Asthma Flashcards
Describe the pathophysiology of the immediate phase of the allergic reaction. (3)
- Trigger enters the body is taken up by antigen presenting cells, which present it to T cells
a. T cells produce inflammatory mediators, esp. IL-4 and IL-33
b. T cells stimulate IgE production, causing allergy - Trigger stimulates degranulation of mast cells
a. This furthers the inflammatory allergic response - Inflammation in the airway causes increased resistance
a. This causes decreased airflow in the lungs
Describe the pathophysiology of the delayed phase of the allergic reaction. (1)
- Trigger enters the body and is taken up by antigen presenting cells, which present it to T cells
a. T cells produce IL-12 and IFN
b. This causes a delayed inflammatory response
How would you define asthma? (3)
HINT: There are 3 aspects.
CLINICAL DEFINITION:
- Appropriate signs and symptoms
- Episodic symptoms
- Triggered symptoms
- Variable/paroxysmal presentation
- Response to asthma therapies
PHYSICAL DEFINITION:
- Reversible airflow obstruction
- Airway hyper-responsiveness
PATHOLOGICAL DEFINITION:
- Airway inflammation
- Airway hyper-responsiveness
- Airway smooth muscle hypertrophy
List 5 symptoms of asthma.
Wheeze Cough Yellow/clear sputum Breathlessness Exercise intolerance
How do you test airway hyper-responsiveness? (2)
Give a small dose of histamine/methacoline/mannitol
Measure when the airways start to narrow - in asthma, this will happen sooner than in normal lungs
Which inflammatory cells are involved in airway inflammation in asthma? (4)
Neutrophils
Macrophages
Eosinophils
Lymphocytes
What are the different inflammatory phenotypes of asthma? (4)
Eosinophilic (3+% eosinophils)
Neutrophilic (61+% neutrophils)
Paucigranulocytic
Mixed
Which investigations would you do to diagnose asthma? (4)
Peak flow (serial tests)
Bronchial hyper-responsiveness test
Reversibility tests
Allergy tests
How do you do reversibility tests for asthma? (3)
Measure spirometry tests
Give a bronchodilator (usually salbutamol)
Re-measure spirometry tests
Significant difference:
- More than 15% difference
- More than 400ml difference
How would you treat chronic asthma? (2)
- Lifestyle changes, e.g.
a. Smoking cessation
b. Avoid triggers
c. Check inhaler technique
d. Written action plan - Asthma drugs
Describe the 5 steps of the treatment ladder for asthma.
STEP 1:
SABA as required
STEP 2:
Add inhaled steroid, e.g. beclamethasone
STEP 3: Add LABA, e.g. salmeterol If ineffective, trial: -Leukotriene receptor antagonist -Oral theophylline
STEP 4:
Trial increased steroid dose
Trial modified-release oral theophylline
STEP 5:
Add regular oral prednisolone
Refer to asthma clinic
Describe the mechanism of action of theophylline. (2)
- Inhibits phosphodiesterase
- This increases CAMP levels, therefore decreasing bronchoconstriction
a. This causes bronchodilation
Theophylline has a narrow therapeutic range.
What can theophylline toxicity cause? (3)
Arrhythmias
GI upset
Fits
What other drug may be used in prophylaxis of mild or exercise-induced asthma? (1)
Cromoglicate
Give 2 examples of leukotriene receptor antagonists.
Montelukast
Zafirlukast
What other drug might an asthma specialist give in persistent asthma?
Omalizumab (anti-IgE monoclonal antibody)
Describe the mechanism of action of leukotriene receptor antagonists. (2)
- Inhibit CystLT1 receptor in the airways
a. This reduces bronchoconstriction - Also reduces inflammation
How would you treat a non-severe, acute asthma attack? (3)
Nebulised salbutamol (5mg) Oxygen Oral prednisolone (30mg)
What are the features of a severe acute asthma attack? (4)
Inability to complete sentences
HR: 110+
Resp. rate: 25+
Peak flow: 33-50% predicted
What are the features of a life-threatening asthma attack? (5)
Silent chest Confusion Exhaustion Cyanosis ABG results: pO2 <8.0; pCO2 4.6-6.0; O2 sats <92%
How would you treat a severe, acute asthma attack? (6)
Assess severity of attack
Warn ICU; patient will need admission
Administer:
- Nebulised salbutamol (5mg)
- Oxygen (if sats are <92%)
- IV hydrocortisone (100mg)
- Oral prednisolone (40-50mg)
How would you treat a life-threatening asthma attack?
- Nebulised salbutamol (5mg), repeat every 15 minutes
- Nebulised ipratropium (0.5mg)
- IV magnesium sulphate (1.2-2g over 20 minutes)
- Monitor ECG for arrhythmias
What investigations would you do in A&E for someone presenting with an acute asthma attack? (5)
PEF (if patient is fit enough) Sputum culture Blood tests: FBC, U&Es, CRP, blood cultures Arterial blood gases CXR
Describe the signs O/E of uncontrolled chronic asthma. (6)
Tachypnoea Audible wheeze Hyperinflation Hyper-resonant percussion Decreased air entry Widespread, polyphonic wheeze
