Pulmonary embolism. Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathing in, and coughing up blood. Symptoms of a blood clot in the leg may also be present, such as a red, warm, swollen, and painful leg. Signs of a PE include low blood oxygen levels, rapid breathing, rapid heart rate, and sometimes a mild fever. Severe cases can lead to passing out, abnormally low blood pressure, obstructive shock, and sudden death. PE usually results from a blood clot in the leg that travels to the lung. The risk of blood clots is increased by advanced age, cancer, prolonged bed rest and immobilization, smoking, stroke, long-haul travel over 4 hours, certain genetic conditions, estrogen-based medication, pregnancy, obesity, trauma or bone fracture, and after some types of surgery. A small proportion of cases...