a b s t r a c t

Background: Bystanders play a vital role in Public access defibrillation (PAD) in out-of-hospital cardiac arrest (OHCA). Dual dispatch of First responders (FR) alongside emergency medical services (EMS) can reduce time to first defibrillation. The aim of this study was to describe the use of automated external defibrillators (AEDs) in OHCAs before EMS arrival.

Methods: All OHCA cases with a shockable rhythm in which an AED was used prior to the arrival of EMS between 2008 and 2015 in western Sweden were eligible for inclusion. Data from the Swedish Register for Cardiopulmo- nary Resuscitation (SRCR) were used for analysis, on-site bystander and FR defibrillation were compared with EMS defibrillation in the final analysis.

Results: Of the reported 6675 cases, 24% suffered ventricular fibrillation (VF), 162 patients (15%) of all VF cases were defibrillated before EMS arrival, 46% with a public AED on site. The proportion of cases defibrillated before EMS arrival increased from 5% in 2008 to 20% in 2015 (p b 0.001). During this period, 30-day survival increased in patients with VF from 22% to 28% (p = 0.04) and was highest when an AED was used on site (68%), with a median delay of 6.5 min from collapse to defibrillation. Adjusted odds ratio for on-site defibrillation versus dispatched defibrillation for 30-day survival was 2.45 (95% CI: 1.02-5.95).

Conclusions: The use of AEDs before the arrival of EMS increased over time. This was associated with an increased 30-day survival among patients with VF. Thirty-day survival was highest when an AED was used on site before EMS arrival.

(C) 2017

Introduction

Every year, out-of-hospital cardiac arrest (OHCA) affects some 700,000 people in Europe and about 350,000 in the USA [1,2]. Survival is highly dependent on early cardiopulmonary resuscitation (CPR) and Early defibrillation with an Automated external defibrillator [3,4,5].

The principal factor when it comes to improvements in the survival rate is reducing the delay from collapse to defibrillation among patients found in ventricular fibrillation (VF). Survival to 30 days after an OHCA is still unacceptably low in Sweden, 11% [6,7]. The dissemination and systematic implementation of AEDs, in addition to training people in CPR with AEDs, can reduce the delay from collapse to on-site defibrilla- tion by laypersons and thereby save lives [5,8]. When public access defibrillation programs (PAD) are implemented and patients are

* Corresponding author.

E-mail address: [email protected] (A. Claesson).

defibrillated within 3 min after collapse, about 70% can survive [8,9,10]. National PAD training programs are desirable and AEDs available for public use should be registered and displayed in registries at national level [11].

The American Heart Association (AHA) and the European Resuscita- tion Council (ERC) recommend the placement of AEDs in public high- risk locations where at least one cardiac arrest occurs every second year [1]. The poor compliance with this recommendation to support res- idential OHCA is compensated for to some degree by PAD programs aimed at professional first responders (FR), such as fire departments and police authorities [1,12]. AEDs placed in appropriate FR vehicles support both public and residential OHCAs, are able to shorten the time to defibrillation and increase survival [13,14,15].

Nordberg et al. have previously shown that the introduction of dual dispatch systems using FR reduced the delay from patient collapse to AED arrival in both rural and urban areas, although 30-day survival was higher in urban areas [16]. In Sweden, an estimated 35,000 AEDs are sold, whereof about 16,500 are registered in the Swedish national AED register (SAEDR) [6].

http://dx.doi.org/10.1016/j.ajem.2017.02.030

0735-6757/(C) 2017

ethical aspects“>The region of western Sweden, with Gothenburg as the main urban area, has a population of 1.6 million individuals, with an area of 25,247 km² and a coverage of 10 AEDs/1000 inhabitants [6]. This region has long been active in the initiation of public training programs focus- ing on resuscitation and basic life support, which subsequently expand- ed nationally from 1983. More than 500,000 people in the region are trained in CPR. Dual dispatch has emerged over time using FR, primarily with fire departments but also with some police districts. Engdahl et al. identified places in the region suitable for PADs at an early stage, based on OHCA data between 1994 and 2003. At that time, 17% of all OHCAs occurred in locations suitable for PADs [17].

The aim of this study was to describe the use of AEDs before the arrival of EMS personnel, its impact on survival and changes over time during an eight-year period. We hypothesize that there was an increase in the use of AEDs before the arrival of the EMS over time, resulting in an increase in 30-day survival, and that on-site defibrillation was associated with improved survival as compared with the use of an AED by FR.

Material and methods

Eligibility criteria

The primary outcome was survival to 30 days. All cases reported to the Swedish Register for Cardiopulmonary Resuscitation (SRCR) suffer- ing an OHCA in the region of western Sweden between 2008 and 2015 in which CPR was started were eligible for inclusion. Patients with OHCAs witnessed primarily by the EMS personnel were excluded, see flowchart, Fig. 1. During the study period, dual dispatch with first re- sponders, such as deploying the fire department and police authorities, in suspected OHCAs was gradually increasing.

To make sure that all cases were included in the study, data from the SRCR were compared with local EMS registers and, when necessary, data were incorporated retrospectively. Moreover, additional follow- up interviews were performed with AED owners to identify cases with defibrillation prior to the arrival of FR and the EMS.

Swedish register for cardiopulmonary resuscitation

All cases of OHCA in which CPR is initiated are reported to the SRCR, founded in 1990 [6]. In 2007, a web-based protocol became available and, since 2011, almost 100% of the EMS organizations contribute data. Every year, a detailed follow-up is made by scanning EMS medical records to find missing cases.

Dispatch of FR and EMS personnel

The EMS in Sweden is based on a two-tier system with registered nurses and paramedics providing Advanced life support . The EMS coverage in the region of western Sweden fluctuates on a daily basis, but it comprises some 80 ambulance units and one helicopter EMS unit. The dispatch of FR units in the region is primarily performed within the fire department using firefighters trained in first aid and prehospital intermediate life support, including the use of AEDs, oxygen and

facemasks.

Statistical analysis

The results are expressed as the mean, standard deviation, median and percentages, while delays are presented as the median. In the com- parison of dichotomous variables between groups, Fisher’s exact test was used. In the evaluation of continuous variables between groups, as well as changes in proportions over time within the same group, Wilcoxon’s two-sample test was used. In the multivariate analysis, a multiple regression analysis was used. A p-value of b 0.05 was regarded as significant.

Ethical aspects

Ethical approval was given by the regional ethical review board in Gothenburg (#242-11). All survivors were informed about their inclu- sion in the study.

Fig. 1. Flowchart of included cases with 30-day survival depending on type of defibrillation.

Results

In overall terms, 6675 patients were reported to have had an OHCA in the region of western Sweden between 2008 and 2015, with 16%

Table 2

Characteristics and outcome in ventricular fibrillation to defibrillation before arrival of EMS.

Defibrillation before arrival of EMS

witnessed by the EMS personnel and 24% of the patients found in VF (Table 1). Bystander CPR was initiated in 68% of all cases and the OHCA had a presumed cardiac or medical cause in 62% and 89% respec- tively. Overall 30-day survival was 10%, for a total of 930 cases found in a shockable rhythm and defibrillated by the EMS personnel. The median delay from collapse to defibrillation was 14 min and the overall 30- day survival among patients found in VF was 24%. Baseline characteris- tics were generally similar as compared to data from Sweden at national level (Table 1).

Defibrillation prior to EMS arrival

CPR before arrival of EMS (%) (0, 0)

Yes No p

	N = 162	N = 930
Age (years); mean +- SD (2, 34a) 65.0 +- 14.8		66.9 +- 15.1	0.08
Sex (women) (%) (0, 0) 18.0		21.9	0.24
Witnessed status (0, 0) Bystander witnessed 93.5		83.0	b0.0001
Place (%) (0, 0) At home 31.1		56.6	b0.0001
Yes 100.0		73.5	b0.0001
Etiology (%) (24, 58)
Medial	98.5	97.0	0.41
Cardiac	85.4	81.6	0.34
Delay (median, min)
Collapse - call (30, 143)	2.0	2.0	0.99
Collapse - start of CPR (22, 65)	1.0	2.0	b0.0001
Collapse - defibrillation (34, 53)	11.0	14.0	b0.0001
Call for EMS - arrival of EMS (3, 18)	13.0	8.0	b0.0001
Survival 30 days (%) (8, 33)
Yes	46.4	22.6	b0.0001
CPC score among survivors (%) (24, 49)			0.22
1	80.4	73.0
2	17.4	15.8
3	2.2	9.9
4	0	1.3

A total of 162 patients (15%) of all cases found in VF were defibrillated before the arrival of the EMS, 46% with a public AED on site and 54% by FR (Table 2).

The median delay between collapse and defibrillation was shorter among patients who were defibrillated before the arrival of the EMS personnel, 11 vs 14 min for EMS (p b 0.001). Consequently, 30-day survival was higher in this group as compared with patients who were defibrillated by the EMS personnel; 46% vs 23% (p b 0.001).

On-site defibrillation versus first responder defibrillation

A total of 74 patients were defibrillated with on-site AEDs. They differed from defibrillation by FR in the following way: they were younger, with a mean age of 61 (SD 15.4) vs 68 (SD 13.1, p b 0.004) years, occurred less frequently at home (1.4% vs 57%, p b 0.001), had a shorter time from collapse to defibrillation, 6.5 vs 14 min (p b 0.001), and higher 30-day survival, 68% vs 29% (p b 0.001) re- spectively (Table 3).

Table 1

Out of hospital cardiac arrest in western Sweden vs Sweden 2008-2015.

	Western Sweden N = 6675	Sweden N = 30 276	p
Age (years); mean +- SD (190,1055a)	67.6 +- 17.8	67.9	0.24
		+- 19.0
Sex (women) (%) (0,60) Witnessed status (313, 1230)	33.9	32.6	0.03

Crew witnessed 16.1 14.8 0.008

Bystander witnessed 53.1 51.6 0.03

^a Numbers within brackets represent missing data.

Thirty-day survival

As shown in Fig. 2, there was an overall increase in the proportion of cases that were defibrillated before the arrival of the EMS over time; 5% in 2008 and 20% in 2015 (p <= 0.001).

There was a change in the overall 30-day survival among patients found in VF, not witnessed by the EMS personnel, from 22% in 2008 to 28% in 2015 (p = 0.04) (Fig. 3). The highest 30-day survival was found in the on-site defibrillation cohort, 68%, as compared to FR defibrillation, 29%, and 23% for EMS defibrillation respectively (p <= 0.001). The adjusted odds ratio (OR) for on-site defibrillation versus dispatched defibrillation was 2.45 (95% CI: 1.02-5.95)

(Table 4).

Table 3

Characteristics among patients found in ventricular fibrillation in relation to type of defibrillation.

Non witnessed 30.4 33.2 b 0.0001

Place (%) (0, 42)

Type of defibrillation p?

At home

CPR before arrival of EMS (%) (22, 167) Yes

69.1	67.5	0.01
67.9	66.9	0.19

On site N = 74

By

firemen/police N = 88

By EMS

crew

N = 930

Initial rhythm (340, 1532)

Ventricular fibrillation Etiology (%) (12, 450)

24.0	23.7	0.71	Age (years; mean +- SD)	61.3	68.1 +- 13.1	66.9	0.004
				+- 15.4		+- 15.1
88.6	89.5	0.034	Sex (women) (%)	18.9	18.2	21.8	1.06
61.6	63.4	0.009	Place (%)

Medial Cardiac

Delay (median, min) At home 1.4 56.8 56.6 b0.0001

Collapse - call for EMS (N = 2358, N = 10 861)	2.0	2.0	0.02b	Etiology (%) Medical	98.3	98.8	97.0	1.00
Collapse - start of CPR (N = 3854, N = 16 525)	1.0	2.0	b 0.0001	Cardiac Delay (median; min)	86.2	84.0	81.5	0.81
Collapse - defibrillation 12.0		11.0	0.05	Collapse - call	2.0	2.0	2.0	0.28
(N = 1125, N = 4690)				Collapse - start of CPR	0	1.0	2.0	0.0005
Call for EMS - arrival of EMS 10.0		9.0	b 0.0001	Collapse - defibrillation	6.5	14.0	14.0	b0.0001
(N = 6506, N = 23 580) Survival 30 days (%) (142, 543)				Call for EMS - arrival of EMS	10.0	16.0	8.0	b0.0001

Yes 10.0 10.4 0.37

^a Numbers within brackets represent missing data.

^b Mean value for western Sweden: 2.76 vs 2.86 for Sweden as a whole.

Survived to 30 days (%)

Yes 68.1 28.6 22.6 b0.0001

* p-Value refers to a comparison between defibrillation on site and by firemen/police.

Fig. 2. Proportion of patients who were defibrillated before the arrival of the EMS.

3.2.1. CPC score among survivors

The 30-day survival rate in patients found in VF was compared be- tween those defibrillated before vs. on the arrival of the EMS. In the for- mer group, the proportion of survivors with CPC 1 or 2 was 98%, versus 89% in the latter group (p = 0.22), see Table 2.

Discussion

The most important finding in this study was that a strategy of in- creasing the use of AED before the arrival of the EMS in OHCA was asso- ciated with an increase in survival among patients found in VF. The second most important finding was that, when an on-site AED was used, more than two thirds of the patients survived to 30 days. Finally, among patients who survived after 30 days, 98% had an initial CPC score that indicated relatively good cerebral function.

In overall terms, during this eight-year period, defibrillation had taken place before the arrival of EMS units in 15% of patients found in VF. This corresponds to about 1.5 cases a month. About half these cases were defibrillated with on-site AEDs and, in this cohort, survival to one month was the highest (68%).

In Amsterdam and surrounding areas, it was recently shown that the use of both on-site and dispatched AEDs increased between 2006 and

2012 and the use of AEDs almost tripled from 21% to 59% in VF cases with a presumed cardiac etiology [9]. The nationwide dissemination of public AEDs results in earlier defibrillation [19] and our findings from western Sweden support these data, with the potential for more exten- sive improvement. The impressive Dutch data are inspiring and guide the way to the future. The ERC guidelines from 2015 regarding public AEDs do not differ much from previous guidelines. In fact, it appears that what is needed is a societal implementation of the guidelines with the emphasis on public awareness to increase AED use.

Our finding of a survival rate of 68% among patients who were defibrillated with an on-site AED is important and similar to previous reports by Valenzuela et al. and Ringh et al. [3,8] describing survival rates of 70% if patients are defibrillated within 3 min after collapse. In our study, the median delay to on-site defibrillation was somewhat lon- ger (6 min), but the survival rate was similar. Interestingly, the dispatch of FR did not generate a decrease in the delay from collapse to defibril- lation or a much higher survival rate compared with cases defibrillated by the EMS team. However, these cases were similar to patients defibrillated by the EMS, with a high proportion of responses to residen- tial homes. Most importantly, the estimated cerebral function according to the CPC score was good in most cases, regardless of whether defibril- lation took place before or after the arrival of the EMS.

Fig. 3. Overall survival to 30 days in 2008-2015.

Table 4 Factors associated with 30 day survival among patients who were defibrillated before EMS arrival (N = 153).

Thirty-day survival was highest when an AED was used on site before the arrival of the EMS.

Unadjusted Adjusted

OR 95% CI OR 95% CI

Age (years) 0.97 0.94-0.99 0.98 0.96-1.01

Place of OHCA (outside home) (%) 5.81 2.70-13.47 2.84 1.05-7.63

Conflict of interest

None of the authors has any conflict of interest to declare.

Type of defibrillation (on site versus dispatched)

Delay from call for until arrival of EMS (logarithmized)

OR = odds ratio, CI = confidence interval.

5.34 2.71-10.87 2.45 1.02-5.90

0.35 0.18-0.62 0.59 0.31-1.14

Acknowledgements

We wish to acknowledge the EMS services, first responders and bystanders contributing to survival from OHCA within the western parts of Sweden during this period and in the following period.

One novel way of increasing the community response to OHCA via on-site and semi-onsite defibrillation is the recruitment of nearby by- standers using mobile phone technologies and text messaging to the site of an OHCA [18,20,21]. Dispatcher guidance via the implementation of AED registries in Emergency Medical Dispatch centers (EMDC) is an emerging way of bringing an AED to OHCA sites at an early stage and be- fore the arrival of the EMS personnel [22,23].

On-site defibrillation is also cost effective, as shown by Berdowski et al. These patients had an overall lower cost due to a shorter stay in the intensive care unit (ICU) [24].

Although dramatic regional differences in survival rates have been reported by Nichol et al. in a US data set, these findings are relatively old and may have changed [25]. This study using recent data with changes over time confirms a continued high survival rate similar to that from the Stockholm region and the Netherlands [8,9]. This is impor- tant knowledge for future potential of implementing AED registers in dispatch centers and for mobile app positioning systems such as SMS- lifesaving within the community [20].

The extension of PAD programs is needed in the future and AEDs need to be visualized and used through various technological solutions, such as national training programs, commercial text messaging, mobile applica- tions and referral from dispatch centers. More effort should be put into facilitating public awareness and motivation in the community to in- crease the use of on-site AEDs, thereby improving survival from OHCA.

Limitations

Information was missing for almost all the variables that were evaluated.

The external validity of our findings could be questioned, as the study took place in a specific part of Sweden with a specific geography. However, in terms of survival, our data are well in line with what has previously been reported in Europe [26]. The region of western Sweden also constitutes 17% of the Swedish population, which can be assumed to increase the representativeness of the sample and thereby strengthen the validity of the results and the ability to generalize them to national conditions.

In terms of survival, it is possible to argue against the comparison be- tween on-site AEDs and AEDs used by FRs who were dispatched, as, in the former group, almost all OHCAs take place in public or other places outside the patient’s home. These cases have previously been reported to have the best outcome [27]. There has been a slight increase in reporting to SRCR (n = 712 cases in 2008 to n = 904 in 2015) over the years and a small decrease in usage of targeted temperature man- agement (TTM) in-hospital (from 36% to 32%), we are unaware of how these small changes have affected outcome.

Conclusion

There was an increase over time in the use of AEDs before the arrival of the EMS. This development was associated with an increased rate of 30-day survival among patients found in ventricular fibrillation.

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