Blast injuries are broadly categorized as primary, secondary, tertiary, quaternary, and quinary, based on a taxonomy of explosive injuries published by the Department of Defense in 2006. The trauma practitioner should be familiar with each of these patterns of injury and be able to predict associated injuries from each category.

Primary blast injuries occur when the blast overpressure transmits forces directly onto a person, causing tissue damage. The air-filled organs are the most likely affected by a primary blast injury and include the tympanic membrane, lungs, and gastrointestinal tract. Primary blast injuries are less common in open-space explosions but are increased in situations where the explosion occurs within a confined space, which allows the blast wave to reflect off of fixed structures. Rupture of the tympanic membrane is the most common manifestation of primary blast injury, occurring in up to one half of patients injured in an explosion.  Some have considered an intact tympanic membrane to be a strong negative predictor of severe blast injury, although this has proven not to be the case. The orientation of the patient to the blast wave (perpendicular vs. parallel), the presence or absence of cerumen in the ear canal, and whether the patient was wearing hearing protection at the time of the blast will all work to alter the true impact of the blast on the tympanic membrane.  Therefore, an intact tympanic membrane does not rule out blast injury.

The most common fatal injury among blast victims is to the lung, often referred to as “blast lung injury.” The blast wave causes tissue disruption at the capillary–alveolar interface, resulting in pulmonary edema, pneumothorax, parenchymal hemorrhage, and, occasionally, air embolus from alveolovenous fistulas.

Secondary blast injuries are created by debris from the explosive device itself or from surrounding environmental particles. Many devices contain additional munitions consisting of nails, pellets, ball bearings, and scrap metal designed to increase the lethality of the explosion. Fragments from the surrounding environment, including glass and small rocks, can become secondary missiles, as well. Secondary blast injuries are more common than primary blast injuries as the debris and added fragments travel over a much greater distance than does the shock wave from the primary blast.  Lacerations, penetrating injury, and significant soft tissue defects are the most common injuries seen from secondary blast injuries.

Tertiary blast injuries are caused by the body being physically thrown a distance or from a solid object falling onto a person as a result of the explosion. Most tertiary injuries are from a blunt mechanism, and crush injuries or traumatic amputations are not uncommon. Quarternary and quinary blast injuries have only recently been defined. They are miscellaneous blast injuries caused directly by the explosion but often due to other mechanisms, such as burns, inhalation injuries, and radiation effects.

Children injured by explosions suffer a different injury pattern as compared to adults. Children are more likely to sustain life-threatening injuries and traumatic brain injury. They are less likely to have an extremity injury or significant open wounds. The adolescent injury pattern resembles that of the adult, although they are more likely to have fewer internal injuries, more contusions, and have a higher risk of requiring surgical intervention for mild or moderate wounds when compared to adults.