Pulmonary embolism occurs when an artery to the lungs is blocked. Generally, the blockage is caused by one or more blood clots that travel to your lungs from another part of your body.
In most cases, pulmonary embolisms are tiny and are not life-threatening. But even small pulmonary embolisms are a main cause of hospital mortality and an increasing threat to passengers on prolonged airplane flights.
In most circumstances that increase the risk of forming a blood clot, preventative measures can be quite effective in avoiding a pulmonary embolism