pulmonary embolism - caused by emboli that travel through the blood stream to the lungs and block a pulmonary artery. When this occurs, circulation and oxygenation of blood is compromised. The emboli are usually formed from blood clots but are occasionally comprised of air, fat, or tumor tissue. Risk factors include: prolonged bed rest, surgery, childbirth, heart attack, stroke, congestive heart failure, cancer, obesity, a broken hip or leg, oral contraceptives, sickle cell anemia, congenital coagulation disorders, chest trauma, certain congenital heart defects, and old age. Symptoms include: labored breathing, sometimes accompanied by chest pain, a rapid pulse, a cough that produces bloody sputum, a low fever, fluid build-up in the lungs.