Smoke inhalation

Many people suffered from smoke inhalation following forest fires in the US

Inhaling hot smoke can have a devastating effect on the delicate tissues of the respiratory system.

About 4% of burn victims die from their injuries - and in many of these cases the crucial factor is smoke inhalation.

The full extent of the damage may only become apparent days after the incident itself.

There are three major problems associated with smoke inhalation:

• heat damage
• asphyxiation
• irritation of the lung tissues

Heat damage is usually limited to the tissues of the mouth and upper throat.

Fortunately, smoke cools rapidly once it is inhaled. Animal experiments have shown that if air at 142C is inhaled it has cooled down to 38C by the time it has reached the chest.

Heat damage can destroy the cells that line the mouth and throat. Often this leads to the build up of fluids, which can obstruct the airways and make breathing difficult.

This problem usually becomes apparent within six to 24 hours of inhaling smoke.

Serious smoke inhalation can lead to damage to the smaller airways deeper down in the respiratory system.

These airways may become blocked by damaged material.

The minute hairs, or cilia, that line these airways and help to ferry contaminants out the respiratory system may also be damaged.

In this case, the patient may find breathing more and more difficult. There is also a risk of developing pneumonia, or even complete respiratory failure.

Asphyxiation occurs when the body fails to get sufficient supplies of oxygen to the tissues.

Inhaling smoke blocks the intake of oxygen, and boosts levels of carbon monoxide.

Irritation

As well as direct tissue damage, smoke inhalation may provoke dangerous chemical reactions within the body.

Pollutants contained in smoke can trigger the immune system to go into overdrive, resulting in damage to the tissues.

The immune system produces chemicals called cytokines which seek out and helps neutralise inhaled contaminants.

Too much of a specific cytokine called tumour necrosis factor-alpha (TNF) can stimulate a chain reaction that leads to the death of cells and general irritation in the lung.