Asthma Flashcards
Define Asthma
“Asthma is a chronic inflammatory disorder of the airways.
inflammatory symptoms are usually associated with widespread but variable airflow obstruction and an increase in airway responsiveness to a variety of stimuli
difference in airway obstruction in COPD and asthma
the airway obstruction in Asthma is often reversible
the airway obstruction in COPD is not fully reversible -
how is asthma classified?
ATOPIC & NON-ATOPIC
atopic> evidemce of allergen sensitization, often in patients w/ a histroy of allergic rhinitis and eczema
Non-atopic> w/ out evidence of allergen sensitization,
different catagories of asthma and examples for each
Atopic asthma > allergen induced (oftem gave FH of asthma)
Non-atopic> non allergen, cause by respiratory infections
Drug-induced> aspirin and NSAIDS
Occupational> fumes (plastics) chemical dusts ( wood, cotton, platinium)
how does aspirin induce asthma?
inhibit the cycloxygenease pathway of AA w/ OUT AFFECTING THE LIPOXYGENEASE ROUTE!
thus tipping the balance toward the elaboration of bronchoconstrictor leukotrines
Pathophysiology of ASthma
Asthma is a chronic inflammatory process driven by Th2 cells
Macrophages process and present antigens to T lymphocytes.
This ‘activates’ T cells, with TH2 cells being preferentially activated.
TH2 cells release cytokines, which attract and activate inflammatory cells, including mast cells and eosinophils. TH2 cells also activate B cells, which produce IgE
sensitized atopic asthmatic, exposure to antigen results in a
2 phase response :
name them
immediate response (reaching max in about 20 mins) followed by a late phase response ( 3 – 12 hours later).
what is immediate response caused by?
is an example of type 1 hypersensitivity.
It is caused by interaction of the allergen & specific IgE antibodies, leading to mast cells degranulation and release of mediators (histamine, tryptase, prostaglandin D2 and leukotriene)
which cause bronchial smooth muscle contraction lading to bronchoconstriction.
describe Late phase response
an example of type 4 hypersensitivity.
involved in recruitment of inflammatory cells:
- eosinophils,
- mast cells,
- lymphocyte
- neutrophils
which release mediators and cytokines, which cause airway inflammation.
leukocyte recruitment is stimulated by the chemokines produced by the mast cells.
this 2nd wave of mediators stimulates the late reaction.
what major substance does eosinophils release?
what does this cause?
release Leukotriene C4 and other mediators, some of which are toxic to epithelial cells
causes shedding of epithelial cells. !!!
(Eosinophils are very sensitive to steroid therapy).
how does the the air way inflammation causes reduced airway calibre (airway narrowing) ?
due to what ?
- Mucosal swelling (oedema) due to vascular leak,
- Thickening of bronchial walls due to infiltration of inflammatory
- cells
- Mucous over production; the mucus is also abnormal- it is thick, tenacious & slow moving. The cough is therefore usually dry or only productive of scanty, white sputum. In severe cases many airways are occluded by mucus plugs.
- Smooth muscle contraction
- The epithelium is shed and is incorporated into the thick mucus
The inflammation also causes hyper responsiveness of airways.
what does this mean?
Because of airway hyper-responsiveness, non-allergic stimuli like cold air & fumes can also trigger attacks
in nonatopic asthma, respiratory infection like (rhinovirus, parainfluenza virus) r common triggers in non atopic asthma.in these patient hyperirritability of the bronchial tree probably lies in their asthma.
what can Long term poorly controlled asthma lead to?
can lead to airway remodelling some of which may not be fully reversible.
Long term poorly controlled asthma, can lead to airway remodelling some of which may not be fully reversible.
The changes include?
The changes include:
hypertrophy & hyperplasia of smooth muscle,
hypertrophy of mucus glands
thickening of the basement membrane .
Effect of airways narrowing on spirometry & symptoms?
- causes wheezing & other clinical features of asthma
- results in an obstructive pattern on Spirometry (↓ FEV/FVC ratio < 70% ) & typical flow volume loops; which shows reversibility with bronchodilators, or over a period of time
- air trapping with increased RV
how is asthma classified?
what r Asthma Triggers ?
Allergens - pollen, animals (animal hair/dander), house dust, faeces
Cold air
exercise
fumes - Car exhaust
cigarette smoke
perfumes
chemicals - Isocyanates and acid anhydrides (varnish/paint)
drugs - NSAIDS and beta blockers
emotional distress;
symtoms of asthma
and signs in examination
Treatment of asthma?
treatment of acute asthma attack
Physical examination finding of asthma
The most frequent finding is wheezing on auscultation, especially
on forced expiration
Wheezing may be absent during severe asthma exacerbations
(‘silent chest’)
How can we measure Airway inflammation
(3)
What can cause Breathlessness?
acute and chronic
(Think differential diagnosis!)
Differemt cells in copd and asthma
