COPD

Definition

    • Progressive disease state characterised by airflow limitation that is not fully reversible.

    • Suspected in patients with a history of smoking, occupational and environmental risk factors, or a personal or family history of chronic lung disease.

    • Presents with progressive shortness of breath, wheeze, cough, and sputum production, including haemoptysis.

    • Diagnostic tests include PFTs, CXR, chest CT scan, oximetry, and ABG analysis.

    • Patients should be encouraged to stop smoking and be vaccinated against viral influenza and Streptococcus pneumoniae.

    • Treatment options include bronchodilators, inhaled corticosteroids, and systemic corticosteroids.

    • Long-term oxygen therapy improves survival in severe COPD.

Risk Factors

    • Cigarette smoking

      • Most important risk factor. It causes 90% of cases of COPD

      • Elicits an inflammatory response and causes cilia dysfunction and oxidative injury

    • Advanced age

      • May be related to a longer period of cigarette smoking as well as the normal age-related loss of FEV1

    • Genetic factors

      • Airway responsiveness to inhaled insults depends on genetic factors.

      • Alpha-1 antitrypsin deficiency causes panacinar emphysema in lower lobes in young people

    • White ancestry

      • COPD is more common in white people

    • Exposure to air pollution or occupational exposure

      • Chronic exposure to dust, traffic exhaust fumes, and sulphur dioxide increases risk of COPD.

    • Developmentally abnormal lung

      • Frequent childhood infection may cause scarring of lungs, decrease elasticity, and increase risk for COPD

    • Male gender

      • COPD is more common in men, but that is probably secondary to more smokers being male

      • But there is a suggestion that women may be more susceptible than men to the effects of tobacco smoke

    • Low socio-economic status

      • The risk for developing COPD is increased in people with lower socio-economic status

      • However, this may reflect exposure to cigarette smoke, pollutants, or other factors.

Differential diagnosis

Epidemiology

    • COPD is more common in older people, especially those >65 years

    • In 2002, the WHO stated that COPD had become the fifth leading cause of death and disability worldwide

    • Predicted that it would be the third most common by 2030. [4]

    • Worldwide population prevalence of COPD for stages II or higher as equivalent to 10.1 ± 4.8% overall

      • 11.8 ± 7.9% for men and 8.5 ± 5.8% for women. [5]

    • It is the fourth leading cause of death in the US

    • COPD affects 1% to 3% of white women and 4% to 6% of white men in the US

    • COPD prevalence estimated to be 2% in men and 1% in women in the UK in the 1990s. [7]

Aetiology

    • Tobacco smoking is by far the main risk factor for COPD

      • It is responsible for 90% of COPD cases

      • Exerts its effect by causing an inflammatory response, cilia dysfunction, and oxidative injury

    • Air pollution and occupational exposure are other common aetiologies

    • Oxidative stress and an imbalance in proteinases and antiproteinases are also important factors

      • Especially in patients with alpha-1 antitrypsin deficiency

Clinical features

    • Key features

      • Presence of risk factors (e.g., smoking)

      • Cough

      • Shortness of breath

    • Other diagnostic factors

      • Barrel chest (common)

      • Hyper-resonance (common)

      • Distant breath sounds (common)

      • Poor air movement (common)

      • Wheezing (common)

      • Coarse crackles (common)

      • Hypoxia (common)

      • Tachypnoea (uncommon)

      • Asterixis (uncommon)

      • Distended neck veins (uncommon)

      • Lower-extremity swelling (uncommon)

      • Fatigue (uncommon)

      • Headache (uncommon)

      • Cyanosis (uncommon)

      • Loud P2 (uncommon)

      • Hepatojugular reflux (uncommon)

      • Hepatosplenomegaly (uncommon)

      • Clubbing (uncommon)

Pathophysiology

    • The hallmark of COPD is chronic inflammation

      • Affects central airways, peripheral airways, lung parenchyma and alveoli, and pulmonary vasculature.

    • The main components of these changes are:

      • narrowing and remodelling of airways

      • increased number of goblet cells

      • enlargement of mucus-secreting glands of the central airways

      • subsequent vascular bed changes leading to pulmonary hypertension

    • This is thought to lead to the pathological changes that define the clinical presentation.

    • Activated macrophages, neutrophils, and leukocytes are the core cells in this process

      • In contrast to asthma, eosinophils play no role in COPD, except for occasional acute exacerbations.

    • In emphysema, the final outcome is elastin breakdown and subsequent loss of alveolar integrity. [8]

    • In chronic bronchitis changes lead to ciliary dysfunction and increased goblet cell size and number

      • Leads to the excessive mucus secretion

      • Responsible for decreased airflow, hypersecretion, and chronic cough

    • Increased airway resistance is the physiological definition of COPD

      • Decreased elastic recoil, fibrotic changes in lung parenchyma, and luminal obstruction of airways by secretions all contribute to increased airways resistance

    • Expiratory flow limitation promotes hyperinflation.

    • This finding, in addition to destruction of lung parenchyma, predisposes COPD patients to hypoxia

    • Progressive hypoxia causes vascular smooth muscle thickening with subsequent pulmonary hypertension

Investigations

    • Spirometry

      • FEV1/FVC ratio <70% with no evidence of reversibility with bronchodilator

      • Total absence of reversibility is neither required nor the most typical result

    • Pulse oximetry

      • Low oxygen saturation

    • ABG

      • PaCO2 >50 mmHg and/or PaO2 of <60 mmHg suggests respiratory insufficiency

    • CXR

      • Hyperinflation

    • FBC

      • Raised haematocrit

      • Possible increased WBC count

    • ECG

      • Signs of right ventricular hypertrophy, arrhythmia, ischaemia

    • Sputum culture

      • Infecting organism

    • PFTs

      • Obstructive pattern

      • Decreased DLCO

    • Chest CT scan

      • Hyperinflation

    • Aalpha-1 antitrypsin

      • Level should be normal in patients with COPD

    • Exercise testing

      • Poor exercise performance or exertional hypoxaemia is suggestive of advanced disease

    • Ssleep study

      • Elevated apnoea-hypopnoea index and/or nocturnal hypoxaemia

    • Respiratory muscle function

      • Reduced maximal inspiratory pressure

Management

    • Stage I disease

      • Short-acting bronchodilator as required

      • Patient education and vaccination

      • Smoking cessation

    • Stage II disease

      • Long-acting bronchodilator

      • Short-acting bronchodilator as required

      • Patient education and vaccination

      • Smoking cessation

      • Pulmonary rehabilitation

    • Stage III disease

      • Long-acting bronchodilator

      • Short-acting bronchodilator as required

      • Patient education and vaccination

      • Smoking cessation

      • Inhaled corticosteroid

      • Theophylline

      • Pulmonary rehabilitation

    • Stage IV disease

      • Long-acting bronchodilator

      • Short-acting bronchodilator as required

      • Patient education and vaccination

      • Smoking cessation

      • Inhaled corticosteroid

      • Theophylline

      • Supplemental oxygen

      • Pulmonary rehabilitation

      • Surgical interventions

Prognosis

    • COPD is a disease with an indeterminate course and variable prognosis

    • Prognosis depends on a number of factors

      • Genetic predisposition

      • Environmental exposures

      • Comorbidities

      • Acute exacerbations.

    • Long-term survival is primarily influenced by the severity of COPD and the presence of comorbid conditions

    • An FEV1 of less than 35% of predicted means very severe disease

      • More than half of patients with very severe disease may not be expected to survive for 4 years. [1]

    • In addition to the FEV1, other factors that predict prognosis are:

      • Weight (very low weight is a negative prognostic factor)

      • Distance walked in 6 minutes

      • Degree of shortness of breath with activities

    • These factors, known as the BODE index, provide information on prognosis for 1-year, 2-year, and 4-year survival. [77]

    • Among different therapeutic modalities in COPD, the only 2 factors that improve survival are smoking cessation and oxygen supplementation.

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