Sneak Preview: Physio Control Lifepak CR2

Today seen at the Emergency Services Show in Birmingham and from tomorrow on show at the ERC conference in Reykjavik; the new Physio Control Lifepak CR2 AED. The latest addition to Physio Controls impressive line of AEDs. Physio Control is awaiting CE approval, then the big distribution of this public defibrillator, making it available to a larger audience.

Appearance
We watched the demonstration of the CR2 and can inform you that the AED is practically the same as it’s predecessor, the main change being the colour. It is compact, with a white plastic lid and a black carry-handle. The status indicator displays a bright green flashing light, visible at the front of the AED. The device starts directly on opening and the electrodes are released by pulling on the clearly visible red handle. The shock electrodes are firmly attached to the AED by a tape. On opening the AED, you see four buttons: a language selection button, the on/off button, a child resuscitation button and finally, a shock button.

Currently only available as a semi-automatic, there will be a fully-automatic available. The price of the CR2 is not yet known, but is expected to be slightly above its predecessor the CRplus.

The Lifepak CR2 comes with an 8 year warranty. The battery and shock electrodes have a 4 year shelf-life before they require replacing. The water and dust resistance is set at IP55 which means the AED can compete with the best. Voice prompts from the Lifepak CR2 are quite extensive compared to other AEDs: it vocally announces the depth of chest compression as an aid to the rescuer. The shock protocol is the same as the other Lifepak AEDs, up to a maximum of 360 Joules.

App
Physio Control has developed an app simultaneously with the release of the Lifepak CR2, aimed at helping to manage AEDs. This app, which can be used in a range of browsers, allows an organization, different AEDs can monitor easily. The CR2 Lifepak AEDs can be connected to the database via Wi-Fi or mobile data (optional), whereby an alert can be sent when an AED is removed, opened or when an audit is needed.

Biggest Basic Life Support change in ERC guidelines 2015: the role of the emergency response communication centre

 

Not much has changed for Basic Life support in the new ERC 2015 guidelines. But small changes can make a big difference for a person’s life. So today at the ERC congress in Prague, one of the main subjects was about the role of the Emergency Response communication Centre.

A fast response and early CPR increase patients survival chances and therefor the bystander CPR has a huge lifesaving potential. In Europe, there are major differences in the way people act when they find a person lying on the ground and presumably dead. Not everyone is used to consider the possibility the victim might survive when CPR is started fast.

It all starts with recognising abnormal breathing. Any person that is unconscious and not breathing normally, is in direct need of CPR. As soon as the abnormal breathing is diagnosed, emergency services should be called to make sure professional help is on its way.  A lay person should get it’s instructions from the emergency dispatcher. How to get the bystander to perform good CPR?

 

New 2015 CPR guidelines, what are matching BLS products?

With the changes of the CPR guidelines that have been published in October, the European Resuscitation Council emphasises the importance of feedback during training. Quality improvements in Basic Life Support training can be accomplished by training with an advanced manikin with feedback. In real life situations, an AED with extensive guidance and feedback is recommended.

What products meet up to these recommendations?

For the manikins, the more feedback the better. Good measurement and feedback will benefit the fine-tuning of the students skills. Currently, one of the best adult manikins in terms of feedback possibilities is the Laerdal Resusci Anne QCPR (combined with a Skillguide or even better with the Simpad Skillreporter). If you have a small budget but still want the look and feel of an advanced manikin, the Ambu Man I or W can be a smart choices. Of all the basic manikins under €250,-, the Prestan manikin scores best on feedback. Ambu Uniman Sam and Laerdal Little Anne have basic measurement. For paediatric CPR instructions with feedback you need the Laerdal Resusci Baby QCPR or the basic Prestan Baby.

There are a number of AED’s that have feedback build in. The Heartsine Samaritan PAD 500P, Cardiac Science Powerheart G5 and Zoll AED Plus measure the depth of the chest compressions and suggest improvements during the CPR process. Adapted audio and visual instructions help improve the patients survival chances by instructions to improve chest compressions. If you want extended CPR guidance, but you are not interested in feedback, then the Philips public AED’s are among the best. These AED’s have an information button that can be pressed if the rescuer needs more instructions. If he does not need it, the Philips Heartstart HS-1 and FRx AEDs are quiet and leave you concentrated on lifesaving.

Would you like more information or would you like to purchase? Please visit www.medisol.eu for the web-shops overview and contact information of your local product specialist.

 

The differences between the various Zoll electrode pads

These pads are suitable for the Zoll AED Plus and the Zoll AED Pro. Which ones should you choose?  In the overview below we have set out the differences that may help to make your choice easier.

Click here to view the Zoll electrode pads in our web shop.
 As you can see there are 4 types. All of these electrode pads can be used with the Zoll AED Plus and the Zoll AED Pro and are interchangeable with the professional monitors/ defibrillators from Zoll that are used by ambulance services. All these sets can be used once only. After they have been removed from their sealed package they must be used straightaway.  Electrode pads have a limited shelf life because the conductivity of the adhesive gel that will decrease with time.

Zoll CPR/D Padz (are.8900-0800-01)
These pads are the preferred pads for the Zoll AEDs as they have been developed for maximum  convenience. Each pad has been made from one piece, which makes accurate positioning easier. These pads have a sensor that measure the depth of the chest compressions. The AED responds to these measurements by giving extra instructions such as ‘press harder’. Better chest compressions will help to increase the chances of survival. The CPR/D pads have a 5 years shelf life. This explains the higher purchase price compared to the other Zoll electrode pads. These electrode pads are  intended for adults.

Zoll CPR Stat Padz (art.8900-0400)
The CPR Stat Padz are not made out of one piece like the CPR/D pads, but are provided with a sensor. These pads are made for the aid worker who welcomes extra instructions but not one-piece pads. These electrodes may also prove advantageous when the AED is used regularly. Their price is lower, all functionality is preserved and their shorter shelf life (about 2 years) is less important. These sets are intended for adult uses.

Stat Padz II (art. 8900-0801-01 Zoll)
Stat Padz are sold widely to people who have no interest in the CPR-feedback of the Zoll AEDs; no sensor is attached to the pads and there is no feedback. This product is made for the very CPR experienced aid worker who would not benefit much from CPR feedback. The electrodes are only connected to each other through a cable and are therefore not made out of one piece. These are the most favourably priced electrode pads and have a shelf life of approximately two years.

Zoll Pedi Padz (art. 8900-0810-01)
The Pedi Padz are intended for children up to 8 years of age or about 25 kg of body weight.

These electrodes guide the energy level of the shock downwards in order to provide optimum therapeutic benefit to smaller bodies.  It is good practice to keep paediatric pads in the vicinity of the AED when it is kept  in a place where many children are present.

AED Maintenance Contract

Available very soon at Medisol AEDexpert.co.uk,  the AED Maintenance Contract

The Medisol Service Centre can then offer you a maintenance service contract for your AED’s.
This service will be available in your area from autumn 2015.

The advantages are:

  • 24/7 phone access for reporting a malfunction
  • Trade Service at fault
  • A replacement AED will be available before 12 a.m the next day
  • Timely replacement of electrode pads and batteries
  • Annual inspection of your AED on location
  • Certainty: you will always have an operating AED
  • Inspection according to the AED label guidelines

If you are interested in this service? Please register by e-mail to be the first to know when more information is available.

Children and circulatory arrest

When a small child (<25 kg) has a circulatory arrest, this usually has a different starting cause than a fibrillating heart. Examples of this are:
-suffocation
-drowning

The right treatment in this case is:
-dial 999 or 112
-start CPR

Because it is not always clear what caused the circulatory arrest the AED unit will always have to be brought.
If a victim weighs less than 25 kg the use of child pads is recommended but not required.

Reasons for using child pads are:
-the AED uses a special child-database for the heart analysis (that is because the regular heart rhythm of a small child is faster or even much faster than for an adult);
-the surge of the AED will revert from 150 Joule to 50 to 80 Joule.

The adjustment of the database, protocol and Joules varies per brand. This document is based on the Philips AED’s

Reasons not to use child pads are:
-having to change electrodes in the middle of a panic situation, which can lead to delays.
-A child key or switch button can be a solution;
-the AED can also be used with adults’ electrodes for use on children who weigh less than 25kg.
-The Dutch Resuscitation Council writes in the currently applicable guidelines: Standard AEDs may also be used for defibrillation of infants and children if there is no custom AED available for them.
-with children under 25kg circulatory arrest in which fibrillation is the cause is less than 5x a year.

Summarizing:
It is better for a child to use child pads, but in emergencies the standard AED should be used.

Remark: for children under 25kg the pads will have to be patched in a different way. See the picture below (one electrode pad on the rear between the shoulder blades and one electrode pad on the breastbone between the nipples: The hands should in this case be placed on the electrode pads during resuscitation).

Quality of BLS when using different public AED’s

Earlier this week a very interesting science article was published about the effect of AED voice prompts in relation to the quality of BLS (in particular the duration of the interruptions during the chest compressions). Given the importance of this article we have decided to take this publication entirety over. This is a study of a German team from the University Hospital in Dresden and published on June 21, 2015 in the Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine. Copy of this article is authorized provided the source is acknowledged.


 

Timeisessence

Quality of basic life support when using different commercially available public access defibrillators

Michael P. Müller, Cynthia Poenicke, Maxi Kurth, Torsten Richter, Thea Koch, Carolin Eisold, Adrian Pfältzer and Axel R. Heller


Abstract

Background

Basic life support (BLS) guidelines focus on chest compressions with a minimal no-flow fraction (NFF), early defibrillation, and a short perishock pause. By using an automated external defibrillator (AED) lay persons are guided through the process of attaching electrodes and initiating defibrillation. It is unclear, however, to what extent the voice instructions given by the AED might influence the quality of initial resuscitation.

Methods

Using a patient simulator, 8 different commercially available AEDs were evaluated within two different BLS scenarios (ventricular fibrillation vs. asystole). A BLS certified instructor acted according to the current European Resuscitation Council 2010 Guidelines and followed all of the AED voice prompts. In a second set of scenarios, the rescuer anticipated the appropriate actions and started already before the AED stopped speaking. A BLS scenario without AED served as the control. All scenarios were run three times.

Results

The time until the first chest compression was 25 ± 2 seconds without the AED and ranged from 50 ± 3 to 148 ± 13 seconds with the AED depending on the model used. The NFF was .26 ± .01 without the AED and between .37 ± .01 and .72 ± .01 when an AED was used. The perishock pause ranged from 12 ± 0 to 46 ± 0 seconds. The optimized sequence of actions reduced the NFF, which ranged now from .32 ± .01 to .41 ± .01, and the perishock pause ranging from 1 ± 1 to 19 ± 1 seconds.

Conclusions

Voice prompts given by commercially available AED merely meet the requirements of current evidence in basic life support. Furthermore, there is a significant difference between devices with regard to time until the first chest compression, perishock pause, no-flow fraction and other objective measures of the quality of BLS. However, the BLS quality may be improved with optimized handling of the AED. Thus, rescuers should be trained on the respective AED devices, and manufacturers should expend more effort in improving user guidance to shorten the NFF and perishock pause.


Introduction

The survival rate after out-of-hospital cardiac arrest (OHCA) is below 10 %, despite considerable efforts on the part of emergency medical services and hospitals to optimize treatment [1]. The key problem is that in cases where no lay rescuers initiate basic life support measures, blood flow to the brain is restored only when professional rescuers start chest compressions, which is often too late for recovery without serious sequelae. The current American Heart Association and European Resuscitation Council guidelines for cardiopulmonary resuscitation (CPR) outline immediate recognition, early CPR, and rapid defibrillation as the key elements of the chain of survival [2],[3]. Furthermore, the 2010 update of the CPR guidelines was designed to ensure high quality chest compressions and minimize interruptions to maximize organ perfusion.

Automated external defibrillators (AED) reliably recognize shockable cardiac rhythms and allow defibrillation to be performed by non-physicians. Furthermore, the time from collapse to defibrillation determines survival in patients with OHCA; each delay of one minute increases mortality by 10 % [4]. Thus, efforts have been increasingly undertaken in the past few years to make AEDs available to the public, especially in high-traffic public areas. By decreasing the time to the first defibrillation, the survival rate after OHCA has increased up to 74 % [5]. Many different AEDs are commercially available, and modern devices defibrillate with biphasic waveforms, resulting in high conversion rates. AEDs seem to be perfect “resuscitation devices” for lay rescuers, as they not only analyse the rhythm and shock the patient if indicated, but they also provide essential instructions regarding the BLS algorithm. The AED provides audible instructions to activate the emergency medical system (EMS), check for vital signs, and initiate chest compressions. However, as early as 10 years ago, Fleischhackl studied how lay people operate an AED and found alarming results; the time to the first shock and the proportion of study volunteers who started chest compressions after being prompted by the AED varied widely [6].

To our knowledge, no previous study has investigated interruptions of chest compressions during BLS when an AED is used. The objective of this study was to evaluate the quality of BLS when an AED is used with a special focus on the no-flow fraction and the perishock pause.

Methods

This study complies with the Declaration of Helsinki, and the locally appointed ethics committee approved the study protocol (EK 127042012). Two standard test scenarios were scripted using a Code Blue III Advanced Life Support manikin (Gaumard Scientific, Miami, FL/ USA). The manikin has conductive skin regions allowing defibrillation with real AEDs through the standard self-adhesive pads. The simulator can be connected to a laptop computer, and the Gaumard software (Gaumard UI-1.40.18.0) records chest compressions, ventilations, and defibrillation.

Eight AEDs were available for the study: Heartsave PAD (Metrax, Rottweil, Germany), Philips HS1 (Philips Medical Systems, Bothell, WA, USA), Lifeline VIEW AED (Defibtech, Guilford, CT, USA), Lifepak CR Plus (Medtronic Physio-Control, Redmond, WA, USA), PowerHeart G5 (Cardiac Science, Bothell, WA, USA), Fred Easy Life (Schiller AG, Baar, Switzerland), AED Plus (Zoll Medical Corporation, Chelmsford, MA, USA), and Cardiolife AED 2100 (Nihon Kohden Corporation, Tokio, Japan). All AEDs were provided by the manufacturers, except for the AED Plus. The language of all AEDs were set to German. The manufacturers were asked to provide a device that is used as a public access defibrillator. Each of the AEDs was evaluated in pre-scripted basic life support scenarios with an adult patient in persistent ventricular fibrillation (VF, scenario 1) or asystole (scenario 2). Each AED was tested three times in both scenarios. The scenario duration was 5 minutes. One BLS instructor (MK) performed single-rescuer BLS using an AED and following the voice prompts. BLS was performed according to the 2010 ERC guidelines, with a ratio of 30 chest compressions to 2 ventilations. The respective AED was switched on immediately at the start of each scenario. The BLS instructor followed all voice prompts of the AED exactly as provided. The rescuer listened to each voice prompt and started the appropriate action immediately after the AED finished speaking.

All AEDs were tested again in a second set of scenarios (a total of three times each in scenarios 1 and 2). However, the BLS caregiver followed the optimal sequence of actions, with minimal interruptions in chest compressions. This was done by starting the appropriate action as early as possible during the AED voice prompt. Some actions can be initiated before the AED has started that particular instruction; for example, chest compressions were resumed immediately after each shock.

A third scenario, 5 minutes in duration, was run without the use of an AED to calculate the difference in the no-flow fraction between BLS with and without the use of an AED. This scenario was also repeated three times.

During all scenarios with the use of an AED, the following values and time intervals were measured:

  • Time until first chest compression
  • Time until the first rhythm analysis was completed
  • Duration of rhythm analysis
  • Time until first shock (in scenarios with ventricular fibrillation)
  • Time between first shock and the beginning of the second rhythm analysis (in scenarios with ventricular fibrillation) or time between completion of the first rhythm analysis and the beginning of the second rhythm analysis (in scenarios with asystole)
  • Perishock pause: Time from last chest compression (CC) before a shock until the first chest compression after the respective shock (in scenarios with ventricular fibrillation)
  • No-flow fraction (NFF): Fraction expressed as a quotient of the no-flow time and the total time without spontaneous circulation.

The mean and standard deviation were calculated for all parameters for each AED.

Data analysis and statistics

All data were analysed using IBM SPSS software (Version 21.0.0.0, Armonk, NY). After ensuring homogeneity of variances by the Levene test, univariate ANOVA was used for repeated between-AED model analyses and was followed by Sidak post-hoc testing and multiple comparison alpha adjustment.

Within each AED model, a paired t-test was used to compare the effects of performing the optimal sequence of actions compared to standard AED voice-prompt-guided procedures.

Due to the strongly statistically significant difference between the AED models as shown in Tables 1, Table 2, Table, 3 and 4, only a lack of significance is indicated. If not otherwise indicated, the between AED-model comparison of the respective parameters is statistically significant at a p-value of <0.01.

Table 1. BLS with the use of an AED in scenarios of persistent ventricular fibrillation. The duration of the scenario was 300 seconds

tabel1

Table 2. BLS with the use of an AED in scenarios of persistent asystole

tabel2

Table 3. BLS with the use of an AED in scenarios of persistent ventricular fibrillation: optimized sequence of actions. The duration of the scenario was 300 seconds

tabel3

Table 4. BLS with the use of an AED in scenarios with persistent asystole: optimized sequence of actions

tabel4

Results

Data for BLS with an AED when the AED voice prompts were strictly followed are shown in Table 1 for VF and in Table 2 for asystole. Table 3 (VF) and Table 4 (asystole) present the data from the AED scenarios with an optimized sequence of actions during BLS. An English translation of the voice prompts in a scenario with shockable rhythm is provided for all AEDs that were evaluated (Additional file 1).

In the scenarios with persistent ventricular fibrillation and without an AED, the rescuer started chest compressions after 25 ± 2 seconds. When using an AED and following the voice prompts, the mean time until the first chest compression ranged from 50 ± 3 seconds to 148 ± 13 seconds in the first set of scenarios (the action was started after the AED finished speaking). In the second set (the optimized sequence of actions), the interval to the start of chest compressions ranged from 16 ± 2 to 41 ± 1 seconds.

The no-flow fraction during BLS without the use of an AED was 0.26 ± 0.01. However, the use of an AED increased the NFF in all scenarios: in the first set of scenarios, the NFF ranged between 0.37 ± 0.01 and 0.72 ± 0.01 (VF) and between 0.40 ± 0.01 and 0.72 ± 0 (asystole). In the second set of scenarios (the optimized sequence), the variability in NFF decreased to 0.32 ± 0.01 – 0.37 ± 0.02 for VF and 0.33 ± 0.01 – 0.41 ± 0.01 for asystole, respectively. The differences between the devices were statistically significant, except for three models of VF and one model of asystole. However, the NFF still was significantly higher with all devices compared to BLS without the use of an AED (p < 0.01).

In the first set of scenarios, the shortest value for the perishock pause was 12 ± 0 seconds, whereas the longest pause was 46 ± 0 seconds. In the scenarios with an optimized sequence of actions, the perishock pause was shorter, ranging from 1 ± 1 to 19 ± 1.

Discussion

This is the first study to investigate the no-flow fraction, perishock pause, and other objective quality parameters during BLS using eight different available public access defibrillators in a simulator setting.

As expected, our study found higher NFF values in BLS scenarios that used an AED compared to those that did not. Furthermore, we found extremely high NFF values in these scenarios with a high variability between the different models. In all cases, the perishock pause was always much longer than advised by the current resuscitation guidelines. However, when the rescuer optimized the sequence of actions and acted immediately before or after the voice prompt started (Tables 2 and 4), the NFF and the perishock pause both were significantly reduced, with minor variability.

The chest compression fraction has been identified as a cardiac resuscitation quality parameter that is associated with the survival rate [7],[8]. A small study from the PAD trial evaluated the quality of BLS and found very high values for NFF (0.52 to .83) when lay rescuers performed BLS and used an AED[9]. Two studies have shown that chest compressions during prehospital life support are interrupted in approximately half of the time [10],[11]. The current international resuscitation guidelines demand high quality chest compressions with minimal interruptions. Well trained teams can provide life support with NFFs as low as 0.24 [12]. In these cases, a defibrillator capable of manual defibrillation was used. However, an observational study showed that the NFF during in-hospital BLS with the use of an AED can be as low as 0.30 when nurses repetitively perform the BLS/ AED algorithm in a BLS training course [13].

The NFF during scenario 2 (asystole) was comparable to that of scenario 1 and was significantly higher than the value for BLS without an AED for all AEDs. Recent studies have found that only between 24 and 40 % of patients with OHCA are in a shockable rhythm when the ambulance arrives [14]. At the time of collapse, the proportion of patients who are in a shockable rhythm is higher, but there is still a considerable number of patients who are in a non-shockable rhythm. For those patients, the use of an AED resulting in a high NFF is harmful and may increase mortality.

The NFF was lower for six devices (VF) and 5 devices (asystole) during the scenarios with an optimized sequence of actions. The NFF was similar in all devices and was below .40, except for one AED in asystole. This set of scenarios can be compared with trained lay rescuers or healthcare professionals after practice with a specific AED. The first set of scenarios involves untrained lay rescuers using a public access defibrillator while strictly adhering to the guiding voice prompts. It is concerning that the use of commonly available AEDs, which are designed to be used by lay rescuers, might lead to poor quality life support, with chest compressions being delivered less than 30 % of the time. The wide difference between the standard use and the optimized sequence of actions implies that the human-machine interface of the devices is a major problem; manufacturers should expend considerably more effort on the development of optimal user guidance to ensure the best possible performance, even when used by lay rescuers who have never before observed a patient in cardiac arrest and who perhaps have never received BLS training.

Stopwastingtime

Perishock pause

Survival to hospital discharge is substantially more likely when the first documented rhythm is shockable rather than nonshockable [15]. When a defibrillator is used, the perishock pause has been identified as an independent predictor of survival [16]. A substantial delay in providing chest compressions has been observed in the post-shock period with AED-equipped first responders [17]. As Cheskes et al. reported, a pre-shock pause of ≥ 20 seconds and a perishock pause of ≥ 40 seconds are predictors of worse survival after shockable cardiac arrest. Based on a log-linear model, any five seconds increase in the perishock pause interval decreases the rate of patient survival to hospital discharge by 14 % [16].

Therefore, the international guidelines for resuscitation advise a perishock pause of less than 5 seconds. This recommendation was not fulfilled in any of the AEDs tested in the first set of scenarios with strict voice prompt adherence. We noted that some AEDs do not permit chest compressions during the charging period, resulting in an almost fourfold variation in the perishock pause between the different devices. This variation in duration may be responsible for the variable success in patient resuscitation. In 2004, Snyder et al. alluded to the problem of the AED-determined variation in hands-off times[18]. However, the manufacturers may have implemented an algorithm, which does not prompt the rescuer to provide chest compressions for some seconds during charge and then take hands off for the shock as this may confuse lay persons. We need further studies to find out whether real lay rescuers are able to follow such an algorithm with minimised perishock pause.

The perishock pause was reduced in nearly all of the tested AEDs when the optimized sequence of actions (in the second set of scenarios) was used. Two devices met the demands of the current guidelines, implying that there is significant potential for improving user guidance. The necessary changes are small and include optimization of the device algorithms and voice prompts. Determining the best practices for AED voice prompting will be the subject of a follow-up analysis of the present dataset.

Time until first chest compression

A lone lay rescuer following the AHA guidelines for BLS would call an ambulance, fetch an AED (if available), and return to the patient to start life support [2]. However, when switching on the AED and following the voice prompts, the beginning of chest compressions is delayed for up to nearly 2.5 minutes. This stands in sharp contrast to what is taught in courses on cardiac resuscitation around the world: the check – call – compress paradigm, in which chest compressions are started as early as possible, and any unnecessary interruptions are avoided.

A retrospective analysis of OHCA cases found no benefit of bystander CPR for patients receiving the first shock between 1 and 5 minutes after collapse, whereas survival was much higher for patients receiving bystander CPR when the first shock was applied after more than 11 minutes [19]. However, even for the patients receiving the first shock within 5 minutes, this study does not answer the question whether shock first (and delayed start of chest compressions) or CPR first (and later application of the shock) is superior with regard to the survival rate. However, modern AED devices should guide the lay rescuer to soonest possible defibrillation, while assuring a short time until the first chest compression.

Duration of rhythm analysis

The duration of rhythm analysis depends solely on the technical specifications of the respective device. This value varied by about 100 % between the devices. However, the absolute difference between the fastest and slowest analysis duration was only 8 seconds. One potential future improvement is hands-on rhythm analysis during chest compressions. Making a serious effort to develop optimized devices may lead to shorter time intervals. However, a much larger effect on shortening the NFF among layperson rescuers could be achieved by inventing devices with improved usability and voice prompts.

Wide variation of CPR quality between different AED models

When a lay rescuer provides BLS and uses an AED model with which he or she is not familiar, the CPR quality depends critically on the AED device. We found extensive variations in important parameters such as the NFF and the perishock pause. Most clinical studies investigating the effects of the use of AED were not stratified by the AED model used. Future studies, especially large resuscitation registries, should always consider the defibrillator model. Even the firmware version might provide important additional information, as different versions may differ in terms of user guidance and thus lead to variations in the quality of BLS.

In this study, a trained person used the AEDs. However, lay rescuers use these machines in real cardiac arrest situations. As they are under high stress and may be afraid of using an AED, the voice prompts should be clear and precise. Some models provide more detailed voice prompts than others (see Additional file 1). We do not know whether more details result in better performance and less mistakes when the AED is used by untrained real lay rescuers and whether this may compensate the longer and more frequent interruptions. The intention of very precise instructions may be to assure a shock when used by a heterogeneous group of lay rescuers. However, if a lone rescuer places an emergency call and fetches an AED before returning to the patient, 2 minutes or more may already have been expired. At this time, soonest beginning of chest compressions is important and this should be taken into account when developing AEDs and when elaborating user guidance. Further research should be done to study the quality of BLS when lay rescuers use AEDs.

Limitations

This study was performed in a simulator centre, and a BLS instructor evaluated the devices. The quality of BLS in real cases may vary from that in this study.

With some AEDs, lay rescuers may not understand some voice prompts or they could experience usability problems that could not been found in the present study but may result in even worse BLS performance.

Conclusions

Our study presents concerning results regarding the quality of BLS when using an AED and following all voice prompts. We found a broad variation in the parameters, which were evaluated in the study, including the time until the first chest compression, the no-flow fraction, and the perishock pause. The manufacturers should take these results into account when developing the next generation of AEDs to be used by layperson rescuers: The protocol of the respective device should meet the best available standard as a high quality of BLS is of utmost importance for optimal survival rates.

Competing interest

MPM has received a speaker honorarium from Philips Healthcare. All authors declare to have received non-financial support from Metrax, Rottweil, Germany, non-financial support from Philips Medical Systems, Bothell, WA, USA, non-financial support from Defibtech, Guilford, CT, USA, non-financial support from Medtronic Physio-Control, Redmond, WA, USA, non-financial support from Cardiac Science, Bothell, WA, USA, non-financial support from Schiller AG, Baar, Switzerland, non-financial support from Nihon Kohden Corporation, Tokio, Japan, non-financial support from Zoll Medical Corporation, Chelmsford, MA, USA, during the conduct of the study.

Authors’ contributions

All authors declare to have no other relationships or activities that could appear to have influenced the submitted work.

Funding

The following companies provided AED models and self-adhesive pads for the study: Metrax, Rottweil, Germany; Philips Medical Systems, Bothell, WA, USA; Defibtech, Guilford, CT, USA; Medtronic Physio-Control, Redmond, WA, USA; Cardiac Science, Bothell, WA, USA; Schiller AG, Baar, Switzerland; Nihon Kohden Corporation, Tokio, Japan. Zoll Medical Corporation, Chelmsford, MA, USA, did not provide an AED, but provided self-adhesive pads. The funders of the study had no other role in the study design, data collection, data analysis, data interpretation, or writing of the report.

References

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Manufacturer Primedic increased warranty up to 6 years.

The manufacturer of  the Primedic AED defibrillators has increased the warranty period for most models up to 6 years. This warranty period is valid for the AEDs with date of delivery from 1 September 2014.  This is valid for the models Primedic Heartsave PAD, Primedic Heartsave AED, Primedic Heartsave AED-M and Primedic Heartsave AS.

The model Primedic HeartSave ONE has a warranty period of  3 years.

All of these models had a warranty period of 2 years.

No excuse for AED behind lock and key

Medisol from Middelburg the Netherlands with web shops throughout Europe and market leader in the Netherlands for the Automated External Defibrillators  AED  does not sell AED cabinets anymore with a keypad or pin lock. The reason for this is that an AED should be accessible for everyone. Medisol has already taken initiatives in the past to discourage the use of locks on AED cabinets.

“Since the start of selling AEDs we find it difficult to keep an important life saving device behind lock and key”, according to Medisol. During our work for the ambulance service we have experienced that AED heart defibrillators were of no use, because nobody knew the pin lock or had the key for the AED cabinet. We now have made a statement and have stopped the sales of AED cabinets with locks or pin lock systems. The AED does not belong  “behind bars”. For crying out loud  “have you ever seen a fire-extinguisher that you needed a key for? “

Medisol asks that the Netherlands  take a special position within Europe. In other countries AED cabinets with a pin lock are nowadays a phenomenon. Abroad there have been several initiatives to stimulate the public character of AEDs. The English Resuscitation Council and the British Heart Foundation have mentioned to give no subsidy to AED-projects where AEDs are placed in a locked cabinet.

https://www.resus.org.uk/pages/aed.pdf/ section guidelines 2010: the use of automated external defibrillators/ page 34

Medisol has been longer active with the subject better achievability  of  AED heart defibrillators. In 2009 Medisol associated with a few large manufacturers and  AED suppliers and launched the website “Stolen AED”. On the website achievability of  the AED is stimulated by giving information. The risk of someone getting an heart attack is much bigger than an AED being stolen out of a cabinet . But  there will always be customers who won’t give it enough thought and will choose an AED wall cabinet with a (pin-) lock.

We want to have a clear conscience on this delicate matter. Someone could die because of an AED placed in a locked cabinet. The past years we have advised our customers not to choose for a locked system, but against all advice in they have continued to do so. “Since 2013 we offer only free-access cabinets”, according to Medisol.

What is the reason AED electrode pads have a limited shelf life?

You must have noticed when you have an AED that the electrode pads have a limited shelf life. What is the reason for this?

The function of AED electrode pads

The pads have two main functions.  Attached to the AED the pads measure the heart rhythm to judge if a life-saving shock is required.  If the AED recommends a shock must be given then it will give a therapeutic shock using the same electrode pads. For use of these main functions  firm adhesion to the  skin is of great importance.

The electrode pads use an adhesive gel that conducts

For  purpose of adhesion to the skin electrode pads are equipped with a gel that not only has adhesive properties but also conducts the electric current. After a while the gel on the pads may dry out in the packaging, causing the chemical composition of the gel to change.  This will  result in  lower conduction of the electric current.  The AED may have problems with the analysis if the quality of the conducting signal reduces.  Also the electrode pads will be less adhesive. This can be a problem when chest compressions have to be applied. They may shake loose from the skin or become displaced. The AED will then be less able of providing a therapeutic shock, hence reducing its life-saving function.

The solution

Because of changes in the chemical composition of the pads the manufacturer can guarantee their quality only for a specific period of time after production. This is the reason that the pads are supplied with a “best before date”. The shelf life varies, depending on the brand and type and runs from 12 to 60 months. It is important that during the periodic inspection of the AED the electrode pads are also checked and, where necessary replaced.