DECOMPRESSION SICKNESS

DECOMPRESSION SICKNESS

Decompression sickness is the disorder that occurs when a person returns rapidly to normal surroundings (atmospheric pressure) from the area of high atmospheric pressure like deep sea. It is also known as dysbarism, compressed air sickness, caisson disease, bends or diver’s palsy.

CAUSE

High barometric pressure at deep sea leads to compression of gases in the body. Compression reduces

the volume of gases. Among the respiratory gases, oxygen is utilized by tissues. Carbon dioxide can be expired out. But, nitrogen, which is present in high concentration, i.e. 80% is an inert gas. So, it is neither utilized nor expired. When nitrogen is compressed by high atmospheric pressure in deep sea, it escapes from blood vessels and enters the organs. As it is fat soluble, it gets dissolved in the fat of the tissues and tissue fluids. It is very common in the brain tissues. As long as the person remains in deep sea, nitrogen

remains in solution and does not cause any problem. But, if the person ascends rapidly and returns to

atmospheric pressure, decompression sickness occurs. Due to sudden return to atmospheric pressure, the nitrogen is decompressed and escapes from the tissues at a faster rate. Being a gas, it forms bubbles while escaping rapidly. The bubbles travel through blood vessels and ducts. In many places, the bubbles obstruct the blood flow and produce air embolism, leading to decompression sickness.

Underground tunnel workers who use the caissons (pressurized chambers) also develop decompression

(caisson disease) sickness. Pressure in the chamber is increased to prevent the entry of water inside.

Decompression sickness also occurs in a person who ascends up rapidly from sea level in an airplane

without any precaution.

SYMPTOMS

Symptoms of decompression sickness are mainly due to the escape of nitrogen from tissues in the form of bubbles.

Symptoms are:

1. Severe pain in tissues, particularly the joints, produced by nitrogen bubbles in the myelin sheath of

sensory nerve fibers

2. Sensation of numbness, tingling or pricking (paresthesia) and itching

3. Temporary paralysis due to nitrogen bubbles in the myelin sheath of motor nerve fibers

4. Muscle cramps associated with severe pain

5. Occlusion of coronary arteries followed by coronary ischemia, caused by bubbles in the blood

6. Occlusion of blood vessels in brain and spinal cord also

7. Damage of tissues of brain and spinal cord because of obstruction of blood vessels by the bubbles

8. Dizziness, paralysis of muscle, shortness of breath and choking occur

9. Finally, fatigue, unconsciousness and death.

PREVENTION

Decompression sickness is prevented by proper precautionary measures. While returning to mean sea

level, the ascent should be very slow with short stay at regular intervals. Stepwise ascent allows nitrogen

to come back to the blood, without forming bubbles. It prevents the decompression sickness.

TREATMENT

If a person is affected by decompression sickness, first recompression should be done. It is done by keeping the person in a recompression chamber. Then, he is brought back to atmospheric pressure by reducing the pressure slowly.

Hyperbaric oxygen therapy may be useful.

SCUBA

SCUBA (selfcontained underwater breathing apparatus) is used by the deep sea divers and the underwater tunnel workers, to prevent the ill effects of increased barometric pressure in deep sea or tunnels. This instrument can be easily carried and it contains air cylinders, valve system and a mask. By

using this instrument, it is possible to breathe air or gas mixture without high pressure. Also, because of

the valve system, only the amount of air necessary during inspiration enters the mask and the expired air

is expelled out of the mask. Disadvantage of this instrument is that the person using this can remain in the sea or tunnel only for a short period. Especially, beyond the depth of 150 feet, the person can stay only for few minutes.

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