1. A system configured to deliver a pressurized flow of breathable gas to the airway of a subject in accordance with a therapy regimen, the system comprising: a pressure generator configured to generate a pressurized flow for delivery to the airway of a subject, wherein the pressurized flow includes breathable gas; a sensor configured to generate output signals indicating flow of the pressurized flow; one or more processors configured to execute modules, the modules comprising: a fluid parameter module configured to determine a fluid parameter of the pressurized flow based on the output signals, an effort module configured to determine an effort parameter such that the effort parameter for a given point in time is determined as a function of the difference between a first slope of the fluid parameter after the given point in time and a second slope of the fluid parameter before the given point in time, and a transition module configured to identify transitions in respiratory state based on comparisons of the effort parameter with a threshold effort parameter level, wherein the one or more processors are further configured to control the pressure generator to adjust one or more fluid parameters of the pressurized flow of breathable gas in accordance with a therapy regimen, wherein the therapy regimen dictates that the one or more fluid parameters vary based on the identified transitions in respiratory state.