• Clinical science

Chronic obstructive pulmonary disease

Summary

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, 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).

Definition

  • COPD is 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 [1]
  • 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. [2]

Epidemiology

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Exogenous factors

  • Tobacco use (90% of cases) [2]
    • 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 [7]
    • Nonorganic dust: such as industrial bronchitis in coal miners [8]
    • Organic dust: incidence of COPD in areas where biomass fuel (e.g., wood, animal dung) is regularly burned indoors

Endogenous factors

Classification

Global initiative for chronic obstructive lung disease (GOLD) classifications [11]

  • GOLD 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% [1]

GOLD uses FEV1/FVC (Tiffeneau-Pinelli index) to classify COPD.

Category

Symptoms

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
A
  • ≤ 1 (with no hospital admission)
  • Mild symptoms
  • < 2
  • < 10
B
  • Severe symptoms
  • ≥ 2
  • ≥ 10
C
  • ≥ 2
  • ≥ 1 leading to hospital admission
  • Mild symptoms
  • < 2
  • < 10
D
  • Severe symptoms
  • ≥ 2
  • ≥ 10

Classification based on underlying morphological changes

Emphysema is divided into the following subtypes: [12]

To remember that centriacinar emphysema is associated with smoking and that it primarily involves the upper lobes of the lungs, think of: Smoke rising up.

Pathophysiology

COPD is characterized by chronic airway inflammation and tissue destruction. [2][13]

Chronic inflammation

It results from significant exposure to noxious stimuli, increased oxidative stress (most commonly due to cigarette smoke) as well as by increased release of reactive oxygen species by inflammatory cells.

Tissue destruction [15]

Clinical features

Symptoms are minimal or nonspecific until the disease reaches an advanced stage.

Presenting findings [2]

  • Chronic cough with expectoration (expectoration typically occurs in the morning)
  • Dyspnea and tachypnea
    • Initial stages: only on exertion
    • Advanced stages: continuously
  • Pursed lip breathing
    • The patient breathes in through the nose and breathes out slowly through pursed lips.
    • This style of breathing increases airway pressure and prevents bronchial collapse during the last phase of expiration.
    • More commonly seen in patients with emphysema
  • Prolonged expiratory phase, end-expiratory wheezing, crackles, muffled breath sounds, and/or coarse rhonchi on auscultation
  • Cyanosis due to hypoxemia
  • Tachycardia

Features of advanced COPD [16]

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

Pink puffer and blue bloater [16]

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
PaO2
  • Slightly reduced
  • Markedly reduced
PaCO2
  • Normal (possibly in late hypercapnia)
  • Increased (early hypercapnia)

Features of COPD due to AATD

  • Age of onset is generally younger (< 60 years)
  • Also, often have hepatic signs and symptoms (jaundice) related to hepatitis or cirrhosis

Diagnostics

Pulmonary function test (PFT) [2]

Spirometry and/or body plethysmography

Postbronchodilator test

  • Objective: assesses reversibility of bronchoconstriction
  • Procedure
    1. Spirometry to establish a baseline
    2. Inhalation (e.g., salbutamol)
    3. Perform spirometry again after ∼10–15 min.
  • Results: FEV1/FVC < 0.7 is diagnostic of COPD (in patients with typical clinical features and exposure to noxious stimuli).
    • Delta FEV1 < 12% (irreversible bronchoconstriction): COPD is more likely than asthma.
    • Delta FEV1 > 12% (reversible bronchoconstriction): Asthma is more likely than COPD.
    • If spirometry is normal, COPD can be excluded.

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

Blood gas analysis and pulse oximetry

  • Pulse oximetry: assesses O2 saturation
  • ABG: only indicated when O2 is < 92% or if the patient is severely ill (e.g., altered mental status, acute exacerbation)
    • Hypoxemia and hypercapnia are expected findings in patients with acute or chronic respiratory acidosis.
      • Decreased pO2: partial respiratory failure
      • Decreased pO2 and increased pCO2: global respiratory failure
      • Many individuals with severe COPD have chronic hypercapnia due to CO2 trapping from hyperinflation and progressive loss of pulmonary elasticity.

Imaging

Other tests

Consider AATD in patients with COPD who are < 60 years of age, have no smoking history, and/or have basilar-predominant COPD. However, testing for AATD is recommended for all new patients with COPD.

Differential diagnoses

The differential diagnoses listed here are not exhaustive.

Treatment

General treatment [1][2]

Medical treatment according to GOLD [1]

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.

Patient group Exacerbations per year Symptoms Initial treatment Subsequent escalation
A
  • ≤ 1 (with no hospital admission)
  • Mild symptoms
  • Continue or try alternative class of bronchodilator
B
  • Severe symptoms
  • Any long-acting bronchodilator (LABA or LAMA)
C
  • ≥ 2
  • ≥ 1 leading to hospital admission
  • Mild symptoms
  • LAMA
  • LAMA and LABA (preferred)
  • LABA and ICS
D
  • Severe symptoms
  • LAMA
  • If highly symptomatic (CAT > 20): LAMA and LABA (preferred)
  • Consider LABA and ICS in patients with high eosinophil count

Other treatment options [1]

Complications

Chronic respiratory failure [2]

  • Description: occurs in the advanced stages of COPD due to progressive emphysematous changes and loss of diffusion surface area
  • 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)
  • Management: depends on the severity and etiology [1]
    • 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. [21]
    • Portable respiration
      • Principle: a type of non-invasive respiration done overnight when the patient is asleep
      • Goal: This allows recovery of the respiratory muscles and in turn permits better respiratory function during the day.
    • Lung volume reduction surgery
    • Lung transplantation: considered the last resort in patients with emphysema associated with advanced COPD and severe diffusion dysfunction

Other complications [2]

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

Prognosis

  • 40–70% of all COPD patients survive the first 5 years after diagnosis. [22]
  • Survival rates vary significantly depending on the severity of the disease. [22]
  • Measures that improve survival
  • COPD is the third most common cause of death worldwide. [23]
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last updated 11/20/2020
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