What happens in COPD, exactly?

What is it?

COPD is a lung disease that impairs the normal flow of air for a long period of time. The typical symptoms include cough and shortness of breath. COPD worsens over time, and as the disease progresses, normal things like walking up stairs can become near impossible.

COPD is extremely common; it affects about 5% of the population of the world. In 2013 it resulted in 2.9 million deaths.

What causes it?

Smoking is the most important cause of COPD. About half of lifetime smokers will develop the disease. In some countries also other things that expose you to certain particles, like indoor fires, are a significant factor. You usually need to be exposed to these things for decades before the symptoms of COPD begin to appear.

What happens during it?

The symptoms of COPD are mainly caused by how cigarette smoke harms our lungs, and our body’s reaction to being irritated by it.

Our airways produce mucus. One of it’s main purposes is to catch any microbes that come into our body when we breathe, and then transport them into our stomach for destruction. This is easier higher up in our airways when only gravity is enough to get the mucus down to our stomach, but things get trickier in the lungs when we need to get the mucus to first go up to the throat. This is why the cells lining our airways have extensions called cilia on their surfaces. The cilia move in such a way that they transport the mucus up the lungs to the throat. Cigarette smoke harms these cilia, and this can lead to mucus staying in our lungs. Our body doesn’t like this – it irritates the cells, and mucus is also the ideal breeding ground for bacteria if it stays in the same place for too long. We try to get rid of the mucus in any way we can, and this causes the cough associated with COPD.

The smallest units of our airways are microscopical, grape-looking alveoli. This is where gas exchange takes place: the walls are so thin that oxygen and carbon dioxide can easily get trough to the tiny blood vessels running on the other side of the wall. You might have heard that exhalation happens when the diaphragm relaxes and causes the pressure in the chest cavity to rise, but in fact, our airways including our alveoli also play a role. They are elastic, and you can think of them in terms of what happens when you stretch an elastic rubber band and then let it go – it springs back. When inhalation has stretched our elastic airways, they spring back during exhalation.

Cigarette smoke destroys the walls of our smallest airways and because of this it leads to the loss of the elasticity of lungs. We can’t breathe out properly – there’s always some amount of air left in our lungs. We still need oxygen though, so we will breathe in normally even though there already is some air in our lungs, and this can force the lungs to increase their total volume. Having to breathe in more air than the lungs would allow feels uncomfortable, and the shortness of breath in COPD is linked to the air that’s trapped inside our lungs but isn’t able to provide us with oxygen anymore.

How can it be treated? 

I guess that the take-home message of this post is that you shouldn’t smoke. COPD isn’t fun (and neither is lung cancer) and you don’t want to go through that. Seriously.

There isn’t a cure for COPD, but the symptoms can be managed to some extent. Being regularly vaccinated reduces the risk of infections, stopping smoking cuts the risk of dying by 18%, and avoiding air pollution is also a good idea. In advanced cases the aim is to reduce the pain and uncomfort – morphine can help with feeling  short of breath and mechanical ventilation can be useful.




Sources: https://en.wikipedia.org/wiki/Chronic_obstructive_pulmonary_disease, https://en.wikipedia.org/wiki/Pulmonary_alveolus, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2713323/


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