A method for controlling an extracorporeal blood processing system, in response to fluid pressure changes in a fluid flow in an extracorporeal blood circuit, comprises the steps of: sensing a fluid pressure in the extracorporeal blood circuit； comparing the fluid pressure to a threshold value； stopping fluid flow, when the fluid pressure is below the threshold value； and resuming fluid flow, when the fluid pressure rises above the threshold value within a selected period of time or a discrete set point within a selected period of time. During the selected period, either the fluid pressure sensed automatically resolves or the method further comprises a step of setting a full alarm condition.
