Obstructive: Asthma Flashcards
What is Asthma?
Reversible airway bronchoconstriction (COPD)
- Allergic stimuli (type 1 hypersensitivity reaction)
- Generally presents in childhood
- Often associated with allergic rhinitis, eczema, and family history of atopy
Explain the pathogenesis of Asthma (type 1 hypersensitivity)
Patient gets exposed to allergens
Induces the TH2 phenotype in CD4+ T cells of genetically susceptible individuals
TH2 cells secrete IL-4, IL-5 and IL-10 (classic cytokines released)
- IL-4:
allows plasma cell to switch to IgE– mediates allergic reaction - IL-5:
attracts eosinophils - IL-10:
inhibits production of TH1 helper cells and induces production of TH2 helper cells, helping to promote this overall reaction
What happens to an individual upon re-exposure to an allergen?
Mast cells have surface IgE
Allergen cross-links to surface IgE, activating mast cell
- (Early phase) –
Causes IGE-mediated activation of mast cells and releases histamine granules - Resulting in histamine-induced vasodilation (occurring at arterioles)
And increased vascular permeability (and leaking of fluid occurs at the post-capillary venule)
- Mast cells perpetuate inflammation by producing leukotrienes – C4, D4, E4
These C4 D4 E4 do various things including –
- Vasoconstriction of SM of BV,
- Increase vascular permeability (oedema) by constricting the pericytes (wrap around capillaries and venules throughout body) and cause
- Bronchoconstriction
- Inflammation (e.g. major basic protein derived from eosinophils) perpetuates bronchoconstriction (late phase reaction)
Name types of allergens
Pollen
Dust
Food
Molds
Name some clinical features and findings of asthma
- Dyspnoea
- Wheezing
- Tachypnoea
- Hypoxemia
- Decreased inspiratory/expiratory ratio
- Pulsus paradoxus - abnormally large decrease in stroke volume, systolic blood pressure and pulse wave amplitude during inspiration – more than 10mmHg
- Mucus plugging
- Productive cough
- DLCO is normal or increased
Explain the histological contents of a productive cough in ASTHMA
Productive cough contains Curschmann spirals -
(spiral shaped mucus plugs)
And Charcot-Leyden crystals
(CL crystals hexagonal, double-pointed crystals formed from breakdown of eosinophils in sputum)
These show up in mucus, can see on slide
How does asthma appear on a microscopic examination of bronchial biopsy?
Mucus plugs
Hypertrophy of mucus glands
Goblet cell hyperplasia
Oedema
Hypertrophy and hyperplasia of bronchial wall smooth muscle
Thickened basement membrane
What does a severe unrelenting asthma attack result in?
Status asthmaticus (most extreme form of asthma) - Results in - Hypoxemia - Hypercapnia - Secondary respiratory failure
Eventually leads to
DEATH
What are the non-allergic causes of asthma?
- Exercise
- Viral infection
- Stress
- Cold temperatures
- Aspirin
- Occupational exposures
What is the pathophysiology of the non-atopic cause of asthma with ASPIRIN? (HY)
Can be a combination of COX inhibition
leukotrienes overproduction = airway constriction (e.g. aspirin intolerant asthma
They get aspirin induced bronchospasm and nasal polyps
Adult with chronic sinusitis and nasal polyps = aspirin intolerant asthma
Child with nasal polyps = Cystic fibrosis
What is the diagnosis for asthma?
- Spirometry
- Methacholine challenge - type of bronchoprovocation test used to help diagnose asthma.
Methacholine is an inhaled drug that causes mild narrowing of the airways in the lungs, like asthma.
Considered positive if methacholine causes a 20 percent or greater decrease in your breathing ability when compared to your baseline.
A positive test suggests that your airways are “reactive,” and a diagnosis of asthma should be considered.
What is the treatment for asthma?
Control of triggers
Drug therapy e.g.
- Bronchodilators (beta-2 agonists, anticholinergics)
- Corticosteroids
- Leukotriene modifiers
- Mast cell stabilizers
Monitoring
Patient education
Treatment of acute exacerbation’s
