Chronic Obstructive Pulmonary Disease (COPD) / Emphysema

Chronic obstructive pulmonary disease (COPD) is a common, preventable, and treatable condition characterised by persistent airflow limitation -- a progressive reduction in the ability to move air in and out of the lungs. COPD is one of the leading causes of death and disability globally, and is significantly underdiagnosed: more than 70% of people with COPD have never received a formal diagnosis. Many accept worsening breathlessness as an inevitable consequence of ageing or lack of fitness, without realising they have a diagnosable and treatable lung condition.

COPD encompasses several related structural abnormalities in the lungs -- emphysema, chronic bronchitis, and small airways disease -- that develop together to cause progressive airflow obstruction. Unlike asthma, the airflow limitation in COPD is largely fixed and does not fully reverse with bronchodilator treatment. And unlike asthma, COPD is almost always caused by a significant history of inhaled irritants -- predominantly tobacco smoke.

What is Chronic Obstructive Pulmonary Disease (COPD)?

In a healthy lung, air moves freely through progressively smaller airways -- bronchi, bronchioles -- into the alveoli, where oxygen crosses into the blood and carbon dioxide crosses out. The airway walls are flexible, the mucosa is thin, and the alveoli are intact elastic sacs that recoil actively with each breath, assisting exhalation.

In COPD, long-term inhalation of noxious particles (predominantly tobacco smoke) triggers a chronic inflammatory response in the airways and lung tissue. Over years, this inflammation causes three overlapping structural changes:

• Airway inflammation and remodelling: The bronchial mucosa thickens, goblet cells proliferate and produce excess mucus, and the airway walls undergo fibrotic remodelling. The airway lumen narrows, increasing resistance to airflow.
• Alveolar destruction (emphysema): Inflammatory cells release proteases that break down the elastic tissue of the alveolar walls. Alveoli coalesce into enlarged, inefficient spaces. Gas exchange area is lost. The lung loses elastic recoil, causing air trapping and dynamic hyperinflation.
• Small airways disease: The bronchioles (small airways less than 2 mm in diameter) become inflamed, narrowed, and partially obstructed by mucus plugs. These peripheral airways contribute disproportionately to airflow resistance in COPD.

The net result of these changes is persistent, largely irreversible airflow limitation -- measured as a reduced FEV1/FVC ratio on spirometry. Breathing becomes effortful, particularly on exertion and during exhalation, as trapped air accumulates with each breath cycle.

Types of COPD

COPD is not a single pathological entity -- it encompasses several overlapping structural patterns. Most patients have a combination of these changes, but understanding each helps explain the specific symptom profile.

Emphysema

Emphysema develops when the chronic inflammatory process triggered by cigarette smoke and other irritants destroys the walls of the alveoli (air sacs), reducing the surface area available for gas exchange. The lungs lose their elastic recoil, the natural tendency to spring back after inhalation. Air becomes trapped, causing the chest to hyperinflate and the diaphragm to flatten.

Chronic Bronchitis

Chronic bronchitis is a long-term condition where a person has a cough with mucus for at least three months in two consecutive years. It is caused by inflammation of the airways, which makes them produce too much mucus. This mucus can block the airways and allow bacteria to grow, causing repeated chest infections.

Symptoms of COPD

COPD symptoms develop gradually as lung function declines. In the early stages (GOLD 1-2), many patients have minimal or no symptoms at rest and only notice limitation on exertion. The classic symptom triad is:

• Progressive breathlessness: Shortness of breath that gets worse over time. It may first happen during exercise, then during normal activities, and eventually even at rest in severe COPD.
• Chronic cough: A long-lasting cough, often worse in the morning and producing mucus. It may be present for years before the person seeks medical help.
• Increased sputum: Producing more phlegm than usual, especially in the morning. During flare-ups, the phlegm may become thicker, more abundant, and yellow/green.

Additional symptoms in moderate-to-severe COPD

• Wheezing: A high-pitched whistling sound when breathing, especially when breathing out.
• Chest tightness: A feeling of pressure or tightness in the chest, especially after exercise.
• Reduced exercise tolerance: Difficulty walking, climbing stairs, or doing daily activities due to breathlessness.
• Fatigue and weight loss: Feeling very tired and losing weight, especially in severe COPD.
• Ankle swelling: Swelling of the ankles can occur in advanced COPD due to right-sided heart failure.
• Cyanosis: A bluish colour of the lips or fingertips caused by low oxygen levels in the blood.

Causes and Risk Factors of COPD

Primary cause: Tobacco smoke

Cigarette smoking is responsible for approximately 75-80% of COPD cases. The risk is strongly dose-dependent, quantified by 'pack-years' (number of packs per day multiplied by years smoked). Ten or more pack-years is the threshold at which spirometry surveillance is recommended. Pipe and cigar smoking carry similar risks. Both active smoking and second-hand smoke exposure from early life increase COPD risk.

Other inhaled irritants: Southeast Asia

In Southeast Asia and many developing countries, indoor air pollution from biomass burning (wood, charcoal, crop residues, and animal dung used for cooking and heating) is a major cause of COPD -- particularly in non-smoking women. In Singapore and the broader region, outdoor air pollution including haze from forest fires can trigger COPD exacerbations in susceptible individuals.

• Occupational exposures: Mineral dust (coal, silica, grain dust), chemical fumes (isocyanates, cadmium, welding fumes), and organic dust (agricultural and textile industries)
• Indoor biomass smoke: The second most important global cause of COPD after tobacco
• Occupational exposure to pollutants: Long-term exposure to chemical fumes, dusts or vapors in the workplace can irritate and inflame your lungs over time.
• Outdoor air pollution: Particulate matter (PM2.5), nitrogen dioxide, and ozone all contribute to COPD incidence and exacerbations

Genetic and Personal Risk Factors

• Alpha-1 antitrypsin (AAT) deficiency: A genetic condition that reduces protection of the lungs and can cause early COPD and emphysema. It is especially important to check in young patients or those with a family history of COPD.
• Childhood respiratory problems: Frequent infections, asthma, or poor lung development during childhood can lead to lower lung function and increase the risk of COPD later in life.
• Low birth weight: Being born with a low birth weight can increase the risk of developing COPD.
• Asthma: Long-term airway inflammation from asthma can speed up the decline in lung function, especially in smokers.
• Male sex: COPD has traditionally been more common in men, mainly because smoking was more common among men.
• Age: The risk of COPD increases significantly after age 40, especially in people with a long history of smoking.

How COPD is diagnosed

COPD diagnosis requires objective lung function measurement -- it cannot be reliably diagnosed on symptoms or chest imaging alone. The cornerstone investigation is spirometry.

• Spirometry (Lung Function Test): Spirometry is the main test used to diagnose COPD. It measures how much air a person can breathe out and how quickly they can do so. COPD is confirmed when the FEV1/FVC ratio is less than 0.70 after using a bronchodilator. The test takes about 15 minutes and involves breathing forcefully into a mouthpiece. The results also help determine the severity of COPD.
• Bronchodilator Reversibility Test: This test compares lung function before and after using a short-acting bronchodilator such as salbutamol. In COPD, the airway blockage usually changes very little after the medicine. If there is a significant improvement in breathing, it may suggest asthma rather than COPD. This test helps doctors tell the difference between COPD and asthma.
• Chest X-ray: A chest X-ray cannot directly diagnose COPD, but it can show signs such as overinflated lungs and bullae (large air spaces caused by emphysema). It can also help detect other conditions such as pneumonia, lung cancer, or heart failure. A normal chest X-ray does not rule out COPD.
• CT Chest (High-Resolution): A CT scan gives a detailed picture of the lungs and can show the extent of emphysema, bullae, and overinflated lungs. It can also detect bronchiectasis and help check for lung cancer, especially in smokers. CT scans are particularly useful when considering advanced treatments such as lung volume reduction procedures.
• Pulse Oximetry: This is a simple, non-invasive test that measures the oxygen level in the blood (SpO₂) using a device placed on the finger. Low oxygen levels may indicate the need for long-term oxygen therapy (LTOT). It is also used to monitor oxygen levels during COPD flare-ups and exercise.
• Full Blood Count: This blood test can detect high red blood cell levels caused by long-term low oxygen levels, as well as anaemia, which can make breathlessness worse. A high eosinophil count may suggest an asthma-like type of COPD and can help guide treatment.
• Sputum Culture: This test examines mucus from the lungs to find bacteria causing a COPD flare-up. It helps doctors choose the right antibiotic, especially in patients who have frequent flare-ups or do not improve with the first treatment.

Managing COPD Exacerbations

A COPD exacerbation is an acute worsening of respiratory symptoms -- increased breathlessness, increased sputum volume and purulence, and/or worsening cough -- beyond normal day-to-day variation, requiring a change in medication. Exacerbations are the most common reason for COPD-related hospitalisation and are associated with accelerated lung function decline and increased mortality. Each hospitalised exacerbation increases subsequent mortality risk.

Triggers

• Respiratory infections: Viral (rhinovirus, influenza, RSV, COVID-19) account for 50-70% of exacerbations; bacterial infections for 25-50% (Haemophilus influenzae is the most common isolate)
• Air pollution: Haze episodes and periods of high PM2.5 are well-documented exacerbation triggers in Singapore
• Poor inhaler adherence or technique: Many 'exacerbations' reflect undertreated stable disease
• Environmental irritants, allergen exposure, or temperature extremes

Preventing exacerbations

• Inhaler treatment: Using LABA + LAMA inhalers can reduce flare-ups. An inhaled corticosteroid (ICS) inhaler may be added for patients at high risk of exacerbations.
• Vaccinations: Flu, pneumococcal, and COVID-19 vaccines help prevent infections and COPD flare-ups.
• Pulmonary rehabilitation: Starting rehabilitation soon after hospitalisation can improve recovery and reduce the chance of being readmitted.

COPD and Comorbidities

COPD rarely occurs in isolation. Shared risk factors (smoking, ageing, systemic inflammation) and the systemic effects of chronic hypoxaemia, exercise limitation, and corticosteroid use lead to a high burden of comorbid conditions:

• Cardiovascular disease: Coronary artery disease, heart failure, and atrial fibrillation are all significantly more prevalent in COPD patients than in the general population. Cardiovascular events are the leading cause of death in COPD patients.
• Lung cancer: Smoking is the dominant shared risk factor. All COPD patients with a significant smoking history meet criteria for low-dose CT lung cancer screening.
• Anxiety and depression: Extremely common and significantly underdiagnosed. Both worsen breathlessness perception, reduce treatment adherence, and impair quality of life. Should be screened and treated alongside the COPD.
• Osteoporosis: From systemic corticosteroids, reduced activity, low vitamin D, and the systemic inflammatory state. DEXA scanning and bone protection should be considered in patients on regular oral or frequent inhaled corticosteroids.
• Muscle wasting and weight loss: Severe COPD, especially emphysema, can cause loss of muscle and body weight. Checking nutrition and providing nutritional support can help improve overall health.
• Obstructive sleep apnoea: The combination of COPD and OSA produces significantly worse nocturnal desaturation than either condition alone and requires combined treatment.
• Gastro-esophageal reflux disease (GERD): A trigger for exacerbations through microaspiration and airway irritation. Proton pump inhibitor treatment in GORD-positive COPD patients reduces exacerbation frequency in some patients.