Retention of Basic Life Support in Laypeople: Mastery Learning vs. Time-based Education

Abstract

Objective: To compare the effectiveness of a mastery learning (ML) versus a time-based (TB) BLS course for the acquisition and retention of BLS knowledge and skills in laypeople. Methods: After ethics approval, laypeople were randomized to a ML or TB BLS course based on the American Heart Association (AHA) Heartsaver course. In the ML group, subjects practiced and received feedback at six BLS stations until they reached a pre-determined level of performance. The TB group received a standard AHA six-station BLS course. All participants took the standard in-course BLS skills test at the end of their course. BLS skills and knowledge were tested using a high-fidelity scenario and knowledge questionnaire upon course completion (immediate post-test) and after four months (retention test). Video recorded scenarios were assessed by two blinded, independent raters using the AHA skills checklist. Results: Forty-three subjects were included in analysis (23ML;20TB). For primary outcome, subjects' performance did not change after four months, regardless of the teaching modality (TB from (median[IQR]) 8.0[6.125;8.375] to 8.5[5.625;9.0] vs. ML from 8.0[7.0;9.0] to 7.0[6.0;8.0], p = 0.12 for test phase, p = 0.21 for interaction between effect of teaching modality and test phase). For secondary outcomes, subjects acquired knowledge between pre- and immediate post-tests (p < 0.005), and partially retained the acquired knowledge up to four months (p < 0.005) despite a decrease between immediate post-test and retention test (p = 0.009), irrespectively of the group (p = 0.59) (TB from 63.3[48.3;73.3] to 93.3[81.7;100.0] and then 93.3[81.7;93.3] vs. ML from 60.0[46.7;66.7] to 93.3[80.0;100.0] and then 80.0[73.3;93.3]). Regardless of the group after 4 months, chest compression depth improved (TB from 39.0[35.0;46.0] to 48.5[40.25;58.0] vs. ML from 40.0[37.0;47.0] to 45.0[37.0;52.0]; p = 0.012), but not the rate (TB from 118.0[114.0;125.0] to 120.5[113.0;129.5] vs. ML from 119.0[113.0;130.0] to 123.0[102.0;132.0]; p = 0.70). All subjects passed the in-course BLS skills test. Pass/fail rates were poor in both groups at both the simulated immediate post-test (ML = 1/22;TB = 0/20; p = 0.35) and retention test (ML pass/fail = 1/22, TB pass/fail = 0/20; p = 0.35). The ML course was slightly longer than the TB course (108[94;117] min vs. 95[89;102] min; p = 0.003). Conclusions: There was no major benefit of a ML compared to a TB BLS course for the acquisition and four-month retention of knowledge or skills among laypeople.

Key words::

• education
• life support, basic cardiac
• patient simulation
• randomized controlled trial

Introduction

Approximately 6% of victims suffering from sudden out-of-hospital cardiac arrests survive to hospital discharge.¹ The time between cardiac arrest and delivery of cardiopulmonary resuscitation (CPR) is crucial to optimize patient outcomes.^2,3 Survival rates increase two-to-three fold when a bystander initiates CPR.^4–7 However, CPR is only delivered in approximately half of all out-of-hospital cardiac arrests.^2,8,9 Lay bystanders are more willing to perform CPR when they have Basic Life Support (BLS) training.^2,10 Yet, despite initial demonstration of competence after rigorous standardized BLS skills training, data from out-of-hospital arrests reveal that CPR delivered by lay bystanders is often suboptimal.^11–13 Poor skill retention after BLS training may be a contributing factor in the low rate of survival after cardiac arrest.^11,12,14,15

Various instructional designs have been tested to improve BLS skill acquisition and retention.¹⁶ Traditional BLS course layouts deliver a curriculum over a fixed time schedule regardless of the needs of individual learners. This fixed design has been postulated as a contributing factor to the poor retention of BLS skills among laypeople.¹⁷ Alternatively, a mastery learning (ML) approach is competency-based and aims to maximize individual learning opportunities while reducing variation in learning outcome.^16,18–21 Learners acquire essential knowledge and skills that are measured against set standards, with variable time allowed to reach the outcome.¹⁹ ML has been shown to be effective for improving learning outcomes in students from primary school through to university,^22,23 and is increasingly used for training medical professionals.^21,24–27 When compared to no intervention or other instructional designs (i.e., lecture format, or non-ML simulation),²⁴ ML has also been shown to translate into better patient care and outcomes.^21,25,27,28 While research shows that ML has facilitated the acquisition of clinical procedural skills in healthcare professionals,^24,25 few studies have examined skill retention.^27,28 Furthermore, the impact of ML on the retention of a complex clinical skill set like BLS for laypeople, that is, individuals without formal healthcare training, has yet to be investigated.

This study aimed to assess the acquisition and retention of BLS knowledge and skills among laypeople immediately after course completion and four months after a traditional time-based (TB) course compared to a ML based BLS course. We hypothesized that a ML BLS course would be more effective than a traditional TB BLS course for the acquisition and retention of BLS knowledge and skills in laypeople.

Methods

Study Design

The study was conducted as single blinded (i.e., raters were blinded to group allocation), prospective, quasi-randomized, controlled trial.

Human Subject Ethical Committee Review

This trial was approved by the Ottawa Health Science Network Research Ethics Board (OHSN-REB) at the Ottawa Hospital Research Institute, Ottawa, Canada (20120928-01H) and was registered on ClinicalTrials.gov (NCT02059395). This study is reported in adherence to the Consolidated Standards of Reporting Trials (CONSORT) standards²⁹ and the “Recommendations for Reporting Mastery Education Research in Medical Education” (ReMERM).²⁶

Population and Setting

Undergraduate university students without formal healthcare training (i.e., laypeople) were recruited from the Faculty of Science at the University of Ottawa, Canada. Students in all programs within the Faculty of Sciences were approached to participate except nursing students. Students who had participated in a formal BLS course prior to study enrollment were excluded. As an incentive, participants were given the choice between an American Heart Association (AHA) Heartsaver CPR AED Course Completion Card (BLS-A) or $100 for their participation. Recruitment was open from November 2013 to January 2014.

Protocol

After obtaining written informed consent, participants were randomly assigned to either the control group/time-based BLS course (TB) or the intervention group/mastery learning BLS course (ML) (Figure 1). In order to guarantee an equal number of participants per course, randomization was performed for each course date and not for each participant. Participants enrolled for a specific date on a first-come-first-serve basis and were not informed which course they would be allocated to. The type of course offered on each date was determined by opening a numbered, opaque envelope prior to the course start. Block randomization was performed using the Wichmann-Hill random number generator algorithm provided by www.randomization.com.

Figure 1. Study flow chart.

On the day of the BLS course, all participants completed a demographic questionnaire and a pre-course written knowledge test (knowledge pre-test). No pre-course simulation test was performed because, in our experience, BLS skill performance in laypeople with no previous training is consistently poor. However, we elected to administer a pre-course knowledge test because basic BLS knowledge may vary even with no previous training. Both groups then received a six-station BLS course based on the 2010 adult AHA Heartsaver course (adult CPR and automatic external defibrillator-AED).^30,31 The AHA course included training on six stations: (1) chest compressions, (2) mouth-to-mouth ventilation and mouth-to-mask ventilation, (3) AED use, (4) diagnosis of cardiac arrest and call for help, (5) single-rescuer BLS, and (6) adult choking. In both groups, AHA Heartsaver course material was used and the courses were guided using the official AHA Heartsaver course video. The instructor/learner ratio was intended to be 1:5 in both groups. Each participant practised on their own mannequin.

In the ML group, after AHA video instruction, each participant deliberately practised the respective skill until a predetermined level of mastery was achieved for each of the six stations. Levels of mastery were predefined using the learning goals for each AHA Heartsaver course station. At each station, a certified instructor completed an individualized skills assessment using a checklist and provided feedback. The formal ML checklist was created to reflect the learning goals as defined in the AHA Heartsaver instructor manual and focused on the skill related to each station (Appendix). Participants received individualized feedback on their performance after each assessment and could only proceed to the next station if they had achieved the predefined mastery level of the given station. Those who did not reach the target were given feedback and required to practice further and were repeatedly re-tested until mastery was reached. A maximum of eight hours was allowed for the learner of the ML group to complete the BLS course. If a participant did not fulfill the final mastery level after eight hours they were considered to have failed the mastery learning curriculum.

In the TB group, the same six stations were taught over a fixed period according to the AHA standard: 10 minutes of introduction followed by 90 minutes of actual course content, with additional time for feedback as necessary up to a maximum of 2 hours total. A certified instructor guided the video-based training following the specific regulations outlined in the AHA Heartsaver AED course DVD set. Concurrent individualized feedback was given according to trainee's needs, as is standard for this course. TB participants performed the skill required at each station for the recommended amount of time and received feedback from the instructor as needed; however, TB participants were not formally evaluated using a checklist, and they moved on to the next station when the maximum amount of time allowed for each station elapsed, without any minimum required performance level to achieve at the end of each station.

As part of the AHA Heartsaver course requirements, all participants in both study arms took the in-course BLS skills test at the end of their initial BLS course to receive a certificate of course completion. The in-course BLS skills test was conducted on the low-fidelity practice mannequins used for the training and assessed in real time by the instructor, therefore was unblinded. Each participant was required to apply the information learned during the BLS course in the appropriate order. The number of attempts required to complete the in-course BLS course skills test were recorded by the instructor at the time of the course. The duration of all BLS training sessions were recorded from the beginning of teaching until all participants had completed the in-course BLS skills test.

Upon completion of the BLS course, including the in-course BLS skills test, participants from both groups completed a written knowledge test (knowledge post-test) prior to participating in a high-fidelity simulated scenario (immediate post-test). All simulated tests were 5-minute high-fidelity simulated cardiac arrest scenarios (sudden collapse of a passer-by) using the SimMan 3G® (Laerdal Medical Corporation, Stavanger, Norway). During the high-fidelity simulation test, each participant was required to perform immediate single rescuer BLS. A confederate was available to help and was available to phone for help and bring an AED upon request. Participants were scheduled for a retention date and were dismissed after the simulation was complete.

Participants returned to the simulation center four months after their original BLS training to participate in their retention tests. Then participants completed the written knowledge test (knowledge retention-test) and subsequently participated in a high-fidelity simulated scenario (same as previously description). All simulation scenarios (immediate post-tests and retention tests) were videotaped for later assessment. All participants were also asked whether or not they had received any additional BLS training or any practical experience with BLS skills since the initial study date.

Performance Measures

AHA checklist

The official AHA Heartsaver adult CPR AED Skills Sheet checklist for single-rescuer BLS was used to capture participants' skills for single-rescuer BLS and defibrillation with an AED. Immediate post-test and retention test video performance were evaluated using the AHA Skills Sheet by two independent expert raters, blinded to group assignment and test phase (post-test and retention test) as well as to the hypothesis. Each rater scored video performances independently from each other. We elected to measure the overall agreement between the two video raters by calculating the intraclass correlation coefficient (ICC). If the ICC had shown good or excellent agreement (>0.60), then we elected to use the mean score as the expert score for analysis. If the ICC had shown poor or fair agreement (<0.59), then we had elected to have the two raters to discuss their disagreements and reach consensus. The immediate post tests and retention tests simulated scenarios had the confederate research assistant to call for help before the participant. This prevented the participants from having a chance to score on step 3 (“yells for help”) of the 12 step AHA Heartsaver checklist. We therefore excluded this step from our checklist, and scored out of a total of 11 points instead. Pass/fail scores were calculated using a passing score when the participant achieved 100% on the AHA checklist of skills (11/11).

CPR quality indicators

Data for chest compression performance during the high-fidelity simulated scenarios (immediate post-test and retention test) were measured using a SimMan 3G® (Laerdal Medical Corporation, Stavanger, Norway). SimMan 3G® measures depth and rate of chest wall movement during each compression. Compression depth was measured in millimeters and compression rate was measured in compressions per minute.

AHA knowledge questionnaire

A written single best choice theoretical knowledge test based on the questionnaire used in the AHA Heartsaver course was used to measure BLS knowledge. The same knowledge test was used in all three phases of the study: before training (knowledge pre-test), immediately after training (knowledge post-test) and at four months (knowledge retention test).

Outcomes

The primary outcome was skill retention from the immediate post-test to four month retention test, as measured by the total score achieved on the AHA Heartsaver CPR AED Skills Sheet checklist.

Secondary outcomes included:

•	Course duration, as assessed using the difference between BLS training session lengths.
•	BLS knowledge acquisition and retention at pre-test, immediate post-test and retention test, as measured by the knowledge test questionnaire based on AHA Heartsaver course.
•	BLS skill retention from the immediate post-test to four month retention test, as measured by the quality of chest compression performance (compression depth and rate).
•	Pass rates for BLS skill tests, captured by the (i) number of attempts to pass BLS in-course skills test; (ii) overall AHA checklist score (a score of 11/11 was considered a pass); and (iii) completion of each AHA checklist item for all simulated tests.

Statistical Analysis

Statistical analysis was performed using SPSS 17.0 (SPSS Inc., Chicago, IL). Agreement between video raters was measured by intra-class correlation coefficient. Mann-Whitney U test or chi-squared were used to analyse categorical data. A two-way repeated-measure analysis of variance (ANOVA) was used to test the difference in skill (primary outcome) and knowledge (secondary outcome) scores between the two groups over time. A two-way repeated measures ANOVA is considered to be a robust test against the normality assumption with small effect on the type I error rate.³² For the primary outcome, the total AHA checklist score was treated as the dependent variable. For the secondary outcome assessing knowledge, the total written knowledge tests scores were treated as the dependent variable. For all two-way repeated-measure ANOVA tests the independent variable was group allocation (ML versus TB) as the between-participants variable and test phase (immediate post-test versus retention test) as the within participants measure. A p value of < 0.05 was considered to be statistically significant. Outcomes are reported using Median [First quartile; Third quartile] (IQR) unless sated otherwise.

Sample size was determined a priori using previous data from Li et al., which showed that pre-training evaluation and feedback improved BLS performance (82.9 ± 3.2%) compared to a control group (63.9 ± 13.4%) in undergraduate medical students without previous BLS training.³³ Therefore, conservatively a 15% improvement in the skills score at retention test was expected.³³ Assuming a type I error of 0.05 and power of 0.8, a minimal sample size of 18 in each group was needed. Considering possible participants lost at retention test, we intended to recruit 50 participants in total.

Results

Demographics

Forty-nine participants were randomized to seven ML and five TB teaching sessions (27 ML; 22 TB), held between November 2013 and January 2014. Fourteen study dates were booked (7ML; 7 TB); however two dates were cancelled due to participant unavailability. Participants who cancelled were given the option of joining a session on a different day if possible. The median instructor to participant ratio was 1:4 [3.5;4] in the ML and 1:4 [4;5] in TB group. All participants completed the first day and the allocated AHA Heartsaver BLS course. Two participants in the ML group obtained additional BLS training between immediate post-test and retention test and were excluded, none practiced BLS on patients in the interval time. Three participants (one ML, two TB) did not participate in the retention phase and video data for one ML participant could not be retrieved after the trial due to a software issue (see Figure 1). These four participants were excluded from data analysis. Therefore, 43 participants (23 ML; 20 TB) were included in analysis. All included participants from both groups completed their retention test within a median of 105 [101;117] days and there was no difference in interval to retention between groups (TB 112 [104;117] vs. ML 101 [92;114], p = 0.07, Table 1). Demographic data are presented in Table 1^{Figure 2}. All participants of the ML instructional design group demonstrated proficiency with compressions at the first attempt, one participant required two attempts at ventilation, seven participants required two attempts at AED as well as for Diagnosis & Call for help, and eight participants required two attempts at one Helper BLS.

Table 1. Demographic data (n = 43); median [interquartile range] (IQR) or absolute frequency (relative frequency)

	Time Based	Mastery Learning
	(n = 20)	(n = 23)
Gender (female)	9 (45%)	13 (57%)
Age (years)	19.5 [18.0;21.0]	20.0 [18.75;21.0]
Time to retention (days)	112 [104;117]	101 [92;114]
Length of course (min)	95 [89;102]	108 [94;117]

Inter-Rater Reliability

The overall agreement between the two video raters using the AHA checklist was excellent (ICC = 0.89; p < 0.005).³⁴ Due to the agreement between expert raters, we elected to use the mean score as the expert score for analysis.

Primary Outcome

Skill Retention: The effect of test phase and teaching modality on the total AHA checklist score

A two-way repeated measures ANOVA revealed no effect of the test phase (between immediate post-test vs. retention test) and no interaction between the effect of teaching modality with respect to immediate post or retention test performance (TB from 8.0 [6.125;8.375] to 8.5 [5.625;9.0] vs. ML from 8.0 [7.0;9.0] to 7.0 [6.0;8.0], p = 0.12 for the test phase, and p = 0.21 for interaction between the effect of teaching modality and test phase) (Figure 2, Table 2). Therefore, participants did not decrease their performance after 4 months, regardless of the teaching modality.

Figure 2. Time Based BLS training versus Mastery Learning BLS training comparing mean pre-test and immediate post-test scores for total American Heart Association (AHA) Checklist score. Subjects' performance did not change after four months, regardless of the teaching modality (p = 0.12 for the test phase, and p = 0.21 for interaction between the effect of teaching modality and test phase).

Table 2. Group comparison for BLS skill test performance results

	Time Based median [IQR]	Mastery Learning median [IQR]
	(n = 20)	(n = 23)
Achieved AHA checklist points^*
Immediate post-test skill	8.0 [6.125;8.375]	8.0 [7.0;9.0]
Retention test skill	8.5 [5.625;9.0]	7.0 [6.0;8.0]
	Pass/Fail (n = 20)	Pass/Fail (n = 23)
Passing AHA Checklist Score^†
Immediate post-test skill	0 / 20	1 / 22
Retention-test skill	0 / 20	1 / 22
	Median [IQR] (n = 15)	Median [IQR] (n = 23)
CPR Quality
Immediate post-test compression depth	39.0 [35.0;46.0]	40.0 [37.0;47.0]
Retention-test compression depth	48.5 [40.25;58.0]	45.0 [37.0;52.0]
Immediate post-test compression rate	118.0 [114.0;125.0]	119.0 [113.0;130.0]
Retention-test compression rate	120.5 [113.0;129.5]	123.0 [102.0;132.0]

IQR: Interquartile Range.

^* Using 11 points of the American Heart Association (AHA) Heartsaver checklist; excluding item 3- yells for help.

^† A “pass” is a score of 11 out of 11 for the AHA Heartsaver checklist.

Secondary Outcomes (Table 2)

•	Course duration: Although not clinically relevant, participants in the time-based group finished the course significantly faster by 13 minutes than their colleagues in the mastery group (TB 95 [89;102] min vs. ML 108 [94;117] min, p = 0.003, Table 1). There were no participants who exceeded the maximum time of 8 hours allocated for the mastery learning based group.
•	Knowledge acquisition and retention: A two-way repeated measures ANOVA detected an effect of the test phase (between pre-test, immediate post-test and retention test) on knowledge acquisition and retention, but no interaction between the effect of teaching modality with respect to test phase (pre-test, immediate post-test, retention test) on knowledge score (TB from 63.3 [48.3;73.3] to 93.3 [81.7;100.0] and then 93.3 [81.7;93.3] vs. ML from 60.0 [46.7;66.7] to 93.3 [80.0;100.0] and then 80.0 [73.3;93.3], p < 0.005 for the test phase, and p = 0.59 for interaction between the effect of teaching modality and test phase) (Table 3). A two-way repeated measures ANOVA revealed that knowledge increased from pre-test to immediate post-test but was not influenced by group (TB from 63.3 [48.3;73.3] to 93.3 [81.7;100.0] vs. ML from 60.0 [46.7;66.7] to 93.3 [80.0;100.0], p < 0.005 for test phase and p = 0.61 for group); and increased from pre-test to retention test but was not influenced by group (TB from 63.3 [48.3;73.3] to 93.3 [81.7;93.3] vs. ML from 60.0 [46.7;66.7] to 80.0 [73.3;93.3], p < 0.005 for test phase and p = 0.81 for group). Knowledge decreased from immediate post-test to retention post-test but was not influenced by group (TB from 93.3 [81.7;100.0] to 93.3 [81.7;93.3] vs. ML from 93.3 [80.0;100.0] to 80.0 [73.3;93.3], p = 0.009 for test phase and p = 0.148 for group). Therefore, irrespective of the teaching modality to which they were exposed, participants acquired knowledge between pre- and immediate post-tests, partially retained the acquired knowledge up to 4 months despite a decrease between immediate post-test and retention test. Table 3. Written knowledge test performance results Knowledge Pre-test Knowledge Post-test Knowledge Retention (median[IQR])^* (median[IQR]^* Test (median[IQR]^* Time Based (n = 20) 63.3 [48.3;73.3] 93.3 [81.7;100.0] 93.3 [81.7;93.3] Mastery Learning (n = 23) 60.0 [46.7;66.7] 93.3 [80.0;100.0] 80.0 [73.3;93.3] *Percentage of correct answers on written knowledge test.
•	Chest compression retention performance: is captured in Table 2. SimMan 3G data for five TB participants could not be retrieved due to software problems that led to data loss (23 ML; 15 TB). A two-way repeated measures ANOVA revealed an effect of the test phase (between immediate post-test vs. retention test) on chest compression depth, but no interaction between the effect of teaching modality with respect to immediate post or retention test performance (TB from 39.0 [35.0;46.0] to 48.5 [40.25;58.0] vs. ML from 40.0 [37.0;47.0] to 45.0 [37.0;52.0], p = 0.012 for test phase and p = 0.25 for the interaction between the effect of teaching modality and test phase). Therefore, participants improved their chest compression depth performance after 4 months, regardless of the teaching modality. A similar two-way repeated measures ANOVA did not show any effect of the test phase (between immediate post-test vs retention test) on chest compression rate and no interaction between the effect of teaching modality with respect to immediate post or retention test performance (TB from 118.0 [114.0;125.0] to 120.5 [113.0;129.5] vs. ML from 119.0 [113.0;130.0] to 123.0 [102.0;132.0], p = 0.81 for interaction between the effect of teaching modality and p = 0.70 for test phase). Therefore, participants did not change their chest compression rate performance after 4 months, regardless of the teaching modality.Table 4
•	Pass rates for skill tests: Regardless of group allocation, all participants completed and passed the in-course BLS skill test (end of course BLS skill test before the immediate post-test, rated by the course instructor who was not blinded), and with a similar number of attempts (Median ML:1 ± 0 TB: 1 ± 0 p = 0.10). However, pass rates were poor in both groups at both the simulated immediate post-test (TB [pass/fail] 0/20 vs. ML 1/22, p = 0.35) and retention test (TB 0/20 vs. ML 1/22, p = 0.35); both assessed by blinded raters (Table 2). A breakdown of skill performance by checklist item by group is given in Table 4.

Discussion

This study investigated the relative effectiveness of a mastery learning BLS course compared to a traditional time-based BLS course. Contrary to our hypothesis, the results of this trial did not demonstrate superiority of the mastery learning course over the time-based course for the acquisition and retention of BLS knowledge and skills among laypeople. Our findings on laypeople are not consistent with the available literature on healthcare professionals that suggests that ML is more effective than TB training for skill retention.^27,28 While not clinically relevant, participants in the ML course took slightly more time than participants in the TB course, which is consistent with the literature.²⁴ Furthermore, all participants achieved similar skill and knowledge levels. Overall, we could not find a benefit to ML when compared to TB BLS teaching in laypeople.

Table 4. Single skill performance showing correctly performed skill

AHA Checklist	BLS Training	Immediate Post-test^*	Retention test^*
Item	Group	Pass (relative %)	Pass (relative %)
1. Verbalize that the scene is safe	Time Based	14 (70.0)	10 (50.0)
	Mastery Learning	17 (73.9)	7 (30.4)
2. Checks for response – tap and shout	Time Based	19 (95.0)	20 (100.0)
	Mastery Learning	21 (91.3)	22 (95.7)
4. Tells someone to phone the emergency response number and get an AED	Time Based	16 (80.0)	15 (75.0)
	Mastery Learning	23 (100.0)	17 (73.9)
5. Checks for no breathing or only gasping	Time Based	4 (20.0)	8 (40.0)
	Mastery Learning	8 (34.8)	5 (21.7)
6. Locates hand placement for compressions	Time Based	18 (90.0)	14 (70.0)
	Mastery Learning	21 (91.3)	12 (52.2)
7. Delivers first set of compressions (30 compressions in ≤ 18 seconds)	Time Based	19 (95.0)	18 (90.0)
	Mastery Learning	22 (95.7)	20 (87.0)
8. Gives 2 breaths	Time Based	10 (50.0)	13 (65.0)
	Mastery Learning	13 (56.5)	18 (78.3)
9. Delivers second set of compressions (23 of 30 compressions in correct location)	Time Based	20 (100.0)	19 (95.0)
	Mastery Learning	23 (100.0)	21 (91.3)
10. Gives 2 breaths	Time Based	11 (55.0)	12 (60.0)
	Mastery Learning	14 (60.9)	18 (78.3)
11. Turns on the AED immediately after it arrives	Time Based	20 (100.0)	20 (100.0)
	Mastery Learning	23 (100.0)	23 (100.0)
12. Delivers third set of compressions (compression depth ≥ 5cm)	Time Based	3 (15.0)	9 (45.0)
	Mastery Learning	5 (21.7)	9 (39.1)

^*Since the average score from two raters was used scores were rounded up.

One possible explanation for the lack of effect of mastery learning on BLS skills compared to the traditional teaching for laypeople is that there may have not been have enough of a contrast between the control and the intervention. Mastery learning is an instructional strategy that may be operationalized in many different ways. For example, instructors may consider that they are employing a ML strategy when they test performance after each step of a course without a fixed amount of time per step. However, the amount of deliberate practice, the quality and quantity of feedback given/received, the assessment tools used at each station, the context in which skills are tested (e.g. low- vs. high-fidelity; single vs. multiple rescuers) may be crucial for learning outcomes, in particular for long-term retention.^{21,24,26,35,36} Both groups engaged in sequenced learning with the same, clearly outlined learning objectives. While both groups were provided with general feedback, only the ML group received formative assessment for each learning objective with individualized feedback. In our study for both groups, feedback was terminal, i.e. provided when assessing participants at each station, and the feedback type and quantity was not standardized, therefore left at the instructor discretion and potentially participant to variability among learners. For the ML group, we left participants to determine when they felt that they had mastered the skills at each given station, that is, we relied on self-regulated learning.²⁴ We used an instructor regulated approach to feedback and assessment, as an instructor formally assessed participants and provided individualized feedback to determine if they actually mastered the skills to move on to the next station.³⁷ The TB group also received feedback from the instructor, but did not get an individualized assessment. Finally, the ML group had additional minimum passing standards for each station when compared to the TB group and all participants needed to complete the in-course BLS skills test in order to be awarded their certificate of course completion. The ML group was required to practise repeatedly until they passed the instructor assessment of the station before moving on to the next station, whereas the TB group practised until the instructor determined it was time for the group to move on to the next station.

In medical education, ML has become an increasingly popular approach and has been advocated for widespread adoption in the field.²¹ Although recent reports suggest that ML can improve skill acquisition and patient outcome²⁴ when used for the medical education of healthcare professionals,^21,26,27 it is unclear if the benefits of ML extend to teaching laypeople complex psychomotor skills, like BLS. While not our primary outcome, it is crucial to consider our unexpected findings with respect to pass/fail rates at the high-fidelity post-tests. Only one participant passed the simulated immediate post-test, yet all participants passed the AHA Heartsaver in-course BLS skills test necessary receive a BLS course completion certificate. Although other studies suggest that BLS skills are often poorly acquired,³⁸ the fact that participants passed the in-course tests brings into question the appropriateness of assessment tools used in the AHA in-course assessment or question having the in-course instructor serving as the unblinded assessor for this test. Although participants managed to master the skills required at each BLS station, they failed to master a simulated cardiac arrest (immediate post-test and retention test), i.e. they failed to transfer skills from a part task trainer (each station) to a full task trainer in a different environment (whole high-fidelity simulated scenario). This element between part and full task has previously been suggested to be of importance for learning other complex skills such as fiberoptic intubation,³⁹ and needs to be assessed properly in future mastery learning studies. Other studies have conveyed that fidelity should not impact learning outcome⁴⁰ and a variety of CPR courses have been shown to be efficacious for skill acquisition, even though the retention of CPR skills is poor regardless of teaching method.^16,17 Considering that a high-fidelity simulation scenario is intended to represent a real-life event, this study suggests that we may require different scoring and assessment methods for those are completing BLS courses to ensure that people who have completed the course can perform the skills if necessary in real-life.

There is a need for rigorous, high-quality research in the field of ML.²⁶ Recognizing that BLS training for laypeople should be focused on mastering essential skills,⁴¹ future studies should consider head to head comparison of different types of ML interventions in order to better understand/clarify what elements of ML produce a positive effect (or not).

Limitations

This trial has some limitations. The same certified instructor (KS) taught both groups, was part of the team of investigators and not blinded to the study hypotheses. There was no independent verification of meeting the predefined skill mastery for the ML group as we did not video record the teaching sessions. However, these elements are unlikely to explain the lack of superiority of ML compare to TB. One could hypothesize that having the instructor as part of the investigator team would probably increase the chance of finding a significant effect of the ML intervention. In this study, we were not able to test the transfer of skills from simulation into a clinical setting. However, this is nearly impossible to achieve with BLS skills and high fidelity simulation using a different scenario than the one used in BLS teaching is a commonly accepted surrogate for clinical resuscitation skills. Lastly, even though students are a frequently used group to evaluate BLS teaching strategies they might not reflect the typical bystander, who might acquire and retain skills differently.⁴² This study enrolled only students from the Faculty of Science, many of whom informally mentioned to research staff that they sought acceptance into medical school or required BLS training for summer jobs. For this reason, participants who consented to participate in the study may have had an increased motivation to complete BLS training when compared to those who did not participate. Therefore, our findings may be not generalizable to other types of laypeople, with less motivation to obtain BLS training.

Conclusion

This study found no major benefit of a ML BLS training course compared to a TB BLS course for the acquisition and four-month retention of knowledge or BLS skills among laypeople.

Appendix 1.

Mastery Learning Checklists