Asthma Flashcards
Define bronchial asthma.
A chronic inflammatory disorder characterised by hyperreactive airways, airway inflammation and reversible airflow obstruction leading to episodic reversible bronchoconstriction
What are the different kind of asthma?
Extrinsic (atopic) - response to inhaled antigen
Intrinsic (non-atopic) - non-immune mechanisms (cold weather, exercise, drugs)
Multifactorial - bit of both
What kind of hypersensitivity is asthma?
Type 1
What happens in asthma?
Allergen binds to IgE on mast cell and degranulation occurs. Histamine is released with other inflammatory markers.
What do histamine and the other inflammatory markers cause?
- muscle spasm - bronchoconstriction (wheeze)
- mucosal inflammation - mucosal oedema and increased secretions (sputum)
- inflam cell infiltrate - infiltration of lymphocytes and eosinophils (yellow sputum)
Give some pathological features of asthma.
Narrowed oedematous airways
Mucus plugs – secretions are increased
Inflammatory cells (lymphocytes, plasma cells, eosinophils)
Epithelial cell damage
When does asthma present in life?
early or late onset
What is the clinical syndrome of asthma?
- episodic signs and symptoms
- diurnal variation
- non-productive cough
- wheeze
- shortness of breath
- chest tightness
- associated atopy (hayfever, eczema, conjunctivitis)
FH of asthma or atopy
How is a diagnosis of asthma made?
- suspicion must be gained from history before preceding to tests
- PEFR (2x daily monitoring for obvioouos diurnal variation)
- Spirometry - obstructive pattern then >15% improvement in FEV1 or PEF following inhaled salbutamol
- Exercise tests - diagnose asthma in children
What is the treatment for an acute exacerbation of asthma?
- Oxygen
- Salbutamol nebulised high dose
- Hydrocortisone IV (or oral if can take orally)
- Ipratropium bromide nebulised
- Magnesium IV
- Theophylline IV
- Anaesthetist
What is step 1 of the BTS asthma guideline?
Avoidance of allergen!
Inhaled Salbutamol PRN
if using twice i one week then step up
What is step 2 of the BTS asthma guideline?
Add inhaled corticosteroid beclometasone
What is step 3 of the BTS asthma guideline?
Add LABA inhaled Salmeterol
What is step 4 of the BTS asthma guideline?
Add leukotriene receptor anatgonist Montelukast, or ora theophylline or oral B2 agonist
What is step 5 of the BTS asthma guideline?
Add regular oral steroid Prednisolone
What is step 6 of the BTS asthma guideline?
Refer to asthma clinic
They may give Omalizumab (suppresses mast cell degranulation response to allergens)
How do B2 adrenoceptor agonists work?
Give 2 examples of this drug
Salbutamol and Salmeterol
increase cAMP to relax bronchial smooth muscle within minutes
increase mucous clearance & decreased inflam mediator release from mast cells & neutrphills
How do corticosteroids work?
Give 2 examples of this drug
Beclometasone and Prednisolone
- Decrease formation of Th2 cytokines and cause apoptosis
- prevent production of IgE antibodies
- prevent allergen induced influx into lung and cause apoptosis
- reduce number of mast cells and decrease Fce expression
How do Xanthines work?
Give an example of this drug
inhibit phosphodiesterase leading to decreased bronchoconstriction and increased cAMP levels
What do Xanthines have that require something to be done about it?
Narrow therapeutic index
blood test required 4-6hours after infusion started
How do cysteinyl leukotriene receptor antagonists work?
Give an example of this drug
Montelukast
anatgonise CystLT1 receptor, blocking the effects of cysteinyl leukotrienes in the airways therefore relaxing bronchial smooth muscle
How does airway smooth muscle remodel in asthma?
undergoes hypertrophy and hyperplasia leading to a larger fraction of the wall being occupied by smooth muscle tissue. The deposition of repair collagens and matrix proteins below the basement membrane further thickens the airway wall.
Which drugs can cause the wheeze in asthma?
NSAIDs
Aspirin
B-blockers
Which drug is absolutely contraindicated in a patient with asthma?
B-blocker
Patients with acute severe asthma typically have what?
inability to complete a sentence in one breath
RR > 25 breaths per min
HR >110bpm
PEFR 33-50% of predicted
Features of life threatening asthma.
Silent chest, cyanosis, feeble respiratory effort
exhaustion, altered conscious level
bradycardia or hypotension
PaO2 <33% predicted
What is the initial treatment of acute severe asthma?
salbutamol by oxygen driven nebuliser
When is exercise induced asthma maximal?
5-10 minutes after the end of exercise
