Asthma Flashcards
What are the three main characteristics of asthma?
- airflow limitation
- airway hyper-responsiveness
- inflammation of the bronchi
what is intrinsic asthma?
often starts in middle age, sometimes called late onset asthma. no trigger can be identified
what does atopy mean?
term used to describe people who have allergies / asthma / hayfever and where the trait runs in families.
How do you test for airway hyper-responsiveness?
bronchial provocation test - ask patient to gradually inhale increasing amounts of methacholine or histamine, this will induce transient airflow limitation in 20% of the population - these patients exhibit airway hyper-responsiveness
what is non-atopic asthma associated with?
recurrent respiratory tract infections
what is bronchoconstriction in non-atopic asthma due to?
airway hyper-responsiveness
why is aspirin thought to induce asthma?
due to increased leukotrienes and decreased prostaglandings, which leads to increased airway irritability
which job professions are susceptible to occupational asthma?
bakers, electrician, carpenter, painter, working with polyurethane
which foods can cause asthma attacks?
high sodium and low magnesium
what will exposure of antigen in asthma do to CD4 T cells?
differentiate into T helper cells (Th2 type) and they will begin to secrete IL-4 and IL-5
what will IL-4 and IL-5 do in asthma?
IL-4 will cause B cells to become plasma cells and begin secreting IgE
IL-5 will act on eosinophils and mast cells, making them reactive to the new antigen. other factors are also released which are chemotaxic for eosinophils
what happens to mast cells upon re-exposure?
mast cell will be activated and will degranulate. this will release inflammatory markers
what is there an increase in the lungs of asthmatics?
number of mast cells in both the airway secretion, and the epithelial lining of lung - therefore increased response to any antigen
what is a asthma attack a result of?
histamine and prostaglandin (as well as leukotrienes; particularly LTC4) released by mast cells.
what does histamine do?
causes smooth muscle contraction, increased bronchial secretions and increased vascular permeability
what is a late phase reaction of asthma causes by?
the accumulation of eosinophils at the site.
what is the effect of cold air and exercise on asthma?
both dry out mucosa of the lung, which makes the lining hyperosmolar. this causes mast cells to release histamine and prostaglandins, thus causing inflammation
what is the effect of a diet high in fruit and vegetables on asthma?
protective, possibly due to large amounts of anti-oxidants
what is the ADAM33 gene?
thought to be the gene responsible for release of factors by eosinophils. these factors can cause remodelling of the epithelium and stimulate growth of fibroblasts. this increases airway hyper-responsiveness
what are the clinical features of asthma?
- wheezing attacks
- periodic SOB
- symptoms often worse at night
- cough is frequent
- nocturnal cough alone sometimes
- some patients can have chronic symptoms
what two tests are most useful for a diagnosis of asthma?
PEFR and Spirometry
what other respiratory function tests may be done?
carbon monoxide transfer test and NO (levels are raised in breath of asthmatics)
what test is used to often diagnose asthma in children?
exercise test
which test is very useful for children at first presentation?
trial of corticosteroids
