The Lungs

Unlike pulmonary barotrauma, pulmonary DI is an intravascular occlusive bubble disease. It results from the passage of venous gas emboli through pulmonary capillaries. The peri-alveolar network of capillaries serves as a trap for venous gas emboli. However, if the amount of gas is excessive, it may cause cardiac air locking and pulmonary outflow obstruction or microvascular obstruction with vasoconstriction, endothelial damage, inflammation, capillary leak and pulmonary edema - "the chokes". The pulmonary "bubble trap" may also be overcome by massive embolization or be bypassed via broncho-pulmonary shunts, arterio-venous fistulae, or intra-cardiac shunts. A reduction in the diameter of circulating bubbles - such as by repetitive diving or "yoyo" diving - may allow bubble passage through the pulmonary capillary beds. All of these mechanisms may lead to arterialization of bubbles - so-called paradoxical gas embolism. The latter provides an attractive theoretical explanation for the poorly understood associations between "chokes", patent foramen ovale, and DI of the central nervous system and skin u'43.

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