BLS – Basic Life Support
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This really is ‘basic’ life support, often performed without any equipment (or an automated defibrillator if one is available). It involves pure ‘CPR’ as a lay person might understand it.
It is a technique used to try and keep a patient alive until proper equipment can be brought to try and reverse the underlying cardiac arrest.
Rarely, CPR can be enough to reverse an underlying cardiac arrest, most commonly when it is secondary to a respiratory arrest (e.g. drowning).
BLS is an international protocol designed to be taught to all hospital staff members and to members of the general public. The most recent guidelines were published in 2015 (1). BLS courses are run by medical institutions (usually hospitals) – often as a 1-2 hour course. Most medical institutions require all staff (including non-clinical staff) to regularly – usually annually – attend the course.
If the oxygen supply to the brain is lost for more than 3-4 minutes then permanent cerebral damage will result. Therefore, prompt initiation and continuation of BLS are paramount for a good outcome.
BLS Chain of Survival. From (1)

The Basic Principle

The basic principle is very simple and can be summarised with the flowchart below. From (1)


You see a collapsed patient…

  • Check for danger! Make sure the situation is safe before approaching
  • Check for a response – shake the victim’s shoulders and ask loudly if they are ok. If they respond, then you should leave them where they are, provided they are not in danger. Try and find out what is wrong then go and get help. Return to the patient as soon as you can and keep re-assessing them.
  • If they do not respond, then:
    • Shout for Help! If no help is available, go and get help (e.g. call emergency services, or go to find somebody else to do this for you).
    • Open the patient’s airway, by doing the head tilt and chin lift.
  • Listen for normal breathing and look to see if you can see the patient’s chest rising and falling. Can you feel breath on your cheek? Do this for no more than 10 seconds. Don’t confuse gasping irregular breaths (“agonal breathing” – which are often associated with cardiac arrest) with normal breathing. If you have any doubts about normal breathing, then assume the patient is not breathing normally.
  • If they are breathing normally, put them into the: Recovery position – Imagine the patient lying flat on their back. Lift up their left knee and put the outside of their left hand against their right cheek. Roll the patient onto their right hand side, making sure their hand is in contact with their cheek at all times. Their right arm should be stretched out at 90’ to their torso. Do not keep the person laid on one side for more than 30 minutes due to the pressure on their arm. Swap them over to the other side before then.
Recovery Position
Recovery Position
  • When you return, you should start chest compressions. You should kneel on the patient’s right hand side. Put your hand in the middle of the patient’s chest, about 2 fingers above the level of the bottom of the sternum. Interlock your fingers. Don’t apply pressure on the stomach or on the very bottom of the sternum! Position yourself so you are vertically over the patient’s chest and keep you arms straight. Press down about 5-6cm (1/3 of the depth of the chest). You should aim to do 100 compressions a minute, or about 2 per second. Some recommend imagining the pace of a song in your head… and performing chest compressions to the ‘beat’. Apparently two appropriately speedy songs are:
    • Staying Alive – The BeeGees
    • Nelly the Elephant – The Nursery Rhyme
  • Often, suitably hard chest compressions will cause rib fractures. You might hear the ribs cracking – don’t worry!
  • After 30 compressions, open the airway again, doing the head tilt and chin lift. Pinch the nose closed, and whilst still maintaining the chin lift and keeping the mouth open, take a normal breath and give two breaths to the patient. Breathe out for about 1 second. You should see the patient’s chest rise. If not, the its likely the air is going into the stomach, and you are not correctly holding the patient’s head in the ‘head tilt, chin lift’ position. Allow the air to come out of the patient and then do the same again. You should maintain the chin lift at all times. After this start 30 compressions again. Don’t ever attempt more than 2 breaths. If the chest doesn’t rise, then check for obstructions. If there is more than one person present, you should swap over about every 2 minutes to prevent fatigue. You should continue resuscitation until help arrives, or until the victim recovers, or until you can no longer continue because you are exhausted.
    • Often in a hospital setting breaths will be provided by BVM – Bag, valve and mask ventilation. 
  • If an automated defibrillator is available, then attach the pads to the patient’s chest. If you have help, ask someone to do this for you whilst you continue CPR.
    • Follow the audible instructions
    • Make sure nobody is touching the patient when a shock is delivered (if one is delivered)
    • Immediately resume CPR and continue to follow the audible instructions
  • Continue CPR until:
    • The patient recovers (rare) – if you are unsure whether or not they have recovered, then continue CPR
    • You are exhausted
    • Further help arrives (e.g. ambulance, or, in hospital, the crash team)


The guidelines for children are different.
  • Give 5 rescue breaths first
  • Give chest compressions and breaths in the ratio 15:2
Children are more likely to have suffered a primary respiratory arrest than adults. As a result, you should give 5 rescue breaths before starting chest compressions, and you should attempt CPR for 1 minute before going for help.
These same exceptions may be applied if the victim is suspected of drowning.


Adult basic life support and automated external defibrillation. Resuscitation Council (UK). 2015

Accessed online on 13th Feb 2018. Available here

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

This Post Has 2 Comments

  1. luca

    this is shit

    1. tom

      Thanks Luca for your helpful and constructive comments.
      We welcome all feedback.
      Did you know that almostadoctor is a wiki?
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