![]() ![]() ![]() Thus it has traditionally been believed that in the absence of pulmonary symptomatology if the TM is intact, it is highly unlikely that the patient has pulmonary injury. It is generally accepted that human tympanic membranes begin to rupture at pressures as low as 5 psi (35 kPa) and that majority at 15 psi (104 kPa). Tympanic membrane Injuries: The TM is considered more vulnerable than the lung tissue for effects of the blast wave. Shrapnel injuries crush injuries and burns are treated as per standard surgical protocols. Penta-erythritol-tetra-nitrate (PETN) has been implicated as one such toxin.Īll patients evacuated from an area close to the explosion should be examined for effects of PBI lung, ear and abdomen even in the absence of other external injuries. Present hypothesis is that this state is due to the toxic substances in the blast explosive being inhaled or absorbed through skin. This hyper-inflammatory state cannot be explained by injuries that are seen after other blast injuries. (e) Quinary Blast Injuries are a more recent addition and occurs commonly after attack with incendiary devices and is characterized by a constant hyper-inflammatory state syndrome. These injuries may add to the delayed fatalities. (d) Quaternary Injuries refer to the burns, injuries caused due to toxic fumes, crush injuries, exacerbation of chronic diseases like asthma and psychiatric disorders. Paediatric injuries are more severe due to their smaller body weight and structure. (c) Tertiary Blast Injuries: These are injuries caused due to the blast wind movement moving bodies and debris. ![]() These are common to any type of explosions and account for the largest class of injuries. (b) Secondary Blast Injuries: Injuries caused by flying shrapnel and present as penetrating organ injury. Intestinal PBI is more commonly seen in underwater injuries and generally involves the fixed parts of the colon with perforation. PBI of the gastrointestinal tract is almost always seen with lung and ear injuries. Air embolism involves cerebral or spinal vessels and produces neurological features indistinguishable from direct injuries.Ĭardiovascular changes of PBI include a fall in stroke volume, bradycardia and hypotension. Pulmonary PBI is the cause of mortality in most and includes lung contusion, alveolar rupture, air embolism and ARDS like picture. Tympanic PBI are the commonest and include tympanic membrane rupture and ossicle fracture or dislocation though infrequently hemotympanum without perforation is also seen. These are more manifest with high energy explosives. Almost always affects air-filled structures and structures with air-fluid interface like lung, gastrointestinal tract, tympanic membrane, blood vessels. (a) Primary Blast Injuries (PBI): Injuries caused by the over-pressure blast wave. The immediate negative phase of the high pressure blast wave (blast wind) too can cause primary blast injuries by the stress and shear waves produced. Added to this is the fact that effects of the blast wave are not prevented by body armour worn by the soldier. The blast wave travels at the speed of sound and is more damaging in a medium with reduced acoustic impedance such as underwater blasts and also in closed environs. The duration of the blast wave is directly proportional to the tissue damage. When the blast front reaches the human body it creates an enormous positive pressure shift which is responsible for the tissue damage. The advancing edge of the blast wave is called the “blast front”. The nature of primary blast injuries depends upon the tissue characteristics that are exposed to the blast phenomenon. air-fluid) interfaces due to the interaction of a high-frequency stress wave and a lower-frequency shear wave. Organs are damaged by dynamic pressure changes at tissue-density (e.g. The resulting extreme pressure differences result in stress and shear forces acting on the susceptible tissues of the human body and are referred to as primary blast injuries. As this wave expands in all directions and the pressure drops, it leads to the creation of the blast “under-pressure wave” with negative pressure and blast winds moving into this area. Blast strength is described as ratio of the overpressure generated to the ambient pressure. The gases expand rapidly, compressing the surrounding air, creating a supersonic “blast over-pressure wave”. High-energy explosive detonation results in extremely rapid (0.001 sec) conversion of a solid or liquid explosive into gases and sudden changes in atmospheric pressure. The nature of injuries caused by an explosion is best understood by analyzing the biomechanics of the blast. ![]()
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