Definition of Asthma
A chronic inflammatory condition of the airways characterized by bronchial constriction. It is associated with atopy
Name some triggers of asthma - 7
- pollen
- pets
- dust
- smoke
- cold weather
- exercise
- NSAIDs
Pathophysiology of Asthma
This chronic inflammation is caused by 2 responses:
Immediate – a type 1 hypersensitivity reaction caused by IgE antibodies recognizing antigens and causing mast cell degranulation. This leads to bronchoconstriction
Late Phase – a type 4 hypersensitivity reaction where eosinophils, mast cells, lymphocytes and neutrophils are released and cause chronic inflammation.
Risk factors of asthma - 5
- FH
- PMH of atopy (often associated with atopic triad of asthma, allergic rhinitis and atopic eczema)
- maternal smoking
- viral infections
- lower socioeconomic status
Symptoms of asthma - 4
- wheeze
- dyspnoea
- cough (worse at night due to raised PNS activity)
- chest tightness
Signs of Asthma - 5
- Tachypnoea
- hyperinflated chest
- hyper-resonance on percussion
- decreased air entry
- wheeze on auscultation
Investigations of Asthma
- Spirometry
- Peak Flow diary
- Bloods - IgE and Eosinophils raised
- CXR - to exclude other causes of wheeze
- Fractional exhaled nitric oxide
Positive spirometry results
Will indicate obstructive lung disease findings:
* reduced FEV1
* Reduced FEV1:FVC ratio (will be less than 0.7)
These should be performed before and after a bronchodilator - after the BD, results should be normal.
Positive Peak Flow Diary Results
At least 20% variablity after monitoring twice daily for 2-4 weeks
Positive Fractional Exhaled Nitric Oxide Results and why is it done
This looks at the NO in a single exhaled breath, as NO is a marker for eosinophilic inflammation in lungs
An NO level of over 40ppb is positive
Differentials of Asthma - 8
- Bronchiectasis
- COPD (smoker, productive cough)
- Cystic Fibrosis
- GORD
- Heart failure
- Lung cancer
- TB
- Pertussis
Non pharmacological management of asthma - 3
- smoking cessation
- avoidance of triggers
- review inhaler technique
Pharmacological stepwise approach to Asthma management - 4
- SABA (salbutamol)
- low dose ICS (beclometasone)
- add LABA (salmeterol). If no benefit, stop and increased ICS dose
- Trial of oral leukotriene receptor antagonist (montelukast) , high-dose steroid, oral beta agonist and oral theophylline
ADRs of Beta Agonists - 5
- Tremor
- palpitations
- headache
- anxiety
- hypokalaemia
Signs of an acute asthma exacerbation - 3
- difficulty breathing
- tachypnoea
- wheeze
Signs of a Severe Asthma Attack - 4
- inability to finish sentences
- respiratory rate is >25
- peak flow is 33-50% of baseline
- HR >110bpm
Signs of a life threatening asthma exacerbation - 6
- Peak flow <33% of baseline
- a silent chest
- confusion or drowsiness
- Cyanosis
- Hypotension
- Bradycardia
These pts should be urgently admitted to intensive care
Investigations of acute asthma
- Blood test (FBC, CRP) - to look for cause of attack e.g. infection
- CXR - to exclude pneumothorax or consolidation
- ABG - respiratory alkalosis is expected
Management of an acute asthma exacerbation - 6
- ABCDE approach
- Ensure patent airway
- Nebulisers - salbutamol or ipratropium
- Steroids - oral prednisalone or IV hydrocortisone
- IV magnesium sulphate
- IV aminophylline
