I would like add to above post. The sponsor is responsible for initially determining if the change meets the statutory criteria. This determination should be made by the person in the company responsible for such decisions, and should be based on the agency’s definition of credible information.
A change to the protocol to increase the sample size or expand the number of investigational sites continues to require submission and approval of an IDE supplement. FDA believes that expanding the study to increase either the number of subjects exposed to an investigational device or to increase the number of institutional sites participating in the trial affects the rights, safety, or welfare of the subjects and thus may not be implemented under the 5-day notice provision.

Other changes that don’t required FDA approval are following:
•Change in primary endpoint variable
•Change in indication