The FirstCPR cluster randomised trial delivered multimodal basic life support (BLS) learning opportunities to community organisations. An a priori process evaluation examined intervention implementation, including participation, reach, uptake and member engagement.

The study used a multimethod process evaluation. Data were collected via semistructured interviews, focus group discussions, participant surveys, study records, web analytics and in-field observations. These sources captured participation patterns and implementation measures (delivery, reach, uptake and engagement: opt-in to digital messages and attendance at training sessions), as well as reasons for refusals and withdrawals. Qualitative data were analysed thematically and organised using the UK Medical Research Council process-evaluation framework. Qualitative and quantitative data were analysed separately and subsequently interpreted collectively to contextualise implementation patterns and identify barriers and enablers that influenced trial successes and failures.

Intervention uptake and engagement varied significantly across organisations, with greater success observed in social and faith-based groups. Of the 82 intervention clusters, 78 (95%) received intervention materials; 74 (90%) engaged in at least one activity and 15 (18%) engaged in all activities. Participation was primarily driven by the organisation’s leadership interest and support in providing BLS training to members, and by the time available to facilitate intervention activities. The presence of a dedicated liaison/champion emerged as the most critical enabler of member engagement and implementation. Feedback recommended concise, simple and culturally tailored modules, with practical components delivered in shorter, convenient sessions. Intervention delivery was affected by contextual challenges, including COVID-19 disruptions that limited in-field recruitment and group activities.

Process evaluation can strengthen community-based interventions by identifying mechanisms and contextual factors that shape implementation and engagement. Partnering with social and faith-based organisations may be an effective approach to disseminating educational programmes such as life-saving skills to lay communities. Minimising research burden and ensuring organisational leadership support may improve participation while brief, practical and culturally tailored training may enhance engagement.

ACTRN12621000367842.