last authored: Feb 2012, David LaPierre
Chronic Obstructive Pulmonary Disease (COPD) is the only major cause of death on the rise in Canada, and is currently the fourth leading cause of death in adults. It accounts for approximately 10% of bed occupancy in most hospitals.
COPD is characterized by progressive dyspnea, or shortness of breath, caused by two main disease processes:
This is contrasted with asthma, a chronic inflammatory disorder characterized by airway hyperactivity and reversible airway obstruction, as well as cystic fibrosis or bronciectasis.
An acute exacerbation of COPD (AE-COPD) is defined as at least two of: worsening SOB, increased sputum production, or increased sputum purulence.
William is a 46 year-old smoker who comes to your office with a 3 month history of chronic cough. He asks you if this could be COPD, which his friend was recently diagnosed with.
Prevalence is associated with increasing age, lower socioeconomic, and smoking.
Smoking is the cause of COPD in over 90% of cases, although only 20% of smokers develop clinically significant COPD, suggesting genetic involvement as well. Most nonsmokers show a decline in FEV1 of 35-40 ml/year. This rate is increased to 45-60 ml/year in smokers, and up to 70-120 ml/year in people apparently genetically susceptible.
Other causes include:
There are two main pathological processes that contribute to COPD:
Decreased elastic recoil leads to hyperinflation, increased residual volumes and FRC, and total lung capacity. Diaphragmatic flattening reduces contractile efficiency.
Emphysema describes the rupture or fragmentation of alveolar walls, without obvious fibrosis, leading to airspace enlargement.
It is classified according to its lobular distribution.
Centriacinar emphysema is the most common form, affecting the central or proximal acini located on respiratory bronchioles while sparing the distal sacs. It is more common in the upper lobes. Centriacinar emphysema is associated with heavy smoking, and walls often contain a large amount of black pigment. Smoke particles predominantly impact the bronchiole bifurcations.
Panacinar (panlobular) emphysema affects the entire acinus, more commonly in the lower zones of the lung. It is associated with α1-antitrypsin deficiency.
Paraseptal disease usually occurs in upper lobes, often caused by spontaneous pneumothorax.
With advanced disease, large abnormal airspaces can lead to blebs or bullae. Rupture of these can lead to pneumothorax.
In chronic bronchitis, mucus hypersecretion and goblet cell hyperplasia follow chronic irritation by tobacco smoke or other factors. Increases in mucus gland size can be estimated by the Reed index, or the proportion of the wall thickness taken up by the mucous layer.
Small airways can become obstructed by mucus, inflammation, edema, and fibrosis.
Infection can be caused by decreased performance of the ciliary elevator and decreased clearing of bacteria by leukocytes, both mediated by smoking. As such, airways are often colonized by bacteria.
Macrophages, CD8+ lymphocytes, and neutrophils are all involved, and a variety of mediators, including leukotriene B4, IL-8, TNF, and others, damage lung structures and sustain inflammation.
An imbalance between proteases and antiproteases appears involved, as evidenced by α1-AT deficiency. An imbalance in oxidant-antioxidant levels is also important.
Tobacco smoke recruits neutrophils and macrophages, both which release elastase. Smoke also leads to the inactivation of alpha-1 antitrypsin.
We want to be able to diagnose people early.
Chronic bronchitis is defined as persistent cough with sputum for at least three months in at least 2 consecutive years, in the absence of any other identifiable cause.
Imagine the dyspnea of COPD dyspnea
Chronic bronchitis can cause:
Emphysema symptoms do not appear until at least one third of lung parenchyma is damaged. These can include:
Dyspnea is usually the first symptom, with a slow but steady progression.
Dysnpea is increased with upper arm exercise as people lose the use of their accessory breathing muscles.
MRC Categorization of Dyspnea
Assess actual exercise capacity; ask I could you walk up a hill?
Physical exam is not diagnostic of COPD, and may underestimate severity. As disease progresses, lungs may appear hyperresonant to percussion. Auscultation can show few ronchi, wheezes, or faint crackles.
During late stages, patients can show cyanosis, evidence of increased work of breathing, sitting forward in a hunched position, using accessory muscles, and breathing through pursed lips.
People with COPD can develop barrel chests.
If pulmonary hypertension develops, cor pulmonale can follow. Heart gallop, distended neck veins, hepatojugluar reflux, and leg edema can all be present.
It is essential to diagnose COPD early. The Canadian lung health test suggests current or ex-smokers over 40 years of age, who answer 'yes' to any of the following questions, should have spirometry done:
Diagnosis of COPD is made when the FEV1 / FVC is less than 70% of predicted, with results not normalizable with bronchodilators (in contrast with asthma). This is because loss of elastic driving force and airflow limitation reduces FEV1, (forced expiratory volume in one second). Decreases in FEV1 predominate over that of FVC.
Classification by impairment of lung function: FEV1 value (GOLD guidelines)
Destruction of alveoli can lead to ventilation/perfusion (V/Q) mismatch, leading to hypoxemia.
Vital capacity decreases while FRC and RV increases and TLC increases or stays the same.
Investigations can reveal:
Chest X-rays do not often show early signs of COPD, but can later show hyperinflation, hyperlucency, diaphragmatic flattening, and bullous formation. If pleural abnormalities, lymphadenopathy, or mediastinal widening are seen, lung cancer should be suspected.
CT allows for detailed evaluation of lung tissue.
ECG can show evidence of right ventricular strain.
Other conditions to rule out include:
Patients need to be self-managers, requiring education and collaboration with the health care team.
Quitting smoking is the single most effective intervention to reduce the risk of developing COPD and the only intervention shown to slow its progression. (Fletcher and Peto, BMJ, 1977) has a good figure showing slowed decline of FEV1 in people who have quit smoking. Telling patients their 'lung age' can assist people with quitting (ref).
Home oxygen, as described in a subsequent section, may also be useful for patients with chronic hypoxia.
Lastly, immunizations against pneumococcus and influenza are critical.
Regular physical exercise could be considered a medical intervention with COPD.
close follow-up and disease monitoring
Bronchodilators reduce dyspnea and air trapping while improving quality of life, though this may not be accompanied by improvement in spirometry.
Short-acting beta-agonists are the initial medication for occasional symptoms.
Long-acting anticholinergic drugs may be added if short-acting beta-agonists are not fully effective.
Long-acting β-adrenoreceptor agonists may be used alone, but more often are in combination with a steroid
A combination of long-acting medications is generally preferred. Bronchodilators can be delivered in metered-dose inhalers (MDIs) or nebulizers.
Inhaled corticosteroids (ICS), together with long-acting beta-agonists (LABAs), reduce the rate of exacerbations and increase function, but have no impact on survival, as shown by the TORCH study (Calverley et al, 2007). These include:
If disease is still not able to be brought under control, COPD, may be treated with a number of agents:
Oxygen is one of the few interventions shown to improve survival in COPD. It is recommended once saturation decreases to 88%, though can be used if end-organ damage becomes apparent.
Oxygen is frequently necessary in AE-COPD.
prevention of exacerbations
AECOPDs: if sputum is purulent, treat with antibiotics. Emperic antibiotics should be used.
corticosteroids, typically 30-50 mg daily prednisone or equivalent for 7-14 days.
long term systemic steroids should not be used.
For patients in distress, supplemental oxygen and short-acting bronchodilators should be given. Inhaled anticholinergics may also be used.
Oral or IV corticosteroids are also often given.
admit to hospital
RF: consider aminophylline
Severe disease can lead to pulmonary hypertension and cor pulmonale, respiratory acidosis, or massive pneumothorax.
AECOPDs are sustained worsening of dysnpea, cough, or sputum production leading to an increase in the use of maintenance medications and/or supplementation with additional medication.
AECOPDs have a 2x mortality risk of acute MI patients.
patients can be taught to measure the colour of their sputum.
One-year mortality after AE-COPD appears to be above 40% (Schiele F et al, 2005).
People at increased risk of death include:
It is critical to ensure to have discussions surrounding end-of-life care.
Qaseem et al. 2011. Diagnosis and management of stable chronic obstructive pulmonary disease: a clinical practice guideline update from the American College of Physicians, American College of Chest Physicians, American Thoracic Society, and European Respiratory Society. Ann Intern Med. 155(3):179-91.
Can Resp.J 2008 15(Suppl A)1A-8A.
Bourbeau et al, Arch Int Medicine 2003
Living Well with COPD (password: copd)