Sustainability of improvement initiatives is recognised as a significant challenge to improving quality in healthcare. Rising demands and limited resources have highlighted the need to understand how sustainability can be supported, to maximise investments and benefits for patients. Unfortunately, relatively little is known about how to support sustainability in practice. The purpose of this thesis is to investigate how healthcare teams influence sustainability of improvement initiatives during the course of implementation and beyond.

A longitudinal mixed methods study was conducted to explore how structured approaches such as tools and frameworks can support sustainability. The application of one such tool, The Long Term Success Tool (LTST), was investigated across multiple QI programmes. The LTST was shown to be associated with a number of benefits (collaborative working, decision making, action planning, and reflection) but also a number of challenges (isolation, critical reflection, confusion, and inability to act). These findings highlight the complex nature of applying approaches in practice and the need to thoughtfully consider their impact and facilitation.

To explore how improvement teams influence sustainability throughout initiatives, four case studies were examined. Results demonstrate that the process of sustaining is an ongoing cycle, requiring teams to respond, adapt, and learn continuously. Analysis identified common challenges impacting sustainability: workforce stability, initiative impact, organisational priorities, workload distribution, and patient & public support. To address these challenges, twelve strategies for navigating sustainability in complex systems were employed. These strategies provide tangible actions for consideration by future initiatives to enhance and promote sustainability in other settings.

Healthcare organisations cannot afford to waste resources. Initiatives must be supported to enhance sustainability where possible; therefore, sustainability research should be prioritised. This emphasises the importance of the contributions made within this thesis, which provide a stepping stone for future research in this area to be conducted.