Wound Ballistic

Bomb & Blast Injury

Biophysics & Pathophysiology

Jim Ryan

WOUND BALLISTICS

The study of wounds caused by

penetrating missiles

Epidemiology - Civil

Incidence of GSW low in Europe

Pistols & shotguns

Increase in weapon range

Incidence of fragment wounds

Related to terrorism

Part of combined injury

GSW Right Shoulder

Typical Terrorist Wound Profile

Epidemiology - Military

Full range of weapons & systems

Fragment wounds predominate

Multiple wounds

Multiple systems

Part of combined injury

Multiple casualties

Military Assault Rifle Wound

Pre-formed Fragment Wounds

Basic Ballistics

Bullets

Low-energy Transfer (LeT)

High-energy Transfer (HeT)

Military

Jacketed

Civilian

Police

Hunting

The myth of Velocity

Kinetic energy = ½ mv²

Where m is mass

and v is velocity

Terrorist Fragments

High-energy Transfer (HeT)

High velocity bullets with retardation

High energy fragments

Shot gun

Solid slug

Close range

Wound Classification

Low-energy Transfer (HeT)

Low velocity (caveat)

Many hand guns

Perforating rifle bullets - <retardation

Stab wounds

Wound Classification

Mechanisms of Injury

Direct laceration & crushing

Cavitation (HeT)

Missile fragmentation / deformation

Contamination

Shock wave ??

Temporary Cavitation

1.Cadaver muscle

2.Indirect fractures

3.Opening of fascial

planes

4.Contamination

5.Fragmentation of the

missile

High-energy Transfer - Head

Hand Gun

High-energy Transfer - Abdomen

High-energy Transfer - Leg

Missile & bone fragmentation

Low-energy Transfer – Chest Assault Rifle

High-energy Transfer - Liver

Velocity – Energy irrelevant!

Multiple Fragments

Multiple hits

Multiple cavities

Clustering

Occult injury

Management

Management principles remain the

same

Do not Panic!

Summary

Treat the patient and wound,

not the weapon

Keep an open mind

Take a Short Break

An explosion is the phenomenon that

results from a sudden release in energy

Sources

1.Gunpowder or TNT

2.Chemical explosion

3.Pressurised steam in a boiler

4.Uncontrolled nuclear transformation

Explosions result in the sudden

release of energy. They form blast

waves (shock wave +blast wind)

and other physical phenomena

which may result in clinically

significant consequences

Significant Phenomena

1. Shock wave - overpressure

2. Blast wind – dynamic pressure

3. Disruption of the environment with generation of projectiles

4. Collapse of buildings – entrapment & crush

5. Thermal injury – flash & ignition

6. Inhalation of toxic fumes & smoke

Most damage caused by energised fragments

Simple physics of an explosion

Blast (wave) 2 elements:

– Shock wave

– Travels at >330m/s

– High overpressures

– Short duration

– Dynamic overpressure –

aka blast wind

– Moves things!

Heat from explosive

products

Shock wave

Edge of explosive products (Dynamic overpressure)

Bombs and explosions cause unique patterns of

injury seldom seen outside war and terrorism

The predominant post explosion injuries among

survivors involve standard penetrating and blunt

trauma

Blast Injuries: Variation in clinical consequences

Medium (air vs water)

Environment (open vs closed spaces)

297 Open space bombings v 93 bus bombings1

1 Leibovici J Trauma 1996

P<0.0001 4 18 Median ISS

P=0.00003 34.2% 77.5% Primary blast

injury

P<0.00001 7.8% 49% Mortality

SIGNIFICANCE OF

DIFFERENCE

OPEN AIR BOMB BUS BOMB

Overpressure reflection

At a surface, sound

pressure is doubled

For shock waves:

– overpressure at

surface may be up to 8

times incident

Reflection and

enhancement will lead to

very complex loading

Time, milliseconds

Ove

rpre

ssure

, kP

a

Atmospheric pressure

Initial shock wave

Shock reflections

Bomb blast injury

Consequences

Multisystem injury

Combined injury

Multiple casualties

Not for the novice

Blast Injuries: Types

Primary (caused by the blast shock wave)

Secondary (fragment acceleration – ballistic injury)

Tertiary (victim is thrown – disruption,disintegration)

Quaternary

– burns, smoke, chemicals

– toxins

– infection

– crush (collapsed buildings)

Primary Blast Injury:

Often absence of external injuries

Extensive parenchymal damage

– some immediate

– some delayed

Therefore, frequent underestimation and delayed

management of injuries

Primary effects – Clinical consequences

1.Blast lung - Acute lung injury (ARDS)

2.Pneumothorax, contusion

3.Bowel contusion/perforation

4.Ear injury

5.Other

Cardiac

CNS

Blast lung -

1.Rare in survivors

2.High index of

suspicion

3.Serial blood gases

4.Pulse oximetry

5.Ventilation - ITU

6.? steroids

Blast injury to bowel

Contusions to large and small

bowel

– occasional acute perforation Usually associated with primary lung

injury

Difficult to diagnose without

laporotomy

Risk of delayed perforation

Caused by shock wave (small)

and shear (large)

Bowel perforation

1.Rare in air blast

2.Common in water blast (water hammer)

3.High index of suspicion

4.Serial exams – CT, FAST, DPL

5.Contusion probably under-reported

Ear injury

1.Common

2.Under-reported

3.Deafness

4.Audiometry

5.Follow up

Other primary sequelae

1.Coronary artery air

embolism

2.Under-reported cause

of death

3.Also CNS air

embolism - stroke

Secondary effects – clinical consequences

1.Generation of fragments

- Primary

- Secondary

2.Penetrating ballistic injury

3.Multiple injuries & multi-system

4.Variable depth of penetration

5.Heavily contaminated

6.Commonest clinical problem

Fragment Injury

Tertiary effects – Clinical consequences

Blast wind

Displacement

- Environment

- The individual

Disruption

- Environment

- The individual

Other – Clinical Consequences

Crush Injury

Thermal

–Flash

– Ignition

– Inhalation

Psychological

–PTS Syndromes

–PTS Disorder

Management

1.ATLS Protocols

2.Penetrating injury predominates

3.Multiple systems

4.Need to prioritise-which injury first?

5.Need to understand underlying biophysics &

pathophysiology

Major Trauma

Multiple injuries

Multiple systems

Multiple victims

Lack of experience

Multi-Disciplinary

Multiple Injuries

Critical decision making

Priorities

Communication

‘Between two stools’

Ownership

Environment

Preparation

Pre-hospital

Transfer guidelines

Communication &

direction

Closest, appropriate

hospital

Preparation

In Hospital

Major incident plan

activated

Control room open

Triage team in place

Resus rooms manned

appropriately

Mobilisation of

resources & assets

Bombs & blast – common wound profiles

Interaction of blast waves with the body

Dynamic overpressure (gas flow)

– Flow shears tissue e.g. gross soft tissue injury

– Loads the body and body wall - displacement

– Avulse fractured limbs

– Burns from products

Primary Blast Injury:

Prediction of Severity?

Eardrum perforation as a marker of Pulmonary

Blast Injury? Israel 1999

Lab markers of severity of injury from blasts:

– IL-1

– TNF

– IL-6

– TxA2 Leukotriene

Bomb blast victim

What is this pathology ?

Summary

Treat the patient and wound,

not the weapon system

Keep an open mind & use

usual ATLS principles

Classification of blast injuries (1)

Primary - principally air containing organs

– Primary blast lung – 70psi

– Bowel injury

– Auditory – 2psi

– Some solid viscera

Secondary - wounds from fragments

– Penetrating - superficial to perforating

– Visceral injury from blunt impacts

Classification of blast injuries (2)

Tertiary

– Traumatic amputation of limbs

– Displacement of the body

– Tissue stripping by gas flow

Quaternary

– Crush injuries

– Burns

– Psychological

Quinternary

– Neurological – repeated TBI

– (Immuno-compromise)

DCR achieved by:

Aggressive approach to

– Hypovolaemia

– Hypotension

– Coagulopathy

– Hypothermia

– Acidosis

Near-patient diagnostics

Focussed abbreviated

surgery

Intensive/Critical Care

Dynamic overpressure (“Blast Wind”) Motion of explosive products

Associated with the shock wave at time of

detonation

– shock wave accelerates ahead very

quickly

Moves things due to gas flow

Gas flow (products)

Shock front (wave)

“War does not

determine who is right,

– Merely who is left”

Probability of Injury

Probability and type of trauma is related

to the casualty’s distance from the

epicenter of the detonation