Impact of dual dispatch system implementation on response times and survival outcomes in out-of-hospital cardiac arrest in rural areas

2.1 Setting

This study took place in the northeastern part of Slovenia. The study region included surrounding catchment rural areas with several smaller and bigger villages of the following EMS: Maribor, Ptuj, Velenje and Koroška region with the population of 138,281 covering 1504.6 km² and average population density of 91.9 people/km². In this area, 63 local fire stations are equipped with AEDs.

2.2 Emergency medical services (EMS)

The EMS in Slovenia is provided by the Community healthcare centers with EMS stations located in the urban areas. The catchment area of a single EMS expands over several surrounding municipalities and thus the EMS provides its service not only in the urban/suburban but also in the rural areas with response times up to 40 min. When a cardiac arrest is suspected, an ambulance with two paramedics and an emergency physician on board is dispatched.

2.3 First responders

From 2014 first responders (local voluntary firefighters) have been organized in the rural areas with the EMS response times of more than 10 min. Median response time of EMS included in the study is 8 min in the urban/suburban areas. According to the Rules on Emergency Medical Service published in Official Journal of the Republic of Slovenia all first responders have to undergo a 10-hour training to gain the following knowledge and skills in basic life support (BLS): adult and children CPR with the use of an AED according to the European Resuscitation Council (ERC) guidelines, foreign body airway obstruction and control of the major isolated traumatic external bleeding. Initially, the ERC guidelines from 2010 were used for the training [23]. In the beginning of 2016, the training was adapted to the 2015 guidelines [24]. The algorithms of the AED were changed accordingly. After the training, the participants have to pass a written and a practical exam to obtain the first responder license. All first responders have to renew their license annually.

2.4 Dual dispatch

In Slovenia, Regional Emergency Notification Center receives all 112-emergency calls. In case of a medical emergency, the emergency call is forwarded to the Medical dispatch center. In cases of suspected cardiac arrests, the Medical dispatch center alerts the nearest available ambulance (EMS) with emergency physician on board first and then, as soon as possible, dispatches the closest available fire brigade with organized local first responders via the Regional Emergency Notification Center. The fire brigade dispatch should happen simultaneously with the EMS dispatch. The first responders to arrive at the scene are responsible for performing medical assessment. If the patient is unresponsive and not breathing, CPR is initiated and the AED is attached. When the EMS crew arrives, they take over the responsibility for the treatment, but the first responders are included in ongoing resuscitation as additional help.

2.5 Study design

This is a retrospective observational cohort study of the prospective gathered data in regions where a dual dispatch of first responders was implemented (intervention group). Enrollment of the patients in the intervention group depended on the time of the first responder implementation in each studied region. In EMS Maribor and EMS Koroška region the first responder system had been stepwise organized since May 2014 and was fully implemented in January 2015. Within the Northeastern Slovenia the system was incrementally rolled out to the other included regions with complete coverage from December 2017. Historical control group was based on all OHCAs occurring in these regions before the implementation of first responders (EMS response only). Comparison of all OHCA victims for an equivalent time period in both groups was made (see Appendix Fig. 2).

EMS protocols designed according to the Utstein style reporting for OHCA, first responder intervention reports, dispatch protocols of the Medical dispatch center and hospital medical reports for the study period were analyzed. Calculations of times and intervals were based on the above-mentioned reports.

2.6 Study participants

Eligible patients were all EMS resuscitated OHCAs in the rural areas included in the study (independent of witnessed status, cardiac rhythm and previous morbidity). The exclusion criteria were: age ≤18 years, EMS crew-witnessed OHCAs, in-hospital arrests, patients with obvious signs of death, people with existing Do Not Attempt Resuscitation (DNAR) orders and patients where no CPR was initiated by the EMS.

2.7 Endpoints

The primary endpoints were: (1) number of OHCAs with the return of spontaneous circulation (ROSC), (2) 30-day survival and (3) neurological outcome. Secondary endpoints were: (1) first responder response times, (2) proportion of patients admitted alive to hospital and (3) proportion of patients with VF/VT as initial rhythm.

2.8 Statistical analyses

Baseline characteristics of the sample are presented with frequencies (means, standard deviations, number, and percentages). Comparisons between intervention and historical groups were analyzed with t-tests for age and Chi squared test for categorical data. Median time intervals and survival between groups were compared with Mann-Whitney U test due to non-normal distribution. Multivariate logistic regression was used to control for confounding factors affecting ROSC between the intervention and the historical group. Following variables suggested by previous studies [11, 12, 14] were added in a multivariable model: intervention (dual dispatch vs historical controls), age: (≤67 years (median) vs ≥68 years), gender (female vs male), witnessed status (witnessed vs non-witnessed), bystander CPR (yes vs no), first rhythm (shockable vs non-shockable), etiology (cardiac vs other). Correlation matrix was checked for collinearity which was considered significant if correlations were greater than 0.80 (which was not the case with any of the chosen variables). Associations are presented as odds ratios (ORs) with 95% confidence intervals (CIs). Results were regarded significant if a two-tailed test yielded a p-value equal to or less than 0.05. SPSS software (version 25, SPSS Inc., Chicago, IL, USA) was used for statistical analysis.

4.1 Survival

Percentage of OHCA patients with initial shockable rhythm did not differ significantly between compared groups in the present study and was similar in other studies [13, 14, 26]. Shorter first responder response times lead to reduced time interval from call to first shock, especially in the group of patients with ROSC. Shorter time intervals to first shock in the two patients that survived without neurological sequelae in the historical controls were resuscitated by bystanders, who were incidentally a health worker and a local firefighter, who was not involved in an organized first responder system and hence stand out from the rest of the population in this study group. Furthermore, a higher number of shocks was delivered by first responders before arrival of EMS. These findings are supported by observations from several studies which also reported that shorter time interval from collapse to initial rhythm analysis more likely resulted in shockable initial rhythm thus increasing chances of ROSC [20, 22, 27]. Unfortunately, we did not observe a statistically significant increase in ROSC, admission to hospital and 30-day survival between compared groups although the hospital admission and 30-day survival rate were similar to other studies [12, 14, 18]. Increased survival to hospital admission and 30-day survival were described in metropolitan/suburban areas with dual dispatch system [11, 14, 19]. On the other hand, a twofold increase in favourable neurological outcome in patients with OHCA was found in our study but it did not reach statistical significance. Saner et al. [13] reported about 18 patients with favourable neurological outcome in OHCA patients resuscitated by first responders. These observations could be due to the fact that only patients with shockable rhythm were included in that study, longer time period of the study and shorter response times of the firefighters which could contribute to better survival outcome. Despite shorter response times and the fact, that dual dispatch of firefighters provides more skilled people at the scene, we failed to observe increase in ROSC after first responder implementation. This finding is similar to conclusions from Nordberg et al. [12] who also have not found increased survival rates of the OHCA victims after implementation of the dual dispatch with first responders in the rural area of the greater Stockholm area with the population density of <250/km². Observations from our study could be due to several factors. One might be that there were more resuscitation attempts in unwitnessed OHCAs as well as in patients of advanced age, both having poorer prognosis [25, 28]. Delayed advanced life support performed by EMS crew in rural areas also contributes to unfavourable outcome. Nordberg et al. [12] also suggest there could be a breakpoint, after which further reduction in the time interval is of less importance. This observation is supported by survival models where each minute of delay to defibrillate shockable rhythm reduces the probability of survival by 10% [5, 17, 20].

4.2 Time intervals

Response times of local first responders are significantly shorter compared to EMS response times (8 min vs 12 min, respectively). Similar first responder response times were also reported by other studies [12, 15, 18, 25]. Voluntary firefighters trained as first responders mostly reside in close proximity to the local fire station in the centre of the rural village. After activation, first responders on the way to the OHCA victim usually make a quick stop at the fire station to collect the first aid equipment and an AED. On rare occasions, when a first responder lives closer to the location of the OHCA victim than to the fire station, he or she goes directly to the OHCA victim providing first aid and starts with BLS if necessary, waiting for other first responders to bring the first aid equipment. Such logistics results in shorter response times, which could be further reduced with more optimal dispatch activation. Voluntary firefighters in Slovenia are a part of protection, rescue and relief forces governed by the Administration of the Republic of Slovenia for Civil Protection and Disaster Relief. The request for first responder activation is transferred telephonically from Medical dispatch center via the Regional Emergency Notification Center, which then alerts first responders using a rescue mobile application. Consequently, prolonged activation time for first responders was observed in our study compared to Saner et al. [13] (3 min vs 30 sec, respectively). Dispatch delay eliminates much of the benefit of the shorter travel time of the first responder [19].

On the other hand, EMS response times were significantly prolonged with the median delay of 8 min after first responder arrival. Similarly, an increase in EMS response times in rural areas during the first responder project was observed by Moore et al. [25]. This could be due to the fact that more resuscitations were attempted in the remote rural areas with prolonged EMS response times and thus included in the study. Voluntary firefighters as local first responders are trained to perform BLS and AED protocol until arrival of the EMS team, which then takes over the resuscitation effort. Due to different professional backgrounds and limited training as first responders, they are not capable of making crucial decisions. Therefore, they attempt resuscitation of every victim with OHCA regardless of the victim’s underlying conditions or whether the collapse was witnessed. Thus, higher numbers of all as well as unwitnessed resuscitations in the intervention group were observed similar to Nordberg et al. [12]. In very few cases, first responders withheld resuscitation attempts due to obvious signs of death (rigor mortis) or in cases where the patient’s DNAR order was well known. All these decisions were made after telephone consultation with the on-coming emergency physician. In the study period before the implementation of first responders, EMS arrival times in remote rural areas were prolonged and thus an emergency physician may have recognized resuscitation attempts as futile on arrival. The other reason for prolonged EMS response times could also be less extreme and safer ambulance driving, because when the EMS team is informed that the first responders are activated and on scene, they rely on them to provide BLS and use an AED.

4.3 Suggestions

Based on observations from our study the following adjustments to further reduce time from call to arrival of first help and thus improve the survival of OHCA victims are suggested: implementation of a systematic telephone assistance for witnesses to perform chest compressions; immediate activation of the firefighters first responders (not after the EMS); consider an alarm to citizens as lay first responders on a large scale (e.g., via a phone application).

4.4 Limitations of the study

Our study has several limitations. First, it is a retrospective study of prospective gathered data which could lead to some bias. When using registry data, results have limitations arising from missing or incorrectly reported variables. Second, the study design makes drawing true conclusions about causality difficult. Third, due to the narrow inclusion criteria the study population is small. Fourth, during the study period the changes in pre- and in-hospital treatment guidelines may have influenced the outcome. Fifth, we did not examine the cost effectiveness of the intervention.