RESP 210 Asthma Flashcards
How do you define asthma?
Chronic inflammatory disorder of the airways characterised by airway hyper-responsiveness that is reversible either spontaneously or with treatment
What are the two types of asthma?
Extrinsic and Intrinsic
Describe extrinsic asthma
Atopic or occupational
IgE mediated with a definite extrinsic cause
Describe intrinsic asthma
No definite cause
Usually develops later in life and is more progressive
What is the general overview of the pathophysiology of asthma?
Bronchial hyper-sensitivity to an antigen and bronchial inflammation which can cause an inflammatory plug
Describe the process of a Type 1 - hypersensitivity reaction
1st exposure to the allergen: detected by dendritic cells which display it to T helper cells
Th2 cells release cytokines that stimulate B-cells to produce IgE
IgE attaches to mast cells
2nd exposure the antigen on the allergen cross links with IgE on the mast cells
= mast cell degranulation
What the fuck is released on mast cell degranulation? What is the result of this?
histamine, prostaglandins and leukotrienes
Bronchoconstriction, increased mucous production and microvascular leakage
Which cytokine stimulates eosinophillic differentiation and what does this result in? (Asthma week)
IL5 = epithelial damage, loss of tight junctions and smooth muscle contraction
What happens to the sub-mucosa in asthmatics with airway remodelling?
It becomes expanded with deposition of matrix proteins and cells making it easier for airways to close with even the slightest smooth muscle contraction
What happens to the epithelium in asthmatics with airway remodelling?
Loss of cilliated columnar cells
Increased mucus secreting goblet cells
Increased NO synthase
Increased susceptibility to infection therefore
What happens to the epithelial basement membrane in asthmatics with airway remodelling?
Deposition of repair collagens and proteoglycans here
Thickened due to activation of fibroblasts
What are the clinical features of asthma?
Recurrent wheeze Breathless ness Cough Chest tightness diurnal variation Reversibilty
How might a severe attack of asthma present?
tachycardia
hyper expanded chest
silent chest +bradycardia = ominous
what investigations would you perform in an asthmatic?
Peak flow
Spirometry and skin prick test for allergens
What would you see on Spirometry in asthma?
Obstructive pattern flow loop
<70% FEV1/FVC ratio
Low FEV1
Low peak expiratory flow rate
