I learned a lot about lung diseases this semester. While most lung diseases/disorders are the result of smoking or an infection, there are some diseases/disorders that can happen to anyone, yet there are ways to prevent them.
An example is a pulmonary embolism (PE). In this condition, a piece of fatty plaque rips of a vein in a lower limb, travels through the circulatory system, until the blood carrying it returns to the lungs to become reoxygenated. At this time, the bulky plaque (or clot) gets stuck in the super small passages of the lungs. When it gets stuck, the surrounding lung tissue starts to die and rot, causing immense chest pain and shortness of breath. In rare cases, this blockage can cause heart failure and death.
A PE, as mentioned, breaks off from veins in the lower extremities. The tissue/plaque/fat that breaks off is called a deep venous thrombosis (DVT). There are also some situations in which the occurrence of a PE is high and thus extra caution must be taken: prolonged bed rest, long periods of sitting, and leg/foot/knee surgeries, are all situations that can provoke PE development.
Luckily, there are some preventable measures that can be taken to prevent the development (and subsequent breaking) of a thrombosis. For instance, the risk of PEs is reduced when patients do not take oral contraceptives (i.e. birth control, the extra synthetic estrogen can clot blog). Another way to prevent PE development is to keep the lower limbs moving! If you work at a desk, make sure to stand up and stretch or walk around at least once an hour. Same goes on long flights: stand up in your seat! If only for a minute; I'm sure the other passengers will be so occupied with the free peanuts (or Terra chips ;) ) they won't even notice you stretching your limbs. The goal is to keep the blood flowing such that thick, stagnant blood doesn't pool in the lower limbs, increasing the likelihood of pulling off venous plaques when the blood finally starts moving again.
Just as a note of clarification: the legs don't really drain blood really well due to the effects of gravity. In order for deoxygenated blood to be pumped back up to the heart, the legs have to move in order to actively push the blood upwards. This is why you need to stretch the legs on long flights and while sitting at a desk all day; you don't want that stagnant old blood pooling up for too long.