Asthma Flashcards
(49 cards)
What is asthma?
Chronic inflammation of airways and hyper responsiveness which causes narrowing of airways
Causes of asthma
Genetic factors (family history)
Environmental factors
Triggering substance of asthma
- air pollution: cigarette smoke, car fumes
- allergens: dust, animals, mould, pollen
- medication: aspirin (NSAIDs), beta blockers
- cold air
Symptoms of asthma
- dry cough (often at night)
- chest tightness
- dyspnoea
- wheezing/high pitched whistling on exhalation on
Why is a dry cough in asthma more common at night?
Increased vagal activity at night
What investigations can be used to diagnose asthma?
- Peak flow + diary
- Spirometry (<70%) + reversibility testing
- FeNO
- direct bronchial challenge test
What is bronchial challenge test?
- patient breathes in powder that irritates airways
- patient’s breathing is tested after each dose to see how much the airways narrow
- dose is increased until breathing ability drops by <20% or max dose is reached
diagnosis of asthma
- spirometry with bronchodilator reversibility: <70% + improvement of >12% with bronchodilators
- FeNO: >50ppb adults | >35ppb kids
Outline the fractional exhaled nitric oxide test for investigation of asthma
What result would support diagnosis?
Why could it be unreliable?
- measures the conc. of NO exhaled (marker for airway inflammation)
- steady exhale for around 10s into device
- > 50ppb is a positive test
- smoking lowers FeNO so could be unreliable in smokers
Management of asthma
- education
- up to date vaccinations
- avoid triggers
- drug treatment: bronchodilators + steroids
- inhalers
New asthma medication guidelines
- first line: AIR therapy: low dose ICS + formoterol combination PRN
- second line: low dose MART
- third line: moderate dose MART
- if still uncontrolled and good adherence + technique: check FeNO level + eosinophil
- if not raised: trial addition of LTRA or LAMA for 8-12 weeks
- if still uncontrolled: refer to specialist
New asthma guidelines in children 5-11 years old
**
What is AIR therapy + MART?
- AIR: anti-inflammatory reliever - PRN
- MART: maintenance and reliever therapy - everyday + during an attack
- use of ICS/formoterol therapy
Why have the asthma management guidelines changed?
risks of SABA overuse
How do you grade asthma exacerbation severity?
mild:
- no features of severe asthma
- PEFR >75% of best or predicted
moderate:
- no features of severe asthma
- PEFR 50-75%
severe: (any one of)
- PEFR 33-50%
- cannot complete sentences in 1 breath
- RR >25
- HR >110
life threatening: (any one of)
- PEFR <33%
- sats <92% or ABG pO2 <8kPa
- cyanosis, poor resp effort or near/fully silent chest
- exhaustion, confusion, hypotension or arrhythmias
near fatal:
- all of above but raised pCO2
How do you manage an acute asthma exacerbation?
- oxygen (aim for 94-98%)
- 2.5-5mg nebulised salbutamol (repeat after 15mina if needed)
-
40mg oral prednisolone
. - if severe, 500mg nebulised ipratropium bromide
. - if life threatening or near fatal:
- urgent ITU, portable CXR + anaesthetist assessment
- IV aminophylline
- consider IV salbutamol if nebulised route ineffective
What class of drug is aminophylline + what is its mechanism of action?
Methylxanthine class
- it inhibits phosphodiesterase > increased cAMP in smooth muscle cells > bronchodilation
- also has anti-inflammatory effects
What does the term controlled oxygen refer to?
Who typically needs it?
- the administration of O2 at specific conc. or flow rate to achieve a target O2 saturation
- key in patients with COPD (risk of CO2 retention)
Key aspects: - precise control of O2 delivery
- monitoring O2 sats
- prevention of complications e.g. hypercapnia
Criteria for safe asthma discharge post exacerbation
- PEFR >75%
- stop regular nebulisers 24hrs prior to discharge
- reassess inhaler technique + adherence
- written asthma action plan
- at least 5 days oral prednisolone
- GP follow up within 2 days
- resp clinic follow up within 4 weeks
What is an asthma management plan?
A written document designed for each individual with asthma to help control their symptoms + reduce exacerbations
Components:
- daily treatment instructions
- monitoring + symptoms tracking e..g peak flow diary
- action plan for exacerbations
Blue vs brown inhalers
Blue: bronchodilator acts a reliever (short term)
Brown: anti inflammatory (corticosteroids) to reduce risks of asthma attacks (longer term)
Describe how asthma attacks happen and what process take place in the body
- triggered by something in th environment
- picked up by dendritic cells
- present to type 2 helper cells - CD4+
- cytokines releases (IL-4+IL5)
- IL-4: production of IgE antibodies > coat mast cells and stimulate the release of histamines, leukotrienes + prostaglandins
- IL-5: act on eosinophils > release more cytokines + leukotrienes
- causes smooth muscle spasm + increased mucous secretion
- also increased vascular permeability > immune cells from blood > eosinophils damage endothelium of lung
- airways become even narrower
What immune cells are in involved asthma?
Type 2 helper cells
B cells > plasma cells > antibodies
What is the atopic triad?
Asthma
Atopic dermatitis
Allergic rhinitis
