Obstructive Airway Disease Overview Flashcards
What is an obstructive respiratory disease?
Affects the airways
What is a restrictive airway disease?
Affects the lungs
What are some examples of obstructive airway diseases?
- Asthma
- COPD
- Chronic bronchitis (COPD)
- Emphysema (COPD)
What is asthma?
Allergic inflammatory reaction which is usually reversible
What is chronic bronchitis (COPD) caused by?
Smoking
What is chronic bronchitis characterised by?
Neutrophil inflammation
What is emphysema (COPD)?
Emphysema is a condition which causes airflow obstruction but is not a disease of the conducting airways (disease of respiratory airways - alveoli)
What is ACOS?
Asthma/COPD overlap syndrome
* Long-standing cigarette smokers who have features of both asthma and COPD
Which airways become inflamed in asthma?
Both large airways (trachea, bronchi) and small airways (bronchioles, terminal bronchioles, alveolar ducts/sacs)
What are large airways?
Diameter larger than 2mm
- Trachea
- Bronchi
What are small airways?
Diameter less than 2mm
- Bronchioles
- Terminal bronchioles
- Alveolar sacs
Where does the conducting zone end and acinar zone begin?
After 17 generation (division)
What is the conducting zone?
Where gas transport takes place
What is the acinar/respiratory zone?
Where gas exchange takes place
What airways make up the conducting zone?
- Trachea
- Bronchi
- Bronchioles
What airways make up the acinar/respiratory zone?
- Terminal bronchioles
* Alveolar sacs
How many levels of branching does the respiratory tree undergo?
23
At what point in the respiratory tree do large airways become small airways?
After 7th generation
How does COPD cause airway obstruction?
- Contraction of smooth muscle causes airway to constrict
* Alveolar walls keep respiratory tree open - COPD results in destruction of alveolar walls and bronchial tree collapse
What is atopic asthma?
Individual experiences attacks in response to allergens
What is non-atopic asthma?
Individual does not experience attacks in response to allergens
What is extrinsic asthma?
Has an external trigger factor e.g. allergen, chemical, environmental pollution
What is intrinsic asthma?
No external trigger factor
What are the 3 points the characterise asthma?
- Airway inflammation (characterised by presence of eosinophils)
- Airway hyper responsiveness
- Reversible airflow obstruction
What characterises asthmatic inflammation?
Eosinophils
What characterises inflammation caused by chronic bronchitis (COPD)?
Neutrophils
What is airway hyper responsiveness?
Airway becomes sensitive to a variety of abnormal stimuli
What does chronic airway inflammation result in?
- Exacerbation
* Airway hyper-responsiveness
What does airway remodelling result in?
Fixed airway obstruction
What does airway remodelling involve?
Repair of airways by laying down collagen - permanent obstruction
How is basement membrane remodelled in asthma?
Thickening
How is submucosa remodelled in asthma?
Collagen deposition
How is smooth muscle remodelled in asthma?
Hypertrophy
What is airway epithelium?
Pseudostratified columnar epithelium
Which T cell is involved in asthma?
TH2
What leukotrienes do TH2 release?
- IL-4 to activate B cells
- IL-13 - used in addition to IL-4 to cause mast cells to express IgE receptors
- IL-5 to activate/recruit eosinophils
What are eosinophils used for?
- To fight parasites
* Allergic responses
What do eosinophils release in an asthmatic response?
- Basic/catatonic proteins
- Leukotrienes
- Cytokines
What is the role of IgE released by B cells?
Bind to IgE receptors on mast cells, activating them
What are useful targets for asthma?
- IgE
- IL-5
- Leukotriene D4 (activate more TH2 cells)
- Histamine (released by mast cells)
What is used to treat eosinophilic inflammation?
Anti-imflammatory medication
- Corticosteroids
- Cromones
- Theophylline (a methylxanthine)
What treatments are used to target mediators or TH2 cytokines?
- Anti-leukotrienes
- Antihistamines
- Monoclonal antibodies
- Anti-IgE
- Anti interleukin-5
What is used to treat hyper-reactivity (twitchy smooth muscle)?
Bronchodilators
- B2 agonists
- Muscarinic antagonists
What is an example of a B2 agonist?
Adrenaline/epinephrine
Are B2 agonists ever given alone?
No, paired with corticosteroids
Why are corticosteroids the main asthma treatment?
Only treatment proven to reduce inflammation, swelling, and mucus production in the airways
What are examples of triggers that symptoms of asthma can occur or worsen in the presence of?
- Allergens
- Exercise
- Viral infection
- Smoke
- Cold
- Chemicals
- Drugs (NSAIDs, B-blockers)
(B-blockers would result in constriction of the airways)
What are the signs and symptoms of asthma?
- Episodic symptoms and signs
- Diurnal variability
- Non-productive cough
- Associated atopy (eczema, conjunctivitis, rhinitis)
- Blood eosinophilia >4%
- Wheezing due to turbulent airflow
Why is it important to take history before testing for asthma?
Due to diurnal variability - if test at points in the day where episodes do not occur, will not have wheeze
How is asthma diagnosed?
- History and examination
- Diurnal variation of peak flow rate (see-saw pattern)
- Reduced forced expiratory ratio (FEV1/FVC <75%)
- Reversibility to salbutamol
- Provocation testing - bronchospasms (via exercise, histamine/metacholine/mannitol)
What are the 3 components of COPD (Chronic Obstructive Pulmonary Disease)?
- Inflammation (characterised by neutrophils)
- Tissue damage
- Mucocilliary dysfunction
What is COPD caused by?
Smoking
What are the characteristics of COPD?
- Exacerbations
* Reduced lung function
What are the symptoms of COPD?
- Breathlessness
* Worsening quality of life
How do the airways of someone with COPD differ to normal airways?
- Mucous hyper-secretion (lumen obstruction)
- Disrupted alveolar attachments (emphysema)
- Mucosal and peribronchial inflammation and fibrosis (obliterative bronchiolitis)
Describe the disease process of COPD
- Cigarette smoke and other irritants activate macrophages and airway epithelial cells in the respiratory tract
- Macrophages release neutrophil chemotactic factors - IL-8 and Leukotriene B4
- Neutrophils and macrophages then release proteases
- Proteases destroy alveolar wall (emphysema) and result in mucous hyper secretion (chronic bronchitis)
What cells other than macrophages and neutrophils may also be involved in the COPD inflammatory cascade?
CD8+ T cells - involvement in destruction of alveolar wall
Why does the COPD inflammatory cascade not occur in normal individuals?
Proteases normally counteracted by protease inhibitors
What are examples of protease inhibitors?
- a1 - antitrypsin
- Secretory leukoprotease inhibitor (SLPI)
- Tissue inhibitors of matrix metalloproteinases
Why do protease inhibitors fail to work in COPD?
In COPD there appears to be an imbalance between proteases and antiproteases (either an increase in proteases, or a deficiency of antiproteases)
What 2 conditions does COPD comprise?
- Chronic bronchitis
* Emphysema
What is chronic bronchitis?
Chronic neutrophilic inflammation
What are the characteristics of chronic bronchitis?
- Mucous hypersecretion
- Mucocilliary dysfunction
- Altered lung microbiome
- Smooth muscle spasm and hypertrophy
- Partially reversible
What does emphysema involve?
Alveolar wall destruction
What are the characteristics of emphysema?
- Impaired gas exchange
- Loss of bronchial support
- Irreversible
Are chronic bronchitis and emphysema reversible?
- Chronic bronchitis - partially reversible
* Emphysema - irreversible
Why can some individuals smoke for years and never develop COPD?
Genetics - higher antiprotenase production
How is COPD assessed?
- Assess symptoms
- Assess degree of airflow limitation using spirometry
- Assess risk of exacerbations
- Assess co-morbitdities e.g. Ischaemic heart disease (IHD) and heart failure (HF)
What are indicators of high risk in COPD?
- 2 exacerbations or more in the past year
* FEV1 <50%
What is the ABCD assessment tool for COPD?
- A - less exacerbations, less symptoms
- B - less exacerbations, more symptoms
- C - more exacerbations, less symptoms
- D - more exacerbations, more symptoms
What are the symptoms of COPD?
- Chronic symptoms - not episodic
- Non-atopic
- Daily productive cough
- Progressive breathlessness
- Frequent infective exacerbations (worsening of symptoms triggered by viruses etc)
- Chronic bronchitis- wheezing
- Emphysema - reduced breath sounds
What can a chronic cascade of COPD result in?
- Progressive fixed airflow obstruction
- Impaired alveolar gas exchange
- Respiratory failure: decrease in PaO2, increase in PaCO2
- Pulmonary hypertension
- Right ventricular hypertrophy/failure (i.e. Cor Pulmonale)
- Death
How can further decline in lung volume in COPD be arrested?
Stopping smoking
What are characteristics of Asthma COPD Overlap Syndrome (ACOS)?
- COPD with blood eosinophils >4%
- Responds better to inhaled corticosteroids (ICS)
- More reversible to salbutamol
Why is it difficult to distinguish between COPD and asthmatic smokers?
Asthmatic smokers may have airway remodelling i.e. reduced FVC
Are asthma and COPD atopic?
Asthma - can be atopic
COPD - non-atopic
Are asthma and COPD early onset?
Asthma - early or late onset
COPD - late onset
Are asthma and COPD chronic?
Asthma - episodic symptoms
COPD - chronic symptoms
Are asthma and COPD progressive?
Asthma - non-progressive
COPD - progressive
What type of cough is seen in asthma and COPD?
Asthma - non-productive
COPD - productive
DO asthma and COPD have diurnal variability?
Asthma - diurnal variability
COPD - no diurnal variability
Do asthma and COPD respond to corticosteroids and bronchodilators?
Asthma - good corticosteroid and bronchodilator response
COPD - poor corticosteroid and bronchodilator response
How does FVC and TLCO vary in asthma and COPD?
- Asthma - preserved FVC and TLCO
* COPD - reduced FVC and TLCO
How is gas exchange affected in asthma and COPD?
- Asthma - normal gas exchange
* COPD - impaired gas exchange
What are non-pharmalogical treatments for COPD?
- Stopping smoking
- Immunisation (exacerbation on infection)
- Physical activity
- Oxygen
- Venesection
- Lung volume reduction
- Stenting
What are pharmacological treatments of COPD?
- LAMA or LABA mono
- LABA/LAMA combo
- ICS/LABA combo
- ICS/LABA/LAMA combo
(LABA - long acting beta-adrenoceptor agonist)
(LAMA - long acting muscarinic antagonists)
- PDE4I - Roflumilast
- Mucolytic - Carbocisteine
- Antibiotics - Azithromycin