Chronic obstructive pulmonary disease is the collective term for lung disease caused by a long-term combination of emphysema and bronchitis. Breathing becomes more difficult over time because the airways become narrowed, the surface area of the lungs is reduced and breathing in and out becomes more of an effort.
Bronchitis is inflammation of the bronchi, which are the tubes that carry air deep into the lungs. As the lining of the bronchi becomes inflamed, the airways narrow. The inflammation also tends to produce a lot of mucus, which results in a persistent cough as the lungs try to clear it.
Emphysema is long-term damage to the alveoli (the tiny air sacs in the lungs). The delicate membranes become damaged and replaced with scar tissue. This has two key effects: gas exchange is less efficient and the lung tissue loses its natural elasticity, so that breathing out takes more of an effort than normal.
COPD has several other names:
Chronic obstructive respiratory disease (CORD)
Chronic obstructive lung disease (COLD)
Chronic airflow limitation (CAL)
Chronic obstructive airway disease (COAD).
How common is chronic obstructive pulmonary disease?
In the UK, close to one million people have been diagnosed with chronic obstructive pulmonary disease. It is the fourth most common cause of death after heart disease, cancer and stroke. It is thought that another two million have a mild form of COPD but have yet to seek medical help.
What is the impact of COPD?
Mild COPD may produce few symptoms beyond occasional breathlessness and coughing in the morning (‘smoker's cough’), after exercise or following an infection. More severe COPD can result in a persistent, productive cough (one that produces phlegm) and breathlessness/wheezing even following mild activity. At its most serious, chronic obstructive pulmonary disease is disabling, with those affected not able to walk more than a few steps without gasping for breath. Some people with COPD eventually need to breathe extra oxygen most of the time.
It is common for people with chronic obstructive pulmonary disease to experience an exacerbation (a flare-up) of symptoms due to bacterial and viral infections in the lungs, which are more common in the winter months.
Asthma may also make the situation worse. Allergens and various other environmental factors can trigger a reaction that causes airways to become narrower. Fortunately, the same medications can be used to relieve both asthma and COPD.
What causes chronic obstructive pulmonary disease?
Smoking/tobacco exposure: this is by far the most common cause of COPD. People who have never smoked rarely develop chronic obstructive pulmonary disease
Air pollutants and industrial irritants. Working conditions in the UK have improved dramatically over the last few decades, but dust particles inhaled by miners or textile workers can cause COPD, or make it worse if the individual is also a smoker. Exposure to smoke during a fire and breathing in hazardous gases as a result of war can also result in chronic obstructive pulmonary disease
Genetic factors. It is known that some people have a genetic predisposition to develop COPD, but the exact link is not known. It has been observed that about 2% of COPD cases are linked to an alpha 1-antitrypsin (AAT) deficiency.
AAT is a helpful enzyme that prevents lung damage caused by damaging enzymes such as elastase and trypsin. These are produced in the lungs as a result of the inflammatory response to cigarette smoke.
How is chronic obstructive pulmonary disease diagnosed?
Spirometry is usually used to diagnose COPD and assess how severe it is. This involves breathing out as hard as you can into a spirometer, which measures the air pressure you create. The same test is carried out to diagnose asthma.
However, unlike asthma, chronic obstructive pulmonary disease cannot be completely relieved by medication because there is permanent damage to lung tissue.
Two measurements commonly taken when assessing COPD are:
FEV1: forced expiratory volume. This is the amount of air exhaled in one second
FVC: forced vital capacity. This is the total amount that can be exhaled in one breath. Results are compared to the average value for someone of the same age, height, weight and sex who does not have chronic obstructive pulmonary disease.
These two values are used to calculate the FEV1/FVC ratio. This gives a measure of how easily the air in the lungs can be expelled. The lower the value, the more severe is the narrowing of the airways.
How is the FEV1/FVC ratio used to classify COPD?
People with chronic obstructive pulmonary disease are given a diagnosis based on the difference in their exhalation capability compared to someone with healthy lungs:
Mild COPD: an FEV1/FVC ratio at least 80% of predicted value
Moderate COPD: an FEV1/FVC ratio between 50% and 79% of predicted value
Severe COPD: an FEV1/FVC ratio between 30% and 49% of predicted value
Very severe COPD: an FEV1/FVC ratio less than 30% of predicted value.
What treatment is available for chronic obstructive pulmonary disease?
COPD cannot be cured but some lifestyle changes and a variety of treatments can help to ease symptoms.
Stop smoking. If the source of the irritation is removed, the inflammation will die down and the damage to the air sacs will stop. Initially the cough may get worse due to the lining of the airways becoming re-activated and becoming more efficient at removing mucus. This should not be taken as a sign to start smoking again
Bronchodilator inhalers will relax the muscle in the walls of the smaller air tubes, making them larger. They give instant relief from asthma but also help in chronic obstructive pulmonary disease
Steroid inhalers dampen down the inflammatory response and so help to open up the airways and reduce mucus production
Antibiotics will be prescribed if you have an infection. It is important that infections are treated early so watch out for a cough that starts producing deep yellow or green mucus, and for symptoms such as aching and a fever
Flu vaccinations are a worthwhile preventative measure. Viral infections can often be followed by bacterial infections.
People who are very breathless may not be able to use inhalers effectively, so a nebuliser might help. This device allows drugs to disperse in an aerosol inside a wide tube. The aerosol can be inhaled by breathing in and out through the end of the tube via a mouthpiece.
Treatments in a COPD emergency
Severe cases of COPD may require hospitalisation, so that the person affected can be more closely monitored. Blood tests are used to measure the levels of dissolved oxygen and oxygen is then given as necessary. Chest X-rays and other imaging techniques can be used to assess lung damage.
Severe cases of COPD may respond to oxygen given around the clock, delivered from a cylinder via a mask or nasal cannula (soft tube inserted into the nostrils). Studies have shown that people with severe chronic obstructive pulmonary disease survive longer when they take extra oxygen throughout the day as well as during the night.
Surgery for COPD
Surgery is not normally recommended for people with chronic obstructive pulmonary disease, though it can be of use in certain circumstances. Three main forms of surgery may be considered:
Bullectomy: a bulla is a large space in the lung filled with air. It forms after severe, long-term lung damage. The pressure of this air space can compress the healthy lung tissue around it. A bullectomy can be carried out to remove the bulla so that the air sacs in the lung tissue that is left can inflate and deflate normally
Lung volume reduction surgery: this involves removing regions of damaged lung tissue. Although a drastic treatment for emphysema, surgery gives the remaining healthy parts of the lung the space to inflate and deflate, which can ease breathing
Lung transplantation: this is sometimes performed as a curative treatment in people with severe COPD, particularly those who are relatively young when they develop the disease.