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Ballistics for the EMS Provider How guns work, what they can do, and how to treat gun shot wounds. Jeff Brosius, B.S., NREMT-P, CCEMT-P. Basic Principles of Ballistics. Physics Firearm mechanics Bullet properties Tissue response to force Treatment. Basic Principles of Physics .
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Ballistics for the EMS Provider How guns work, what they can do, and how to treat gun shot wounds Jeff Brosius, B.S., NREMT-P, CCEMT-P
Basic Principles of Ballistics • Physics • Firearm mechanics • Bullet properties • Tissue response to force • Treatment
Basic Principles of Physics • Kinetic Energy is a function of mass and velocity • Force is a function of mass and acceleration/deceleration • Energy can not be created or destroyed, only changed from one form to another
Newton’s Laws of Energy • Kinetic Energy = ½ Mass x Velocity² • Force = mass x G (where G = Gravity Force • A body in motion will continue in motion until acted upon by an outside force (tissue, gravity, friction, solid object, etc.)
Firearm Mechanics • All firearms share some basic principles. • There is a barrel, which functions to direct the projectile in a certain direction. • There is a pin, which causes the powder in the bullet to ignite. • There is a trigger, which causes the pin to strike the bullet.
Firearm Mechanics, cont. • The bullet contains powder, which will burn rapidly, creating gas vapors. • These vapors expand inside the barrel, creating pressure. • The pressure forces the bullet out of the barrel. • The speed of the bullet depends on several factors (size, friction, etc.)
Bullet Characteristics • Caliber of the bullet (.22, .45, .357, 9mm, etc.) • Blunt vs. Hollow vs. Pointed end • Casing (unjacketed/full metal jacket) • Density of material
Tissue Response • Cavities – temporary and permanent • Temporary is larger than the size of the bullet, and is caused by compression of air around the projectile. • Permanent is the destroyed tissue from the bullet itself.
Cavities • The size of the cavity is not simply a factor of the bullet size. Other factors are important, but often unknown • Deflection • Yaw of bullet at impact • Speed of bullet at impact • Angle of impact • Range from gun to target
Cavity Formation Tissue Temporary Cavity
Tissue Response • Dense tissue will suffer more damage than hollow tissue. (Bone vs. lung) • Elastic tissue will suffer less damage than rigid tissue. (Muscle vs. liver) • Strong tissue will withstand damage better.
Treatment Goals • Safety!!!!!!!!!!!!!!!!!! • ANY penetrating trauma should be treated with the utmost urgency. • A small hole on the outside might be hiding a large hole inside. • A large hole outside can mask massive internal damage.
Treatment Goals • ABCs, as always. • Rapid scene times… grab ‘em and get moving to the hospital. • Airway support to include intubation (more often needed for thorax injuries.) • Ventilatory support as needed. • IV enroute, fluids as protocol/Med Control requests.
Treatment Goals • Hemorrhage control if possible. • Occlusive dressings for sucking chest wounds. • Needle Thoracostomy as needed for tension pneumothorax. • Bilateral needle decompression ONLY in an intubated patient.
Treatment Goals • Early notification of the hospital. • Constant reassessment…A GSW to the chest can cause the patient’s condition to change RAPIDLY. Be vigilant. • Again, rapid transport is the single best method for treating a gunshot victim. • Nothing else will be as helpful as a physician and hospital trauma care.
Treatment Pitfalls • Wasting time looking for the bullet or shell casing. • Thinking that a small hole is not a major issue. • Wasting time trying to classify wounds as entrance or exit. • Closest facility vs. Closest appropriate facility. • Delaying transport for ANY reason, other than EMS crew safety.
Controversial Issues • Cervical Spine Immobilization. • Large volumes of fluid replacement. • Traumatic cardiac arrest treatment.
Acknowledgements • Andres M. Rubiano, MD • David H Livingston, MD, FACS • Manuel Sotelo, MD • Errington C. Thompson, MD • Eric D. Ladenheim, MD • M.L. Fakler, MD • Grady Memorial Hospital, Atlanta, GA • Emory University School of Medicine, Department of Surgery
Web Sites • ww.umds.ac.uk • http://medstat.med.utah.edu • http://igm.nlm.nih.gov/ • http://www.vnh.org/EWSurg/EWSTOC.html • http://internet.cybermesa.com/~jbm/ballistics/calculations.html • http://www.firearmstactical.com
Web Sites • http://www.iwba.com/ • http://www.milnet.com/milnet/weapons.htm • http://www.wwa.com/~dvelleux/html • http://www.vnh.org/EWSurg/EWSTOC.html
Final Words…. • Don’t waste time. What you can’t see will kill the patient. • Be safe. • Treat the patient. • Do not treat the bullet, and don’t waste time on details that don’t matter. • Understand that a .22 is just as lethal as a .357. • Don’t waste time.