Military personnel in combat zones are at increased risk for TBI resulting from blast injuries. Dr. Freeman, what can you tell us about blast injuries?
Well, Dr. Hemstad, blast injuries are caused by the indirect impact from a pressure wave generated by an explosion. The explosion causes an instant rise in pressure, which creates a blast wave. This wave starts at the site of the explosion and travels outward. The effects of the blast on a person depend on several factors, including:
- The type and strength of the blast
- The person’s distance from the blast, and
- Whether exposure is in an open environment or in an enclosed structure
Injuries caused by these pressure or blast waves are described as primary, secondary, tertiary, and quaternary. Primary blast injury occurs when the blast wave hits the body. Air-filled organs, such as the ears, lungs, stomach, and intestines are particularly at risk for blast injuries. This is also true for organs that are surrounded by fluid, such as the brain and the spine. As the wave passes through these organs, it can cause fragmenting and shearing of tissues.
Secondary blast injury includes being hit by flying debris, which can cause both penetrating and direct impact trauma.
Tertiary blast injury occurs when a person is physically thrown by the blast, which usually causes direct impact trauma. For example, being thrown by the blast might cause the head to strike the ground or a wall.
And lastly, quaternary blast injuries include burns, chemical exposure, and breathing toxic gases or vapors.