Clinical decision support systems (CDS) can interpret detailed treatment protocols for ICU care providers. In open-loop systems, clinicians can decline protocol recommendations. We capture their reasons for declining as part of ongoing, iterative protocol validation and refinement processes. Even though our protocol was well-accepted by clinicians overall, noncompliance patterns revealed potential protocol improvement targets, and suggested ways to reduce barriers impeding software use. We applied Rita Kukafka and colleagues' (2003) IT implementation framework to identify and categorize reasons documented by ICU nurses when declining recommendations from an insulin-titration protocol. Two methods were used to operationalize the framework: reasons for declining recommendations from actual software use, and a nurse questionnaire. Applying the framework exposed limitations of our data sources, and suggested ways to address those limitations; and facilitated our analyses and interpretations.