Method and systems for patient airway and leak flow estimation for non-invasive ventilation

A method for estimating patient airway flow in a non-invasive ventilator system, the method comprising the steps of:

• providing a non-invasive ventilator system, the non-invasive ventilator system comprising tubing having a distal ventilator end and a proximal patient end;
• obtaining a measurement of tubing compliance and a measurement of one or more parameters of a nonlinear leak flow model of the non-invasive ventilator system comprising leak flow resistance;
• measuring, using a distal gas flow sensor of the non-invasive ventilator system, gas flow at the distal ventilator end of the tubing;
• measuring, using a proximal pressure sensor of the non-invasive ventilator system, pressure at the proximal patient end of the tubing;
• determining an estimated gas flow at the proximal patient end of the tubing, the estimated gas flow comprising the measurement of gas flow at the distal ventilator end of the tubing, the measurement of pressure at the proximal patient end of the tubing, the obtained measurement of tubing compliance, and the obtained measurement of the one or more parameters of the nonlinear the leak flow model comprising leak flow resistance;
• determining a proximal pressure error value by subtracting the measured pressure at the proximal patient end of the tubing from an estimated pressure at the proximal patient end of the tubing;
• compensating, using a compensator, for the determined proximal pressure estimate error value;
• compensating for at least one error in the estimated gas flow at the proximal patient end of the tubing by feeding the estimated gas flow back into a sum of accumulated flows;
• determining an estimated gas flow leak, the estimated gas flow leak comprising the estimated pressure at the proximal patient end of the tubing and the obtained measurement of the one or more parameters of the nonlinear leak flow model comprising the leak flow resistance;
• monitoring for an unknown leak in the non-invasive ventilator system using a feedback controller to estimate a size of the unknown leak during ventilation;
• determining, when the unknown leak is identified, a gas flow leak correcting factor comprising leak information from a previous breath;
• adjusting, with the determined gas flow leak correcting factor, the estimated gas flow leak;
• and
• compensating for bias in the patient airway flow.