Federal Republic of Germany. J Trauma 1987;27:703-705 35. Jagger J, Vernbergk JA: Airbags: Reducing the toll of brain trauma. Neurosuraerv 1987:20:815-817 36. Lipe HP: Prevention of nervous system trauma from travel in motor vehicles. J Neurosurg Nurs 1985;17:77-82 37. McGuire A: Issues in the prevention of neurotrauma. Nurs Clin North Am 1986;24:549-554 38. Reath DB, Kirby JK, Lynch M, Maul1 Kl: Injury and cost comparison of restrained and unrestrained motor vehicle crash victims. American Association for the Surgery of Trauma, 48th Annual Meeting, 1988, p 130
The effectiveness of restraint systems in reducing fatal outcomes and severity of injury in motor vehicle occupants injured in crashes is well documented.“4 The National Highway Traffic Safety Administration (NHTSA) estimates that, for every 10% increase in belt use, 1,500 deaths will be prevented, 30,000 moderate-to-serious injuries will be reduced, and 600 to 800 million dollars will be saved annually.5 In 1974, standards promulgated by the Department of Transportration (DOT) required that all passenger vehicles manufactured be equipped with a combination lap and shoulder restraint system. Between 1974 and 1985, national voluntary seatbelt usage rates were approximately 12% and, in Maryland, less than 20% in 1985, despite multiple educational programs aimed toward increasing voluntary use by the public.6 From 1981 to 1984, the requirement for all passenger vehicles manufactured to have “automatic passive restraint systems” was debated and a compromise was made between the automobile manufacturers and DOT.’ Manufacturers would not be required to equip passenger vehicles with automatic passive restraint systems if mandatory state seatbelt legislation would encompass two thirds of the United States population. As of 1987, seatbelt usage legislation has been enacted in 31 states and the District of Columbia; 16 states are in the process of enacting legislation and 2 have repealed From the Maryland Institute for Emergency Medical Services Systems, Baltimore, MD. Manuscript received October 30,1989; revision accepted April 1, 1990. Address reprint requests to Dr. Kaplan: 9318-B Sable Ridge Circle, Boca Raton, FL 33428. Key Words: Seatbelts, trauma, hospital costs. Copyright 0 1991 by W.B. Saunders Company 07356757/91/0901-0002$5.00/O 4
their laws. Usage is influenced by mandatory seatbelt usage laws, enforcement policies, penalties incurred as a result of violating the law, and various educational programs informing the public as to the risks-benefits of seatbelt restraints.‘-” Nationally, mandatory seatbelt usage laws have increased usage from a low of 12% to 46%, with a range of 28.9% to 67.8%.” In states with seatbelt laws, the reduction in motor vehicle fatalities and injuries has not been so great as predicted from observed belt usage rates and the estimated protection of belts in crashes.‘* This observation and the enactment of mandatory seatbelt legislation in Maryland, effective July 1, 1986, afforded the opportunity to study this program and identify the reasons for these differences. A pilot study was designed to determine seatbelt effectiveness in reducing injury and to determine the cost of seatbelt noncompliance among a sample of injured drivers admitted to the Shock Trauma Center of the Maryland Institute for Emergency Medical Services Systems (MIEMSS). MATERIAL AND METHODS
The study was limited to drivers of passenger cars, vans, and light trucks, who were injured as a result of collision with another vehicle or fixed object, rollover, or rear-end collision and directly admitted to the MIEMSS Shock Trauma Center between July 1, 1986 and June 30. 1987. Crash, hospital admission, and disposition data were collected prospectively by senior medical students randomly assigned to one of four trauma teams. These data consisted of demographic information, time of crash, estimated crash speed, type of impact, type and size of vehicle, and restraint status. Medical students contacted the on-scene prehospital care provider within 24 hours to determine restraint status and crash data. Admission data consisted of alcohol levels, admission time, number and types of injuries, and disposition. The hospital course data were collected retrospectivelyl from medical records and consisted of number and severity of injuries, length of stay (LOS), and discharge disposition. Injury severity scores (ISS) were calculated by the author [Kaplan], according to the 1985 revision of the Abbreviated Injury Scale of the American Association for Automotive Medicine. l3 Hospital charges were supplied by the Financial Officer of MIEMSS, and professional fees by the Shock Trauma Associate Physicians Office. Parametric and nonparametric statistical tests were used for data analysis. RESULTS Study Population Description
Demographic information for the 55 subjects is presented in Table 1. Ages ranged from 16 to 76, with a mean of 32
KAPLAN AND COWLEY n SEATBELT COMPLIANCE
5
TABLE1. Population Characteristics and Seatbelt Compliance Rate (SBCR) Parameter Gender Race
Age (yr) Employment
Alcohol use Month of crash Vehicle type
Male Female White Black Asian 30 Yes No Retired Unknown Yes No July-December 1986 JanuaryJune 1987 Auto Van Light truck
N (%)
SBCR (%)
34 (62) 21 (38) 46 (84) 7 (13) 2 (4) 29 (53) 26 (47) 38 (69) 7 (13) 3 (5) 7 (15) 17 (31) 38 (69) 13 (24) 42 (76) 48 (87) 3 (5) 4 (7)
44 38 39 43 100 52 31 37 28 33 88 35 45 54 38 42 67 25
years. Seventeen drivers (31%) were alcohol positive on admission; 12 (71%) of them had alcohol levels above 100 mg/ dL. Forty-eight subjects drove cars (87.3%), three drove vans (5.40/o), and four drove light trucks (7.3%); 27 of the car drivers operated small or mid-sized vehicles (wheel base size cl09 inches) at the time of crash (Table 2). Collisions occurred mostly between 6 PM and midnight, accounting for 44% (24) of all crashes. The overall seatbelt compliance rate (SBCR) was 41.8%. The SBCR was greater from July through December 1986 (54%) than from January through June 1987 (38%). A total of 249 injuries were distributed among the 55 subjects, with an average of 4.53 injuries per subject. There were 164 (66%) AIS l-2 type injuries (minor) and 85 (34%) AIS 3-5 type injuries (major). The average number of minor injuries was 2.98 per subject and, for major injuries, 1.54 per subject (Table 3). Multiple injuries occurred within the study population. The most commonly recorded anatomical region of injury was the head (71%), followed by soft tissue (39%), extremities (38%), chest (33%), pelvis (24%), face (22%), abdomen (18%), and neck (11%). The ISS associated with these anatomical regions ranged from 1 to 66, with a mean of 14.2. The LOS ranged from 1 day to 110 days (mean, 13.5 days). The mean hospital cost was $30,719, with a range of $1,989 to $217,606 (Table 4). On arrival at the trauma facility, 24 subjects were admitted directly to the operating room (OR) (44%), 6 to the critical care recovery unit (CCRU) (ll%), 12 to the intensive care unit (ICU) (22%), and 13 to the general care unit (24%) (Table 5). The majority of the study population, 41 (710/o), were discharged home. Following their hospital course, 10 (18%) required rehabilitative facilities. Four patients expired (7.3%) (Table 6). Characteristics of Belted Subjects There were 23 seatbelt-compliant subjects: 15 males (10 white, 3 black, 2 Asian) and 8 females (white). Their mean
age was 30.4, with a range of 19 to 58 years, 66% (15) of these belted drivers were between the ages of 19 and 29 and 35% (8) were between age 30 and 50. Fourteen were employed, 2 were unemployed or students, 1 was retired, and the employment status of six was unknown. Within this group, 26% (6) were alcohol-positive drivers, three of whom had levels greater than 100 mg/dL, ranging from 154 to 167 mg/dL. The mean age of these alcohol-positive drivers was 22.2 years, with a range of 20 to 24 years. Thirty-nine percent (9) drove small vehicles (wheel base ~99 inches), 26% (6) drove mid-size vehicles, and 13% (3) large vehicles. The vehicle size was unknown for 22% (5) of this group. Seventy-eight percent (18) of belted drivers crashed between 6 PM and 6 AM, 52% (12) between 6 PM and midnight, and 22% (5) between 6 AM and 6 PM. Of the 23 collisions among belted drivers, 74% (17) were frontal impact, 13% (3) side impact, 9% (2) rollover, and 4% (1) rear-end impact. Estimated crash speed determinations were 3 1 to 55 mph for 61% (14) of crashes involving belted drivers and less than or equal to 30 mph in 39% (9). Seven of the belted driver crashes occurred between July and December 1986, and 16 between January and June 1987. Belted Group Injuries Among the 23 belted drivers, there were a total of 80 injuries, averaging 3.4 injuries per driver. Three-fourths (60) were minor injuries (AIS l-2) and one-fourth (20) major injuries (AIS 3-5). The average number of major injuries per driver was 0.87. The nine collisions occurring at less than or equal to 30 mph resulted in 28 injuries, representing 35% of the total belted group injuries; 71% (20) of the injuries were minor and 29% (8) were major. The total injury distribution for this subgroup was 3.1 injuries per driver: 2.2 injuries per driver for minor and 0.89 for major injuries. For crash speeds greater than 30 mph there were 52 injuries, representing 65% of the total injuries in the belted group; 77% (40) were minor TABLE2. Vehicle Characteristics and Seatbelt Compliance Rate Parameter Vehicle (wheel base in inches) Small (c99) Mid (100-109) Large (>109 Unknown Crash time 6 AM-~ PM 6 PM-midnight midnight-6 AM Crash speed (mph) 930 31-55 >55 Unknown Ejections Crash vector Frontal Multiple Side Rear Rollover Unknown
N (%)
SBCR (%)
12 (22) 15 (27) 11 (20) 27 (31)
75 40 27 29
14 (25) 24 (44) 17 (31)
36 50 35
13 (24) 31 (56) 9 (16) 2 (4) 5 (100)
69 47 0 0 0
34 (62) 1 (2) 12 (22) 2 (4) 4 (7) 2 (4)
50 0 17 50 50 0
AMERICAN JOURNAL OF EMERGENCY MEDICINE I Volume 9, Number 1 n January 1991
6
TABLE3. Injury Severity Score, Injuries, and Seatbelt Compliance Rates (SBCR) by Speed and Impact Site No. of Injuries
Crash Speed (mph) ISS
N (%)
Impact
Belted
s30
>30
u
F/M
S
0
U
Yes (%)
l-09 lo-19 20-29 30-39 c40
23 (42) 13 (24) 10 (16) 5 (9) 4 (7)
7 3 2 1 -
16 10 6 4 4
2 -
14 7 7 2 3
7 2 1 1 -
1 2 2 1 -
1 2 1 1
36 (45) 24 (30) 20 (25) -
Total
55(100)
13
40
2
33
11
6
5
60 (1200)
ABBREVIATIONS:
U, unknown; F/M, frontal/multiple;
Total (%)
SBCR (%)
36 (21) 36 (22) 26 (17) 29 (22) 36 (16)
72 (29) 62 (25) 48 (19) 29 (12) 36 (15)
56.5 42.6 40.0 0 0
169 (100)
249 (100)
41.6
S, side; 0, other.
and 33% (12) were major. The total injury distribution in this subgroup was 3.7 injuries per driver: 2.86 for minor and 0.86 for major injuries. The most commonly recorded anatomical regions of injury for the belted group were soft tissue (74%), head (65%), extremities (22%), pelvis (17%), abdomen (13%), chest (13%), neck (14%), and face (9%). The ISS associated with these ranged from 1 to 29, with a mean of 10.8. The mean ISS at crash speeds less than or equal to 30 mph was 9.8, which increased to a mean of 11.4 with crash speeds greater than 30 mph (Tables 3 and 4). The mean ISS of the alcohol-positive belted drivers was 10.8, with a range of 5 to 20. The LOS ranged from 1 to 32 days (mean, 10.8 days). For crash speeds less than or equal to 30 mph, the LOS ranged from 1 to 24 days, with a mean of 9.2; for crash speeds greater than 30 mph the LOS ranged from 1 to 32 days, with a mean of 10.5. For alcohol-positive belted drivers, the mean LOS was 10.8, with a range of 1 to 24 days. The mean hospital cost for belted drivers was $19,414 (range, $2,055 to $57,942). Of the 23 seatbelt-compliant drivers admitted to the trauma facility, 44% (10) were admitted directly to the OR; 4% (1) directly to the CCRU: 22% (5) directly to the ICU; and 31% (7) directly to the general care unit. The mean ISS and mean LOS for direct OR admissions were 13.6 and 16.2, respectively; for the CCRU, 9 and 12, respectively; for ICU admission, 4.2 and 4.4, respectively; and for the general care unit, 3.3 and 4.9, respectively (Table 5). The belted group had a 91.3% (21) disposition to home, and 9.5% (2) went to a rehabilitation facility (both from crashes greater than 30 mph). All of the belted, injured, alcohol-positive patients were discharged home. There were no deaths (Table 6) or ejections among the seatbelt population.
TABLE4. Number of Injuries; Average Injuries per Driver; Mean ISS, LOS, and Cost According to Restraint State Seatbelt Yes (N = 23)
No (N = 32)
Total (N = 55)
Significance
Injuries/driver Mean ISS Mean LOS Mean cost
3.4 10.6 10.6 $19,414
5.3 22.9 17.0 $38,845
4.5 14.2 13.5 $30,719
P < .0005 P < .0005 P< .l P -=z.025
ABBREVIATIONS:
ISS, injury severity score; LOS, length of stay.
Variable
No (%)
Characteristics
of the Unbelted
Subjects
Thirty-two subjects were not wearing seatbelts at the time of their crash: 19 males (17 white, 2 black) and 13 females (11 white, 2 black). The mean age was 34.1 years, with a range of 16 to 76 years; 44% of the unbelted drivers were between the ages of 16 and 29; 56% were aged 30 to 76. Twenty-four were employed, 5 were unemployed or students, 2 were retired, and 1 had an unknown employment status. Within this group, 34% (11) were alcohol-positive drivers, 73% (8) of whom had levels higher than 100 mg/dL, ranging from 115 to 333 mg/dL. The mean age of the alcohol-positive drivers was 21.4 years, with a range of 1 to 45 years. Nine percent (3) operated small vehicles; 28% (9) operated medium-sized vehicles; and 25% (8) large vehicles. The vehicle size was not reported for 38% (12) of this group. Seventy-two percent (23) of the unbelted drivers crashed between 6 PM and 6 AM; 38% (12) of these crashes occurred between 6 PM and midnight and 28% (9) between 6 AM and 6 PM. Of the 32 collisions in this group, 53% (17) were frontal impact, 31% (10) side impacts, 6% (2) rollover, 3% (1) rearend impact, and 6% (2) unknown impact direction. Fifteen percent (5) of the unbelted drivers were ejected from their vehicle during the crash sequence: 2 from rollovers, 2 from frontal collisions, and 1 in an unknown type of impact. Estimated crash speed determinations were 31 to 55 mph for 53% (17), greater than 55 mph for 28% (9). and less than or equal to 30 mph for 12% (4). The crash speed was unknown for 6% (2). Six of the 32 unbelted driver crashes occurred between July and December 1986, and 26 between January and June 1987. The 32 unbelted drivers had a total of 169 injuries, averaging 5.3 injuries per driver. Sixty-two percent (104) were minor injuries and 38% (65) were major injuries (Table 3). Minor injuries averaged 3.25 per driver, and major injuries averaged 2.03 per driver. Collisions occurring at 30 mph or less (4) resulted in 14 injuries, representing 8% of the total injuries in the unbelted group (78% [ll] minor and 22% [3] major). The total injury distribution for this subgroup was 3.5 injuries per driver: 2.75 for minor and 0.75 for major injuries. In the 15 crashes between 31 and 55 mph, there were 77 injuries, representing 46% of the total injuries in the unbelted group; 7% (61) were minor and 21% (16) were major injuries. The total injury distribution for crash speeds between 31 and 55 mph was 5.1 injuries per driver: minor, 4.1, and major, 1.1 per driver. For crashes (8) at greater than 55 mph,
KAPLAN AND COWLEY n SEATBELT COMPLIANCE
7
TABLE 5. Admission Disposition vs Restraint State with Mean ISS and LOS Seatbelt Yes
No
Admission Unit
N,
ISS
LOS
N2
ISS
LOS
Total: N, + N2 (%)
OR CCRU ICU Ward
10 1 5 7
13.6 9.0 4.2 3.3
16.2 12.0 4.4 4.9
14 5 7 6
31.5 17.6 6.7 3.6
25.7 16.6 5.4 3.6
24 (44) 6(11) 12 (22) 13 (24)
42 17 42 54
Total
23
10.6
10.0
32
22.9
17.0
55
41.6
SBCR (%)
ABBREVIATIONS: SBCR, seatbelt compliance rate; ISS, injury severity score; LOS, length of stay; OR, operating room; CCRU, critical care recovery unit; ICU, intensive care unit.
there were 49 injuries, representing 29% of the total injuries in the unbelted group; 39% (19) were minor and 61% (30) were major. The total injury distribution for this subgroup was 6.1 injuries per driver: 2.4 for minor and 3.7 for major injuries. There were 29 injuries (representing 17% of the total injuries in the unbelted group) associated with 5 ejection-type crashes: 2 rollovers (1 at 85 mph), 2 frontal (1 at 45 mph), and 1 unknown type. In this subgroup, 45% (13) were minor and 55% (16) major injuries. The total injury distribution for drivers crashing and being ejected was 5.8 injuries per person: 2.6 for minor and 3.2 for major injuries. The most commonly recorded anatomical regions of injury for the unbelted drivers were head (75%), soft tissue (69%), extremities (50%), chest (47%), face (31%), pelvis (28%), abdomen (22%), and neck (9%). The ISS associated with these regions ranged from 1 to 66, with a mean of 22.9. The mean ISS of unbelted drivers with crash speed less than or equal to 30 mph was 16.0; for crash speeds between 31 and 55 mph, the mean ISS was also 16.0; for crash speeds in excess of 55 mph, the mean ISS was 32.9. The ejected drivers’ mean ISS was 33.0. The mean ISS of the 11 alcoholpositive drivers was 14.2, with a range of 5 to 54. The mean hospital cost for the unbelted driver was $38,845, with a range of $1,989 to $217,606 (Table 4). The LOS for’unbelted drivers ranged from 1 to 110 days, with a mean of 17 days. For crash speeds less than 30 mph, the mean LOS was 9 days; for crash speeds between 3 1 and 55 mph, 18.1 days; for crash speeds greater than 55 mph, 17.8 days. Of the 32 unbelted drivers admitted to the trauma facility, 44% (14) were admitted directly to the OR, 15% (5) directly to the CCRU, 22% (7) directly to the ICU, and 19% (6)
TABLE6. Hospital Disposition on Discharge According to Seatbelt Compliance Rate (SBCR) Seatbelt Discharge Disposition
Yes N (%)
Home Rehabilitation Morgue
21 (91.3) 2 (9.5) 6 (6)
20 (62.5) 6 (25.0) 4 (12.5)
41 (74) 10 (16) 4 (7.3)
51 25 0
Total
23
32
55
41.8
NY;,
Total N (%)
SBCR (%)
directly to the general care unit. The mean ISS and mean LOS for direct OR admissions were 31.5 and 25.7, respectively; for the CCRU admissions, 17.6 and 18.6, respectively; for the ICU admissions, 6.7 and 5.4, respectively; and for the general care unit, 3.6 and 3.6, respectively (Table 5). The unbelted group had a 62.5% (20) home discharge rate and 25% (8) required rehabilitative services at another facility. Of the 11 unbelted, injured, alcohol-positive drivers, 45% (5) were discharged home and 55% (6) required rehabilitative services at another facility. Four patients expired in the unbelted group, yielding a mortality rate of 12.5% (Table 6); three died from head injuries and one from multiple organ failure. Two of the fatalities had frontal collisions at crash speeds greater than 55 mph (ISS, 66; LOS, 1 and 23 days); one was ejected in a frontal collision at a crash speed of 45 mph (ISS, 38; LOS, 18 days). Seatbelt
Effectiveness
(SEE)
For the purpose of this study, seatbelt effectiveness is defined as a measure of a restraining device’s performance in reducing both the number and severity of injuries resulting from motor vehicle crashes. To facilitate the comparison of seatbelt effectiveness between the two subgroups (belted and unbelted drivers) of the study population, a Multiple Injury Distribution Index (MIDI) was developed. This index represents the total number of injuries occurring within the subgroup equally distributed to all subjects within their respective subgroup. The derived number was then multiplied by 100 to reflect the number of injuries expected to occur in a population base of 100 individuals. For example, the 23 victims in the belted group had a total of 80 injuries, 15 of which were to the head region. This equalled 3.48 injuries per individual, or an MIDI of 348 injuries per 100 belted drivers, and 0.652 head injuries per individual, or an MIDI for head injuries of 65.2 per 100 belted drivers (Table 7). The MIDI was calculated for both subgroups (belted and unbelted) and for their respective anatomical regions. The magnitude and direction of the seatbelt effectiveness rate (SBER) was then derived as follows: SBER =
Unbelted
Index - Belted Index x 100 Unbelted Index
A positive value indicates
a reduction
in the number of in-
AMERICAN JOURNAL OF EMERGENCY MEDICINE W Volume 9, Number 1 W January 1991
8
TABLE7. Seatbelt Effectiveness Rate (SBER) in Reduction of Number of Injuries by Anatomical
Location and Severity
Severity AIS l-5 No. Inj/N x 100
AIS l-2 Minor
AIS 3-5 Major
Seatbelt
Seatbelt
Seatbelt
Anatomical Location
Yes N, = 23
No N, = 32
SBER
Yes N, = 23
No N, = 32
SBER (“W
Yes N, = 23
No N, = 32
SBER
(“W
Head Face Neck Chest Abdomen Pelvis Extremities Soft tissue
65.2 13.0 13.0 13.0 47.8 17.4 47.8 130.0
93.8 34.4 15.6 68.8 43.8 37.5 91.6 143.8
30.1 62.2 16.7 81.1 -9.1 53.6 47.8 9.6
39.1 13.0 8.7 13.0 21.7 17.4 21.7 126.1
34.4 21.9 6.2 25.0 15.6 25.0 56.2 140.6
-13.7 29.8 -40.3 48.0 - 39.0 30.4 61.3 10.3
26.1 0 4.3 0 26.1 0 26.1 4.3
59.4 12.5 9.4 43.8 28.1 12.5 34.4 3.1
56 100 54 100 7.1 100 24 -38.7
Total
347.8
528.1
34.0
260.9
325.0
20
87.0
200.0
juries and a negative injuries (Table 7).
value an increase
in the number
of
Total Injuries (AISl-5)SBE For total injuries occurring in the belted group, the MIDI was 348 compared with an MIDI of 528 for the unbelted group, yielding a SBE injury reduction in the belted group of 34%. When the numbers of injuries per anatomical location were compared, positive SBE injury reduction was observed in all regions except the abdomen. The abdomen injury index was 9.1 times greater for belted drivers than unbelted drivers. Specific injury reductions were as follows: 81% chest; 62% face; 54% pelvis; 48% extremity; 30% head; 17% neck, and 9.6% soft tissue (Table 7). Minorlnjuty (AIS1-2)SBE For minor injuries in the belted group, the MIDI was 261 compared with an MIDI of 325 for the unbelted group, indicating an SBE reduction in minor injuries in the belted group of 20%. When the numbers of minor injuries per anatomical location were compared, all were reduced except injuries to the head, neck and abdomen. In the belted group, minor injuries to the head increased by 14%; neck injuries by 40%; and abdominal injuries by 39% compared with the unbelted group. Specific minor injury reductions in the belted group were 30% face; 48% chest; 30% pelvis; 61% extremities; and 10% soft tissue injuries (Table 7). MajorInjuries (AIS3-5)SBE For major injuries in the belted group, the MIDI was 87 compared with an MIDI of 203 in the unbelted group, yielding a 57% SBE reduction in major injuries in the belted group. When the numbers of major injuries per anatomical locations were compared, positive SBE in the reduction of injury was observed in all regions except soft tissues. The incidence of soft tissue injuries in the belted group was 39% times greater than in the unbelted group. Specific major injury reduction in the belted group were the following: 100% chest; 100% pelvis; 100% face; 56% head, 54% neck; 24% extremity; and only 7.1% for abdominal injuries (Table 7).
(“/I
57
DISCUSSION This research demonstrates that the majority of drivers involved in serious crashes and admitted to a trauma facility have seatbelt compliance rates similar to those found in the community.” Noncompliant injured drivers have crashes in larger vehicles at greater speeds; they also have higher injury severity scores, use more hospital resources, have longer hospital stays and incur greater costs, and account for more referrals to rehabilitative facilities. Regardless of seatbelt usage, the majority of crashes are frontal, at moderate crash speeds (31 to 55 mph), and occur between 6 PM and 6 AM. Thirty percent of drivers will be alcohol positive, with 70% having alcohol levels greater than 100 mg/dL. The data verify seatbelt effectiveness in reducing the number of serious injuries,3 hospital deaths, and crash scene ejection in a hospital population and establish differences in the use of hospital resources and in hospital costs between seatbeltcompliant and noncompliant injured drivers. The seatbelt usage rate among seriously injured drivers, like the rate among drivers in the community, varies according to a number of parameters (eg, employment, gender, vehicle size and type). Despite mandatory seatbelt usage legislation and close to a 50% compliance rate, serious injuries will continue to occur to occupants of motor vehicles at a considerable cost to society.‘*‘4*1s Severity of injury to seatbelt-compliant drivers depends on crash dynamics, restraint system configuration, and the interaction of the driver with the passenger compartment. Severe injuries can occur to the head, face, neck, pelvis, and extremities despite proper seatbelt tit. l6 Currently designed seatbelt systems allow forward motion of the driver, permit the driver’s knees to contact the instrument panel, and allow the neck to flex and rotate the head and face forward until contact is made with the steering wheel assembly. If seat mountings fail, the lower extremities may be entrapped, crushed, and fractured when the steering wheel assembly moves upward and rearward. If excessive forces are present, these contacts result in a multiple injury syndrome consisting of head, face, and neck injury associated with joint disruption and fractures to the pelvis and
KAPLAN AND COWLEY B SEATBELT COMPLIANCE
lower extremities. 17-2’ If the seatbelt assembly is not worn properly (loosely or under the shoulder girdle), severe injuries to the chest and abdominal regions may occur, as forces are concentrated to these areas.22-24 People will have crashes and serious injuries will occur regardless of fault, socioeconomic factors, or seatbelt compliance rates. 25 If the present trauma epidemic occurring on public roads is to be controlled, and if hospitalization and rehabilitative costs are to be reduced, motor vehicles must be made more crashworthy and occupants protected by the most cost-effective countermeasures available.L*8*9,26 The Federal Motor Vehicle Safety Standard (FMVSS) 208 requires, as standard equipment, the installation of automatic passive restraint systems (seatbelts or airbags) on all new cars manufactured in 1990. The standard does not require testing at crash speeds greater than 30 mph; does not mandate that all vehicles (light trucks, vans) be equipped with restraint systems; and does not require either a failproof automatic restraint system or mandatory installation of both airbags and automatic seatbelt restraint systems.27 The most cost-effective countermeasure device available today is the airbag-seatbelt combination.28-33 Legislative action directed toward the automotive industry is required to mandate these countermeasures as standard safety equipment in all vehicles. In the interim, if seatbelt usage is to be increased, state laws should be enforced and amended to reflect noncompliance of the law as a primary violation with appropriate penalties and negligent clauses.34 If those recommendations had been enacted by legislative bodies 15 years ago, the authors estimate that over 135 billion dollars would have been saved in acute hospital care and rehabilitative costs, and 150,ooO deaths and 1,537,500 brain and spinal injuries could have been prevented.35”8 The time has come for all health care providers to demand these measures be taken. CONCLUSIONS Injured drivers admitted to trauma facilities reflect the seatbelt compliance rate of the community. When worn correctly, seatbelts reduce the total number of injuries by 34% and their severity by 57%. The restraint state affects the use of hospital resources, severity of injury, length of stay, disposition, and overall cost parameters. Seatbelt-compliant drivers had fewer injuries, required less use of hospital resources with shorter hospital stays, and accounted for fewer rehabilitation referrals. This researcher is cognizant of the small sample size limitations with respect to validity and reliability; however, the findings of this study correlate with those documented by Maull, Christian, and DOT.4*‘1,38 It is recommended for future action that pilot study methodology be applied to a larger population for reliability and validity testing, that statutory regulations mandating both airbags and seatbelts for all vehicles become law, that seatbelt noncompliance laws be enforced and strengthened, and that seatbelt education prevention programs be designed for specific age and gender groups. The authors thank Ellen Doyle, RN, certified emergency nurse, for her help in the manuscript preparations. They are also grateful for the contributions made by the medical students rotating through our institution and the prehospital care providers in the
9
State of Maryland, without whose cooperation
and efforts this study could not have been accomplished, and to Frances Cipriotti for the many hours devoted to manuscript preparation.
REFERENCES 1. Ziperman HH, Cromade JP, Clark JM: Airbags and seatbelts in injury amelioration. J Trauma 1986;16:686-693 2. Bohlin Nl: Statistical analysis of 28,000 accident cases with emphasis on occupant restraint value. Report of the Proceedings of the Stapp Car Crash Conference (Paper #670925), 1967 3. Campbell J: Safety belt injury reduction related to crash severity and front seated position. J Trauma 1987;27:733-739 4. Christian MD: Morbidity and mortality of car occupants: Comparative survey over 24 months. Br Med J 1984;289:15251526 5. American College of Preventive Medicine: Prevention of Motor Vehicle Trauma. Washington, DC, US Department of Transportation, 1986 6. Committee on Trauma Research, National Research Council: Injury in America: A Continuing Public Health Problem. Washington, DC, National Academy Press, 1985 7. Austin RH: Political risk assessment, from an elected safety belt law advocate’s point of view and experience. J Trauma 1987;27:719-725 8. Sleet D: Motor vehicle trauma and safety belt use in the context of public health priorities. J Trauma 1987;27:695-702 9. Withers B, Baker S: Epidemiology and prevention of injuries. Emerg Clin North Am 1984;2:4 10. Petrucelli E: Seatbelt laws: The New York ExperiencePreliminary data and some observations. J Trauma 1987;27:706710 11. US Department of Transportation, Restraint System Usage in the Traffic Population, DOT HS 342, 1987 Annual Report, 1988 12. Gurin DB: Over representation of safety belt non-users in North Carolina traffic crashes: Research notes. NHSTA. DOT. 1989 13. American Association for Automotive Medicine: The Abbreviated Injury Scale, 1985 14. Orsay EM, et al: Prospective study of the effect of safety belts on mortality and health care: Cost in motor vehicle accidents. JAMA 1988;260:3598-3601 15. MacKenzie EJ, Shapiro S, Siegel JH: The economic impact of traumatic injuries. JAMA 1988;260:22 16. MacKay M: Kinematics of vehicle crashes. In Advances in Trauma, vol 2. Chicago, IL, Year Book, 1987, pp 21-42 17. Gallup B, Newman JA: The assessment of facial injury and fully restrained drivers through full-scale car crash testing. J Trauma 1987;27:711-718 18. Borgqvist D, Hedeliz H: Roll seatbelt induced injury of the duodenum. J Trauma 1976;16:390-394 19. Morton J, Jordan G: Traumatic duodenal injuries: Review of 131 cases. J Trauma 1986;8:127-139 20. Myers J, Schmidt C, Kraft R: An unusual seatbelt injury case report. J Trauma 1972;12:529-533 21. Porter S, Green E: Seatbelt injuries. Arch Surg 1968; 96:242-246 22. States JD, et al: Fatal injuries caused by underarm use of shoulder belts. J Trauma 1987;27:740-745 23. Williams J, Kirkpatrick J: The nature of seatbelt injuries. J Trauma 1971 ;11:207-218 24. Williams J, Lies B, Hale H: The automotive safety belt: In saving a life may produce intraabdominal injuries. J Trauma 1966;6:303-315 25. US Department of Transportation, Fatal Accident Reporting System, National Highway Traffic Safety Administration, Annual Report, 1987 26. Hames LN: Airbags. JAMA 1970;214:1109 27. Insurance Institute for Highway Safety: Airbags and belts: 20 years of rulemaking activity and litigation. 1987:22:12-13 28. States JD: Airbags: Some myths dispelled. J Trauma 1972;12:178
10
AMERICAN JOURNAL OF EMERGENCY MEDICINE n Volume 9, Number 1 H January 1991
29. Haddon W: Options for the prevention of motor vehicle crash injury conference and the prevention of motor vehicle crash injuries, Ben Gurion University, Beershebas, Israel. Isr J Med Sci 1980;18:45 30. Clark CC: Rollover crash and laboratory tests of ejection reduction by basic-plastic side windows and wind shields. Technical paper SAE 89OD18, SAE International Conference, Logo Hill, Detroit, MI, 1989 31. States JD: The prevention of injury secondary to motor vehicle accidents. Clin Or-thop 1987;222:21-29 32. Williams AF, Lund AK: Seatbeit use laws and occupant crash protection in the United States. Am J Public Health 1986;76:1438-1442 33. Williams JS: The nature of seatbelt injuries. Report of the
Proceedinas of the Staoo Car Crash Conference. .~(Paoer . #700896) 1970 34. Marburger EA, Friedel B: Seatbelt legislation and seatbelt effectiveness in the Federal Republic of Germany. J Trauma 1987;27:703-705 35. Jagger J, Vernbergk JA: Airbags: Reducing the toll of brain trauma. Neurosuraerv 1987:20:815-817 36. Lipe HP: Prevention of nervous system trauma from travel in motor vehicles. J Neurosurg Nurs 1985;17:77-82 37. McGuire A: Issues in the prevention of neurotrauma. Nurs Clin North Am 1986;24:549-554 38. Reath DB, Kirby JK, Lynch M, Maul1 Kl: Injury and cost comparison of restrained and unrestrained motor vehicle crash victims. American Association for the Surgery of Trauma, 48th Annual Meeting, 1988, p 130
