In blast injuries, primary blast injury is caused by which mechanism?

• A. The blast itself
• B. Shrapnel
• C. Body being thrown against a solid object
• D. Heat of explosion

Answer: (A)

The blast overpressure wave from the explosion is the mechanism behind primary blast injury. This rapid, high-pressure wave travels through air and tissues, causing damage mainly to gas-filled organs because of impedance differences and the extreme, sudden compression and expansion that follows. Effects often include tympanic membrane rupture, pulmonary barotrauma, and possible hollow-organ injury. Shrapnel injuries come from fragments (secondary), being thrown against a solid object causes tertiary injuries, and burns from heat or other explosion effects are quaternary injuries. So the damage caused directly by the blast wave itself is the primary mechanism.