The paper addresses safety issues involved in making ad hoc interconnections among medical devices in order to assemble more complex medical systems. The main problem is that the systemic view may be easily concealed by nowadays behavioral modeling tools. Missing such a systemic view does not allow to have a precise view of what is being modeled: we propose instead to adopt novel methodological guidelines in developing assembled medical systems, basically by showing how a a clear and unambiguous semantics may be given for any state of the system being modeled, from specification to test phases. Such a state semantics may then be checked against safety axioms by simply visiting the state diagram without the need of resorting to model checking techniques.