Mechanisms of Injury
Advanced First Aid
This gives the lesson plan for a 30 minute presentation on
Mechanisms of Injury
Introduction and Motivation
- [0:00] Aim:
- Be able to anticipate injuries from an accident scene
- Motivation
-
- Acts as a backup for survey skills: "I would have
expected more injury than I found -- what did I miss?"
- Impresses the heck out of bystanders
- Improves understanding of how, why and where injuries arise
Laws of Physics
- [02:00] Motion
- "A body in motion will remain in motion until acted on by
an outside force"
- Implications:
Describe forces involved in typical head-on restrained
car crash
- [06:00] Conserving energy
- Conservation: energy changes between forms but cannot be destroyed
- Implications:
Describe energy changes in prototypical car crash
- [09:00] Quantifying energy
- Kinetic energy: KE = 0.5 * Mass * (Velocity)^2
- Implications:
- Velocity affects energy much more than mass
- Quantify for car velocities
Deceleration Injuries
- [12:00] Bones / Joints
- Five major kinds of force: give examples
- Flexion
- Extension
- Rotation
- Distraction
- Compression
- [15:00] Organ damage
- Concept of "third collision":
- Impact against inside of body / skull
- "Cheesewire" by tendons in the way of
organs in motion, especially liver
- Classic deceleration damage to brain (concussion)
- "Paper bag" effect of full lungs on impact
RTA: Forms of Collision
- [19:00] Describe form of each, and typical injuries:
-
- Frontal
- Lateral (side)
- Rotational
- Rear
- Rollover
- [23:00] Pathways
- "Up and over":
- Classic injuries to head, chest, abdomen, pelvis
- Motorcyclists sustain bilateral femur fractures
- "Down and under":
- Classic injuries to knees, pelvis
- [25:00] Effects of restraints
- Diagonal + lap seatbelt:
- The most effective single measure
- NB: head is not restrained so spine
may be damaged by hyperflexion/extension
- Often causes bruising or burns in
high-speed impacts
- Lap seatbelt:
- Prone to cause abdominal damage if
incorrectly placed
- Passenger can go up-and-over
- Airbag:
- Very effective if used with full seatbelt
- Can be dangerous if no seatbelt fitted
- LETHAL to kids and to rear-facing baby seats
Conclusions
- [28:00]
- How to do it:
- Make use of your first 15 seconds
- Talk to patient and witnesses
- Apply basic laws of motion and energy
- Assume the worst until proven otherwise
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