1. A method for respiratory support, the method comprising: measuring a pressure and providing a measured pressure; measuring an inlet flow and an outlet flow, and providing a measured net flow; using a relationship between a first value related to the measured pressure, a second value related to the measured net flow, and a third value related to patient effort to provide a prediction of patient effort; and updating an interim value based at least in part on the prediction of the patient effort, wherein the interim value is a composite parameter that does not directly correspond to any identifiable respiratory parameter.