It is known that most cardiac arrests occur in out-of-hospital (OOH) environments (Steen et al, 2005), with the incidence across Europe cited as 66 per 100 000 of the population (Atwood et al, 2005) and the frequency of OOH cardiac arrest in the UK at 60 000 per year (Perkins and Cooke, 2013). Overall survival rates from OOH cardiac arrest, for which a resuscitation attempt is made, vary regionally, with recent reports from 6.8% (Kendall et al, 2012) and 10.9% (London Ambulance Service NHS Trust, 2012), for example.
The only viable response to a cardiac arrest is cardiopulmonary resuscitation. Chest compressions have long been highlighted as the pre-eminent manoeuvre in resuscitation attempts, except for the few cases for which defibrillation is immediately available at the time of the arrest. The European Resuscitation Council (ERC) guidelines of 2010 emphasise their importance and the consensus statement from the American Heart Association recently further validated the place of high quality compressions at the forefront of resuscitation success (Meaney et al, 2013).
In this clinical forum we consider the place of automated (or ‘mechanical’) chest compression devices (ACDs) as an adjunct in pre-hospital resuscitation and have assembled a variety of perspectives to examine this in comparison to manual chest compression. Paramedics are likely to remain at the forefront of resuscitation attempts in the community and in implementing developments that have the potential to increase survival. It is therefore important for the pre-hospital clinician to be aware of the debate around such developments.
The key components to the efficacy of chest compressions are rate (at least 100 per minute but not exceeding 120 per minute), complete decompression, minimisation of interruptions to chest compressions (‘time off the chest’) and depth (5–6 cm). Yet this last point of the depth of compression alone has given rise to concerns over the speed with which rescuers fatigue—apparently within the second minute (McDonald et al, 2013)— and also the degree of efficiency with which smaller or ‘lightweight’ rescuers are able to perform the compressions (Krikscionaitiene et al, 2013). It is also known that compressions delivered in transit—in the back of an ambulance—are compromised (Glasser et al, 2012).
Might there then be a call for a mechanical device that is able to be pre-programmed reliably to deliver the requisite depth and rate of compression with full release—all maintained en route to hospital as well as on scene? If the device is easily employed and minimises ‘time off the chest’ then it could free a member of what can often be a small paramedic team—with quite possibly skill-mix as an issue—to engage in other issues such as drug delivery or even speaking with family or onlookers?
Of the available devices, which do you think is the most useful?
Douglas Chamberlain replies:
Although other designs are available, only two—Autopulse and LUCAS—are commonly used within the United Kingdom. It is impossible to say which is the more useful. No study has offered a direct comparison, nor is one likely to be performed. The recent results of trials against conventional CPR have had similar results of equivalence or near equivalence; this also argues against any important advantage of one device over the other. Choice is therefore a matter of individual preference. They do, however, have slightly different modes of action: Autopulse provides more circumferential compression whereas LUCAS relies on direct sternal compression and retraction. It may be that the shape of the thorax and the distance of the heart from the sternum or the elasticity of the rib cage could influence relative efficacy in individual cases, but studies on manual compression that have addressed similar issues make this hypothesis unlikely. The time spent in applying the devices by well trained operators should not be very different, nor should be the effect on ease of movement of patients vary appreciably. Primary percutaneous coronary angioplasty can be performed on patients maintained on both devices, though some would argue that LUCAS fitted with a radiolucent base is preferable in this situation. Certainly, there are good reasons for hoping that more than one device remain as viable options.
Are ACDs easy to actually employ?
What are the ‘hands-on’ issues that you are aware of in clinical practice and what possible improvements might help from a paramedic's perspective?
Joanna Hernandez replies:
The design presents some issues, in particular the size and shape of the back-plate. The LUCAS 2 device does tend to slide and move out of place when on uneven ground or on different types of outside terrain. The addition of some sort of shock absorbing material placed along the rear of the back-plate would enable a better grip to the ground surface and reduce some movement. Another potential recommendation would be to have an extendable back-plate so we could measure the size/width of the patient to the plate (almost like the settings on a cervical neck collar, but for example - small, medium and large adult) this may help to ensure the device fits tightly around the patient. This would also minimise the risk of it moving out from the patient's axilla even when the arms are placed in the side straps, as I've experienced this happen too.
One other issue that I have noticed is that of battery power—we can't always charge the ACD if we have a run of shifts with 24/7 critical care paramedic cover, especially if we are busy and not back on base much. As we are currently working on rapid response vehicles it is not very easy to charge the device in the car when we are out and about on the road. I've had to resort to using the charging unit connected to the plug socket inside the ambulance when I've used up both batteries, but have to be cautious when shocking the patient with it connected to the mains! So I tend to detach the charging lead prior to shocking then reattach with commencement of CPR. I feel battery life could be improved, as we never seem to have both batteries at 100% prior to deployment.
In terms of possible improvements, I wonder whether it could be adapted further to enable compatibility with some sort of ventilating apparatus? I find it quite helpful to be able to tailor my ventilation strategies to the patient's ETCo2 (shown on the ‘EMMA’ device) with our ventilator during the resuscitation effort to maintain adequate readings, ventilation rate and tidal volume, which you cannot achieve as well with a bag valve mask device when the ACD is on the patient's chest. Many people have commented on how much better they feel the LUCAS 2 is compared to its predecessor in terms of O2 consumption. With LUCAS 1, oxygen use was so dramatic that they would often run out during the resuscitation effort. On the whole, I've seen the LUCAS 2 work extremely well in providing both cerebral and cardiac perfusion.
There have been some recent concerns raised around the inconsistencies of the paramedic resuscitation curriculum (Lyon and Sinclair, 2012). Do you see a place for ACD education routinely? How would this be best managed?
Andy Bishop replies:
With the concerns raised I think it is reasonable to question the current level of education and training provided, and also what impact this may have on patient outcome. Given the importance of correct depth, rate and technique of chest compressions, it has been regularly argued that these vary considerably throughout the out-of-hospital arena and that monitoring of these standards is equally as variable.
In order to reduce these variables, the following could be considered:
ACDs are not a recommendation per se in the ERC (2010) guidelines. should mechanical devices be used as a routine in the management of cardiac arrest?
Douglas Chamberlain replies:
The finding in recent trials of equivalence or near equivalence compared with standard CPR for both devices should be interpreted with some caveats. Clinical trials should be reliable under the conditions of the trials but do not necessarily relate accurately to everyday events. The training that takes place for clinical trials may not be replicated for all paramedics who might use the devices for the relatively few cardiac arrests that each individual deals with each year. Of at least equal importance, inevitably some compression time is lost in fitting devices. Added to this, manual compressions of good quality need not be markedly inferior to mechanical compressions. But the devices can be invaluable in special situations. In particular, when patients do have to be transported before ROSC has been achieved, and in the case of a single professional rescuer who cannot give an adequate number of compressions and attend to all other duties that come with the management of cardiac arrest.
Andy Bishop replies:
Higher education institutions (HEIs) providing paramedic education are recognising the importance of a clinical leadership role within an out-of-hospital resuscitation incident and how vital this role is to ensure quality control and audit of skills such as chest compressions. Utilising the ACDs within this process could provide another important option in order to give the patient the best possible outcome. However, ACDs should be utilised based on the decision of the lead clinician at a resuscitation attempt and not seen as the only method for all out-of-hospital cardiac arrests.
Are there patient groups that are less appropriate to use the ACD with, or where manual compressions are going to be the better option? There are some instances that are cited as contraindications (Adams et al, 2013), e.g. pregnancy. Are there times when you would not consider an ACD and why?
Joanna Hernandez replies:
I haven't used the device on any females yet so I can't comment on how well it fits to the chest (especially if they have large breasts); however, I could see this as a potential limitation to its usage. There have been a couple of occasions where I've been unable to deploy it on the larger/obese patient as they have simply been too big to fit inside the device, especially those with barrel type chests/very large abdomens. I do find that on frail elderly patients the device does tend to cause a lot of damage and trauma to the chest wall, so much so that it breaks away the skin and causes a burn-like effect across the compression site. I did have to stop the ACD once as the pressure on this elderly man's chest was so great that it had caused significant internal injuries, the chest became concaved, and as he was a warfarinised patient, blood kept collecting inside the oral cavity which needed constant suctioning—this could have compromised the airway had he not been intubated.
There are some reports of complications and trauma incurred with ACD usage (Truhlar et al, 2010; 2012), although others dispute any distinct associated dangers (Smekal et al, 2009). Are there any disadvantages in using mechanical devices?
Douglas Chamberlain replies:
All CPR that meets requirements for adequate depth and is prolonged will cause some musculoskeletal damage in adults, particularly in those who are older, whose chest walls have less natural flexibility. Damage to costo-chondral junctions are near-inevitable, whilst rib and even sternal fractures are relatively common. Most would accept, however, that successful recovery with skeletal damage is preferable to death with the chest intact! Mechanical devices may cause more injury than manual compression (that may sometimes include organ damage) but the balance of net benefit over harm is likely to be positive. The risks of trauma from mechanical devices should be considered acceptable and does not rank as a disadvantage great enough to preclude use when indicated. One should emphasise, however, that inexpert application can cause unnecessary harm with both devices, highlighting the need for adequate initial training and refresher courses for those who use them only infrequently.
Any last comments on this point of ‘skill fade’?
Andy Bishop replies:
Regular resuscitation refresher training and assessment has traditionally been part of annual ‘key skills’ CPD workshops provided by ambulance services. With the reduction of educational staff within most UK NHS ambulance Trusts and the transference of educational responsibility to HEIs, it would be reasonable for ambulance services to consider if the HEIs can play an ongoing regular CPD role within the resuscitation field to ensure paramedics maintain high-quality skills through robust ACD and manual CPR assessment.
Annual workshops could be provided by HEIs in partnership with the ambulance service. This would support quality and competence of ambulance resuscitation attempts. Perhaps the format could follow a formal assessment in order to achieve a yet-to-be-created OOH resuscitation qualification under the auspices of the ERC?
Closing comments
Paramedics will be aware that there are a number of factors that influence someone's chances of survival in out-of-hospital arrest; this discussion has just looked at one area in particular: the importance of high quality of chest compressions and the utility of automated, mechanical assistance with these. Even though the implementation of ACDs at out-of-hospital cardiac arrest has not been correlated with increased survival (Smekal et al, 2011; Axelsson et al, 2013), the technology does seem to have some decided advantages for small teams or situations where transport is absolutely indicated. What has been demonstrated, with robust methodology, is that the device—in this case the ‘Autopulse’—can deliver compression's that are at least as good as high quality chest compressions (Lerner et al, 2011) and the same machine has shown a statistically significant improvement in survival (to hospital discharge) when the duration of the cardiopulmonary resuscitation was longer; this is witnessed in shockable OOH cardiac arrests in adults. What has not been established so far through large, multi-centre randomised clinical trial is an advantage in outcome (at four hours) of resuscitation employing an ACD compared with manual technique (Rubertsson et al, 2013). With this in mind, although deliberate routine education and training in the use of ACD devices appears obvious—and with some ongoing design modification possibly providing improvements in ‘usability’ for clinicians—the need for high quality, minimally interrupted manual chest compressions remains absolutely at the fore of cardiopulmonary resuscitation practice.