This paper defines what the authors named Modular Operating Room, as a heterogeneous system with different subsystems and devices that should interact between them in a surgical scenario. This is an evolution of the concept of Intelligent Operating Room, that has led us to large and expensive OR. The paper uses ROS to define a new package that manages the communications between different devices that can appear in a surgical scenario, in such a way that the real surgical scenario can be made with any combination of these devices. One simplified application consisting on the automatic insertion of an endoscopic camera on a trocar is shown as an example of integration.