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Asthma: a very basic introduction?

  • 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. 


What is asthma?

  • 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.


Risk factors and aetiology?

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


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

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


A number of patients with asthma are sensitive to aspirin.

  • 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.


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

  • 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.


Symptoms and signs?


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


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



  • 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


Typical results in asthma?


Other investigations to consider

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

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


  • 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: