Airbag Deployment Can Cause 'Hidden' Cardiac Injuries

Marlene Busko

January 17, 2014

MEMPHIS, TN — Authors of a new review are warning cardiologists and other health professionals of "hidden injuries" that can arise from automobile airbags [1]. Even though airbags save lives and reduce injuries, they can also cause cardiac and pulmonary injuries and death, especially if the driver or passenger is not wearing a seatbelt and — of special note — people who present following low-speed crashes.

"Cardiac injuries can happen due to airbag deployment even with no visible injury at the time of presentation to the hospital, and this may include serious cardiac injuries," lead author Dr Rami Khouzam (University of Tennessee Health Science Center, Memphis) explained to heartwire in an email. The main types of cardiovascular injuries following airbag deployment are aortic transection, tricuspid-valve injury, right atrial rupture, cardiac contusion, MI, aortic-valve avulsion, cardiac tamponade, and hemopericardium, he noted.

Physicians and the general public need to be aware that sitting closer than 10 inches to where an airbag would deploy can cause greater injury, and airbags should be switched off (if possible) in certain cases when there is a young child or short person in the front passenger seat. Although the risks of air bags related to passenger size are well known and have been taken into account with refinement of the technology, Khouzam and colleagues point out that injuries are still seen, even with the latest airbag technology.

The review article was published online January 9, 2014 in the Canadian Journal of Cardiology.

"Despite the fact that airbags are considered to be lifesaving and their use has significantly reduced the fatality rate associated with high-speed collisions, airbag deployment alone has recently been implicated as a cause of clinically significant thoracic injury to unrestrained drivers," Khouzam and colleagues write. The first cases of cardiac trauma were reported in 1993.

To investigate airbag-related injuries and deaths, they searched the literature for "airbag" and "trauma" from 1970—when airbags were introduced—until January 2013. They identified 57 reviews, case reports, and prospective studies.

Identifying Cardiac and Pulmonary Complications

It can be difficult to detect cardiac trauma in a patient who is injured in a car accident. "Because it can occur in the absence of chest pain or visible wounds, cardiac trauma can easily be missed in the presence of other injuries," the authors write. "A high index of suspicion must be entertained in decelerating-type accidents to diagnose occult injury to the aorta and great vessels," they add.

The right ventricle is directly behind the sternum, so it receives the full impact of the airbag on the anterior chest wall, the authors explain. As well, the right atrium can be ruptured, because it is one of the thinnest vascular structures in the thorax.

"It is important to consider acute coronary occlusion in the differential diagnosis of chest pain following blunt trauma related to airbag deployment and even in young patients," they continue. MI and valvular injury may be masked by blunt cardiac trauma of collision, and evaluation by coronary angiogram and transthoracic echocardiogram may be warranted.

When an airbag deploys, it can also cause rib and sternum fractures. A patient may have new-onset or exacerbated asthma or have inhalational chemical pneumonitis from byproducts of a chemical reaction in which sodium azide powder releases nitrogen gas that inflates the airbag. If the airbag is ruptured, the release of alkaline chemicals can cause burns.

"The situations in which airbags are most dangerous are low-speed collisions, when the occupants are positioned closer to the airbag at the time of deployment, particularly shorter adults and those who ride unbelted," according to the researchers.

Airbags Can Still Be Improved

With first-generation frontal airbags, some small-stature adults, children, and infants who were not restrained or sat too close to where airbags were deployed were seriously injured or died following airbag deployment. Second-generation frontal airbags with less forceful inflation were introduced in 1998. Then in 2003, some cars were equipped with third-generation or "advanced" frontal airbags designed to be more effective than depowered airbags and yet still reduce potential airbag-induced serious injury or death.

All passenger cars and light trucks produced after September 1, 2006, are required to have advanced frontal air bags, and newer cars also have side airbags.

According to the National Highway Traffic Safety Administration, in 2011, 21 253 occupants of passenger vehicles died in motor vehicle traffic crashes, and of these, 56% were not wearing seat belts. An estimated 2204 lives were saved by frontal airbags in that year. On the other hand, since June 2003, 144 children and 87 adults have died because of airbags, and many others have been injured.

Vehicle manufacturers need to continue to improve the technology to reduce injuries and death, researchers conclude. "We are still some way from the ideal combination of maximum protection with minimum risk."

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