3 Chronic Obstructive Pulmonary Disease

COPD and diagnosis

Chronic obstructive pulmonary disease (COPD) is a common, preventable, and treatable condition involving persistent respiratory symptoms and airflow limitation. It includes different patterns of airway and lung damage, often combining chronic bronchitis and emphysema.

Diagnosis is confirmed with spirometry. Persistent airflow obstruction is generally defined by a post-bronchodilator $\mathrm{FEV}_1/\mathrm{FVC} < 0.70$.

Causes and effects

Long-term exposure to tobacco smoke is a major cause of COPD. Air pollution, workplace exposures, and inherited conditions such as alpha-1 antitrypsin deficiency can also contribute.

Inflammation and structural damage can thicken and narrow small airways, increase mucus production, destroy alveolar walls, and reduce the lungs’ elastic recoil. These changes can make exhalation difficult, causing air trapping and lung hyperinflation, and can impair gas exchange. The resulting effects may include low blood oxygen and, in advanced disease, carbon-dioxide retention.

Damaged air sacs may empty slowly during exhalation. During activity, a person may begin the next breath before fully breathing out, increasing air trapping and breathlessness.

Recognizing exacerbations

A COPD exacerbation is an acute worsening beyond a person’s usual day-to-day symptoms. Breathlessness, cough, sputum volume, or sputum purulence may increase. Viral or bacterial infections are common triggers; smoke, air pollution, and other irritants can also contribute.

Pneumonia, heart failure, and pulmonary embolism can mimic or worsen an exacerbation and may need separate assessment.

Treating exacerbations

Treatment depends on severity and clinical assessment. Common measures include short-acting inhaled bronchodilators, a brief course of systemic corticosteroids for many moderate or severe episodes, and antibiotics when bacterial infection is likely.

Severe breathlessness, confusion, cyanosis, poor response to usual treatment, or suspected respiratory failure requires urgent evaluation. In hospital, blood-gas testing may help assess oxygenation, carbon-dioxide retention, and acidosis. Noninvasive ventilation may be needed for selected patients with acute respiratory failure, particularly when carbon dioxide is elevated and blood pH is low.

Oxygen use and safety

Oxygen treats hypoxemia; it is not a general treatment for breathlessness when blood oxygen is adequate. During an acute exacerbation, oxygen should be given when indicated and titrated to a prescribed target rather than delivered at an unnecessarily high concentration.

For patients at risk of hypercapnic respiratory failure, clinicians commonly use a target oxygen saturation of $88\%-92\%$ while obtaining blood gases and further assessment. This is a monitored clinical target, not a universal target for every person with COPD. Excess oxygen can worsen hypercapnia in susceptible patients through changes in ventilation–perfusion matching and carbon-dioxide carriage; oxygen should not be withheld from a hypoxemic patient.

Long-term oxygen may benefit people with COPD and severe, persistent resting hypoxemia. It should be prescribed after appropriate assessment when the person is clinically stable. Oxygen started during an exacerbation may no longer be needed after recovery, so the need should be reassessed. Oxygen also creates a fire hazard: avoid smoking and open flames near oxygen equipment.

Ongoing management

Management is individualized and aims to reduce symptoms, preserve activity, prevent exacerbations, and address other health conditions.

• Reduce exposures: Stop smoking and reduce exposure to smoke, dust, fumes, and air pollution.

• Use inhaled medicines appropriately: Long-acting bronchodilators are central for persistent symptoms. Inhaler choice depends on symptoms, exacerbation history, response, and other clinical factors. Check inhaler technique and adherence. Inhaled corticosteroids are appropriate for selected patients, not automatically for everyone with COPD.

• Support function: Pulmonary rehabilitation combines supervised exercise, education, and breathing strategies to support function and quality of life.

• Prevent and plan: Recommended vaccinations, an agreed exacerbation action plan, and regular review can help reduce risk and support timely care.

• Reassess over time: Review symptoms, exacerbations, inhaler technique, oxygen need when relevant, and comorbidities such as cardiovascular disease, anxiety, or depression.