Serious injuries from airbags

cles caused a major reduction in mortality and morbidity from collisions. The more recent introduction of airbags has caused a smaller, but also significant, further reduction in mortality and morbidity. Airbags are, however, not without some definite injury patterns due to the bags themselves. It is important that medical practitioners managing trauma patients are aware of the possible injuries caused by airbags, their patterns, incidence and how these may be minimized by attention to preventative measures. In this issue of the Journal there are two case reports of serious injuries suffered due to airbag deployment in collisions. Cullinan and Merriman report a case of frontal impact resulting in airbag deployment, with rupture of the distal oesophagus in a postprandial situation, in a middle-aged man who had an underlying oesophageal motility abnormality (the ‘corkscrew oesophagus’).1 This complication would appear to be related as much to the particular individual’s underlying oesophageal abnormality as to the airbag specifically. Similar perforations have been reported after forceful vomiting episodes, unrelated to the forceful impact of a motor vehicle accident and airbag deployment. Thomson and Davis report a case of carotid dissection following air bag deployment.2 In a case report recently published in this journal, Nabarro and Myers reported the commonly recognized minor injuries of upper limb fractures.3 More than 96% of all reported occupant injuries related to airbag deployment are considered minor and include abrasions, contusions or lacerations to the face (42%), wrist (14.8%), forearm (16.3%) and chest (9.6%). The American Highway Transportation Safety Administration (AHTSA) collected this information over a period of 14 years,4 and were able to demonstrate, together with insurance industry data, that moderate to severe injury in crashes involving airbags is up to 29% lower than that in similar cars equipped only with automatic safety belts. The principal reduction has been in head and torso injuries because airbags help prevent whiplash-type motions. Airbags are designed to work as an adjunct to a wellpositioned lap-sash seat belt with appropriate pretensioning devices. The airbag is, by its nature, a round inflatable, rubber-lined, woven nylon bag, slightly bigger than the steering wheel when fully inflated. It is inflated by the ignition of gases (mainly nitrogen) with a small amount of alkaline aerosol. The airbag is propelled from its compartment at a speed of more than 160 kph. Within 2 s of deployment it deflates by the release of hot gases from rear exhaust ports into the passenger compartment. Burns from airbag injuries can be thermal (from the hightemperature gases), chemical (related to the alkaline corrosives), or frictional (due to direct contact of the bag on the skin, particularly that of the face). Most of these burns are light and superficial. Burns to the face and sclera are well reported and are considered to be due to the residue of gases, such as sodium hydroxide, from the airbag deployment. Minor upper limb injuries may be related to trapping of the upper limb between the airbag and the torso, or in the spokes of the steering wheel during deployment of the airbag. Eye injuries can be significant, principally from the alkaline keratitis caused by residue. Small adults and children may be at significant risk of cervical spine injury from airbag deployment. The study by Kaplain et al. of computerized crash simulation revealed a prediction of no benefit from airbags, in their current design, to restrained children.5 There have been well over 30 reports of children, either inproperly restrained or in rear-facing safety seats in front seat positions in motor vehicle collisions, who have died after airbag deployment.6 A unique report is of a small 17-year-old girl, 150 cm tall, who sustained a fatal basilar skull fracture following her vehicle’s airbag deployment in a low-speed accident.7 This person had not been wearing a seat belt. Small adults and children appear to have hyper-extension injuries during airbag deployment and this risk is significantly higher if the person is unrestrained by a seat belt. Extreme forward positioning of the driver or front-seat passenger in relation to airbag deployment appears to be a risk factor for severe cervical spine injury, according to a case report of a fatality due to cervical spine injury and diffused axonal injury of the brain.8 There is good evidence that the high risk for cervical spine injuries, given the risk factors outlined, is operative in lowspeed impact with airbag deployment. There are data to suggest that children under the age of 10 years, seated in the front seat of motor vehicles, have a 21% increased risk of fatality when an airbag is deployed.9 The mechanism of severe head and cervical spine injury to children and short-statured adults would appear to be in the close proximity of the head to the site of deployment of the airbag, either with children in rear-facing child restraint systems in the front passenger seats, or with front-facing situations but with the seat brought forward. Recommendations are that children should ride in the back seat of vehicles at all times, properly restrained by seat belts, and away from airbags. All airbags have been designed based around medium-sized adults. They have not been designed to accommodate the needs of small children located in the front seat of vehicles in minor collisions. The potential for side impact airbags to depose further risks to children in front seats has yet to be estimated. Apart from the stature of the occupant and the absence of seatbelt wearing as defined risk factors for injury in airbag deployment, there are specific mechanisms of injury related to the airbag themselves and other related objects. These include the cover of the airbag module itself, which can be released at high speed and, if faulty, can be a source of injury; foam particles from the airbag deployment; the alkali and chemical gases (if the airbag bursts); direct abrasions from the airbag; the trapping of upper limbs in odd positions; and the effect of other objects such as spectacles, pipes, rings etc. which the person may be using or wearing. Other unusual and rare injuries described include bilateral pneumothorax, presumably due to rupture of the airbag, allowing high-pressure gases to lead to explosive barotrauma through the patient’s airways. 10 ANZ J. Surg. (2001) 71, 507–508