Asthma

Question 1

What is asthma?

Answer 1

Asthma is a chronic inflammatory condition of the airways that causes episodic exacerbations of bronchoconstriction.

Question 2

Typical triggers of an exacerbation of asthma

Answer 2

• Infection
• Night time or early morning
• Exercise
• Animals
• Cold/damp
• Dust
• Strong emotions

Question 3

Presentation suggesting a diagnosis of asthma

Answer 3

• 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

Question 4

Presentation indicating a diagnosis other than asthma

Answer 4

• 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.

Question 5

First line investigations for asthma

Answer 5

• Fractional exhaled nitric oxide
• Spirometry with bronchodilator reversibility

Question 6

Asthma - if there is diagnostic uncertainty after first line investigations these can be followed up with further testing:

Answer 6

• 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

Question 7

Long term managment of asthma (NICE guidelines 2017)

Answer 7

1. Add short-acting beta 2 agonist inhaler (e.g. salbutamol) as required for infrequent wheezy episodes.
2. Add a regular low dose inhaled corticosteroid.
3. Add an oral leukotriene receptor antagonist (i.e. montelukast).
4. Add LABA inhaler (e.g. salmeterol). Continue the LABA only if the patient has a good response.
5. Consider changing to a maintenance and reliever therapy (MART) regime.
6. Increase the inhaled corticosteroid to a “moderate dose”.
7. Consider increasing the inhaled corticosteroid dose to “high dose” or oral theophylline or an inhaled LAMA (e.g. tiotropium).
8. Refer to a specialist.

Question 8

Action of short acting beta 2 adrenergic receptor agonists, for example salbutamol

Answer 8

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.

Question 9

Action of Inhaled corticosteroids (ICS), for example beclomethasone

Answer 9

These reduce the inflammation and reactivity of the airways. These are used as “maintenance” or “preventer” medications and are taken regularly.

Question 10

Action of long-acting muscarinic antagonists (LAMA), for example tiotropium.

Answer 10

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.

Question 11

Action of leukotriene receptor antagonists, for example montelukast.

Answer 11

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.

Question 12

Action of Theophylline

Answer 12

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.

Question 13

How does Maintenance and Reliever Therapy (MART) work?

Answer 13

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.

Question 14

Presentation of an acute exacerbation of asthma

Answer 14

• 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

Question 15

Grading acute asthma - moderate

Answer 15

• PEFR 50 – 75% predicted

Question 16

Grading acute asthma - severe

Answer 16

• PEFR 33-50% predicted
• Resp rate >25
• Heart rate >110
• Unable to complete sentences

Question 17

Grading acute asthma - life threatening

Answer 17

• PEFR <33%
• Sats <92%
• No wheeze. This occurs when the airways are so tight that there is no air entry at all. This is ominously described as a “silent chest”.
• Haemodynamic instability (i.e. shock)

Question 18

Treatment of moderate acute asthma

Answer 18

• Nebulised beta-2 agonists (i.e. salbutamol 2.5mg repeated as often as required)
• Nebulised ipratropium bromide (500 micrograms, maximum 2mg per day)
• Steroids. Oral prednisolone or IV hydrocortisone. These are continued for 5 days
• Antibiotics if there is convincing evidence of bacterial infection

Question 19

Treatment of severe acute asthma

Answer 19

• Oxygen if required to maintain sats 94-98%
• Aminophylline infusion
• Consider IV salbutamol

Question 20

Treatment of life threatening acute exacerbation of asthma

Answer 20

• IV magnesium sulphate infusion
• Admission to HDU / ICU
• Intubation in worst cases – however this decision should be made early because it is very difficult to intubate with severe bronchoconstriction

Question 21

ABGs in acute exacerbation of asthma:

Answer 21

Initially patients will have a respiratory alkalosis as tachypnoea causes a drop in CO2. A normal pCO2 or hypoxia is a concerning sign as it means they are tiring and indicates life threatening asthma. A respiratory acidosis due to high CO2 is a very bad sign in asthma.

Question 22

How would you monitor the effect of treatment of an acute exacerbation of asthma?

Answer 22

• Respiratory rate
• Respiratory effort
• Peak flow
• Oxygen saturations
• Chest auscultation

Question 23

Side effects of salbutamol

Answer 23

• moves potassium into cells - monitor serum potassium
• tachycardia