Background Pressures of patient demand and GP shortages have prompted a major workforce shift in primary care. Increasingly, paramedics are joining the primary care team but with wide variation in how they are employed, managed and supported. With numbers of paramedics in primary care rapidly increasing, evidence is needed to understand how PPC can be successfully implemented.

Methods We evaluated two collaborative health board/ambulance service initiatives. Each featured advanced paramedics (APs) – paramedics with additional education - rotating between their usual role and the new primary care role. In site A, the service of 9 APs spanned 5 general practice clusters. Site B featured 1 general practice with 8 APs. We completed 28 qualitative interviews with APs, managers, practice staff, and patients to understand implementation at both sites. We used the iPARIHS implementation framework (Harvey and Kitson 2015) as a conceptual lens to analyse transcripts, applying its interrelated domains of context, innovation, recipients and facilitation.

Results Site A was introduced as part of an innovation project, with external funding, a focus on training and personal development, and a structured lead in time. In site B paramedics were rapidly introduced to address an acute GP shortage, without formal training and support. The innovations were similar – home-visits and in-practice clinics undertaken by the practitioners. Interviewees (recipients) at both sites reported that the services helped to increase capacity, and were well received by patients and most staff. At site A: facilitation (by dedicated project workers) and training helped to shape the culture and preparedness. Site B APs and practice staff reported less readiness, impacting on morale, interprofessional working, and sustainability.

Conclusions Paramedics increasingly feature in primary care, but there is great variation in service models and implementation. Our comparative approach, informed by iPARIHS, illustrates the importance of understanding implementation - alongside or in addition to effectiveness.