#$%^&*AU2015249041A120151119.pdf#####Abstract Methods and apparatus are disclosed for determining the occurrence of a closed or open apnea. Respiratory air flow from a patient is measured to give an air flow signal. The determination of an apnea is performed by applying an oscillatory pressure waveform of known frequency to a patients airway, calculating a complex quantity representing a patient admittance (12) and comparing its value with ranges (14,16) indicative of open or closed apneas. The method distinguishes open from closed apneas even when the model used to calculate admittance is not based on details of the respiratory apparatus. In addition the patient admittance may be compared with admittance during normal breathing to avoid having to characterize the airway. 311/5 Measure P,Q _10 atFG Generate 2 Admittance Values No No i Coe Yes j Ye s Open Mixed 20/ Increase CPA P Pressure 22 1 Log Open Reduces reAP Log Closed FIG. 1
