TY - JOUR
AU - PhD, Stefan M. Duma,
AB - Abstract The purpose of this study was to investigate burn injuries resulting from frontal automobile crashes and to determine the effects of frontal airbags on the incidence of burn injuries. The study included 25,464 individual cases from the National Automotive Sampling System database files for the years 1993 to 2000. Occupants were at a significantly higher risk to sustain a burn injury when exposed to an airbag deployment (1.54%) compared with those who received a burn injury when not exposed to an airbag deployment (0.02%; P = 0.02). In contrast to previous publications, this study found that 1.53% of front seat occupants exposed to an airbag deployment sustained an airbag-induced burn injury. The vast majority of airbag-induced burn injuries were minor (98.7%); however, in cases with no airbag deployment, the burns were often much more serious, including fatal burns (29.6%). Occupant weight, height, sex, seatbelt use, and seat position were all found not to be significant in predicting the risk of airbag induced burn injury, whereas age and crash velocity were found to be significant. Although airbags have reduced the incidence of fatal and severe injuries in automobile collisions, they have increased the risk of less severe injuries.1 These associated injuries include upper extremity fractures,2,–5 eye injuries,6,–9 skin abrasions,10,–12 and skin burns. In particular, skin burns have been attributed to the high-temperature gases released during airbag deployment.13,–15 These types of thermal burns have been identified through case reports and observed primarily on the upper extremities16,–20 but have also been shown to occur on the face21,22 and thigh.12,23 In addition to the thermal burns, a few cases have indicated chemical burns resulting from airbag deployment.10,24,–27 There are several potential factors that could be the direct cause of the burn. Airbags are inflated by hot gas flowing through a metal inflator housing at the rear of the bag. Immediately after the airbag reaches full deployment, the hot gas exhausts through vent ports that are typically located in the back of the airbag. An occupant could experience a burn through contact with the metal inflator housing, which stays hot up to several minutes after deployment, or from the hot gas exiting the vent ports during and after deployment. To estimate the incidence of skin burns from airbag deployments, Reinfurt et al28 investigated 215 crash survivors exposed to driver-side airbag deployments. This study found through occupant self-reporting that 28% of the occupants sustained an airbag-induced skin abrasion, and approximately 7% of the occupants sustained an airbag-induced burn. Hallock17 references Swanson-Biearman et al29 and states that “the Chrysler Corporation has corroborated this finding by admitting that burns occurred in 5% of all airbag deployments involving their vehicles.” However, there is no specific publication to corroborate this alleged statement by Chrysler. Other data suggest that these rates are far too high. This potentially inflated rate is possibly the result of the incorrect identification of abrasions as burns. Antosia et al30 performed a retrospective review of 618 airbag-induced injuries and identified 7.8% of these as burn injuries. Given that the majority of airbag deployments result in no injury, this would imply that the incidence of burn injuries is far lower than the 7% reported by Reinfurt et al.28 Moreover, by considering the number of injuries rather than the number of occupants with injuries, the exposure risk may be exaggerated because of a multiple injury count on a single occupant. Although studies have demonstrated experimental and numerical modeling of heat transfer into the skin during an airbag deployment,31,–34 no study has successfully demonstrated the national incidence of airbag-induced skin burns. The purpose of this study was to elucidate the incidence of burn injuries in automobile crashes and to examine the effects of airbag deployment on these injury patterns. METHODS To eliminate the inaccuracies associated with small case study projections and the confusion between skin abrasions and burns, this study used the National Automotive Sampling System (NASS).35 The two primary advantages of using the NASS are that the database includes an analysis of approximately 5000 cases per year and that the injuries are coded by trained nurses using the Abbreviated Injury Scale (AIS).36 The AIS scale classifies injuries by body region on a six-point scale ranging from low severity (AIS 1) to fatal (AIS 6). The AIS values are assigned for each injury sustained and do not include combined effects from multiple injuries to the same patient. This coding allows for a consistent and accurate distinction and identification of burn injuries. Each crash scene is investigated by a group of trained accident investigators that examine and document vehicle damage, occupant injuries, and crash dynamics. The NASS cases are collected from 24 separate field research teams across the United States. Because it is not practical to investigate every crash in the United States every year, each case investigated for the NASS database is assigned a weighted value, which scales the incidence of the particular crash investigated to a number that represents actual occurrence of similar noninvestigated crashes that occur in the United States each year. The weighting factor is included in the NASS database for each case. This procedure has been used for national injury projection studies to analyze injury severity and crash characteristics for topics, such as lower-extremity injury patterns, upper-extremity injury patterns, and restraint effectiveness in motor vehicle crashes.1,6,37,–43 The occupant and injury numbers reported represent the weighted numbers based on the raw cases. Chi-square test of independence statistical analyses were performed using the SUDAAN statistical software for weighted survey data (SUDAAN, Research Triangle Park, NC). For this study, cases in NASS were selected from the years 1993 through 2000 that included drivers and front-seat occupants only and excluded ejected occupants and rollovers. In addition, only frontal impacts were considered, which are defined as having a primary direction of force (PDOF) in the 11-, 12-, or 1-o'clock position. Occupants with injuries and total injuries to occupants were analyzed. Burn injuries in the NASS database were identified using the current AIS injury codes for burns (Table 1).36 For burn injuries the AIS code identifies the burned body region, the degree of burn from first to third, and the percent of body surface that sustained a burn. In general, AIS 1 and 2 burn injuries are considered minor, and AIS 5 and 6 burn injuries are considered major. This study was divided into four parts. Table 1. Abbreviated Injury Scale (AIS) burn injury codes with descriptions for adults View Large Table 1. Abbreviated Injury Scale (AIS) burn injury codes with descriptions for adults View Large Part 1: Crashes With and Without Airbag Deployment For all occupants who were exposed to an airbag deployment, the number of occupants that sustained a burn injury was compared with the total number of occupants who did not sustain a burn injury. Next, an analogous search was performed for crashes in which the airbag did not deploy. Part 2: Airbag-Induced Burn Injury Locations Further investigation of injuries was made for crashes in which the occupant was exposed to an airbag deployment. Resulting burn injury locations were compared as percents of total injuries in similar crashes, depending on the source of injury. Airbag and other injury sources were compared for analysis of resulting burn injury location. Part 3: Burn Injury Severity and Injury Source Occupants and burn injuries were further investigated to identify trends relating burn injury source to the severity of the resulting burn injury. The occupants exposed to an airbag deployment were sorted apart from the occupants who were not exposed to an airbag deployment. The burn injury AIS values were identified and compared with the injury source for both categories. Next, the percentage of occupants who received a burn injury was calculated. Part 4: Occupant and Crash Characteristics Occupants with burn injuries were divided into two groups: group 1 included all occupants who received an airbag induced burn injury, whereas group 2 included all of the occupants with burns from other sources. The groups were divided in this way to identify occupant or crash characteristics that indicated risk of injury by specific injury source. RESULTS AND DISCUSSION Part 1: Crashes With and Without Airbag Deployment Of the 2,421,893 occupants who were exposed to an airbag deployment, 1.54% sustained a burn injury (Figure 1). In contrast, for the 10,007,687 occupants not exposed to an airbag deployment, only 0.02% sustained a burn injury in the crash. This increase in burn risk is statistically significant (P = .02). Figure 1. View largeDownload slide Burn injury incidence for occupants who were or were not exposed to airbag deployment (1993–2000). Figure 1. View largeDownload slide Burn injury incidence for occupants who were or were not exposed to airbag deployment (1993–2000). Of the occupants exposed to an airbag deployment, 37,162 sustained a burn specifically from the airbag (1.53%). Of these occupants with airbag-induced burn injury, 34,737 were drivers (93.5%), and 2,425 were passengers (6.5%). For all the burn injuries, 94.8% occurred to occupants exposed to an airbag deployment (Figure 2). If the occupants with a burn injury were exposed to an airbag deployment, the airbag was the source of the burn injury for 99.9% of the injuries. The top three sources for burn injury not including the airbag were a fire in the vehicle, the instrument panel, or another noncontact source. Figure 2. View largeDownload slide Number of burn injuries that occurred to occupants in frontal crashes. Figure 2. View largeDownload slide Number of burn injuries that occurred to occupants in frontal crashes. Part 2: Airbag-Induced Burn Injury Locations Occupants who sustained airbag-induced burn injuries sustained the majority of the injuries to the upper extremity (82.5%; Table 2). The next two most frequently injured regions were the face (7.7%) and the chest (2.9%). For crashes without airbag deployment, occupants sustained only 13.8% of the reported burn injuries to the upper extremity. Table 2. Locations of burn injuries in crashes with and without airbag deployment View Large Table 2. Locations of burn injuries in crashes with and without airbag deployment View Large Part 3: Burn Injury Severity and Injury Source Of the airbag-induced burns, 98.7% were AIS 1 injuries, 1.3% were AIS 2 burns, and only 0.04% were AIS 3 injuries (Figure 3). There were no airbag-induced burns resulting in AIS 4 or higher and all burn related fatalities were in the no airbag deployment group. There were 2,164 burn injuries to occupants not exposed to an airbag deployment. All of these injuries were from sources other than the airbag and were compared by AIS injury level to the severity of the injuries in crashes with airbag deployment, that had the airbag as injury source. Occupant burns in crashes with no airbag deployment, were distributed as 34.1% AIS 1, 10.3% AIS 2, 7.8% AIS 3, 18.2% AIS 5, and 29.6% AIS 6. In other words, if the airbag was the injury source, the injuries were mostly minor AIS 1 severity; however, in cases with no airbag deployment, there were considerably fewer AIS 1 burns, and the injuries were likely to be much more serious, with nearly 30% being fatal burns rated AIS 6. Figure 3. View largeDownload slide Abbreviated Injury Scale (AIS) injury severity comparison between airbag-induced burns and burns from other sources in crashes with no airbag deployment. There are no AIS 4 level injuries for either source. *Statistically significantly greater, P = .01. Figure 3. View largeDownload slide Abbreviated Injury Scale (AIS) injury severity comparison between airbag-induced burns and burns from other sources in crashes with no airbag deployment. There are no AIS 4 level injuries for either source. *Statistically significantly greater, P = .01. Part 4: Occupant and Crash Characteristics The next analysis was made by examining occupant and crash characteristics for the 38,919 occupants who sustained a burn injury from any source (Table 3). Table 3. Comparison of group 1 and group 2 crash characteristics indicating correlation between incidence of injury and crash variable View Large Table 3. Comparison of group 1 and group 2 crash characteristics indicating correlation between incidence of injury and crash variable View Large Occupant Sex. It was found that 66.1% of occupants with airbag-induced burn injury were male (24,565 occupants), compared with 69.0% of occupants who sustained a burn injury from a source other than the airbag (1,213 occupants). Occupant sex was not a statistically significant factor in incidence of burn injury by source (P = .87). Seatbelt Use. The analysis found that 84.5% of occupants with an airbag-induced burn injury were wearing a seatbelt (31,402 occupants), whereas only 36.5% of occupants who sustained a burn injury from a source other than the airbag (642 occupants). Although this study indicated that a much greater proportion of occupants were belted who received an airbag-induced burn injury, the difference was not statistically significant (P = 0.16). Seat Position The analysis found that 93.5% of occupants with an airbag-induced burn injury were drivers (34,747 occupants) compared with 90.1% of occupants that sustained a burn injury from a source other than the airbag (1,584 occupants). This difference was not statistically significant (P = .39). Within a 95% confidence interval, occupant age, and crash ΔV are significant variables correlating with the risk of incidence of airbag-induced burn injury. In particular, the occupants that sustained an airbag-induced burn injury were older and in crashes with a lower ΔV. In addition, younger occupants in crashes with a higher ΔV are more likely to sustain burn injuries from sources other than the airbag. For burned occupants from the airbag, the average age was 32.3 ± 14 years with a range of 15 to 67 years. CONCLUSIONS This article presents the most comprehensive investigation of automobile burn injuries to date as it investigates 12,429,580 front-seat occupants from 25,464 cases for the years 1993 through 2000. This study shows that occupants exposed to an airbag deployment are statistically more likely to incur a burn injury (1.54%) than those occupants who were not exposed to an airbag deployment (0.02%; P = .02). In particular, 1.53% of front-seat occupants exposed to an airbag deployment in a frontal collision sustained a burn injury specifically from the airbag. This rate is markedly less than the 5% or 7% estimated in previous studies. Given the large national database used to determine the risk of airbag- induced burn injury found in this study, the larger rates that were previously published seem inaccurate and inflated for two reasons. First, they were based on small groups of individual case studies with no accurate national statistical weighting procedure. Second, it is likely that these studies include abrasion injuries that were mis-classified as burn injuries. It was also shown that if the airbag was the injury source, the injuries were mostly minor AIS 1 type; however, in cases with no airbag deployment, the burn injuries were often much more serious, with nearly 30% being fatal burns rated AIS 6. 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TI - Analysis of Burn Injuries in Frontal Automobile Crashes
JF - Journal of Burn Care & Research
DO - 10.1097/01.BCR.0000132173.40745.D3
DA - 2004-07-01
UR - https://www.deepdyve.com/lp/oxford-university-press/analysis-of-burn-injuries-in-frontal-automobile-crashes-nGm4pus7CC
SP - 357
EP - 362
VL - 25
IS - 4
DP - DeepDyve
ER -