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Basic life support (BLS)

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Basic life support refers to the maintaining of airway patency and supporting breathing and the circulation without the use of equipment other than a protective device (1).

With respect to Basic Life Support in an Adult:

  • The following guidance is based on a situation where the rescuer is alone and without access to medical equipment such as an electrocardiograph or a defibrillator. The guidance is for lay people and medical personnel alike. It is based on the guidance from the European Resuscitation Council (Resuscitation 2005;67:181-341) which has been accepted by the Resuscitation Council (UK).

Basic Life Support (BLS) in an adult consists of the following sequence of actions (1):


Technical description


Make sure you, the victim and any bystanders are safe


  • Check the victim for a response

  • shake his shoulders gently and ask loudly: "Are you all right?"If he responds leave him in the position in which you find him, provided there is no further danger; try to find out what is wrong with him and get help if needed; reassess him regularly


Open the airway

  • the victim should be turned onto his back
  • your hand should be placed on his forehead and gently tilt his head back; with your fingertips under the point of the victim's chin, lift the chin to open the airway


Look, listen and feel for normal breathing for no more than 10 seconds

In the first few minutes after cardiac arrest, a victim may be barely breathing, or taking infrequent, slow and noisy gasps. Do not confuse this with normal breathing. If you have any doubt whether breathing is normal, act as if it is they are not breathing normally and prepare to start CPR

DIAL 999

Call an ambulance (999)

  • ask a helper to call if possible otherwise call them yourself
  • stay with the victim when making the call if possible
  • activate the speaker function on the phone to aid communication with the ambulance service


Send someone to get an AED if available

If you are on your own, do not leave the victim, start CPR


Start chest compressions

  • kneel by the side of the victim
  • place the heel of one hand in the centre of the victim’s chest; (which is the lower half of the victim’s breastbone (sternum))
  • place the heel of your other hand on top of the first hand
  • interlock the fingers of your hands and ensure that pressure is not applied over the victim's ribs
  • keep your arms straight
  • do not apply any pressure over the upper abdomen or the bottom end of the bony sternum (breastbone)
  • position your shoulders vertically above the victim's chest and press down on the sternum to a depth of 5–6 cm
  • after each compression, release all the pressure on the chest without losing contact between your hands and the sternum;
  • repeat at a rate of 100-120 min-1


After 30 compressions open the airway again using head tilt and chin lift and give 2 rescue breaths

  • Pinch the soft part of the nose closed, using the index finger and thumb of your hand on the forehead
  • Allow the mouth to open, but maintain chin lift
  • Take a normal breath and place your lips around his mouth, making sure that you have a good seal
  • Blow steadily into the mouth while watching for the chest to rise, taking about 1 second as in normal breathing; this is an effective rescue breath
  • Maintaining head tilt and chin lift, take your mouth away from the victim and watch for the chest to fall as air comes out
  • Take another normal breath and blow into the victim’s mouth once more to achieve a total of two effective rescue breaths. Do not interrupt compressions by more than 10 seconds to deliver two breaths. Then return your hands without delay to the correct position on the sternum and give a further 30 chest compressions

Continue with chest compressions and rescue breaths in a ratio of 30:2

If you are untrained or unable to do rescue breaths, give chest compression only CPR (i.e. continuous compressions at a rate of at least 100–120 min-1)


Switch on the AED

  • attach the electrode pads on the victim's bare chest
  • if more than one rescuer is present, CPR should be continued while electrode pads are being attached to the chest
  • follow the spoken/visual directions
  • ensure that nobody is touching the victim while the AED is analysing the rhythm

If a shock is indicated, deliver shock

  • ensure that nobody is touching the victim
  • push shock button as directed (fully automatic AEDs will deliver the shock automatically)
  • immediately restart CPR at a ratio of 30:2
  • continue as directed by the voice/visual prompts

If no shock is indicated, continue CPR

  • immediately resume CPR
  • continue as directed by the voice/visual prompts


Do not interrupt resuscitation until:

  • a health professional tells you to stop
  • you become exhausted
  • the victim is definitely waking up, moving, opening eyes and breathing normally

It is rare for CPR alone to restart the heart. Unless you are certain the person has recovered continue CPR


If you are certain the victim is breathing normally but is still unresponsive, place in the recovery position

  • remove the victim’s glasses, if worn
  • kneel beside the victim and make sure that both his legs are straight
  • place the arm nearest to you out at right angles to his body, elbow bent with the hand palm-up
  • bring the far arm across the chest, and hold the back of the hand against the victim’s cheek nearest to you
  • with your other hand, grasp the far leg just above the knee and pull it up, keeping the foot on the ground
  • keeping his hand pressed against his cheek, pull on the far leg to roll the victim towards you on to his side
  • adjust the upper leg so that both the hip and knee are bent at right angles
  • tilt the head back to make sure that the airway remains open
  • if necessary, adjust the hand under the cheek to keep the head tilted and facing downwards to allow liquid material to drain from the mouth
  • check breathing regularly

Be prepared to restart CPR immediately if the victim deteriorates or stops breathing normally


  • suspected spinal injuries: Spinal injuries may occur in a variety of situations, for example, if the victim has sustained a fall, been struck on the head or neck, or has been rescued after diving into shallow water. In a situation where there is a suspected spinal injury then particular care must then be taken during handling and resuscitation to maintain alignment of the head, neck, and chest in the neutral position. When establishing an airway, jaw thrust is preferable to chin lift. During resuscitation, assistance from others may be required to maintain head, back, and chest alignment if adequate splinting is not available. It is important to remember that successful resuscitation that results in paralysis is a tragedy, but failure to carry out adequate ventilation in cases of respiratory arrest will result in death
  • barrier Devices:
  • health care professionals may prefer to use these. A pocket face mask is especially suitable since the technique is easily learned and a good tidal volume can be achieved - care is needed to avoid gastric distension.
  • considerable training is required to use a bag-valve-mask. This device should preferably incorporate an oxygen reservoir facility and generally requires two people
  • there is no evidence of the transmission of the HIV or Hepatitis B virus during mouth-to-mouth ventilation
  • There have been no human studies to address the effectiveness of barrier devices during CPR; however, laboratory studies have shown that certain filters, or barrier devices with one-way valves, prevent transmission of oral bacteria from the victim to the rescuer during mouth-to-mouth ventilation.
  • two rescuer CPR:
  • the ratio of ventilations to compressions remains 2:30 irrespective of the number of rescuer
  • compression-only CPR (1)
  • studies have shown that compression-only CPR may be as effective as combined ventilation and compression in the first few minutes after non-asphyxial arrest.
  • however, chest compression combined with rescue breaths is the method of choice for CPR by trained lay rescuers and professionals and should be the basis for lay-rescuer education
  • lay rescuers who are unable or unwilling to provide rescue breaths, should be encouraged to give chest compressions alone. When advising untrained laypeople by telephone, ambulance dispatchers should give instruction on compression-only CPR
  • mouth to nose ventilation can be effectively preformed on patients if the patients mouth is seriously injured or cannot be opened, if the rescuer is assisting a victim in the water, or if a mouth-to-mouth seal is difficult to achieve (1).
  • regurgitation during CPR (1)
    • turn the victim away from you.
    • keep him on his side and prevent him from toppling on to his front.
    • ensure that his head is turned towards the floor and his mouth is open and at the lowest point, thus allowing vomit to drain away.
    • clear any residual debris from his mouth with your fingers; and immediately turn him on to his back, re-establish an airway, and continue rescue breathing and chest compressions at the recommended rate.


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