• Clinical science

Chronic obstructive pulmonary disease


Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by airway obstruction due to inflammation of the small airways. It is caused predominantly by inhaled toxins, especially via smoking (90% of cases), but air pollution and recurrent respiratory infections can also cause COPD. Some individuals are genetically predisposed to COPD, particularly those with α1-antitrypsin deficiency (AATD). COPD begins with chronic airway inflammation that usually progresses to emphysema, a condition that is characterized by irreversible bronchial narrowing and alveolar hyperinflation. These changes cause a loss of diffusion area, which can lead to inadequate oxygen absorption and CO2 release, resulting in hypoxia and hypercapnia. Most affected individuals present with a combination of dyspnea and chronic cough with expectoration. In later stages, COPD may manifest with more severe symptoms such as tachypnea, tachycardia, and cyanosis. Diagnosis is primarily based on clinical presentation and lung function tests, which typically show a decreased ratio of forced expiratory volume (FEV) to forced vital capacity (FVC). Imaging studies, such as chest x-ray, are helpful in assessing disease severity and the extent of possible complications, but they are not required to confirm the diagnosis. ABG and pulse oximetry are useful for quickly assessing the patient's O2 status. All COPD patients should be staged according to the staging system of the Global Initiative for Chronic Obstructive Lung Disease (GOLD), which considers a variety of factors (e.g., exacerbations, symptom severity, FEV1). Treatment options depend on the GOLD stage and mainly consist of short- and long-acting bronchodilators (beta-agonists and parasympatholytics) and glucocorticoids. Individuals with advanced disease typically require oxygen supplementation, which is the only treatment that decreases mortality. COPD may cause complications such as pulmonary hypertension or respiratory failure; the most significant complication is acute exacerbation of COPD (See AECOPD).


  • A chronic pulmonary disease characterized by persistent respiratory symptoms and airflow limitation (postbronchodilator FEV1/FVC < 0.70), which is caused by a mixture of small airway obstruction and parenchymal destruction.
  • COPD was formerly subdivided into chronic bronchitis and emphysema. These terms are still widely used to describe patient findings and found as subclasses of COPD in outdated literature.


  • Sex: 3:2 male/female ratio [1][2]
  • The third most common cause of death worldwide [3]
  • Prevalence: 6% [4]


Epidemiological data refers to the US, unless otherwise specified.


  • Exogenous factors
    • Tobacco use (90% of cases)
      • Smoking is the major risk factor for COPD, but those who have quit ≥ 10 years ago are not at increased risk. [6]
      • Passive smoking
    • Exposure to air pollution or fine dusts
      • Nonorganic dust: such as industrial bronchitis in coal miners
      • Organic dust: ↑ incidence of COPD in areas where biomass fuel (e.g., wood, animal dung) is regularly burned indoors
    • Recurrent pulmonary infections and tuberculosis
    • Premature birth
  • Endogenous factors



Global initiative for chronic obstructive lung disease (GOLD) classifications

  • Classifies COPD according to the severity of airflow limitation (GOLD 1-4) and the ABCD assessment tool, which takes into account the modified British Medical Research Council (mMRC) dyspnea scale, COPD assessment test (CAT), and risk of exacerbation.
  • Previously, COPD was classified into chronic bronchitis and emphysema based on clinical findings. The use of these terms to classify types of COPD is now considered outdated because most individuals with COPD have a combination of both. However, these terms are still widely used to describe patient findings and found as subclasses of COPD in outdated literature.

Classification based on airflow limitation in patients with FEV1/FVC < 70%



FEV1 % of the predicted value
GOLD 1 (Class I)
  • Mild
  • ≥ 80%
GOLD 2 (Class II)
  • Moderate
  • 50% ≤ FEV1 < 80%
GOLD 3 (Class III)
  • Severe
  • 30% ≤ FEV1 < 50%
GOLD 4 (Class IV)
  • Very severe
  • < 30%

For GOLD categories according to the FEV1 %, remember that 30 + 50 = 80.

Classification using combined assessment tools

Patient group Degree of severity Exacerbations per year Symptoms mMRC Dyspnea Scale CAT score
  • ≤ 1 (with no hospital admission)
  • Mild symptoms
  • < 2
  • < 10
  • Severe symptoms
  • ≥ 2
  • ≥ 10
  • ≥ 2
  • ≥ 1 leading to hospital admission
  • Mild symptoms
  • < 2
  • < 10
  • Severe symptoms
  • ≥ 2
  • ≥ 10

Classification based on underlying pathophysiologic changes

Emphysema is divided into the following subtypes:



COPD is characterized by chronic airway inflammation and tissue destruction.


Clinical features

  • Symptoms are minimal or nonspecific until the disease reaches an advanced stage.
  • Common presenting findings:
  • In cases of advanced COPD and/or cor pulmonale:
  • According to their clinical appearance, patients with COPD are often categorized as either “Pink Puffer” or “Blue Bloater”.
Pink Puffer Blue Bloater
Main pathomechanism
Clinical features
  • Noncyanotic
  • Cachectic
  • Pursed-lip breathing
  • Mild cough
  • Slightly reduced
  • Markedly reduced
  • Normal (possibly in late hypercapnia)
  • Increased (early hypercapnia)
  • Patients with COPD in association with AATD
    • Age of onset is generally younger (< 60 years)
    • Also often have hepatic signs and symptoms (jaundice) related to hepatitis or cirrhosis

Nail clubbing is not a finding specific to COPD; its presence usually suggests comorbidities such as bronchiectasis, pulmonary fibrosis, or lung cancer.



Pulmonary function tests

To remember FEV1 for COPD patients, imagine a COP with low FEVer.

Always TaLCk FRanCly. It ReleaVes HIGH stress in COPD.

Blood gas analysis (BGA) and pulse oximetry


Other tests

Consider AATD in patients with COPD who are < 60 years of age, have no smoking history, and/or have basilar-predominant COPD.


Differential diagnoses

  • See “Differential Diagnosis” in Asthma.


The differential diagnoses listed here are not exhaustive.


General treatment

  • Cessation of tobacco use (single most effective step to slow the decline in lung function)
  • Vaccinations
  • Pulmonary rehabilitation (indicated in patients with GOLD B, C, and D): physiotherapy with breathing exercises
    • Pursed lip breathing: A breathing technique in which the patient breathes in through the nose and breathes out slowly through pursed lips. This technique increases airway pressure and prevents bronchial collapse during the last phase of expiration.
    • Physical activity helps maintain endurance and alleviate dyspnea.
  • Supportive treatment (e.g., postural drainage)
  • Vitamin D3 and calcium in cases of deficiency

Medical treatment according to GOLD

Medical treatment in COPD reduces the severity of symptoms, improves overall health status, and lowers the frequency and severity of exacerbation. The first-line treatment of COPD consists of bronchodilators, inhaled corticosteroids, and phosphodiesterase (PDE) type 4 inhibitors.

Initial treatment

Exacerbations per year Mild symptoms Severe symptoms
≤ 1 exacerbation

(Gold A)

(Gold B)

  • Any long-acting bronchodilator (LABA or LAMA)
  • If severe dyspnea: LABA and LAMA
≥ 2 exacerbation or ≥ 1 exacerbation requiring hospitalization

(Gold C)

  • LAMA

(Gold D)

  • LAMA or
  • If highly symptomatic (CAT > 20): LAMA and LABA or
  • If eosinophil count is ≥ 300/μl: LABA and ICS

For all groups: a SABA and/or SAMA can be added as needed

Follow-up treatment

Other treatment options



Chronic respiratory failure

  • Description:
  • Criteria:
    • Long-standing partial respiratory failure (pO2 at rest < 60 mm Hg)
    • Global respiratory insufficiency failure (pO2 changes at rest < 60 mm Hg and pCO2 > 45 mm Hg)
  • Long-term oxygen therapy (LTOT): 16 hours oxygen administration per day (minimum dosage) is associated with lower mortality rates.
    • Indication: patients with COPD GOLD D and severe respiratory insufficiency failure that exhibit long-standing pO2 < 55 mm Hg, despite administration of optimal medication
      • Oxygen administration is regulated in a way that the pO2 value rises and pCO2 drops to a level of 60–70 mm Hg. Hypercapnia would lead to respiratory acidosis and disorientation and should be prevented.
  • Portable respiration
    • Principle: A type of non-invasive respiration done overnight when the patient is asleep. This allows recovery of the respiratory muscles and in turn permits better respiratory function during the day.
  • Lung volume reduction surgery
  • Lung transplantation: It is considered the last resort in patients with emphysema associated with advanced COPD and severe diffusion dysfunction.

Other complications


We list the most important complications. The selection is not exhaustive.


  • 40–70% of all COPD patients survive the first 5 years after diagnosis
  • Survival rates vary significantly depending on the severity of the disease. [33]
  • Measures that improve survival
    • Cessation of tobacco use
    • Long-term supplemental O2 therapy is the only treatment that improves mortality.