Definitions
Cardiac arrest is defined as the sudden and complete loss of cardiac output due to asystole, ventricular fibrillation, ventricular tachycardia or loss of mechanical cardiac function.3 The clinical diagnosis is based upon the patient being unconscious and pulseless (breathing can take some time to stop after cardiac arrest). Death is virtually inevitable unless effective treatment is given.
Cardiopulmonary resuscitation (CPR) or basic life support (BLS) consists of a series of manoeuvres that attempt to maintain a low level of circulation to perfuse the vital organs such as the heart and brain until more definitive treatment such as defibrillation or advanced life support can be given or there is a return of spontaneous circulation.1,4 For the purposes of this chapter CPR and BLS are used interchangeably.
The chain of survival
The chain of survival (Figure 3.1) is a sequence of events that are necessary to maximise the chances of survival following a cardiac arrest. The chain is based upon the principle that a patient in cardiac arrest is most likely to survive if all of the links in the chain are present and timely. The focus of this chapter will be upon steps 1 and two of the chain. Further information regarding the following steps of the chain is provided in other chapters (e.g. defibrillation).
Figure 3.1 The chain of survival. Reproduced with kind permission of Laerdal Medical Ltd.
The importance of CPR
CPR is aimed at providing oxygen delivery to vital organs until more definitive treatment or spontaneous circulation can be restored and is therefore of great significance in the management of cardiac arrest. Several studies have supported the role of early CPR in cardiac arrest, with improved outcomes, including the role of bystander CPR in successful cardiac arrest outcome.5–9 It is believed that successful outcomes from cardiac arrest are improved by CPR due to the creation of a ‘bridge to successful defibrillation’, whereby CPR prolongs the phase of ventricular fibrillation which has a higher successful resuscitation rate.1,10 With such a wealth of evidence supporting the use of CPR in cardiac arrest and subsequent outcomes, a clear understanding of the process of CPR is imperative.
Lay rescuers versus healthcare providers
There is a distinct difference between the provision of CPR between the trained healthcare provider and the lay person. It is important to bear this in mind when attending a scene where bystander CPR is underway. This chapter will describe the process of CPR for the trained healthcare provider, however the main differences between the processes are highlighted below:
- Lay rescuers are not taught to assess for pulses or signs of life. The lay rescuer may commence CPR in an unresponsive patient with abnormal breathing.
- The lay rescuer may not perform rescue breathing or ‘mouth-to-mouth’ ventilation due to fears of contamination.13
The change to recent guidelines for the lay person not to assess for a pulse or absence of breathing is a result of studies into the ability of the lay person (and healthcare professionals) to undertake carotid pulse checks.11 In addition confusion has been found over the presence of agonal breathing and an association as normal breathing.12 Therefore it may be found that the lay person has undertaken CPR on a premise that differs from the trained healthcare provider.
Adult basic life support
This section contains the guidelines for single rescuer CPR. The recommendations of this are based upon the 2005 International Consensus Conference on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science document13 and European Resuscitation Council Guidelines,1 with further supporting evidence included.
Figure 3.2 shows the adult CPR algorithm, whilst it is designed for the lay rescuer the principles remain the same for the trained healthcare provider. This chapter will outline the process of basic life support, for further information and guidance upon principles raised such as airway management and defibrillation please see the relevant chapters of this text.
Figure 3.2 Adult basic life support algorithm. Reproduced with permission of Resuscitation Council UK.
The main principle of basic and advanced life support is the adherence to the ABC approach.
A Airway
B Breathing
C Circulation
You should remain on each level until any major deficiencies are rectified. Source: Resuscitation Council UK.1
Sequence of BLS
- This is of undoubted importance to all healthcare providers and lay persons.
- Gently shake the shoulders and ask loudly ‘are you all right?’
- Consider any suggestion of cervical spine injury and provide support for the c-spine during shaking the shoulders as required. This can be achieved by holding the head still with one hand whilst shaking the patient’s shoulders.
- Urgent medical assessment may be required.
- During this time consider oxygen therapy, clinical assessment and treatment.
- Consider requesting assistance.
- Turn the patient onto their back (considering c-spine injury).
- Open the airway, if no c-spine injury suspicion use the head tilt and chin lift technique. See airway management chapter for guidance.
- If there is suspicion of c-spine injury consider a jaw thrust or chin lift with assistance from others to manually stabilise the head and neck. If a life threatening airway obstruction persists, despite airway manoeuvres add a head tilt gently a small amount at a time. The lack of patency of an airway overrides the hypothetical risk of a cervical spine injury.
- Look for chest movement.
- Listen for breath sounds.
- Feel for air upon your cheek.
- In the first few minutes after cardiac arrest a victim may be breathing (barely) or be taking infrequent noisy gasps, this shouldn’t be confused for normal breathing.1,13
- There may be other signs of life such as movement which may contradict the absence of a palpable pulse. Remember to view the patient as a whole.
- Turn the patient into the recovery position. This is discussed later in the chapter.
- Continue to monitor airway status, breathing and pulse.
- Continue to perform a medical assessment and required interventions.
- Ventilate the patient’s lungs using a bag-valve-mask, pocket mask or mouth to mouth ventilations. This should be at a rate of 10 min-1, the easiest way to determine this is to provide a breath when you would need a breath. Be careful not to hyperventilate or over-inflate.
- To provide mouth-to-mouth ventilation:
- Commence CPR.
- Kneel beside the patient. Place the heel of one hand in the centre of the chest.
- Place the heel of the other hand on top of the other hand.
- Interlock the fingers and ensure that pressure is not applied over the ribs but over the sternum (Figure 3.3). Do not apply pressure over the upper abdomen or lower part of the sternum.
- Position yourself vertically above the victim’s chest with the arms straight.
- Press the sternum down approximately 4–5 cm.
- After each compression release the pressure off of the chest, without losing contact between the hands and the sternum.
- Repeat at a rate of 100 min−1 for 30 compressions.
- Compression and release should take equal amounts of time.
- After 30 compressions, re-open the airway and provide two ventilations using a bag-valve mask, pocket mask or mouth to mouth ventilation.
- Use an inspiratory time of 1 second and provide enough volume to produce a chest rise as in normal breathing.
- Allow for the chest to fall prior to the second ventilation.
- If a ventilation fails repeat until successful up to a maximum of five attempts.
Figure 3.3 Positioning the hands for chest compressions.
Figure 3.4 Overhead CPR.
- Note that the hands must be positioned so that the heel of the bottom hand is over the sternum as with the ‘standard’ chest compression position. This reduces pressure over the ribs and ensures compressions are delivered to the correct area with reduced likelihood of rib fracture.
Rescuer danger
The safety of the rescuer and victim are paramount during resuscitation. There have been a relative few incidences of rescuers suffering adverse effects from CPR, with isolated reports of infections such as tuberculosis and severe acute respiratory distress syndrome being transmitted via mouth-to-mouth ventilation.1 There have been no reported incidences of HIV being transmitted during CPR. With the availability of filters, barrier devices and one way valves it is recommended that rescuers take appropriate precautions and risk assess each situation.
Initial rescue breaths
During the first few minutes following non-asphyxial cardiac arrest blood oxygen remains high and lack of oxygenation to the vital organs is limited more by the lack of cardiac output. It is therefore less important to provide initial rescue breaths than to provide chest compressions.14 In addition it is recognised that rescuers are often unwilling to undertake mouth-to-mouth ventilation, therefore the emphasis has been placed upon effective chest compressions as opposed to ventilation.
Chest compressions
Chest compressions produce blood flow by increasing intrathoracic pressure and directly compressing the heart.13 Chest compressions are able to produce systolic blood pressures of 60–80 mmHg, this enables a crucial amount of blood flow to the vital organs.15 There is little evidence to support the specific placement of the hands during chest compressions, however the placement of the hands in the current position is aimed at being simplistic and reducing injury to underlying tissues.16
Chest compression depth is aimed at providing an adequate intra-thoracic pressure and compression of the heart to allow for the forcing of blood to the vital organs. The recommended depth for adult chest compression is 4–5 cm. The majority of evidence that supports the recommended compression depth is based upon animal studies due to the ethical nature of such research. It is believed that blood flow increases with compression force and depth during CPR, thus improving circulation.17,18 However studies suggest that in both out of hospital cardiac arrest and in hospital cardiac arrest that compression depths are often inadequate.19 It is suggested in a small scale animal study that a reduction in compression depth of 30% can significantly reduce coronary perfusion pressure and subsequent successful resuscitation.20 However no large scale study has been undertaken to validate these results.
Compression rate is recommended at 100 min-1; this rate is suggested as a speed for compressions not as a target for the number of compressions to be given per minute. This number will be reduced by a number of interruptions such as airway management and defibrillation. The rate of compressions is aimed at maintaining coronary perfusion pressure (CPP) and to allow for the heart to refill with blood following each ejection. Therefore rates that are too slow will allow CPP to fall thus reducing perfusion, whereas rates that are too high will cause reduced cardiac filling and subsequent falls in CPP.13 Whilst there is little evidence to support the recommended rate mathematical models suggests that this rate would achieve best blood flow.13
Compression to ventilation ratio
Insufficient human studies have been undertaken to support a specific compression to ventilation ratio, however a small number of animal studies suggest that a ratio above 15:2 is required to optimise blood flow and oxygen delivery.21 Interruptions to chest compressions should be minimised as stopping chest compressions causes the coronary flow to decrease substantially; on resuming chest compressions, several compressions are necessary before the coronary flow recovers to its previous level. Therefore a ratio of 30 compressions to 2 ventilations is now recommended. Studies utilising this new ratio suggest that CPR has been improved with increased chest compression numbers and reduced time where no CPR was being performed,22 with a perceived benefit to patient outcome being identified.23 However this is yet to be demonstrated in a large scale prospective study.
Compression only CPR
Both lay persons and healthcare professionals are often reluctant to perform mouth-to-mouth ventilation when no device is available to provide protection from contamination. Animal studies have demonstrated that compression only CPR may be as effective as standard CPR in the first few minutes following non-asphyxial cardiac arrest.24 In adults chest compression only CPR has also been demonstrated to be more effective than no CPR on survival rates.25 Recent human observational studies have supported this concept finding no significant differences in survival rates between standard CPR and compression only CPR by lay persons.26,27 It has been suggested but yet to be empirically proven that compression only CPR may provide some level of passive airflow to ventilate patients when the airway is open and elastic recoil of the chest allows for air exchange.28,29 Based upon current evidence it is recommended that compression only CPR should be undertaken as an alternative to no resuscitation.
Basic life support in pregnancy
Cardiac arrest seldom occurs late in pregnancy, however survival from such an event is exceptional.30 There are a number of physiological changes that are peculiar to pregnancy that may affect life support and resuscitative measures, these include relative haemodilution (increased blood volume but relatively less red blood cells); increased gastric pressure due to the enlarged uterus and laryngeal oedema making airway management more difficult.30,31 However in the third trimester the most important physiological change is the compression of the inferior vena cava by the gravid uterus (aortocaval compression). In a full term patient (without known obstetric abnormality) the vena cava may be completely occluded when in the supine position, this is believed to occur in up to 90% of cases and may result in a stroke volume of only 30% of the value expected in a non pregnant patient.32 During cardiac arrest or when in the supine position the gravid uterus in a noticeably pregnant woman should be displaced to the left, either by manually displacing the uterus using two hands or by tilting the pelvis to the left by between 15° and 30° (a wedge or pillow/blankets may be used to achieve this),32 Angles of greater than 30° will greatly inhibit adequate chest compressions and should therefore be avoided. It is recommended that a lateral tilt or manual displacement of the uterus is achieved or considered in any third trimester patient, this can be seen in Figure 3.5.
Figure 3.5 Manual displacement of the uterus.
Mechanical chest compression devices
Following concerns over a variety of factors within CPR, such as provider fatigue and the health and safety issues of performing CPR on a stretcher in a moving ambulance,33 a series of mechanical devices have been designed to provide continuous chest compressions. An example of this is the LUCAS device (Lund University Cardiopulmonary Assist System) which is a gas driven CPR device which provides active compression/decompression (ACD) CPR.34 ACD devices lift the anterior chest actively during decompression. Decreasing intra-thoracic pressure during the decompression phase increases venous return to the heart. This theoretically enables an increased cardiac output, coronary/cerebral perfusion pressures during the compression phase. In randomised animal studies, the use of ACD devices has been demonstrated to improves cardiac output and coronary perfusion pressure.31,35 However throughout a series of studies no consensus has been reached to support a definitive use of or rejection of such devices, suggesting that greater research is required to fully validate the introduction of such devices.36
The recovery position
There are several variations of the recovery position, however there is no single position that will suit all patients and no evidence to support a single recovery position. The recovery position is designed to ensure that the unconscious casualty has a clear unobstructed airway which allows for postural drainage of any secretions or vomit that may occur. The position should be stable and be as near to lateral as possible, with no pressure upon the chest to inhibit breathing.
The Resuscitation Council UK recommends the following sequence of actions to place a patient in the recovery postion.1:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
