Emergency War Surgery NATO Handbook: Part I: Types of Wounds and Injuries: Chapter V: Blast Injuries
United States Department of Defense
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The blast wave exerts a force (pressure times exposed area) on the body surface. That force is transmitted to internal structures by bulk movement of tissue. Inertial effects may play a role in the injuries seen around the relatively massive airways and vessels suspended in the lighter tissue of the lungs. Mass differences, the compressibility of isolated gas pockets, and the material properties of the foam-like lung tissue are probably critical factors in blast injury. Pressure waves propagate in the lung parenchyma as a result of blast exposure. At some point, the lung is unable to pass on the local stresses generated at the pleural surface as fast as the chest wall moves and delivers energy. In such a case, the local compressions, shears, or tensile stresses exceed the physical limits of the lung substance and injury occurs.
For the gut and tympanic membrane, the physical events leading to injury are probably much simpler. Isolated collections of gas within the bowel lumen are compressed by the pressure wave within the abdomen. At some point, the bowel wall is stressed to the point of failure, manifested as either intramural hemorrhage or frank rupture. The eardrum is a relatively simple membrane which completely closes one end of a tube, the other end of which is open to the air. The middle ear airspace behind the drum is unable to equilibrate pressures rapidly enough through the Eustachian tube. When the stress on the drum exceeds the limits of the tissue, the tympanic membrane ruptures.
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