Understanding Cardiac Arrest, CPR & AEDs

Recently a sound engineer, Simon Daniels, hit headlines for saving former football player and England manager Glenn Hoddle at the BT Sport studio in London. Daniels performed CPR and used a defibrillator on Hoddle before paramedics arrived. Without this quick intervention before the arrival of emergency services, Hoddle may not have survived. Unfortunately, a lack of knowledge and confidence in how to handle cardiac arrest means many bystanders fail to act.

CPR is amongst the simplest and most important of all first aid skills, but should someone experience cardiac arrest, use of an Automated External Defibrillator (AED) can boost their chances of survival much more than CPR alone. An AED cannot be effective without good-quality CPR, but conversely, CPR alone is very unlikely to restore normal heart function.

Understanding cardiac arrest and CPR

Cardiac arrest is when the heart stops pumping blood (many people confuse this with a heart attack – while a heart attack may lead to cardiac arrest, during a heart attack the casualty is still responsive and breathing). This causes a rapid loss of consciousness, meaning the casualty becomes completely unresponsive, and their breathing becomes highly abnormal or ceases altogether. If someone does not respond to any external stimulus and is not breathing normally, you must always begin CPR.

While CPR can, rarely, lead to a return of spontaneous circulation, with the casualty’s heart ‘restarting’ and subsequently a resumption in normal breathing and possibly responsiveness, the main aim of CPR is to keep oxygen flowing around the body (in particular, to the brain) until medical treatment can restore heart function.

CPR consists of chest compressions, which are intended to manually pump the heart and circulate blood around the body, combined with ‘rescue breaths’, which aims to breathe for the patient and add more oxygen to the blood. However, hands-only CPR is far more preferable to no CPR at all and may be more suitable for those without training.

What does CPR do?

While CPR alone is unlikely to restore the heart to normal function, it is absolutely crucial to survival in cases of cardiac arrest. This is because it restores a partial flow of oxygenated blood to the brain and heart, delaying tissue death and extending the timespan in which successful resuscitation is possible. Without oxygen, brain tissue dies within minutes, leaving the casualty permanently brain damaged if they survive at all. Cardiac arrest is a race against time for the casualty and good CPR can buy them more time.

Without CPR by bystanders until the arrival of emergency services, even if they are summoned promptly, chances of survival are vanishingly small. The target response time for NHS ambulances is 7 minutes. Even if this is achieved, by 7 minutes without oxygen permanent brain damage has often already occurred, as brain cells begin shut down after 4-6 minutes. In most circumstances, after ten minutes without oxygen, brain cells cease to function altogether, resulting in death or severe neurological damage.

To delay this, CPR must be commenced as early as possible; the earlier this starts, the more likely the casualty is to survive and to survive without permanent disability. Should emergency services take longer than 6 minutes to arrive, continuous CPR from bystanders, preferably combined with use of an AED, is the only thing which can give a casualty a chance of survival. CPR must always be continued until emergency services arrive or, in rare cases, until the casualty begins to breathe normally or become responsive.

Understanding this is key, because people may mistake CPR as being intended to restart the heart and give up hope if no responsiveness is achieved and emergency services are slow to arrive. However, due to good-quality CPR and expert medical care, people have been known to be resuscitated after hours without a heartbeat. Keeping enough oxygenated blood flowing around the body can keep the cells from dying off for a long time until their heart begins to beat for itself.

It is also vital to understand that if someone is in cardiac arrest and needs CPR, it is impossible to make things worse for them, by breaking their ribs for example. Correct CPR often does crack ribs. However, as long as somebody is unresponsive and not breathing, they are effectively dead and have absolutely zero chance of recovery without first aid and/or medical attention. If bystanders do cause injuries to the casualty during CPR, they cannot get into legal trouble for doing so – there has never been an incidence of this in the United Kingdom.

How can an AED further boost chances of survival?

There is more than one cause of cardiac arrest. In ventricular fibrillation, the heart quivers rather than beats due to abnormal electrical activity. In pulseless ventricular tachycardia, the heart beats quickly and regularly but without pumping blood around the body. These are known as ‘shockable’ cardiac arrests, meaning that a defibrillator can restore normal electrical activity to the heart so it begins to pump correctly.

In these instances, emergency services would also use a defibrillator to attempt to save a casualty’s life. However, the earlier this is performed, the greater the chances of survival, as this limits the amount of time the brain and other vital organs have gone without a full supply of oxygenated blood. An AED is designed to be used by bystanders at the scene before emergency services arrive. The device, once powered on, instructs users how to correctly attach the machine’s electrode pads to the casualty’s chest, analyses the casualty’s heart rhythm, and then gives a potentially lifesaving shock either completely automatically or at the press of a button.

An AED cannot be effective without CPR; CPR is vital to keep the casualty sufficiently oxygenated up until the point their heart is restarted – this can require multiple shocks so CPR must continue between shocks too. While an AED shock does not guarantee survival, it does greatly increase the chances compared to later defibrillation by emergency services.

In some cases, an AED will analyse the casualty’s heart rhythm and decide a shock is not recommended. This is because there are two ‘non-shockable’ forms of cardiac arrest: asystole and pulseless electrical activity. Only CPR and professional medical help can give casualties in these situations a chance of survival. It’s therefore vital that CPR continues with minimal interruptions until help arrives. Most AEDs will continuously guide the responder’s CPR to help them with their technique.

Because it’s impossible to tell whether a cardiac arrest is shockable or non-shockable without the use of equipment, you should always send someone to locate and retrieve an AED whilst you commence CPR.

Just how effective are CPR and AEDs?

Determining the statistical effectiveness of CPR and AED use is difficult, as it isn’t possible to do lab studies for obvious reasons. It has been suggested that bystander CPR can increase survival rates by 2-3 times. However, unfortunately it’s all too common for cardiac arrest victims to go without bystander CPR, and use of AEDs is rare. A Resuscitation Council Report suggests that only 30-40% of cardiac arrest victims receive CPR by bystanders, and ultimately only 8% of out-of-hospital cardiac arrest victims survive to be discharged from hospital.

AED use is even rarer – used in just 2% of out-of-hospital cardiac arrests. AEDs are now found in many public places, but many people lack the knowledge and confidence to seek them out and use them. Every minute that goes by without defibrillation lowers survival chances by 10% for those with a shockable heart rhythm. However, early administration of CPR combined with an AED can raise survival chances to as high as 40%!

While ensuring more people throughout the country have the training to recognise cardiac arrest, perform good CPR and use an AED where possible is essential, it’s equally important to ensure they have the confidence to apply this knowledge in real-life situations.

Our training

CPR is a common feature of basic first aid training. Our courses teach people to carry out the primary survey and ascertain when CPR is required, and how to perform CPR correctly. While emergency services will talk people through CPR on the phone if they’re untrained, good-quality chest compressions are key to survival and trained responders are more likely to be able to deliver this. Trained first aiders are much more likely to have the confidence to act, which is important when so many people go without help from bystanders. CPR is a key first aid skill and is taught in all our courses, including our half day basic first aid training course.

AED training is also very useful for any organisation that has AEDs on site. Although AEDs are designed to be used by anyone and to talk users through the defibrillation process, a lack of knowledge and understanding prevents people from recognising when an AED should be used or having the confidence to use one. Giving people the chance to train with AEDs in a controlled environment familiarises them with the devices. Once they understand how safe and easy it is to use an AED, they are much more likely to do so. AED use forms part of our 3 day first aid at work course, but we also offer a special half day defibrillator training course which is perfect for augmenting employees’ existing first aid skills or ensuring everyone on site is able to use these lifesaving devices even if they aren’t otherwise first aid trained.

You can browse all our first aid courses at https://www.firstaidtraining.co.uk/courses/.

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