Alveoli are tiny sacks that are found along the millions of capillaries in your lungs. As your heart beats, old, used, deoxygenated blood pumps through the right ventricle, through the pulmonary artery into the lungs, and into the capillaries. When you inhale, the alveoli inflate with air, and the oxygen/carbon dioxide exchange is made through the walls of the alveoli, enriching the blood in the capillaries with oxygen.
This is how your blood is oxygenated. It's a pretty slick system, really. Almost seems... engineered.
Emphysema is the deterioration of elastin in alveoli walls in the lungs. Over time the alveoli become less and less flexible. As an analogy, imagine inflating a balloon, and then watching the air escape from it. Over time the balloon changes to a paper sack, and finally a glass bottle. After the alveoli become truly fucked, the walls essentially stop working. You lose surface area in your lungs. The air that is in the rigid alveoli is no longer useful to you. So not only is it hard as hell to breathe, you are only using a percentage of the air you have. And every day that percentage drops.
After a while, exhaling becomes extremely difficult, since your glass alveoli are always inflated, you are basically constantly trying to exhale, but your lungs won't empty themselves. Your blood pressure skyrockets, as your poor heart begs for more oxygen from your lungs, pumping more and more blood harder and harder to compensate. In addition, your blood thickens because of the lack of oxygen, thus making your blood even more difficult to pump.
In a somewhat cruel twist of irony, after years of this condition, your body becomes conditioned to the low levels of oxygen. The brain learns to respond to high levels of carbon dioxide instead. As a result, increasing the level of oxygen in the blood through oxygen treatment can be lethal. Oxygen, the thing your body is craving, cannot be supplied in full to your body, because your body is so used to the lack of oxygen.
Essentially, Emphysema is slow suffocation, suffocation over the course of years. Today you breathe less than you could breathe yesterday. And tomorrow you will breathe even less. And there's shit you can do about it.
Causes? Well, basically smoking. Though there are some cases where it occurs because of some genetic chemical imbalance, smoking is basically the cause. Well, not necessarily the act of smoking, but smoke itself is the cause. My point is you can give emphysema to someone else, by exposing them to your second-hand smoke over the course of years.
My grandfather stopped smoking before I was even born.
When I was five, emphysema meant that my grandfather had to take a break in the middle of mowing the yard, to catch his breath.
When I was ten, it meant it took him two days to mow his yard, and he could no longer wrestle with me.
When I was 15, it meant he couldn't use the stairs in his basement, and he couldn't walk for more than 50 or 60 yards at a time.
When I was 20 it meant he had to stop for a breather twice on the way to his mailbox. A 15 yard journey he could only tolerate two or three times a week.
Now I'm 25 and emphysema means a lot more. Emphysema is a ghastly mask on his face, spewing medicine into his glass lungs in a hospital room. Emphysema is a signed power of attorney on his bedside, which nobody wants to read. Emphysema is a complete lack of promises. Emphysema is a million stories I've heard a million times and hope to God I'll hear again.
Emphysema is Christmas in a hospital room.
This has been a very educational weekend.