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 CaliberVelocityMuzzle EnergyEnergy at 45 feet Ft/sec mm

Rifles, by the Numbers CaliberVelocityMuzzle EnergyEnergy at 300 ft.22 Hornet M Uzi (150 ft) AK

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 /calculations.html /calculations.html

Web Sites

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?