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Understanding why trials in critical care work (or not): the role of process evaluation


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Understanding why trials in critical care work (or not): the role of process evaluation 


A Process Evaluation (PE) aims to understand functioning of a study intervention to help explain study outcomes.
It does this by evaluating intervention delivery, mechanisms of action, and how context influences delivery and mechanism. 
Thus PEs are an essential part of designing and testing complex interventions.
PEs have previously been used for educational studies, but their use for evaluating clinical critical care interventions is limited.
Given the challenges inherent with multi-site trials in ICU, we sought to develop and test a framework to provide guidance for undertaking PEs in critical care trials.


1. Framework development

We reviewed and extracted the strongest components from the theoretical and methodological PE literature.
We considered factors specific to multi-centre complex critical care trials.
We designed a framework that combined the best aspects from the literature that would address factors that impact complex ICU trials.

2. Testing the framework

We used the multi-centre trial VAPrapid-2 (ISRCTN65937227) to test the framework. 
VAPrapid-2 was a complex critical care trial which:
explored the effectiveness of a rapid diagnostic test to rule out VAP.
tested whether antibiotic stewardship could be safely improved. 
challenged deeply entrenched prescribing characteristics of clinicians.


Our framework was influenced primarily by Stecklerand Linnan’sPE guidance. In addition, we considered attitudinal factors and participants’ responses to interventions, which are likely to impact trial adoption and intervention delivery. Our PE framework for critical care trials is shown in Figure 1.


Our framework was a good fit for this type of trial. In the context of VAPrapid-2, it identified both contextual and attitudinal factors as key moderators on the intervention delivery pathway, potentially impacting on trial outcomes. We recommend that this framework is tested in PEs of other types of critical care trials.

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