Cover article

Airbags and children:
A mixed blessing

By Ken Kontio, MD, Merv Letts, MD, and Alan German, PhD, C Phys

The dangers of airbags to children have been almost as well publicized as the benefits. Prospects for moderating the former and emphasizing the latter are improving.

Pediatricians who have been in practice for more than two decades remember when a newborn went home from the hospital in the arms of his or her mother, who sat without a seat belt in the front passenger seat of the family car. Months later, when the infant went out with his parents for a ride, he sat in an infant seat that was hooked over the back of the right-front passenger seat.

LEARNING OBJECTIVES

After reviewing this article the physician should be able to:

We have come a long way since then. Back-facing infant seats, placed in the rear compartment of the car, are ubiquitous. Almost all states mandate the use of safety belts, and new cars must be equipped with airbags that deploy in a crash. Yet we now know that the deployed airbag itself can inflict serious damage on a young child or an adult of small stature.

This raises several questions. What kind of injuries do airbags cause, and how common are they? How can the incidence and severity of these injuries be reduced? And what can pediatricians do to help?

Defining the problem

Airbags came into common use in the United States with the

release in 1987 of the Federal Motor Vehicle Standard 208, Occupant Crash Protection legislation. The statute "recommended" that airbags and three-point seatbelts be fitted in all passenger automobiles, trucks, and vans. A second federal mandate in 1991 "required" airbag installation in all new automobiles by the beginning of the 1998 model year and in all new light trucks by model year 1999.¹ As a result, more than 107 million driver-side airbags and 81 million passenger-side airbags are in use in vehicles on US roadways.²

Vehicles increasingly are being sold with airbags that deploy from the side as well as from the front. One type of side airbag is mounted in the seat or side door at the level of the occupant's chest and head. Another "curtain" type deploys to cover the window at head level. These airbags are intended to protect occupants from side-impact injuries, primarily to the chest, upper limbs, and head. There are no federal mandates regulating their introduction or use.

According to estimates, dual front airbags decrease right-front passenger fatalities in frontal collisions by 18% and in all crashes by 11%. Nonetheless, airbag deployment is now recognized as a substantial contributor to vehicular-related trauma in children¹ (Figure 1). Data suggest an amazing 34% increase in right-front passenger seat deaths when the airbag deploys if that passenger is a child younger than 10 years of age.³ According to the National Highway Traffic Safety Administration (NHTSA), 82 children from 1 to 11 years of age have been killed by passenger airbags since 1990.⁴ Of these children, 64 are believed to have been unbelted and eight were belted improperly. (See "The law and seat belt use".) During this same period, 18 infants were killed; 15 of these infants were restrained in rear-facing infant seats and three were on adult passengers' laps.² Yet, in many of these crashes, the vehicle was moving at low or moderate speed—in all likelihood too slow to have caused a fatality had the airbag not deployed. These statistics have prompted many observers to look closely at what causes injuries and deaths in vehicle crashes and at how to prevent them.⁵

The law and seat belt use

Forty nine states, the District of Columbia, Puerto Rico, and all United States territories have laws mandating use of seat belts. In most states, these laws cover only front-seat occupants, though laws in 14 jurisdictions apply to rear-seat occupants as well. In New Hampshire, seat belt use is required only up to the age of 12.

Enforcement of seat belt violations is either "primary," allowing police officers to issue citations for not buckling up, or "secondary," where an officer must have another reason for stopping a vehicle before issuing a citation for failure to use a seat belt. Thirty-seven states have "secondary" enforcement of seat belt violations and 12 have "primary" enforcement. Seat belt use in states with "primary" laws is about 15% higher on average than in states with "secondary" laws.

The National Highway Traffic Safety Administration estimated that in the fall of 2000, 71% of front-seat passengers used seat belts.

How airbags injure children

An impact speed of eight to 14 miles an hour triggers sensors to deploy an airbag. A propellant (sodium azide) ignites, which liberates nitrogen gas, carbon dioxide, and alkaline aerosols.⁵ In a frontal crash, the vehicle occupants continue to move forward as the vehicle's front end is crushed. At the instant the crash occurs, the airbags inflate, slowing passengers' forward motion and acting as energy-absorbing buffers between them and the windshield, steering wheel, and other hard interior surfaces. Safety belts also help to decelerate passengers' forward motion, decreasing the amount of injury-causing force the crash applies. Deceleration of an improperly or unrestrained child doesn't begin until the child strikes an object, increasing the force of the crash that is applied to the child.

The safety belt also keeps a child from being very close to the airbag as it begins to inflate—the moment at which the airbag can cause the greatest injury because tremendous energy is required for inflation.⁶ Hence, when the head and torso of a child who plunges forward because of preimpact braking is close to a deploying airbag, the child is pushed backward rapidly by the airbag, which is inflating at 150 to 200 miles an hour. This produces an extremely large and violent force against the child's head as the head is thrown backwards. The impact to the child's head and possible life-threatening injuries from the marked extension of the child's neck are major concerns (Figure 2). An infant carrier positioned in the right passenger seat similarly places the infant's head in very close proximity to the deploying airbag, exposing the infant to injury that can be fatal (Figure 3).

Little is known yet about how side airbags might injure children. The lateral direction of deployment suggests that side airbags would apply less direct force than front airbags.

A range of injuries

To assess a child who has been in a motor vehicle crash, pediatricians need to be aware of specific patterns and types of injuries caused by deployed airbags. These injuries range from abrasions to chemical burns to life-threatening head and spinal trauma.

Dermatologic injury. The skin can sustain a wide array of injuries, from small abrasions to full lacerations and even thermal and chemical burns (Figure 4).^7,8 Depending on the type of airbag involved, the nylon fabric can cause direct contact injury. The heat released during deployment may also cause direct thermal injury to the skin or indirect damage to the rider's clothing. Chemical byproducts of combustion can create a fine alkali aerosol containing sodium hydroxide, sodium carbonate, and other metallic oxides—a mixture that can be corrosive if it is converted into solution by sweat or tears.

The child should undress completely for assessment after contact with a deployed airbag. Examine the skin thoroughly, paying special attention to the face and eyes.

Otologic injury. Ear injuries caused by airbag deployment are not common, but serious injuries have been reported.^9,10 Many patients complain about hearing loss and tinnitus after airbag impact, and objective testing may reveal losses such as unilateral or bilateral sensorineural, unilateral conductive, and mixed deficits. Tympanic membrane perforation has also been reported. These perforations should heal and any associated symptoms resolve within about six weeks. Objective hearing loss may be permanent, however. How close the ear is to the airbag during deployment is thought to be directly associated with the severity of injury.

Although many patients studied in the literature are adults, such an array of potentially serious injuries should prompt examination of the ears and hearing of a child who has been in a motor vehicle crash in which airbags have deployed. Whether the increased use of side airbags will make this type of injury more prevalent remains to be seen.

Ocular injury. Because a deployed airbag is often at the level of a child's head, it is not surprising that youngsters incur eye injuries in car crashes. The result may be corneal abrasion, hyphema, vitreous or retinal hemorrhage, retinal tear or detachment, and even rupture of the globe.¹¹ Electronic games and toys and other objects that children often hold while they are riding in a car can become projectiles when an airbag deploys, causing serious injury to the eye.⁹ Chemical projectiles created by propellant particles can also result in alkali keratitis, a potentially vision-threatening condition.⁸

If you suspect an ocular injury, evaluate the child with gross visual acuity testing and slit lamp or fundoscopic examination. Check the inferior cul-de-sac with litmus paper for pH, and institute irrigation if it is alkaline. Signs of ocular trauma call for ophthalmologic consultation.

Neurologic injury accounts for most deaths attributable to airbags among children.^5,12 Crush injury to the skull predominates in infant victims traveling in a rear-facing child safety seat inappropriately placed in the front passenger seat. Other neurologic injuries include subdural hematoma, cerebral edema, and skull fracture.¹³ Brainstem injury has also been reported.¹⁴ Deaths are frequently due to occipital or C1 dislocation, resulting in cord injury. Careful examination and observation are warranted, with cranial bone or soft tissue imaging as required.

Visceral injury. Although airbags occasionally cause injury to the chest and abdomen, such as hemothorax, rib fracture, pericardial laceration, and visceral injury, these injuries seem to be less common in children than in adults—in part because it is the child's head, not torso, that comes in full contact with the airbag. The plasticity of a child's thoracic cage may also dampen the impact of the airbag. Damage to vital organs cannot be excluded, however, and the child should be managed with a comprehensive head-to-toe examination and a high index of suspicion to exclude these potentially dangerous injuries.⁹

Musculoskeletal injury mostly affects the upper limbs and spine. Finger, wrist, and forearm fractures have been reported.¹³ Of greater concern is the likelihood of injury to the cervical spine because of the often explosive nature of a deploying airbag. The craniovertebral junction is at particular risk of hyperextension injury.^5,12,14 Careful neurologic assessment and radiologic investigation, for occult or late-presenting instability, is appropriate for any child with a neck complaint. Ligamentous disruption, rather than bony injury, seems to predominate in this skeletally immature age group.

Children at special risk. Children with certain medical problems may be more likely than others to have particular injuries.¹⁵ In the child with chronic obstructive pulmonary disease, asthma, or other lung disease, for example, byproducts of the airbag propellant may precipitate severe bronchospasm. The youngster who has suffered back or neck injury or surgery in the past risks reinjury from a deploying airbag. The same is true of a child who has had facial injury or surgery or ophthalmologic surgery.

The noise of a deploying airbag can exacerbate symptoms in a child with hyperacusis or tinnitus. Because of positioning problems, the child with severe scoliosis, achondroplasia, or another syndrome associated with short limbs, or the child who requires a wheelchair, may also face heightened risk. A youngster with Down syndrome, atlantoaxial instability, or severe developmental delay may sometimes be unable to sit back from an airbag. Although all children should be seated in the back seat of a vehicle, if possible, it is especially important for children at special risk for airbag injuries.

Newly licensed teenage drivers who are short in stature or skeletally immature also are at special risk because their seats need to be positioned forward. This places their upper torso and head in close proximity to the airbag, increasing the chance of airbag-associated injury during deployment. Cars that have no seating in the rear, such as sports cars, also present problems. The safety of drivers and passengers in these situations can be increased through the use of telescoping steering columns or by moving or tilting the seat back, so as to increase the distance between the individual's chest and the airbag. Adjustable foot pedals, another way to place the driver further from the airbag, are now available as optional equipment on some vehicles. Research also has shown that driving a smaller vehicle designed to fit smaller drivers will help position these individuals further back from the airbag. When these options are not available, airbag deactivation (discussed below) is the only way to neutralize the risk posed by airbag deployment.

Where we go from here

Efforts to reduce injuries and fatalities from airbags have focused on public education, revised testing standards for airbags, and improved airbag design.

Public education. The decline of child fatalities over the last year may be the result of increased attention to public awareness campaigns or continued media coverage of child fatalities caused by airbags. This issue has prompted the NHTSA to release recommendations for preventing death and injury (see Table).⁴ Despite these attempts to educate parents and drivers about the hazards of airbags to children, a 1997 study found that more than 30% of children in fatal crashes were riding in the front seat.³ In addition, as many as 40% of children continue to travel unrestrained—an alarming estimate.

Keeping children safe in the car

The back seat is the safest place for a child of any age to ride.

Never put an infant (younger than 1 year) in the front seat of a car with a passenger-side airbag.

An infant must always ride in the back seat, facing the rear of the car.

Make sure everyone in the car is buckled up with a safety belt. Unbuckled occupants can be hurt or killed by an airbag.

Source: National Highway Traffic Safety Administration

Physicians increasingly have a front-line position in educating the public about vehicle safety. The pediatrician, in particular, is in an excellent position to help change the attitudes and habits of both children and parents. By discussing safety issues and having visible reminders in their office, such as posters, the pediatrician can raise awareness of potential dangers. More formal actions to reduce accident injuries, such as legislation to require seat-belt use and modified airbag design, are also needed.

Parents need to know how important it is to properly restrain and position their child. Child seats and booster cushions allow the child to sit higher in the seat so that lap and shoulder belts are properly positioned to offer adequate protection in all types of crashes (Figure 5). Regrettably, these systems are not as widely used as they might be, and are not always used appropriately or correctly. Investigators also estimate that 80% of child safety seats are used improperly, as described in "Using child safety and booster seats".¹⁶ In the absence of a booster seat, the shoulder strap often impinges on the child's neck. To avoid this irritation, the parent may put the shoulder portion of the restraint under the child's arm, decreasing the effectiveness of the restraint.

Using child safety and booster seats

According to the National Highway Traffic Safety Administration (NHTSA), restraint use for children from birth to 1 year of age is 97% and for children from 1 to 4 years of age 91%. In children 5 and older, these figures plummet alarmingly. From ages 5 to 15 years, only about 69% of children use restraints. According to 1988 data from the Fatality Analysis Reporting Service, more than 47% of fatally injured children from 4 to 7 years of age are completely unrestrained. One NHTSA study showed that only 6.1% of children who belong in a booster seat are actually restrained in this manner.

All 50 states and the District of Columbia have child restraint laws requiring children to travel in approved child restraint devices. Some states permit or require older children to use adult safety belts, with the age at which belts can be used differing among the states. Because of the way laws are worded in some states, many children are covered by neither a safety belt law nor a child restraint law.

The accompanying table lists recommendations for safety and booster seat use in children.

Seating children safely*

New testing standards. A congressional mandate to improve the protection offered by airbags and to minimize their potential for harm led to release of a regulation in the summer of 2000 that sets forth new standards of testing.² Until now, manufacturers conducting automobile crash testing have been required to use only dummies that simulate an adult male at the 50th percentile for height and weight. New testing with dummies that simulate children of various ages as well as a female dummy in the fifth percentile for height and weight also will be required.¹⁷ The small-statured female crash dummy in the proposed NHTSA testing will reasonably simulate a 12-year-old child. These dummies will be used primarily for static testing, in which airbags either are suppressed or are inflated with forces below specified thresholds (low-risk deployment).

These tests will result in development of airbags that either inflate with less energy than they normally do or do not inflate at all in certain situations where passengers are at risk of being injured by deploying airbags, thereby reducing injuries in those most likely to be hurt by deployment—infants, children, and short adults. Airbags that meet new testing standards will be required on 2004 model-year vehicles, with full implementation by August 2006.

Airbag deactivation. NHTSA has defined four situations in which installation of an on/off switch for airbag deactivation is advisable: The driver is unable to sit at least 10 inches away from the steering wheel; the driver is transporting more children from 1 to 12 years of age than can safely fit in the back seat of the vehicle; the driver must place a rear-facing infant seat in front; or an occupant of the car is at high risk of airbag injury for medical reasons. It is permissible to have factory-installed passenger airbag on/off switches in new vehicles with no back seat or a back seat that is too small to safely position a rear-facing child seat. All others who wish deactivation must seek approval for an on/off switch from the NHTSA, which considers requests on a case-by-case basis. Request forms are available at dealerships, repair shops, state motor vehicle offices, the NHTSA Internet site (www.nhtsa.dot.gov ), and Automobile Association of America offices.²

Other possibilities. Additional suggestions for protecting children from airbag injury include increasing deployment thresholds to avoid inflation in minor crashes, the use of lighter and less abrasive airbag materials, and venting airbag gases outside of the occupant compartment. The use of more vertically deploying airbags, which inflate toward the roof of the vehicle and are deflected toward the occupant after contact with the windshield, is controversial. The next generation of airbags is in development and may represent the most significant step in protecting children.^6,9 These "smart" airbags rely on sensors to know when someone is in the seat and his size, whether or not he is restrained, and his proximity to the airbag. This information can then be used to decide if the airbag will be used at all and, if so, at what threshold or force it will be deployed.

What pediatricians can do

For the practicing pediatrician, continued patient and parent education about the risks airbags pose, and what can be done to prevent the injuries they cause, remain our most effective intervention. Stress the importance of buckling up children properly, using car seats and booster seats for small children, and placing the child in the back seat of the car whenever possible. More concentrated and vocal support for legislative reform, primarily in seat belt use and airbag technology, is also an important avenue for advocating for the safety of patients. Community safety group materials and educational information are available on the Web at www.highwaysafety.org . A copy of "Physician counseling about safe vehicle travel for children" by Williams and colleagues is available by writing to: Publications, Insurance Institute for Highway Safety, 1005 North Glebe Road, Arlington, VA 22201.

REFERENCES

1. Mehlman C T, Scott KA, Koch BL et al: Orthopaedic injuries in children secondary to airbag deployment. J Bone Joint Surg Am 2000;82-A(6:)895

2. Insurance Institute for Highway Safety: Airbag statistics and status reports, 1998­2001. www.hwysafety.org

3. Braver ER, Ferguson SA, Greene MA, et al: Reductions in deaths in frontal crashes among right front passengers in vehicles equipped with passenger airbags. J Am Med Ass 1997;278:1437

4. Transport Canada: www.tc.gc.ca

5. McCaffrey M, German A, Lalonde F, et al: Airbags and children: A potentially lethal combination. J Ped Orthop 1999;19:60

6. Mckay MP, Jolly T: A retrospective view of airbag deaths. Acad Emerg Med 1999;6:708

7. Stein JD, Jaeger EA, Jeffers JB: Airbags and ocular injuries, Transactions of the American Opthalmological Society 1999;97:59

8. Vitello W, Kim M, Johnson R, et al: Full-thickness burn to the hand from an automobile airbag. J Burn Care Rehabil 1999;20 (3):212

9. Mikhail JN, Huelke DF: Airbags: An update. J Emerg Nurs 1997;23:439

10. Tibbs RE Jr, Haines DE, Parent AD: The child as a projectile. Anat Rec 1998;253:167

11. McFeely WJ Jr, Bojrab DI, Davis KG, et al: Otologic injuries caused by airbag deployment. Otolaryngol Head Neck Surg 1999;121(4):367

12. Giguère JF, St-Vil D, Turmel A, et al: Airbags and children: A spectrum of C-spine injuries. J Pediatr Surg 1998;33(6):811

13. Baruchin AM, Jakim I, Rosenberg L, et al: On burn injuries related to airbag deployment. Burns 1999;25(1):49

14. Morrison AL, Chute D, Rodentz S, et al: Airbag-associated injury to a child in the front passenger seat. Am J Forensic Med Pathol 1998;19(3):218

15. National Conference on Medical Indications for Air Bag Disconnection, July 16­18, 1997: Final report. www.nhtsa.dot.gov/airbags

16. Mohamed AA, Banerjee A: Patterns of injury associated with automobile airbag use. Postgrad Med J 1998;74:455

17. Dalmotas DJ: Assessments of airbag performance based on the 5th percentile female hybrid III crash test dummy; paper No. 98-S5-0-07. Proceedings of Enhanced Safety of Vehicles Conference, Windsor, Ontario, Canada, 1998, p 1019

DR. KONTIO is Clinical Fellow (orthopedics), Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, Canada.

DR. LETTS is Head, Division of Pediatric Orthopaedics, at the same institution.

DR. GERMAN is Chief, Collision Investigation (ASFBC), Road Safety & Motor Vehicle Regulation Directorate, Transport Canada.

ACCREDITATION

This activity has been planned and implemented in accordance with the Essentials and Standards of the Accreditation Council for Continuing Medical Education through the joint sponsorship of Jefferson Medical College and Medical Economics, Inc.

Jefferson Medical College of Thomas Jefferson University, as a member of the Consortium for Academic Continuing Medical Education, is accredited by the Accreditation Council for Continuing Medical Education to sponsor continuing medical education for physicians. All faculty/authors participating in continuing medical education activities sponsored by Jefferson Medical College are expected to disclose to the activity audience any real or apparent conflict(s) of interest related to the content of their article(s). Full disclosure of these relationships, if any, appears with the author affiliations above.

CONTINUING MEDICAL EDUCATION CREDIT

This CME activity is designed for practicing pediatricians and other health-care professionals as a review of the latest information in the field. Its goal is to increase participants' ability to prevent, diagnose, and treat important pediatric problems.

Jefferson Medical College designates this continuing medical educational activity for a maximum of one hour of Category 1 credit towards the Physician's Recognition Award (PRA) of the American Medical Association. Each physician should claim only those hours of credit that he/she actually spent in the educational activity.

This credit is available for the period of April 15, 2001, to April 15, 2002. Forms received after April 15, 2002, cannot be processed.

Although forms will be processed when received, certificates for CME credits will be issued every four months, in March, July, and November. Interim requests for certificates can be made by contacting the Jefferson Office of Continuing Medical Education at 215-955-6992.

HOW TO APPLY FOR CME CREDIT

1. Each CME article is prefaced by learning objectives for participants to use to determine if the article relates to their individual learning needs.

2. Read the article carefully, paying particular attention to the tables and other illustrative materials.

3. Complete the CME Registration and Evaluation Form below. Type or print your full name and address in the space provided, and provide an evaluation of the activity as requested. In order for the form to be processed, all information must be complete and legible.

4. Send the completed form, with $20 payment if required (see Payment, below), to:
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5. Be sure to mail the Registration and Evaluation Form on or before April 15, 2002. After that date, this article will no longer be designated for credit and forms cannot be processed.

FACULTY DISCLOSURES

Jefferson Medical College, in accordance with accreditation requirements, asks the authors of CME articles to disclose any affiliations or financial interests they may have in any organization that may have an interest in any part of their article. The following information was received from the author of "Airbags and children: A mixed blessing."

Ken Konito, MD, has nothing to disclose.

Merv Letts, MD, has nothing to disclose.

Alan German, PhD, C Phys, has nothing to disclose.

 

Merv Letts, Ken Kontio, Alan Gesman Peng. CME: Airbags and children: A mixed blessing. Contemporary Pediatrics 2001;4:96.