Cooperation between Health Care Professionals is essential for the quality of care. Workflow systems could improve the transfer of informations and responsibilities within Health Care Actors. We have proposed a conversation-based Workflow in order to modelize the therapeutics plan in the ICU. In such a complex field, the flexibility of the workflow system is essential for the system to be usable. We have introduced some dynamicity by adding roles in the model. With the use of roles, the dynamicity of the workflow is assumed by the routing process. We need to use simulation to be able to study the impact of routing algorythms on the efficiency of the coordination.