Obstructive Airways Disease Flashcards
What is emphysema?
A condition in which the air sacs of the lungs are damaged and enlarged causing breathlessness
Where do you find obstructive and restrictive disease?
Obstructive = In the airways Restrictive = In the lungs
What 3 conditions are the different pathological entities of obstructive airway syndrome?
Asthma
Chronic bronchitis
Emphysema
COPD^
What is ACOS syndrome?
Its the overlap of COPD and asthma - basically smokers with symptoms of asthma (such as reversibility, eosinophilia who are steroid responsive)
Respond better to ICS wrt exacerbation reductions
More reversible to salbutamol
Difficult to distinguish from asthmatic smokers who have airway remodeling (ie reduced FVC)
What is commonly found in asthma and COPD/chronic bronchitis?
Asthma - eosinophil infiltrate in bronchial mucosa
COPD/Chronic bronchitis - neutrophil infiltrate in bronchial mucosa
Describe the airways in terms of large and small airways, and gas transfer and gas exchange?
Large airways = trachea and bronchi
Small airways = Bronchioles, terminal bronchioles and alveolar ducts/sacs
Gas transfer (conducting zone) = Trachae, bronchi and bronchioles Gas exchange (Acinar zone) = terminal bronchioles and alveolar ducts/sacs
Particles smaller than 5 and 2 microns can enter what area of the airways?
5 Microns = will get past the carina
2 microns = will get past the bronchioles
Describe the aetiology (the cause) of airway obstruction in COPD and asthma?
The mucosa becomes enlarged due to inflammation which leads to invagination of the lumen which closes it off/occudes it.
This causes the wheezing noise when breathing out due to the turbulent airflow
What is chronic bronchitis?
Long term inflammation of the airways
Describe the asthma triad?
3 factors you must have to have asthma
- airway inflammation - primarily eosinophils
- Airway hyperresponsiveness - twitching of the airways due to inflammation, when activated by a stimulus the airways will respond in a abnormal way.
- REVERSIBLE airflow obstruction - the airways can reversibly dilate, they are in a constant state of not knowing whether to contract or dilate.
Describe the dynamic evolution of asthma?
Bronchoconstriction - brief symptoms
Chronic airway inflammation - exacerbations AHR
Airway remodelling - fixed airway obstruction - then becomes irreversible, collagen is laid down, can’t get rid of it.
Name 3 hallmarks of remodelling in asthma?
Thickening of the basement membrane
Collagen deposition of the submucosa
Hypertrophy of the smooth muscle
Describe the inflammatory cascade in asthma?
- Genetic predisposition + Triggers (allergens, chemical etc) - if you have the gene you’re more likely to get it, in combo with allergies for example.
- Eosinophilic Inflammation - (above) leads to inflammation cells from the TH2 cells which create cytokine environment etc, resulting in eosinophilic inflammation.
- Mediators, TH2 cytokines - Histamine and leyukotrine D4 make the airways twitchy
- Twitchy smooth muscle (hyper-reactivity) - Twitchy
How can you treat/prevent these steps in the cascade?
- Genetic predisposition + Triggers (allergens, chemical etc) - Avoidance
- Eosinophilic Inflammation - Corticosteriods, anti-inflammatory
- Mediators, TH2 cytokines - anti-histamines, anti-leukotrines etc
- Twitchy smooth muscle - Bronchodilators, Ba agonists,, Muscarinic antagonists
Talk about the tip of the iceberg in terms of asthma?
Symtoms/Exacerbations - are visible etc
Airflow obstruction
Bronchial hyperresponsiveness - possible to measure but time consuming
Airway inflammation - hard to test this, can measure amount of NO in breath, or eosinophils in blood
What type of basement membrane is found in normal airways?
Pseudostratified
Describe some of the main feature of asthma clinically?
Episodic symptoms and signs
Diurinal variability – nocturnal/early morning
Non-productive cough, wheeze
(Triggers)
Associated atopy ( rhinitis , conjunctivitis, eczema)
Family history of asthma
Wheezing due to turbulent airflow
How can you diagnose asthma?
History and examination Peak flow Reduced FE ratio < 75% Reversibilty using salbutamol Provocative tresting - causing bronchospams
Name the 3 main components in COPD?
Mucociliary dysfunction
Inflammation
Tissue damage
What happens to the alveolar attachments which hold open the airways in emphysema?
They are disrupted and collapse
Describe the disease process in COPD?
- Cigarette smoke and other irritants activate macrophages and airway epithelial cells in the respiratory tract which release neutrophil chemotactic factors, including interleukin 8 (IL-8)and leukotriene B4.
- Neutrophils and macrophages then release proteases that break down connective tissues in the lung parenchyma (emphysema) and also stimulate mucus hypersecretion (chronic bronchitis)
- Proteases are normally counteracted by protease inhibitors such as α1-antitrypsin, secretory leukoprotease inhibitor (SLPI) and tissue inhibitors of matrix metalloproteinases.
- Cytotoxic T cells (CD8+ lymphocytes) may also be involved in the inflammatory cascade, possibly through involvement in the destruction of alveolar wall epithelial cells.
- In COPD there appears to be an imbalance between proteases and antiproteases (either an increase in proteases, or a deficiency of antiproteases) which lead to inflammatory changes in the airways including damage of the respiratory mucosa.
Describe the characteristics of Chronic bronchitis?
Chronic neutrophilic inflammation Mucus hypersecretion Mucociliary dysfunction Altered lung microbiome Smooth muscle spasm and hypertrophy Partially reversible
Describe the characteristics of emphysema?
Alveolar destruction
Impaired gas exchange
Loss of bronchial support
Irreversible
Describe the characteristics of COPD?
Chronic symptoms - not episodic Smoking Non-atopic Daily productive cough Progressive breathlessness Frequent infective exacerbations Chronic bronchitis- wheezing Emphysema- reduced breath sounds
