Blast & Ballistics

Question 1

Define primary, secondary, tertiary and quaternary blast injuries:

Answer 1

PRIMARY
- Tissue injury secondary to shockwave/ overpressure
- Worst at tissue-air interface
—> eg. blast lung, ruptures tympanum, bowel perf, shear dissection of vessels, air embolism

SECONDARY
- Projectiles, thrown during negative pressure wave

TERTIARY
- Body being thrown, or crushed by a collapsed structure

QUATERNARY
- Other indirect
Eg. Burns, inhalation, asphyxiation, psychological etc.

Question 2

What is ‘blast lung’

Answer 2

Primary blast injury (ie. from overpressure/ shock wave)

Diffuse lung contusions
Pulmonary oedema
And sometimes, air embolism
—> lacerations and fistulae between alveoli and veins

Most common blast injury, after TM rupture.

Fatal +
No specific Tx

Question 3

What are the phases of a blast?

Answer 3

Detonation —>

Peak overpressure (primary blast injuries)
Continued positive pressure
Negative pressure (projectiles)

Return to atmospheric pressure.

Question 4

In which environment is a blast most damaging?
- Open air
- Enclosed space
- Underwater

Answer 4

Underwater!
—> denser, slower disappation, at peak overpressure/ positive pressure for longer

Open air is safest.

Question 5

Approach to the apparently uninjured blast victim:

Answer 5

Check tympanum
If TM damage, check CXR, for blast lung.

If isolated TM rupture only, can DC.
If ANY symptoms, admit.

TM most susceptible to injury, then lung.
If TM and lungs okay, unlikely to have other injury (eg. Vessels, intestinal, solid organ etc)

Question 6

History- taking for blast victim:

Answer 6

• Nature of explosive (high order like TNT, or low order like petrol bomb)
• Environment:
  —> Open air
  —> Enclosed
  —> Underwater
  (open air, injury less likely)
• Proximity to blast
• Projectiles at scene
• Victim thrown
• Structural collapse
• Noxious agents (eg. Cyanide)
• Casualty number

Patient:
(think in terms of 1,2,3,4-ternary blast injuries)
1 - TM symptoms
- Blast lung symptoms
- Air embolism symptoms
- Abdo pain
2- Penetrating/ blunt projectile trauma (consider as ballistics)
3- Crush
4- Burns, inhalation, chemical etc.