Chronic obstructive pulmonary disease (COPD) is a progressive, chronic lung disease. Several conditions fall under this umbrella diagnosis, the two most common being chronic bronchitis and emphysema, which often coexist in patients with COPD. Twelve million people in the U.S. have been diagnosed with COPD and it is the second most common cause of disability and the fourth leading cause of death in the country.
What Causes COPD?
The most significant cause of lung damage is tobacco smoke. It is estimated that up to 90% of COPD cases can be attributed to smoking. Inflammation due to free radicals and cytokines from tobacco destroys the enzymes that protect the lung. But researchers still do not fully understand how tobacco smoke and other inhaled particles damage the lungs to cause COPD.
Although there is currently no cure, COPD is both a preventable and treatable disease. The diagnosis of COPD should be considered in anyone who has shortness of breath, chronic cough or sputum production, and/or a history of exposure to risk factors for the disease, particularly regular tobacco smoking. No single symptom or sign can adequately confirm or exclude the diagnosis of COPD, although it is uncommon in individuals under forty.
Chronic Bronchitis & COPD
To understand how COPD affects the body, let's first examine how the lungs work. The lungs have two main parts: the bronchial tubes (airways) and the air sacs (alveoli). Air enters the lungs through the bronchial tubes and is exchanged with the blood in the alveoli.
Lung damage and inflammation in the large airways (i.e, the trachea and main bronchial tube) results in chronic bronchitis, a precursor to COPD. A primary symptom of chronic bronchitis is a cough with sputum production that lasts for several months a year, and is characterized by an increased number and activity of the mucus glands in the airway. The mucus narrows the airways and causes a cough with sputum. The airways become inflamed, leading to scarring and thickening of the walls (chronic obstructive bronchitis) and results in chronic narrowing of the airways. As chronic bronchitis progresses, airflow is limited. Patients with advanced COPD who have primarily chronic bronchitis rather than emphysema commonly have a bluish color of the skin and lips (cyanosis).
Emphysema & COPD
Emphysema is another condition which can result in COPD. Emphysema is the widespread and irreversible destruction of the normal air sacs due to multiple causes. As emphysema progresses, larger and fewer air sacs (alveoli) are left behind due to the loss of tissue with collapse of the small airways leading to the alveoli. Many of these multiple cavities are lined by heavy black carbon deposits, reducing the amount of air and the area available for the exchange of oxygen and carbon dioxide which occurs during normal breathing. In other words, the result is reduced airflow. These small airways are also more likely to collapse, further limiting airflow.
Patients with emphysema exert a considerable effort during exhalation, which can cause a pink color in their faces. In COPD, the greatest reduction in airflow occurs when breathing out because the pressure in the chest tends to compress, rather than expand, the airways. In theory, airflow could be increased by breathing more forcefully, increasing the pressure in the chest during expiration. But the benefits of this are limited.
If the rate of airflow is too low, a person with COPD may not be able to completely finish expelling the air before needing to take another breath. This is particularly common during exercise. When this occurs, some air from the previous breath remains within the lungs when the next breath is started, resulting in an increased volume of air in the lungs (hyperinflation).
Both of the above processes are linked to shortness of breath (dyspnea) in COPD. It is less comfortable to breathe with hyperinflation because it takes more effort to move the lungs and chest wall when they are already stretched by hyperinflation. Decreased oxygen absorption and carbon dioxide expiration further complicate the situation, requiring the patient to breathe faster and more deeply to compensate. As a result, the patient may still feel short of breath (dyspnea), and experience headache and drowsiness.
Advanced COPD can lead to complications beyond the lungs, such as undesirable weight loss, increased blood congestion in the lungs, and even heart failure. Osteoporosis, heart disease, muscle wasting and depression are all more common in people with COPD. An acute worsening of COPD symptoms (shortness of breath, quantity and color of phlegm) typically lasts for several days and may be triggered by an infection (caused by bacteria, viruses or both) in 75% or more of the deterioration.
The diagnosis of COPD is confirmed by a breathing test (spirometry) which measures the greatest volume of air that can be breathed out in the first second of a large breath and the greatest volume of air that can be breathed out in a whole large breath. Spirometry can also help to determine the severity of COPD. The severity of dyspnea and exercise limitation, among other factors, can be combined with spirometry results to obtain a COPD severity score that takes multiple dimensions of the disease into account.
An X-ray of the chest may show an over-expanded lung and can be useful to help exclude other lung diseases. Complete spirometry tests plus measurements of oxygen and carbon dioxide transfer may also show hyperinflation and can discriminate between COPD with emphysema and COPD without emphysema. A CT of the chest may show the distribution of emphysema throughout the lungs and can also be useful to exclude other lung diseases. A blood count is also helpful to show whether there are too many blood cells.
What You Can Do To Prevent COPD
Tobacco smoke has proven to be the most significant cause of lung damage. Unsurprisingly, smoking cessation is one of the most important factors in slowing down the progression of COPD. In fact, even at a late stage of the disease it can significantly reduce the rate of deterioration in lung function and delay the onset of disability and death. It is the only standard intervention that can delay the rate of progression of COPD.
Most people who quit smoking go through several attempts before kicking the habit for good. The chance of successfully stopping smoking can be greatly improved through social support, engagement in a smoking cessation program and the use of drugs such as nicotine replacement therapy, bupropion and varenicline.
There are other preventative measures to reduce the likelihood that workers in at-risk industries such as coal mining will develop COPD. For one, air quality can be improved by pollution reduction efforts. Another measure is limiting one’s exposure to known pollutants; a person who has COPD may experience fewer symptoms by staying indoors on days when air quality is poor.
Author’s Note: For further reading on COPD, see these useful references: