What is it: decompression sickness, also called the bends, is related to great changes in environmental pressure. It is caused by nitrogen bubbles forming in the bloodstream and tissues of the body. The bubbles occur if you move from deep water towards the surface (where the surrounding pressure is lower) too quickly . It is most usually associated with divers, but can also occur in fliers in a non pressurised cabin when there is a major change in altitude. In the most serious cases decompression sickness can lead to unconsciousness or death.

What are the symptoms: the symptoms generally appear in a relatively short period after completing the dive. Almost 50 per cent of divers develop symptoms within the first hour after the dive, 90 per cent within six hours and 98 per cent within the first 24 hours. In practice this means symptoms that appear more than 24 hours after the dive are probably not decompression sickness. An exception is if the diver has travelled in an aircraft or has been travelling in the mountains. Under these circumstances, low pressure can still trigger decompression sickness more than 24 hours after the last dive. As a result, it is wise not to fly within 24 hours of a deep dive. Mild forms of decompression sickness can resolve themselves without treatment or by breathing 100 per cent oxygen at the site of the accident. The symptoms of decompression sickness vary because the nitrogen bubbles can form in different parts of the body. These can include pain in the joints “bends”. a headache or vertigo, unusual tiredness or fatigue, confusion, a rash, shortness of breath, tingling in the arms or legs, muscular weakness or paralysis, a burning chest pain with a deep breath, a cough or ear or sinus pain.

What happens if I get it: if you suspect decompression sickness, stop the dive, initiate first aid, and summon assistance from a specialist in divers' medicine. Treatment is oxygen on site and during transportation, followed by treatment in a decompression chamber.

How can I avoid decompression sickness?

· Dive within the limits set out in the diving tables.

· Keep your rate of ascent to a maximum 10m/min.

· Don't plan any dives that need a decompression stop in the water.

· Make a three-minute safety stop at a depth of 5m.

· Don't dive more than three times in one day.

· If you plan more than one dive in one day, start by making the deepest dive first.

· If you are diving for several days in a row, have a dive-free day after two to three days.

· Don't do any hard work before or after diving.

· Drink lots of liquid before diving. Lack of fluid due to heat or excess alcohol is dangerous.

· Make sure you are in good physical condition and well rested. Have regular medical checkups.

· Make sure there is an interval of at least 24 hours between diving and travel by air or climbing up mountains. If you have had decompression treatment, the recommended interval before the next dive is at least 48 hours.