Body Story

Crash: Trauma

• What happens when a car crashes?
Car crashes are a very common cause of traumatic injury — that is, damage to the body produced by external violence and involving wounds. When a car hits a stationary object there are two collisions. The first occurs between the car and the object. The second occurs between the driver and part of the car: for example, the steering column, the windscreen, the dashboard or, hopefully, the seatbelt and airbag.

For example, when a car travelling at 55mph (88kph) hits a stationary object, the frame of the car stops moving within 0.2 seconds. However, whatever is inside the car, including the driver and passengers, continue to move at 88kph for another 0.3 seconds.

Crucial factors in determining the extent of injuries include the speed of the impact and whether or not the driver and passengers are wearing seatbelts. If they are wearing seatbelts, their chances of sustaining only minor injuries are much higher.

Few will escape without some cuts and bruises. Given that your body continues to travel at the speed at which the car was travelling, you are likely to come into contact with some glass and steel. Airbags and seatbelts prevent this contact from being too serious.

Whiplash is the most common injury sustained in car accidents. On impact the head may be thrown back so violently that nerves, joints and muscles can be damaged, leading to back and neck pain, dizziness and headaches.

Broken bones are also common. Instinct causes the driver and any passengers to stiffen their legs upon impact, which increases the likelihood of breaks.

But internal injuries are the most serious. On impact, your internal organs shift violently. In serious cases this can lead to torn blood vessels and internal bleeding. If the brain shifts violently it slams against the skull, and complex connections and delicate cells may be damaged.

In Body Story, David and Laura were both wearing seatbelts when their car crashed, but such is the force of the impact that both sustain serious injuries.

• Laura's case: ruptured blood vessel
On impact, the body's internal organs move violently, stretching the blood vessels. In Laura's case, a blood vessel leading to the spleen ruptures.

In itself, this is not a serious problem: as blood escapes from the blood vessel, it starts to congeal and seals the tear. So long as no further pressure is put on the wound, it will heal itself. However, if the wound is not given sufficient time to heal itself, it is liable to re-open, and a serious problem may develop. If the blood vessel continues to be strained through sudden movements, blood will continue to flow out into the protective membrane that encases the spleen. Gradually, this sac will fill with blood. But all the patient feels is a dull ache.

Days after the accident a slight shock to Laura's abdomen is enough to burst the swollen membrane, and as it bursts, it tears away part of her spleen. Around a third of the blood in Laura's blood supply pours out into her belly. The brain is suddenly starved of blood, so the heart beats faster to increase the flow. All it succeeds in doing, however, is pumping more blood out of her severely damaged spleen.

• David's case: haematoma
The brain may also be shifted violently in an impact but, encased by the skull, it cannot move freely. When the car crashes, David's brain slams against his skull. This severs connections between his brain stem and his conscious brain and causes an artery in his brain to rupture. The internal bleeding in David's case is more acute than in Laura's: the blood is flowing so quickly from the artery that it doesn't congeal at the point of damage and seal the wound.

The danger with a haematoma — a swelling composed of blood - is that if it is large enough, it can compress or shift the brain, damaging sensitive structures in the brain stem. It can also raise the pressure inside the skull, which could shut off the blood supply to the brain. In David's case, the problem is that the haematoma will crush the area of the brain that controls the breathing and the heartbeat.

As successive parts of the brain come under threat, the brain acts to protect itself. The patient loses consciousness and goes into a coma.

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