Combat helmet design and TBI
September 1, 2009
From the New England Journal of Medicine: (edited for brevity).
Among surviving soldiers wounded in combat in Iraq and Afghanistan, TBI appears to account for a larger proportion of casualties than it has in other recent U.S. wars. […]22 percent of the wounded soldiers from these conflicts […] had injuries to the head, face, or neck. This percentage can serve as a rough estimate of the fraction who have TBI [T]he true proportion is probably higher, since some cases of closed brain injury are not diagnosed promptly.
In the Vietnam War, by contrast, 12 to 14 percent of all combat casualties had a brain injury, and an additional 2 to 4 percent had a brain injury plus a lethal wound to the chest or abdomen. [B]ecause mortality from brain injuries among U.S. combatants in Vietnam was 75 percent or greater, soldiers with brain injuries made up only a small fraction of the casualties treated in hospitals.
Kevlar body armor and helmets are one reason for the high proportion of TBIs among soldiers wounded in the current conflicts. By effectively shielding the wearer from bullets and shrapnel, the protective gear has improved overall survival rates, and Kevlar helmets have reduced the frequency of penetrating head injuries. However, the helmets cannot completely protect the face, head, and neck, nor do they prevent the kind of closed brain injuries often produced by blasts. As insurgents continue to attack U.S. troops in Iraq, most brain injuries are being caused by IEDs, and closed brain injuries outnumber penetrating ones among patients seen at Walter Reed[…] All admitted patients who have been exposed to a blast are routinely evaluated for brain injury; 59 percent of them have been given a diagnosis of TBI[…]. Of these injuries, 56 percent are considered moderate or severe, and 44 percent are mild.
So the design and engineering of armor has changed the nature of the injuries that happen on the battlefield.
Design. Engineering. Acquired disabilities. That sounds like this blog.
Some physicists have looked at the current armor anew and determined that there are some serious problems.
Here is a preprint of a journal paper on the mechanics of traumatic brain injury caused by explosives.
Since we know that TBI is a major threat, these authors recommend adjusting the design of helmets so that they can better withstand the pressure waves that occur in explosions (without, of course, compromising their ability to also deflect bullets and shrapnel, which they currently do quite well).
The Army knows that this is an important issue and have made adjustments for it. (A quick shoutout to my former employer, who runs a facility that specializes in this area.) But how quickly can we engineer and manufacture a better helmet and deploy it to the troops who need it in Iraq and Afghanistan? Probably not quickly enough, and the military procurement process is famously biased by politics and restrained by bureaucracy— so in a classic case of “fighting the last war” our troops in ten years will probably be much better prepared than our troops on the ground today.