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Defibrillators    Save Lives CPR has long been considered the most important first-aid skill you could learn. Arguably it still is – but using an Automated External Defibrillator (AED), is becoming just as important. It can save many more lives! Photo courtesy First Aid Plus by Ross Tester I f we told you that performing CPR (Cardio-Pulmonary Resuscitation, or heart-lung resuscitation) on someone who has suffered sudden cardiac arrest, (SCA) is successful in only about 5-7% of cases, you’d probably be surprised. But you’d probably be even more surprised to learn that adding a defibrillator and CPR training shoots that success rate up to around 60% (some authorities say even higher). The reason is pretty simple: an SCA usually (though not always) doesn’t just stop the heart pumping blood, often it “scrambles” the electrical signals in the heart so that it does not rhythmically beat, even if it wants to (and it does – the heart really wants to start rhythmically beating again). An ECG of someone who has effectively died perhaps half an hour before will sometimes show tiny pulses, albeit too small to be of any use, as the heart valiantly tries to get going again). What happens is that the confused electrical signals send the heart into ventricular fibrillation, where it simply “quivers” rather than pumping blood through its four chambers. Little or no vital oxygen-rich blood gets to the heart and brain and within a few minutes, the cells become damaged. A few min- 14  Silicon Chip siliconchip.com.au Why publish this in SILICON CHIP? If you’re wondering why we have published this feature in what is primarily an electronics magazine, it’s for three very good reasons. (1) Medical Electronics is a fascinating field that not too many know about. Most readers would have heard of defibrillators but we believe that relatively few would know what they are actually used for (apart from the “Packer Whacker” mentioned elsewhere), how they’re used or their limitations. Indeed, most readers’ experience would be the totally false movie and TV show images of a doctor looking at a flat line on an ECG monitor, yelling “clear” and delivering a shock which makes the patient almost jump off the bed! As you read this story, you will begin to understand that defibrillators are highly sophisticated devices which these days do far more than shock someone back to life after a heart attack (which, by the way, they virtually never do unless that is followed by SCA or sudden cardiac arrest!). utes more and the damage becomes permanent and death follows not long after. The experts tell us that the first three to five minutes are vital – that’s how long we have before damage starts to occur. After ten minutes, assuming the victim isn’t also suffering from hypothermia, or reduced temperature, permanent damage is done. Hypothermia slows down the damage but damage is still inevitable in time. 2: SILICON CHIP readership is overwhelmingy those who just might need a defibrillator . . . Whether they are in the position of first-on-the-scene after someone has suffered a SCA or they are the person needing one, we hope that this feature might open a few eyes to the appropriate use of AEDs, now that they are to be found in many public buildings, offices and so on. 3: This is arguably the most important reason! We hope that this article might encourage business owners and managers to buy a defibrillator for their workplace (just as we have now done at SILICON CHIP). We list several defibrillators on page 19 – there are many more. Today’s Public-Access AEDs are designed for totally novice and untrained use – they tell you what to do and how to do it. Most are relatively inexpensive these days (and tax deductible). Just imagine how you would feel if someone in your office/factory/etc died because you hadn’t taken that simple step. What’s wrong with CPR? Absolutely nothing . . . everyone should learn it. CPR is vital in the link to a successful resuscitation outcome, providing oxygenated blood to the heart and brain. CPR simply keeps the blood flowing where the heart isn’t functioning or not functioning properly. The actions of the first aider repeatedly and rapidly pushing down on the chest forces blood through the lungs Doing it (almost!) for real: Manly Life Saving Club members Max Moon and Jonathan Curulli, under the watchful eye of assessor Joe Mastrangelo, undertaking their AED qualification, part of Surf Life Saving’s Advanced Resuscitation Techniques Certificate. The difference between this and the real thing is they’re using a “trainer” AED, obviously on a dummy! siliconchip.com.au February 2016  15 “Heart Attack” (MI; Myocardial Infarction) vs SCA (Sudden Cardiac Arrest) A Sudden Cardiac Arrest (SCA), which can be defibrillated, is quite different to a “heart attack”, more properly known as a Myocardial Infarction (MI), which can’t. Think of SCA as an “electrical problem” and MI as a “plumbing problem”. SCA prevents the heart from beating due to its electrical signals being scrambled, while MI is something physical (for example a blood clot or other blockage) in the arteries which prevents blood flow to the heart itself. The heart is a complex of nerves and muscles in their own right; an MI will usually cause nerve and muscle damage when they are starved of oxygen but will not necessarily be fatal if treated within a reasonable time. Hence MI patients receive “bypasses” and “stents” to allow blood to flow around or through a blocked area. (to pick up oxygen) and to the heart and brain (especially), along with the other organs of the body. There are two problems with this: first of all, CPR is incredibly tiring for the person administering it; so much so that the average person is lucky to effectively compress the heart for two minutes. When you train in CPR, you train to be able to swap with new people to keep going. The rule for administering CPR is that it should be continued for as long as the first aider(s) is/are physically able to continue, or until medical assistance arrives. Victims have been reported to have recovered after more than an hour of CPR – just so long as it is continued with no pauses. Indeed, the record (for someone also suffering severe hypothermia [low body temperature]) is a whopping six hours, 30 minutes. Hypothermia appears to slow down the onset of brain and other tissue damage. (The opposite is also true, by the way – someone who is overheated [hyperthermia] will tend to suffer organ damage faster than someone who is cool.) Good CPR is the only effective method of changing “fine VF” (flatline) to “coarse VF”, which is a shockable rhythm. However CPR will not stop VF – the quivering heart needs an electrical shock to effectively stop the scrambling, On the other hand an SCA if not treated immediately (<5 minutes) will almost always be fatal . An MI may in some cases may trigger an SCA but this is not usual. As far as the first-aider is concerned, CPR, (preferably with a defibrillator) is the only immediate means of treating an SCA, whereas the usual treatment for MI is to sit the patient up and call for medical help. CPR must never be performed on a conscious (ie, MI) patient; indeed modern defibs will not allow you to administer a shock if it detects that a true pulse is present. In all cases, MI or SCA, medical help should be summoned immediately. If you are by yourself, do not stop CPR but yell out until someone else is able to help so that it can start it beating again in a “sinus” rhythm. Enter the defibrillator Believe it or not, the defibrillator’s job is to stop the heart. It supplies a large shock current, directly across the heart, to “freeze” the muscles and so stop it fibrillating. Then, the heart may start beating properly of its own accord. Even if it doesn’t, continuing CPR once the heart is no longer fibrillating gives the victim the best chance of survival. Recent medical research suggests that the first shock is the most important. Until now, most defibs “ramp up” the shock in the belief that higher charges may damage the heart. However, some manufacturers have now switched over to delivering a large shock first up. How much charge? This depends a lot on the manufacturer and how their waveform is set up. This, in turn, is determined by several factors, not the least being the impedance between the pads (ie, across the heart). Early AEDs used a “monophasic” waveform – one where the current went in one direction only. The recommended charge for these was 360J for adult patients (Joules = voltage x current x time). The charge was delivered in a very short time – a couple of milliseconds or so – meaning that the other components, voltage and cur- A defibrillator “Trainer”, such as being used in the photo overleaf, looks and works like a “proper” defib – except for the vital detail that it cannot supply the shock. The trainer gives the same prompts as a real AED, including the spoken instructions. It is clearly labelled as a training device and the pads (also labelled as training electrodes) can be used over and over, unlike the real thing. This trainer is from Cardac Science. At right is the real defibrillator – notice the difference? Apart from not having the “Trainer” and “Not for Human Use” labels, there isn’t one you can see. 16  Silicon Chip siliconchip.com.au rent, were rather high. Most worked on a voltage between about 500V and 2000V DC. Further research showed that a “biphasic” waveform, where the current travelled in both directions, was just as effective but with simpler circuitry, smaller battery and lower weight. These days, the vast majority of AEDs which you come across will be biphasic. The advantage of biphasic waveforms is that the current can be lower than monophasic, resulting in less potential damage to the heart. And with lower power, there are fewer burns and lower battery use. Not only that, the first shock success rate of a biphasic machine is claimed to increase from 60% to 90%. A typical AED might deliver 200 (or more) joules, with a current of perhaps 30A or so delivered over 10ms. The AED also analyses the “dryness” of the skin. With drowning victims, the first aider is taught to dry the skin before applying the pads. This is to both help the pads “stick” and increase the impedance, so the AED can operate more efficiently. There is a shock hazard when the shock is delivered, so the first aider is also taught to ensure that no-one is in contact with the victim (his/herself included!). Note that manufacturers arrange delivery of their charges differently so comparing one with another is not practical nor accurate – none has been demonstrated to be superior to another. How do they work? Public-access defibrillators (ie, those mounted in public areas and designed to be available to anyone, even untrained) all give specific, clear instructions, including where and how to place the pads. Apart from infants, the location is almost invariably on the upper right chest and the lower left side – this gives the best possible path through the heart. Infants usually have the pads placed front and back over the heart. Pacemakers and implanted defibs? While it is quite possible that an external defibrillator will “fry” the electronics in an implanted pacemaker or defibrillator, the Mr Bean’s Defibrillator “Mr Bean Rides Again” Tiger Aspect Productions (1992) You must have seen that episode of “Mr Bean” where Rowan Atkinson attempts to deliver resuscitation to a man in the street using a pair of jumper leads connected to a power pole. Is it art imitates life or life imitates art? We’re not sure, but this has some (OK, miniscule!) factual historical basis: early defibrillators (in hospital operating theatres) actually used 300-1000V AC derived from a step-up transformer connected to the mains, with research funded by the Edison Power Company! The first successful use on a human (a 14-year-old boy being operated on for a congenital chest defect) was in 1947 by Claude Beck, professor of surgery at Case Western Reserve University in Cleveland, Ohio. The boy’s chest was surgically opened and manual cardiac massage was undertaken for 45 minutes before the defibrillator arrived. Beck used paddles on either side of the heart. Closed-chest defibrillation, using 100-150ms shocks <at> >1000V AC, was pioneered in the USSR in the mid-1950s, while portable defibrillators were first used in the late 1950s and early 1960s. Today’s defibrillators deliver a very much shorter shock. By the way, you can see the episode of “Mr Bean Rides Again” on https://www.youtube.com/watch?v=OEwXQE5kh2SE experts all say to ignore them. If the victim is in ventricular fibrillation (VF), it’s obvious that an implanted defib is not doing its job. And a pacemaker can’t work in VF anyway . . . the alternative is to let the victim die. Here’s the procedure If you’ve done a first aid course, you’ll remember the mnenonic DRS ABCD You may also remember that this stands for Danger, Response, Send for Help, Airway, Breathing, Circulation and Defibrillation. The very latest teaching is much simplified and reflects The “Packer Whacker” 25 years ago, media tycoon Kerry Packer suffered an SCA while playing polo – and the one ambulance in NSW which had a defibrillator on board happened to be the one which was standing by for any injuries during the polo match. Packer was revived using that defibrillator and he subsequently donated enough money to the NSW Ambulance Service to equip every ambulance with a defibrillator. These earned the nickname “Packer Whackers” after their famous benefactor. Packer died on Boxing Day, 2005, not from heart disease but from kidney failure. siliconchip.com.au February 2016  17 the expert guidance that heart compressions are all-important to keep the blood flowing; much more so than the older routine, which experience has shown that most people, even trained first-aiders, can get wrong in the panic of a “real” emergency. But before anything else, as with all first aid, you need to get someone reliable to call for medical help (ie, an ambulance). The latest mnenonic, at least overseas (but could change here) is simply CAB This stands for Compressions, Airway and Breathing. This calls for compressions to be commenced as soon as no “signs of life” are detected. These signs have also been simplified – you no longer have to feel for a pulse (that’s the main thing lay people got wrong) but simply establish that the victim is both unconscious and is not breathing. Of course, you still need to ensure the victim (and you!) are in no danger and that the airway is clear but it is now considered imperative to start compressions as soon as possible – ie, immediately! While you’re doing this, have someone else set up the defibrillator. The routine is: 1: Turn on the defibrillator – it will go through a self-checking routine and tell you when it’s ready to go (usually only 5-10 seconds). 2: Attach the pads to the patient, where shown by diagrams on the defibrillator. You will almost certainly need to remove upper body clothing, wetsuits, (most defibs contain a pair of scissors to make this as quick as possible). If the victim is a man with a very hairy chest, use the shaver provided to remove hair under the pad positions. If the victim is a female with an underwire bra, this should also be removed to eliminate any short circuit possibility. 3: Plug in the pad leads to the defibrillator. Two models of AED from the same company, the HeartOn A10 on the left and the A15 on the right. The main difference is that the A15 caters for both adult and child defibrillation without changing pads (courtesy APL Healthcare). 4: Follow the prompts that the defibrillator gives you (almost all these days are spoken words). It will tell you to do several things: briefly stop CPR while it “analyses” the electrical signals coming from the heart via the pads. It will probably tell you to continue CPR, at the rate of 30 compressions to two breaths, until it gives the next instruction. If it wants to deliver a shock, it will tell you. Fully automatic defibs say something like “stand clear. Delivering shock in 3-2-1 (seconds)”. Manual defibs will tell you to “Shock now – press red button”. Even if you don’t know how to perform CPR, in some cases the AED will tell you – either by illustrations or by voice commands. Some advanced models will even tell you if your compressions aren’t deep enough or too slow. Make sure that no-one is touching the victim during analysis or shock – the latter for obvious reasons; the former because the minute electrical signals in some else’s body may in fact interfere with what the AED is trying to read in the victim. Then what? Simply follow the instructions the AED gives you. It may be that it advises that no shock is possible, or that pulse has been restored, or a variety of other scenarios. Hopefully, by this time the ambulance has arrived and they will take over and treatment from you. Buying an AED As we said earlier, we hope that this article may encourage businesses and companies to invest in their own AED and train some of their people to use it. Make sure everyone knows where it is! Or at the prices of these units these days, why not get together with a few neighbours and buy one for home – especially if you have older people either living with you or close by? Remember, though, that sudden cardiac arrest is no respector of age – whether by accident, trauma, disease or illness, it can strike at any age! Acknowledgement: Our thanks to Gary Beauchamp, of First Aid Plus, Sydney (02 9905 0155), for assistance in preparing this feature. On the left is a “normal” beating heart waveform, showing the rhythmical compression which pumps blood. This is referred to as a “sinus” rhythm. Compare this to the uncontrolled and basically useless waveform of a heart in ventricular fibrillation. If not stopped (and that’s the job of a defibrillator) the lack of oxygenated bloodflow will quite quickly start to cause damage to the heart muscles and to the brain (and other organs). Untreated, death is usually the end result. 18  Silicon Chip siliconchip.com.au Which AED is right for YOU? AED Model         Price (Dec15) Replacements (if known)    Pads  Battery Choosing an AED is not all that simple: the best advice we can give is to look for one which has a low “consumables” cost as well as an acceptable initial price. Available From Phone Web First Aid Plus or Defibtech (02) 9905 0155 1300 853 563 www.firstaidplus.com.au www.defibtech.com.au Australian First Aid or APL Healthcare 1300 975 889 1300 727 580 www.australianfirstaid.com.au www.aplhealthcare.com.au HeartOn A15 $2250      (not known)     $2250    (not known) Australian First Aid or APL Healthcare 1300 975 889 1300 727 580 www.australianfirstaid.com.au www.aplhealthcare.com.au Heartsine samaritan PAD 500P (not known)    (not known) $2850     (not known) $2860      (not known) Aero Healthcare or APL Healthcare or Recovery Defibrillators 1800 628 881 1300 727 580 0413 223 472 www.aerohealthcare.com www.aplhealthcare.com.au www.recoverydefibrillators.com.au Heartsine samaritan PAD 360P (not known)     (not known) Aero Healthcare 1800 628 881 www.aerohealthcare.com Recovery Defibrillators 0413 223 472 www.recoverydefibrillators.com.au APL Healthcare 1300 727 580 www.aplhealthcare.com.au Defibtech Lifeline HeartOn A10          $3135      (not known) (not known)      (not known) $1950    $109.95 $199.00 $1950    (not known) Heartsine samaritan PAD 350P $2150     (not known) Heartsine samaritan PAD 300P $2400      (not known) Laerdal HeartStart First Aid $2390   $108 $250 (not known)     (not known) (not known)     (not known) Laerdal or Australian Defibrilators or St John 1800 331 565 1300 333 427 1300 360 455 www.laerdal.com.au www.aeds.com.au www.stjohn.org.au Laerdal HeartStart Frx (not known)     (not known) (not known)     (not known) $3200   $106 $250 Laerdal or Australian Defibrilators or St John 1800 331 565 1300 333 427 1300 360 455 www.laerdal.com.au www.aeds.com.au www.stjohn.org.au First Aid Plus (02) 9905 0155 www.firstaidplus.com.au LifePak CR Plus $2595     (not known) Mindray Beneheart (not known)     (not known) Australian Defibrilators 1300 333 427 www.aeds.com.au Powerheart G3 (not known)     (not known) $2950   $90 $210 $2750       (not known) Cardiac Science or Australian Defibrilators or Recovery Defibrillators (03) 9429 2666 1300 333 427 0413 223 472 www.cardiacscience.com.au www.aeds.com.au www.recoverydefibrillators.com.au Powerheart G5 (not known)     (not known) (not known)     (not known) (not known)     (not known) $2750      (not known) Cardiac Science First Aid Plus or Australian Defibrilators or Recovery Defibrillators (03) 9429 2666 (02) 9905 0155 1300 333 427 0413 223 472 www.cardiacscience.com.au www.firstaidplus.com.au www.aeds.com.au www.recoverydefibrillators.com.au Schiller Fred Easy (not known)     (not known) $1800    $100  Schiller Australia Pty Ltd or Recovery Defibrillators (02) 4954 2442 0413 223 472 www.schiller.com.au www.recoverydefibrillators.com.au Schiller Fred Easyport (not known)     (not known) $2900    $100 $130 Schiller Australia Pty Ltd or Recovery Defibrillators (02) 4954 2442 0413 223 472 www.schiller.com.au www.recoverydefibrillators.com.au Zoll AED Plus (not known)     (not known) $2795     (not known) (not known) (not known) (not known) (not known) Zoll Medical Australia or Defib Shop or Australian Defibrilators or St John 1800 605 555 1300 729 575 1300 333 427 1300 360 455 www.zoll.com.au www.defibshop.com.au www.aeds.com.au www.stjohn.org.au From our research, any of these AEDs appear to be quite suitable for office/factory/building use where untrained users may need to operate them. However, this is not an exhaustive list. These days, most AEDs operate in a similar way but like any electronic device, might go about it their own way! Some, for example, monitor CPR and will tell you if the compression depth is insufficient. Others may record data from the heart which can be used later by a medical professional to review the treatment given and if necessary, tailor ongoing care. The suppliers listed may or may not have stock and may have price changes, especially if they were on special offer when we checked. Any prices shown are ex supplier’s websites. Many do not list prices of either the AEDs or their consumables (they want you to call them!). SC We suggest calling the numbers shown and/or visit their websites to determine features and availability. siliconchip.com.au February 2016  19