Summary of findings
The trial met its primary outcome, achieving a significant (if small) reduction in time to successful ventilator liberation. Although the intervention reached a high proportion of patients, delivery did not always encompass all components that were deemed necessary in progression towards extubation. This may explain the lack of effect between adherence rates and the primary outcome. The setting of sedation and ventilator support targets, as well as COMFORT assessment, achieved high adherence, and were important foundational work for intervention effectiveness. However, sedation targets could be inadequately explicit and/or focused, so that assessment did not always result in optimal patient sedation. Furthermore, setting sedation and ventilator targets did not guarantee that these targets were acted on. The same was apparent in respect of daily SBT screening. Although this component achieved relatively high adherence and successfully moved patients along the weaning pathway, some drop-off was clear and, again, the passing of a SBT screen did not always ensure the subsequent performance of an SBT. Completion of SBTs achieved the lowest adherence; non-performance represented a detrimental ‘stop’ in patients’ pathway through the intervention and, by extension, progress towards extubation. Nevertheless, despite variable component adherence rates, the intervention was delivered as a coherent bundle.The process evaluation enabled a nuanced understanding of multiple, overlapping processes, operating at the individual, unit and wider institutional level, involved in the delivery of the intervention. Importantly, the evidence provides insight into these processes in respect of each of the intervention components. It also highlights the countervailing nature of their collective working to moderate intervention delivery as theorised in our logic model.