This was a quasi-experimental longitudinal prospective study, with assessments before, immediately after, and two and a half months after the intervention.

Students (n=1405) were recruited from the 10th, 11th and 12th grades at the Mem Martins High School in the municipality of Sintra (Figure 1). Of these, 540 students (38.43%) were excluded because they were not enrolled in the Physical Education discipline, 481 students (34.23%) in 19 classes because their schedule did not allow time to participate in the study, 21 (1.5%) who took part in the pre-test to validate the data collection instrument, and one student (0.07%) who refused to give informed consent for participation.

Figure 1.

Exclusion criteria used in the sampling process and distribution of the sample.

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Random sampling of the classes led to the selection of 155 students in seven classes in the 10th grade (11.03%), 120 students in six classes in the 11th grade (8.54%), and 104 students in five classes in the 12th grade (7.40%), for a total of 379 school children. In the first round, 34 students who failed to attend, eight who did not complete Item B after training, one who did not speak Portuguese, and one who was physically unable to perform chest compressions on the manikin, were excluded. In the second round 38 students were excluded due to failure to attend.

The experimental group was composed of teachers from the high school, while the control group consisted of health professionals, all of them nurses or physicians from Hospital Professor Doutor Fernando da Fonseca, Amadora (HFF). All instructors had taken the Basic Life Support and Automated External Defibrillator (BLS+AED) course certified by the American Heart Association and the Portuguese National Institute for Emergency Medicine (INEM) and the instructors’ course in “Aprende os 3C's – Salva uma vida” (Learn the Three Cs – Save a Life), a training program for instructors in schools (Appendix 1). The level of practical skills achieved was assessed by the instructors themselves under the supervision of the lead investigator of the study.

Field work for the study took up two class periods. It was performed in the school itself and was divided into two rounds. The first round took place in morning and afternoon periods between March 11 and 20, 2019, while the second round (reassessment) took place in the same class periods between May 27 and 31. Based on information provided by the school's Executive Board on the composition of the classes, a ratio of up to 15 students per instructor was assumed.

The instrument used to evaluate the effectiveness of the simulated practice (Appendix 2) consisted of four items:

Item A: sociodemographic characterization of the study sample;

Item B: assessment of the student's previous knowledge about CA as presented in the video (see below), to be filled in individually under the instructor's supervision, consisting of 10 questions with responses scored between 0 and 1011;

Item C: practical case in which students demonstrate specifically how to implement safety measures, identify a CA, call the emergency number (112) and communicate appropriately, and place their hands on the victim's chest (between 5 and 20 points for each section, for a maximum score of 100)12;

Item D: chest compressions on a manikin for 2 min, performed by students individually, supervised and recorded by the instructor. International guidelines recommend a rate of 100-120 compressions/min and a depth of approximately 5 cm. The compressions were counted manually with the help of a smartphone app. A Laerdal Mini Anne Plus® manikin13 was used.

The instrument was reviewed by two school teachers and seven students with similar characteristics to the study sample, who suggested changes to the text. Items B and C were validated by one physician and four nurses, all experts in emergency medicine and trainers on PCR courses (Appendix 3). A pre-test was carried out with 21 students in the 12th grade at the same school.

In the first round, all participants were given around 15 min to complete a test assessing their previous knowledge about CA (Items A and B), and then attended a training session in which they watched a 16-min video. The practical case was then applied (Items C and D), taking around 5 min for each participant. The participants then responded to another assessment of their knowledge with the same questions (Item B). In the second round two and a half months later, a reassessment took place (without watching the video) that included the practical case (Items C and D) and assessment of post-training knowledge retention (Item B). The entire course of the intervention is summarized in Figure 2.

Figure 2.

Course of the intervention.

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The costs of implementing and maintaining the training program were estimated based on data provided by Sintra Town Hall, the Resuscitation School of HFF, and current legislation. Information was collected on:

• (a)

  costs of certified training in BLS+AED for the experimental and control groups;

• (b)

  costs of training sessions delivered by the control group, since these took place outside normal working hours;

• (c)

  costs of initial preparation of school teachers and regular annual visits for quality control of the program. Costs of the training and initial preparation sessions were calculated on the basis of the standard rates used in the Resuscitation School for remuneration of instructors;

• (d)

  cost of acquiring the Laerdal Mini Anne Plus® manikins (2018 prices);

• (e)

  traveling expenses;

• (f)

  costs of online data storage on a cloud hosting service.

These costs were extrapolated to cover all students in the 10th, 11th and 12th grades at the school (n=1405).

A non-parametric median test was used to compare the medians of continuous variables in the experimental and control groups, in order to assess the quality of the randomization and to identify possible sources of bias. The chi-square test was used to compare categorical variables.

A general linear model was applied to determine whether the differences in effectiveness between the experimental and control groups were statistically significant, adjusting for variables with significant differences between the groups on univariate analysis. This adjustment was designed to avoid measurement bias when calculating the impact of the intervention arising from the fact that the characteristics of the adjustment were not necessarily similar between the two groups.

The significance level was taken to be 5% (p-value <0.05).

The study was authorized by the Clinical Research Unit and the Resuscitation School of HFF, the ethics committee of the NOVA Medical School of Universidade Nova, Lisbon, the Directorate-General for Education (case no. 0665400001), and the Executive Board of the school group in which the study took place. Informed consent was requested from parents or guardians and students were asked if they were willing to participate. All data collected were anonymized and consent was deemed to be passive, i.e. the consent form was filled and signed only in cases of refusal, with failure to respond being considered equivalent to consent.

In the calculation of effectiveness, multivariate analysis was used to adjust for dimensions in which significant differences had been observed in univariate analysis. Specific adjustments were made for school year, grades in the previous year, and the student's relationship with the school. A log-normal distribution was assumed for the three dependent variables, as the distributions had been shown to be non-normal.

Multivariate analysis showed that improvements in knowledge retention immediately after the training session and 2.5 months later (Item B) did not differ significantly between the experimental and control groups. The greater improvement in practical skills (Item C) observed in the experimental group was also confirmed but again without statistical significance. Finally, regarding chest compressions (Item D), there were greater improvements in the control group, although once more without statistical significance (Table 3).

Costs arising from the training program were lower in the experimental group than in the control group. The costs of implementing and maintaining the program, extrapolated for all students of the 10th, 11th and 12th grades in the following year, were 4043 and 862 euros, respectively, in the experimental group, and 8561 and 6430 euros in the control group.

If the program had been implemented as in the control group only, the costs extrapolated to the year of implementation would be 8561 euros, falling to 6430 euros in the following year.

The item with the greatest cost was the Aprende os 3C's series of training sessions (6000 euros), which would account for 70.1% of the total cost in the year of implementation and 93.3% in the following year.

If the program had been delivered as in the experimental group, the main costs in the year of implementation would have been (a) training the school teachers in BLS+AED and Aprende os 3C's, with 1113 euros (27.5% of the total cost) and 120 euros (3.0% of the total cost), respectively; (b) acquisition of the training manikins, with 1426 euros (35.3% of the total cost); and (c) initial preparation and quality audit of the session, a total of 1200 euros (29.7% of the total cost). However, in the following year, the quality audit of the session by itself would incur the highest cost, with 600 euros (69.6% of the total cost). Costs of implementation are higher than maintenance costs in both groups (Table 4).

On multivariate analysis, there were no statistically significant differences between the experimental and control groups with regard to knowledge retention (Item B), demonstration of practical skills (Item C), or performing chest compressions (Item D), either in the initial period or after 2.5 months or in the difference between the two periods. The multivariate analysis enabled adjustment of the comparison between groups for possible confounding factors, including bias due to differences in the characteristics of the two groups. In terms of magnitude of the effect, without adjustment there was an improvement in the practical skills of the experimental group, while gains were greater in the control group for knowledge retention and chest compressions.

The costs of the program were lower when it was delivered by the experimental group, with savings of 4500-5500 euros, depending on the need to acquire training resources or material in other years.

The main result is that when adjusted for differences between the groups, no differences in the effectiveness of the intervention were seen between health professionals and school teachers. This is to be expected regarding practical skills and chest compressions, since these are taught in part through the same video.11 Furthermore, the greater technical knowledge of the health professionals could be balanced by the closer relationship between the school teachers and their students, by their experience in transmitting knowledge, and by their greater ability to adapt their language for a young audience, especially when they have been trained in BSL+AED.14

Other points deserve mention with regard to effectiveness. For Item B, other studies have observed statistically significant improvements in knowledge retention before training, immediately after, and at two and four months,11,12 as we found in univariate analysis. There is a reference in the literature to a decline in knowledge retention after six months, although assessment of this variable was not within the scope of our study. Annual training sessions may lead to better results, as well as being easier to integrate into school curricula and improving use of the school's resources.12

An unexpected result was the low effectiveness of training in frequency of chest compressions (Item D). International guidelines recommend a frequency of 100-120/min, with a depth of approximately 5 cm but not exceeding 6 cm, allowing full chest recoil after each compression, maintaining an equal time between compression and recoil, and minimizing interruptions.15 However, around 70% of participants in the experimental group and 60% in the control group did not achieve the recommended rate of chest compressions (100-120/min). We recognize the need to improve training in this respect in future applications of the program.

According to a study by Lockey et al., the British Heart Foundation estimated the cost of implementing its Heartstart program to be 2100 GBP.16 This includes the cost of the training manikins, audiovisual educational aids, and the instructor who carries out the training sessions. Maintenance costs include those for replacing manikins and consumables, and instructor costs. Lockey et al. do not specify the type of instructor or number of students covered by the Heartstart program, or whether the training of instructors is certified. These variables may explain the lower costs they calculated compared to the results of our study.

Calculation of costs in the present study was based on estimates and retrospective analysis. Costs were extrapolated to the entire school, since all students in the 10th, 11th and 12th grades would be covered by the training. The highest cost was attributed to training sessions in the school when the program was delivered only by health professionals, in which case the sessions took place outside normal working hours. Payments for these sessions were calculated at the rate stipulated by the Resuscitation School for their instructors. If the sessions had taken place during normal working hours, payments would have been adjusted to the contracted price per hour for the instructor's professional category. However, this would entail these health professionals being unable to perform their usual duties during these hours. The hours of the school teachers, who delivered the training as part of their normal activity, were costed according to the contracted price per hour for their professional category. The training sessions took up two class periods as part of the core curriculum of the Physical Education discipline for 10th-year students, and so the teacher did not require additional time to prepare the lessons.

Other authors have compared conventional training techniques (with health professionals, school teachers, videos and manikins) with other low-cost training techniques such as foam dice, videos, and peer instruction by fellow students,17,18 but it would be difficult to compare their results with ours.