Asthma Flashcards
What is the prevalence of asthma?
adults 10-12%
children 15%
What is the hygeine hypothesis?
early childhood infections alter the immune response by directing T cell differentiation towards TH1 phenotype and away from TH2 (allergy causing)
What are the risk factors for asthma?
allergy
atopy
family history
smoke exposure - smoker or passive
What is the main inflammatory response in asthma?
TH2 response - IL4, IL5, IL13
What are some triggers for asthma?
allergen exposure (house dust mite, animal dander etc.) infection - viral URTI Cold air inhaled irritants B-blockers stress excercise
Clinical features of asthma?
cough - dry or productive dynsnoea wheeze - mostly expiratory chest tighness symptoms occur more at night
Diagnosis of asthma?
clinical picture
spirometry with reversibility and bronchial challenge (if indicated
- FEV1/FVC less then 0.7
- reversibility greater then 12% and improvement of FEV1 by 200mls
What is a bronchial challenge?
administer bronchoconstricting substance (methacholine, histamine etc.)
FEV1 should decrease by 20% or more to have a positive test
often done in those with normal spirometry to confirm diagnosis
Features of exercise induced bronchospasm
occurs a few minutes after intense excercise
peaks 5-10 minutes after and resolves within 30 minutes
due to dryness and cooling of airways with increased ventilation
treat with prior b-agonist or leukotriene blocker
Features of vocal cord dysfunction?
prominent wheezing on inspiration and heard loudest over throat
can co-exist with asthma
monophonic wheeze (compared with polyphonic in asthma)
abrupt onset and termination
flow volume loop - inspiration part of loop flat (form of variable extrathoracic obstruction)
What are some conditions that may lead to poor asthma control?
Non compliance rhinosinusitis GORD mycloplasma/chlamidia pneumonia aspirin/nsaids/b-blockers pre-menstral phase hypo or hyperthyroidism vocal cord dysfunction
What is aspirin sensitive asthma?
1-5% of asthmatics are exacerbated by COX inhibitors
Samter triad of severe asthma, aspirin sensitivity and nasal polyps
What is the treatment for aspirin sensitive asthma?
Refer for de-sensitisation (only indication for desensitization testing in asthma)
What is the treatment ladder for asthma?
SABA PRN
Low dose ICS
Low dose ICS + LABA
Medium dose ICS + LABA
High does ICS + LABA + consider omiluzumab
High dose ICS + LABA + oral steroids + consider omulizumab
What is the caution with LABA in asthma?
Should never be started without ICS as can mask symptoms and increase mortality
What is Omalizumab?
antibody against Fc portion of IgE
neutralises circulating IgE and reduces asthma exacerbations
ADR: risk of anaphylaxis
What is lebrikizumab?
monoclonal antibody against IL 13
reduced exacerbations
What are leukotriene inhibitors?
Montelukast
block leukotriene receptors and reduce bronchoconstricting effect
useful add on therapy - good in excercise induced bronchospasm
Less effective then ICS for reducing inflammation
What happens in pregnancy with asthma?
1/3 get better
1/3 get worse
1/3 stay the same
What is the classification of asthma?
Intermittent - symptoms less then 2 days a week
Persistent
Mild: symptoms greater then 2 days per week with SABA use more then 2 days per week
Moderate: daily symptoms and SABA use
Severe: daily symptoms, nightly awakenings, SABA use throughout day
When is ICS use indicated?
For all other categories except for mild intermittent
- shown to reduce permanent airway re-modelling if started early
Treatment of acute asthma exacerbation?
Moderate PEF 40-69% - bronchodilator via spacer, increase reliever, oral steroids 5-7 days, can be managed as OP if stable Severe PEF less then 40% - inh b-agonist (as good as nebs) - oral steroids (as good as IV) - magnesium (broncodilator) - oxygen to keep sats greater than 90 - early intubation
How do inhaled corticosteroids work to prevent inflammation in asthma?
switches off trascription of activated genes that encode inflammatory proteins, reduces inflammatory cell recruitment and activation
What is theophylline?
Oral bronchodilator
Inhibits phosphodiesterase in smooth muscle which increases cAMP and bronchodilates
What are some negatives of theophylline?
ADRs are common at dose required to achieve bronchodilation
N+V, headache, dizziness, arrythmias, seizures
multiple drug interactions as metabolised by CYP
