Asthma: Diagnosis, Treatment Steps and Acute Severe Asthma

Asthma is a chronic inflammatory disease of the airways that causes variable, reversible airflow obstruction. It affects children and adults, and although most patients can live normal lives with good treatment, asthma attacks can still be fatal. Knowing how to recognise a severe attack is essential for every doctor.

Triggers and risk factors

• Personal or family history of atopy (eczema, allergic rhinitis).
• Allergens: house dust mite, pollen, animal dander, mould.
• Viral respiratory infections.
• Cold air and exercise.
• Smoke and air pollution.
• Occupational exposures.
• Drugs such as beta-blockers and, in some patients, aspirin or NSAIDs.

Clinical features

Episodic wheeze, breathlessness, chest tightness and cough, often worse at night or early morning, and triggered by the factors above. Symptoms vary over time and in intensity. Between attacks the examination may be normal.

Diagnosis

• Spirometry: obstructive pattern (reduced FEV₁/FVC ratio) with significant bronchodilator reversibility (an increase in FEV₁ of at least 12% and 200 mL).
• Peak flow variability over 2 weeks.
• FeNO (fractional exhaled nitric oxide): supports eosinophilic airway inflammation.
• Bronchial challenge tests in uncertain cases.

A normal spirometry result does not exclude asthma if the patient is well at the time of testing.

Long-term management

Treatment is stepped up or down according to control. Inhaled corticosteroids (ICS) are the foundation because they treat airway inflammation. The Global Initiative for Asthma (GINA) no longer recommends short-acting beta-agonist (SABA) treatment alone for adults and adolescents, because it increases the risk of severe attacks. GINA's preferred approach uses ICS–formoterol as the reliever, and also as maintenance at higher steps. Other options include:

• Long-acting beta-agonists combined with ICS (never a LABA alone).
• Long-acting muscarinic antagonists.
• Leukotriene receptor antagonists (for example montelukast).
• Biologic therapies for severe asthma in specialist care.

At every review, check:

• inhaler technique
• adherence
• triggers and smoking
• a written asthma action plan

Acute asthma: assess severity (BTS/SIGN)

• Moderate: peak flow above 50–75% of best or predicted, no features of acute severe asthma.
• Acute severe: any one of
  • peak flow 33–50%
  • respiratory rate 25/min or more
  • heart rate 110/min or more
  • inability to complete sentences in one breath
• Life-threatening: any one of
  • peak flow below 33%
  • SpO₂ below 92%
  • "normal" PaCO₂
  • silent chest
  • cyanosis
  • poor respiratory effort
  • arrhythmia
  • hypotension
  • exhaustion
  • altered consciousness
• Near-fatal: raised PaCO₂ or the need for mechanical ventilation.

Acute management principles

• Oxygen to keep saturation 94–98%.
• High-dose inhaled or nebulised SABA (salbutamol), repeated or continuous.
• Nebulised ipratropium in severe attacks.
• Oral prednisolone or IV hydrocortisone.
• IV magnesium sulfate in severe or life-threatening attacks, after senior advice.
• Early involvement of senior and critical care teams for life-threatening features.

Exam pearls

• A normal or rising CO₂ in an asthma attack is a danger sign: the patient is tiring.
• A silent chest means very little air is moving. It is not a sign of improvement.
• Beta-blockers can trigger severe bronchospasm in asthmatics.

For respiratory revision, see our Exam Night Notes 1.0: Pulmonology and the respiratory part of the Medicine Companion.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. Which spirometry result supports asthma?

   1. Reduced FEV1/FVC with FEV1 rising ≥12% and ≥200 mL after bronchodilator
   2. Normal spirometry always excludes asthma
   3. Reduced DLCO only
   4. FEV1/FVC above 0.8 with no change after bronchodilator
   5. Reduced FVC with normal ratio
   Show answer

   Answer: A. Reduced FEV1/FVC with FEV1 rising ≥12% and ≥200 mL after bronchodilator
   Obstruction with significant bronchodilator reversibility supports asthma. Normal spirometry between attacks does not exclude it.

2. Acute asthma: PEF 40% of best, RR 28/min, HR 115/min, SpO2 95%. Severity?

   1. Mild
   2. Moderate
   3. Acute severe
   4. Life-threatening
   5. Near-fatal
   Show answer

   Answer: C. Acute severe
   PEF 33–50%, RR ≥25, HR ≥110 are features of acute severe asthma; no life-threatening features are present.

3. During an attack, the PaCO2 is 5.5 kPa. What does this mean?

   1. Reassuring
   2. Lab error
   3. A life-threatening feature: the patient is tiring
   4. Hyperventilation
   5. Metabolic alkalosis
   Show answer

   Answer: C. A life-threatening feature: the patient is tiring
   In acute asthma, PaCO2 should be low; a 'normal' PaCO2 is a life-threatening sign of exhaustion.

4. Which drug class can trigger severe bronchospasm in asthma?

   1. PPIs
   2. Calcium channel blockers
   3. Statins
   4. ACE inhibitors
   5. Non-selective beta-blockers
   Show answer

   Answer: E. Non-selective beta-blockers
   Beta-blockers, especially non-selective ones, can precipitate severe bronchospasm.

5. According to GINA, why is SABA-only treatment not recommended for adults?

   1. It must be taken daily
   2. It causes cough
   3. It is too expensive
   4. It increases the risk of severe attacks because airway inflammation is untreated
   5. It is less effective than placebo
   Show answer

   Answer: D. It increases the risk of severe attacks because airway inflammation is untreated
   Inhaled corticosteroids treat the underlying inflammation; SABA alone is linked to more severe exacerbations and deaths.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.