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NEWS
16th May 2007

Hypoxia and Medicine

Hypoxia, or lack of oxygen, is a very common phenomenon in medicine. Sudden and severe hypoxia such as drowning is obvious and frequently fatal. The majority of hypoxia which we experience in medicine, however, tends to be of slower onset. But if hypoxia is left untreated it can result in the same unfortunate outcome. As doctors it is our job to try to stop and reverse hypoxia in order to ensure adequate oxygen levels in our patients.

As explained above ('What is Hypoxia?') oxygen must be transported from the air to each of the millions of cells within our body. Failure anywhere along this transport chain leads to hypoxia. The vital components of the transport process are the lungs, heart, circulatory system (arteries and veins) and the red blood cells which travel within them. If any of the individual components are affected by disease, hypoxia will ensue.

Probably the commonest cause of hypoxia we see in hospitals is due to disease of the lungs. Smoking damages the lungs over many years whereas an infection (pneumonia) can cause sudden deterioration. With defective lungs not enough oxygen will be drawn into the body for the blood to circulate. Without treatment hypoxia may become progressively worse causing debilitation and even death. Our first line of treatment for these individuals is to administer oxygen to them, usually via a mask in hospital. By increasing the amount of oxygen available to the patient we hope to increase the amount which is delivered to their tissues. Sometimes, however, this proves ineffective and more drastic measures must be taken. One such measure is to breathe for the patient using a mechanical ventilator. In this way we are able to inflate and deflate the patient's lungs with as much oxygen as we wish until such time that they recover from their underlying disease. Artificial ventilation is a complicated process and can only be carried out by specially trained individuals on an intensive care unit.

Heart disease can also lead to hypoxia and probably the most dramatic example of this is children born with heart defects. In these children the heart, because of a structural defect, is unable to pump blood effectively around the body. There may also be mixing of oxygenated blood from the lungs with deoxygenated blood from the body which compounds the problem. Although oxygen may improve the situation temporarily, these children will eventually need surgery to correct the abnormality.

Many patients have long term disease which requires them to have oxygen at home. The need for a large cylinder of oxygen in their home makes for a reasonably restricted lifestyle as they frequently cannot leave home with such a burden. One of the Caudwell Xtreme Everest projects is looking into ways of delivering oxygen more efficeintly to these patients using a novel re-breathing circuit.

So hypoxia can affect people in many ways. Extra oxygen may help ease the problem temporarily but more often than not the underlying disease needs to be effectively treated before the hypoxia subsides.



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