The blood returning to your heart from the lower extremities of the body has gravity to contend with and, therefore, it is harder for the blood to be pumped round the body. In order to help the blood flow, the muscles of the legs act as a pump - this occurs naturally as you walk around.

Long periods of inactivity, combined with the cramped conditions and dehydration which can occur on flights can cause a number of circulatory problems. Blood is at risk of not circulating through your veins adequately and concentrating in your legs causing problems ranging from swollen ankles and tired, aching legs to more serious conditions such as DVT.

Flying contributes many of the factors which may be associated with the development of a DVT:

• Cramped conditions
• Limited exercise opportunity and lack of leg movement
• Low humidity
• Reduced cabin pressure
• Dehydration
• Increased carbon dioxide and reduced oxygen levels

The signs and symptoms of a DVT can develop after your journey and so you should contact your doctor immediately if you develop any of the following and have recently been on a long haul flight or a long journey:

• Severe or persistent swelling of the ankles
• A swollen or painful calf or thigh
• An increase in skin temperature
• Local skin discolouration