Blast injury
| Blast injury | |
|---|---|
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| Floor-by-floor breakdown of the injuries/deaths in the Alfred P. Murrah Federal Building from the April 1995 Oklahoma City bombing | |
| Classification and external resources | |
| eMedicine | emerg/63 |
| MeSH | D001753 |
A blast injury is a complex type of physical trauma resulting from direct or indirect exposure to an explosion. Blast injuries occur with the detonation of high-order explosives as well as the deflagration of low order explosives. These injuries are compounded when the explosion occurs in a confined space.
Blast injuries are divided into four classes: primary, secondary, tertiary, and quaternary.
Primary injuries are caused by blast overpressure waves, or shock waves. These are especially likely when a person is close to an exploding munition, such as a land mine. The ears are most often affected by the overpressure, followed by the lungs and the hollow organs of the gastrointestinal tract. Gastrointestinal injuries may present after a delay of hours or even days. Injury from blast overpressure is a pressure and time dependent function. By increasing the pressure or its duration, the severity of injury will also increase.
In general, primary blast injuries are characterized by the absence of external injuries; thus internal injuries are frequently unrecognized and their severity underestimated. According to the latest experimental results, the extent and types of primary blast-induced injuries depend not only on the peak of the overpressure, but also other parameters such as number of overpressure peaks, time-lag between overpressure peaks, characteristics of the shear fronts between overpressure peaks, frequency resonance, and electromagnetic pulse, among others. There is general agreement that spalling, implosion, inertia, and pressure differentials are the main mechanisms involved in the pathogenesis of primary blast injuries. Thus, the majority of prior research focused on the mechanisms of blast injuries within gas-containing organs and organ systems such as the lungs, while primary blast-induced traumatic brain injury has remained underestimated. Blast lung refers to severe pulmonary contusion, bleeding or swelling with damage to alveoli and blood vessels, or a combination of these. It is the most common cause of death among people who initially survive an explosion.
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