A method and processing system adapted to monitor respiratory instability by directly calculating a measure of periodicity and amplitude regularity, which is effectively a measure of disorganization, of a respiratory waveform. Normal respiration is a somewhat periodic signal whereas complete cessation of breathing would result in the respiratory signal reflecting measurement noise (i.e. aperiodic with minimal amplitude regularity). Thus, the measure is responsive to changes in the subject's breathing, and can distinguish between normal and abnormal breathing patterns.
