Use of the Automated External Defibrillator (AED)
within the Dental Practice
WHY IS AN AED SO IMPORTANT? (“In the UK approximately 30,000 people sustain cardiac arrest outside hospital and are treated by the emergency medical services (EMS) each year. Electrical defibrillation is well established as the only effective therapy for cardiac arrest caused by ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT). The scientific evidence to support early defibrillation is overwhelming; the delay from collapse to delivery of the first shock is the single most important determinant of survival. If defibrillation is delivered promptly, survival rates as high as 75% have been reported. The chances of successful defibrillation decline at a rate of about 10% with each minute of delay, basic life support will help to maintain a shockable rhythm but is not a definitive treatment. The Resuscitation Council (UK) recommends strongly a policy of attempting defibrillation with the minimum of delay in victims of VF/VT cardiac arrest.”) Resuscitation Council (UK) 2012.
CARDIAC ARREST The most common cause for the heart to stop (cardiac arrest) is a “heart attack”, though it is worth noting that a heart attack does not always cause a cardiac arrest. The majority of people who suffer a heart attack stay conscious and survive. “Sudden Cardiac Arrest” (SCA) however, is as its name implies - it can happen at any time - and can affect anyone, even if they are young and seemingly fit.
If a heart attack (or other cause) results in a cardiac arrest, it is usually because it has interrupted the heart’s own electrical impulses, and this causes the heart to act chaotically (VF or VT) instead of beating in a co-ordinated rhythm.
Chain of survival
If a casualty suffers a cardiac arrest, there is a sequence of events that must happen in order for them to stand a chance of survival. This is known as the “Chain of Survival”
1 Early recognition and call for help. Help must be summoned immediately so that the other links in the chain of survival can happen. In the case of a heart attack most casualties look and feel ill for a while, so it is important to call for help if you think a person might have a cardiac arrest so that help can arrive before they collapse. Ideally, send someone else to call for the EMS and tell them to come back as soon as possible. If no-one is available then make the call yourself and tell them you are alone and about to start CPR.
2 Early CPR. The purpose of early CPR is to buy time for the casualty. Chest compressions are needed to push blood around the body and inflations using high-flow oxygen via the Bag Valve Mask (BVM) are needed to put more oxygen in. Early CPR has been proven to more than double the chances of survival. Effective CPR with the use of oxygen increases the chance of successful defibrillation.
3 Early defibrillation. Remember – defibrillation is the only effective treatment for a casualty in cardiac arrest caused by VF or VT, and for every minute it takes to administer the first shock the chance of survival reduces by as much as 10%. Therefore the most important determinant to survival is the delay from collapse to delivery of the first shock.
4 Early advanced care. Early advanced care from professional medical personnel is essential to stabilise the casualty and increase their chance of survival.
THE HEART The heart is a cone shaped hollow muscular organ, and is the only muscle in the body that can create its own electrical impulses.
The two top chambers of the heart (atria) collect blood from the two largest veins in the body and squeeze it into the chambers below (ventricles). The heart has its own primary pacemaker, situated at the top right hand side, which fires electrical impulses through the atria first, making them contract. They then pass through the ventricles, causing them to contract next, which pumps the blood out of the heart. The electrical cells then “recharge” ready for the next wave of electricity.
HEART RHYTHMS The AED will analyse the heart’s rhythm, which is likely to be in one of four, listed below:
Normal (normal sinus rhythm)
Ventricular fibrillation (VF)
Ventricular tachycardia (VT)
No activity (asystole)
In the above reading (asystole) the heart is still. There is no electrical activity at all and occurs after the heart has eventually run out of oxygen. This is commonly referred to as “flatline” and is classed as a “non-shockable rhythm”. The AED can no longer deliver a shock because the heart is now “stopped”.
Therefore, the AED can only work if the heart is in a “shockable rhythm”. Contrary to what many believe, the defibrillation shock does not “jump start” a heart once it has stopped. The shock is designed to make the heart’s electrical cells re-charge, which can stop the fibrillation and brings the heart to a standstill. Once fibrillation is stopped, the heart’s own pacemaker should start to send normal impulses once again. Maybe the best way of describing it is as similar to “rebooting” a computer.
When someone suffers a heart attack, an area of the heart loses its blood supply and dies as a result. However, while this is happening, the dying area becomes very unstable and can send its own electrical impulses, and these “mis-fires” interrupt the normal electrical activity of the heart, causing it to beat too rapidly (ventricular tachycardia), irregularly (ventricular fibrillation) or both. This can result in the whole electrical system becoming disrupted. Instead of beating in a co-ordinated rhythm, the electrical cells start firing independently, stopping the heart from pumping blood effectively. Some cardiac arrests are due to extreme slowing of the heart. This is called bradycardia.
Other factors besides heart disease and heart attack can cause cardiac arrest. They include respiratory arrest, electrocution, drowning, choking and trauma. Sudden cardiac arrest can also occur without any known cause.
Remember, there are two common misconceptions about the use of defibrillators:
1 “A defibrillator starts the heart beating again once it stops”
The defibrillator actually stops the heart during fibrillation so that the heart can restore a normal rhythm. CPR can help to maintain a “shockable rhythm” for as long as possible, however, the longer the defibrillator takes to arrive, the more likely the heart will have become asystolic (a non-shockable rhythm.) A “flatline” is the common name for an asystolic rhythm, so cannot be shocked. The chance of survival is as high as 75% if the first shock can be delivered within the first 3-5 minutes. However, after this time the survival rate drops by approximately 10% per minute.
2 “There is a risk that the defibrillator will shock a heart that is beating normally, and cause it to stop”
A normally beating heart (normal sinus rhythm) is also a non-shockable rhythm. Therefore the defibrillator will not administer a shock if attached to a casualty whose heart is still beating with a normal rhythm.
WHO CAN USE AN AED? The Resuscitation Council (UK) recommends that “All healthcare professionals should consider the use of an AED to be an integral component of BLS. Untrained employees working in healthcare establishments should not be prevented from using an AED if they are confronted with a patient in cardiac arrest. The administration of a defibrillatory shock should not be delayed while waiting for a more highly trained personnel to arrive.”
“An AED can be used safely and effectively without previous training. Therefore, the use of an AED should not be restricted to trained rescuers. However, training should be encouraged to help improve the time to shock delivery and correct pad placement.” The Resuscitation Council (UK) also recommends that an AED be made available wherever crowds gather, for example at sports stadiums, theatres, cinemas, shopping centres, airports, train and bus stations etc.
- The frequency of cardiac arrest is such that there is a reasonable probability of the use of an AED at least once in five years.
- The time from call out of the EMS to delivery of first shock cannot be achieved within 5 minutes (most of UK).
- The time from collapse of a casualty until on-site AED is used should be within 5 minutes.
- The Resuscitation Council (UK) recommends that if a defibrillator is present, use IMMEDIATELY (do not wait to use an AED whilst CPR is carried out).
TYPES OF AUTOMATED EXTERNAL DEFIBRILLATOR “AEDs are sophisticated, reliable, safe, computerised devices that deliver electric shocks to victims of cardiac arrest when the ECG rhythm is one that is likely to respond to a shock. Simplicity of operation is a key feature: controls are kept to a minimum, voice and visual prompts guide rescuers. Modern AEDs are suitable for use by both lay rescuers and healthcare professionals”
All AEDs analyse the victim’s ECG rhythm and determine the need for a shock. The semi-automatic AED indicates the need for a shock, which is delivered by the operator, while the fully automatic AED administers the shock without the need for intervention by the operator.” R C (UK) 2012.
Although AEDs are designed to do the same thing, they can be very different in design, colour, size, number of buttons and use of voice prompt language. It is essential, therefore, that you are familiar with the particular unit you may have within your practice. If you are considering obtaining an AED, the following may be useful when making a decision as to which to have within your practice.
- Buttons While some AEDs only have one button that will deliver the shock, some units can have up to three buttons;
- One to turn the unit on
- One to analyse the rhythm
- One to deliver the shock
- Size AEDs are about the size of a small laptop computer and can weigh approx 2 kilos. Units have either a carrying handle attached or come in a carry case which is a handy place to keep spare electrodes, battery packs and rescue ready packs (see below)
- Electrodes These are stored with the AED and are wrapped in foil. Some AEDs have the electrodes already attached whilst others are separate and need connecting once the AED is switched on. (There will be a voice command to tell you when and where to attach the lead). The electrodes have a shelf life of approx 2 years.
- Battery Most AEDs have one large lithium battery pack which needs replacing every 2-7 years depending on the unit. Some use standard camera batteries which are cheaper to replace.
- Status Indicator Most AEDs have some form of status indicator which shows that the machine is ready for use. AEDs perform a variety of daily, weekly and monthly self-checks to ensure battery levels are OK, that electrodes are attached properly, that software isn’t malfunctioning and whether a service is due or not. The AED will flash or beep to indicate that a fault has been located. It is vital, therefore, that staff understand the need to ensure that their AED is ready at all times.
RESCUE PACK It is advisable to carry the following accessories with the AED;
- Scissors You will probably need to cut open clothing to expose the bare chest. It’s therefore advisable to have a strong pair that are capable of cutting through thick material, such as “tough cut” safety scissors.
- Razor A good quality disposable razor is useful to remove any excessive chest hair where the pads need to be applied to ensure that they stick closely to the skin.
- Small towel/flannel It is common for a casualty suffering a heart attack to sweat profusely and the chest must be dry to ensure a secure adhesion of the pads.
It is also recommended that you also include the following:
- Spare AED pads If a pad gets torn, or fails to stick properly, then having spare pads available will save time.
- Paediatric pads Most machines require paediatric pads to be connected if using the AED on a child (1-8 years).
- Protective gloves Always wear protective gloves when dealing with the casualty.
AED SAFETY CONSIDERATIONS
- Jewellery Take care not to place pads over jewellery such as a necklace. This would conduct the electricity and burn the casualty. There is no need to remove piercings, but ensure that pads are not placed over them.
- Medication patches Some heart patients wear a “glyceryl tri-nitrate” (GTN) patch which may explode if electricity is passed through it, so remove ALL visible medication patches as a precaution.
- Implanted devices Some heart patients may have a pacemaker or defibrillator implanted. These can usually be seen or felt just below the left collar bone, which is not in the way of the pads and care must be taken not to place the pads over them.
- Supplemental oxygen There are no reports of fires caused by sparking where defibrillation was delivered using adhesive pads. If oxygen is being delivered by a face mask, remove the mask and place it at least one metre away before delivering the shock. Do not allow this to delay shock delivery.
- Defibrillation if the victim is wet As long as there is no direct contact between the user and the victim when the shock is delivered, there is no direct pathway that the electricity can take that would cause the user to experience a shock. Recent tests have shown that the risk of accidental shock is low, because the electricity only wants to travel from one pad to another, not to “earth” like mains electricity. Do not delay defibrillation because the casualty is on a wet, or metal surface – providing the chest is dry it is safe to deliver the shock.
- Inappropriate shock The casualty needs to be motionless to analyse rhythms. Do not use on a casualty who is fitting (violent jerking movements) and ensure vibrating machinery is switched off whenever possible.
- Pad positioning Recent studies have found that the position of the pad on the lower left chest can affect the effectiveness of the shock. Ensure the pad is placed around the side of the chest and not on the front. This ensures the maximum electricity flows through the heart rather than across the chest surface. Most AEDs will inform the rescuer if the pads are incorrectly positioned, however, training will ensure that all staff know exactly where they should go. Although most AED pads are labelled left and right, or carry a picture of their correct placement, it does not matter if their positions are reversed. It is important for staff to understand that if this happens “in error” the pads should not be removed and replaced as this wastes time and they may not adhere adequately when re-attached.
- CPR before defibrillation Provide good quality CPR while the AED is brought to the scene. Continue CPR whilst the machine is turned on, then follow the voice and visual prompts. Giving a specified period of CPR, as a routine before rhythm analysis and shock delivery, is not recommended. If you are on your own, ring for the EMS first, and then fetch the AED, switch it on and apply pads, even if this means delaying the onset of CPR, as the first shock should be delivered within 3-5 minutes, if possible.
- Minimise interruptions in CPR The importance of early, uninterrupted chest compressions is emphasised throughout the Resuscitation Council (UK) guidelines. Interrupt CPR only when it is necessary to analyse the rhythm and deliver a shock. When more than one rescuer is present, the rescuer operating the AED applies the electrodes while the other(s) continue CPR. The AED operator delivers a shock as soon as the shock is advised, ensuring that no-one is in contact with the casualty.
STORAGE AND USE OF AEDS “AEDs should be stored in locations that are immediately accessible to rescuers; they should not be stored in locked cabinets as this may delay deployment. Use of the UK standardised AED sign (see below) is encouraged, to highlight the location of an AED. People with no previous training have used AEDs safely and effectively. While it is highly desirable that those who may be called upon to use an AED should be trained in their use, and keep their skills up to date, circumstances can dictate that if no trained operator (or a trained operator whose certificate of training has expired) is present at the site of an emergency no inhibitions should be placed on any person willing to use an AED” RC (UK) 2012.
PUBLIC ACCESS DEFIBRILLATION (PAD) “Public access defibrillation is the term used to describe the use of AEDs by laypeople. Two strategies are used. Firstly. AEDs are installed in public places and used by people nearby. Impressive results have been reported with survival rates as high as 74% with fast response times often possible when an AED is nearby. The second strategy uses first responders despatched by an ambulance control centre when they may reach a patient quicker than a conventional ambulance” RC(UK) 2012
RESUSCITATION WITH THE USE OF AN AED
- Make sure that the casualty, any bystanders, and you are safe
CHECK FOR RESPONSE
- If there is no response, shout for help immediately
- Carefully open the airway by using “head tilt” and “chin lift”
- Keeping the airway open, look, listen and feel to see if the breathing is “normal”. Take no more than 10 seconds to do this
- If the casualty is breathing “normally” place them into the recovery position
IF THE CASUALTY IS NOT BREATHING NORMALLY:
- If you are on your own, call for EMS (emergency services) AND GET THE AED
- If you have help – start CPR immediately whilst your helper(s) call for EMS and get the AED. If there is anyone else available send them for the oxygen and breathing apparatus
CONTINUE CPR USING RATIO OF 30 COMPRESSIONS TO 2 INFLATIONS UNTIL THE AED ARRIVES
AS SOON AS THE AED ARRIVES:
- Continue CPR if more than one rescuer present
- Switch on the AED immediately and follow the voice prompts:
- Attach the leads to the AED if necessary and attach the pads to the casualty’s bare chest after cutting through clothing, doing this whilst the other rescuer(s) continue CPR if possible (remember – every minute counts)
- You may need to towel dry or shave the chest so that the pads stick properly. Only shave excessive hair over where the pads are to be positioned and don’t delay defibrillation if a razor is not available
- To place the pads, peel one pad from the plastic backing and place it to the right of the sternum (breast bone) just below the casualty’s right clavicle (collarbone) as shown on the pad
- Peel the second pad from the backing and place on the lower chest wall on the left, just below the apex of the heart, as shown on the pad DO NOT REMOVE THE PADS IF YOU HAVE PLACED THEM THE WRONG WAY ROUND – THE AED WILL STILL WORK
- Whilst the AED analyses the rhythm – stop CPR and ensure that no-one is touching the casualty by shouting “STOP CPR”. YOU WILL NOT GET A SHOCK AT THIS POINT – HOWEVER, THE AED CANNOT SUCCESSFULLY DETERMINE THE RHYTHM IF THE CASUALTY IS MOVING. IF YOU ARE STILL TOUCHING THE CASUALTY THE AED MAY DETECT YOUR OWN RHYTHM ALSO AND THIS WILL CAUSE A DELAY
IF A SHOCK IS ADVISED:
- Ensure that nobody touches the casualty. The AED will take a few seconds to fully charge. Shout “STAY CLEAR”
- Once the AED advises you to press the button to deliver the shock check the casualty from head to toe to ensure everyone is clear, shout “SHOCKING NOW” and press the shock button. REMEMBER THAT A FULLY AUTOMATIC AED WILL DELIVER THE SHOCK WITHOUT THE NEED TO PRESS A BUTTON SO BE CLEAR IN YOUR INSTRUCTIONS TO OTHER RESCUERS
- Continue as directed by the voice/visual prompts
- Minimise, as far as possible, interruptions to chest compressions
IF A SHOCK IS NOT ADVISED:
- Immediately resume CPR using the ratio of 30 compressions to 2 inflations
- Continue as directed by the voice/visual prompts
CONTINUE TO FOLLOW THE AED PROMPTS UNTIL:
- Qualified help arrives and takes over OR
- The casualty starts to show signs of regaining consciousness, such as coughing, opening the eyes, speaking, or moving purposefully AND starts to breath normally OR
ALWAYS LEAVE THE ELECTRODE PADS ON THE CASUALTY EVEN IF THEY APPEAR TO HAVE RECOVERED AS THEIR CONDITION MAY QUICKLY DETERIORATE
- The instructions above follow the latest Resuscitation Council (UK) guidelines published in October 2010. Some older AEDs (pre 2006) may use older guidelines. If you have an AED that you think may be pre 2006 check with your AED supplier if an update is available. If your AED follows older guidelines it is still acceptable to use it (following the voice prompts, as stated above) as defibrillation using older guidelines is better than no defibrillation at all.
CORRECT PLACEMENT OF ELECTRODE PADS ON AN ADULT
UK STANDARDISED AED SIGN
Wendy Berridge delivers CPR, Medical Emergencies and AED training to dental practices throughout Yorkshire and Lincolnshire.