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Nitrogen embolization occurs in decompression sickness, which is also known as 'caisson disease'. It is seen in the persons whose occupation causes them to work at very high pressures and who may then be returned too quickly to normal atmospheric pressure (deep sea divers, tunnellers, etc.). 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, platelets often being associated with gas bubbles in the latter situation. 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.
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. [SUMMARY: Decompression sickness is a special form of air embolism caused by sudden change in atmospheric pressure as in deep-sea divers. Air breathed at high pressure (during a deep-sea drive) 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. ]
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