Blast injury
Encyclopedia
A blast injury is a complex type of physical trauma
resulting from direct or indirect exposure to an explosion
. Blast injuries occur with the detonation
of high-order explosives as well as the deflagration
of low order explosives. These injuries are compounded when the explosion occurs in a confined space.
waves, or shock wave
s. These are especially likely when a person is close to an exploding munition, such as a land mine. The ears are most often affected by the overpressure, followed by the lungs and the hollow organs of the gastrointestinal tract. Gastrointestinal injuries may present after a delay of hours or even days. Injury from blast overpressure is a pressure and time dependent function. By increasing the pressure or its duration, the severity of injury will also increase.
In general, primary blast injuries are characterized by the absence of external injuries; thus internal injuries are frequently unrecognized and their severity underestimated. According to the latest experimental results, the extent and types of primary blast-induced injuries depend not only on the peak of the overpressure, but also other parameters such as number of overpressure peaks, time-lag between overpressure peaks, characteristics of the shear fronts between overpressure peaks, frequency resonance, and electromagnetic pulse, among others. There is general agreement that spall
ing, implosion, inertia, and pressure differentials are the main mechanisms involved in the pathogenesis of primary blast injuries. Thus, the majority of prior research focused on the mechanisms of blast injuries within gas-containing organs/organ systems such as the lungs, while primary blast-induced traumatic brain injury
has remained underestimated. Blast lung refers to severe pulmonary contusion
, bleeding or swelling
with damage to alveoli and blood vessels, or a combination of these. It is the most common cause of death among people who initially survive an explosion.
and other objects propelled by the explosion. These injuries may affect any part of the body and sometimes result in penetrating trauma
with visible bleeding. At times the propelled object
may become embedded in the body, obstructing the loss of blood to the outside. However, there may be extensive blood loss within the body cavities
. Shrapnel
wounds may be lethal and therefore many anti-personnel
bombs are designed to generate shrapnel and fragments.
Most casualties are caused by secondary injuries. Some explosives, such as nail bomb
s, are deliberately designed to increase the likelihood of secondary injuries. In other instances, the target provides the raw material for the objects thrown into people, e.g., shattered glass from a blasted-out window or the glass facade
of a building.
s and coup contre-coup injuries
.
Young children, because they weigh less than adults, are at particular risk of tertiary injury.
s, crush injuries
and respiratory injuries.
Traumatic amputations quickly result in death, and are thus rare in survivors, and are often accompanied by significant other injuries. The rate of eye injury
may depend on the type of blast. Psychiatric injury, some of which may be caused by neurological damage incurred during the blast, is the most common quaternary injury, and post-traumatic stress disorder
may affect people who are otherwise completely uninjured.
overpressure shock wave, while low order explosives deflagrate (subsonic
combustion
) and do not produce an overpressure wave. A blast wave
generated by an explosion starts with a single pulse of increased air pressure, lasting a few millisecond
s. The negative pressure (suction
) of the blast wave follows immediately after the positive wave. The duration of the blast wave, i.e., the time an object in the path of the shock wave is subjected to the pressure effects, depends on the type of explosive material
and the distance from the point of detonation. The blast wave progresses from the source of explosion as a sphere of compressed and rapidly expanding gases, which displaces an equal volume of air at a very high velocity
. The velocity of the blast wave in air may be extremely high, depending on the type and amount of the explosive used. Indeed, while a hurricane-force wind (approximately 200 km/h) exerts only 0.25 PSI
overpressure (i.e. 1.72 kPa
), a lethal blast-induced overpressure of 100 PSI (i.e. 690 kPa) travels with a velocity of approximately 1500 mph (i.e. 2414 km/h). An individual in the path of an explosion will be subjected not only to excess barometric pressure, but to pressure from the high-velocity wind traveling directly behind the shock front of the blast wave. The magnitude of damage due the blast wave is dependent on: 1) the peak of the initial positive pressure wave (bearing in mind that an overpressure of 60-80 PSI or 414-552 kPa is considered potentially lethal); 2) the duration of the overpressure; 3) the medium in which it explodes; 4) the distance from the incident blast wave; and 5) the degree of focusing due to a confined area or walls. For example, explosions near or within hard solid surfaces become amplified two to nine times due to shock wave reflection. As a result, individuals between the blast and a building generally suffer two to three times the degree of injury compared to those in open spaces.
and potential neurological
consequences. Its complex clinical syndrome is caused by the combination of all blast effects, i.e., primary, secondary, tertiary and quaternary blast mechanisms. It is noteworthy that blast injuries usually manifest in a form of polytrauma, i.e. injury involving multiple organs or organ systems
. Bleeding from injured organs such as lungs or bowel causes a lack of oxygen
in all vital organs, including the brain. Damage of the lungs reduces the surface for oxygen uptake from the air, reducing the amount of the oxygen delivered to the brain. Tissue destruction initiates the synthesis and release of hormones or mediators into the blood which, when delivered to the brain, change its function. Irritation of the nerve endings in injured peripheral tissue and/or organs also significantly contributes to blast-induced neurotrauma
.
Individuals exposed to blast frequently manifest loss of memory
for events before and after explosion, confusion, headache, impaired sense of reality, and reduced decision-making ability. Patients with brain injuries acquired in explosions often develop sudden, unexpected brain swelling
and cerebral vasospasm
despite continuous monitoring. However, the first symptoms of blast-induced neurotrauma (BINT) may occur months or even years after the initial event, and are therefore categorized as secondary brain injuries
. The broad variety of symptoms includes weight loss, hormone imbalance
, chronic fatigue, headache, and problems in memory, speech and balance
. These changes are often debilitating, interfering with daily activities. Because BINT in blast victims is underestimated, valuable time is often lost for preventive therapy and/or timely rehabilitation.
Trauma (medicine)
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
resulting from direct or indirect exposure to an explosion
Explosion
An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...
. Blast injuries occur with the detonation
Detonation
Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases...
of high-order explosives as well as the deflagration
Deflagration
Deflagration is a term describing subsonic combustion that usually propagates through thermal conductivity; hot burning material heats the next layer of cold material and ignites it. Most "fire" found in daily life, from flames to explosions, is deflagration...
of low order explosives. These injuries are compounded when the explosion occurs in a confined space.
Classification
Blast injuries are divided into four classes: primary, secondary, tertiary, and quaternary.Primary injuries
Primary injuries are caused by blast overpressureOverpressure
The term Overpressure is applied to a pressure difference, relative to a "normal" or "ambient" pressure, in various circumstances:* In engineering: the pressure difference over the wall thickness of a pressure vessel...
waves, or shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
s. These are especially likely when a person is close to an exploding munition, such as a land mine. The ears are most often affected by the overpressure, followed by the lungs and the hollow organs of the gastrointestinal tract. Gastrointestinal injuries may present after a delay of hours or even days. Injury from blast overpressure is a pressure and time dependent function. By increasing the pressure or its duration, the severity of injury will also increase.
In general, primary blast injuries are characterized by the absence of external injuries; thus internal injuries are frequently unrecognized and their severity underestimated. According to the latest experimental results, the extent and types of primary blast-induced injuries depend not only on the peak of the overpressure, but also other parameters such as number of overpressure peaks, time-lag between overpressure peaks, characteristics of the shear fronts between overpressure peaks, frequency resonance, and electromagnetic pulse, among others. There is general agreement that spall
Spall
Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure...
ing, implosion, inertia, and pressure differentials are the main mechanisms involved in the pathogenesis of primary blast injuries. Thus, the majority of prior research focused on the mechanisms of blast injuries within gas-containing organs/organ systems such as the lungs, while primary blast-induced traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
has remained underestimated. Blast lung refers to severe pulmonary contusion
Pulmonary contusion
A pulmonary contusion is a contusion of the lung, caused by chest trauma. As a result of damage to capillaries, blood and other fluids accumulate in the lung tissue. The excess fluid interferes with gas exchange, potentially leading to inadequate oxygen levels...
, bleeding or swelling
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
with damage to alveoli and blood vessels, or a combination of these. It is the most common cause of death among people who initially survive an explosion.
Secondary injuries
Secondary injuries are due people being injured by shrapnelShrapnel
Shrapnel shells were anti-personnel artillery munitions which carried a large number of individual bullets close to the target and then ejected them to allow them to continue along the shell's trajectory and strike the target individually. They relied almost entirely on the shell's velocity for...
and other objects propelled by the explosion. These injuries may affect any part of the body and sometimes result in penetrating trauma
Penetrating trauma
Penetrating trauma is an injury that occurs when an object pierces the skin and enters a tissue of the body, creating an open wound. In blunt, or non-penetrating trauma, there may be an impact, but the skin is not necessarily broken. The penetrating object may remain in the tissues, come back out...
with visible bleeding. At times the propelled object
Projectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....
may become embedded in the body, obstructing the loss of blood to the outside. However, there may be extensive blood loss within the body cavities
Body cavity
By the broadest definition, a body cavity is any fluid-filled space in a multicellular organism. However, the term usually refers to the space located between an animal’s outer covering and the outer lining of the gut cavity, where internal organs develop...
. Shrapnel
Fragmentation (weaponry)
Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonating high explosive filling. The correct technical terminology for these casing pieces is fragments , although shards or splinters can be used for non-preformed fragments...
wounds may be lethal and therefore many anti-personnel
Anti-personnel weapon
An anti-personnel weapon is one primarily used to incapacitate people, as opposed to attacking structures or vehicles.The development of defensive fortification and combat vehicles gave rise to weapons designed specifically to attack them, and thus a need to distinguish between those systems and...
bombs are designed to generate shrapnel and fragments.
Most casualties are caused by secondary injuries. Some explosives, such as nail bomb
Nail bomb
The nail bomb is an anti-personnel explosive device packed with nails to increase its wounding ability. The nails act as shrapnel, leading almost certainly to greater loss of life and injury in inhabited areas than the explosives alone would. The nail bomb is also a type of flechette weapon...
s, are deliberately designed to increase the likelihood of secondary injuries. In other instances, the target provides the raw material for the objects thrown into people, e.g., shattered glass from a blasted-out window or the glass facade
Facade
A facade or façade is generally one exterior side of a building, usually, but not always, the front. The word comes from the French language, literally meaning "frontage" or "face"....
of a building.
Tertiary injuries
Displacement of air by the explosion creates a blast wind that can throw victims against solid objects. Injuries resulting from this type of traumatic impact are referred to as tertiary blast injuries. Tertiary injuries may present as some combination of blunt and penetrating trauma, including bone fractureBone fracture
A bone fracture is a medical condition in which there is a break in the continuity of the bone...
s and coup contre-coup injuries
Coup contrecoup injury
In head injury, a coup injury occurs under the site of impact with an object, and a contrecoup injury occurs on the side opposite the area that was impacted. Coup and contrecoup injury is associated with cerebral contusion, a type of traumatic brain injury in which the brain is bruised. Coup and...
.
Young children, because they weigh less than adults, are at particular risk of tertiary injury.
Quaternary injuries
Quaternary injuries, or other miscellaneous named injuries, are all other injuries not included in the first three classes. These include flash burnFlash burn
Flash burn can mean:*Arc eye, also called corneal flash burn*The effect that in a nuclear explosion of sufficient magnitude, the majority of damage is done by light and thermal radiation...
s, crush injuries
Crush syndrome
Crush syndrome is a medical condition characterized by major shock and renal failure after a crushing injury to skeletal muscle...
and respiratory injuries.
Traumatic amputations quickly result in death, and are thus rare in survivors, and are often accompanied by significant other injuries. The rate of eye injury
Eye injury
Physical or chemical injuries of the eye can be a serious threat to vision if not treated appropriately and in a timely fashion. The most obvious presentation of ocular injuries is redness and pain of the affected eyes. This is not, however, universally true, as tiny metallic projectiles may cause...
may depend on the type of blast. Psychiatric injury, some of which may be caused by neurological damage incurred during the blast, is the most common quaternary injury, and post-traumatic stress disorder
Post-traumatic stress disorder
Posttraumaticstress disorder is a severe anxiety disorder that can develop after exposure to any event that results in psychological trauma. This event may involve the threat of death to oneself or to someone else, or to one's own or someone else's physical, sexual, or psychological integrity,...
may affect people who are otherwise completely uninjured.
Mechanism
High-order explosives produce a supersonicSupersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...
overpressure shock wave, while low order explosives deflagrate (subsonic
Subsonic
Subsonic may refer to:*Any speed lower than the speed of sound within a sound propagating medium is called subsonic*Subsonic aircraft, a flying machine that flies at air speeds lower than the speed of sound...
combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
) and do not produce an overpressure wave. A blast wave
Blast wave
A blast wave in fluid dynamics is the pressure and flow resulting from the deposition of a large amount of energy in a small very localised volume. The flow field can be approximated as a lead shock wave, followed by a 'self-similar' subsonic flow field. In simpler terms, a blast wave is an area of...
generated by an explosion starts with a single pulse of increased air pressure, lasting a few millisecond
Millisecond
A millisecond is a thousandth of a second.10 milliseconds are called a centisecond....
s. The negative pressure (suction
Suction
Suction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not...
) of the blast wave follows immediately after the positive wave. The duration of the blast wave, i.e., the time an object in the path of the shock wave is subjected to the pressure effects, depends on the type of explosive material
Explosive material
An explosive material, also called an explosive, is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure...
and the distance from the point of detonation. The blast wave progresses from the source of explosion as a sphere of compressed and rapidly expanding gases, which displaces an equal volume of air at a very high velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
. The velocity of the blast wave in air may be extremely high, depending on the type and amount of the explosive used. Indeed, while a hurricane-force wind (approximately 200 km/h) exerts only 0.25 PSI
Pounds per square inch
The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...
overpressure (i.e. 1.72 kPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
), a lethal blast-induced overpressure of 100 PSI (i.e. 690 kPa) travels with a velocity of approximately 1500 mph (i.e. 2414 km/h). An individual in the path of an explosion will be subjected not only to excess barometric pressure, but to pressure from the high-velocity wind traveling directly behind the shock front of the blast wave. The magnitude of damage due the blast wave is dependent on: 1) the peak of the initial positive pressure wave (bearing in mind that an overpressure of 60-80 PSI or 414-552 kPa is considered potentially lethal); 2) the duration of the overpressure; 3) the medium in which it explodes; 4) the distance from the incident blast wave; and 5) the degree of focusing due to a confined area or walls. For example, explosions near or within hard solid surfaces become amplified two to nine times due to shock wave reflection. As a result, individuals between the blast and a building generally suffer two to three times the degree of injury compared to those in open spaces.
Neurotrauma
Blast injuries can cause hidden brain damageBrain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...
and potential neurological
Neurology
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
consequences. Its complex clinical syndrome is caused by the combination of all blast effects, i.e., primary, secondary, tertiary and quaternary blast mechanisms. It is noteworthy that blast injuries usually manifest in a form of polytrauma, i.e. injury involving multiple organs or organ systems
Biological system
In biology, a biological system is a group of organs that work together to perform a certain task. Common systems, such as those present in mammals and other animals, seen in human anatomy, are those such as the circulatory system, the respiratory system, the nervous system, etc.A group of systems...
. Bleeding from injured organs such as lungs or bowel causes a lack of oxygen
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
in all vital organs, including the brain. Damage of the lungs reduces the surface for oxygen uptake from the air, reducing the amount of the oxygen delivered to the brain. Tissue destruction initiates the synthesis and release of hormones or mediators into the blood which, when delivered to the brain, change its function. Irritation of the nerve endings in injured peripheral tissue and/or organs also significantly contributes to blast-induced neurotrauma
Nerve injury
Nerve injury is injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injury. Most systems attempt to correlate the degree of injury with symptoms, pathology and prognosis...
.
Individuals exposed to blast frequently manifest loss of memory
Amnesia
Amnesia is a condition in which one's memory is lost. The causes of amnesia have traditionally been divided into categories. Memory appears to be stored in several parts of the limbic system of the brain, and any condition that interferes with the function of this system can cause amnesia...
for events before and after explosion, confusion, headache, impaired sense of reality, and reduced decision-making ability. Patients with brain injuries acquired in explosions often develop sudden, unexpected brain swelling
Cerebral edema
Cerebral edema or cerebral œdema is an excess accumulation of water in the intracellular or extracellular spaces of the brain.-Vasogenic:Due to a breakdown of tight endothelial junctions which make up the blood-brain barrier...
and cerebral vasospasm
Vasospasm
Vasospasm refers to a condition in which blood vessels spasm, leading to vasoconstriction. This can lead to tissue ischemia and death . Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to...
despite continuous monitoring. However, the first symptoms of blast-induced neurotrauma (BINT) may occur months or even years after the initial event, and are therefore categorized as secondary brain injuries
Primary and secondary brain injury
Primary and secondary brain injury are ways to classify the injury processes that occur in brain injury. In traumatic brain injury , primary injury occurs during the initial insult, and results from displacement of the physical structures of the brain. On the other hand, secondary injury occurs...
. The broad variety of symptoms includes weight loss, hormone imbalance
Hormone imbalance
Hormones are the chemical messengers in the body that travel the bloodstream to the organs and tissues. They slowly work and affect many of the body's processes over time. Endocrine glands, which are special groups of cells, make hormones....
, chronic fatigue, headache, and problems in memory, speech and balance
Equilibrioception
Equilibrioception or sense of balance is one of the physiological senses. It helps prevent humans and animals from falling over when walking or standing still. Balance is the result of a number of body systems working together: the eyes , ears and the body's sense of where it is in space ideally...
. These changes are often debilitating, interfering with daily activities. Because BINT in blast victims is underestimated, valuable time is often lost for preventive therapy and/or timely rehabilitation.
Further reading
- McSwain NE, Frame S, 2003. PHTLS Basic and Advanced Prehospital Trauma Life Support, 5th ed., Mosby, St. Louis
- Benzinger T (1950). Physiological effects of blast in air and water. In German Aviation Medicine, World War II (Vol. 2, pp. 1225-1229). Washington DC: Department of the Air Force.
- Cernak I, Savic VJ, Ignjatovic D, Jevtic M (1999). Blast injury from explosive munitions. J Trauma, 47(1), 96-103; discussion 103-104.
- Cernak I, Savic VJ, Zunic G, Pejnovic N, Jovanikic O, Stepic V (1999). Recognizing, scoring, and predicting blast injuries. World J Surg, 23(1), 44-53.
- Cernak I, Savic VJ, Kotur J, Prokic V, Veljovic M, Grbovic D (2000). Characterization of plasma magnesium concentration and oxidative stress following graded traumatic brain injury in humans. J Neurotrauma, 17(1), 53-68.
- Cernak I, Savic VJ, Lazarov A, Joksimovic M, Markovic S (1999). Neuroendocrine responses following graded traumatic brain injury in male adults. Brain Inj, 13(12), 1005-1015.
- Cernak I, Wang Z, Jiang J, Bian X, Savic J (2001a). Cognitive deficits following blast injury-induced neurotrauma: possible involvement of nitric oxide. Brain Inj, 15(7), 593-612.
- Cernak I, Wang Z, Jiang J, Bian X, Savic J (2001b). Ultrastructural and functional characteristics of blast injury-induced neurotrauma. J Trauma, 50(4), 695-706.
- Chiffelle TL (1966). Pathology of direct air-blast injury. In Technical Progress Report DA-49-146-XY-055. Washington DC: Defense Atomic Support Agency, Department of Defense.
- Clemedson CJ (1956). Blast injury. Physiol. Rev., 36, 336-354.
- Dedushkin VS, Kosachev ID, Tkachenko SS, Shapovalov, VM (1992). [Rendering medical care and the volume of the treatment of victims with blast injuries (a review of the literature)]. Voen Med Zh.(1), 13-18.
- Owen-Smith, MS (1981). Explosive blast injury. Med Bull US Army Eur, 38(7/8), 36-43.
- Phillips Y, Zajtchuk, JT (1989). Blast injuries of the ear in military operations. Ann Otol Rhinol Laryngol Suppl., 140, 3-4.
- Rice D, Heck J (2000). Terrorist bombings: Ballistics, patterns of blast injury and tactical emergency care. The Tactical Edge Journal, Summer, 53-55.
- Rossle, R (1950). Pathology of blast effects. In German Aviation Medicine, World War II (Vol. 2, pp. 1260-1273). Washington DC: Department of the Air Force.
- Saljo A, Bao F, Haglid KG, Hansson HA (2000). Blast exposure causes redistribution of phosphorylated neurofilament subunits in neurons of the adult rat brain. J Neurotrauma., 17(8), 719-726.