DR DEAC PIMPs‎ > ‎

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.

Pictures


Comments