A study comparing the usability of fully automatic versus semi-automatic defibrillation by untrained nursing students

Resuscitation 64 (2005) 41 47 A study comparing the usability of fully automatic versus semi-automatic defibrillation by untrained nursing students Koenraad G. Monsieurs a,, Catherine Vogels b, Leo L. Bossaert c, Philippe Meert d, Paul A. Calle a a Emergency Department, Ghent University Hospital, De Pintelaan 185, Ghent 9000, Belgium b Intensive Care Department, Cliniques Universitaires St. Luc, Avenue Hippocrate 10, Brussels 1200, Belgium c Intensive Care Department, University Hospital Antwerp, Wilrijkstraat 10, Edegem 2650, Belgium d Emergency Department, Cliniques Universitaires St. Luc, Avenue Hippocrate 10, Brussels 1200, Belgium Received 1 June 2004; received in revised form 2 July 2004; accepted 6 July 2004 Abstract Introduction: Current international guidelines prefer the use of semi-automatic external defibrillators (SAEDs) over fully automatic external defibrillators (FAEDs). However, there is a lack of evidence supporting this recommendation. We conducted a study of usability with nursing students comparing the FAED version against the SAED version of the Lifepak CR Plus AED (Medtronic, Redmond, USA). We hypothesized that FAED use would limit the number of operator-device interactions, thereby increasing compliance by the rescuer, safety and speed. Methods: Sixty-two untrained first year nursing students were randomized to use the FAED or the SAED in a simulated cardiac arrest scenario. During analysis and delivery of three shocks, the AED guided the user with six voice prompts per shock (18 voice prompts per student). Their performance with regard to efficacy and safety was assessed using video recording. Results: All rescuers except for two were able to attach electrodes and deliver a series of three shocks. During rhythm analysis by the device, FAED users made 30/372 (8%) errors against 62/360 (17%) errors for SAED users (P < 0.001). During shock delivery, FAED users made 0/186 errors against 12/180 (7%) for SAED users (P < 0.001). FAED use eliminated long time intervals between the first to the third shock (range 47 49 s for FAED versus 41 90 s for SAED). Conclusion: Despite a lack of BLS skills and AED training, the majority of students demonstrated safe and effective use of the AED. The use of the FAED version of the CR Plus resulted in increased compliance with the protocol and reduced variability in time to deliver three shocks. Further research is needed to confirm these findings in other groups of first responders. 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Automated external defibrillator (AED); Cardiac arrest; Defibrillation; Safety; Training; Usability 1. Introduction Previous studies have indicated that the use of an automated external defibrillator (AED) by untrained rescuers may be feasible, but safe operation has been one of the major con- A Spanish and Portuguese translated version of the Abstract and Keywords of this article appears at 10.1016/j.resuscitation.2004.07.003. Corresponding author. Tel.: +32 9 2402755; fax: +32 9 2403948 E-mail address: koen.monsieurs@ugent.be (K.G. Monsieurs). cerns [1 6]. Current international guidelines on the use of AEDs recommend the use of semi-automatic (SA) external defibrillators (SAEDs) reserving fully automatic (FA) external defibrillators (FAEDs) for special situations [7]. However, evidence to support this recommendation is lacking. We hypothesized that FAED use would limit the number of operator-device interactions, increasing compliance by the student nurses, safety and speed. Therefore, we compared the use by single untrained nursing students of an AED in FA versus SA mode. 0300-9572/$ see front matter 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.resuscitation.2004.07.003

42 K.G. Monsieurs et al. / Resuscitation 64 (2005) 41 47 Fig. 1. Flow chart of fully and semi-automatic modes of the Lifepak CR Plus (voice prompts are printed in italic). 2. Methods Sixty-two first year nursing students (Institut Supérieur d Enseignement Infirmier, Université Catholique de Louvain, Belgium) were randomized to use either the FAED version or the SAED version of the Lifepak CR Plus AED (both training AEDs, Medtronic, Redmond, USA) in a simulated cardiac arrest scenario with a fully dressed training manikin (Recording Resusci Anne, Laerdal, Norway), delivering a series of three consecutive shocks. We have used this particular device because it is the only latest generation AED currently available in both fully and semi-automatic mode. Apart from a small lid covering the shock button in FA mode, both types of AED are identical on the outside. The sounds during charging are also identical. During analysis and shock delivery, the AEDs only differ in a single voice prompt (see Fig. 1). The students were unprepared; they were expecting a scheduled lecture on first aid. A questionnaire was taken immediately before the test to assess demographics and previous basic life support (BLS)/AED training and experience. The performance of the students was recorded on video and their behaviour was scored afterwards by KM and CV using the Cardiff scoring system [8]. All participants gave prior written informed consent for their actions to be filmed. 2.1. Assessment of BLS skills To determine BLS skill level, all participants were first asked to help a victim who collapsed after having experienced chest pain. No further information was given to the rescuer, except the clinical condition of the manikin, which was communicated after each appropriate assessment by the rescuer. Ventilation and compression data were recorded on the manikin. All BLS actions were also recorded on video. After a maximum of 3 min, the rescue attempt was interrupted. 2.2. Definitions of BLS performance The Cardiff scoring criteria were used, but for some techniques this scoring system did not allow meaningful conclusions because of the poor performance of our untrained participants. We therefore modified the definitions for the following items: Call for an ambulance: the candidate mentions a call for an ambulance at any time during the resuscitation effort. Free airway: the airway is opened before assessment of breathing and before two initial rescue breaths. Effective rescue breathing: a minimum of six effective mouth-to-mouth ventilations per minute (tidal volume 800 1200 ml). Correct hand position: hand position on the lower half of the sternum Effective chest compression: depth between 4 and 5 cm at a rate between 80 and 120 per min. Correct ratio: at least two cycles showing two ventilation attempts and from 14 to 16 chest compressions.

K.G. Monsieurs et al. / Resuscitation 64 (2005) 41 47 43 2.3. Assessment of AED skills After the assessment of the BLS skills, the manikin was redressed and an AED was given without explaining its purpose, only that they should attempt to use the device as it could help the victim. The AED actions were recorded on video and interrupted after a maximum of 4 min. The AEDs were programmed to deliver a series of three consecutive shocks. During cardiac rhythm analysis and shock delivery, the AED guided the user with six voice prompts: 1. Do not touch patient 2. Evaluating heart rhythm 3. Stand by 4. Preparing to shock 5. a. SAED: everyone clear, press flashing button b. FAED: do not touch patient, delivering shock 6. Shock delivered Because each participant delivered three shocks, 18 voice prompts were given per rescuer, i.e. a total of 558 voice prompts for the FAED group (n = 31) and 540 for the SAED group (n = 30). Based on the voice prompts, each rescue attempt was subdivided into three sections covering six episodes. These episodes were used to tabulate incidents occurring during the rescue efforts. After the first voice prompt do not touch patient, rescuers are expected to stand clear until shock delivery. The first four voice prompts guide the rhythm analysis; touching the victim may negatively influence the accuracy of this process. The last two voice prompts relate to shock delivery; not respecting them exposes the rescuer to a safety hazard. To assess the behaviour of the participants after each voice prompt, an additional detailed scoring sheet was used. The language of the training AEDs was French. The French voice prompts are exact translations from English, except for an additional voice prompt continue care which was translated into maintenir surveillance (which means maintain surveillance ). This continue care prompt (preceded by a check breathing prompt) is given after the series of three shocks. The correct position of the electrodes on the chest of the manikin could be identified from pictorial information on the AED, on the package of the electrodes and on the electrodes themselves. After the participants had attached the electrodes to the chest, an instructor pressed a button on an infrared remote control to allow the AED to proceed. 2.4. Outcome measures Outcome measures were: performance of BLS techniques (before AED use), AED time intervals (receipt to switch on, switch on to electrode placement, electrode placement to first shock, first shock to third shock), position of electrodes on the chest, rescuer compliance after each voice prompt during the series of three shocks and BLS performance after delivery of three shocks. The position of the electrodes on the manikin was assessed by comparing the video images with the correct area as defined by the Cardiff scoring system [8]. 2.5. Statistics Continuous variables were assessed with the Mann Whitney U-test, discrete variables with the chi-square test and Fisher exact test where appropriate using Statistica for Windows (Statsoft). 3. Results 3.1. Characteristics of rescuers (Table 1) A limited number of participants reported that they had followed a BLS course previously. In addition, 13 subjects of each group had participated in a trial studying BLS from a CD-ROM, 7 FAED users and five SAED users had been exposed to interactive CD-ROM AED content showing a cardiac arrest situation where a Forerunner SAED (Philips) was used. None of the rescuers had received previous hands-on training in AED use. 3.2. Baseline BLS skills (Table 1) None of the rescuers delivered effective rescue breaths and only five rescuers (8%) performed effective chest compression. 3.3. AED skills The moment of receipt of the AED was not recorded due to technical reasons for one participant in each group. In addition, one participant from the FAED group did not succeed in attaching either electrode and one participant from the SAED group attached only a single electrode. As a result the time interval switch to electrode placement was not available in four participants. The participant who attached only one electrode was allowed to continue the protocol and therefore data on compliance were collected on 61 cases. Time intervals independent of AED type (Table 1) Since the AEDs perform identically up to the moment of shock delivery, the performance data before this point (i.e. including the intervals between receipt to switch on, and switch on to electrode placement) are not related to the differences between SAED and FAED. The interval between switch on and electrode placement was statistically different between the two groups. This interval includes tasks such as undressing, opening the electrode package and correct positioning of the electrodes on the chest. A possible explanation for the difference observed could be an imbalance between the two groups caused by the wide variability in speed of performance of these tasks.

44 K.G. Monsieurs et al. / Resuscitation 64 (2005) 41 47 Table 1 Characteristics of participants and baseline BLS skills (not influenced by AED type) FA (n = 32) SA (n = 30) P Gender (M/F) 4/28 0/30 0.04 Age (S.D.) 23 (8) 21 (5) 0.94 Practical BLS course 7 8 0.66 CD-Rom BLS 13 13 0.83 BLS skills Shake and shout 13 (41%) 8 (27%) 0.25 Free airway 7 (22%) 5 (17%) 0.60 Call ambulance 8 (25%) 11 (37%) 0.32 Effective rescue breathing 0 (0%) 0 (0%) Correct hand position 14 (44%) 15 (50%) 0.62 Effective chest compression 3 (9%) 2 (7%) 0.70 Correct ratio 15:2 8 (25%) 11 (37%) 0.32 AED time interval (sec) Receipt to switch on (S.D.) 15 (8) 20 (21) 0.7 Switch on to electrodes (S.D.) 64 (23) 56 (19) 0.04 Position of electrodes (Table 2) Only 22/62 (35%) rescuers positioned electrodes correctly. There was no difference between FAED and SAED users, as would be expected from the fact that the AEDs behave identically up to the moment of shock delivery. Time intervals related to AED type The interval between applications of electrodes to first shock (S.D.) was 22 (2) sec for FA (n = 32) and 21 (2) sec for SA (n = 30). This difference was statistically significant (P = 0.014), though without clinical relevance. The interval between the first shock to third shock (S.D.) was 48 (0.5) sec for FA and 47 (7) for SA (P < 0.001) with a range of 47 49 s for FA and 41 80 s for SA. This means that SAED users were sometimes faster than FAED users because they pressed the shock button before the end of the voice prompt. On the other hand, FAED use prevented longer intervals. Rescuer compliance during analysis and shock delivery We observed three main types of non-compliance (Table 3): o Circulation assessment (Fig. 2a) During analysis and shock delivery, rescuers assessed circulation in various ways: by palpating the wrist, the neck or even the precordial area. This occurred much Table 2 Position of electrodes Position of electrodes FA SA TOTAL Both within area 11 11 22 (35%) One within area, one crossing border 13 11 24 (39%) Both crossing border 3 4 7 (11%) One within area, one outside area 1 1 2 One crossing border, one outside area 1 1 2 Both outside area 2 1 3 Not attached 1 1 2 Total 32 30 62 There were no statistical differences between the FA and SA groups. Table 3 Types of non-compliance during the different episodes delineated by the voice prompts during the series of three shocks FA SA Total P Circulation 15/558 51/540 66/1098 < 0.0001 assessment Touching 12/558 10/540 22/1098 0.72 electrodes Other touching 3/558 13/540 16/1098 0.01 errors Total 30/558 (5%) 74/540 (14%) 104/1098 (9%) <0.0001 It should be noted that not more than one error was found during each episode. more frequently in the SA group. Most errors occurred at the beginning of the rhythm analysis sequence. o Touching electrodes (Fig. 2b) Except for one case, electrodes were touched only during the first shock and most errors occurred during the first voice prompts. This indicates that rescuers wanted to adjust the position of the electrodes or ensure proper attachment, even if the voice message prompted them not to touch the patient. o Other touching errors (Fig. 2c) These include accidental or intentional touching of the victim, such as touching clothing. Overall, rescuers made non-compliance errors in 9% (104/1098), with SAED users making 14% errors (74/540) and FA users only 5% (30/558) (Table 3). Table 4 lists the compliance for each voice prompt. Most errors occurred during the second voice prompt evaluating heart rhythm. Combining the voice prompts into an analysis group (prompts 1 4) reveals that 30/372 (8%) errors were made by FA users and 62/360 (17%) errors by SA users (P < 0.001). Errors during this analysis episode might interfere with the rhythm analysis but are not a safety risk. Combining the results for voice prompts five and six reveals that 0/186 errors were made by the FA users against 12/180 (7%) by the SA group (P < 0.001). These errors occurred immediately before or during shock delivery and are therefore a safety hazard. In the FA group, rescuers made a maximum of four errors out of 18 voice prompts, whereas in the SA group seven rescuers made between 5 to 11 errors. Fig. 3 shows that compliance increased with subsequent shocks for FAED, whereas compliance decreased for SAED. Table 4 Compliance errors for each voice prompt FA SA Total P 1 6/93 5/90 11/183 0.8 2 15/93 25/90 40/183 0.06 3 5/93 17/90 22/183 0.005 4 4/93 15/90 19/183 0.006 5 0/93 9/90 9/183 0.002 6 0/93 3/90 3/183 0.08 Total 30/558 74/540 104/1098 <0.0001

K.G. Monsieurs et al. / Resuscitation 64 (2005) 41 47 45 Fig. 2. (a) Circulation assessment (Erroneous circulation assessment for each voice prompt). (b) Touching electrodes (Erroneously touching electrodes for each voice prompt). (c) Other touching errors (Other touching errors for each voice prompt). Shock 1: grey, shock 2: white and shock 3: barred

46 K.G. Monsieurs et al. / Resuscitation 64 (2005) 41 47 Fig. 3. Errors during shocks (touching electrodes: white, circulation assessment: grey and other touching errors: barred). 3.4. BLS skills after shock delivery After delivery of three shocks, 54/61 (88%) complied with the check breathing voice prompt by checking breathing and/or the pulse (count irrespective of correctness). After the next voice prompt if no breathing, start CPR only half of the rescuers attempted rescue breathing, few attempted chest compression and one third did nothing at all. After the voice prompt maintenir surveillance 6/61 (10%) rescuers even ceased the resuscitation efforts which they had started earlier. There were no differences in behaviour between the FAED and SAED group. 4. Discussion According to the recommendations of the International Liaison Committee on Resuscitation (ILCOR) basic rescuers, or even lay people, are required to operate AEDs to improve outcome after cardiac arrest [7]. This strategy poses an enormous training challenge with regard to the operators of these devices. The current generation AEDs show improved usability and studies are emerging that the use of AEDs by minimally trained rescuers may be feasible [1 6]. Fromm and Varon showed that untrained lay rescuers could use a Heartstart 1000 (Laerdal, Norway) AED, using a simple written instruction sheet [1]. Approximately 50% of the 25 subjects had previously received BLS training. Ninetysix percent of the rescuers were able to deliver three shocks during a simulated cardiac arrest scenario. No safety data were published. It was concluded that brief instruction on AED use during BLS courses might be sufficient to prepare lay rescuers for AED use. Gundry et al. studied the use of the Forerunner AED by 15 untrained children during simulated cardiac arrest [2]. None had prior BLS training or experience with AED. All subjects placed electrode pads correctly and all remained clear of the patient during shock delivery. However, before the test the children received verbal instructions regarding pad handling and placement. The pass criteria for pad placement were quite liberal and differ from current guidelines. Mattei et al. studied 15 nurses and physiotherapists [3]. A Forerunner AED was used during a simulated cardiac arrest. Fifty-three percent showed wrong pad placement and 67% were unsafe, thereby indicating that pad position and safety are areas for improvement. Wik et al. showed that 15/27 pairs of flight attendants with no previous exposure to an AED decided to use a Forerunner AED during a simulated cardiac arrest scenario [4]. Eighty-six percent of pads were judged to be located correctly and no safety errors were observed. However, all the subjects had previous BLS training and all received a BLS/AED course manual before the test. Moreover 12 pairs of flight attendants were reluctant to use the AED. The study certainly suggests that a significant number of rescuers proficient in BLS would need only written information to use an AED effectively. Bradley et al. tested 30 untrained individuals at an airport [6]. Only eight were able to defibrillate within 3 min, the main problem being failure to apply the electrodes properly. The study supports our findings that visual and oral instructions are not adequate enough to guide untrained users, especially for applying the electrodes. From these mentioned studies, one may conclude that although current AEDs have been developed to be used by trained individuals, at least some AEDs can be used by lay rescuers with minimal or no training at all. This is an important finding because it could reduce the training burden. However, most of the studies do not address operator-device interactions adequately. Literature data on the choice between FAEDs and SAEDs is very scarce. In 1987, Stults and Cummins [5] wrote that the choice is largely subjective and that safety and efficiency were depending on good initial training and adequate skill mainte-

K.G. Monsieurs et al. / Resuscitation 64 (2005) 41 47 47 nance. The perceived increased risk of inadvertent shocks in FA mode would not exist when operated by trained rescuers. Still, current international guidelines on the use of AEDs favour the use of SAEDs reserving FAEDs for special situations, without detailing these [7]. Our results show that the Lifepak CR Plus FAED version eliminated the slower delivery of shocks by inexperienced rescuers. In addition, we observed that the students using the FAED were more compliant with the protocol than rescuers using the SAED, both during rhythm analysis and during shock delivery. The most common error was touching the patient to check for signs of a circulation (Table 3). This error occurred more in relation to the second voice prompt ( analyzing heart rhythm ) (Fig. 2a). We believe some rescuers were confused by this voice prompt which was often interpreted as an incentive to feel for a pulse whereas its goal is merely to provide information. Still, although the voice prompts were identical in both groups, the effect was much smaller in the FA group. A probable explanation is that the FA mode puts the rescuer in a more passive and secure position during analysis and shock delivery, preventing the rescuer from inappropriate actions. We recognize a number of limitations of our study. Nursing students may have a special interest in resuscitation, or a more positive attitude towards helping than the general population. The results cannot therefore be applied to other groups of first responders with certainty. A simulated cardiac arrest scenario may not necessarily predict rescuer behaviour during a real resuscitation event. Our findings are restricted to the Medtronic CR Plus AED. The study was limited to a single rescuer situation and did, therefore, not assess the performance of rescuers in the presence of bystanders or other rescuers who may touch the patient during analysis and shock delivery. 5. Conclusion Protocol compliance was increased in this group of untrained nursing students using the fully automatic version of the CR Plus. Prolonged intervals between the first to third shock were eliminated. In addition, we observed a rather high number of errors with regard to electrode positioning. BLS after defibrillation was largely inadequate. Future design of AEDs should focus on these issues by avoiding unwanted rescuer victim interactions during rhythm analysis and shock delivery, and by improved guidance for the rescuer when BLS is required. Further research is needed before the results can be applied to other groups of first responders. Acknowledgements We thank the students of the Institut Supérieur d Enseignement Infirmier for their participation and Cybèle Delwiche, Anne-Marie Champagne and Benoît Dupuis for providing logistical support. We also thank all instructors for running the testing stations. Medtronic provided the AEDs for the study. Conflict of interests: The authors of this article have no conflict of interest to report. References [1] Fromm Jr RE, Varon J. Automated external versus blind manual defibrillation by untrained lay rescuers. Resuscitation 1997;33:219 21. [2] undry JW, Comess KA, DeRook FA, Jorgenson D, Bardy GH. Comparison of naïve sixth-grade children with trained professionals in the use of an automated external defibrillator. Circulation 1999;100:1703 7. [3] Mattei LC, McKay U, Lepper MW, Soar J. Do nurses and physiotherapists require training to use an automated external defibrillator? Resuscitation 2002;53:277 80. [4] Wik L, Dorph E, Auestad B, Steen P. Evaluation of a defibrillatorbasic cardiopulmonary resuscitation programme for non medical personnel. Resuscitation 2003;56:167 72. [5] Stults KR, Cummins RO. Fully automatic versus shock advisory defibrillators: what are the issues? J Emerg Med Serv 1987;12: 71 3. [6] Bradley RN, Hamilton WH, Boyle MR, et al. Public access defibrillation programs without training are effective. Acad Emerg Med 2003;10:502 3 (abstract). [7] International Guidelines 2000 for CPR and ECC-A consensus on science. Resuscitation 2000;46:1 448. [8] Lester CA, Morgan CL, Donnelly PD, Assar D. Assessing with CARE: an innovative method of testing the approach and casualty assessment components of basic life support, using video recording. Resuscitation 1997;34:4.