Patent ID: 8746248

Claim:
A method of detecting disconnection of a ventilation system during delivery of gas from a medical ventilator to a patient, the ventilation system comprising a processor and a memory, the method comprising: developing, by the ventilation system, an actual leakage equation describing leakage from the ventilation system as a function of pressure in the ventilation system, wherein developing the actual leakage equation comprises: taking one or more measurements of instantaneous pressure or instantaneous flow in the ventilation system during a period of delivery of gas to the patient; determining an actual leakage from the ventilation system during the period; based on the one or more measurements and the actual leakage for the period, modeling the actual leakage as a first leakage component through a first orifice of a fixed size and a second leakage component through a second orifice of a varying size, wherein the first and second leakage components are different functions of pressure in the ventilation system; and developing the actual leakage equation based on the first and second leakage components; developing a maximum leakage equation describing a maximum allowed leakage from the ventilation system as a function of pressure in the ventilation system; monitoring pressure in the ventilation system during delivery of gas to the patient during a breath; calculating an actual breath leakage from the ventilation system during the breath based on a current pressure using the actual leakage equation; calculating a maximum allowed leakage from the ventilation system during the breath based on the current pressure using the maximum leakage equation; and comparing the calculated maximum allowed leakage and the actual breath leakage.