Chronic Obstructive Pulmonary Disease (COPD)

Definition: Chronic obstructive pulmonary disease is defined as a condition of restricted airflow which is not fully reversible. It is often a progressive disease caused by abnormal inflammatory responses to obnoxious substances. 

Demographics: COPD is a common condition, The prevalence of COPD increases with age, with most patients being diagnosed at around the age of 50. 

Aeitiology and pathophysiology: 

Airway obstruction in COPD is caused by; 

1) increase in mucus secretion, leading to obstruction. 

many COPD patients show increased number of goblet cells in their airways, which block airways. 

2) inflammation and scarring to the airways, leading to narrowed airways. 

Inflammatory cells infiltrate the bronchi and bronchiole walls. The inflammation causes scarring and thickening of walls which cause small airways to narrow. Initially, inflammation is reversible, but this become irreversible with continued smoking. As the disease progresses, the bronchial walls become fibroses and squamous cells replace the columnar epithelial cells. 

3) and damage to the distal lung tissue leading to loss of elasticity of airways and collapse. 

This is also known as emphysema, and may affect the terminal bronchioles (centri-acinar emphysema) which usually only causes symptoms when severe, or affect both the terminal bronchioles and the alveoli, which causes severe airflow problems. The loss of elasticity in airways lead to rapid closure of small airways on expiration, which are more prone to being blocked by mucus and requires more effort on inspiration to open up, and the loss of alveolar surface leads to decreased gas transfer. 

The greatest risk factor for COPD is smoking. In the developed world, 90% of COPD cases are caused by cigarette smoking. Other risk factors include smoke from biomass fuels in poorly ventilated areas, and occupational exposure. a1- antitrypsin deficiency may also causes COPD. Climate and air pollution may also have a small role. 

Presentation: 

Patients typically present with a long history of productive cough with white or clear sputum, wheezing and breathlessness, usually with a history of smoking, and smoker's cough. COPD patients may present with recurring infections. Patients with advanced COPD may resent with severe breathlessness even with mild activities. 

Examination: 

With mild disease, sometimes only a quiet wheeze can be heard.

In severe disease, patients are often tachypnoeic, with prolonged expiration, and may use their accessory muscles. They may have intercostal in drawing during inspiration and purse their lips on expiration. Patients often have poor chest expansion, with hyper inflated chests, which may be hyper resonant on percussion. Ausculation may show reduced breath sounds or a wheeze. 

Depending on whether or not the patient has retained their responsiveness to CO2, patients may be described as 'pink puffers' or 'blue bloaters'. 

Patients who maintain a respiratory drive due to CO2 tend to be breathless. 

On the other hand, patients who loose their respiratory drive from CO2 may become cyanosed, but will not appear breathless. Hypercapnia may causes peripheral vasodilatation, a flapping tremor, and a bounding pulse. Hypercapnia can also cause confusion and drowsiness. 

COPD can also cause a raised JVP, ankle oedema and weight loss. 

This image shows someone who is a 'pink puffer' and a person who is a 'blue bloater'

Differential diagnoses: 

Asthma - usually reversible with bronchodialators. 

Congestive heart failure

Bronchiectasis

Lung cancer

Obliterative bronchiolitis

Bronchopulmonary dysplasia

Investigations: 

COPD is often diagnosed clinically, often from a history of breathlessness and sputum production in a long term smoker. A family history of COPD may indicate a1 antitrypsin deficiency. 

Lung function tests through peak flow, and spirometry can confirm obstructive disease. Usually a FEV1:FVC less than 0.7 of predicted shows airway obstruction. Post bronchodialator spirometry showing reduced FEV1 (less than 80%) and reduced FEV1/FVC (less than 0.7) with a typical history in a smoker over 35 with typical symptoms and no signs and symptoms more likely seen in asthma. A FBC, Chest X ray and BMI is also needed to look for other causes and for prognosis. 

More investigations may be indicated if symptoms are disproportionate with spirometry findings or in atypical presentations. 

• High resolution CT scan could show signs of emphysema. 
• Carbon monoxide lung transfer factor test 
• Chest X ray is often normal but may show signs of hyperinflation (flattened diaphragm), large bullae may be seen and blood vessels may be larger proximally and less visible peripherally. 
• Echocardiogram may be helpful if heart failure is suspected
• A1 antitrypsin levels and genotype may be appropriate in those presenting young or with no smoking history. 
• Blood gases are usually normal but may show hypoxaemia or hypercapnia
• Bloods - FBC may show polycythaemia, CRP will be raised. 
• Sputum examination is usually not helpful as most exacerbations are caused by strep pneumonia or H influenzae. 

Severity and prognosis can be assessed with the GOLD classification and the BODE index

Global initiative on Obstructive Lung Disease

Stage of COPD	Function	Symptoms
Mild	FEV1/FVC less than 0.7 FEV1 over 80%	none/mild
Moderate	FEV1/FVC less than 0.7 FEV1 50-79%	on exertion
Severe	FEV1/FVC less than 0.7 FEV1 30-49%	on minimal exertion
Very severe	FEV1/FVC less than 0.7 FEV1 less than 30% or less than 50% with respiratory failure.	at rest

BODE: 

BMI

Obstruction - FEV1 % compared to predicted

Dysponea - MRC dysponoea scale 

Exercise tolerance - distance walked in 6 minutes

Calculate BODE index here: 

http://www.qxmd.com/calculate-online/respirology/bode-index

Management

smoking cessation

Prolongs rate of deterioration and prolongs life before disability and death

Also review regularly. 

Drug treatment

1. Short acting B2 agonist (eg. salbutamol) or short acting muscarinic antagonist (eg. ipratropium)
2. If FEV1>50% start on long acting B2 agonist (eg. salmeterol) or long acting muscarinic antagonist (eg. tiotropium)
   If FEV1 under 50 start on long acting B2 agonist combined with inhaled steroid (seretide - fluticasone + salmeterol) or long acting muscarinic antagonist (eg. tiotropium) 
3. Use all 3 therapies - short acting drug + long acting B2 agonist + steroid + long acting muscarinic. *discontinue short acting muscarinic if long acting muscarinic is started*
   
   Consider other adjuncts including theophylline orally, and mucolytics. Oral steroids are rarely used in long term management. 

Long term oxygen therapy
Long term oxygen therapy may provide a survival benefit in some patients with chronic hypoxaemia. However patients must be committed as the benefit is only seen if oxygen is used for over 15 hours per day.

consider LTOT in patients with severe or very severe airway obstruction with an arterial blood gas oxygen level of less than 7.3kPa when stable, or between 7.3-8 kPa if patient shows signs of cor pneumonale (oedema), pulmonary hypertension, secondary polycythaemia rubra vera or nocturnal hypoxaemia. 

Other therapy
Pulmonary rehab can increase exercise capacity and help patients cope with breathlessness, it is very effective and patients find this really helpful.
In patients with cor-pneumonale, diuretics may be used to reduce odoema. It is also important to provide support for nutritional problems, and psychological problems such as depression and anxiety. 

Some patients may benefit from a bullectomy to allow other parts of the lung to be used if a large bullae is present. 

Opioids can sometimes reduce the sensation of breathlessness but may increase risk or respiratory failure. 

Treating complications

Nocturnal hypoxia may occur in patients with hyperaemia as breathing becomes more shallow in sleep and muscles of respiration are inhibited. These may lead to increase in pulmonary arterial pressure which may cause cardiac arrhythmias. These patients may be treated with ventilatory support (eg. BiPAP) 

Preventing and treating exacerbations

Give annual pneumococcal and influenza vaccinations

Antimucolytics may reduce sputum viscosity and reduce number of exacerbations

Treat exacertbations promptly with antibiotics and steroids- amoxicillin (although there is increasing resistance to H. influenzae) Cefaclor, cefixime have lower resistance rates, and coamoxiclav can be used alternatively.

antibiotics and steroids may be given to patients to use as soon as their sputum turns yellow/green. 

Prognosis

Prognosis depends on Age and other factors - see BODE score above. Patients with a BODE index of 0-2 has a mortality rate of 10% at 4 years whereas one with 7-10 points will have a mortality rate of 80% at 4 years. 

http://www.patient.co.uk/doctor/chronic-obstructive-pulmonary-disease

http://www.patient.co.uk/doctor/Diagnosing-COPD.htm

Kumar and Clark's Clinical Medicine