MEDizzy - A 31-year-old man is on a scuba diving trip and descends to

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Hemodynamic Disorders

A 31-year-old man is on a scuba diving trip and descends to a depth of 50 m in the Blue Hole off the coast of Belize. After 30 minutes, he has a malfunction in his equipment and quickly returns to the boat on the surface. He develops difficulty breathing within 5 minutes, with dyspnea and substernal chest pain, followed by a severe headache and vertigo. An hour later, he develops severe, painful myalgias and arthralgias. These symptoms abate within 24 hours. Which of the following occluding his arterioles is the most likely cause of his findings?

ExplanationThese findings are characteristic of decompression sickness (the bends), a form of air embolism. At high pressures, such as occur during a deep scuba dive, nitrogen is dissolved in blood and tissues in large amounts. Ascending too quickly does not allow for slow release of the gas, and formation of small gas bubbles causes symptoms from occlusion of small arteries and arterioles. Fat globules in pulmonary arteries are a feature of fat embolism, which usually follows trauma. Fibrin thrombi may form with widespread activation of coagulation, as with DIC. Platelet thrombi may form with microangiopathic hemolytic anemia, such as thrombotic thrombocytopenic purpura.