Chronic Obstructive Pulmonary Disease (COPD) is almost always caused by cigarette smoking (also by some occupational fumes and dusts). There are 2 forms: Chronic Bronchitis and Emphysema; most patients have a mixture of both. Chronic Bronchitis can be present continually, but can also get worse from time to time with acute exacerbations that then get better. See Diagram — Lower Respiratory System.
“Obstructive” disease means useless air gets trapped in the airways. So new air with oxygen (O2) can’t get in, & the carbon dioxide (CO2) we need to exhale can’t get out. Not enough O2 damages the heart & the entire body. Too much CO2 dulls the brain. If O2 is critically low, you get anxious & crazy. If CO2 is critically high, you fall asleep & stop breathing (& die, etc.).
Symptoms of Chronic Bronchitis are a lot like asthma, with bronchospasm that causes wheezing. There’s a cough, and usually some shortness of breath. With a stethoscope, we can hear wheezes and rhonchi (squeaks & gurgles). See Asthma for a fuller description.
But while asthma gets triggered by substances in the air, the bronchospasm of Chronic Bronchitis is due to constant presence of mucus and bacteria in the bronchi. This is because the cilia, tiny hairs that constantly brush gunk up and out of our lungs, get paralyzed by as little as one cigarette per week (good reason not to smoke). Bronchospasm can persist even after quitting, but will be much less.
Usually we treat Chronic Bronchitis similarly to asthma. The same medications work for both, though some are better for one, others for the other. But if bacteria in the bronchi grow too much, it’ll trigger an exacerbation of Chronic Bronchitis (there aren’t any in asthma). So if a smoker’s phlegm starts turning green, & wheezing gets worse, antibiotics help somewhat.
Emphysema involves destruction of the alveoli (usually from smoking). With pure emphysema, there’s no cough and no phlegm, just shortness of breath (it’s in the alveoli that oxygen moves from the lungs to the blood). Damage develops so gradually that patients often don’t realize it, until shortness of breath interferes with a key life activity like work, play, or sex.
There’s no treatment for Emphysema, though stopping smoking will prevent further damage. We can see how much damage has occurred by ordering pulmonary function tests (PFT’s). If the condition is bad enough, wearing oxygen during sleep will protect the heart. When emphysema reaches a critical point, patients can’t breathe without a respirator; death is on the horizon. Unfortunately, studies have shown that showing smokers their PFT results doesn’t motivate them to quit.