What is the pathophysiology of COPD?
According to the American Lung Association, it is the third leading cause of death in the United States. COPD typically causes coughing that may produce large amounts of mucus, shortness of breath, and other symptoms.
What happens in the lungs?
In healthy lungs, once a person breathes in air, it travels down their wind pipe and into airways that are found in the lungs, known as bronchial tubes. Inside of the lungs, the bronchial tubes branch into thousands of small, thinner tubes called bronchioles.
People with COPD have less air flowing in and out of their airways than people with healthy lungs.
At the end of these tubes are bunches of tiny round air sacs called alveoli. There are more than 300 million alveoli in the lungs. The larger the lungs, the more alveoli there are.
Capillaries are small blood vessels that surround the walls of the air sacs. Once air makes its way to the air sacs, oxygen passes through the air sac walls into the blood in the capillaries.
Carbon dioxide also moves from the capillaries into the air sacs. These events happen at the same time and are referred to as gas exchange.
Healthy air sacs are elastic and very stretchy. As a person breathes in, the air sacs fill up with air like a balloon. As they breathe out, the air sacs deflate due to the air moving out. The body uses energy to blow the air sacs up but no energy is used to empty them as they return to their original size.
People with COPD have less air flowing in and out of their airways, which can be linked to several possible reasons:
- The airways and air sacs have lost their stretchiness
- The walls between the air sacs are damaged or have been destroyed
- The walls of the airways become inflamed and thickened
- More mucus is produced in the airways, causing them to clog
Chronic bronchitis and emphysema
Chronic bronchitis is the result of an increase in swelling and mucus production in the breathing tubes or airways. The lining of the airways remains irritated and inflamed. The additional swelling and mucus leads to a reduction of the inside of the breathing tubes, causing them to be smaller than normal. This makes it more difficult to breathe.
Emphysema causes damage to the air sacs in the lungs. The walls between many of the air sacs are damaged, causing them to lose their shape. This causes the sacs to lose their stretchiness and trap air instead.
It becomes increasingly difficult to push all of the air out of the lungs and they no longer empty efficiently. This cause more air than normal to be present. This phenomenon is called air trapping and causes hyperinflation in the lungs. Extra air in the lungs and the additional effort needed to breathe adds to shortness of breath.
Air obstruction occurs because the air sacs that typically support the airways and the breathing process are unable to open properly during inhalation or exhalation. The damage can also destroy the walls of the air sacs, resulting in fewer and larger inefficient air sacs instead of the normal tiny ones. This leads to a reduction in gas exchange within the lungs.
People with COPD have difficulty emptying the air out of their lungs, which can lead to shortness of breath or feeling extremely tired because the body is forced to work harder to breathe.
Cigarette smoke is the most common cause of COPD, but COPD is not exclusively a smoking disease.
COPD can be linked to many different factors, but the most common cause is cigarette smoke. Other common risks include environmental and genetic factors. Inhaling any type of pollutants, whether it is cigarette smoke, chemicals at work, cooking fumes, or heavy pollution, can cause COPD.
Genetics may also play a role in the development of COPD, even for those who have not been exposed to pollutants. It is suspected that genetics also plays a role in making certain people more sensitive to the effects of cigarette smoke and pollutants compared with others.
The problem with COPD is that many people often do not recognize the symptoms until the disease has progressed into its later stages. Shortness of breath or ongoing cough are often mistaken as being from other causes.
It is important to note the warning signs of COPD and consult a doctor if they appear. Common symptoms include:
- Chronic cough
- Shortness of breath while doing daily activities
- Frequent respiratory infections
- Blueness of the lips or fingernail beds
- Producing higher amounts of mucus than normal
- Chest tightness
People who have mild COPD symptoms may not notice them at first, or they may not cause significant problems. These people may simply have to make some lifestyle changes to help make breathing easier.
How severe a person's condition is depends greatly on how much lung damage they have. If people who smoke continue to do so, the damage to the lungs will occur at a much faster rate. How COPD affects other systems and body parts also provides vital clues about the severity of the disease.
Severe COPD can cause additional symptoms such as swelling in the ankles, feet, or legs, weight loss, and reduced muscle strength and endurance.
Doctors measure the severity of lost lung function in COPD by the amount of air that a person can forcibly exhale in one second (FEV1). This amount decreases as the COPD gets worse.
Acute exacerbation of COPD is a flare-up or episode in which a person's breathing becomes worse than usual and they struggle to maintain their oxygen levels. During these episodes, the airways suddenly become blocked, making COPD symptoms worse.
A COPD exacerbation may be triggered by an infection, and it is important to look out for the warning signs.
A flare-up is typically triggered by an infection either in the airways or throughout the body. Exacerbations can be very serious and may cause further lung damage. As a result, COPD progresses faster.
It is important for those affected to seek treatment as needed. People can avoid exacerbations by knowing the warning signs and taking action immediately.
Symptoms of a flare-up include:
- Increased mucus that may be thicker and darker in color
- Extreme shortness of breath
- Confusion or excessive sleepiness
- Excessive coughing or wheezing
Certain medications, as well as exposure to pollutants or irritants, can cause exacerbations. People who smoke also have more exacerbations than those who do not.
Treatment and prevention
For those who do smoke, the best treatment plan is to stop smoking. Although there is no cure, early treatment is the best defense against COPD, regardless of its stage.
Treatments for COPD include:
- Pulmonary therapy
- Oxygen therapy
- Airway clearance techniques
- Lung surgery
- Flu, pneumonia, and whooping cough vaccines
The goal of COPD treatment is not only to relieve symptoms but also to prevent flare-ups from occurring and to improve a person's quality of life. Frequent episodes can cause the lungs to deteriorate at a faster rate. They also often lead to more frequent emergency room and hospital visits.
It can take a while for someone with COPD to completely bounce back following a flare-up. Some never fully recover to their baseline, or their condition worsens.
To treat flare-ups, doctors commonly use the following measures: