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Automated external defibrillators: Implications for training qualified ambulance staff
EMS/ORIGINAL CONTRIBUTION automated external defibrillator
Automated External Defibrillators"Implications for Training Qualified Ambulance Staff From the Accident and Emergency Department, King's College Hospital,* and the
Geraldine Waiters, Bsc* Denis D'Auria, MFOM* Edward Glucksman,FRCP*
London Ambulance Service,t London, England. Received for publication March 1, 1991. Revision received November 13, 1991. Accepted for publication December 11, 1991. Presented at the 3rd International Conference on Emergency Medicine in Toronto, Ontario, Canada, 1990.
Study objective: Toinvestigate the performance of basic trained ambulance personnel using an automated external defibrillator (AED) after a short training program. Methods: One hundred ninety ambulance attendants working in London received six and one-half hours training in the use of an AED, with written feedback and continuing education regarding performance after training. Performance was assessed over a period of 15 months by analysis of report forms and ECG/audible cassette tapes from the patients who were treated. Results: Staff were able to operate the defibrillator correctly in 96% of cases and followed the protocol sequence taught in 34% of cases. The median time taken to activate the defibrillator following arrival of the ambulance at the scene of cardiac arrest was four minutes (range, one to 13 minutes). In 32% of cases, patients were intubated erroneously or moved to the ambulance before the AED was attached. Conclusion: The short course with continuing education was sufficient to train staff in AED operation, but errors in protocol compliance occurred throughout the trial. [Waiters G, D'Auria D, Glucksman E: Automated external defibrillators: Implications for training qualified ambulance staff. Ann EmergMefl June 1992;21:692-697.]
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DEFIBRILLATORS Waiters, D'Auria & Glucksman
INTRODUCTION
Automated external defibrillators (AEDs) were described first in 1979. Since then, they have been investigated extensively, allaying initial concerns over the possibility of inapp r o p r i a t e shock administration2, 3 and demonstrating that there is no difference in patient outcome between patients who are treated by operators using AEDs and those who are treated by operators using conventional defibrillators, a The m a j o r benefit of the AED is that staff with only basic life support skills can be taught to defibrillate very quickly, and theoretically, there is less need for monitoring and retraining because knowledge of the ECG is not required. Consequently, AEDs are being used more by ambulance services. In previous studies of AED use by ambulance staff, the length of AED training programs r e p o r t e d for emergency medical technicians or ambulance staff has been variable, ranging from 11 hours 5 to four hours. 6 Different methods of refresher training also have been r e p o r t e d , including monthly protocol review sessions 5 to no formal refresher training. 6 Although no specific problems have been r e p o r t e d , there have been no detailed descriptions of the performance of ambulance operators after training in AED use. In one study involving basic trained emergency medical technicians who had undergone four-hour AED training with no formal refresher training, it was r e p o r t e d that elapsed time from arrival to shock administration and protocol compliance did not deteriorate measurably, but no time intervals or further details regarding performance were given. 6 At the time this study was u n d e r t a k e n , there was no caseby-case system of medical control in operation at the London Ambulance Service, and hospital emergency departments in London have no formal role in the monitoring or continuing education of ambulance staff. In view of this, a method of prehospital care that required less monitoring and refresher training was considered advantageous. Therefore, the aim of this study was to observe and describe the performance of ambulance staff using an AED in the field in London after six and one-half hours of training with written feedback regarding performance but without formal refresher training. The basic qualification of ambulance staff in the United Kingdom is that of qualified ambulanceman/woman. To become qualified, recruits to the London Ambulance Service undergo a six-week course in all aspects of basic ambulance aid, a two-week driving course, and four weeks of practice in the field supervised by ambulance instructors. Successful candidates then are able to work on emergency ambulances without supervision. Full qualification is obtained after a p r o b a t i o n a r y year of fieldwork. The emergency ambulance system in London is a one-tier system. There is no selective deployment policy; calls are allocated on a "nearest ambulance to location of call" basis r a t h e r than according to the capabilitie~ of the crew.
38/693
At the time this study was u n d e r t a k e n , the only additional skills routinely taught were endotracheal intnbation and insertion of IV cannulae (without drug administration by either route). Staff volunteering for this training were eligible after two years of work as a qualified ambulanceman/ woman. Ambulance staff complete reports (for administrative purposes) on each patient attended, but they are not reviewed routinely. Staff trained in intubation and infusion complete an additional r e p o r t that is submitted to the ambulance training school and reviewed by ambulance instructors. During this study, treatment of prehospital cardiac arrest by qualified ambulance staff consisted of chest compressions and artificial ventilation using oxygen and airway adjuncts or endotracheal intubation in the case of staff who had completed the additional course. Staff were taught to use the AED as an adjunct to their existing life support skills. This study was u n d e r t a k e n by independent investigators with the backing of the London Ambulance Service. Monitoring of ECG/audible tapes and continuing education was carried out by the trial coordinator, a former coronary care senior nurse, who is involved in research into prehospital cardiac care and has experience in teaching basic and advanced cardiac life support methods. The defibrillator used was the Lifepak 200 ® (PhysioControl Corporation, Redmond, Washington), a semiautomatic device with three controls. The o p e r a t o r is required to press a button to initiate analysis and another to deliver a shock if advised. The third control is used to select a 360-J shock if necessary. Written instructions are given for the o p e r a t o r on a liquid crystal display, but no ECG readout is given. A cassette r e c o r d e r i n c o r p o r a t e d in the AED produces a continuous ECG and audible record whenever the device is switched on. The electronic advisory system of the Lifepak 200 ® AED allows shocks to be given for ventricular fibrillation and ventricular tachycardia at rates of more than 180. MATERIALS
AND
METHODS
One h u n d r e d ninety staff members from eight ambulance stations were trained to use the AED. All were qu~ilified ambulance personnel; at the time of training, 26 also were trained in intubation and infusion. Training of ambulance staff began in December 1986 and was completed by mid J a n u a r y 1987. Patient data were collected from F e b r u a r y 1, 1987, through May 31, 1988. Training consisted of six and one-half hours of lectures and practical sessions. These included review of basic cardiology, including cardiac arrest etiology, ECG rhythms encountered, and their treatment (with emphasis on defibrillation); the "chain of survival" concept, the importance of early basic and advanced cardiac life support, and critical time intervals; review of basic life support and use of airway adjuncts; demonstration of the AED, including its capabilities; safety points, explanation of the protocol including a step-by-step
ANNALS OF EMERGENCYMEDICINE 21:6 JUNE1992
DEFIBRILLATORS Walters, D'Auria & Glucksman
demonstration of the protocol sequence; and practice using the AED with a manikin and an ECG rhythm simulator. The following protocol points were stressed throughout training. First, the AED should be taken to any patient when the emergency call suggests a possibility of cardiac arrest. Second, the AED should be attached as soon as possible after arrival at the scene of cardiac arrest. Third, the patient should not be moved to the ambulance before activating the AED, unless conditions are hazardous. Fourth, for intubation-trained staff, intubation should be carried out after, rather than before, the use of the AED. Last, in the case of patients who arrest en route to the hospital, crews are required to stop the vehicle and activate the AED rather than continue to the hospital. Staff were trained to use the AED according to a protocol sequence (Figure 1) taken from an earlier report. 7 At the end of the course, the staff were required to demonstrate satisfactorily the use of the AED according to the three-shock protocol using the manikin and rhythm simulator. All participants were successful.
Figure 1. Protocol for use of AED
VerifyArrest J [CommenceCPR] [ AttachAED ]
[ Ana'y,e I
L Ana'yze j
I
[ ShockAdv~sed]
] ShockAdvisod
I ShockAdvised
I CheckPulse I
I CheckPulsq
[
CheckPulse
[ Shock200J ]
I Shock200J~
I
Shock200 J
[ CPR1Oyc,e ]
I CPRtCycle~
CPR 1 Cycle
[ CheckPulse ]
I CheckPulse I
CheckPulse
Analyze
Training included a session on the documentation requirements of the trial. Staff were asked to give as much verbal information as possible by tape and to leave the tape r u n n i n g for as long as possible. Patient report forms requested the patient's personal information, details of the arrest incident, treatment given by the ambulance crew, time of collapse, time at which CPR commenced, time of ambulance arrival, and time of AED attachment. After each cardiac arrest call was completed, the report form was sent, with the ECG and audible tape, to the trial coordinator. There were no facilities to allow playback of tapes at local hospitals or at participating ambulance stations. Immediately after receipt of patient report forms, letters were sent to the involved staff regarding their performances. When errors in performance had occurred, these were pointed out and an explanation of why such errors may be detrimental was given. Good practice was reinforced. These letters usually were received within a week of the report form being submitted. Monthly newsletters were sent to the individual ambulance stations, giving details of the patients treated and outcomes, reinforcing information given during training, and drawing attention to any common mistakes. The course coordinator spent one day per week visiting in t u r n each of the ambulance stations involved and attending calls with ambulance crews. No formal refresher training sessions were given. Performance was assessed for 15 months after training. ECG/audible tapes were analyzed in conjunction with reporting forms to assess operator performance. The aim of this assessment was to observe whether the crews practiced what had been taught. In cases in which shocks were advised and sufficient information was available on tape, performance was assessed for the following. In correct AED operation, the AED operator initiates ECG analysis and delivers a shock when advised.
Figure 2. Patients treated with AEDs
273 Cases (100%) 6 Not Attached
(2%) l
o Not IntubateUntil AfterAED Use j
Transport
Do Not MovePatient Until] AfterAED Use in Caseof Secondary Arrest,RepeatProtocol
JUNE 1992 21:6 ANNALSOF EMERGENCYMEDICINE
~
- 267 Attached (98%) J
104 Shocks Advised I (38%) -j-
t
~ 163 No Shock Advised [ (60%)
I 95 Data Available (35%)
694/ 39
DEFIBRILLATORS
Walters, D ' A u r i a & G l u c k s m a n
Protocol sequence compliance requires that the AED operator administers no more than three shocks, administers the shocks in the correct voltage sequence (200,200, and 360 J), gives interposed CPR between each shock and subsequent reanalysis, gives the order to stand clear before the shocks are delivered, and initiates reanalysis of the ECG after each of the first two shocks. The speed with which the defibrillator was attached and activated involves determination of time from arrival of the ambulance at the address given by the emergency call to activation of the AED, whether intubation was performed before or after AED attachment, and whether the patient was moved to the ambulance before AED attachment. RESULTS
Two hundred seventy-three victims of prehospital cardiac arrest were attended by crews equipped with the AED (Figure 2). Performance and AED operation were assessed in the 95 cases in which tapes were available and shocks were given. I n 92 cases (97%), the AED was operated correctly after attachment. In one case, there was a 29-second delay between attachment of the electrodes and the operator pressing the "analyze" control during which no action was taken. In another case, the operator pressed the "shock" control before the AED was charged. When the AED reached the charged state, the operator did not press the shock control and the charge was dissipated. The patient did not receive a shock. In one additional case, the operator failed to activate the 360-J button at the appropriate point to increase the voltage of the third shock. In 32 cases (35%), there were no errors in the protocol sequence. In 33 cases (36%), one error was made; in 20 cases (22%), two errors were made; and in seven cases (8%), three errors were made. Interposed CPR was omitted in 33 cases (35%), the operator failed to give the order to stand clear in 22 cases (23%), shocks were not given according to the correct voltage sequence in 19 cases (20%), more than three shocks were given in 12 cases (13%), and the operator failed to reanalyze the ECG following shock administration in eight cases (9%). Complete data were not available in three cases.
Table. Time from ambulance arrival to AED attachment No of Not Applicable: Time Cases(%) Unab|etoAseess Known
Median (rain}
Range (min)
All cases
95 (100)
...
93
4
1-13
AED attached first
57 (60)
3
57
3
1-11
Moved before AED attached
27 (28)
3
27
7
1-13
7 {17)
...
6
6.5
2-11
Intubated before AED attached~
The n u m b e r of cases in which patients were intubated or moved before AED attachment and where the AED was attached first and the median and range of times from ambulance arrival to AED activation in these cases are shown (Table). In 19 cases (20%), the protocol sequence was performed without errors, and the AED was attached before the patient was moved or intubated. DISCUSSION
In this study, there were few cases in which the ambulance staff was unable to operate the AED after attachment. The protocol sequence was performed without errors in 35% of cases in which shocks were administered. In the majority of cases involving protocol sequence errors (55%), only one error was made. For all patients, the median time between ambulance arrival and AED attachment was four minutes (range, one to 13 minutes). Some delay is expected because several minutes may be spent locating the patient (difficulty in locating patients in high-rise buildings accounted for some of the very long intervals recorded), confirming cardiac arrest, commencing basic life support, removing clothing, and attaching the AED. Patients either were moved to the ambulance or were intubated before AED attachment in 32% of cases. These practices were contrary to the protocol stressed during training and feedback. In these patients, the median times from arrival of the ambulance to defibrillator attachment were several minutes longer (seven and 6.5 minutes, respectively; range, one to 13 minutes) than those in patients in whom the AED was attached first (three minutes; range, one to 11 minutes). These unfavorable practices occurred throughout the trial and were independent of the time interval between cases. The results suggest that the crews remembered how to operate the AED, b u t protocol compliance, in terms of both using the AED at the earliest possible convenience and the sequence once the AED is attached, was not retained well after training. The training program was similar in length and content to that given in other areas, 6 but as previous reports have not commented on the same aspects of operator performance, we do not know whether this degree of compliance is comparable with that found elsewhere. The difficulties in retaining after training psychomotor skills that are not used regularly are well known, an obvious example being the skills of basic life support. 8 The protocol sequence may have been too difficult to retain after a short course, even with regular written reminders. We had hoped that delays in attachment of the AED would be corrected by stressing repeatedly the importance of rapid defibrillation in both general and individual feedback, but this was not the case. We can only speculate on the reasons. First, a more direct, person-to-person method of continuing
*Total number of patients intubated, 41.
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DEFIBRILLATORS Walters, D'Auria & Glucksman
education performed immediately after each case might have been more successful than written feedback. A second possibility is that as outside investigators, the authors were not in a position to exercise any measures to deter crews from disregarding the guidelines that had been given or to excuse crews from fieldwork for retraining. The most probable explanation is that the short course with feedback was not sufficient to convince the staff to change their established practices in favor of prompt defibrillation. Ambulance staff developed particular working practices as a result of previous training (reflected in the way priority was given to treating the airway by some of the intubation-trained staff, and proceeding to the hospital rapidly in six cases rather than stopping the ambulance to use the AED) and, by experience, to suit the nature of the majority of ambulance work in London. Ambulance staff appeared to have developed the practice of locating and assessing patients and then returning to the ambulance for appropriate equipment because of the inaccurate descriptions of patients' complaints received in emergency calls. This pattern results in a pernicious delay for the cardiac arrest victim. These findings were gained by informal observation of the day-to-day practices of the ambulance staff and therefore are difficult to quantify. It is unlikely that this problem is unique to London and may go unnoticed without careful monitoring of performance. Of the 95 patients who received shocks, six (6%) survived. This is an insufficient n u m b e r of survivors to assess the effects of the errors detected on survival. It must be assumed that any delays in defibrillation to patients who were in ventricular fibrillation or ventricular tachycardia would have adversely affected their chances of survival. Studies have shown that if patients are not defibrillated within eight to ten minutes after collapse, the chances of survival fall sharply. 9 In this study, in cases in which patients were moved or intubated before AED attachment, regardless of ambulance response time, the median delay between ambulance arrival and defibrillator attachment (seven minutes) was sufficient to reduce the likelihood of survival of patients in ventricular fibrillation. In the 32% of patients who were intubated or moved before AED attachment, shocks subsequently were advised and given, but none of these patients survived. It is possible that earlier shock administration might have been successful in some of these victims. Although speed of defibrillation has been shown to be related unequivocally to patient outcome, elements of the protocol sequence have not. The protocol sequence errors that are documented represent deviations from the protocol taught, but failure to give interposed CPR or administration of more than three shocks is unlikely to have had a deleterious effect on patient survival. Failure to give a third shock at 360 J might have reduced the chances of survival in a small n u m b e r of patients because administration of a higherenergy shock may be effective when lower-energy shocks
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have failed to defibrillate, t0 When the operator failed to reanalyze the ECG after either the first or the second shock administration, any patient still in ventricular fibrillation at this point would not have received a subsequent shock. Clearing the area is an important safety aspect of defibrillation protocols and should be maintained. In some of the cases in which the operator did not give a verbal order to stand clear, this could have been because no one else was present at the time, which would not have been made apparent by listening to the tape. In four of the six victims who survived, there were errors in protocol sequence compliance, but no survivor was intubated or moved before AED attachment. Improving retention of the protocol sequence may be achieved by increasing the length of the initial training program or by having regular practical refresher sessions. The danger of increasing the amount of formal practice for AED operators is that the advantages of brief training will be diminished, and any extra training commitment will reduce indirectly the n u m b e r of operators who can be trained. If absolute compliance with a protocol sequence is considered important, an alternative option may be to simplify the sequence by omitting less-important stages. Attempts already have been made to do this; for example, in more recently devised protocols, interposed CPR is not included. CONCLUSION
Staff remembered how to operate an AED after a short training course, but elements of the protocol often were forgotten. Extra formal training may improve protocol sequence compliance, but ensuring that ambulance staff use the AED at the earliest possible convenience requires a change in their established practices, and this may be a more difficult problem to resolve. We recommend that training in AED use be carried out during initial ambulance staff and emergency medical technician training to establish defibrillation as a priority before working practices develop that might impede early shock delivery to patients in ventricular fibrillation. Second, the considerable delays in defibrillation that we have described would not have been identified without careful monitoring of ECG/audible cassette tapes in conjunction with written report forms. Monitoring of ECG/audible cassette tapes, in addition to report forms, is essential to identify deficiencies in performance that may reduce the chances of successful resuscitation. Monitoring of report forms alone does not yield sufficient information. Third, AED operators should be monitored in the aspects described, that is, speed; special attention should be paid to the way in which use of the AED is incorporated into the care of the cardiac arrest patient, from ambulance arrival, to AED operation, and to protocol compliance after AED attachment.
696/41
DEFIBRILLATORS
Walters, D'Auria & Glucksman
Fourth, effective monitoring as described must be backed up by stringent medical control to ensure that any deficiencies found in performance are rectified. The authors thank British Telecom PIc for funding this research; Physic-Control Corporation for loaning the defibrillators and providing electrodes and tapes; Dr Debbie Shears for computation assistance; Mr KG Smith, former Chief Training Officer, and the instructors at the Regional Training Centre of the London Ambulance Service for their assistance with training; and the ambulance crews for submitting data.
REFERENCES 1. Daick AW, Welborn WS, Bullman R6, et al: An automatic cardiac resuscitator for emergency treatment of cardiac arrest. Med Instrum 1979;13:78. 2. Bosenthal E, Carrel B, Vincent R: Automated external defibrillation: Laboratory evaluation. Int J Cardio11984;5:441-447. 3. Cummins RO, Eisenberg M, Bergner L, et al: Sensitivity, accuracy, and safety of an automatic external defibrillator- Report of a field evaluation. Lancet1984;2:318-320. 4. Cummins RO, Eisenberg MS, Litvvin PE: Automatic external defibrillators used by emergency medical technicians - - A controlled clinical trial. J.4MA 1987;257:1605-1610. 5.6entile D, Auerbach P, 6affron J, et al: Prehespital defibrillation by emergency medical technicians: Results of a pilot study in Tennessee. J Tenn MeflAssoc 1988;3:144-148. 6. Stults HR, Brown DD, Kerber RE: Efficacy of an automated external defibrillator in the management of out-of-hospital cardiac arrest: Validation of the diagnostic algorithm and initial clinical experience in a rural environment. Circulation 1986;73:701-709. 7. Cummins BO, Eisenberg MS, Moore TR, et al: Automatic external defibrillators: Clinical, training, psychological, and public health issues. Ann Emerg Med 1985;14:755760. 8. Weaver FJ, Ramirez A6, Dorfman SB, et al: Trainees" retention of cardiopulmonary resuscitation. How quickly they forget. JAMA 1979;241:901-903. 9. Eisenberg MS, Bergner L, Hallstrom A: Cardiac resuscitation in the community. Importance of rapid provision and implications for program planning. JAMA 1979;241:1905-1907. 10. Kerber RE, Grayzel J, Hoyt R, et al: Transthoracic resistance in human defibrillation. Influence of body weight, chest size, serial shocks, paddle size and paddle contact pressure. Circulation 1981;63:676.
Address for reprints: Geraldine Waiters, Bsc, Accident and Emergency Department, King's College Hospital, Denmark Hill, London, England SE5 9RS.
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Automated External Defibrillators"Implications for Training Qualified Ambulance Staff From the Accident and Emergency Department, King's College Hospital,* and the
Geraldine Waiters, Bsc* Denis D'Auria, MFOM* Edward Glucksman,FRCP*
London Ambulance Service,t London, England. Received for publication March 1, 1991. Revision received November 13, 1991. Accepted for publication December 11, 1991. Presented at the 3rd International Conference on Emergency Medicine in Toronto, Ontario, Canada, 1990.
Study objective: Toinvestigate the performance of basic trained ambulance personnel using an automated external defibrillator (AED) after a short training program. Methods: One hundred ninety ambulance attendants working in London received six and one-half hours training in the use of an AED, with written feedback and continuing education regarding performance after training. Performance was assessed over a period of 15 months by analysis of report forms and ECG/audible cassette tapes from the patients who were treated. Results: Staff were able to operate the defibrillator correctly in 96% of cases and followed the protocol sequence taught in 34% of cases. The median time taken to activate the defibrillator following arrival of the ambulance at the scene of cardiac arrest was four minutes (range, one to 13 minutes). In 32% of cases, patients were intubated erroneously or moved to the ambulance before the AED was attached. Conclusion: The short course with continuing education was sufficient to train staff in AED operation, but errors in protocol compliance occurred throughout the trial. [Waiters G, D'Auria D, Glucksman E: Automated external defibrillators: Implications for training qualified ambulance staff. Ann EmergMefl June 1992;21:692-697.]
JUNE1992 21:6 ANNALS 0FEMERGENCYMEDIClNE
692/37
DEFIBRILLATORS Waiters, D'Auria & Glucksman
INTRODUCTION
Automated external defibrillators (AEDs) were described first in 1979. Since then, they have been investigated extensively, allaying initial concerns over the possibility of inapp r o p r i a t e shock administration2, 3 and demonstrating that there is no difference in patient outcome between patients who are treated by operators using AEDs and those who are treated by operators using conventional defibrillators, a The m a j o r benefit of the AED is that staff with only basic life support skills can be taught to defibrillate very quickly, and theoretically, there is less need for monitoring and retraining because knowledge of the ECG is not required. Consequently, AEDs are being used more by ambulance services. In previous studies of AED use by ambulance staff, the length of AED training programs r e p o r t e d for emergency medical technicians or ambulance staff has been variable, ranging from 11 hours 5 to four hours. 6 Different methods of refresher training also have been r e p o r t e d , including monthly protocol review sessions 5 to no formal refresher training. 6 Although no specific problems have been r e p o r t e d , there have been no detailed descriptions of the performance of ambulance operators after training in AED use. In one study involving basic trained emergency medical technicians who had undergone four-hour AED training with no formal refresher training, it was r e p o r t e d that elapsed time from arrival to shock administration and protocol compliance did not deteriorate measurably, but no time intervals or further details regarding performance were given. 6 At the time this study was u n d e r t a k e n , there was no caseby-case system of medical control in operation at the London Ambulance Service, and hospital emergency departments in London have no formal role in the monitoring or continuing education of ambulance staff. In view of this, a method of prehospital care that required less monitoring and refresher training was considered advantageous. Therefore, the aim of this study was to observe and describe the performance of ambulance staff using an AED in the field in London after six and one-half hours of training with written feedback regarding performance but without formal refresher training. The basic qualification of ambulance staff in the United Kingdom is that of qualified ambulanceman/woman. To become qualified, recruits to the London Ambulance Service undergo a six-week course in all aspects of basic ambulance aid, a two-week driving course, and four weeks of practice in the field supervised by ambulance instructors. Successful candidates then are able to work on emergency ambulances without supervision. Full qualification is obtained after a p r o b a t i o n a r y year of fieldwork. The emergency ambulance system in London is a one-tier system. There is no selective deployment policy; calls are allocated on a "nearest ambulance to location of call" basis r a t h e r than according to the capabilitie~ of the crew.
38/693
At the time this study was u n d e r t a k e n , the only additional skills routinely taught were endotracheal intnbation and insertion of IV cannulae (without drug administration by either route). Staff volunteering for this training were eligible after two years of work as a qualified ambulanceman/ woman. Ambulance staff complete reports (for administrative purposes) on each patient attended, but they are not reviewed routinely. Staff trained in intubation and infusion complete an additional r e p o r t that is submitted to the ambulance training school and reviewed by ambulance instructors. During this study, treatment of prehospital cardiac arrest by qualified ambulance staff consisted of chest compressions and artificial ventilation using oxygen and airway adjuncts or endotracheal intubation in the case of staff who had completed the additional course. Staff were taught to use the AED as an adjunct to their existing life support skills. This study was u n d e r t a k e n by independent investigators with the backing of the London Ambulance Service. Monitoring of ECG/audible tapes and continuing education was carried out by the trial coordinator, a former coronary care senior nurse, who is involved in research into prehospital cardiac care and has experience in teaching basic and advanced cardiac life support methods. The defibrillator used was the Lifepak 200 ® (PhysioControl Corporation, Redmond, Washington), a semiautomatic device with three controls. The o p e r a t o r is required to press a button to initiate analysis and another to deliver a shock if advised. The third control is used to select a 360-J shock if necessary. Written instructions are given for the o p e r a t o r on a liquid crystal display, but no ECG readout is given. A cassette r e c o r d e r i n c o r p o r a t e d in the AED produces a continuous ECG and audible record whenever the device is switched on. The electronic advisory system of the Lifepak 200 ® AED allows shocks to be given for ventricular fibrillation and ventricular tachycardia at rates of more than 180. MATERIALS
AND
METHODS
One h u n d r e d ninety staff members from eight ambulance stations were trained to use the AED. All were qu~ilified ambulance personnel; at the time of training, 26 also were trained in intubation and infusion. Training of ambulance staff began in December 1986 and was completed by mid J a n u a r y 1987. Patient data were collected from F e b r u a r y 1, 1987, through May 31, 1988. Training consisted of six and one-half hours of lectures and practical sessions. These included review of basic cardiology, including cardiac arrest etiology, ECG rhythms encountered, and their treatment (with emphasis on defibrillation); the "chain of survival" concept, the importance of early basic and advanced cardiac life support, and critical time intervals; review of basic life support and use of airway adjuncts; demonstration of the AED, including its capabilities; safety points, explanation of the protocol including a step-by-step
ANNALS OF EMERGENCYMEDICINE 21:6 JUNE1992
DEFIBRILLATORS Walters, D'Auria & Glucksman
demonstration of the protocol sequence; and practice using the AED with a manikin and an ECG rhythm simulator. The following protocol points were stressed throughout training. First, the AED should be taken to any patient when the emergency call suggests a possibility of cardiac arrest. Second, the AED should be attached as soon as possible after arrival at the scene of cardiac arrest. Third, the patient should not be moved to the ambulance before activating the AED, unless conditions are hazardous. Fourth, for intubation-trained staff, intubation should be carried out after, rather than before, the use of the AED. Last, in the case of patients who arrest en route to the hospital, crews are required to stop the vehicle and activate the AED rather than continue to the hospital. Staff were trained to use the AED according to a protocol sequence (Figure 1) taken from an earlier report. 7 At the end of the course, the staff were required to demonstrate satisfactorily the use of the AED according to the three-shock protocol using the manikin and rhythm simulator. All participants were successful.
Figure 1. Protocol for use of AED
VerifyArrest J [CommenceCPR] [ AttachAED ]
[ Ana'y,e I
L Ana'yze j
I
[ ShockAdv~sed]
] ShockAdvisod
I ShockAdvised
I CheckPulse I
I CheckPulsq
[
CheckPulse
[ Shock200J ]
I Shock200J~
I
Shock200 J
[ CPR1Oyc,e ]
I CPRtCycle~
CPR 1 Cycle
[ CheckPulse ]
I CheckPulse I
CheckPulse
Analyze
Training included a session on the documentation requirements of the trial. Staff were asked to give as much verbal information as possible by tape and to leave the tape r u n n i n g for as long as possible. Patient report forms requested the patient's personal information, details of the arrest incident, treatment given by the ambulance crew, time of collapse, time at which CPR commenced, time of ambulance arrival, and time of AED attachment. After each cardiac arrest call was completed, the report form was sent, with the ECG and audible tape, to the trial coordinator. There were no facilities to allow playback of tapes at local hospitals or at participating ambulance stations. Immediately after receipt of patient report forms, letters were sent to the involved staff regarding their performances. When errors in performance had occurred, these were pointed out and an explanation of why such errors may be detrimental was given. Good practice was reinforced. These letters usually were received within a week of the report form being submitted. Monthly newsletters were sent to the individual ambulance stations, giving details of the patients treated and outcomes, reinforcing information given during training, and drawing attention to any common mistakes. The course coordinator spent one day per week visiting in t u r n each of the ambulance stations involved and attending calls with ambulance crews. No formal refresher training sessions were given. Performance was assessed for 15 months after training. ECG/audible tapes were analyzed in conjunction with reporting forms to assess operator performance. The aim of this assessment was to observe whether the crews practiced what had been taught. In cases in which shocks were advised and sufficient information was available on tape, performance was assessed for the following. In correct AED operation, the AED operator initiates ECG analysis and delivers a shock when advised.
Figure 2. Patients treated with AEDs
273 Cases (100%) 6 Not Attached
(2%) l
o Not IntubateUntil AfterAED Use j
Transport
Do Not MovePatient Until] AfterAED Use in Caseof Secondary Arrest,RepeatProtocol
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~
- 267 Attached (98%) J
104 Shocks Advised I (38%) -j-
t
~ 163 No Shock Advised [ (60%)
I 95 Data Available (35%)
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Protocol sequence compliance requires that the AED operator administers no more than three shocks, administers the shocks in the correct voltage sequence (200,200, and 360 J), gives interposed CPR between each shock and subsequent reanalysis, gives the order to stand clear before the shocks are delivered, and initiates reanalysis of the ECG after each of the first two shocks. The speed with which the defibrillator was attached and activated involves determination of time from arrival of the ambulance at the address given by the emergency call to activation of the AED, whether intubation was performed before or after AED attachment, and whether the patient was moved to the ambulance before AED attachment. RESULTS
Two hundred seventy-three victims of prehospital cardiac arrest were attended by crews equipped with the AED (Figure 2). Performance and AED operation were assessed in the 95 cases in which tapes were available and shocks were given. I n 92 cases (97%), the AED was operated correctly after attachment. In one case, there was a 29-second delay between attachment of the electrodes and the operator pressing the "analyze" control during which no action was taken. In another case, the operator pressed the "shock" control before the AED was charged. When the AED reached the charged state, the operator did not press the shock control and the charge was dissipated. The patient did not receive a shock. In one additional case, the operator failed to activate the 360-J button at the appropriate point to increase the voltage of the third shock. In 32 cases (35%), there were no errors in the protocol sequence. In 33 cases (36%), one error was made; in 20 cases (22%), two errors were made; and in seven cases (8%), three errors were made. Interposed CPR was omitted in 33 cases (35%), the operator failed to give the order to stand clear in 22 cases (23%), shocks were not given according to the correct voltage sequence in 19 cases (20%), more than three shocks were given in 12 cases (13%), and the operator failed to reanalyze the ECG following shock administration in eight cases (9%). Complete data were not available in three cases.
Table. Time from ambulance arrival to AED attachment No of Not Applicable: Time Cases(%) Unab|etoAseess Known
Median (rain}
Range (min)
All cases
95 (100)
...
93
4
1-13
AED attached first
57 (60)
3
57
3
1-11
Moved before AED attached
27 (28)
3
27
7
1-13
7 {17)
...
6
6.5
2-11
Intubated before AED attached~
The n u m b e r of cases in which patients were intubated or moved before AED attachment and where the AED was attached first and the median and range of times from ambulance arrival to AED activation in these cases are shown (Table). In 19 cases (20%), the protocol sequence was performed without errors, and the AED was attached before the patient was moved or intubated. DISCUSSION
In this study, there were few cases in which the ambulance staff was unable to operate the AED after attachment. The protocol sequence was performed without errors in 35% of cases in which shocks were administered. In the majority of cases involving protocol sequence errors (55%), only one error was made. For all patients, the median time between ambulance arrival and AED attachment was four minutes (range, one to 13 minutes). Some delay is expected because several minutes may be spent locating the patient (difficulty in locating patients in high-rise buildings accounted for some of the very long intervals recorded), confirming cardiac arrest, commencing basic life support, removing clothing, and attaching the AED. Patients either were moved to the ambulance or were intubated before AED attachment in 32% of cases. These practices were contrary to the protocol stressed during training and feedback. In these patients, the median times from arrival of the ambulance to defibrillator attachment were several minutes longer (seven and 6.5 minutes, respectively; range, one to 13 minutes) than those in patients in whom the AED was attached first (three minutes; range, one to 11 minutes). These unfavorable practices occurred throughout the trial and were independent of the time interval between cases. The results suggest that the crews remembered how to operate the AED, b u t protocol compliance, in terms of both using the AED at the earliest possible convenience and the sequence once the AED is attached, was not retained well after training. The training program was similar in length and content to that given in other areas, 6 but as previous reports have not commented on the same aspects of operator performance, we do not know whether this degree of compliance is comparable with that found elsewhere. The difficulties in retaining after training psychomotor skills that are not used regularly are well known, an obvious example being the skills of basic life support. 8 The protocol sequence may have been too difficult to retain after a short course, even with regular written reminders. We had hoped that delays in attachment of the AED would be corrected by stressing repeatedly the importance of rapid defibrillation in both general and individual feedback, but this was not the case. We can only speculate on the reasons. First, a more direct, person-to-person method of continuing
*Total number of patients intubated, 41.
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DEFIBRILLATORS Walters, D'Auria & Glucksman
education performed immediately after each case might have been more successful than written feedback. A second possibility is that as outside investigators, the authors were not in a position to exercise any measures to deter crews from disregarding the guidelines that had been given or to excuse crews from fieldwork for retraining. The most probable explanation is that the short course with feedback was not sufficient to convince the staff to change their established practices in favor of prompt defibrillation. Ambulance staff developed particular working practices as a result of previous training (reflected in the way priority was given to treating the airway by some of the intubation-trained staff, and proceeding to the hospital rapidly in six cases rather than stopping the ambulance to use the AED) and, by experience, to suit the nature of the majority of ambulance work in London. Ambulance staff appeared to have developed the practice of locating and assessing patients and then returning to the ambulance for appropriate equipment because of the inaccurate descriptions of patients' complaints received in emergency calls. This pattern results in a pernicious delay for the cardiac arrest victim. These findings were gained by informal observation of the day-to-day practices of the ambulance staff and therefore are difficult to quantify. It is unlikely that this problem is unique to London and may go unnoticed without careful monitoring of performance. Of the 95 patients who received shocks, six (6%) survived. This is an insufficient n u m b e r of survivors to assess the effects of the errors detected on survival. It must be assumed that any delays in defibrillation to patients who were in ventricular fibrillation or ventricular tachycardia would have adversely affected their chances of survival. Studies have shown that if patients are not defibrillated within eight to ten minutes after collapse, the chances of survival fall sharply. 9 In this study, in cases in which patients were moved or intubated before AED attachment, regardless of ambulance response time, the median delay between ambulance arrival and defibrillator attachment (seven minutes) was sufficient to reduce the likelihood of survival of patients in ventricular fibrillation. In the 32% of patients who were intubated or moved before AED attachment, shocks subsequently were advised and given, but none of these patients survived. It is possible that earlier shock administration might have been successful in some of these victims. Although speed of defibrillation has been shown to be related unequivocally to patient outcome, elements of the protocol sequence have not. The protocol sequence errors that are documented represent deviations from the protocol taught, but failure to give interposed CPR or administration of more than three shocks is unlikely to have had a deleterious effect on patient survival. Failure to give a third shock at 360 J might have reduced the chances of survival in a small n u m b e r of patients because administration of a higherenergy shock may be effective when lower-energy shocks
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have failed to defibrillate, t0 When the operator failed to reanalyze the ECG after either the first or the second shock administration, any patient still in ventricular fibrillation at this point would not have received a subsequent shock. Clearing the area is an important safety aspect of defibrillation protocols and should be maintained. In some of the cases in which the operator did not give a verbal order to stand clear, this could have been because no one else was present at the time, which would not have been made apparent by listening to the tape. In four of the six victims who survived, there were errors in protocol sequence compliance, but no survivor was intubated or moved before AED attachment. Improving retention of the protocol sequence may be achieved by increasing the length of the initial training program or by having regular practical refresher sessions. The danger of increasing the amount of formal practice for AED operators is that the advantages of brief training will be diminished, and any extra training commitment will reduce indirectly the n u m b e r of operators who can be trained. If absolute compliance with a protocol sequence is considered important, an alternative option may be to simplify the sequence by omitting less-important stages. Attempts already have been made to do this; for example, in more recently devised protocols, interposed CPR is not included. CONCLUSION
Staff remembered how to operate an AED after a short training course, but elements of the protocol often were forgotten. Extra formal training may improve protocol sequence compliance, but ensuring that ambulance staff use the AED at the earliest possible convenience requires a change in their established practices, and this may be a more difficult problem to resolve. We recommend that training in AED use be carried out during initial ambulance staff and emergency medical technician training to establish defibrillation as a priority before working practices develop that might impede early shock delivery to patients in ventricular fibrillation. Second, the considerable delays in defibrillation that we have described would not have been identified without careful monitoring of ECG/audible cassette tapes in conjunction with written report forms. Monitoring of ECG/audible cassette tapes, in addition to report forms, is essential to identify deficiencies in performance that may reduce the chances of successful resuscitation. Monitoring of report forms alone does not yield sufficient information. Third, AED operators should be monitored in the aspects described, that is, speed; special attention should be paid to the way in which use of the AED is incorporated into the care of the cardiac arrest patient, from ambulance arrival, to AED operation, and to protocol compliance after AED attachment.
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DEFIBRILLATORS
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Fourth, effective monitoring as described must be backed up by stringent medical control to ensure that any deficiencies found in performance are rectified. The authors thank British Telecom PIc for funding this research; Physic-Control Corporation for loaning the defibrillators and providing electrodes and tapes; Dr Debbie Shears for computation assistance; Mr KG Smith, former Chief Training Officer, and the instructors at the Regional Training Centre of the London Ambulance Service for their assistance with training; and the ambulance crews for submitting data.
REFERENCES 1. Daick AW, Welborn WS, Bullman R6, et al: An automatic cardiac resuscitator for emergency treatment of cardiac arrest. Med Instrum 1979;13:78. 2. Bosenthal E, Carrel B, Vincent R: Automated external defibrillation: Laboratory evaluation. Int J Cardio11984;5:441-447. 3. Cummins RO, Eisenberg M, Bergner L, et al: Sensitivity, accuracy, and safety of an automatic external defibrillator- Report of a field evaluation. Lancet1984;2:318-320. 4. Cummins RO, Eisenberg MS, Litvvin PE: Automatic external defibrillators used by emergency medical technicians - - A controlled clinical trial. J.4MA 1987;257:1605-1610. 5.6entile D, Auerbach P, 6affron J, et al: Prehespital defibrillation by emergency medical technicians: Results of a pilot study in Tennessee. J Tenn MeflAssoc 1988;3:144-148. 6. Stults HR, Brown DD, Kerber RE: Efficacy of an automated external defibrillator in the management of out-of-hospital cardiac arrest: Validation of the diagnostic algorithm and initial clinical experience in a rural environment. Circulation 1986;73:701-709. 7. Cummins BO, Eisenberg MS, Moore TR, et al: Automatic external defibrillators: Clinical, training, psychological, and public health issues. Ann Emerg Med 1985;14:755760. 8. Weaver FJ, Ramirez A6, Dorfman SB, et al: Trainees" retention of cardiopulmonary resuscitation. How quickly they forget. JAMA 1979;241:901-903. 9. Eisenberg MS, Bergner L, Hallstrom A: Cardiac resuscitation in the community. Importance of rapid provision and implications for program planning. JAMA 1979;241:1905-1907. 10. Kerber RE, Grayzel J, Hoyt R, et al: Transthoracic resistance in human defibrillation. Influence of body weight, chest size, serial shocks, paddle size and paddle contact pressure. Circulation 1981;63:676.
Address for reprints: Geraldine Waiters, Bsc, Accident and Emergency Department, King's College Hospital, Denmark Hill, London, England SE5 9RS.
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