1. A method for respiratory support, the method comprising: identifying a target proportion of patient effort; 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 an estimated normalized prediction error, wherein the estimated normalized prediction error is based at least in part on a current estimated value of a parameter vector to calculate an estimate of patient effort from the measured pressure and measured net flow; and supplying a gas in proportion to the estimate of patient effort based on the target proportion.