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 Handguns, by the Numbers Caliber Velocity Muzzle Energy Energy at 45 feet Ft/sec .25 810 73 60 .32 745 140 120 .357 1410 540 475 .38 855 255 255 .40 985 390 365 .44 1470 1150 875 .45 850 370 350 9 mm 935 345 315 Rifles, by the Numbers Caliber Velocity Muzzle Energy Energy at 300 ft .22 Hornet 3770 1735 1262 .243 3500 1725 1285 M-16 3650 1185 805 Uzi 1500 440 277 (150 ft) AK-47 3770 1735 1262 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 M-16 Rifle Wound NATO 7.62 Wound .22 Long Rifle Wound AK-74 Rifle Wound .22 cal Hollow Point Wound 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. Pictures of injuries from firearms…. 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. Questions?