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Deadly Deep Sea Diving -

Pathology of Decompression Sickness ('Caisson disease')

Dr Sampurna Roy MD


"As every scuba diver knows, panic is your worst enemy: when it hits, your mind starts to thrash and you are likely to do something really stupid and self-destructive." - Daniel Dennett


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Diving with self-contained underwater breathing apparatus (scuba) has become a popular recreational sports activity throughout the world.

Although scuba diving is not a competitive sport requiring athletic health conditions, a certain medical fitness is recommended because of the physical peculiarities of the underwater environment.

Decompression sickness is a special form of air embolism caused by sudden change in atmospheric pressure seen in deep-sea divers.

'Caisson disease' is a chronic form of decompression disease due to persistent gas bubbles in the normally poorly vascularized portion of the skeleton (head of the femur, tibia and humerus) causing multiple foci of ischemic necrosis.

Air breathed at high pressure (during a deep-sea dive) causes increasing amount of gas (particularly nitrogen) to be dissolved in blood and tissues.

Subsequent rapid depressurization allows the dissolved gases to expand and bubble out of solution to form gas emboli. 

Nitrogen embolization occurs in decompression sickness ( 'caisson disease') .

This condition is often seen in the persons whose occupation causes them to work at very high pressures and who may then return too quickly to normal atmospheric pressure 

(Example: Commercial or professional deep sea divers and tunnellers ).

At high pressure, inert gases, of which nitrogen is the most important, are dissolved in the plasma and in interstitial tissue,  especially adipose tissue.

If the person at risk return too quickly to normal atmospheric pressure, the gas comes out of solution and small bubbles  are formed within the interstitial tissues and blood. In the blood, platelets are often associated with gas bubbles.

These bubbles may coalesce to form quite large masses and the clinical features are produced either by emboli in the circulating blood or by the presence of bubbles in the interstitial tissues, especially in tendons, joints and ligaments.

When this happens the patient complains of excruciating pain ( the syndrome being known as "the bends" ).

Gas emboli may also cause focal ischemia in a number of tissues, including brain and heart.

In lungs, edema, hemorrhage and focal emphysema lead to respiratory distress, the so-called chokes.

Occasionally the presence of nitrogen emboli in the systemic circulation is followed by the ischemic damage to the ends of long bones, this being associated with secondary damage to the articular cartilage and joints.


The symptoms may be relieved by placing the patient in a compression chamber and forcing the gases back into solution.

Once this has been done, slow and careful decompression should avoid a recurrence.

A prerequisite for those who enjoy scuba diving is mental and physical fitness. The person should be examined for fitness before first taking up the sport, and should be rechecked every one to three years.

For the deep sea diver not only lung function and electrocardiogram (ECG) should be normal, the psychological profile of the diver also plays an important role under water.


Further reading:

Is there a need for more diving science for divers?

Fatal Scuba diving accidents. A discussion of 8 fatal cases.

Serum albumin as a biomarker of capillary leak in scuba divers with neurological decompression sickness.

Saturation diving; physiology and pathophysiology.

Serum albumin as a biomarker of capillary leak in scuba divers with neurological decompression sickness.

Acute decompression sickness--report of an autopsy case.

Postmortem CT appearance of gas collections in fatal diving accidents.

A forensic diving medicine examination of a highly publicised scuba diving fatality.

Case report: fatal diving-accident. Or: accident while diving?.


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Dr  Sampurna Roy  MD

Consultant Histopathologist (Kolkata - India)







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