Polysomnographic titration of non-invasive ventilation in motor neurone disease (3TLA): protocol for a process evaluation of a clinical trial

Background: We are undertaking a multicentre randomised controlled trial to determine the effectiveness of including a sleep study (polysomnography (PSG)) to assist the commencement of non-invasive ventilation (NIV) in people with motor neurone disease (MND): the Polysomnographic titration of non-invasive ventilation in motor neurone disease (PSG4NIVinMND; 3-three letter acronym; 3TLA) trial. A process evaluation will be conducted alongside the clinical trial to understand: (1) the implementation of the 3TLA intervention in the trial sites, including barriers and enablers, and (2) the mechanisms through which the 3TLA intervention produces change. This protocol paper describes the rationale, aims and methods of the 3TLA process evaluation. Methods: To guide the design of the process evaluation, a logic model representing the 3TLA intervention, the likely mechanisms of impact, potential external contextual factors and assumptions, and the anticipated outcomes was developed by the researchers in collaboration with the 3TLA Trial Steering Committee. From this, five key process evaluation research questions were identified, a priori. The mixed-methods design is guided by three implementation frameworks: the Reach, Effectiveness, Adoption, Implementation and Maintenance (RE-AIM) framework, the Theoretical Domains Framework (TDF), and the Theoretical Framework of Acceptability (TFA). We will conduct semi-structured interviews with approximately 20–30 clinical trial participants (people with MND) and their carers, and focus groups and surveys with approximately 60 health professionals involved in delivering the intervention at each site. Quantitative process data will also be collected from the main clinical trial. Qualitative and quantitative data will be analysed iteratively throughout the trial, independent of the main trial outcome analyses. Process evaluation findings will be triangulated with the results of the clinical trial. Discussion: This process evaluation incorporates a mixed-methods design and is informed by three theoretical frameworks. It will provide insights into how the 3TLA intervention was implemented, for whom and how the 3TLA intervention was (and was not) effective, and what adaptations may be needed to facilitate future implementation into routine clinical practice. Trial registration: ClinicalTrials.gov NCT05136222. Registered on November 25, 2021.