Patent ID: 7988640

Claim:
A method for treating sleep disordered breathing by controlling a machine to apply breathable gas at positive pressure to the airway of a patient comprising the steps of: determining the patient's arousal index for use in an outer loop of a control algorithm, the arousal index being calculated from a size of the patient's breath and being a measure of the frequency of sleep arousals, monitoring the patient's respiratory airflow signal in an inner loop of said control algorithm to detect an airway obstruction, said control algorithm being used to adjust the positive pressure applied by said machine, if said arousal index is above a particular threshold, then increasing the sensitivity of detection of the obstruction and/or the aggressiveness of the treatment, and if the arousal index is below a particular threshold, then decreasing the sensitivity of detection of the obstruction and/or the aggressiveness of the treatment, wherein said arousal index is determined to be high by monitoring a flow rate over a sequence of breaths and checking whether the sequence is followed by a large breath.