A blood embolism occurs when a blood clot that has formed on the wall of a blood vessel detaches and travels through the circulatory system. A pulmonary embolism means the clot has blocked off the main artery to the lungs or one of its major branches. It is estimated that 80 per cent of cases are linked to deep vein thrombosis. Around one third of people who experience a major pulmonary embolism will die. Life saving treatment includes thrombolytic and anticoagulation drugs that dissolve the clot and restore blood flow.