Patent ID: 7370650

Claim:
A method for providing air to an airway of a patient, comprising: supplying an inspiratory flow of air at a first pressure during a respiratory cycle of a patient; determining whether the respiratory cycle is a valid respiratory cycle, including, (a) measuring a rate of the inspiratory flow of air, (b) measuring a volume of the inspiratory flow of air, (c) measuring a duration of the inspiratory flow of air, (d) measuring a duration of the respiratory cycle, wherein the respiratory cycle is determined as valid when the rate of the inspiratory flow of air is greater than an inspiratory flow rate threshold, the volume of the inspiratory flow of air is greater than an inspiratory volume threshold, the duration of the inspiratory flow is within an inspiratory duration interval and the duration of the respiratory cycle is within a respiratory cycle duration interval; incrementing a respiratory cycle counter when the respiratory cycle is determined as valid; setting a problem appearance indicator, including, (e) determining a sinusoidal curve equivalent to a curve of the inspiratory flow of air during the respiratory cycle, (f) calculating a correlation criterion between the inspiratory flow rate curve and the equivalent sinusoidal curve, (g) calculating a surface criterion proportional to the ratio of an area delimited by the inspiratory flow rate curve to an area delimited by the equivalent sinusoidal curve, (h) setting the problem appearance indicator to a problem absence state or setting the problem appearance indicator to a problem appearance state when the calculated correlation criterion is less than a correlation criterion threshold or when the calculated surface criterion is less than a surface criterion threshold; incrementing a problem appearance counter when the problem appearance indicator changes from the problem absence state to the problem appearance state; and increasing the pressure of the inspiratory flow of air above the first pressure when the respiratory cycle has been determined to be a valid respiratory cycle, when the respiratory cycle counter is greater than a respiratory cycle threshold and when the problem appearance counter is greater than or equal to a problem appearance threshold.