Basic Life Support (BLS) – OSCE guide

This basic life support (BLS) guide aims to provide an overview of performing cardiopulmonary resuscitation (CPR) in a hospital setting, which is a common OSCE scenario.

This guide is based on the Resuscitation Council (UK) guidance and is intended only for students preparing for their OSCE exams and not for patient care.

Check out our basic life support (BLS) OSCE mark scheme here.


Chain of survival

The chain of survival refers to a series of actions that, properly executed, reduce the mortality associated with cardiac arrest. Like any chain, the chain of survival is only as strong as its weakest link.

The four interdependent links in the chain of survival are:

  • Early recognition and call for help
  • Early CPR
  • Early defibrillation
  • Early advanced cardiac life support


1. Ensure personal safety

  • Check the patient’s surroundings are safe before approaching (if you injure yourself, you will not be able to help the patient, so take this seriously)
  • Put on gloves (and other personal protective equipment) as soon as possible
  • Be careful with sharps during resuscitation


2. Check the patient for a response

  • The first step is to assess for a response.
  • Gently shake the patient’s shoulders and ask loudly “Hello can you hear me?” or “Are you alright?”.
  • If they respond, the patient then needs an urgent medical review with a full ABCDE assessment (see our emergency assessment guides here).


3. No response from the patient

Get help

  • Shout for help: This is absolutely essential, as you will not be able to effectively assess and treat the patient alone.

Position the patient and inspect the airway

  • Position the patient on their back
  • Open their airway using a head-tilt and chin-lift manoeuvre
  • Inspect the airway for obvious obstruction. If an object is seen to be obstructing the airway, use a finger sweep or suction to remove obstructions that are in line of sight.

Assess for signs of life

  • With the airway held open (using the head-tilt and chin-lift manoeuvre), position your head looking down towards the chest, with your cheek above the patient’s mouth.
  • If the patient is suspected to have suffered significant trauma (with potential spinal involvement) perform a jaw-thrust rather than a head-tilt chin-lift manoeuvre.
  • In addition, you should place two fingers over the carotid artery to assess for a pulse at the same time.


  • Look, listen and feel to assess if the patient is breathing for 10 seconds (ideally, you should expose the chest to assess breathing):
    • Observe for chest rising and falling
    • Listen for any evidence of breath sounds
    • Feel for air blowing against your cheek
    • Look for any other signs of life (e.g. movement)

Agonal breathing

  • If the patient has occasional, irregular gasps of breath, this does not qualify as a sign of life as it commonly occurs in cardiac arrest and is referred to as agonal breathing.


A pulse is present, but the respiratory rate is low

  • If the respiration rate is below 12 – assist ventilation with bag valve mask (BVM) to maintain 10 breaths/min (re-checking the pulse every minute to ensure it is still present).
  • You will likely need two people to perform effective ventilation with a BVM (one ensuring a good seal over the face and the other compressing the bag to deliver the oxygen).
  • The BVM should ideally be connected to high-flow oxygen as soon as possible.

A pulse is present and respiratory rate is acceptable

  • If you feel a pulse or evidence of genuine breathing, the patient would need urgent medical assessment (using an ABCDE approach) to stabilise them before further deterioration.


4. No signs of life

Call the resuscitation team (a.k.a. “crash team”)

  • If there are no signs of life, you need to call for help from the resuscitation team and commence CPR.
  • If more than one person is present, you can do these tasks simultaneously, however, if you are alone, you should leave the patient and get help first (as this will ensure the resuscitation team attend and can commence advanced life support).
  • In a hospital, calling for help involves calling 2222 to request urgent input from the resuscitation team
  • When calling 2222 it is important to clearly state your location (e.g. ward) and the type of cardiac arrest (e.g. adult or paediatric) as this will inform which team members attend.


Perform chest compressions

  • The patient needs to be positioned on a flat, hard surface for effective compressions to be possible.
  • Deliver 30 chest compressions followed by 2 ventilations and repeat.
  • Place one hand on top of the other in the centre of the lower half of the sternum.
  • Aim to compress the chest by approximately one-third of the depth of the chest wall (5-6cm), as this allows for sufficient emptying of the cardiac ventricles.
  • Perform compressions at approximately 100-120 compressions per minute.
  • Make sure to allow the chest to fully recoil (this allows enough time for the heart’s chambers to refill before the next compression).
  • It is absolutely essential to minimise interruptions to chest compressions.
  • Alternate the person performing chest compressions at 2-minute intervals (if enough team members are present)
  • If tracheal intubation is performed, chest compressions should then be continued without any interruption at a rate of 100-120 a minute.


Example of chest compressions
Example of chest compressions 3



Ventilate the patient

  • Perform a head-tilt chin-lift manoeuvre to open the airway and allow effective ventilation.
  • Pinch the nostrils closed with your thumb and index finger.
  • Place your mouth tightly over the patient’s mouth (or use a pocket-mask or bag-valve-mask if available)
  • Deliver 2 breaths (with an inspiratory time of approximately 1 second) and watch for the patient’s chest rising (which confirms you are ventilating them).
  • Release the nostrils and observe for the patient’s chest falling as the air is exhaled.
  • You should then begin performing another 30 chest compressions.
  • Add supplemental oxygen as soon as you are able to.


Mouth-to-mouth ventilation

  • In clinical settings, mouth-to-mouth ventilation is not often used because of clinical reasons (e.g. concerns regarding infections) or because airway equipment is available (e.g. pocket-mask, bag-mask or anaesthetic input for tracheal intubation).
  • If there are clinical reasons to avoid mouth-to-mouth ventilation, perform chest compressions until help and airway equipment arrives.



Attach the AED

  • Once an automated external defibrillator (AED) arrives, it is import to attach the 2 self-adhesive pads immediately to the patient’s chest (as labelled):
    • ADHESIVE PAD 1: To the right of the sternum below the clavicle
    • ADHESIVE PAD 2: In the mid-axillary line with its long axis vertical and sufficiently lateral
    • If the patient is hairy, you may need to shave the areas to allow adequate contact between the pads and the skin
    • Check for piercings and remove as these can cause burns to the patient during defibrillation (however doing this should not significantly delay defibrillation)


Turn on the AED

  • Turn on the AED and follow the audio-visual instructions:
    • Typically the AED will ask you to pause chest compressions whilst it performs a rhythm check.
    • It will then indicate if the rhythm is shockable or non-shockable and instruct you to deliver a shock if it is the former.
    • If a shock needs to be delivered, ensure you and no one else is in contact with the patient and press the deliver shock button on the AED
    • Re-commence CPR after the shock is delivered and follow further instructions from the AED (which will typically involve another rhythm check in 2 minutes).
  • Advanced life support would be commenced once the resuscitation team arrives.

If signs of life present or the patient responds to treatment

Arrange an urgent medical assessment

  • Call for urgent medical assessment which may be the same resuscitation team as for cardiac arrest, or a dedicated medical emergency team.

Assess ABCDE

Re-assess the patient using a structured ABCDE approach:

  • Airway: Ensure airway patent
  • Breathing: Give oxygen and monitor with pulse oximetry
  • Circulation: Record blood pressure, obtain venous access, attach ECG monitoring
  • Disability: Assess AVPU/GCS and check a capillary blood glucose
  • Exposure: Inspect for evidence of trauma or other clues as to a diagnosis (e.g. rash or bleeding)

See our ABCDE guides here



Prepare to handover to the attending medical teams using an SBAR structure (see our guide here)


1. Resuscitation Council (UK). Resuscitation Guidelines 2015. Authors: Carl Gwinnutt, Robin Davies, Jasmeet Soar. Accessed August 15th 2018. Available from: [LINK].

2. By BruceBlaus [CC BY-SA 4.0 (], from Wikimedia Commons

3. By Video by Bangkok Hospital PhuketSegment extracted and converted by Mikael Häggström [CC BY 3.0 (], via Wikimedia Commons



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