Patent ID: 8366631

Claim:
A system for determining the respiratory flow of a patient receiving respiratory therapy, the system comprising: a breathing device defining a breathing area; a flow sensor configured to take one or more measurements of the air flow through the breathing area during a time window at a transition substantially between an expiratory phase and an inspiratory phase of a breath cycle, wherein the time window is a relatively small portion of the duration of the breath cycle; a pressure sensor configured to take one or more measurements of the pressure in the breathing area during the time window; and a processor configured to: determine a corrective flow factor by dividing (a) a measured air flow determined based on the one or more air flow measurements taken during the time window by (b) the square root of a measured pressure determined based on the one or more pressure measurements taken during the time window, such that the determined corrective flow factor corresponds specifically to air flow and pressured measured during the time window at the transition substantially between the expiratory phase and inspiratory phase of the breath cycle; obtain a subsequent airflow and a subsequent pressure; determine a product of the corrective flow factor and a square root of the subsequent pressure; and determine the patient's respiratory flow by subtracting from the subsequent air flow the product of the corrective flow factor and the square root of the subsequent pressure.