1. A ventilation system, comprising: a processor communicably coupled to a computer readable medium, wherein the computer readable medium includes instructions executable by the processor to: receive a measured pressure value; receive a net flow value; calculate a patient effort value based on a relationship between patient effort, the measured pressure value and the net flow value; calculate a gas delivery metric, wherein the gas delivery metric varies as a function of the patient effort value; and cause a gas to be delivered consistent with the gas delivery metric.