Patient Presentation
A 3-month-old female came to clinic about 2 hours after being a restrained passenger in a low-speed car accident. The patient was inrear-facing car seat in the back seat of a 2-year-old, sedan-style car. The mother was driving in a parking lot and had been rear-ended by another car. The mother stated that the left rear light area had been damaged but the bumper was intact. The other car had right front light damage and was otherwise okay. Both drivers had no injuries, no airbags deployed in either car, and both cars were drivable. The infant had seemed slightly fussy after the incident and did not feed as well as usual so the mother wanted the child examined. The mother denied any other problems such as loss of consciousness. The past medical history showed a full-term infant who had received appropriate preventative care.

The pertinent physical exam revealed a smiling infant with normal growth parameters and vital signs. HEENT showed that the anterior fontanelle was patent and not bulging. Skin showed no bruising. Her neurological examination was normal. The diagnosis of a healthy 3 month old who had been in a low-speed car accident was made. The mother was counseled that the infant appeared well at this time and that this seemed to be a low-speed accident, therefore watchful monitoring was called for. “I’m not sure why the baby didn’t eat as well but she appears well now and I think you can just watch her as this sounds like a low-speed accident. Let’s look at the car seat you have here and see if it has any information about when to replace it after an accident too,” the pediatrician counseled. The car seat did not have any noticeable damage but did have a notice that it should be replaced if it was in a crash when examined by the pediatrician. “You should always follow the manufacturer’s recommendations and in this case, I would replace the car seat even though this seemed to be a low-speed collision,” she remarked. Later she was reviewing the encounter with the medical student who had accompanied her during the visit. The medical student asked at what speeds airbags deploy. “I’m not entirely sure but it is lower than you think. We should try to find the answer,” and they went to a computer to check the Internet for more information.

Discussion
Airbags are supplemental (not primary) safety devices in motor vehicles that are intended to prevent injuries mainly to the head, neck, and torso. They are designed to provide the greatest protection when the occupant is seated properly and wearing a seat belt properly. Front airbags are designed to inflate within 50 milliseconds of impact in a moderate to severe crash. They usually will deploy for belted occupants at speeds of 16 miles/hour (mph) or more, but with newer sensors and algorithms will deploy at lower speeds if they detect unbelted occupants (i.e. 10-12 mph). Forward airbags will also deploy for impacts in other vehicle locations if there is sufficient forward motion of the occupant detected. In the US front airbags have been required since the 1999 model year.

Side airbags are designed to inflate for side impacts or if parts of the vehicle begin to intrude in the passenger compartment. Head protection is considered of primary importance, but other airbags offer more pelvis or torso protection. As there is a smaller space between the vehicle’s side and the occupant, the airbags need to deploy quicker usually within 10-20 milliseconds of impact. Side airbags are not necessarily required in the US but are often used to meet the standards for head and torso protection required for all occupants.

Airbags may deploy from a variety of locations depending on the model. Steering wheel, passenger front panel, ceiling, doors, and seat backs are common locations for airbags which may be marked with “SRS” or “Airbag”. Airbags should be replaced with “OEM” or original equipment manufacturer replacement parts after they have been deployed. Recalled airbags should be replaced as soon as replacement parts are available by a qualified repair shop associated with a new-car dealership.

Other airbags include knee airbags, inflatable seat belt airbags, between seat airbags, and external hood airbags. In some countries airbags integrated into motorcycles are available. There is also a bicycle helmet that has an integrated airbag too.

National Highway Transportation Safety Administration (NHTSA) estimates that 44,869 lives have been saved by frontal airbags and 2252 saved because of side airbags up to 2015. Airbags can cause injury because they must inflate quickly. Therefore, drivers and front passengers should be as far back from the steering wheel and passenger instrument panel as they can: at least 10 inches from the occupant’s chest. Pregnant women, especially in their last trimester of pregnancy, if they cannot be positioned correctly are recommended to not drive. Shorter drivers may be able to slightly recline the seat or may need pedal extenders. A rear-facing car seat should never be put into a front passenger seat with an airbag as it positions the head to close to the airbag. All children should be placed in the rear seat. Children over 13 may sit in the front seat, properly belted in and positioned, but still the safest location is the middle or rear of the vehicle. Young children who must routinely be transported in the front seat can seek help from their car manufacturer or NHTSA regarding airbag options.

Learning Point
The National Highway Transportation Safety Administration (NHTSA) defined a minor motor vehicle crash and all criteria must apply as:

• “The vehicle was able to be driven away from the crash site.
• The vehicle door nearest the car seat was not damaged.
• None of the passengers in the vehicle sustained any injuries in the crash.
• If the vehicle has air bags, the air bags did not deploy during the crash; and
• There is no visible damage to the car seat.”

Always follow the manufacturer’s instructions. A car seat should never be used that has been involved in a moderate to severe crash.

A moderate to severe crash is defined as the “equivalent to hitting a solid, fixed barrier at 8-14 mph or higher. (This would be the equivalent of striking a parked car of similar size at about 16-28 mph or higher.)

Questions for Further Discussion
1. What are the recommendations for use of car seats for various ages and sizes of children?
2. What are the recommendation for bike helmet use and bicycling safety for children?
3. What summer and winter safety guidance should be offered to families? For summer safety click here; for winter safety click here.

Related Cases

Disease: Airbags | Motor Vehicle Safety

Symptom/Presentation: Behavior Problems

Specialty: General Pediatrics

Age: Infant

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.
Information prescriptions for patients can be found at MedlinePlus for this topic: Motor Vehicle Safety.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

NHTSA. Air Bags.
Available from the Internet at https://www.nhtsa.gov/equipment/air-bags (cited. 4/13/18).

Insurance Institute for Highway Safety. Highway Loss Data Institute. Airbags.
Available from the Internet at http://www.iihs.org/iihs/topics/t/airbags/qanda (cited 4/13/18).

NHTSA. Car Seat Use After a Crash.
Available from the Internet at https://www.nhtsa.gov/car-seats-and-booster-seats/car-seat-use-after-crash (cited 4/13/18).

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa