Asthma Flashcards
What is asthma?
-chronic lung condition
-chronic inflam of airways
-airway hypersensitivity
-variable airflow limitation
Describe the main proccess involved with asthma
-bronchoconstriction
-inflammation
-mucus
What are the asthma phenotypes?
-extrinsic - allergic
-intrinsic- non allergic
What is extrinsic asthma?
-atopic individuals
-genetic component ( ADAM33 and PHF11 genes)
-immune system mediated
-produce IgE antibodies to many common allergerns
-inflam mediated by systemic IgE production
What is intrinsic asthma?
-non identifiable triggers
-middle aged onset
-local inflamm
-also includes occupational asthma, food induced and aspirin induced asthma
Describe the cellular mechanisms of asthma
-inflam cascade
-many rather than one disease entity
-main immune cells incolved are mast cells and eosinophils
-mast cells produce may mediators including histamise, LTs, PGs which have a direct effect on bronchial smooth muscle, bronchospams
-eosinophils, late phase response, leukotriene B4 and C4- bronchospasm
Describe the pathophysiology of asthma with the activation of Th2 cells
-inhaled allergen engulfed by submucosal dendritic cells which attract and activate Th2 cells
-Activated Th2 cells release a host of cytokines and interleukins:
ILI3 and IL14 stimulate IgE antibody production from B cells, which bind to mast cells
IL9 stimulate mast cell production and activation
IL5 promotes eosinophil production from bone marrow
-chemoattractants draw eosinophils to lungs
Describe the pathophysiology of asthma when the allergen binds to IgE
-allergen binds to IgE/mast cell comples resulting in degranulation, releasing inflam mediators- histamine, leukotrienes and prostaglandins
-mast cell mediators result in bronchoconstriction, increased airway secretion and increased vascular permeability
-immediate and rapid response to allergen exposure
-a late phase reaction occurs 6-8 hrs post allergen exposure, mediated by eosinophils, monocyes and lymphocytes - results in long lasting inflam
Describe airway hyperresponsiveness
twitchy airways- react to otherwise harmless substances
leads to- airway inflam, eosinophilia,bronchospasm/bronchoconstriction, mucous hypersecretion
Describe airway remoddeling in asthma
due to chronic inflam
-smooth muscle cell hyperplasia
-goblet cell hyperplasia
-epithelial basement membrane thickening
-bronchial hyper-responsiveness
-poorer clinical outcomes
Describe lung function in asthma
obstructive spiro when symptomatic
-increased airway resistance
-normal or increased TLC
-raised reiducal volume
-normal or increased TLco
-blood gases normal except during an attack
-spiro may be normal if patient is assymptomatic
What is a key diagnostic feature of asthma?
if airway obstruction is present then it may be reversible if bronchodiators are given
Name the inhaled bronchodilators used to treat asthma
-Beta 2 agonists (salbutamol)
-anticholenergic (ipratropium bromide)
SABA, LABA, SAMA, LAMA
how do beta 2 agonists help with asthma ?
-smooth muscle relaxation, cause dilation of bronchial passages and vasodilation
What are glucocorticosteroids?
-usually taken every day by inhaler
-examples- beclomethasone,flucticasone
-can be given orally as prednisolone tablets for severe asthma
-in acute severe asthma steroids can be given intravenously
Name some side effects of glucocorticosteroids
-severe asthmatics may need large oral doses of steroids for long periods
-may cause cushingoid side effects related to changes in metabolism of fats, proteins and carbs
-fear of long term effects with very high oral doses and patient may not use their steroid inhalers
