最後更新日期 十一月 22, 2021.
COPD (chronic obstructive pulmonary disease) is a common progressive lung disorder characterised by airway obstruction with little or no reversibility. This irreversibility distinguishes it from asthma, in which airway obstruction is reversible. COPD is the third leading cause of death worldwide and accounted for 2.7% of all registered deaths in Hong Kong in 2017. Smokers are significantly more likely to develop COPD. Although there is no cure for COPD, it is treatable and preventable. Read more to learn about the causes, symptoms, prevention and treatment of COPD.
What is COPD?
COPD is a group of diseases in which long-term lung damage leads to the obstruction or narrowing of the airways. The most frequent forms of COPD are chronic bronchitis and emphysema; commonly, people suffer from both conditions at the same time to varying degrees.
Chronic bronchitis is characterised by inflammation and narrowing of the bronchial tubes, which carry air to and from the air sacs in your lungs. Mucus builds up due to irritation, making it harder for your lungs to transport oxygen and carbon dioxide. As a result, patients develop a chronic cough trying to clear the mucus from their airways.
In emphysema, on the other hand, the inner walls between air sacs are damaged, creating larger air spaces instead of tiny air sacs. As a result, the shape and elasticity of the air sacs are lost, trapping more air in your lungs when you exhale. Destruction of the air sacs also reduces the surface area available for air exchange, limiting the amount of oxygen entering the lung and bloodstream. Patients with emphysema commonly develop air blisters (blebs) or air cavities (bullae) due to the destruction of the air sacs. If large bullae rupture, pneumothorax, or collapsed lung, can result.
COPD predisposes to lung infections. It also increases the risk of other diseases, such as heart problems, lung cancer, osteoporosis, depression and anxiety. Although COPD worsens over time, early treatment can slow the progression, control signs and symptoms and improve quality of life.
Signs and Symptoms of COPD
People may be unaware of COPD in the early stages as it usually begins with subtle symptoms. When COPD progresses, signs and symptoms become more severe and may include:
- Shortness of breath, especially during and after physical exercises
- Wheezing: High-pitched whistling sound made while breathing.
- Chronic cough
- Excessive production of mucus / phlegm / sputum
- Frequent respiratory infections
- Chest tightness
- Swollen feet and ankles
- Weight loss
You should seek medical help immediately if you experience the following acute signs and symptoms of COPD:
- Hypoxia: Lack of oxygen resulting in blue discolouration of lips, hands and feet.
- Tachycardia: Rapid heartbeat
- Trouble catching your breath or inability to talk due to breathlessness
Causes and Risk Factors of COPD
Smoking is the leading cause of COPD in developed countries. Cigarette smoking produces harmful chemicals that can damage your lungs, making you more susceptible to COPD and respiratory infections. Both first-hand smoking and second-hand smoking cause COPD.
However, non-smokers can also develop COPD due to genetic causes or exposure to other irritants. In developing countries where living environments are poorly ventilated, fumes from burning fuel used for cooking and heating can be a risk factor contributing to COPD. Other irritants include second-hand smoke, air pollution, harmful chemicals, dust, or fumes from the workplace.
A rare genetic disorder called alpha-1-antitrypsin deficiency (AATD) reduces the amount of the proteins, called alpha-1-antitrypsins, that protect the lung and the liver. Lung damage results, leading to early COPD.
Apart from the abovementioned causes of COPD, the risk factors below also increase the risk of developing COPD:
– Age: Most people who are diagnosed with COPD are at least 40 years old.
– Asthma: Patients with asthma who smoke are more likely to develop COPD than non-asthmatic smokers.
Diagnosis of COPD
People frequently overlook the symptoms of COPD until the disease has progressed significantly. In order to diagnose COPD accurately, your doctor will review your signs and symptoms, discuss your medical conditions, smoking history, family history and may look for any possible chronic exposure to lung irritants. Your physician will also auscultate (listen to your lungs) with a stethoscope to determine if there are any abnormal breathing sounds and examine you for other signs of lung disease.
If COPD is suspected, your doctor may need to confirm the diagnosis by arranging some of the following procedures:
- Pulmonary function tests: Spirometry is a standard test to measure how much air your lungs can hold and how fast you exhale. It is performed by simply blowing air into a small machine called a spirometer. This test can detect COPD and assess the progress of the disease. Other tests such as lung volume testing (body plethysmography), gas diffusion testing, and exercise stress testing can also be done.
- Imaging tests: Chest X-ray and CT scan are generally used to diagnose emphysema and examine for other lung or heart diseases, such as tuberculosis, lung cancer, and heart failure.
- Arterial blood gas (ABG) test: This test measures the oxygen levels in your blood in order to assess your lungs’ ability to carry out effective gas exchange. This is done to determine the severity of COPD and whether you need long-term oxygen therapy.
- Sputum examination: Examining the sputum can help to rule out other lung diseases, such as lung cancer or tuberculosis. It may also be used to assess COPD exacerbations.
Assessment of COPD: Grades and Groups
To describe the severity of your disease, your doctor may refer to the GOLD guideline of COPD. The objectives of COPD assessment are to determine the severity of airflow limitation, the range of symptoms, and the risk of COPD exacerbation, and hence to guide therapy.
The classification of airflow limitation severity is based on the result of spirometry, which measures FEV1, or the amount of air you can force out from the lungs in the first second of forced expiration. The lower the FEV1, the more severe the condition.
FEV1 (% predicted)
GOLD Grade 1
GOLD Grade 2
50% - 79%
GOLD Grade 3
30% - 49%
GOLD Grade 4
Very severe COPD
The severity of your COPD symptoms is also measured, mainly by CATTM (GOLD Assessment Test) and mMRC (Modified Medical Research Council) questionnaires. CATTM scores range from 0-40 and measure health status impairment in COPD, while mMRC scores have five grades and provide a measure of breathlessness.
Lastly, your doctor will assess your risk of COPD exacerbation. COPD exacerbation is defined as “an acute worsening of respiratory symptoms that needs additional therapy”. The risk is predicted based on the history of exacerbation events.
Combining the measurement of symptoms and risk of COPD exacerbation, your physicians will classify your COPD condition into these four groups:
- Group A: Low risk of exacerbation, less symptomatic
- Group B: Low risk of exacerbation, more symptomatic
- Group C: High risk of exacerbation, less symptomatic
- Group D: High risk of exacerbation, more symptomatic
Complications of COPD
It is important to prevent and treat COPD in its early stages to avoid any of the following serious complications:
- Respiratory infections: COPD increases the chance of respiratory illnesses such as pneumonia, colds and flu. Bacterial or viral infections often lead to COPD exacerbations, which can be life-threatening.
- Pulmonary hypertension and heart diseases: COPD leads to increased blood pressure in the pulmonary circulation by thickening and narrowing its blood vessels. The higher pressure means your heart needs to pump harder and becomes stressed, resulting in other problems such as heart failure.
- Depression: Since COPD may affect daily activities due to fatigue and difficulty breathing, it may contribute to the development of depression and anxiety.
- Pneumothorax (collapsed lung): Pneumothorax is the leakage of air into the pleural space between your lungs and chest wall. COPD patients are at higher risk of pneumothorax as the lung tissue is damaged and prone to developing air blisters or blebs. If a bleb ruptures, air may escape into the pleural space, resulting in pneumothorax.
- Lung cancer: COPD increases the risk of lung cancer.
Treatments of COPD
COPD cannot be cured, but it can be treated. Effective treatments can control COPD symptoms, slow down disease progression, improve quality of life, and reduce the risk of COPD exacerbation and complications.
Quitting smoking can significantly slow down COPD progression, improve symptoms and prevent the development of other diseases and complications. It is the single most important thing you can do for yourself. However, smoking cessation can be difficult. If you are prepared to stop smoking, discuss it with your doctor. There are several regimens and medications that can help you!
Eating a balanced diet and regular exercise can strengthen your body and improve symptoms. Maintaining a healthy weight is also essential. If you are underweight, you may lose muscle mass, including the muscles that help you breathe. Excess weight is also harmful, as it increases the work of breathing.
Medications for COPD
Bronchodilators relax the muscles around your airways, which helps to keep them open and makes breathing easier. This type of medication is usually administered by inhaler.
Short-acting bronchodilators (e.g. ipratropium, salbutamol) have a rapid onset of action and are used when you experience acute shortness of breath. They can help quickly; however, the effect does not last long (4-6 hours).
In addition to short-acting bronchodilators, regular use of long-acting bronchodilators can alleviate COPD symptoms, improve lung function and reduce the risk of COPD exacerbations. Long-acting beta-agonists (LABA, e.g. salmeterol, formoterol) and long-acting muscarinic-agonists (LAMA, e.g. tiotropium) are comparable and can be used together.
- Inhaled corticosteroids (ICS)
ICS (e.g. fluticasone, budesonide) reduces inflammation of the airways and mucus production. They are usually used in combination with a long-acting bronchodilator.
- Phosphodiesterase-4 (PDE-4) inhibitors such as Roflumilast are a relatively new class of oral medication used to reduce airway inflammation and prevent exacerbations in patients with severe COPD and chronic bronchitis.
Theophylline is an old non-prescription, inexpensive drug in Hong Kong that can relax the muscles of the airways and open up the airways in the lungs making breathing easier. In doses that don’t cause toxicity, it is only mildly effective. It is used only occasionally and in combination with other more effective treatments.
If there are signs of infection, such as pneumonia or an acute exacerbation of COPD, antibiotic treatment might be needed temporarily. Commonly used antibiotics are amoxicillin-clavulanic acid and azithromycin.
Your physician will likely also recommend that you get vaccinated against influenza (annual flu shots), pneumococcal pneumonia (Prevenar and Pneumovax vaccines), and of course, COVID-19 to prevent respiratory infections.
- Other medications
Oral corticosteroids can be used in patients with acute exacerbations of COPD. Mucolytic agents (e.g. acetylcysteine) may be used to clear the airways by making it easier to cough up mucus.
Other therapies for COPD
- Oxygen therapy: Oxygen therapy is used when you have severe COPD and a low oxygen level in your blood. You may need to carry a light and portable oxygen device with you on a long-term basis.
- Pulmonary rehabilitation: This is a comprehensive intervention combining exercise training, education and behaviour change in order to improve symptoms, quality of life and lung function. It generally requires various healthcare professionals working together to tailor a program that maximises your personal benefit.
- Surgery: Some surgical procedures may be required for patients with severe COPD and symptoms which are not responsive to medications. These surgeries include lung volume reduction, bullectomy (removing air spaces in the lungs), and lung transplantation.
COPD Exacerbation Management
An exacerbation of COPD is a sudden worsening of symptoms that requires prompt treatment. The key feature of COPD exacerbation is increased shortness of breath. Other symptoms include increased sputum purulence, sputum volume, cough and wheeze. Although COPD exacerbations can be caused by bacterial infections and environmental factors, such as air pollution, the leading cause is respiratory viral infections.
COPD exacerbations can range from mild to severe and often last for 7-10 days. It is important to understand exacerbation symptoms and know when to seek healthcare, as an exacerbation can significantly affect one’s health status and cause many complications.
An exacerbation can be managed in either the outpatient or inpatient setting, depending on the severity of the current episode and the severity of the underlying disease. Mild COPD exacerbations may be treated with short-acting bronchodilators only. For moderate COPD exacerbations, additional inhalers, antibiotics and/or oral corticosteroids may be needed.
Suppose you experience a sudden worsening of shortness of breath, cyanosis (bluish discolouration of the body or nails), peripheral oedema (swelling), confusion or drowsiness. In that case, you will likely need to be hospitalised because these symptoms may progress to respiratory failure. Supplemental oxygen, additional medications and treatments are usually required.
To prevent further exacerbations, good compliance and adherence to treatment as well as lifestyle modification are essential. It is especially important to quit smoking and avoid lung irritants.
Prevention of COPD
Since the cause of COPD is clear, the following approaches can help prevent COPD:
- Never smoke or quit smoking. If you have trouble quitting, seek help from a smoking cessation program.
- Put on protective equipment; for example, wear an appropriate face mask at all times when working with chemical fumes and dust.