Asthma Flashcards
What changes to the airway wall is seen in asthma?
Thickening of smooth muscle and basement membrane
Damaged epithelium
What is asthma?
A chronic condition characterised by
- airway wall inflammation
- airway wall remodelling
- reversible airflow obstruction
- increase in airway responsiveness to various stimuli
What happens to airflow when triggers cause airway smooth muscle to contract and why?
Reduced airway radius
Increased resistance
Reduced airflow
Risk factors for asthma?
Genetic risk Hygiene hypothesis Sensitisation to airborne allergens such as -pollution -house dust mites -pollen -tobacco smoke
Triggers of airway smooth muscle contraction?
Histamine
Muscarinic agonists
Cold air
Arachidonic acid metabolites such as prostaglandins and leukotrienes
Symptoms of asthma?
Wheeze
Dry cough - worse at night and can cause lack of sleep, poor performance at school
Breathlessness with exercise
Chest tightness
What is a wheeze?
A high pitched, EXPIRATORY sound
Originates in airways narrowed by compression or obstruction
Can be of variable intensity and tone
Examinations for asthma?
Inspection - look for hyperexpansion (Barrel chest), general health - eczema, hay-fever, lethargy, can they speak?
Percussion- will be hyper-resonant
Auscultation - polyphonic wheeze
How does spirometry help in diagnosis asthma?
Produce a flow volume loop
Have a low peak expiratory flow rate (can’t breathe out quickly)
Low FEV1/FVC a ratio
What happens to the FEV1/FVC ratio after administration of salbutamol?
See a greater than 12% increase
What allergy testing can be done in aiding diagnosis of asthma?
Skin-prick to aero-allergens of eg
Cat, dog, house dust mites,
Look at blood IgE level,s for specific aero-allergens
Why are chest X-Rays used in the diagnosis of asthma?
Can exclude other diseases, inhalation of foreign body, pneumothorax
In the pathophysiology of asthma, what does exposure to the antigen cause?
CD4 T cells differentiate into T helper cells
Secrete IL-4 and IL-5
What do IL-4 and IL-5 do?
IL-4: causes B cells to differentiate into plasma cells and secrete IgE
IL-5: makes eosinophils and mast cells reactive to new antigen
What does IgE do?
Binds to mast cells in the mucosa
Waits to come into contact with the antigen again
On re-exposure, mast cells are activated and de-granulate to release inflammatory mediators
What inflammatory mediators are released by mast cells?
Histamine
Prostaglandins
Leukotrienes
What does histamine do in an asthma attack?
Smooth muscle contraction
Increased vascular permeability
Why do asthmatics have an increased response to antigens?
Increased number of mast cells in their airway secretions and epithelial linings of lungs
What is the late phase reaction?
Due to collection of eosinophils and neutrophils
More sustained inflammation, less bronchoconstriction
How does remodelling of the airways occur?
Epithelium is stressed and damaged with the loss of ciliated columnar cells
Deposition of collagen causes basement membrane to thicken
Smooth muscle undergoes hyperplasia - thickening
Precipitating factors for asthma attacks?
Can occur spontaneously Lack of treatment adherence Respiratory virus infections associated with common cold Exposure to allergen Exposure to a triggering drug eg NSAID
How can education be used in the treatment of asthma?
So patients can recognise symptoms
Use medication timely
Use services appropriately
Develop a personal asthma action plan
How can asthma be prevented?
Stop smoking
Fresh air
Reduce exposure to allergens and triggers
Weight loss
Pharmacological management of asthma?
β2 adrenoagonists
Muscarinic antagonists to provide short term relief eg salbutamol
Anti-inflammatory agents eg corticosteroids
Preventer therapies
