Asthma Flashcards
What is the pathophysiology of asthma?
Airway hyperresponsiveness is triggered by environmental factors
- Activation of Th2 cells results in eosinophil Activation, IgE production and mast cell degranulation
- This causes a reversible airflow obstruction
What are the risk factors for asthma?
History of atopy
Family history
Exposure to allergens
Occupational exposure
What are the typical triggers for asthma?
Infection
Nighttime or early morning
Exercise
Animals
Cold, damp or dusty air
Strong emotions
What are the clinical features of asthma?
Episodic shortness of breath - diurnal variation
Dry cough
Wheeze
Chest tightness
What are the primary investigations for asthma?
Fractional exhaled nitric oxide (FeNO)
Spirometry and bronchodilator reversibility
Peak flow diary
What FeNO level is indicative of asthma?
> 50ppb
What peak flow variability is indicative of asthma?
> 20%
What spirometry results are indicative of asthma?
An FEV1:FVC ratio of less than 70%
What are the presenting features of an acute asthma exacerbation?
Progressive shortness of breath
Use of accessory muscles
Tachypnoea
Symmetrical expiratory wheeze
What are the features of a moderate asthma exacerbation?
Peak flow 50-75% of best
What are the features of a severe asthma exacerbation?
Peak flow 33-50% of best/predicted
RR > 25
HR > 110
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What are the features of a life-threatening asthma exacerbation?
PEFR < 33%
SpO2 < 92%
PO2 < 8
PCO2 normal
Altered consciousness
Exhaustion
Arrhythmia
Hypotension
Silent chest
What are the features of a near-fatal asthma attack?
High pCO2
What investigations are helpful in an acute asthma exacerbation?
PEFR
ABG
Inflammatory markers - look for infective trigger
CXR - hyperexpansion/infection
What is the initial management of an acute asthma exacerbation?
Admission - all patients with life-threatening asthma
Oxygen
Bronchodilation - SABA
40-50mg oral prednisolone
Ipratropium bromide nebulisers if not responding or if life-threatening asthma
What is the further management of an acute asthma exacerbation?
IV magnesium sulfate
IV aminophylline
ICU admission
What is the criteria for discharge in acute asthma exacerbation?
Have been stable on their discharge medication for 12-24 hours
Inhaler technique checked and recorded
PEF > 75% of best or predicted
What is the first line management of asthma?
Low dose ICS/formoterol combination inhaler (AIR therapy)
What is the second line management of asthma?
Low dose MART (combined ICS/formoterol taken daily and as required)
What is the third line management of asthma?
Moderate dose MART
What is the fourth line management of asthma?
Check the FeNO level and eosinophil count
- If either of these is raised, refer to specialist
- Consider trial of leukotriene receptor antagonist or LAMA
