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Introduction

Chronic Obstructive Pulmonary Disease (COPD) is a chronic respiratory condition characterised by airflow obstruction, most commonly the result of a combination chronic bronchitis and emphysema.
  • Bronchitis – Cough and sputum production on most days for at least 3 months during the last two years.
  • Emphysema – Enlarged airspaces distal to the terminal bronchioles, with destruction of the alveolar walls.
Unlike asthma, in COPD there is little or no reversibility of the obstruction. The airflow limitation is usually progressive and is associated with an abnormal inflammatory response of lung tissues to certain particles. It does not change markedly over several months – i.e it is slowly progressive.
Most cases of COPD are due to smoking, or other exposure to noxious gasses or particles.
COPD is the 4th leading cause of death worldwide. 
  • Previously patients were often diagnosed with “chronic bronchitis” or “emphysema” – often dependent on their clinical symptoms. However, it is now best practice to avoid using the terms, and instead to use the diagnosis of COPD
  • COPD should be distinguished from the other main form of chronic respiratory disease – the restrictive pulmonary diseases. These are a group of disorders characterised by decreased lung capacity where FEV1 and FVC are both decreased proportionately, resulting in a normal FEV1:FVC.

In COPD the FEV1:FVC ratio is <70%. COPD can also be diagnosed in patients with FEV1:FVC ratio is >70% on the basis of clinical signs and symptoms – such as shortness of breath, or cough.

Patients typically follow a slowly progressive course, with recurrent “exacerbations”.

Long term management often involves combinations of inhaled steroids and bronchodilators, smoking cessation and pulmonary rehabilitation. It is also important to prevent exacerbations with flu and pneumonia vaccination.

Exacerbations are often mild and can be treated in primary care, but COPD also frequently present to hospital with exacerbations. Treatment of exacerbations typically involves oral steroids, increases in doses of inhaled agents, oxygen therapy and in many (but not all cases) antibiotics.

Severe long-term cases may result in the use of home oxygen therapy.

Epidemiology

  • Prevalence of about 1.5m in the UK
  • Mortality is 23,000 /year in the UK
  • It is severely under-diagnosed. Airway obstruction affects 10% off the UK population, but only about 4% of these are diagnosed with COPD – i.e. 40-60% of patients are undiagnosed
  • The 4th highest cause of death world-wide – and soon likely to be the 3rd
  • Smoking accounts for 90-98% of all cases
    • Symptoms will improve in 90% of patients with smoking cessation
  • Number of cases has stabilised in men, but is rising among women
  • Most commonly seen in ex-smokers > 35 years of age
    • Most patients done show symptoms until in their 50s
  • COPD is unlikely to develop with a smoking history less than 10 pack years
  • The number of deaths from COPD each year has been greatly reduced from 200 per 100 000, to 70 per 100 000 in the last 25 years
  • It is responsible for 1 in 8 hospital admissions
  • 25% of patients will die within the first 5 years of diagnosis
  • Associated with other co-morbidities: cardiovascular disease, lung cancer, osteoporosis, depression

Aetiology

  • Smoking
    • 10 – 20% of all smokers will develop COPD
    • Up to 50% of those with a >20 pack year smoking history will get COPD
  • Coal mining
  • Exposure to air pollution – particularly from indoor fires and cooking in the developing world
  • Genetic, i.e. α1 –antitrypsin deficiency causes emphysema
  • Low socioeconomic status and low birth weight are predisposing factors
    • Low birth weight is associated with reduce maximum lung capacity in adulthood
  • Asthma and COPD may also co-exist

Signs and symptoms

Symptoms

  • Breathlessness (dyspnoea)
  • Cough – may or may not be productive (just normal sputum)
  • Regular exacerbations
Signs
  • Tachypnoea
  • Use of accessory muscles of respiration
  • Hyperinflation
  • Reduced cricosternal distance (<3cm) – this is the distance between the cricoid cartilage and the sternal angle – this is reduced because of hyperinflation – thus the thorax is raised in relation to the cricoid cartilage.
  • Reduced chest expansion
  • Resonant chest sounds – suggestive of hyperinflation
  • Quiet breath sounds – over areas of emphysematous bullae
  • Wheeze – this is an abnormal high pitched or low pitched breath sound heard on expiration. Often a wheeze is polyphonic- this means it is made up of many different notes, and thus this shows it is caused by many abnormal airways. Wheeze is normally caused by abnormal small airways. A monophonic wheeze is caused by a single airway obstruction, and is more likely to be cancer.
  • Stridor is the name for a wheeze heard on inspiration. It is caused by abnormal large airways – and thus not normally heard in COPD. It is more likely to be heard in cancer.
  • Cyanosis
  • Cor pulmonale
  • Prolonged expiration – because their FEV1 is low, they have to have a prolonged expiratory phase to allow for adequate respiration.
  • Pursed lip breathing – This is a technique that many COPD patients adopt by themselves, but it is also taught in pulmonary rehab clinics. It will reduce the respiratory rate, as well as helping some areas of trapped air in the lungs. There is evidence to suggest it reduces dyspnoea. The respiratory rate is reduced because it just physically reduces the opening of the airway to a small size, and thus exchange of air across the opening is a slow process. This also creates an area of high pressure at the pursed lips themselves, and this high pressure will mean that the dynamic closure point is moved to a more distal area of the lung. In COPD, some of the airways will collapse at a point proximal to many of the alveoli – this point is known as the dynamic closure point. I presume this occurs due to the destruction of elastin tissue that occurs in emphysema. Anyway, pursed lip breathing keeps the pressure in the lungs higher, and thus the closure point is kept open, and thus ventilation can occur in a greater number of alveoli (more alveoli are ‘recruited’), and the VQ mismatch is reduced.
 
As we can also see, COPD leads to gas trapping – which causes an increase in dead space and leads to hyperinflation. This is not only a problem in its own right as it reduces the amount of air exchanged with outside air with each breath, but it also reduced chest wall compliance.
Hyperinflation is particularly a problem during exercise as the time for expiration is reduced, and hyperinflation is exaggerated.

Investigations

  • Lung function tests (spirometry)
    • FVC<80% predicted
    • FEV1/FVC<0.7, OR <LLN (lower limit of normal)
    • Increased residual volume
  • CXR
    • Possibly hyperinflation, but often normalF
    • Flat hemidiaphragms
    • Large central pulmonary arteries
    • Decreased peripheral vascular markings
    • Bullae
    • Cylindrical heart
  • ECG
    • Right atrial and ventricular hypertrophy suggestive of cor pulmonale, leading to large p waves on ECG p pulmonale
  • ABG – often normal, but in advanced disease, there may be:
    • Decreased PaO2
    • Increased PaCO2
  • Full Blood Count
    • Polycythaemia – measure the haematocrit – >45
    • Normocytic normochromic anaemia of chronic disease – prevalence of up to 20%.
    • HB and PCV may be raised
  • Tests for α1-antitrypsin
  • Gas transfer – reduced
    • This is a test to measure the effectiveness of gas transfer across the alveoli. Requires a known Hb value for calibration The patient inhales a known value of carbon monoxide (which has a very high affinity for haemoglobin – higher even than oxygen). In emphysema and severe fibrosis, the gas transfer value is reduced.

Diagnosis

This can be done clinically using the GOLD criteria. This measures the FEV1 as a % of the FVC – thus spirometry is the test needed for clinical diagnosis.
Stage
FEV (%)
Symptoms
0 – at risk
≥80%
None
I – Mild
≥80%
Variable
II – Moderate
50-70%
Mild to moderate
III – Severe
30-49%
Limit exertion
IV – very severe
<30%
Limit ADL’s
  • If there is no history of cigarette smoking then a tentative diagnosis of asthma is usually given instead of COPD. UNLESS, there is also a family history of lung disease suggestive of α1- antitrypsin deficiency.
  • There are no clinical features that are diagnostic. Be wary of giving a diagnosis of emphysema just on the basis of hyperinflation. Asthma may also cause this. Also be aware that in elderly patients, there may appear to be a barrel chest, but in actual fact, it is just curvature of the spine as a result of osteoporosis.

Differentiating COPD and asthma

COPD
Asthma
Age of onset >35
Age of onset <35
No diurnal variation in FEV1
Diurnal variation in FEV1
Non-reversible
Reversible
Chronic dyspnoea
Acute episodes
Sputum produced
No sputum produced
History of many years of smoking
(generally patients too young to have this)
Neutrophil infiltrate
Eosinophil infiltrate
CD8 mediated
CD4 mediated

Pathology

  • Hypersecretion of mucus due to marked hypertrophy of mucus-secreting glands and hyperplasia of goblet cells. Reduces lumen size and increasing distances for gas diffusion
  • Abnormal dilation of air spaces with destruction of alveolar walls
  • Inflammation and scarring, reducing size of lumen of airways and reducing lung elasticity
  • Initially small airways are affected and this initial inflammation is reversible, whereas in later stages larger airways become affected and the process is no longer reversible
  • Epithelial layer becomes ulcerated and squamous epithelium may be replaced by columnar cells, resulting in increased gas diffusion distance

Chronic Bronchitis

Defined as cough and sputum production on most days for at least 3 months during the last two years.

In this, there is:
  • An enlargement in mucus secreting glands (hypertrophy)
  • An increased number of goblet cells (hyperplasia)
particularly in the larger airways. In extreme cases, the bronchial tissue itself may become inflamed, and these may be pus excreted into the lumen.
the main cell involved in this reaction is the NEUTROPHIL in asthma, the main inflammatory cell involved is the eosinophil. The main leukocyte infiltrate is CD8+ in COPD, as opposed to CD4 in asthma.
After events of inflammation, there will be scarring and fibrosis of the tissue. This thickens the walls of the airway, and thus reduces the size of the lumen (thus decreasing the amount of air you can get into and out of the lungs quickly (FEV1),and also increasing the distance that gasses have to travel in order to diffuse properly.
Also remember that the inflammatory process will also cause bronchoconstriction – thus in some cases of COPD where bronchoconstriction is a factor, bronchodilators, such as salbutamol may be of some use for symptom relief.
Initially, the small airways are affected by chronic bronchitis, and this initial inflammation is reversible if smoking is stopped soon enough. Later, the larger airways become affected, and the process is no longer reversible.
In the later stages there will be fibrosis, and squamous cell metaplasia, further narrowing the bronchial lumen.
The epithelial layer can become ulcerated, and when the ulcer heals, the squamous epithelium may be replaced by columnar cells.

Emphysema

Emphysema causes enlarged airspaces distal to the terminal bronchioles, with destruction of the elastin alveolar walls causing decreased elastic recoil. 
The three main pathological effects in COPD:
  1. Loss of elasticity of the alveoli
  2. Inflammation and scarring – reducing the size of the lumen, as well as reducing elasticity
  3. Mucus hypersecretion – reducing the size of the lumen and increasing the distance gasses have to diffuse.
There are several different types of emphysema that can be identified anatomically – e.g. centrilobular and panlobular are the most common types. But this is not clinically very useful, as often several different types co-exist to different degrees.
About 1/3 of lung tissue has to be destroyed before the clinical consequences of emphysema are seen. You should also note that after the age of 25, an individual will naturally lose 30ml of functional lung capacity each year – the process of COPD just massively accelerates this!
Emphysematous bullae will often form, which are essentially just large closed off air spaces with trapped air inside them.

Α1-antitrypsin deficiency

α 1 antitrypsin is an enzyme that destroys other enzymes! It destroys several proteases, including trypsin, elastases and collagenases. In the deficiency, these enzymes aren’t destroyed, and they are allow to happily eat away at the lung tissue, leading to COPD.
The condition is genetic, and is autosomal dominant. You need to be homozygous to have clinical effects, and about 1/5000 people are. 1/10 are carriers of the gene.
The deficiency accounts for about 2% of cases of emphysema in the UK.
The proteinases that act in the lung are often released by inflammatory cells, such as macrophages. Thus, in smoking, there are more of these around, and the effect becomes exaggerated. This also explains the mechanism of emphysema in a normal individual who smokes.

Pink Puffers and Blue Bloaters

  • Pink Puffers – have a near normal PaO2, and a normal or low PaCO2 (due to hyperventilation). They ‘puff’ to increase their alveolar ventilation – and by doing so they are able to keep their blood gas values normal. These patients generally have emphysema or at least a higher degree of emphysema than bronchitis. These are likely to enter type I respiratory failure.
  • Blue Bloaters – these have decreased alveolar ventilation. They have a low PaO2 and a high PaCO2. They are cyanosed but not breathless (because their respiratory centre has become sensitised). They rely on hypoxic drive to maintain adequate ventilation. They often go on to develop cor pulmonale. These patients are more likely to be type II respiratory failure. ‘Bloater’ – due to cor pulmonale.

Exacerbations

These are most commonly caused by:
  • Streptococcus pneumoniae – this is a Gram-positive diplococcus.
  • Haemophilus influenzae – this is a Gram-negative coccobascillus.
Because these two organisms are by far the most common causes, you do not need to take a sputum sample in an exacerbation of a known COPD patient – the first line treatment is amoxicillin 500mg tds for 7 days. Second and third line options are co-amoxiclav and ciprofloxacin respectively. These have almost identical dose regimens as amoxicillin, as does clarithromycin which is given in penicillin allergic individuals.

Management

Acute exacerbations

  • Oxygen therapy – beware of CO2 retention
    • Give controlled O2 therapy to maintain sats at 88-92%
    • Perform repeat ABGs (e.g. every 20 minutes) to assess for a rise in PaCO2
    • If PaCO2 has risen > 1.5kPa consider use of CPAP or other assisted ventilation
    • PaCO2 is dependent on VENTILATION – i.e. the volume of air inhaled and exhaled
    • PaO2 is dependent on alveolar gas transfer (“OXYGENATION”) and the percentage of oxygen inhaled
    • VENTILATION and OXYGENATION are not the same!
    • In COPD, the normal respiratory drive, (usually driven by PaCO2) is not longer effective – the feedback mechanism between respiratory rate and PaCO2 has been lost. So, a patient may be adequately oxygenating due to the quality of O2 inhaled, but may not be adequately ventilating to “blow off” CO2
    • Rising PaCO2 can lead to reduced level of consciousness and is a poor prognostic factor
  • Give nebulised salbutamol (2.5-5mg in solution), and ipratropium (0.5mg)
    • Repeat doses as required
  • Give steroids – typically 50mg OD for 5-7 days
  • Treat the cause
    • Could be viral
    • Not all exacerbations need antibiotics
    • If bacterial, most common causes are Streptococcus pneumonia or Haemophilus influenza

 

Management of long-term disease

  • Smoking cessation – whatever stage the disease, this can slow down the progression
  • Long-term oxygen therapy – give 2L via nasal prongs for at least 15 hours per day
    • Known as LTOT – long term oxygen therapy
    • Smoking cessation and LTOT are the only two things that can prolong the life expectancy in COPD.
  • Pulmonary rehabilitation
  • Drugs –  salbutamol, ipratropium
  • Surgery, i.e. bullectomy in those who have large emphysematous bullae, or lung transplant in those with end-stage emphysema.
  • Exercise training
  • Diet – to promote weight gain if weight loss experienced

Drugs – in many cases these are similar to those used in asthma, despite the fact that on paper, it appears they shouldn’t work. However, in practice, many patients get great symptom relief from these drugs:

  • Short acting beta agonist or anti-cholinergic – i.e. salbutamol – 200μgevery 4-6 hours
  • Long acting beta agonist or anti-cholinergic – i.e. ipratropium – 40μg 4x a day
Exacerbations – if they have 2 or more each year, then they are eligible to try inhaled steroids.
When using these drugs, the change in FEV1 will usually be very small (the whole definition of COPD is that the airway damage is irreversible). Thus, the use of these drugs should be related to the amount of breathlessness the patient experiences.

Steroids – a trial of these is indicated in virtually any patient with symptoms. The trial is typically 40mg prednisolone for 2 weeks. If the trial increases the FEV1 by >15% then you should prescribe a long term inhaled corticosteroid – i.e. beclomethasone – 400μg twice daily. If there is no response in the trial, then there is no point giving the inhaled corticosteroid.

  • The long-term effectiveness of these drugs is yet to be established.

Antibiotics – these should be given promptly during exacerbations, as they reduce the duration of the exacerbation, and prevent hospital admission and further lung damage.

  • Patients are sometimes given their own supply of antiobiotics to keep at home, and instructed to take them as soon as their sputum turns yellow or green. They are NOT FOR PROPHYLAXIS!
    • However – there is some new evidence emerging that long term AB therapy can preserve lung function, as lung function may be lost during exacerbations.
  • Note that about 10-20% of H influenzae is now amoxicillin resistant – although this is not a major problem, as co-amoxiclav is a very useful alternative drug.

Diureticsthese are often also taken by many patients (I presume due to the secondary cor pulmonale)

LTOT – long term oxygen therapy
This can prolong the life expectancy of COPD patients! Basically, the longer you give it for, the greater the increase in life-expectancy. You should give it @ 2L via nasal prongs for at least 15 hours a day. This aims to keep oxygen saturation above 90%.
  • Only 30% of those not receiving LTOT survive more than 5 years after diagnosis.
  • By giving the LTOT you reduce the pulmonary arterial pressure. Moderate reduction is pressure is achieved after 15 hours, and a larger reduction after 19 hours a day.

Indications for LTOT

  • PaO2 <7.3kPa
  • PaO2 <8kPa, and patient also has polycythaemia, hypoxaemia, peripheral oedema or pulmonary hypertension
Patients should be asses for LTOT when they have:
  • FEV1 30-49% predicated
  • Cyanosis
  • Any of the indications above

Surgery

  • Some patients who have a large emphysematous bullae may benefit form a bullectomy. This enables adjacent areas of collapsed lung to re-expand into the space, and function again. This improves VQ mismatch.
    • Another option – you can put a valve in on bronchoscopy – this will allow air out of an emphysematous bullae, but not allow air in, and this eventually allows the bullae to collapse.
  • Another option is lung volume reduction surgery. This aims to increase the elastic recoil of the lung. Patients have to be carefully selected, and have an FEV1 <1L. it improves symptoms, but does not improve mortality.
  • Lung transplant can be performed on certain patients with end stage emphysema. It has a 3-year survival of 75%, and again, the treatment improves symptoms, but does not really affect quality of life.

Pulmonary rehabilitation

This basically just involves exercise training – and the aim is to improve symptom control. The exercises usually involve walking / climbing stairs, and can be arranged at clinic or in the home. These exercises are often in conjunction with physiotherapy and education classes. Breathing exercises are of little use.
Pulmonary rehabilitation has no effect on life expectancy

Diet

Patients can lose weight – this is a particularly bad prognostic sign – because it shows that they are expending a huge amount of energy trying to breathe – you have to encourage them to try and gain weight – but you can lose muscle mass, and this will make it even more difficult to breathe.

Considerations

Vaccination

COPD patients should receive an annual flu vaccine, and a one-off vaccine of polyvalent pneumococcal polysaccharide – which provides life-long immunity.

Air travel

Commercial airliners have a cabin pressure equal to an altitude of 2750m. At this level PaO2 will fall from 13.5kPa to 10kPa – and oxygen saturation will fall by 3%. In normal healthy individuals this has no effect, but in patients with even moderate COPD, this can reduce their O2 saturation to around 6.5kPa and oxygen therapy may be needed. As a result, patients with COPD should consult their doctor / airline before travelling.

Weight loss and COPD

This is a bad prognostic sign. It is thought to be caused by the increased energy needs of the body as a result of the massive amount of energy needed for respiration. A small contributory factor may also be that patients find it hard to eat because they are too breathless!

Complications

Patients will either basically get respiratory failure or cor pulmonale.

Respiratory Failure

  • Cardiac output will be normal or slightly increased
  • Salt and fluid retention will occur as a result of renal hypoxia
  • Technically, respiratory failure occurs when the PaO2 <8kPa, or the PaCO2 >7kPa.

Type one respiratory failure

This is hypoxaemia without hypercapnia. The CO2 level will tend to be normal or low. It is caused by a VQ mismatch. Common causes include:
  • Pneumonia
  • Pulmonary oedema
  • PE
  • Asthma
  • Emphysema
  • Fibrosing alveolitis
  • ARDS

Treatment

  • Treat the underlying cause
  • Give O2 (35-60%) by face mask to correct the hypoxia
  • If PaO2 does not rise above 8kPa then give assisted ventilation

Type two respiratory failure

This is hypoxaemia with hypercapnia. It is a result of alveolar hypoventilation. There is not VQ mismatch. Common causes include:
  • Pulmonary disease (COPD, asthma, pulmonary fibrosis, obstructive sleep apnoea)
  • Reduced respiratory drive – can be a result of sedentary drugs, trauma or CNS tumour
  • Neuromuscular disease – e.g. cervical cord lesion, diaphragmatic paralysis, polio, myasthaenia gravis
  • Thoracic wall disease

Treatment

In type II failure, the respiratory centre is likely to have become desensitised to CO2 levels, and hypoxia will now be its main driving force, thus oxygen therapy should be given with care! However, don’t leave the hypoxia untreated!
  • Give controlled oxygen therapy, starting at 24% O2
  • Recheck the ABG after 20 minutes – if the PaCO2 is steady or lower, then you can increase the O2 to 28%.
    • If the PaCO2 has risen >1.5kPa– then consider giving a respiratory stimulant such as doxapram (1.5-4mg/min IV) or assisted ventilation.
    • You can also see CO2 retention as physical signs – the patient will become drowsy and confused
    • If this fails consider intubation / ventilation

Cor pulmonale

  • This is right sided heart failure, as a result of pulmonary hypertension
  • The patient is likely to be cyanosed – look at the hands!
  • They are also likely to have ankle oedema and ascites due to fluid retention
  • Likely to have severe breathlessness
  • There may be an especially loud pulmonary heart sound, and there may be a diastolic murmur, as a result of incompetence of the pulmonary valve.

References

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