How does COPD damage the lungs?1,2,3
A person who receives a diagnosis of chronic obstructive pulmonary disease (COPD for short) usually has symptoms of two different conditions: chronic bronchitis and emphysema. Those two conditions are now classified under the same name – COPD – because most people have symptoms of both, rather than just one or the other.
Some people with COPD may have more symptoms of one of the conditions than the other, but most people have a combination of symptoms. In the past, doctors used to diagnose each condition separately. For that reason, it is still common to hear people refer to them separately. This is especially true of people who are not health care professionals.
Most of the time, chronic bronchitis and emphysema are a product of lung damage that results from long-term exposure to airborne irritants and toxins. Cigarette smoke is the most common cause of lung damage in COPD. However, air pollution or toxic chemicals and fumes in the workplace can also put people at risk for COPD.
In both kinds of COPD, the lung damage makes breathing tough and can cause a person to have a number of disabling symptoms and harmful complications. This is because the lung damage causes obstructions, or blockages, to the standard flow of air in and out of the lungs.
These airflow obstructions occur in different parts of what is called the pulmonary system. In this system, the lungs deliver oxygen to the body through the process of inhalation. They also expel carbon dioxide, a waste product, from the body through exhalation. For people with COPD, lung damage makes them unable to breathe well and prevents the system from working in a healthy way.
For a more detailed description of how healthy lungs function, please see “How healthy lungs function”.
What is chronic bronchitis?1,4
Chronic bronchitis involves an ongoing, long-term irritation in the parts of the lung called breathing tubes. Breathing tubes include both the two main airways (called bronchi) that lead to each lung, as well as the smaller tubes (called bronchioles) that branch off from these main airways. The irritation in the breathing tubes causes two serious problems:
- Swelling in the lining of the bronchial tubes
- Excessive mucus (often called phlegm) production
Chronic bronchitis prevents a healthy flow of air through the airways because the inflammation and excess mucus combine to narrow the breathing tubes. This can greatly restrict the amount of air that can pass through the airways and into the air sacs in the lungs, where oxygen is absorbed.
Because of this persistent irritation, there is a need to clear mucus from the airways so that air can flow more freely. As a result, people with chronic bronchitis have a long-term cough that produces mucus. They may also experience wheezing, chest pain, and a feeling of breathlessness.
Chronic bronchitis is a serious condition. It is different from acute bronchitis, which is usually caused by a contagious virus or bacteria. In the acute form of this illness, the symptoms such as cough and fever disappear completely within a week or so, after the body fights off the virus.
On the other hand, chronic bronchitis is a long-term condition that can last for months or years. Also, keep in mind that it is caused by irritants rather than a virus or bacteria. People who smoke are at a high risk of developing chronic bronchitis, but it can also be caused by exposure to pollution and other toxins.
It’s important to recognize, though, that because COPD irritates the breathing tubes, they are less able to fight off infections as healthy lungs can. So, people with chronic bronchitis are also more likely to develop viral or bacterial infections that make their symptoms even worse.
What is emphysema?1,3,5
Emphysema is a condition that affects the millions of tiny air sacs, called alveoli, which are found within the lungs. The function of the alveoli is to transfer oxygen into the blood and carbon dioxide out of the blood. Healthy air sacs have flexible, elastic walls that require energy (mainly from the diaphragm) to expand and inflate with air. But they require no energy to deflate and push out the air, because their flexibility allows them to easily bounce back to their original smaller size.
People with emphysema have damaged lungs from long-term exposure to irritants. As with chronic bronchitis, smokers have the highest risk of developing emphysema. The lung damage from emphysema takes two forms, both of which are common in most patients:
- Air sac walls lose their natural elasticity and flexibility
- Walls between air sacs are destroyed completely
The result of the first kind of damage is that without their natural flexibility, the air sacs are no longer able to deflate like a balloon and expel the air without effort. This means that in addition to using energy to inhale air into the lungs, people with emphysema must also use energy to exhale air from the lungs. Because this requires twice as much effort as normal breathing, as well as the use of extra muscles that are not as efficient, people with emphysema often feel out of breath during normal activities.
The second type of damage causes the tiny air sacs to combine into a smaller number of much larger sacs. There are no longer as many air sac walls to exchange oxygen and carbon dioxide in the blood. The result is that with each breath, there is a smaller amount of oxygen that gets into the bloodstream. There is also a smaller amount of carbon dioxide that leaves the blood and the lungs.
Another problem is that because the air sacs are now bigger, they are not as easy to empty completely. The “used” air becomes trapped inside instead of being exhaled. That, in turn, prevents enough “fresh” air from entering the air sacs. Because they have too much extra air in their lungs, this kind of damage is another reason that people with emphysema can feel constantly out of breath.