Chronic obstructive pulmonary disease (COPD)

Chronic obstructive pulmonary disease (COPD) is characterised by airflow obstruction that is not fully reversible. The airflow limitation is usually progressive and is associated with an abnormal inflammatory response of the lungs to noxious particles or gases.1 The airflow obstruction is due to a combination of airway and parenchymal damage. COPD is now the preferred term for patients with airflow obstruction who were previously diagnosed as having chronic bronchitis or emphysema.2

Airflow obstruction is defined as a reduced post-bronchodilator FEV1/FVC ratio (where FEV1 is forced expiratory volume in 1 second and FVC is forced vital capacity), such that FEV1/FVC is less than 0.7. If FEV1 is 80% or more of predicted normal, a diagnosis of COPD should only be made in the presence of respiratory symptoms, e.g. breathlessness or cough.2

The respiratory drive is normally largely initiated by PaCO2 but in COPD hypoxia can be a strong driving force, which can therefore be reduced if the hypoxia is corrected. Patients with COPD have traditionally been divided into pink puffers and blue bloaters based on their physiological response to abnormal blood gases.

  • Pink puffers work hard to maintain a normal pO2. They tend to have a barrel-shaped, hyperinflated chest and breath through pursed lips.
  • Blue bloaters are blue because of hypoxia and polycythaemia. They are often obese and have water retention. The blue bloaters are dependent upon hypoxia for their respiratory drive and to give oxygen and deprive them of this will lead to signficant hypercapnia and acid base imbalance.

However this classification is of little clinical value as patients tend not to be clearly defined into these two categories.

Epidemiology2

The damage to the lungs is the result of chronic inflammation, which is usually the result of tobacco smoke. Other factors, particularly occupational exposures, may also contribute to the development of COPD.

  • An estimated three million people are affected by COPD in the UK. About 900,000 have been diagnosed with COPD and an estimated two million people have COPD which remains undiagnosed.
  • The rate of COPD in the population is estimated at between 2% and 4%. The diagnosed prevalence of COPD is 1.5%. The prevalence increases with age, with an estimated prevalence of 10% in men older than 75.3
  • Most patients are not diagnosed until they are in their fifties. COPD is closely associated with levels of deprivation - rates of COPD are higher in more deprived communities.

Presentation

See also separate articles Respiratory System - History and Exam and Diagnosing COPD.

  • A diagnosis of COPD should be considered in patients over the age of 35 who have a risk factor (generally smoking) and who present with exertional breathlessness, chronic cough, regular sputum production, frequent winter 'bronchitis' or wheeze.2
  • COPD may also cause abnormal weight loss, effort intolerance and ankle oedema.

Smoking cessation: an up-to-date smoking history, including pack years smoked (number of cigarettes smoked per day, divided by 20, multiplied by the number of years smoked) should be documented for everyone with COPD. An assessment of their 'readiness to change' should also be made.4

Signs

  • Respiratory distress: tachypnoea, breathlessness on exertion, increased use of accessory muscles of respiration, pursed lip breathing.
  • Abnormal posture: patients may lean forward and rest their arms on the table to ease breathing.
  • Drowsiness, flapping tremor and mental confusion (these are features of elevated carbon dioxide levels).
  • Other signs include being underweight, ankle oedema, cyanosis, hyperinflation of the chest, downward displacement of the liver, relatively quiet vesicular breath sounds, wheezing, prolonged forced expiratory time.

Disease severity and staging2

  • Disability in COPD can be poorly reflected in the FEV1. A more comprehensive assessment also includes:
    • Degree of airflow obstruction and disability.
    • Frequency of exacerbations.
    • Prognostic factors such as breathlessness (Medical Research Council (MRC) dyspnoea scale), carbon monoxide lung transfer factor (TLCO), health status, exercise capacity, body mass index (BMI), partial pressure of oxygen in arterial blood (PaO2) and presence of cor pulmonale.
  • Investigate symptoms that seem disproportionate to the spirometric impairment using a CT scan or TLCO testing.
  • The BODE index (= BMI, airflow Obstruction, Dyspnoea and Exercise capacity index) should be used to assess the prognosis when the component information is available: measurement of the BODE index includes measurement of BMI, FEV1 as a percentage of predicted, dyspnoea (modified MRC score) and exercise tolerance (6-minute walking distance).
  • Assess the severity of airflow obstruction by FEV1 as a percentage of predicted:2
    • Stage 1 - mild: 80% or above (symptoms should be present to diagnose COPD in people with mild airflow obstruction).
    • Stage 2 - moderate: 50-79%.
    • Stage 3 - severe: 30-49%.
    • Stage 4 - very severe: below 30% (or FEV1 less than 50% but with respiratory failure).

The GOLD (= Global Initiative on Obstructive Lung Disease) classification of severity is also still used:1

  • Stage 0: at risk; chronic cough and sputum production. Spirometry is normal.
  • Stage I: mild COPD; mild airflow limitation (FEV1/FVC less than 70% but FEV1 80% or more than predicted); usually, but not always chronic cough and sputum production.
  • Stage II: moderate COPD; worsening airflow limitation (FEV1 50-79% predicted) and usually progression of symptoms, with shortness of breath, especially on exertion.
  • Stage III: severe COPD; further worsening of airflow limitation (FEV1 30-50% predicted), increased shortness of breath, and repeated exacerbations.
  • Stage IV: very severe COPD; severe airflow limitation (FEV1 less than 30% predicted) or the presence of chronic respiratory failure.

Differential diagnosis

Investigations2

  • There is no single diagnostic test for COPD. The diagnosis is therefore based on a combination of history, examination and confirmation of the presence of airflow obstruction, using spirometry.
  • The presence of airflow obstruction should be confirmed by performing post-bronchodilator spirometry. Spirometry is considered the gold standard test for diagnosing COPD. See also separate article Spirometry Calculator.
  • Initial evaluation should also include CXR to exclude other diagnoses (investigate abnormalities using a CT scan), FBC (to identify anaemia or polycythaemia) and BMI calculation.
  • In younger patients, or in those who are not exposed to cigarette smoke or other factors known to be associated with COPD, consider a genetic cause such as alpha-1-antitrypsin (A1AT) deficiency.

Management

Referral2

Referral for advice, specialist investigations or treatment may be appropriate at any stage of the disease, not just for people who are severely disabled. Possible reasons for referral include:

  • Diagnostic uncertainty.
  • Suspected severe COPD.
  • The individual requests a second opinion.
  • Onset of cor pulmonale.
  • Assessment for oxygen therapy, long-term nebuliser therapy or oral corticosteroid therapy.
  • Bullous lung disease.
  • Rapid decline in FEV1.
  • Assessment for pulmonary rehabilitation.
  • Assessment for lung volume reduction surgery or lung transplantation.
  • Dysfunctional breathing.
  • Onset of symptoms at age under 40 years or a family history of A1AT deficiency.
  • Symptoms disproportionate to lung function deficit.
  • Frequent infections.
  • Haemoptysis.

Indications for surgery

  • Refer patients who are breathless, have a single large bulla on a CT scan and an FEV1 less than 50% predicted for consideration of bullectomy.
  • Refer people with severe COPD for consideration of lung volume reduction surgery if they remain breathless with marked restrictions of their activities of daily living, despite maximal medical therapy (including rehabilitation), and meet all of the following:
    • FEV1 greater than 20% predicted.
    • PaCO2 less than 7.3 kPa.
    • Upper lobe predominant emphysema.
    • Carbon monoxide lung transfer factor (TLCO) greater than 20% predicted.
  • Lung transplantation:
    • Consider referring people with severe COPD for assessment for lung transplantation if they remain breathless with marked restrictions of their activities of daily living despite maximal medical therapy.
    • Considerations include age, FEV1, PaCO2, homogeneously distributed emphysema on CT scan, elevated pulmonary artery pressures with progressive deterioration, comorbidities and local surgical protocols.

Complications

Prognosis2

The BODE index has been shown in a number of studies to be a better predictor of exacerbations, hospital admissions and mortality than using only FEV1.

  • Chronic obstructive pulmonary disease (COPD) is progressive and patients deteriorate but the natural history of the disease varies in different people.
  • COPD is the fifth leading cause of death in the UK. More than 90% of COPD-related deaths occur in the over-65 age group. COPD is an important comorbidity in those dying from other smoking-related diseases, especially ischaemic heart disease and lung cancer.
  • Five-year survival from diagnosis is 78% in men and 72% in women with clinically mild disease (defined as not requiring continuous drug therapy), but falls to 30% in men and 24% in women with severe disease defined as requiring oxygen or nebulised therapy.
  • The mean age of death of patients with severe COPD is 74.2 years compared with 77.2 years in patients with mild disease and 78.3 years in individuals who do not have COPD.
  • In patients who stop being exposed to cigarette smoke and other noxious substances the disease may continue to progress but the rate of declining lung function may slowed.1
  • Repeated exacerbations lead to irreversible decline in lung function and efforts should therefore be made to reduce exacerbations.

Prevention

  • Smoking cessation and restriction of other potential risk factors, e.g. occupational dusts and chemicals.
  • Reduce the risk of exacerbations, e.g. influenza and pneumococcal immunisation.

Document references

  1. Global Initiative for Chronic Obstructive Lung Disease (GOLD); Guidelines & Resources page
  2. Chronic obstructive pulmonary disease, NICE Clinical Guideline (June 2010); Management of chronic obstructive pulmonary disease in adults in primary and secondary care (partial update). This guideline partially updates and replaces NICE clinical guideline 12
  3. Britton M; The burden of COPD in the U.K.: results from the Confronting COPD survey.; Respir Med. 2003 Mar;97 Suppl C:S71-9. [abstract]
  4. Prochaska JO, DiClemente CC, Norcross JC; In search of how people change. Applications to addictive behaviors. Am Psychol. 1992 Sep;47(9):1102-14. [abstract]

Internet and further reading

Acknowledgements

EMIS is grateful to Dr Colin Tidy for writing this article. The final copy has passed scrutiny by the independent Mentor GP reviewing team. ©EMIS 2010.

Document ID: 1615

Document Version: 23

Document Reference: bgp625

Last Updated: 5 Nov 2010