Practice ABC of Resuscitation, 6th Edition

Basic Life Support

BMJ 2014; 348 doi: (Published 02 April 2014) Cite this as: BMJ 2014;348:bmj.g1730
  1. Anthony J. Handley
  1. Colchester Hospital University NHS Foundation Trust Colchester Essex UK

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  • Early institution of CPR and defibrillation significantly increase the chance of survival after cardiac arrest

  • Effective chest compression is vital, with correct depth and rate, and with a minimum of interruptions

  • For the non-specialist, CPR on a child should follow the adult sequence of actions


The term basic life support (BLS) is used to describe maintenance of a clear airway and support of breathing and the circulation in cases of cardiac arrest, without the use of equipment other than a simple airway device or protective shield. Cardiopulmonary resuscitation (CPR) is the combination of chest compression and rescue breathing, and forms the basis of modern BLS.

The chances of survival after cardiac arrest are increased when the event is witnessed and when a bystander institutes CPR prior to the arrival of the emergency services. When the heart arrests in ventricular fibrillation, the critical interval that determines outcome is the time from arrest until defibrillation, the chances of survival decreasing by between 7 and 10% for each minute of delay. Effective CPR reduces this decline by about 50%.

The best chance of a successful outcome for the patient is achieved if chest compressions are started as soon as cardiac arrest is diagnosed. Chest compressions should be given with minimal interruptions at the recommended rate and depth, and are accompanied by artificial ventilation according to the current guidelines (see Box 1 and Figure 1).

Figure 1
Figure 1

Adult basic life support. Reproduced with the kind permission of the Resuscitation Council (UK).

box 1

Optimal chest compression characteristics (adults)

  • Depth 5–6 cm

  • Rate 100–120 min−1

  • Release pressure fully between each compression

  • Minimise interruptions in CPR


Diagnosing cardiac arrest

Although an absent carotid pulse in an unconscious patient is a sure sign of cardiac arrest, it has been shown that the accuracy of such a pulse check can be very poor, not only for laypeople. Unless the rescuer is trained, experienced, and confident in feeling for the carotid pulse, a diagnosis of cardiac arrest should be assumed if the patient is unresponsive and not breathing normally.

Agonal breathing

Particular care should be taken to recognise agonal breathing (irregular, often noisy, gasps) as a sign of cardiac arrest and not a sign of life. If agonal breathing is present, start CPR.

Circulatory support

A patient in cardiac arrest is unlikely to recover as a result of CPR alone, but rapid institution of resuscitation, particularly chest compression, can ‘buy time’ until a defibrillator and the emergency services arrive.

The correct place to compress the chest is in the centre of the lower half of the sternum. It is recommended that this location be taught in a simplified way, such as, ‘place the heel of your hand in the centre of the chest with the other hand on top’. This instruction should be accompanied by a demonstration of placing the hands on the lower half of the sternum on a manikin. Use of the inter-nipple line as a landmark is not reliable.

Firm pressure is needed to compress the chest of an adult by 5–6 cm. The rescuer's arms should be kept straight with the elbows locked. About the same amount of time should be spent in the compressed phase as in the released phase, with complete release of pressure each time. The rate should be between 100–120 min−1 and compressions should be given in groups of 30, interspersed with 2 rescue breaths.

Ventilatory support

Establishing and maintaining an airway is the single most useful manoeuvre that the rescuer can perform. To open the airway, the patient's head should be tilted backwards (without hyperextension of the neck) and the jaw lifted to pull the tongue forward off the posterior pharyngeal wall.

To give mouth-to-mouth ventilation the patient's nose should be pinched closed. The rescuer should then take a breath, make a firm seal with his or her lips around the patient's mouth, and breathe out, watching as the patient's chest clearly rises as in normal breathing. This should take about a second, and it is important to avoid over-inflation as this will allow air to enter the oesophagus and stomach. Subsequent gastric distension causes not only vomiting but also passive regurgitation into the lungs, which often goes undetected. The expired air is then allowed out passively. As soon as the chest falls, another breath should be given, with 30 chest compressions being given after every 2 rescue breaths.

Risks to rescuer and patient

The main concern during resuscitation is for the patient, but it is equally important to ensure that no harm comes to the rescuer.

Before approaching a collapsed patient, the rescuer should rapidly assess any personal danger as well as any to the patient from hazards such as falling masonry, gas, electricity, fire, or traffic.

Although there may be fears about catching HIV (human immunodeficiency virus), no case has been recorded due to mouth-to mouth-resuscitation. Despite the presence of the virus in saliva, it does not seem that transmission occurs via this route in the absence of blood-to-blood contact. There have been reports of the transmission of other infections, such as tuberculosis (TB) and severe acute respiratory distress syndrome (SARS), but these have been very rare. Nevertheless, those who may be called upon to administer resuscitation should be allowed to use some form of barrier device, preferably a ventilation mask (for mouth-to-mask ventilation) or a filter device placed over the mouth and nose.

Adult basic life support sequence

  • Make sure the patient, any bystanders, and you are safe.

  • Check the patient for a response:

    • Gently shake his shoulders and ask loudly, ‘Are you all right?’ (Figure 2)

  • 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

  • If he does not respond:

    • Shout for help

  • Turn him onto his back and open the airway using head tilt and chin lift:

    • Place your hand on his forehead and gently tilt his head back

    • With your fingertips under the point of the patient's chin, lift the chin to open the airway (Figure 3)

  • Keeping the airway open, look, listen, and feel for normal breathing:

    • Look for chest movement

    • Listen at the patient's mouth for breath sounds

    • Feel for air on your cheek (Figure 4)

  • Look, listen, and feel for no more than 10 seconds to determine if the patient is breathing normally. If you have any doubt whether breathing is normal, act as if it is not normal

  • If the patient is breathing normally:

    • Turn him into the recovery (lateral) position (Figure 5)

  • If he is NOT breathing normally:

    • Ask someone to call for an ambulance (or the emergency team if in hospital) and bring an AED if available. If you are on your own, use your mobile phone to call for an ambulance. Leave the patient only when no other option exists for getting help

  • Start chest compression as follows:

    • Kneel by the side of the patient

    • Place the heel of one hand in the centre of the patient's chest (which is the lower half of the patient's 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 patient's ribs. Do not apply any pressure over the upper abdomen or the bottom end of the sternum (Figure 6)

    • Position yourself vertically above the patient's chest and, with your arms straight, press down on the sternum 5–6 cm (Figure 7)

  • After each compression, release all the pressure on the chest without losing contact between your hands and the sternum

  • Repeat compressions at a rate of 100–120 min−1

  • Compression and release should take an equal amount of time

  • Combine chest compression with rescue breaths:

    • After 30 compressions open the airway, again using head tilt and chin lift

    • Pinch the soft part of the patient's nose closed, using the index finger and thumb of your hand on his forehead

    • Allow his 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 (Figure 8)

    • Blow steadily into his mouth whilst watching for his chest to rise—take about one second to make his chest rise as in normal breathing: this is an effective rescue breath

    • Maintaining head tilt and chin lift, take your mouth away from the patient and watch for his chest to fall as air comes out

    • Take another normal breath and blow into the patient's mouth once more to give a total of two effective rescue breaths. The two breaths should not take more than 5 s. 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

  • Stop to recheck the patient only if he starts to show signs of regaining consciousness, such as coughing, opening his eyes, speaking, or moving purposefully AND starts to breathe normally; otherwise do not interrupt resuscitation

Figure 2
Figure 2

Establish responsiveness.

Figure 3
Figure 3

Head tilt – chin lift.

Figure 4
Figure 4

Look, listen, and feel for breathing.

Figure 5
Figure 5

Recovery (lateral) position.

Figure 6
Figure 6

Hand position for chest compression.

Figure 7
Figure 7

Compress the chest 5–6 cm at a rate of 100–120/min.

Figure 8
Figure 8

After 30 compressions give 2 rescue breaths.

Compression-only CPR

There is considerable published evidence that supports the concept of chest compression-only CPR for out-of-hospital cardiac arrest patients: it is simple and does not require rescuers to perform unpleasant mouth-to-mouth ventilation. The problem is that it is effective for a limited period only (probably less than 5 min) and, for a small but important minority of patients (children and those suffering an asphyxial or prolonged arrest), it is suboptimal treatment. It is not recommended as the standard management of out-of-hospital cardiac arrest, but should be considered (a) if the rescuer is untrained in CPR; (b) when an untrained rescuer is receiving telephone instruction from the ambulance dispatcher; (c) if the rescuer is unable or unwilling to perform rescue breathing.

CPR in children

Full details of resuscitation techniques for use in children will be found in Chapter 9. The following advice is for those who do not have a duty to respond to paediatric emergencies (usually health professional teams).

For ease of teaching and retention laypeople should be taught that the adult sequence may also be used for children (Figure 9) who are not responsive and not breathing.

Most laypeople taught CPR should perform the adult sequence on infants and children, BUT compress to one-third depth of chest. Physical damage following CPR in children is very rare. Therefore, do not be afraid that you may push too hard.

Non-specialists, those laypeople who have responsibility for children (e.g. teachers, lifeguards, school nurses) or who are more likely to witness cardiac arrest in children (e.g. parents, child minders), and those who simply wish to extend their training may be taught to modify the adult sequence by (a) giving 5 initial breaths at the start of CPR, then continuing with a 30:2 compression:ventilation ratio; (b) compressing the child's chest to one-third its depth, using 2 fingers or 1 hand as appropriate to obtain the necessary depth; (c) performing CPR for about 1 min before leaving for help if this is necessary for a lone rescuer. If at all possible, training on a child manikin should be offered.

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