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PLAB 2 Acute Asthma Station: Severity Classification, Management Steps & Free Practice

Acute asthma is one of the most common respiratory presentations tested in PLAB 2. The eight minutes ask whether you can rapidly assess severity, start the right treatment in the right order, and recognise the life-threatening features that need immediate senior input. You will face a breathless patient, take a focused history, request examination findings and a peak flow from the station panel, classify severity, and outline a stepwise management plan in plain English. This guide walks through the BTS/SIGN and NICE-aligned approach the station rewards, the order of treatment steps that scores well, and the safety-critical items that decide pass from fail.

Last reviewed 2026-05-15 · Reading time about 8 minutes

What the station is testing

The station is marked across data gathering, clinical management and interpersonal skills, plus two safety-critical actions: starting oxygen when saturations are below 94 to 98%, and not discharging a patient with moderate-or-worse severity. Missing either collapses the Clinical Management domain to Clear Fail. Severity classification - moderate, severe or life-threatening - is the single highest-yield non-history block in the station.

Hold these differentials in your head

Bracket the deadly causes first. If you fail to consider any of these in your reasoning out loud, the clinical-management domain will suffer.

  • Acute asthma exacerbation
    Wheeze, breathlessness and chest tightness on a background of known asthma. Severity is classified by peak flow, oxygen saturation, speech, accessory muscle use, pulse and respiratory rate.
  • Acute COPD exacerbation
    Older smoker with chronic productive cough and progressive breathlessness. Less prominent wheeze, more sputum, may have hypercapnia. Oxygen target is 88-92%, not 94-98%.
  • Anaphylaxis
    Sudden wheeze with urticaria, angioedema, hypotension or recent exposure to an allergen. Adrenaline IM 0.5 mg first, then bronchodilators - do not delay.
  • Community-acquired pneumonia
    Productive cough, fever, focal crackles or consolidation, raised CRP and WCC. Wheeze less prominent. Antibiotics per local protocol.
  • Pulmonary embolism
    Sudden breathlessness with pleuritic chest pain, tachycardia, sometimes haemoptysis. Look for thrombotic risk factors - immobility, recent surgery, malignancy, oestrogen.
  • Spontaneous pneumothorax
    Sudden unilateral pleuritic pain with breathlessness, typically a tall thin young patient or a known COPD/asthma sufferer. Decreased breath sounds and hyperresonance on the affected side.
  • Acute heart failure
    Older patient, basal crackles, pink frothy sputum, orthopnoea, raised JVP. Wheeze can mimic asthma ("cardiac asthma") - look for cardiac history.

Step-by-step approach

This is the structure that scores. You do not need to follow it verbatim, but every numbered block below maps to a cluster of marks in the rubric.

  1. 1. Open the consultation - paced and empathic

    Match the patient's pace. A breathless patient cannot answer long-winded questions.

    • Wash hands, greet, introduce yourself.
    • Confirm name and date of birth quickly.
    • Acknowledge the breathlessness: "I can see you're working hard to breathe - I'll keep my questions short."
    • Tell them what you are going to do and start oxygen as soon as findings allow.

  2. 2. Take a focused, short-question history

    Use yes/no and short-answer questions where possible. Give them time between questions.

    • When did the breathing get worse?
    • Was there a trigger - a cold, an allergen, the cold air, exercise?
    • How many puffs of the blue reliever have you used today?
    • Have you been taking the brown preventer regularly?
    • Can you finish sentences? Are you wheezing?
    • Any chest pain, fever, coloured sputum?

  3. 3. Critical asthma history - never skip these

    Previous severity is a major predictor. These items are graded heavily.

    • Previous hospital admissions for asthma.
    • Previous ITU admission or intubation - explicitly ask.
    • Triggers and known allergies.
    • Smoking, vaping, occupational exposure.
    • Pets and home environment.
    • Best peak flow at home when well.

  4. 4. Request examination and bedside findings

    Address the station for vitals, respiratory examination, peak flow and ABG.

    • Vital signs - respiratory rate, oxygen saturation, heart rate, blood pressure, temperature.
    • Respiratory exam - air entry, wheeze, accessory muscles, tripod posture, silent chest if life-threatening.
    • Peak expiratory flow rate - measure on arrival and compare to best or predicted.
    • Arterial blood gas - especially if saturations under 92% or severe features.
    • Chest X-ray to rule out pneumothorax and consolidation.

  5. 5. Classify severity out loud

    This is the highest-yield single item in the clinical management block.

    • Moderate: peak flow 50-75% best/predicted, no features of severe asthma.
    • Severe: peak flow 33-50%, RR >25, HR >110, inability to complete sentences in one breath.
    • Life-threatening: peak flow <33%, SpO2 <92%, silent chest, cyanosis, exhaustion, altered consciousness, normal or raised PaCO2.
    • Verbalise: "This is a severe acute asthma exacerbation" - the examiner is listening for the words.

  6. 6. Start oxygen if hypoxic

    Target saturations 94-98% in acute asthma. Oxygen is a safety-critical action.

    • Apply oxygen via face mask or nasal cannula immediately if SpO2 below 94%.
    • Titrate to the 94-98% target - do not start at 15 L if 4 L gets her there.
    • Keep a saturations monitor on continuously.

  7. 7. Pharmacological management - in order

    The order matters and the examiner is listening for each step.

    • Nebulised salbutamol 5 mg, repeat back-to-back if severe.
    • Add nebulised ipratropium bromide 500 mcg if severe or not responding.
    • Oral prednisolone 40-50 mg or IV hydrocortisone 100 mg.
    • IV magnesium sulphate 2 g over 20 minutes for life-threatening or non-responding patients.
    • IV salbutamol or aminophylline only on senior advice.
    • Antibiotics only if there is evidence of bacterial infection.

  8. 8. Escalate if life-threatening

    Call seniors and ITU early - do not wait for arrest.

    • Inform medical registrar / on-call team immediately.
    • Anaesthetics / ITU review for any life-threatening features or no response to initial treatment.
    • Repeat ABG to watch for rising PaCO2 - a sign of exhaustion.
    • Prepare for possible non-invasive ventilation or intubation.

  9. 9. Address compliance without blame

    Many patients have stopped their preventer. Counselling here is graded interpersonal-skills marks - do it without shaming.

    • Explain why the brown preventer matters even when she feels well.
    • Ask what would make it easier to take consistently.
    • Arrange a repeat prescription and inhaler-technique review.
    • Offer an asthma action plan and a peak-flow diary.

  10. 10. Admit, safety-net and close

    No moderate-or-worse asthma is discharged home from A&amp;E.

    • Admit for monitoring and treatment review.
    • Explain the plan in plain English - chunk and check.
    • Safety-net: come back immediately if breathing worsens, can't talk, lips go blue or the inhaler stops helping.
    • Invite questions, thank her, close.

Common pitfalls

  • Not classifying severity out loud - the examiner is listening for the words "moderate", "severe" or "life-threatening".
  • Forgetting to ask about previous ITU admission or intubation - the single strongest predictor of mortality.
  • Skipping the brown preventer-compliance question - it is a top-weighted history item.
  • Starting full-flow 15 L oxygen reflexively - the target is 94-98%, titrate it.
  • Forgetting steroids - they reduce relapse and admission length, every guideline lists them.
  • Talking faster than the breathless patient can listen.
  • Blaming the patient for missing her preventer - it costs interpersonal marks even if the medicine is right.
  • Discharging home with a salbutamol-puffs script - this is a safety-critical fail at moderate or worse severity.

Frequently asked questions

What is the oxygen target in acute asthma?

Target oxygen saturations of 94-98% in acute asthma, per BTS/SIGN and NICE guidance. This is different from COPD (where the target is 88-92% to avoid CO2 retention). Start oxygen if saturations are below 94% and titrate to the target.

When do I give IV magnesium in acute asthma?

Give IV magnesium sulphate 1.2-2 g over 20 minutes for life-threatening asthma or for severe asthma that has not responded to the first round of nebulised bronchodilators and steroids. Discuss with seniors before giving in the PLAB 2 station - mentioning it on the management list is enough for the mark.

How do I classify asthma severity quickly?

Moderate: peak flow 50-75% of best or predicted, no features of severe asthma. Severe: peak flow 33-50%, RR over 25, HR over 110, inability to complete sentences. Life-threatening: peak flow under 33%, SpO2 under 92%, silent chest, cyanosis, exhaustion or normal/raised PaCO2.

What is the role of antibiotics in acute asthma?

Antibiotics are not routine in acute asthma. Give them only if there is clear evidence of bacterial infection - fever, purulent sputum, focal consolidation on chest X-ray. Most asthma exacerbations are triggered by viral upper respiratory tract infections that do not need antibiotics.

Can I discharge a patient with moderate asthma from A&E?

No. PLAB 2 stations and BTS/SIGN guidance both expect admission for monitoring at moderate or worse severity, especially in a patient who is poorly compliant with preventer therapy. Discharging is marked as a safety-critical fail in the station.

Can I practise the PLAB 2 acute asthma station for free?

Yes. Plabity gives every new user one free station credit on signup. The acute asthma station is available immediately - you speak with a simulated patient in real time, request peak flow and ABG findings, and receive a PLAB-rubric-aligned mark scheme with personalised feedback at the end.

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