Asthma: a very basic introduction

Question 1

Asthma: a very basic introduction?

Answer 1

• It affects over 10% of children and around 5-10% of adults, with the prevalence of asthma increasing.
• Not only does asthma account for a significant morbidity burden it should be remembered that around 1,000 people die in year from asthma in the UK, 30-40 of whom are children.

Question 2

What is asthma?

Answer 2

• Defined as a chronic inflammatory disorder of the airways secondary to hypersensitivity.
• The symptoms are variable and recurring and manifest as reversible bronchospam resulting in airway obstruction.

Question 3

Risk factors and aetiology?

Answer 3

A number of factors can increase the risk of a person developing asthma:

• personal or family history of atopy
• antenatal factors: maternal smoking, viral infection during pregnancy (especially RSV)
• low birth weight
• not being breastfed
• maternal smoking around child
• exposure to high concentrations of allergens (e.g. house dust mite)
• air pollution
• ‘hygiene hypothesis’: studies show an increased risk of asthma and other allergic conditions in developed countries.
• Reduced exposure to infectious agents in childhood prevents normal development of the immune system resulting in a Th2 predominant response

Question 4

Focusing on atopy, patients with asthma also suffer from other IgE-mediated atopic conditions such as?

Answer 4

• atopic dermatitis (eczema)
• allergic rhinitis (hay fever)

Question 5

A number of patients with asthma are sensitive to aspirin.

Answer 5

• Patients who are most sensitive to asthma often suffer from nasal polyps.
• Remember the nose is part of the respiratory tract from a histological point of view.

Question 6

Finally around 10-15% of adult asthma cases are related to allergens in the workplace.

Answer 6

• Occupational asthma is usually diagnosed by observing reduced peak flows during the working week with normal readings when not at work.
• Examples of common occupational allergens include isocyanates and flour.

Question 7

Symptoms and signs?

Answer 7

Symptoms:

• cough: often worse at night
• dyspnoea
• ‘wheeze’, ‘chest tightness’

Signs:

• expiratory wheeze on auscultation
• reduced peak expiratory flow rate (PEFR)

Question 8

Investigation?

Answer 8

• Spirometry is a test which measures the amount (volume) and speed (flow) of air during exhalation and inhalation.
• It is helpful in categorising respiratory disorders as either obstructive (conditions where there is obstruction to airflow,
• for example due to bronchoconstriction in asthma) or restrictive (where there is restriction to the lungs,
• for example lung fibrosis). Key metrics include:

FEV1: forced expiratory volume - volume that has been exhaled at the end of the first second of forced expiration

FVC: forced vital capacity - volume that has been exhaled after a maximal expiration following a full inspiration

Question 9

Typical results in asthma?

Other investigations to consider

chest x-ray: particular in older patients or those with a history of smoking

Answer 9

• FEV1 - significantly reduced
• FVC - normal
• FEV1% - (FEV1/FVC) < 70%

Question 10

• Management of asthma has changed slightly following the 2016 British Thoracic Society guidelines.
• The main take home points are that all patients are started on a inhaled corticosteroid at the time of diagnosis, in addition to a short-acting beta-agonist:

Answer 10