Patent ID: 8607793

Claim:
A respiratory apparatus comprising: an air source adapted to selectively provide pressurized breathable air to a patient, a flow detecting device configured to sense respiratory airflow from the patient and to generate an airflow signal indicative of airflow of a breathing cycle, an obstruction detector coupled to said flow detecting device and configured to detect partial obstruction of a patient's airway by: measuring respiratory flow from the patient; detecting inspiratory flow from the measured respiratory flow; trimming the inspiratory flow to remove any expiratory pause; normalizing an effect of overshoot by estimating a peak flow value of a central portion of the inspiratory flow and by resetting each point outside the central portion that has a flow value exceeding the peak flow value; scaling the inspiratory flow to a reference value; calculating a mean deviation of the central portion of the inspiratory flow; calculating a flattening index from the mean deviation; and filtering the flattening index with a moving average filter, and a controller coupled to the flow detecting device and arranged to control the operation of the air source and to receive an obstruction signal indicative of a partial obstruction.