Deep Vein Thromboses (DVT)
Blood clots can form in the legs during ﬂights, chieﬂy because of prolonged immobility. This formation of clots is known as deep vein thrombosis (DVT), and the longer the ﬂight, the greater the risk. Although most blood clots are reabsorbed uneventfully, some might break oﬀ and travel through the blood vessels to the lungs, where they could cause life-threatening complications.
The chief symptom of DVT is swelling or pain of the foot, ankle or calf, usually but not always on just one side. When a blood clot travels to the lungs, it can cause chest pain and breathing diﬃculty. Travelers with any of these symptoms should immediately seek medical attention.
To prevent the development of DVT on long ﬂights you should walk about the cabin, perform isometric compressions of the leg muscles (i.e. contract the leg muscles while sitting), drink plenty of ﬂuids, and avoid alcohol.