Basic Life Support OSCE — Adult BLS, AED Use, and Recovery Position

Why BLS Is a Non-Negotiable OSCE Station

Basic life support is universally examined. Examiners use a standardised marking scheme aligned to Resuscitation Council UK (RCUK) 2021 guidelines. Marks are lost most commonly for: incorrect compression depth or rate, wrong hand position, checking for breathing incorrectly, and failing to state when to send for the AED. There is no clinical judgement required — this is a procedural skill with precise criteria.

The BLS Sequence — Step by Step

Step 1: Safe Approach

"Before approaching, I would ensure the scene is safe — look for hazards such as electricity, traffic, or caustic substances."

Step 2: Assess Responsiveness

• Shake shoulders firmly and shout: "Are you all right?"
• If no response: "This patient is unresponsive — I need help."

Step 3: Open Airway

• Head-tilt chin-lift: one hand on forehead, two fingers under the bony part of the chin, tilt head back to neutral/sniffing position
• Look in mouth for visible obstruction — remove if accessible

Step 4: Assess Breathing — No More Than 10 Seconds

Look, Listen, Feel — simultaneously:

• Look: chest rise
• Listen: breath sounds
• Feel: air movement on cheek

If breathing normally: place in recovery position, call 999, monitor.

If not breathing normally (or unsure): assume cardiac arrest — proceed to step 5.

Step 5: Call for Help

"I would shout for someone to call 999 and bring an AED. If alone, I would call 999 myself on speakerphone before starting CPR. I would not leave the patient to get the AED until I have performed 1 minute of CPR — unless in a witnessed arrest, where I would get the AED first."

Step 6: 30 Chest Compressions

Step 7: 2 Rescue Breaths

• Maintain head-tilt chin-lift
• Pinch soft part of nose closed
• Seal lips around mouth
• Blow steadily for 1 second — watch chest rise
• Allow chest to fall, then give second breath
• Return to compressions immediately — do not pause over 10 seconds for breaths

Step 8: Continue 30:2 Until

• AED arrives and is ready to use
• Patient shows signs of life (purposeful movement, normal breathing, coughing)
• A healthcare professional takes over
• You are too exhausted to continue

AED Use

1. 1Power on — press button or open lid (automatic on some models)
2. 2Attach pads — right pad below right clavicle; left pad in the left anterior axillary line at V6 position (below armpit)
3. 3Stand clear while AED analyses rhythm — do not touch patient
4. 4Shock advised: "Stand clear — charging — delivering shock" — press button
5. 5Immediately resume CPR for 2 minutes — do not check for pulse
6. 6No shock advised: resume CPR immediately — reanalyse every 2 minutes

Recovery Position

For an unconscious patient who is breathing normally:

1. 1Kneel beside the patient
2. 2Place near arm at right angle to body, elbow bent, palm upwards
3. 3Bring far arm across chest; hold back of hand against near cheek
4. 4With other hand, pull up far knee so foot is flat on floor
5. 5Roll patient towards you — stabilise with knee and hand at cheek
6. 6Tilt head back slightly to keep airway open
7. 7Monitor breathing continuously — call 999 if not already done

Frequently Asked Questions

"What depth should chest compressions be and why does it matter?"

5-6 cm in adults. Compressions shallower than 5 cm are less effective at generating cardiac output. Compressions deeper than 6 cm increase risk of rib fractures, liver laceration, and pneumothorax. In practice, rib fractures are acceptable collateral damage — effective CPR is the priority. "I would not stop CPR because I heard a crack."

"When should you stop CPR?"

When a competent healthcare professional takes over, when the patient has a sustained return of spontaneous circulation with signs of life, when you are physically unable to continue, or when a valid DNACPR (do not attempt CPR) order is confirmed. In an OSCE, do not stop CPR to check for a pulse unless the AED prompts you or you see clear signs of life.

"What is the ratio for paediatric BLS?"

Two rescuers: 15 compressions to 2 breaths (15:2). One lay rescuer: 30:2. Depth: one-third of chest depth. Rate: 100-120/min. Use two fingers for infants, one or two hands for children depending on size. The sequence differs: five initial rescue breaths before starting compressions (because paediatric arrest is usually respiratory in origin).

"What does AED stand for and how does it work?"

Automated External Defibrillator. It analyses the cardiac rhythm, identifies shockable rhythms (ventricular fibrillation and pulseless ventricular tachycardia), and delivers a controlled DC electrical shock to depolarise the myocardium simultaneously and allow a co-ordinated rhythm to emerge. It does not shock non-shockable rhythms (asystole, PEA) — in these cases it will state "no shock advised."

"Should you perform a pulse check before starting CPR?"

Only in a healthcare provider context, and for no more than 10 seconds. Lay rescuers are not taught to check for a pulse because it is unreliable and causes dangerous delays. In an OSCE as a medical student, you may check for a pulse (carotid, up to 10 seconds) — but if absent or uncertain, proceed immediately to CPR.

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