Asthma Flashcards
What is asthma?
Asthma is a chronic inflammatory condition of the airways that causes episodic exacerbations of bronchoconstriction.
Typical triggers of an exacerbation of asthma
- Infection
- Night time or early morning
- Exercise
- Animals
- Cold/damp
- Dust
- Strong emotions
Presentation suggesting a diagnosis of asthma
- Episodic symptoms
- Diurnal variability. Typically worse at night.
- Dry cough with wheeze and shortness of breath
- A history of other atopic conditions such as eczema, hayfever and food allergies
- Family history
- Bilateral widespread “polyphonic” wheeze heard by a healthcare professional
Presentation indicating a diagnosis other than asthma
- Wheeze related to coughs and colds more suggestive of viral induced wheeze
- Isolated or productive cough
- Normal investigations
- No response to treatment
- Unilateral wheeze. This suggests a focal lesion or infection.
First line investigations for asthma
- Fractional exhaled nitric oxide
- Spirometry with bronchodilator reversibility
Asthma - if there is diagnostic uncertainty after first line investigations these can be followed up with further testing:
- Peak flow variability measured by keeping a diary of peak flow measurements several times per day for 2 to 4 weeks
- Direct bronchial challenge test with histamine or methacholine
Long term managment of asthma (NICE guidelines 2017)
- Add short-acting beta 2 agonist inhaler (e.g. salbutamol) as required for infrequent wheezy episodes.
- Add a regular low dose inhaled corticosteroid.
- Add an oral leukotriene receptor antagonist (i.e. montelukast).
- Add LABA inhaler (e.g. salmeterol). Continue the LABA only if the patient has a good response.
- Consider changing to a maintenance and reliever therapy (MART) regime.
- Increase the inhaled corticosteroid to a “moderate dose”.
- Consider increasing the inhaled corticosteroid dose to “high dose” or oral theophylline or an inhaled LAMA (e.g. tiotropium).
- Refer to a specialist.
Action of short acting beta 2 adrenergic receptor agonists, for example salbutamol
Adrenalin acts on the smooth muscles of the airways to cause relaxation. This results in dilatation of the bronchioles and improves the bronchoconstriction present in asthma. They are used as “reliever” or “rescue” medication during acute exacerbations of asthma when the airways are constricting.
Action of Inhaled corticosteroids (ICS), for example beclomethasone
These reduce the inflammation and reactivity of the airways. These are used as “maintenance” or “preventer” medications and are taken regularly.
Action of long-acting muscarinic antagonists (LAMA), for example tiotropium.
These block the acetylcholine receptors. Acetylecholine receptors are stimulated by the parasympathetic nervous system and cause contraction of the bronchial smooth muscles. Blocking these receptors leads to bronchodilation.
Action of leukotriene receptor antagonists, for example montelukast.
Leukotrienes are produced by the immune system and cause inflammation, bronchoconstriction and mucus secretion in the airways. Leukotriene receptor antagonists work by blocking the effects of leukotrienes.
Action of Theophylline
This works by relaxing bronchial smooth muscle and reducing inflammation. Unfortunately it has a narrow therapeutic window and can be toxic in excess so monitoring plasma theophylline levels in the blood is required. This is done 5 days after starting treatment and 3 days after each dose change.
How does Maintenance and Reliever Therapy (MART) work?
This is a combination inhaler containing a low dose inhaled corticosteroid and a fast acting LABA. This replaces all other inhalers and the patient uses this single inhaler both regularly as a “preventer” and also as a “reliever” when they have symptoms.
Presentation of an acute exacerbation of asthma
- Progressively worsening shortness of breath
- Use of accessory muscles
- Tachypnoea
- Symmetrical expiratory wheeze on auscultation
- The chest can sound “tight” on auscultation with reduced air entry
Grading acute asthma - moderate
- PEFR 50 – 75% predicted
