A pulmonary embolism is any blockage of the pulmonary artery that blocks the flow of blood to the lungs. The blockage is usually the result of a clot that has either developed in the artery or has broken off from a vein elsewhere in the body, but it can also be the result of an air, fat or plaque embolism. When blood flow to the lungs is blocked, it cannot be properly oxygenated and the body begins to be starved of oxygen. An increase in heart rate has no effect on the condition as the limiting factor is blood flow to the lungs. As a result, despite a strong heart beat, the oxygen level in the blood starts to drop.
A pulmonary embolism is a life threatening condition and requires immediate medical treatment. Once the condition is diagnosed, usually with an angiogram or CT scan, the patient is given an anti-cogulant such as heparin to keep the condition from getting worse. At that time, the patient is monitored to see if their vital signs start to improve. If not, drugs that actively break up clots are used. If that does not improve the patient, surgery is scheduled to physically remove the blockage.