Asthma Flashcards
What is the definition of Asthma?
a Common REVERSIBLE chronic disorder of airways that is complex and characterized by variable and recurring symptoms of airflow obstruction: bronchial hyperresponsiveness and inflammaiton
*reversibility distinguishes it from COPD
what are the symptoms of Asthma?
dyspnoea, cough and wheeze
How do we diagnose Asthma?
History, Examination, Investigations
- history of resp. symptoms
- physical examination
- demonstration of variable expiratory airflow obstruciton
what is the hygiene hypothesis?
Normally: child in womb has Th2 CD4 lymphocytic response (Type 1 hypersensitivity) to antigens that converts to a Th1 CD4 T lymphocytic response upon repeated exposure to antigens in neonatal life.
Hygiene Hypothesis: lack of stimulation by antigenic exposure results in a maintenance of Th2 hypersensitivity response to antigens throughout life = never converts to Th1 response.
What are the chronic effects of asthma?
poorly controlled asthma leads to a chronic thickening of the basement membrane and the destruction of the epithelial layer
destruction of the epithelial layer leads to a chronic inflammatory infiltrate
why are asthmatic symptoms more common at night?
because of the diurnal pattern of airway caliber = more bronchial narrowing at nightime
What result would we see on spirometry in someone with Asthma?
due to airway blocking, we see a reduced FEV1, decreased FEV1/FVC ratio, reduced Peak expiratory flow rate, and lower overall FVC
*key difference is that it’s reversible - try the methacholine challenge
describe the immunopathology of asthma
- allergen exposure
- mast cells in lumen/epithelium activated by allergen - release mediators
- mediators initiate acute reaction including bronchospasm = airflow obstruction
- quiescent CD4 Th2 lymph. become activated by cytokines secreted by allergen-stimulated cells = initiate more chronic inflammatory process
- Th2 cells secrete IL4 and IL5
- IL4 initiates B lymphocyte IgE release
- IgE amplifies mast cell event
- negative regulation of Th2 cells by Th1 and regulatory T cells is impaired in asthma
- IL5 activates eosinophils which induce acute inflammation
what auscultatory finding do we find in an asthmatic emergency?
Silent Chest
what is atopic triad?
a family history/personal history of
atopic dermatitis
seasonal allergic rhinitis (hay fever)
and conjunctivitis
This atopic triad favors a diagnosis of asthma in patients with suggestive symptoms
what type of wheeze do we hear in asthma?
polyphonic - multiple tone wheeze
what tests do we do to confirm an asthma diagnosis?
Bronchodilator response (positive selection) - with salbutamol
Bronchial provocation tests (negative selection) - with histamine or metacholine challenge
Allergen Challenge -
what is the first line drug in an asthma attack?
SABA
short acting beta 2 agonists
like salbutamol or terbutaline
these are beta 2 selective and adrenergic agonists
They are recommended for use AS NEEDED
what is a LABA and why do we never put patients exclusively on a LABA?
LABA= long acting beta 2 agonist ex) Salmeterol or formoterol
- similar specific bronchodilatory effect of SABAs but sustained fo more than 12 hours
- never give a LABA without corticosteroids b/c shown increased risk of death in patients who only use LABAs - this is due to muscle hypertrophy of the basement membrane over time - eventually the LABA won’t do anything for you it’s just chronic inflammation
Why do we use inhaled corticosteroids in Asthma?
b/c of anti-inflammatory activities
and
decreased cumulative inflammatory effects on airway: fewer mast cells, eosinophils, reduced hyperplasia and epithelial cell injury
Also, nonspeicific bronchial hyperresponsiveness decreases
*they suppress inflammation- not curative
Describe treatment steps in asthma classes
least severe asthma (step 1) = SABA as needed
Most severe asthma (Step 5)
= SABA + anti IgE treatment
