Introduction
The number of young adults with complex healthcare needs due to life-limiting conditions/complex physical disability has risen significantly as children with complex conditions survive into adulthood. Respite care and short breaks are an essential service, however, needs often go unmet after the transition to adult services, leading to a significant impact on the life expectancy and quality of life for this population. We aim to identify, appraise and synthesise relevant evidence to explore respite care and short breaks provision for this population, and to develop a conceptual framework for understanding service models.

Methods and analysis
A mixed-methods systematic review conducted in two stages: (1) knowledge map and (2) evidence review. We will comprehensively search multiple electronic databases; use the Citations, Lead authors, Unpublished materials, Google Scholar, Theories, Early examples, and Related projects (CLUSTER) approach, search relevant websites and circulate a call for evidence'. Using the setting, perspective, intervention/phenomenon of interest, comparison and evaluation framework, two reviewers will independently select evidence for inclusion into a knowledge map and subsequent evidence review, extract data relating to study and population characteristics, methods and outcomes; and assess the quality of evidence. A third reviewer will arbitrate where necessary. Evidence will be synthesised using the following approaches: quantitative (narratively/conducting meta-analyses where appropriate); qualitative (framework approach); policy and guidelines (documentary analysis informed approach). An overall, integrated synthesis will be created using a modified framework approach. We will use Grading of Recommendations Assessment, Development and Evaluation (GRADE)/GRADE-Confidence in the Evidence from Reviews of Qualitative Research to assess the strength and confidence of the synthesised evidence. Throughout, we will develop a conceptual framework to articulate how service models work in relation to context and setting.

Ethics and dissemination
Ethical approval is not required as this is a systematic review. We will present our work in academic journals, at appropriate conferences; we will disseminate findings across networks using a range of media. Steering and advisory groups were established to ensure findings are shared widely and in accessible formats. PROSPERO registration number CRD42018088780. © 2019 BMJ Publishing Group Limited.