Mechanism of injury Flashcards
introduction
- trauma is primary cause of death and disability between ages 1-44 years
- analyzing a trauma scene is a vital skill
trauma
-injury occurs when an external source of energy affects the body beyond its ability to sustain and dissipate the energy
forms of energy
- different forms of energy produce different kinds of trauma
- mechanical energy
- chemical energy
- electrical energy
- barometric energy
biomechanics
Study of physiology and mechanics of living organisms
kinetics
Study of the relationship among speed, mass, direction of force, and physical injury caused by these factors
mechanism of injury (MIO)
- physical cause of the injury
- what happens outside the body
- assessment of how energy was introduced to the body
- suggest which organs/systems may be affected
- can direct assessment and treatment
biomechanics of trauma
- explains the physical results of the MOI
- what happens inside the body
factors affecting types of injury
- Ability of body to disperse energy delivered
- Force and energy
- duration and direction
- position of victim
force and energy: factors affection types of injury
− Size of object
− Velocity
− Acceleration or deceleration
− Affected body area
duration and direction: factors affecting types of injury
− The larger the area of force dissipation, the more pressure is reduced to a specific spot.
impact resistance
- impact resistance of body parts has a bearing on types of tissue disruption
- organs that have has inside are easily compressed
- liquid containing organs are less compressible
understand the effects of forces to help assess the mechanism of injury (MOI)
velocity (V)
distance per unit of time
acceleration (a)
rate of change of velocity
gravity (g)
downward acceleration imparted to any object moving toward earth
kinetic energy
1/2 (mass x velocity^2)
kinetics
- the KE of a car in motion that stops suddenly must be transformed or applied to another object
- other factors that will affect energy dissipation in a crash include:
- vehicles angle of impact
- differences in sizes of the 2 vehicles
- restraint status and protective gear of occupants
law of conservation of energy
-energy can neither be created nor destroyed
energy dissapation
- process by which KE is transformed into mechanical energy
- protective devices can manipulate the way in which energy is dissipated
newtons first law of motion
-a body at rest will remain at rest unless acted on by an outside force
newtons second law of motion
- the force of an object can exert is the product of its mass times its acceleration
- f= ma
force
- force = mass (weight) x acceleration (or deceleration)
- deceleration and acceleration can be measured in numbers of g force
blunt trauma
-injuries in which tissues are not penetrated by external object
motor vehicle crashes
- 5 phases of trauma
- phase 1- deceleration of the vehicle
- phase 2- deceleration of occupant
- phase 3- deceleration of internal organs
- phase 4- secondary collisions
- phase 5- additional impacts received by the vehicle
impact patterns: frontal or head on impacts
- front end of the car distorts
- passengers decelerate at same rate as vehicle
- abrupt deceleration injuries are produced by a sudden stop of a body forward motion
- unrestrained occupants usually follow one of 2 trajectories:
- down and under pathway
- up and over pathway
impact patterns: lateral or side impacts
- impart energy to the near side occupant
- seat belt offer little protection
- the body is pushed in 1 direction, while the head moves towards the impacting object
-impact patterns: rear impacts
- have the most survivors
- whiplash injury is common
- energy is imparted to the front vehicle
impact patterns: rotational or quarter panel impacts
- occurs when a lateral crash is off center
- the vehicle forward motion stops, but the side continues in rotational motion
impact patterns: rollovers
- patients may be ejected
- patients may be struck hard against the interior of the vehicle
- worst scenario bc no protection
restrained vs unrestrained occupants
- seat belts stop the motion of an occupant traveling at the same speed as the vehicle
- associated injuries include cervical fractures and neck sprains
air bags
- have reportedly reduced deaths in direct frontal crashes by about 30%
- can also result in secondary injuries:
- direct contact
- chemicals
motorcycle crashes
- any structural protection afforded to victims is derived from protective devices worn by the rider
- helmet
- leather or abrasion resistant clothing
- boots
- attention should be given to:
- deformity of motorcycle
- side damaged
- distance of skid
- deformity of objects or vehicles
- helmet deformity
four types of motorcycle impact
- head on impact
- angular impact
- ejected
- laying the bike down
when helmet should be removed
- helmet should be removed carefully if:
- airway management techniques cannot be performed with the helmet in place
- helmet should be cut if it cannot be removed without further deformation
3 predominant MOIs for pedestrains
- 1st impact- auto strikes body with its bumpers
- 2nd impact- adult is thrown on hood and/or grille of vehicle
- 3rd impact- body strike the ground or some other object
waddell triad
- pattern of injuries in children and people of short stature
- bumper hits pelvis and femur
- chest and abdomen hit grille
- head strikes vehicle and ground
- more likely to go under, hit head on ground, or hit grille
falls from heights
- severity of injuries impacted by:
- height
- position
- surface
- physical condition
penetrating trauma
- involves disruption of skin and tissues in a focused area
- low velocity- caused by sharp edges
- medium and high velocity- object might flatten out, tumble, or ricochet
- middle- handgun
- high- riffle
most common penetrating injury
-caused by firearms
stab wounds
- severity depends on:
- anatomic area involved
- depth of penetration
- blade length
- angle of penetration
gunshot wounds
- the most important factor for seriousness of wound is type of tissue involved
- entry wound is characterized by the effects of the initial contact and implosion
- severity depends on:
- type of firearm
- velocity of projectile
- physical design/size of projectile
- distance of victim from muzzle
- type of tissue struck
handgun wounds
- revolver holds 6-10 rounds of ammunition
- pistol holds up to 17 rounds of ammunition
- accuracy is limited
shotguns
- fire round pellets
- shallower
rifles wounds
- fire single projectile at a very high velocity
- impart a spin for accuracy
- longer barrel = more accurate
- can go further into the body
- high velocity
deformation/tissue destruction: gunshot wounds
- deformation/tissue destruction is based on:
- density
- compressibility
- missile velocity
- missile fragmentation
projectile creates a permanent cavity
-may be straight line or irregular pathway
pathway expansion
-tissue displacement that results from low displacement sonic pressure
missile fragmentation
-projectile sends off fragments that create paths through tissues
exit wounds
- exit wounds occur when projectile energy is not entirely dissipated
- size depends on energy dissipated and degree of cavitation
- exit wound is larger, can be burns, more surface area
wounding potential
- wounding potential depends on:
- powder charge
- size and number of pellets
- dispersion of the pellets
- range at which the weapon was fired
- barrel length (long = more accuracy)
- type of choke at the end of the barrel
- shorter barrel -> more dispersion
when assessing gunshot wounds
- obtain weapon used, range fired, bullet used
- look for powder residue around the wound
- entrance and exit wounds
primary blast injuries
- damage is caused by pressure wave generated by explosion
- close proximity to the origin of the pressure wave carries a high risk of injury or death
- can rupture membranes and affect organs
-secondary blast injuries
- result from being struck by flying debris
- a blast wind occurs
- flying debris may cause blunt and penetration injuries
- most common
- b
tertiary blast injuries
- occur when a person is hurled against stationary, rigid objects
- ground shock
- amputations, broken bones, penetrations
ground shock
-physical displacement when the body impacts the ground
quaternary blast injury
- occur from the miscellaneous events that occur during an explosion
- may include:
- burns
- respiratory injury
- crush injury
- entrapment
quinary blast injuries
- caused by biologic, chemical, or radioactive contaminants added to an explosive
- associated with dirty bombs
physics of an explosion
- speed, duration, and pressure of the shock wave are affected by:
- size of the explosive charge
- nature of surrounding medium
- distance from explosion
- presence or absence of reflecting surface
explosion is more damaging in closed spaces
true
blast pressures cause destruction at
- interface between tissues of different densities
- interface between tissues and trapped air
tissue at risk
- air containing organs are more susceptible to pressure changes (lungs) -> primary blast
- junctions between tissues of different densities and exposed tissue are prone
- the ear is most sensitive (pressure)
- primary pulmonary blast injuries occur as contusions and hemorrhages
- if there is any reason to suspect lung injury in a blast victim -> administer oxygen
assessment/management of blast injuries
- if scene safety cannot be ensured, evacuate until advised that it is safe
- assess for other hazards
- form a general impression as you approach
- assess breath sounds frequently
- examine for the presence of DCAP-BTLS
- establish a baseline pulse oximetry value
