Chronic obstructive pulmonary disease (COPD) is more common than most people think. According to the American Lung Association, COPD—a chronic lung disease marked by damage and inflammation in certain parts of the lungs that makes it hard to breathe—is the third leading cause of disease-related death in the U.S., behind only heart disease and cancer.
Perhaps not surprisingly, the majority of cases are caused by smoking. In fact, “about 80 percent of people with COPD are current or former smokers,” says Russell G. Buhr, M.D., Ph.D., a pulmonary and critical care physician at UCLA Health in Los Angeles. But long-term exposure to second-hand smoke and other pollutants can also cause someone to develop COPD.
There are two main types of COPD: emphysema and chronic bronchitis. Since most people have both to some degree, COPD is usually used as an umbrella term to describe the chronic decline of lung function that happens as a result of both or either of these conditions. Common symptoms include increasing shortness of breath, a cough that produces a lot of mucus, wheezing, and chest tightness.
How Exactly Does COPD Impact the Lungs?
To understand how COPD causes its hallmark symptoms, it helps to first understand how the lungs work. So, let’s break that down.
When you inhale, either through your nose or mouth, the air travels down the back of the throat (pharynx), through the voice box (larynx), and into your windpipe (trachea). The trachea is divided into two passages called bronchial tubes. One leads to the left lung and the other leads to the right lung.
In the lungs, the bronchial tubes branch out into thousands of smaller air passages called bronchioles, which have tiny air sacs called alveoli on the ends. When you breathe in, these tiny sacs fill with air and expand like balloons; when you exhale, they deflate again. The walls of the alveoli are lined with capillaries, so when air reaches these air sacs, oxygen is easily transferred to the blood so that it can be carried throughout your body. At the same time, carbon dioxide moves into the alveoli so that you can exhale it back out (we don’t want that in our bodies).
That’s how a healthy set of lungs functions.
In emphysema, on the other hand, the walls between the tiny air sacs are damaged, causing them to lose their elasticity and shape, essentially becoming deflated. The walls may even completely break down.
“When the walls of the air sacs get destroyed, we end up with fewer but larger sacs,” Dr. Buhr explains. “And since they’ve lost their stretch, air then gets trapped in the lungs, making it harder to exhale. That’s why people are more symptomatic as they’re breathing out,” he says. “Wheezing—a high-pitched whistling sound made while you breathe—is caused by turbulent airflow as you’re trying to breathe out.”
In chronic bronchitis, the lining of the airways becomes constantly irritated and inflamed, causing it to swell and prompting thick mucus to form. This inflammation and excess mucus can obstruct normal breathing and often causes a disruptive, chronic cough. It can also lead to recurrent infections, says Dr. Buhr.
All of these structural changes in the lungs are what contribute to COPD, and as the disease progresses, symptoms will worsen as well.
The Stages of COPD
COPD is a progressive disease, meaning patients’ lung function will continue to decline over time and symptoms will worsen. How quickly this happens depends on each person’s individual case, but overall, your prognosis will be better if you’re diagnosed earlier and quit smoking sooner, says Lori Shah, M.D., pulmonologist and lung transplant expert at New York-Presbyterian in New York City. This is the best way to maintain your current lung function and slow down the decline.
When you’re diagnosed with COPD, your doctor will determine how advanced the disease is by doing a pulmonary test and assessing your symptoms. Dr. Shah says the system for deciphering a patient’s COPD stage used to be based on one lung-test number: your FEV1, or forced expiratory volume, a measurement of how much air you can force out of your lungs in one second. Your FEV1 is still very important for helping determine your stage, but many doctors now consider other factors, like how symptomatic you are, in addition to FEV1 (more on that later).
When you take a lung-function test to determine your FEV1, the technician will tell you to take in a really deep breath, blast it out fast, then keep blowing and blowing as long as possible. The machine measures how much air you blew out in the very first second of that long breath out. This is your FEV1.
The machine then takes that number and compares it to the amount of air a person your age, height, and race, with normal, healthy lungs would blow out in that first second. From this comparison, a patient’s COPD can be categorized as very mild, moderate, severe, or very severe. These four stages make up the GOLD staging system, developed by the Global Initiative for Chronic Obstructive Lung Disease or GOLD:
- Stage 1: Very mild COPD with a FEV1 about 80% or more of normal
- Stage 2: Moderate COPD with a FEV1 between 50% and 80% of normal
- Stage 3: Severe emphysema with FEV1 between 30% and 50% of normal
- Stage 4: Very severe COPD with a lower FEV1 than Stage 3, or those with Stage 3 FEV1 and low blood-oxygen level
The COPD Foundation also has its own staging system called the Spirometry Grade (SG), which is based off the ratio of your FEV1 compared to FVC, or forced vital capacity, which is a measure of the amount of air you blow out in the entire exhalation, not just the first second. Here’s how it breaks down:
- SG 1 Mild: FEV1 to FVC ratio less than 0.7 | FEV1 about 60% or more of normal
- SG 2 Moderate: FEV1 to FVC ratio less than 0.7 | FEV1 between 30% and 59% of normal
- SG 3 Severe: FEV1 to FVC ratio less than 0.7 | FEV1 less than 30% of normal
Your doctor may use the GOLD system or the COPD Foundation system. Dr. Shah says it doesn’t really matter which system your doctor uses, because either can give them a better idea of where you are and what sort of treatment you may need.
How Your Stage Helps Guide Treatment
While knowing your stage of COPD can be a helpful guide to figure out how your lung function is changing over time, this very straightforward grading system leaves out a key factor: how the patient is feeling and the symptoms they’re experiencing.
That’s why GOLD now recommends using an ABCD grading system that takes into account both the stage a patient is in (one through four) and other factors like:
- How symptomatic you are
- How far you can walk before having to stop and catch your breath
- How much you’re coughing
- If trouble breathing is interfering with sleep or causing anxiety
- How many flare-ups you’ve had in the past year and whether or not they required hospitalization
Taking all these things into consideration, an A grade is given to those experiencing intermittent or low-grade persistent symptoms and a D grade is given to those who are highly symptomatic and experiencing frequent or severe flare-ups
Like GOLD, the COPD Foundation also notes that symptoms need to be considered along with the Spirometry Grade in order to make the best treatment decisions for each individual. In the earlier, less severe stages of COPD, you may be able to alleviate symptoms by using a bronchodilator, a medication that relaxes and opens the airways, or bronchi, in the lungs to make breathing easier. Those in more advanced stages with severe symptoms may need a variety of other treatments, such as corticosteroids, prescription anti-inflammatories, antibiotics (if an infection is worsening symptoms), or even oxygen therapy if blood oxygen levels are especially low.
It’s important to remember that COPD impacts everyone differently, so you should always tell your doctor how you’re feeling and how the disease is impacting your life. That way, they can use that information, in conjunction with your tests, to get you on the right treatment plan to minimize symptoms and maximize your quality of life.