Asthma

Overview

Asthma is characterised by chronic inflammatory reversible airway obstruction and hyperreactivity. It is a heterogeneous disease, meaning there are many different underlying disease processes and different presentations varying in severity and response to treatment.

Epidemiology

• Asthma is one of the most common respiratory conditions
• Around 160,000 people are diagnosed with asthma each year
• Incidence is higher in children than adults

Risk Factors

• Family history
• Family and/or personal history of atopy e.g. eczema/food allergy/hayfever
• Male sex – for pre-pubertal asthma
• Female sex – for the persistence of asthma from childhood to adulthood
• Respiratory infections in infancy
• Prematurity
• Obesity
• Occupational triggers (e.g. isocyanates)

Presentation

Patients generally have:

• Wheeze
• Cough – usually dry
• Shortness of breath
• Chest tightness

The pattern of these symptoms can help make a diagnosis of asthma more likely compared to other conditions such as chronic obstructive pulmonary disease (COPD). Features suggesting asthma are:

• Episodic symptoms – they are usually diurnal (worse at night/early morning)
• Symptoms may be triggered by exercise/chest infections/cold air exposure/allergens e.g. pollen, animal dander
• Symptoms may worsen with aspirin and beta-blockers.
  • Beta-blockers are contraindicated in asthma
• An expiratory polyphonic (multiple pitches and tones) wheeze is heard throughout the chest on auscultation
• There may be a family or personal history of other atopic conditions

Differential Diagnoses

Chronic obstructive pulmonary disease (COPD)

• Asthma and COPD can coexist and be difficult to distinguish
• Patient usually has a history of smoking
• Cough is usually productive
• Shortness of breath can be on exertion
• In some patients, there is no diurnal variation
• FEV₁/FVC ratio is <70% and does not improve with bronchodilators

Bronchiectasis

• Cough usually brings up copious amounts of purulent and offensive sputum
• Frequent chest infections
• History of childhood chest infection
• Coarse lung crackles

Heart failure

• The patient may have a history of ischaemic heart disease or a myocardial infarction
• There may be oedema, pulmonary crackles, or an elevated jugular venous pressure (JVP) on examination

Occupational asthma

• Symptoms present in an adult
• Symptoms usually improve away from work or while on holiday
• Causative agents may be present e.g. isocyanates

Foreign body/obstruction

• The wheeze may be localised, rather than general

Investigations

Patients ≥17 years

• Spirometry with bronchodilator reversibility (BDR) testing + fractional exhaled nitric oxide (FeNO):
  • Spirometry usually shows:
    • Reduced FEV1
    • Normal FVC
    • FEV1/FVC ratio: <0.7
  • Reversibility testing involves giving a bronchodilator and observing changes in spirometry findings:
    • Adults: improvement in FEV1 of ≥12% and a volume of ≥200 ml is positive
    • Children: improvement in FEV1 of ≥12% is positive
  • Nitric oxide (NO) is released by eosinophils during inflammatory reactions. In asthma, FeNO levels are raised:
    • Adults: ≥40 ppb is raised
    • Children: ≥35 ppb is raised

Patients 5-16 years

• Spirometry with BDR testing
• Offer FeNO if spirometry is normal or spirometry shows an obstructive picture with a negative BDR test

A reason for this is that it can be difficult to measure FeNO tests in children as it requires slow and controlled breathing.

Patients <5 years

• Diagnosis is made clinically

Management

Patients ≥17 years

A stepwise approach is recommended by NICE:

• 1^st-line: short-acting beta agonist (SABA)
  • Example SABAs are salbutamol and terbutaline 
• 2^nd-line: SABA + low-dose inhaled corticosteroid (ICS)
  • Examples ICSs are beclometasone, budesonide, ciclesonide, fluticasone, and mometasone
• 3^rd-line: SABA + low-dose ICS + leukotriene receptor antagonist (LTRA)
  • Examples are montelukast and zafirlukast
• 4^th-line: SABA + low-dose ICS + long-acting beta-agonist (LABA) +/- LTRA (depending on response)
  • Example LABAs are salmeterol and formoterol
• 5^th-line: SABA + maintenance and reliever therapy (MART) that includes a low-dose ICS +/- LTRA
  • MART is a single inhaler containing ICS and LABA which can be used for relief of symptoms and maintenance therapy
• 6^th-line: SABA + medium-dose MART +/- LTRA or SABA + moderate-dose ICS + LABA
• 7^th-line: SABA +/- LTRA and one of:
  • Fixed high-dose ICS (i.e. not as a MART)
  • Trial adding long-acting muscarinic receptor antagonist (LAMA) or theophylline
  • Refer to specialist

Patients 5-16 years

Management is very similar to adults:

• 1^st-line: SABA
• 2^nd-line: SABA + paediatric low-dose ICS
• 3^rd-line: SABA + paediatric low-dose ICS + LTRA
• 4^th-line: SABA + paediatric low-dose ICS + LABA (stop LTRA if it has not helped)
• 5^th-line: SABA + MART that includes paediatric low-dose ICS
• 6^th-line: SABA + paediatric moderate-dose ICS MART or SABA + moderate-dose ICS + LABA
• 7^th-line: SABA and one of:
  • High-dose paediatric ICS as fixed-dose or part of a MART
  • Trial adding theophylline
  • Refer to specialist

Patients <5 years

A stepwise approach is recommended by NICE:

• 1^st-line: SABA
• 2^nd-line: SABA + 8-week trial of paediatric moderate low-dose ICS
  • If symptoms do not resolve, an alternate diagnosis should be considered
  • If symptoms do resolve but restart <4 weeks after stopping ICS, restart with paediatric low-dose ICS
  • If symptoms do resolve but restart >4 weeks after stopping ICS, repeat the 8-week trial with a paediatric moderate dose ICS
• 3^rd-line: SABA + paediatric low-dose ICS + LTRA
• 4^th-line: SABA + paediatric low-dose ICS + refer to specialist

All patients

• 1^st-line: annual influenza jab + personal asthma action plan

Stepping down treatment

Consider stepping down asthma treatment every 3 months if the patient is stable and treatment is sufficient. This involves reducing the dose of ICS by 25-50% at a time.

Aspirin and Asthma

Overview

Aspirin and NSAIDs can lead to bronchoconstriction in patients with asthma, particularly women, those with adult-onset asthma, and those with severe disease.

Around 60% of people with asthma who are aspirin-sensitive have nasal polyps. The triad of asthma, aspirin sensitivity and nasal polyps is known as Samter’s triad. Therefore, caution should be taken when prescribing aspirin and other NSAIDs. 

Monitoring

• Patients are followed up at least annually, and more often if their symptoms are more severe or they have had an acute asthma attack within the last year
• Any patient >5 years should have their control reviewed through peak flow measurements or spirometry
• The patient’s inhaler technique should be reviewed regularly
• Children can score symptoms using the Childhood Asthma Control Test or Asthma Control Questionnaire (ACQ)
• Adults can score symptoms using the Asthma Control Test, ACQ, or the Royal College of Physicians 3 Questions

Inhaler Technique

Overview

Instructions for using a pressurised metered-dose inhaler (pMDI) are:

• Remove the cap from the mouthpiece and shake the inhaler
• Stand/sit upright and lift the chin to open the airway
• Breathe out gently
• Put the mouthpiece in the mouth and seal with your lips
• Start breathing slowly in and out. As you breathe in, press the inhaler canister and continue to breathe in slowly
• Hold your breath for 10 seconds if possible before breathing out slowly
• If another dose is needed, wait 30 seconds and repeat

Patient Advice

• Patients should be encouraged to self-monitor using peak expiratory flow rate (PEFR) measurements
• Patients should minimise exposure to or avoid triggers where possible e.g. cigarette smoke, irritants, pollen, animal dander etc.
• Patients should avoid NSAIDs and beta-blockers where necessary
  • These can precipitate asthma attacks

Complications

• Acute asthma exacerbation
• Airway remodelling and irreversible airway changes
• Impaired quality of life
• Death

Prognosis

• Male children are more likely to grow out of asthma through adolescence
• The earlier the onset of asthma, the better, as many children become asymptomatic by around 6-11 years of age
  • In children with atopy, early-onset asthma may carry a worse prognosis