An embolism is the obstruction of blood vessels by a mass or clot that has detached from its origin and traveled through the bloodstream. Embolisms can be classified based on the material causing the obstruction and the source and direction of blood flow. Common types of embolisms include pulmonary, fat, air, amniotic fluid, and tumor embolisms. Pulmonary embolisms originate in the lower leg veins and are caused by stasis, hypercoagulability, or a saddle embolism. Fat embolisms result from trauma or medical conditions and obstruct arterioles and capillaries. Decompression sickness is a form of gas embolism that affects scuba divers or caisson workers