I agree with you ks629. The Project Management Process Groups are all valid processes for the different management groups. What is important as Dr. Simon said is the Project Communications Management Group. This group is an integral part of medical device development. You need to have a clear and concise plan set in place of how communication between management and process groups will be established. We know each process group is intertwined but is separate from the different management sectors. Therefore, a clear and concise plan of action needs to be done to have effective communication. For example say you have a FDA regulator affairs individual for your company they are probably speaking to the Project Manager of the project which will relay the info to the Initiation Process Group and the Manager of Project Communications. The Communications manager needs to identify the various stakeholders to reach out to for the project to start. The project manager can evaluate it and state the decision to initiation group to either say “yes” or “no”.

Chapter 3 of PBOK goes into detail of the 42 management processes. Table 3-1 on page 42 is a great visual that shows the mapping of the 42 management processes into the 5 Project Management Process Groups (Initiating, Planning, Executing, Monitoring & Controlling, and Closing) and the nine Project Management Knowledge Areas (Project Integration Management, Project Scope Management, Project Time Management, Project Cost Management, Project Quality Management, Project Human Resource Management, Project Communications Management, Project Risk Management, and Project Procurement Management). Like @ks629 mentions that processes from any group may be used throughout the project life cycle. For medical devices another example would be regulatory where you would use all the process groups throughout the life cycle; selecting the regulatory route, plan communications as @krp67 mentions with FDA, plan risk management, perform quality assurance,and perform quality control etc.

When looking at Table 3 on page 42 it has the relationships between Process Groups and the relationships between Process Groups and external groups. What are the external groups involved and what are their roles/interactions with Process Groups?

Is it necessary to create a process group for every project by a company or a single process group looks after all the projects being done in the company?

According to the PMBOK, standard process groups can be created and applied (and edited as needed) for companies. Most companies have a dynamic way of doing their projects and if they are able to pin down the exact way they initiate, execute, and finish, they should be able to create the following archetypes that may be edited as needed:
1. Initiating Processing Group
2. Planning Process Group
3. Executing Process Group
4. Monitoring and Control Process Group
5. Closing Process Group

I think another great example of process group within medical device are product complaints and change control that fall under monitoring and controlling process group. This continuous monitoring provides the project team insight into the heath of the project and identifies any areas requiring additional attention. According to PMBOK, in multiphase projects, this process group coordinates project phases in order to implement corrective and preventive actions to bring the project into compliance with project management plan. The key benefit of this process group is that project performance is measured and analyzed at regular intervals, appropriate events, or exception conditions to identify variances from the project management plan. The monitoring and controlling process group also involves: 1) controlling changes and recommending corrective or preventive action in anticipation of possible problems, 2) Monitoring the ongoing project activities against the project management plan and the project performance measurement baseline, and 3) Influencing the factors that could circumvent integrated change control or configuration management so only approved changes are implemented.