COPD (Chronic Obstructive Pulmonary Disease)

Original Editor - Rachael Lowe

Top Contributors - Laura Ritchie, Rachael Lowe, Scott Buxton, Evan Thomas and George Prudden

Clinically Relevant Anatomy

The Lungs

See this page for information on the anatomy of the lungs

Causes

  • Smoking - The primary risk factor for COPD is chronic tobacco smoking. In the United States, 80 to 90% of cases of COPD are due to smoking.[1]
  • Occupational exposure - Intense and prolonged exposure to workplace dusts found in coal mining, gold mining, and the cotton textile industry and chemicals such as cadmium, isocyanates, and fumes from welding have been implicated in the development of airflow obstruction, even in nonsmokers.[2] Workers who smoke and are exposed to these particles and gases are even more likely to develop COPD. Intense silica dust exposure causes silicosis, a restrictive lung disease distinct from COPD; however, less intense silica dust exposures have been linked to a COPD-like condition.[3] The effect of occupational pollutants on the lungs appears to be substantially less important than the effect of cigarette smoking.[4]
  • Air pollution - Studies in many countries have found that people who live in large cities have a higher rate of COPD compared to people who live in rural areas.[[5] Urban air pollution may be a contributing factor for COPD as it is thought to slow the normal growth of the lungs although the long-term research needed to confirm the link has not been done. In many developing countries indoor air pollution from cooking fire smoke (often using biomass fuels such as wood and animal dung) is a common cause of COPD, especially in women.[6]
  • Genetics - Some factor in addition to heavy smoke exposure is required for a person to develop COPD. This factor is probably a genetic susceptibility. COPD is more common among relatives of COPD patients who smoke than unrelated smokers.[7]] The genetic differences that make some peoples' lungs susceptible to the effects of tobacco smoke are mostly unknown
  • Autoimmune disease - There is mounting evidence that there may be an autoimmune component to COPD.[8] Many individuals with COPD who have stopped smoking have active inflammation in the lungs.[9]The disease may continue to get worse for many years after stopping smoking due to this ongoing inflammation.[9] This sustained inflammation is thought to be mediated by autoantibodies and autoreactive T cells.[10]

Mechanism of Injury / Pathological Process

It is not fully understood how tobacco smoke and other inhaled particles damage the lungs to cause COPD. The most important processes causing lung damage are:

  • Oxidative stress produced by the high concentrations of free radicals in tobacco smoke.
  • Cytokine release due to inflammation as the body responds to irritant particles such as tobacco smoke in the airway.
  • Tobacco smoke and free radicals impair the activity of antiprotease enzymes such as alpha 1-antitrypsin, allowing protease enzymes to damage the lung.

Clinical Presentation

COPD is a complex interaction between Chronic Bronchitis, Emphysema, and Asthma

Asthma

Asthma is a chronic lung disease which is a very common respiratory condition. It is also known as a reactive airway disease which is inconvenient most of the time but manageable. Asthma is caused by inflammation and constriction of bronchial walls which leads to a series of spasmodic attacks of wheezing and shortness of breath as a result of the hyper-reactivity of smooth muscle in the bronchial walls and in the absence of any other apparent cause. There are various factors such as exposure to cigarette smoke, climate change, physical exertion or emotional stress that causes asthma. It begins during childhood and the disease is commonly triggered by viral infection[11].

Asthma can be diagnosed by the presence of the signs and symptoms. The diagnosis is normally confirmed by presenting a response to a inhaled bronchodialator. Often pulmonary function tests, chest x-rays and blood tests can also be done in order to confirm the diagnosis.

Chronic bronchitis

Bronchitis

Lung damage and inflammation in the large airways results in chronic bronchitis. Chronic bronchitis is defined in clinical terms as a cough with sputum production on most days for 3 months of a year, for 2 consecutive years.[12] In the airways of the lung, the hallmark of chronic bronchitis is an increased number (hyperplasia) and increased size (hypertrophy) of the goblet cells and mucous glands of the airway. As a result, there is more mucus than usual in the airways, contributing to the narrowing of the airways and causing a cough with sputum. Microscopically there is infiltration of the airway walls with inflammatory cells. Inflammation is followed by scarring and remodeling that thickens the walls and also results in narrowing of the airways. As chronic bronchitis progresses, there is squamous metaplasia (an abnormal change in the tissue lining the inside of the airway) and fibrosis (further thickening and scarring of the airway wall). The consequence of these changes is a limitation of airflow.[13]

Patients with advanced COPD that have primarily chronic bronchitis rather than emphysema were commonly referred to as "blue bloaters" because of the bluish color of the skin and lips (cyanosis) seen in them.[14] The hypoxia and fluid retention leads to them being called "Blue Bloaters."

Emphysema

A lateral chest x-ray of a person with emphysema.
Note the barrow chest and flap diaphragm.

Lung damage and inflammation of the alveoli results in emphysema. Emphysema is defined as enlargement of the air spaces distal to the terminal bronchioles, with destruction of their walls.[12] The destruction of air space walls reduces the surface area available for the exchange of oxygen and carbon dioxide during breathing. It also reduces the elasticity of the lung itself, which results in a loss of support for the airways that are embedded in the lung. These airways are more likely to collapse causing further limitation to airflow. The effort made by patients suffering from emphysema during exhalation, causes a pink color in their faces, hence the term commonly used to refer to them, "pink puffers".

Diagnostic Procedures

  • Assessment - 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.
  • Spirometry - The presence of airflow obstruction should be confirmed by performing post-bronchodilator spirometry. All health professionals involved in the care of people with COPD should have access to spirometry and be competent in the interpretation of the results
  • X-Ray - An x-ray of the chest may show an over-expanded lung (hyperinflation) and can be useful to help exclude other lung diseases.
  • Pulmonary function tests - Complete pulmonary function tests with measurements of lung volumes and gas transfer may also show hyperinflation and can discriminate between COPD with emphysema and COPD without emphysema.
  • Blood tests - A blood sample taken from an artery can be tested for blood gas levels which may show low oxygen levels (hypoxemia) and/or high carbon dioxide levels (respiratory acidosis). A blood sample taken from a vein may show a high blood count (reactive polycythemia), a reaction to long-term hypoxemia.

Outcome Measures

Follow the link here for a list of outcome measures within Physio-pedia.

There can be a different number of ways of measuring the impact or change of someone's COPD, examples being from lung function, lung volumes and exercise capacity.

Lung function - Forces Expiratory Volume in 1 second (FEV1)

It is known that COPD lungs lose function quicker and more rapidly than non-COPD lungs. In recognition of this FEV1 is the most important marker to determine severity and treatment in COPD algorithms, with decline of FEV1 over-time as the marker for disease progression[15]. The ratio of FEV1/FVC (Forced vital capacity) as well as the percentage predicted FEV1 is a fixed ratio used in current guidelines to assess the function of lungs.

The strengths of using this measure is that:

  • FEV1 and FVC measurements are highly reproducible
  • Poor lung function if a risk factor for all cause of cardiovascular mortality and poorer health[16]

Limitations being:

  • FEV1 measurements are based on an artificial manoeuvre and do not always correlate with clinically relevant outcomes such as dyspnoea, health status, exercise capacity, or exacerbations[17][18]
  • Patients with similar FEV1 may represent different underlying phenotypes.
  • Reference equations for lung function by European Community for Coal and Steel are disputed and limited in predicting lung function in the general population [19]
  • No minimal important difference (MID) has been established yet. It was suggested that an appropriate range of values for the MID for FEV1 might be 100-140 mL but the MID for FEV1 remains poorly defined for COPD [20]

Lung Volumes

Changes in absolute lung volumes can occur in COPD patients even in the absence of FEV1 changes. Progressive hyperinflation due to airflow limitation and loss of lung elastic recoil not only increases the work required during inspiration but also profoundly decreases the ventilatory reserve and increases the sense of effort and dyspnoea[21]

In terms of measurement static lung hyperinflation and its increase during exercise (dynamic hyperinflation) are measured as elevations of total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV) and as a decrease in inspiratory capacity (IC)[15].

Strengths of lung volumes include:

  • Indices of dynamic hyperinflation correlate better than FEV1 with activity limitation and exertional dyspnoeaand pharmacological and surgical lung volume reduction have been associated with improvements in exercise performance and dyspnoea[22][23]
  • A severely reduced IC/TLC ratio with a threshold value of 25% has been shown to predict mortality in COPD patients[24]

Weaknesses include:

  • Body plethysmography remains the gold standard for the measurement of lung volumes such as TLC, FRC and RV. Spirometrically derived assessments of lung hyperinflation are more difficult to interpret in the absence of simultaneous bodyplethysmographic volume measurements to rule out a concomitant restrictive ventilatory disorder[25]
  • The reproducibility of FRC, IC and RV in absolute values has yet to be demonstrated. Measurement of IC alone is not a reliable marker of lung hyperinflation and does not consistently reflect changes in FRC or TLC[25]
  • The natural course of dynamic hyperinflation in COPD is unknown and seems likely to be highly variable among COPD patients [25]

Exercise Capacity

Includes the 6 Minute Walk test, the Bleep Test, Shuttle Walk Test and Ergometry.

Management / Interventions

Stopping Smoking

Encouraging patients with COPD to stop smoking is one of the most important components of their management. All COPD patients still smoking, regardless of age, should be encouraged to stop, and offered help to do so, at every opportunity.

Exercise

[26]

Exercise prescription is a key component of pulmonary rehabilitation programmes, which are part of the non-pharmacological approach to managing COPD. There is a high level of evidence for the benefits of pulmonary rehabilitation for people with COPD[27] Strength and endurance exercise are endorsed for people with COPD.[28]

Muscles that are required for arm exercise are also involved in movement of the chest wall during respiration and thus the need to breathe often compromises the individual’s ability to undertake daily activities, therefore exercise prescription involving arm exercise needs to be carefully prescribed.[29]

Promote effective inhaled therapy

In people with stable COPD who remain breathless or have exacerbations despite use of short-acting bronchodilators as required, offer the following as maintenance therapy:

  • if forced expiratory volume in 1 second (FEV1)≥50% predicted: either long-acting beta2 agonist (LABA) or long-acting muscarinic antagonist (LAMA)
  • if FEV1<50% predicted: either LABA with an inhaled corticosteroid (ICS) in a combination inhaler, or LAMA

Offer LAMA in addition to LABA + ICS to people with COPD who remain breathless or have exacerbations despite taking LABA + ICS, irrespective of their FEV1.

Provide pulmonary rehabilitation

Pulmonary rehabilitation should be made available to all appropriate people with COPD including those who have had a recent hospitalisation for an acute exacerbation.

Use non-invasive ventilation

[30]

Non-invasive ventilation (NIV) should be used as the treatment of choice for persistent hypercapnicventilatory failure during exacerbations not responding to medical therapy. It should be delivered by staff trained in its application, experienced in its use and aware of its limitations. When patients are started on NIV, there should be a clear plan covering what to do in the event of deterioration and ceilings of therapy should be agreed.

Manage exacerbations

The frequency of exacerbations should be reduced by appropriate use of inhaled corticosteroids and bronchodilators, and vaccinations.

The impact of exacerbations should be minimised by:

  • giving self-management advice on responding promptly to the symptoms of an exacerbation
  • starting appropriate treatment with oral steroids and/or antibiotics
  • use of non-invasive ventilation when indicated
  • use of hospital-at-home or assisted-discharge schemes

Ensure multidisciplinary working

COPD care should be delivered by a multidisciplinary team.

Managing symptoms and conditions in stable COPD

Breathlessness and exacerbations

  • Manage breathlessness and exercise limitation with inhaled therapy
  • For exacerbations or persistent breathlessness:
    • use long-acting bronchodilators or LABA + ICS
    • consider adding theophylline if still symptomatic
  • Offer pulmonary rehabilitation to all suitable people
  • 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
    • TLCO greater than 20% predicted
  • 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
    • local surgical protocols

Frequent exacerbations

  • Optimise inhaled therapy
  • Offer vaccinations and prophylaxis
  • Give self-management advice
  • Consider osteoporosis prophylaxis for people requiring frequent oral corticosteroids

Cor pulmonale

Cor Pulmonale
  • Consider in people who have peripheral edema, a raised venous pressure, a systolic parasternal heave, a loud pulmonary second heart sound
  • Exclude other causes of peripheral edema
  • Perform pulse oximetry, ECG and echocardiogram if features of cor pulmonale
  • Assess need for LTOT
  • Treat edema with diuretic
  • Angiotensin-converting enzyme inhibitors, calcium channel blockers, alpha-blockers are not recommended
  • Digoxin may be used where there is atrial fibrillation

Respiratory failure

  • Assess for appropriate oxygen
  • Consider referral for assessment for long-term domiciliary NIV therapy

Abnormal BMI

  • Refer for dietetic advice
  • Offer nutritional supplements if the BMI is low
  • Pay attention to weight changes in older patients (especially>3 kg)

Chronic productive cough

  • Consider mucolytic therapy

Anxiety and depression

Alpha-1 antitrypsin deficiency

  • Offer referral to a specialist centre to discuss the clinical management of this condition
  • Alpha-1 antitrypsin replacement therapy is not recommended

Palliative setting

  • Opioids should be used when appropriate for the palliation of breathlessness in people with end-stage COPD unresponsive to other medical therapy
  • Use benzodiazepines, tricyclic antidepressants, major tranquillisers and oxygen to treat breathlessness
  • Provide access to multidisciplinary palliative care teams and hospices

Resources

  • KNGF guidelines for physical therapy in patients with chronic obstructive pulmonary disease

Videos

References

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