Pulmonary Embolism Support Group
By far the most common form of pulmonary embolism is a thromboembolism, which occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death.
They said its more common than you'd think, not just aeroplane trips but coach trips, fishermen that sit in the same position, theatre goers, people that are drunk that fall asleep in awkward positions. In fact anywhere that you restrict blood flow for 4 hours is a problem. Who knew sitting could be so risky!