Study design and approval
This retrospective observational study presents data collected from a GPS-based system on the Danish Island of Langeland. Approval for this study was given by The Danish Data Protection Agency (Journal no. 17/32047) and Danish Patient Safety Authority under the administration of Danish Health Authority (no. 3-3013-2848/1, ref.LOSC) and the volunteers accepted during their registration in the project, that data was collected from their smartphones, stored on the server and used for research purposes. In Denmark, ethical approval is not needed for this kind of study.
The island of Langeland has a population of approximately 12,000 inhabitants, but during summertime approximately 260,000 tourists visit the holiday island. It is 52 km long and 11 km at its widest and is bridge connected to the mainland9. There are 5 larger villages, and the population is a typical island community, where most of the island’s inhabitants have lived most of their life on the island. Langeland has one ambulance and one paramedic vehicle and in case the ambulance is reserved for another duty, response times increase drastically as another ambulance needs to arrive from the city of Svendborg placed on the mainland 20–50 km away9. The island has 96 AEDs placed strategically with no more than 2 km between each of them.
A GPS-based system to activate CFRs was initiated in 2012 on Langeland. Each time an ambulance was dispatched to an emergency, the system identified the nine closest CFRs in a five km radius from the emergency site via GPS and notified them by an alarm sent to their smartphone. The CFRs could then choose to accept or decline the call. Based on the choices made, the system within 20 seconds identified the three closest CFRs and sent a map to the location of the emergency site and tasks. Two CFRs were dispatched directly to the emergency site, while the third was sent to pick up an automated external defibrillator (AED) before proceeding to the emergency site. These tasks are selected by the system based on the CFRs GPS location and nearest AED. After each activation, there was a possibility for a debriefing for the CFRs9,10.
Recruitment of lay responders
CFRs were recruited to the project through local advertisement and were mostly laypersons but included some off-duty healthcare providers. To become CFR certified, the CFRs needed to be at least 18 years of age and complete a 12-hour basic life support training course provided by Langeland AED Association. The CFRs were trained by ERC certified staff. Each CFR is manually approved by an administrator before being able to accept assignments in the system. To remain active as a CFR an annual 3-hour retraining course is required.
All medical emergency calls involving CFRs on Langeland in the time period from 21st of April 2012 to 31st of December 2017 were included. CFRs were excluded from analysis if they did not arrive on-site or if their data did not appear to be appropriate (arrived on-site > 2 hours after accepting the call).
The time for arrival at the emergency site was automatically logged by the GPS-based system. Time and date for when the system alerts the CFRs, the emergency site’s address and CFRs arrival time at the emergency site were collected from the project-server. Emergency service records were acquired and were used to correct any missing data as far as possible in the CFR information.
Definition of variables
CFR experience was measured as the number of times a CFR was activated and arrived to the emergency site, and was divided into the following groups based on milestones from the Langeland AED Association as the association gives rewards based on the categories: ≤10, 11–24, 25–49, 50–99, ≥ 100 calls accepted. We presumed these milestones to be applicable and good indicators for CFR experience. These groups were used to investigate the link between CFRs experience and response time; e.g. the response times of a CFR who was called out 34 times was placed in the category ≤ 10 calls the first 10 times he/she was called out, then placed in the category 11–24 calls for the next 14 calls, and finally placed in the category 25–49 for the last 10 calls. Response times were calculated using the time from alerting the CFRs to CFRs time of arrival at the emergency site.
Variables of interest
The median response time could be influenced by multiple variables and were therefore analysed by the effect of a CFR acquiring an AED on the way to the emergency site, the time of day and season. Time of day was categorised according to hours at work (7:00 to 15:00), spare time (15:00 to 23:00) and nighttime (23:00 to 7:00). The season was defined meteorologically as winter (December, January, February), spring (March, April, May), summer (June, July, August) and fall (September, October, November). As Rudkoebing is the biggest City on Langeland, we wanted to see if this had an impact compared to the rest of Langeland.
The data were analysed using Stata 16 and statistical significance was set to p = 0.05. To validate if data were normally distributed a Q-Q plot was used. Non-normally distributed outcomes were reported as median with interquartile ranges (IQR). Categorical data were described as absolute numbers and percentages. A Spearman’s rank-order correlation was used to assess if there was a monotonic relationship between experience and response times. To evaluate non-normally distributed outcomes, a Kruskal Wallis test was used if there were three or more unmatched groups and a Mann-Whitney U-test was used to test for statistically significant differences between two groups. A multiple regression analysis was used to analyse the relationship between CFR response times and the independent variables (experience, AED, year, time of day, season, Rudkoebing vs. the rest of Langeland).