Chronic Obstructive Pulmonary Disease (COPD)

Introduction

Chronic obstructive pulmonary disease (COPD) is a lung condition characterised by consistent respiratory symptoms and airflow obstruction. It comprises emphysema, chronic bronchitis, and small airway fibrosis. Chronic bronchitis is defined as a persistent cough for at least three months in two consecutive years. COPD affects approximately three million people in the UK and causes 30,000 deaths yearly. Additionally, it results in 1.4 million GP appointments annually and is the second-leading cause of emergency admissions in the UK. COPD is a common and important topic that all medical disciplines must be familiar with.

Risk factors

• Tobacco smoking: associated with 80% of COPD cases
• Indoor air pollution: this usually happens in the developing world, where biomass is burned inside homes for cooking and heating
• Alpha-1 antitrypsin deficiency: an autosomal dominant condition which presents in younger patients (aged 20-40). Alpha-1 antitrypsin is a protease inhibitor that stops neutrophil elastase from destroying alveolar structures. A deficiency in alpha-1 antitrypsin leads to an increased destruction of alveolar structures, resulting in early-onset emphysema. Some cases of alpha-1 antitrypsin deficiency involve a reduced secretion of the inhibitor in the liver, resulting in accumulation of it in the liver and therefore cirrhosis.

Clinical features

History

Presenting complaint

COPD patients show progressive dyspnoea and chronic productive cough.

History of presenting complaint

• Dyspnoea: initially experienced during exertion but may become resting dyspnoea over the course of the condition (months to years). Dyspnoea is evaluated using the Medical Research Council (MRC) dyspnoea scale (Table 1)
• Chronic productive cough: usually colourless sputum which may become green during lower respiratory tract infections (LRTIs)
• Recurrent LRTIs
• Fatigue
• Headache (due to CO₂ retention)

Table 1. MRC Dyspnoea Scale. Used with the permission of the MRC

GradeLevel of Activity   1 Breathless during strenuous exercise only   2 Breathless when hurrying or walking up a slight incline   3 Walks slower than people of the same age due to dyspnoea, or needs to pause for breath when walking at own pace   4 Pauses for breath after walking 100m/a few minutes on the level   5 Too breathless to leave the house, or breathless when dressing  

It is important to assess the impact of the patient's COPD on their wellbeing and daily life, using the COPD Assessment Test (CAT) (Table 2).

Table 2. The CAT.

Chronic Obstructive Pulmonary Disease Assessment

Scores range from 0-40; higher scores indicate a greater impact of COPD on the patient's daily life.

SCOREI never cough1 2 3 4 5I cough all the time I have no phlegm in my chest at all 1 2 3 4 5My chest is full of phlegm My chest does not feel tight at all 1 2 3 4 5My chest feels very tight When I walk up a hill or flight of stairs, I am not out of breath 1 2 3 4 5When I walk up a hill or flight of stairs, I am completely out of breath I am not limited to doing any activities at home 1 2 3 4 5I am completely limited to doing any activities at home I am confident leaving my home despite my lung condition 1 2 3 4 5I am not confident leaving my home at all despite my lung condition I sleep soundly 1 2 3 4 5I do not sleep soundly because of my lung condition I have lots of energy 1 2 3 4 5I have no energy at all  TOTAL SCORE /40

Past Medical History

• Previous exacerbations or hospitalizations
• Medical comorbidities, including lung disease (such as asthma)
• Psychiatric comorbidities, including depression and anxiety
• Previous operations

Medication/Allergies

• Regular medications (and any recent changes) *ACE-inhibitors can cause a dry cough
• Over-the-counter medications
• Allergies

Family History

• Lung disease
• Liver disease (may suggest alpha-1 antitrypsin deficiency)

Social History

• Smoking history: quantify in pack-years (1 pack-year = smoking 20 cigarettes a day for a year)
• Alcohol history
• Recreational drug use
• Occupation: may be exposed to indoor air pollution

Examination

A full respiratory examination should be performed in suspected cases of COPD. See the guide here.

Most Common Findings

• Tachypnoea: due to an increased neural respiratory drive to breathe
• Wheeze on auscultation: due to inflammatory airway edema and mucous obstructing the airway
• Pursed lips breathing: to increase airway resistance and therefore reduce expiratory flow limitation

Less Common Findings

• Barrel chest: due to gas trapping
• Peripheral cyanosis
• Cor pulmonale (signs of right heart failure, such as peripheral edema and hepatomegaly): due to pulmonary hypertension, which results from chronic hypoxic pulmonary vasoconstriction
• CO₂ retention flap: while the exact mechanism is unknown, some hypothesise that it is due to abnormal function of the diencephalon (which acts as a relay centre for sensory and motor impulses)

Barrel Chest and Peripheral Cyanosis

Dyspnoea (shortness of breath) and productive cough have important differential diagnoses. Table 3 outlines the differential diagnoses and the features which differentiate them from Chronic Obstructive Pulmonary Disease (COPD).

Table 3. Differential Diagnoses of COPD

Differential diagnosisFeatures differentiating from COPD   Asthma  

• Diurnal variation in symptoms and peak flow
• History of atopy
• Eosinophilia (blood and sputum)
• Lung function tests: bronchodilator reversibility

*Note that COPD and asthma can co-exist

   Bronchiectasis  

• Expectorate larger volumes of sputum
• More frequent lower respiratory tract infections, often starting in childhood
• High-resolution chest CT: bronchial dilation

   Congestive cardiac failure  

• Orthopnoea
• Paroxysmal nocturnal dyspnoea
• History of cardiovascular disease
• Fine basal inspiratory crepitations
• Bloods: elevated BNP
• Echocardiogram: reduced ejection fraction

   Lung cancer  

• Weight loss
• Haemoptysis
• Chest X-ray and bronchoscopy: the presence of tumour

   Tuberculosis  

• Drenching night sweats
• Weight loss
• Positive sputum culture and microscopy

Investigations

Bedside Investigations

Spirometry

• Typical finding in COPD: FEV1/FVC < 70%
• FEV1 is also used to classify the severity of COPD (Table 4)

Table 4. Severity of COPD according to FEV1

SeverityFEV1 (L) ⁹   Mild >= 80% predicted   Moderate 50-79% predicted   Severe 30-49% predicted   Very severe < 30% predicted  

Severity Grading of COPD

Severity of COPD

FEV1Mild>80%Moderate50-80%Severe30-50%Very Severe<30%

Pulse Oximetry

• Aim for an SpO₂ of 88-92%
• Avoid excessive amounts of O₂:
• O₂ displaces CO₂ in hemoglobin, resulting in increased CO₂ in the blood
• When COPD is present, increased CO₂ cannot be removed due to alveolar ventilation failure, leading to hypercapnic respiratory failure

Other Investigations

• Sputum Culture: assists with targeted antibiotic therapy during COPD exacerbations
• ECG: detects cor pulmonale (such as peaked p-waves and right axis deviation) (Figure 3)

Laboratory Investigations

• Baseline Blood Tests: FBC, U&E, LFTs, CRP
• Arterial Blood Gas (ABG):
• When stable: when PaCO₂ >6.0 and bicarbonate >30, patient is known as a “CO₂ retainer”
• During exacerbations: check for respiratory acidosis (PaCO₂ >6.0 and pH <7.35)

Imaging

• Chest X-Ray: detect hyperinflation¹⁰
• More than 6 anterior ribs or 10 posterior ribs visible in the mid-clavicular line
• Flattened diaphragm
• Hyperlucent lungs

Chronic Obstructive Pulmonary Disease (COPD)

COPD is a long-term, progressive condition characterised by airflow limitation. It is an umbrella term for a range of conditions, including emphysema and chronic bronchitis. While the cause of COPD is most commonly smoking, other factors can contribute to its development, such as environmental exposure and genetics. It is often under-diagnosed and can lead to disability and reduced life expectancy if left untreated.

Pulmonary Function Tests

Pulmonary function tests are used to diagnose COPD and assess its severity. They include spirometry, reversibility tests and diffusion capacity tests.

Spirometry

• Measures Forced Expiratory Volume in 1 second (FEV1) and Forced Vital Capacity (FVC)
• Uses the FEV1/FVC ratio to differentiate obstructive and restrictive lung diseases
• May also assess reversibility if bronchodilator is given

Reversibility tests

• Uses FEV1 before and after a bronchodilator to assess reversibility
• A 15% improvement in FEV1 suggests bronchial hyperreactivity (asthma) rather than COPD

Diffusion capacity tests

• Measures the capacity of the lungs to transfer oxygen to the bloodstream
• Reduced in both COPD and restrictive lung diseases

Management (long-term)

For further information on the management of acute exacerbations of COPD.

Conservative management

• Smoking cessation
• Pulmonary rehabilitation
• Annual influenza vaccine and one-off pneumococcal vaccine
• Personalised self-management plan

Medical management

Inhalers

Medical management of COPD is largely administered through inhalers, with a step-up process as needed (Figure 5).

Note that some clinicians prefer to use the international GOLD guidelines for the management of COPD, so please ensure that you know which guidelines your medical school will use for your examinations.

Long-term oxygen therapy

• Indications (one of the following):
• SpO₂ <88%
• PaO₂ <7.3 kPa when awake, or <6.7 kPa when asleep

COPD is a combination of emphysema, chronic bronchitis and small airway fibrosis. Risk factors include smoking and inhaling pollutants. It is characterized by progressive dyspnea and a productive cough. Diagnosis is based on clinical features and FEV1/FVC having a value of < 70%.  

Management

Management includes conservative measures such as smoking cessation and inhaled bronchodilators. In cases of severe COPD that does not respond to optimal medical management, lung volume-reduction surgery or lung transplantation may be necessary.

Complications

 
• Hypercapnic respiratory failure (PaO2 < 8.0 and PaCO2 > 6.0)
 
• Secondary polycythaemia (raised haemoglobin): due to chronic hypoxaemia
 
• Cor pulmonale: right heart failure due to pulmonary hypertension caused by chronic hypoxic pulmonary vasoconstriction
 
• Bronchiectasis due to chronic and repeated infections
 
• Anxiety and depression
 
• Osteoporosis due to chronic steroid use, smoking, lack of bone-strengthening exercise and vitamin D deficiency
 
• Sleep disturbance

Key Points

 
• COPD is a triad of emphysema, chronic bronchitis and small airway fibrosis.
 
• The main risk factors are tobacco smoking and inhaled pollutants.
 
• COPD presents with progressive dyspnoea and productive cough.
 
• Diagnosis is based on clinical features + spirometry (FEV1/FVC <70%).
 
• Management consists of conservative measures (such as smoking cessation) and inhaled bronchodilators.
 
• Complications include respiratory failure and cor pulmonale.

References

 
1. National Institute for Health and Care Excellence. Chronic Obstructive Pulmonary Disease in Over 16s: Diagnosis and Management. Published in 2018. Available from: LINK
 
2. Health and Safety Executive. Chronic Obstructive Pulmonary Disease (COPD) Statistics in Great Britain. Published in 2019. Available from: LINK
 
3. National Institute for Health and Care Excellence. Quality Standards and Indicators: COPD. Published in 2015. Available from: LINK
 
4. Rabe KF and Watz H. Chronic Obstructive Pulmonary Disease. Published in 2017. Available from: LINK
 
5. Kalfopoulos M et al. Pathophysiology of Alpha-1 Antitrypsin Lung Disease. Methods in Molecular Biology. Published in 2017. Available from: LINK
 
6. Medical Research Council. MRC Dyspnoea Scale. Published in 1960. Available from: LINK
 
7. Jones PW et al. Development and First Validation of the COPD Assessment Test. European Respiratory Journal. Published in 2009. Available from: LINK
 
8. Mendizabal M and Silva MO. Images in Clinical Medicine: Asterixis. Published in 2010. Available from: LINK
 
9. Global Initiative for Chronic Obstructive Lung Disease. Global Strategy for the Diagnosis, Management and Prevention of COPD. Published in 2020. Available from: LINK
 
10. Bickle I. Hyperinflated Lungs. Published in 2018. Available from: LINK
 
11. National Institute for Health and Care Excellence.