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LUCAS: bringing the dead back to life! There are people amongst us today who owe their lives to LUCAS. They were once clinically dead – some for more than an hour – but LUCAS resuscitated them, much more effectively than any human could have done! B ack in February this year, we reported on how defibrillators lifted the success rate of CPR from 5-7% to more than 60% – and urged all businesses to buy one. But as we explained, CPR is not only seldom done correctly, it can very quickly exhaust the persons doing it. Now there’s a CPR “machine” which not only does it correctly but it never gets exhausted and has achieved some rather spectacular successes when used. We’re talking about LUCAS, a mechanical device which administers CPR to a person in sudden cardiac arrest, continuously. It does it better than humans can and it will continue for as long as needed. There are well-documented cases of apparently “dead” people being brought back to life an hour or more after their heart stopped beating. That’s significantly longer than the vast majority of CPR administration, although there are some celebrated cases of MUCH longer (successful) manual CPR. LUCAS was developed at the Lind University in Sweden (hence the first by ROSS two letters of its name!). The full title 18  Silicon Chip is Lind University Cardiopulmonary Assist System (small wonder it’s abbreviated!). In effect, it is a mechanical plunger which is placed directly over the person’s heart and powered by either compressed gas (such as the oxygen carried by all responders) or by internal batteries. It pushes down on the chest a precise amount at a precise speed. That speed is important, because the heart needs to be compressed frequently enough to provide sufficient bloodflow to keep the vital organs (especially the brain) perfused with oxygen from the lungs. The reason that LUCAS is so much better than a human in this regard is that LUCAS keeps going and going at a consistent speed; a human tires rapidly (in as little as a minute) and not only does the speed drop but the depth of compression reduces too. What does it look like? TESTER LUCAS comes in two sections, including a slightly concave piece which lies underneath the person being resussiliconchip.com.au LUCAS, seen on the opposite page on a patient in an emergency room, is assembled from two halves: the yellow backboard, which is passed under the patient, and the top portion which contains the LUCAS machine itself. When the two halves are clipped together, the plunger rests on the patient’s chest. When activated, the pluger compresses the chest (and therefore the heart) against the backboard at a rate of 100 times per minute. citated. Clipping into this is the main “works”, mounted on a curved frame. The idea is that the curved frame and the bottom piece encompass the victim, with the assembly strapped in position so that it doesn’t shift. Mounted in the centre of the top curve is a solenoid-type device which does the resuscitating. It actuates precisely 100 times per minute at a duty cycle of 50%, pushing the “plunger” out of the machine down to a depth of 50mm. The plunger can be moved up and down to take into account differing body sizes. At the end of the plunger is a soft suction cup – it looks similar to a drain-clearing plunger but is made from flexible silicone material. The idea is that this forms a partial vacuum with the chest underneath, to help it “pull up” just as a normally-breathing person’s chest rises and falls but also assists in keeping it located. Once adjusted for position, the plunger operates continuously. This is important in keeping up the blood pressure – not only to the brain but also to the heart itself. The absolute minimum “coronary perfusion pressure” (or CPP) required to return the heart to spontaneous circulation (or ROSC) is usually quoted at 15mm Hg (Hg=mercury, equivalent to 2kPa). One of the reasons that manual CPR, by itself, has such a low success rate is that it only maintains a pressure of around 15-50mm Hg – IF the CPR is maintained continuously and maintained correctly. Even 50mm Hg (~7kPa) is barely enough to perfuse the brain and other organs, though it is much better than nothing at all. One of the main difficulties in doing this is that CPR is so tiring that the first-aider usually cannot continue for more than a couple of minutes and all CPR training includes the mechanism for swapping operators. However, the action of stopping compressions and changing to a fresh person causes the pressure to drop very quickly to very low levels and it takes a while to build it back up again, even to the lower level quoted above. The ‘‘business end’’ of LUCAS: this suction cup plunger pushes down on the chest and assists in bringing it back up. As well as maintaining blood flow . . . . . . this is likely to leave quite a mark! The patient here is shown with defibrillation pads also in position. siliconchip.com.au September 2016  19 One study on pigs (used because of their similarity to humans) showed that with interrupted CPR, CPP fell from 60mm to 15mm HG in just 15 seconds and continued to plummet into negative values until CPR was restarted. Even then, it took 90 seconds to get the CPP back up to the absolute minimum 15mm Hg pressure. No interruption By contrast, in its “continuous” mode, the LUCAS machine simply keeps on going, delivering deep compressions (which increase blood pressure) at a steady rate (which maintains increased blood pressure). LUCAS is able to maintain a CPP of 80-90mm Hg (1112kPa), virtually an impossibility with manual CPR. Studies on pigs showed that those which had LUCAS resuscitation had 100% recovery, while those being given manual CPR had only 25% recovery. It doesn’t tire unless, of course, the 25.9V, 3.3Ah lithium polymer battery (or air supply, depending on model) runs out – in which case, a spare battery or new air supply are fitted, which takes but a few seconds. (LUCAS can also operate with an external power supply. It will recharge the battery as well as power the compressions). Running time is quoted at 45 minutes from a fully charged battery but this will obviously be extended significantly if externally powered. Recharging from flat is quoted at 4 hours maximum but longer if the supply is also powering the LUCAS too. As well as the mains supply, LUCAS also comes with a 12V DC power cable to use in a vehicle (such as an ambulance or even a first responder’s vehicle). 30:2 resuscitation mode In addition to the continuous compressions mentioned above, LUCAS will also operate in the “old” mode of 30 compressions to two breaths administered to the mouth by the first aider (the R – resuscitation – in CPR) . However, modern guidelines eliminate the pause for mouth-to-mouth breaths but use continuous compressions because it has been found that the pausing compressions for two breaths is in itself a cause for the pressure to drop (as detailed above) – the compression and release of the heart also causes the lungs to allow oxygen to enter the lungs and therefore the bloodstream. LUCAS compressions should only be stopped to allow a defibrillator (or other ECG equipment) to analyse and if necessary, shock the patient. A “Pause” button on the operating console makes this quick and easy. The defibrillator pads placed in their normal locations (top right of chest, lower left side) do not interfere with the LUCAS compressions. Mobile operation Once the LUCAS machine is fitted to a patient, it can start work – and that includes someone being carried on All personnel using LUCAS need thorough training, not only in its operation but on the damage it may do if used incorrectly. Here ambulance paramedics are fitting a resuscitation mannequin with LUCAS. 20  Silicon Chip siliconchip.com.au It is not suitable for young children nor patients with a chest width greater than 450mm. Cost Once fitted, LUCAS operation is very simple and is controlled by this panel. (1) tells the operator to adjust the plunger depth. (2) is the universal symbol for a pause – for example, to fit defibrillator pads etc, while the (3) buttons give you the choice of continuous (100 pulses per minute) or 30:2 resuscitation modes. a stretcher or trolley, in the back of an ambulance, even being ferried by a rescue helicopter. Performing manual CPR on someone being transported is notoriously difficult. On a stretcher, it’s almost impossible and even in an ambulance rushing to a hospital there is a great risk to an unrestrained CPR-giver. What are the negatives? Manual CPR has a real risk of broken ribs. Studies have shown this occurs in about one third of cases; indeed, the sternum is fractured in almost 20% of cases. Normally this would not be regarded as a problem, the philosophy being a live patient with a few broken ribs is certainly better than a dead patient with a pristine ribcage! The LUCAS machine can be criticised for the fact that there is no feedback; LUCAS just keeps going. When a manual CPR-giver hears (or sometimes feels) cracking ribs, he/she can adjust their position slightly to minimise dire consequences. (As an aside, when I did my CPR training many years ago, the old St Johns instructor told the class that “done properly, CPR will inevitably break a few ribs. Done improperly, those broken ribs could be pushed into the heart or lungs and kill the patient”). There are limitations on the physical size of the patient, mainly due to the difficulty of getting the LUCAS secured. Taken from the LUCAS manual, this demonstrates that operation is possible even when transporting a patient on a stretcher or trolley; even down stairs in this case (something which is not possible with manual CPR). siliconchip.com.au The other drawback is cost. While the price of the LUCAS machine depends on the model chosen, you can work on a figure of at least $15,000 per machine. Equipping all 850 ambulances and more than 100 hospitals in NSW alone would cost around $15 million. They’re not likely to be required equipment in sporting clubs, surf lifesaving clubs and so on – they would continue to use traditional CPR until the LUCAS-equipped ambulance arrived. Even taking these negatives into account, there is much to recommend the LUCAS machine – just ask the people who are living and breathing right now whose lives have been saved (including one woman clinically dead for 57 minutes; fortunately for her she was in the emergency room at a Sydney hospital which had a LUCAS machine!). LUCAS machines have been installed in a two-year trial between St Vincents and Royal Prince Alfred hospitals and NSW ambulances. (It was RPA hospital where the patient above suffered sudden cardiac arrest). So far the results have been more than encouraging – RPA Hospital Emergency Department Acting Director Dr James Edwards is reported to have said “We have moved from resuscitating the alive to resuscitating the dead!” It has even reached the point where, due to the amount of oxygenated blood being pumped to the brain by LUCAS, patients have effectively regained consciousness even before the heart has started beating by itself. That’s something rarely, if ever, achieved without LUCAS. For further information, see: www.lucas-cpr.com An alternative: the Zoll AutoPulse A somewhat similar product to LUCAS is the Zoll AutoPulse. The big difference between the two is that the Autopulse squeezes the entire chest through the use of a load-distributing ‘‘LifeBand’’, which Zoll claims delivers high-quality compressions with much less risk of broken ribs or sternum. The other main difference is that the AutoPulse operates more slowly than LUCAS, delivering 80 compressions per minute, at 50% duty cycle. It is operated by a 36.3V, 2500mAh lithium-ion battery, with a run time of 30 minutes. Users can select continuous, 30:2 or even 15:2 modes. In the latter two modes, there are two pauses of 1.5 seconds to allow a resuscitation breath to be applied. For further information, see: www.zoll.com SC September 2016  21