Maybe there's a misunderstanding here.
Continuous Improvement Process is not the same as
Continuous Process Improvement.
I'm not aware of a specific FDA guidance for medical device manufacturers on Continuous Improvement Process. In my understanding continuous improvement can be achieved through a systematic and consistent application of a quality management system such as that prescribed by 21 CFR 820.
This document discusses Innovation and Continuous Improvement in Pharmaceutical Manufacturing.
Chapters IV & V of
this document seem to be relevant too, though targeted at pharmaceuticals manufacturing.