Choking

If the patient is unconscious seek expert help swiftly

US President George W Bush fainted for a few seconds and fell off a couch after choking on a pretzel. BBC News Online examines how.

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Everybody knows the phrase "something went down the wrong way".

This means that instead of swallowing food down the food pipe, or oesophagus, it is diverted down the windpipe, or trachea.

Heimlich manoeuvre

The victim should be sitting or standing

Grasp the victim from behind with your hands around his waist

Make a fist with one hand and place the thumb side on the victim's abdomen, midway between the waist and the rib cage

Grasp the fist with your other hand and thrust forcefully inward and upward

Each new thrust should be a separate and distinct movement

This can block off the supply of air to the lungs, and cause the involuntary coughing and gasping for air that we call choking.

Fainting will occur if the obstruction leads to a reduced supply of oxygen to the brain. In this case it is vital to remove the obstruction as soon as possible.

If the obstruction is quickly removed, then no lasting damage will be done, but if the brain is starved of oxygen for more than a few seconds, it can lead to serious injury.

Permanent brain damage can result in about two minutes and death in three minutes.

Choking on food often occurs after drinking alcohol, which dulls feeling in the throat.

Frequently, a choking victim clutches the throat with thumb and forefinger, a universal signal of distress.

Children choke more frequently than adults, usually on a toy or food fragment.

Infections such as croup or epiglottitis can produce extreme swelling that blocks the airway.

If a child with a fever, a barking cough, or known infection develops an obstructed airway, it is important to seek hospital treatment as quickly as possible.

Unusual case

The case of President Bush is unusual in that it does not appear to simply involve a blocked airway.

According to White House physician Dr Richard Tubb, he fainted because the pretzel he ate stimulated a nerve in his throat.

This was almost certainly a reference to the vagus nerve - a major connection between the brain and various organs, such as the gut, liver and heart, which passes through the neck.

Stimulation of the vagus nerve can cause the heart rate to slow down. In someone like President Bush, who has a lower than normal heart rate anyway, fainting could result.

What to do

UK choking statistics

About 16,000 cases of choking are treated in UK hospitals each year

In 1999, a total of 218 people choked to death on food. A further 55 died after choking on non-edible objects

About half the choking fatalities in 1999 were men and women aged 75 and over

About 2,600 choking accidents in the UK each year involve children under four years of age

If the victim can talk this is a sign that the airway is not completely obstructed and that some air is getting through to the lungs.

In this case it is best to leave the victim alone until they can dislodge the food or object themselves by coughing or throat clearing, or with their fingers.

If they cannot talk this probably means the airway is completely obstructed.

It is essential to seek urgent medical help, but in the meantime one should try to dislodge the obstruction using a technique called the Heimlich manoeuvre (see box).

Unconscious victim

If the victim has lost consciousness and you cannot see the chest rise and fall, then it is vital to take action immediately.

Kneel next to or astride the victim, place the heel of one hand on the abdomen midway between the waist and the rib cage.

Place the other hand on top of the first and thrust inward and upward.

If the victim is pregnant or obese, then substitute chest thrusts for abdominal thrusts.

Use the same hand position over the breastbone that you would for chest compressions, but do quick downward thrusts.

Sweep the mouth of the victim if abdominal or chest thrusts do not dislodge the obstruction.

Open the victim's mouth wide by grasping the chin.

Still holding the chin, bend the forefinger of the other hand and with your hooked finger probe deep into the mouth along the insides of the cheeks.

If the airway is still not open, back blows, abdominal (or chest) thrusts, finger sweeps, and rescue breathing should be repeated rapidly as many times as is necessary to remove the obstruction.

Occasionally, an open handed blow to the back may dislodge the obstruction and can be tried at this time.

The longer the victim goes without oxygen, the more relaxed the muscles become, and this may release the foreign object.