Blasts as Major Threat to Humanity - Essay Example

Blast Injuries Introduction Conventionally, explosion is the fast chemical conversion of a liquid or solid into gas. Explosives, which are usually thermobaric – commonly referred to as fuel-air explosives, are either finely divided particles mixed with gases/air, or droplets suspended in air. Explosives fall into two categories namely low-order explosives and high-order explosives, with each category causing somewhat diverse patterns of injury. High explosives are extremely high reaction rate-chemical materials and their reaction is known as detonation. Such explosives include dynamite, picric acid, nitroglycerin, and ammonium nitrate fuel oil mixture among others. Upon detonation, a high explosive undergoes an almost instantaneous conversion into a gas at extremely high temperature and pressure. Rapidly, these high pressure gases expand generating a marked pressure wave known as the blast wave, which moves outward in every direction resulting into an abrupt shattering blow on everything in the immediate surroundings (Bailey and Murray, 1989). The blast wave inflicts on individuals in the surroundings injuries that are known as blast injuries, which this paper discusses. The blast wave is an intense rise in pressure that the detonation of a high explosive creates. In the ambient environment, the pressure rises almost instantly followed by an exponential decay and may have a brief reduced-barometric pressure period. The peak pressure as well as the period that the initial positive blast phase covers is dependent on the distance from the detonation centre (blast epicentre) and the explosion size. Energy transfer from the blast wave to bodies or objects in its path takes place causing damage (Elsayed, 2007). Below is a diagram showing a typical pressure/ blast wave. Source: Pennardt and Lavonas, 2010. Blast Injuries. One may characterize explosive devices on the basis of their source. The bureau of Firearms, Tobacco and Alcohol classifies explosives into improvised and manufactured. While an improvised explosive denotes utilization of weapons fabricated in small quantities, devices used outside of their intended purposes, or alternative materials; a manufactured explosive entails a standard, quality tested and mass produced weapon. It is important to note that if somebody with training in explosives designs an ‘improvised’ explosive device, it may be professional in form and its operation may be somewhat lethal. In fact, high quality improvised explosive devices may bear a resemblance to military weapons both in appearance and effect (Bailey and Murray, 1989). The degree and patterns of blast injuries depend upon many factors including the peak of the original positive wave, which relates directly with the explosion magnitude and with a victim’s proximity to the explosion; distance from the incident blast wave; overpressure duration; and the number and nature of reflections in enclosed areas and with reflecting walls. Another significant factor that characterizes the degree and patterns of blast injury is the medium in which the blast occurs. An underwater blast wave, unlike a blast wave in the air, causes extremely more damage owing to the fact that water is basically incompressible (Landsberg, 2000). Moreover, a wave ensuing from an underwater blast moves faster and travels farther as compared to a wave from an analogous explosion in the air. Blast injuries in water consequently take place at greater expanse and their severity may be much more than the injuries from a blast wave in the air. Studies have revealed that personnel walking on water are at higher abdominal injury risk than thoracic injury ensuing from an underwater explosion, while victims who are fully submerged are at equal risk of collective abdominal and thoracic blast injuries (Petri, et al., 2001). The injury patterns that blast waves produce are related to both the medium via which they travel and a victim’s body position with regard to deflecting or reflecting objects that the wave strikes. Explosions within or near hard solid surfaces for instance become magnified two to nine times as the shock wave is reflected. Generally, victims franked by the blast and a building in effect suffer two to three times the extent of injury that a blast victim in an open location would suffer (Rice and Heck, 2000). Worthy noting is the fact that if a blast victim is near a reflecting surface like a building or a solid wall, or is in a confined area, a blast wave can be lethal contrary to when he or she would be in the open. Blast injury in open air has a lethality of approximately 7.8 percent on the whole, but when the blast takes place in confined spaces, this shoots to forty-nine percent. In effect, seventy percent of blast victims in confined spaces usually sustain minor soft tissue injuries while roughly eleven percent of the victims suffer traumatic amputations – these act as severe multisystem trauma markers as well as markers of the subsequent high mortality (Hull and Cooper, 1996). In the event of an explosive detonation, body armour offers a deceptive sense of security – a medical provider must not presume that body armour offered a blast victim protection from explosion-related injuries. As Wightman and Gladish (2001) explain, although body armour offers the victim protection from fragments from an explosive device, and to a lesser degree, objects that the blast wave picks up and flung, it also avails a reflecting surface capable of concentrating the explosion power as the blast wave reflects off on the front and back of the armour. All the same, in view of the fact that the mass of explosive device-caused injuries ensue from secondary objects that the blast wave flung, the merits of body armour to a large extent outweigh the risk of the blast wave enhancement (Nerenberg, Makris and Klein, 2000). Conventionally, blast injuries are in four categories namely primary, secondary, tertiary and lastly, quaternary/miscellaneous injuries. A blast victim may be suffering injuries from more than one of these mechanisms. A primary blast injury solely results from the direct impact of blast overpressure on a victim’s tissue. Unlike water, air is easily compressible and thus, nearly always, a primary blast injury affects air-filled structures including the ear, lung as well as gastrointestinal tract (Pennardt and Lavonas, 2010). Only high explosives have the potential of causing primary blast injuries due to the blast wave’s direct effects on the human body – low-order explosives cannot trigger off primary blast injury since they do not generate a supersonic blast wave. This disparity is the only evident clinical variation between wounds that a low order explosive causes and those that a high order explosive causes. Primary blast injuries’ overall incidence is roughly twenty percent, and their victims nearly always have other injury types such as blunt trauma ensuing from impact on stationary objects or penetrating wounds ensuing from flying debris (Cernak, et al., 1999). As Wightman and Gladish (2001) explain, the most probable primary blast injury mechanism is the irreversible work effect connected to the variations in tissue tensile strength and blast wave speed through the various tissues. The damage onset takes place when the blast wave compresses a victim’s tissues. The ensuing forces surpass the material’s tensile strength thus causing shearing of vascular beds, gastrointestinal haemorrhages, and pulmonary contusions as the tissues are expanded and compressed (Cooper, Townsend and Cater, 2001). Wightman and Gladish (2001) further explains that in every non-penetrating blast trauma, some combination of shear and stress waves is possible – stress that surpasses tissue tensile strength possibly prevails when blast surface loading goes above 80 to 90 m/sec in velocity. As aforementioned, the common organ systems that suffer primary blast injury include the ear, the gastrointestinal tract and the respiratory tract, with the ear being the most easily damaged. All the same, ear damage is the easiest to protect. Its structures are designed to gather and amplify sounds in such a way that the tympanic membrane moves with the sounds. Regrettably, they as well gather and amplify pressure waves and the human eardrum may rapture at a pressure of approximately thirty-five kilopascals. Indeed, nearly all eardrums will be ruptured with an overpressure of a hundred kilopascals. At slighter pressures, haemorrhage into the drum may result from the overpressure, but without a rupture. Moreover, extremely high pressures may destroy the drum and may fracture or dislocate the ossicles. Eardrum rupture causes hearing loss, pain and may cause tinnitus, which may in turn interfere with the victim’s quality of life (Cohen, et al., 2002). Gastrointestinal (GI) blast injuries may not be visible externally, have a great potential of causing death and may be much harder to shield against. Primary blast injury of the GI is inconsistent in presentation – may comprise haemorrhage underneath the visceral peritoneum, or may broaden into the cecum, mesentery and colon. The colon is the common-most site of both perforation and haemorrhage, which is thought to be due to the colon having, in the GI tract, the most bowel gas accumulation (Sharpnack, Johnson and Phillips, 1991). The lungs are susceptible to damage particularly owing to the far-reaching lung/air tissue interfaces. High explosives generate supersonic pressure waves that are directly responsible for blast lung/pulmonary blast, which is the most common lethal primary blast injury. Pulmonary blast injuries may not be visible outwardly or instantly, but if their diagnosis and treatment is not done promptly, the victim may culminate into death. An overpressure of roughly 280 kilopascals causes lung injuries (Yelverton, 1997). Lungs damage can encompass pulmonary contusions, inclusive or exclusive of a laceration, and pulmonary barotrauma like subcutaneous emphysema, pneumothorax, pneumomediastinum, or pulmonary interstitial emphysema. Pulmonary contusion is the most common blast-wave associated lung injury, and may assume the form of micro-haemorrhages with peribronchial/perivascular disruption. The wall of alveolar may tear, instigating a blood-filled emphysematous alteration to the lung (Sharpnack, Johnson and Phillips, 1991). Below is a chest x-ray showing primary blast injury of the lung ensuing in pulmonary contusions portrayed as infiltrates under the left wall of the chest. Source: Wightman J. (n.d.). Blast injuries: Recognition and management. Primary blast injuries are also characterized by solid organ laceration as well as testicular rupture, although they are less common and frequently related to huge blast forces. Primary blast injury can also cause traumatic brain injury or concussion, although this finding is tricky to tell from the concussion resulting from impact with other objects. In addition, myocardial contusion brings about either hypotension or arrhythmia, despite the heart being well protected plus not subject to the fluid/air shear of primary blast injury (Wightman and Gladish, 2001). As Pennardt and Lavonas (2010) point out, flying objects under the impact of a blast waves strike victims in the surroundings thereby causing secondary blast injury. In other words, blast fragments plus other debris propelled by the explosion’s intense energy release causes secondary blast injuries on victims. With the increase in distance from the blast epicentre, the blast’s impact lessens and the impact of debris and shrapnel (fragments) propelled by the explosive attains significance. These flying projectiles, depending on their sizes and the velocity at which they travel, produce both blunt and penetrating trauma. With these velocities, the debris can struck and injure individuals far from an explosion scene along with those in close proximity to it. For instance, after the 1998 US Embassy terrorist bombing in Nairobi, victims up to two kilometres away sustained wounds from flying glass (Wightman and Gladish, 2001). In blast victims, secondary blast injury is indeed the common-most death cause. While intra-abdominal and thoracic injuries may occur whenever fragments penetrate, exposed areas including the neck, head and extremities often suffer penetrating injuries. Majority of the secondary blast injuries result from glass, and frequently, victims peppered with glass are harder to differentiate from those peppered with glass and at the same time have penetrating injuries (Almogy, et al., 2002). The diagram below clearly evidences the fact that secondary blast injuries cannot at times be initially noticeable – an outwardly tiny wound or abrasion may mask a substantial fragment’s entrance wound – the diagram features multiple bolts in a victim’s chest. These bolts were part of the explosion device and their purpose was to inflict as much damage to human as possible. The imparted force was ample to make them penetrate the victim. Source: Gimmon, 2006. Pictures from Israel: An x-ray taken after a suicide bombing in Jerusalem. A tertiary blast injury on the other hand is a characteristic of high-energy explosions and takes place when individuals fly through the air thus striking other objects (Pennardt and Lavonas, 2010). They occur when the blast winds propel the victim’s body into another object. Tertiary effects ensue from the bulk gas flow away from the explosion. They occur most frequently when the victim is somewhat close to the blast epicentre. Similarly, victim’s displacement can occur relatively far from the detonation point in case the victim is regrettably in the path where gases must take to escape from an enclosed structure, including a window, hatch, doorway, or in an alley. Majority of tertiary injuries result from the deceleration that the impact into a rigid structure causes. Fractures and closed head injuries are the most common injuries. Additionally, tertiary blast injuries are dependent on what the victim hits in the surroundings. Victims may topple along the ground sustaining contusions, abrasions as well as ‘road-rash’ (Stapczynski, 1982). Quaternary or miscellaneous blast injury takes in all other injuries that explosions cause, which include toxic inhalations (eg. Carbon monoxide and inhalation of chemicals or dust from the explosion), crush injuries and fire or radiation. A good instance for explaining this is the two jet airplanes’ crash into the World Trade Centre that only generated a somewhat low-order pressure wave, but the building collapse and resulting fire killed thousands. Although the human body can unshielded survive a blast with a peak overpressure of 210 kilopascals, buildings plus other structures collapse with pressure of just a few pounds per square inch, which signifies that individuals can survive the blast’s impact, only to receive injuries from collapsing buildings (Pennardt and Lavonas, 2010). For effective examination of blast injuries, forensic investigators should put into account the following steps: they should ensure that all body parts and clothing are recovered from the blast scene – clothing is submitted either in air tight containers such as unused paint can, or in bags composed of polypropylene, polyester or nylon. The investigators should also note the direction of projectile injury. They should also examine victims’ hands in order to determine whether their hands were holding explosives. This is in addition to collecting the explosive residue, whether burned (gray or black) or unburned (yellow, gray or brown); fingernail scrapings; hair; and swabs of skin. They should also collect from within wound tracks and skin surface and, or radiolucent material, which may be part of explosive. Full-body photographs as well as full-body radiographs are very important – forensic experts must collect all radio-opaque fragments. These can be an explosive device’s components, metallic structures from the vicinity or parts of body prosthesis. Radiographs are repeated to ensure that all fragments have been recovered. Additionally, forensic investigators should conduct toxicological analysis (Shkrum and Ramsay, 2007). Conclusion Apparently, blasts are a major threat to humanity. Whenever they occur, they not only cause damage to objects in their proximity, but also cause death over and above inflicting severe injuries to victims in the surroundings. Forensic experts should be among the first to arrive at a blast scene. They should ensure that they protect the scene and collect everything that would aid them in conducting their investigations regarding the blast. Additionally, they should examine blast injuries on the victims upon which they should be in a position to identify the nature of the blast injuries that the victims have sustained. That is, whether primary, secondary, tertiary or quaternary/miscellaneous blast injuries. Moreover, forensic experts have the responsibility of determining the nature of the explosives that caused the blast – whether high- order or low-order explosives and their subsequent blast wave strengths. This information would of great significance to medical experts attending to the blast victims, especially so considering the fact that not all blast injuries are instantly apparent. References Almogy, G., et al. (2002). Rectal penetrating injuries from blast trauma. Isr Med Assoc J, 4(7), 557-558. Bailey, A., & Murray, S. (1989). The chemistry and physics of explosions. Explosives, Propellants, and Pyrotechnics. London UK: Brassey. Cernak, I. et al., (1999). Blast injury from explosive munitions. J Trauma, 47(1), 96-103. Cohen, J.T, et al. (2002). Blast injury of the ear in a confined space explosion: auditory and vestibular evaluation. Isr Med Assoc J, 4(7), 559-562. 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Scientific foundations of Trauma. Oxford, UK: Butterworth-Heinemann, 189-199. Read More