NURSING 2LA2 Lecture Notes - Lecture 7: Airway Obstruction, Chronic Obstructive Pulmonary Disease, Bronchopulmonary Dysplasia
28 Nov 2016
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Module 7: Alterations in Respiratory Function
COPD (Chronic Obstructive Pulmonary Disease)
COPD in Canada
• COPD is a major respiratory disease in Canada that is often preventable and can be treated but
remains underdiagnosed. It is thought that the prevalence of COPD is underestimated because those
with early symptoms of COPD are not recognized and/or do not seek treatment.
• COPD affects at least 700,000 adults which is approximately 4.4% of Canadians aged 35 years or older.
In contrast, COPD affects a much higher percentage of off reserve Aboriginal people at 7.9%.
• COPD is the fourth leading cause of death in females and fifth in males.
• There is a higher prevalence in women except for the aged 75 years and older group.
• Over the past 15 years, mortality rates have increased, especially for women.
• Mortality rates are higher in males (4.5/100,000) than females (2.8/100,000). Mortality rates may
actually be higher than reported because two complications of COPD, pneumonia and congestive heart
failure may be listed as the cause of death instead of COPD.
• Also, it is predicted that as new epidemiological data emerges, the mortality rate in women will be
higher than in men.
• COPD is also a major cause of death worldwide. In the US, it is the 4th leading cause of death and it is
the 6th leading cause of death worldwide. Like Canada the mortality and morbidity are increasing
around the world. The burden of COPD from a health, economical and societal cost is significant.
• Hospitalizations, ER visits, pharmacotherapy, pulmonary rehabilitation, oxygen therapy, missed work
days are but a few of the items that were studied in the Confronting COPD survey in North America
and Europe which studied the burden of COPD in different countries.
• Among major chronic illnesses in Canada, COPD now accounts for the highest rate of hospital
admissions. Hospitalization for AECOPD are on average 10 days in length and cost about $10,000. A
conservative estimate of the total cost of COPD hospitalizations in Canada is 1.5 billion dollars per
year.
• It is beyond the scope of this lecture to go into further detail about the actual costs of care.
Etiology
• Cigarette smoking is the leading cause of COPD.
• 15-20% of smokers will be diagnosed with COPD, this does not take into account smokers who have
yet to be diagnosed with COPD.
• An average smoker loses lung function at twice the rate of a non-smoker. This means that smoking
adults lose lung function at a more rapid rate as they age in comparison to non-smokers.
• Loss of lung function is associated with increased mortality.
• Adolescents who begin smoking before they are finished growing will inhibit maximal lung
development.
• Smoking is common in people diagnosed with COPD as 80-90% of them have a history of smoking.
• Smoking is toxic to cells in the lungs and also impairs the mechanisms that are responsible for lung
tissue repair. It is important to note that both active and passive smoking have been implicated in
COPD.
• Genetics also play a contributing factor to developing COPD.
• Genetic susceptibilities have been identified. Polymorphisms of genes that code for TNF, surfactant,
proteases and antiproteases are examples. Also, a hereditary deficiency of alpha-1 antitrypsin may
result in early onset and severe COPD. The onset and severity is worsened by smoking.
• The heterogeneous nature of COPD can be attributed to multiple genetic and environmental factors as
well as gene to gene and gene to environment interactions known as epigenetics.
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• Genetics have a role in how the phenotypes are expressed and how gene environment interactions
contribute to disease manifestations such as exacerbations.
• Environmental risk factors include long-term inhalational exposure to: occupational dusts or chemicals;
indoor pollution from heating and cooking with biomass fuels; and outdoor pollution.
• Other risk factors include severe childhood respiratory infections, asthma, airway hyper
responsiveness, nutritional compromise, impairment of fetal development resulting in low birth
weight, and infants who develop bronchopulmonary dysplasia.
• Although the risk factors listed on this slide are relevant in the etiology of COPD, the most important
etiologic factor is cigarette smoking.
COPD Phenotypes
• COPD is not a single disorder. Rather it is a group of disorders that are characterized by airflow
limitation. These different phenotypes may overlap and include chronic bronchitis, emphysema, and
bronchiectasis.
• Chronic bronchitis is characterized by airway inflammation and obstruction of the major and small
airways. A history of a chronic productive cough for at least 3 consecutive months over 2 consecutive
years is required for clinical diagnosis.
• Emphysema is characterized by loss of lung elasticity and abnormal enlargement of the airspaces distal
to the terminal bronchioles with destruction of the alveolar walls and capillary beds.
• Bronchiectasis is an uncommon form of COPD characterized by permanent dilation of the bronchi and
bronchioles. It is caused by destruction of the muscle and elastic supporting d/t vicious cycles of
infection and inflammation.
• Asthma is a chronic inflammatory airway disorder where lung function if often normalized in the
absence of triggers especially early on in the disease prior to significant airway remodeling. Asthma is
usually not classified under COPD but together asthma and COPD can be called obstructive airway
diseases.
Comparing Asthma and COPD
• Before we look at the pathophsiolog of COPD let’s take a oet to opae astha ad COPD.
• The course of asthma is usually intermittent while that of COPD is chronic and progressive.
Defining COPD
• The Caadia Thoai “oiet defies COPD as a espiato disode lagely caused by smoking,
characterized by progressive, partially reversible airway obstruction and lung hyperinflation, systemic
aifestatios, ad ieasig feue ad seeit of eaeatios.
• COPD is characterized by persistent inflammation of airways, lung parenchyma and its vasculature.
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• The pathophysiological hallmark of COPD is expiratory flow limitation.
Airflow Limitation Mechanisms
• The four most important mechanisms for airflow limitation are listed here. Any of which can occur in
either asthma or COPD.
1. Loss of lung elastic recoil occurs with emphysema due to protease mediated degradation of
connective tissue elements in the lungs.
2. Peribronchiolar fibrosis ous due to a ialae etee the lug’s epai ad defese
mechanisms. Fibrosis of the small airways contributes to airway remodelling which is a key factor
in the development of the irreversible airflow limitation seen in COPD. Fromer and Cooper define
aia eodellig as the pesistet hages that ou ithi the stutural components of the
aias i espose to iflaatio.
3. Increased airway secretions. In COPD there is mucus hyperplasia and increased expression of
mucin genes. Inflammation and oxidant injury play a role in mucus hypersecretion.
4. Airway smooth muscle. Increased tone in airway smooth muscle due to hyper reactivity of the
bronchi with bronchoconstriction due to persistent inflammation. Even if tone is not increased in
persons with COPD their airways are narrower resulting in an increase in airway resistance.
Relaxing airway smooth muscle with bronchodilators will have a beneficial effect on airflow
whether there is increased tone or not.
Chronic Bronchitis
• People diagnosed with COPD usually have some degree of both emphysema and chronic bronchitis.
• Chronic bronchitis is the result of inflammation of the airway epithelium and mucus hypersecretion
due to inspired irritants like tobacco smoke or air pollution.
• Hypersecretion in the large airways is the first feature of chronic bronchitis. The mucus produced is not
only more tenacious than normal but there is also an increase in the size and number of mucous
glands and goblet cells in the airway epithelium.
• Ciliary function is impaired which reduces mucus clearance.
• There is an increased risk of pulmona ifetio ad iju as the lug’s defee ehaiss ae
compromised. Bacterial colonization may occur. Bacteria such as haemophilus influenza and
streptococcus pneumoniae can become embedded in the airway secretions.
• Infection and injury cause further mucus production and inflammation. Recurrent infections and
persistent inflammation result in bronchospasm and eventual permanent narrowing of the airways.
• Thick mucus and hypertrophied bronchial smooth muscle leads to airway obstruction. Air trapping can
result as the airways collapse early in expiration when the airways are narrowed trapping gas in distal
portion of the lung.
• Airway obstruction causes ventilation-perfusion mismatch, hypercapnia and hypoxemia. Significant
hypoxemia will lead to polycythemia which is the overproduction of red blood cells and cyanosis.
• Eventually if not reversed, hypoxemia will lead to pulmonary hypertension and cor pulmonale or
enlargement of the right ventricle which will in turn cause right heart failure.
Emphysema
• Emphysema is characterized by the breakdown of elastin in the alveolar septa and bronchial walls as
well as breakdown of alveolar and bronchial wall components by proteases. Proteases are enzymes
that digest proteins.
• This occurs due to an imbalance between proteases and antiproteases as a result of increased
protease activity and inhibition of normal endogenous antiprotease activity in the lung.
• The leading cause of this is airway epithelial inflammation from toxins in tobacco smoke or air
pollution.
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Document Summary
Copd in canada: copd is a major respiratory disease in canada that is often preventable and can be treated but remains underdiagnosed. In the us, it is the 4th leading cause of death and it is the 6th leading cause of death worldwide. Like canada the mortality and morbidity are increasing around the world. Hospitalization for aecopd are on average 10 days in length and cost about ,000. A conservative estimate of the total cost of copd hospitalizations in canada is 1. 5 billion dollars per year: it is beyond the scope of this lecture to go into further detail about the actual costs of care. It is important to note that both active and passive smoking have been implicated in. Copd: genetics also play a contributing factor to developing copd, genetic susceptibilities have been identified. Polymorphisms of genes that code for tnf, surfactant, proteases and antiproteases are examples.
