Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has traveled from elsewhere in the body through the bloodstream (embolism). Symptoms 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 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, and sudden death.