Asthma Flashcards
Define asthma
- chronic airway inflammation
- cough, wheeze, breathlessness
- variable outflow obstruction
- airways hyper-responsiveness
Symptoms
Wheeze
breathlessness
Chest tightness
Cough
Different phenotypes of asthma
- allergic
- non allergic
- adult onset (late)
- asthma with persistent airflow limitation
- with obesity
Sympathetic action of respiratory system
Beta 2 receptors
Bronchodilation
Mucociliary clearance
Parasympathetic action of respiratory system
Muscarinic receptors
Bronchoconstriction
What surrounds bronchioles
Terminal and respiratory bronchioles surrounded by SM
What holds large airways open
Cartilage
What does flow =
pressure change/resistance
What is flow increased by?
- increased pressure change
- decreased resistance
Pouseille’s Law
Flow = 1/resistance^4
Decreased resistance = increased flow
What do mast cells cause in the acute phase?
Bronchospasm
Oedema
Mucous
What happens in the late phase?
Th2 helper cells activate B cells to produce IgE and eosinophils
- these cause bronchoconstriction and muco-secretion
Extrinsic causes
- air pollution
- allergen exposure
- maternal smoking
- hygiene hypothesis
- genetics
Intrinsic causes
- non-allergic
- less responsive
- colds/infections
Occupational causes
- allergens at work
Diagnosis
- clinical
- Evidence of airflow obstruction or airway inflammation
- respiratory symptoms, signs and test results
- absence of alternative explanation for presentation
Symptoms and presentation
Wheeze Breathlessness Chest tightness Cough Worse at night and morning Triggers Atopic features FH Low PEFR or FEV
What triggers it?
Allergens Exercise Cold air Aspirin Beta blocker
Less likely symptoms/presentation
- dizziness/light – headedness/peripheral tingling
- productive cough in absence of wheeze of breathlessness
- normal exam when breathless
- voice disturbance
- symptoms with colds
- smoking history >20 pack years
- cardiac disease
- normal PEF or FEV1 when symptomatic
Wheeze differentials
Asthma COPD Obstruction = foreign body Anaphylaxis Pulmonary oedema
Bronchodilator reversibility
> 12% or 200ml improvement in FEV1
Spirometry results
FEV1/FVC<70%
- may be normal when not symptomatic
Fraction exhaled nitric oxide
> 40 ppb
breath test marker of eosinophilic inflammation
Direct Challenge Testing
- drop in FEV! when exposed to provoking substance
- concentration required for 20% fall in FEV1 of 8mg/ml or less
Peak Flow
- twice daily readings over 2 weeks
- diurnal variation
- 20% variability
Diagnostic test
Peak Flow Spirometry Bronchodilator reversibility Fraction exhaled nitric oxide Direct challenge testing IgE Allergy/skin prick testing FBC/eosinophil count
Treatment
- patient education and self management plan
- avoidance of triggers and allergens = smoking
- weight reduction
- breath exercises
- stepwise approach
What is not recommended
- house dust mite avoidance
- air ionisers
When should patients be reviewed post discharge
<30 days if admitted
usually by specialist nurse
Drug treatment
- short and long acting B2 agonists
- corticosteroids
- leukotriene antagonists
- Anti-IgE monoclonal antibodies
MOA of B2 agonists
Sympathetic action of B2 receptors = bronchodilation and mucociliary clearance
- relax SM
- relieve bronchospasm
Example of short acting B2 agonist
Salbutamol
Terbutaline
Example of long acting B2 agonist
Salmeterol
Formoterol
Side effects of beta 2 agonists
Tremor
Tachycardia
Sweats
Agitation
Mechanism of action of corticosteroid
decrease inflammation
Examples of corticosteroids
Budesonide
Beclometasone
Fluticasone
Side effects of corticosteroids
Oral candidiasis
Systemic rare with inhaled corticosteroids
MOA of leukotriene antagonists
- block leukotriene receptors in SM
- reduce bronchoconstriction
Examples of leukotriene antagonists
Montelukast
Side effects of leukotriene antagonists
Nausea
headache
Example of Anti-IgE
omalizumab
subcutaneous
Side effects of Anti-IgE
- itching
- joint pain
- headache
- nausea
- anaphylaxis
Indications for anti-IgE
- confirmed allergic IgE mediated asthma
- add on to optimised standard therapy
- continuous/frequent treatment with oral corticosteroids (4 or more)
Stepwise treatment
- short acting B2 agonist
- inhaled corticosteroid low dose
- regular preventer
- add LABA to low dose ICS and offer LTRA
- increase ICS dose or add LTRA, consider stopping LABA if no response
- MART, increase ICS OR fixed dose ICS/LABA + SABA then LAMA or theophylline
How much to reduce ICS?
25-50% reduction in dose every 3 months consider if not getting worse
Define uncontrolled asthma
- 3 ore more days a week with symptoms
OR - 3 or more days a week with required use of SABA for symptomatic relief
OR - 1 ore more nights a week with awakening due to asthma
Risk of future attacks in children
- comorbid atopic conditions
- younger age
- obesity
- exposure to environmental tobacco smoke
Risk of future attacks in adults
- older age
- female
- reduced lung function
- obesity
- smoking
- depression
Asthma control assessment
- scored 5-25
- 25 = complete control
- ACT score >19 indicates well controlled asthma
Precipitating factors to acute asthma
- pets
- exercise
- pollen
- bugs in home
- chemical fumes
- cold air
- fungus spores
- dust
- smoke
- strong odors
- pollution
- anger
- stress
Brittle asthma
- 2 types
- difficult to control
- unstable/unpredictable
Type 1 brittle asthma
- wide PEF variability
- > 40% diurnal variation for >50% of time period >150 days
- despite intense therapy
Type 2 brittle asthma
- sudden severe attacks on background of apparently well controlled asthma
Moderate acute asthma
- increasing symptoms
- no features of acute severe
- PEF >50-75% best or predicted
Acute severe asthma
Any 1 of
- PEF 33-50%
- RR 25>/min
- HR 110/min>
- inability to complete sentences in 1 breath
Life threatening asthma
Any 1 of
- PEF <33%
- Sats <92%
- PaO2 <8
- Silent chest
- Cyanosis
- hypotension
- exhaustion
- feeble respiratory effort
- tachy or bradycardia
- dysrhythmia
- confusion
- coma
What to do if life threatening asthma
Call anaesthetist
When to admit in acute asthma
- if acute severe persisting after treatment or > life threatening
Near fatal asthma
- raised PaCO2 and/or requiring mechanical ventilation with raised inflation pressures
When to discharge in acute asthma
- PEF>75% after 1 hour
- unless = symptoms significant, compliance concerns, live alone, psychological problems, previous near fatal/brittle asthma, pre-existing steroids, night time, pregnant
Management of acute asthma
- high flow oxygen
- aim sats >92%
- O2 driven nebs
- IV fluids
- reassess every 15 mins with PEFR
Drugs on management of acute asthma
OSHIT
- oxygen
- salbutamol
- hydrocortisone/prednisolone
- ipratropium bromide
- theophylline
- magnesium sulphate
Dose for salbutamol in acute
- 2.5-5mg every 10 mins
- nebulised with oxygen
Side effects of salbutamol
- tremor
- arrhythmias
- hypokalemia (monitor ECG)
Hydrocortisone dose in acute
- IV 100-200mg QDS
- or prednisolone PO 40mg OD
Ipratropium bromide dose in acute
500mg every 4-6 hours
Side effects of ipratropium bromide
- arrhythmias
- cough
- dizziness
- dry mouth
- headache
- nausea
Magnesium sulphate dose in acute
1.2-2g over 20 mins IV
For acute severe
Side effects of theophylline
- palpitations
- arrhythmias
- nausea
- seizures
- alkali burns if extravasation occurs
- drug interactions
When to involve ITU?
- If require ventilatory support
- near fatal asthma
- life threatning/acute severe not improving
- early
Monitor In acute asthma
- peak flow reg.
- ox sats
- chest auscultation
- ABG repeat 1hr?
- potassium and glucose bloods
- ECG = potassium, Mg, beta 2 agonists
When to repeat ABG every hour?
- hypoxic
- normo-hypercapnoeic
- patient deteriorates
Acute asthma follow up
- within 48 hours
- <30 days post discharge by GP/nurse specialist
- under specialist supervision for near fatal asthma
- at least 1 year for severe asthma attack
