Patent ID: 8538514

Claim:
An active implantable medical device for monitoring physiological information relating to sleep comprising: at least one sensor configured to sense physiological information; and a processor coupled to the at least one sensor and configured to process the physiological information to detect at least one sleep state or stage, the processor: configured to detect a plurality of half waves in the sensed physiological information; wherein each detected half wave is characterized by a half wave amplitude and a half wave duration; configured to sort each detected half wave into one of a plurality of bins in a histogram based on whether each half wave amplitude falls between a predetermined minimum amplitude and a predetermined maximum amplitude and whether each half wave duration falls between a predetermined minimum duration and a predetermined maximum duration; configured to associate at least some of the histogram bins with a unique frequency band; configured with a histogram counter to keep track of a time interval over which the detected half waves are sorted; and configured to determine whether the sensed physiological information is representative of a sleep state based on the density of detected half wave in the one or more unique frequency band histogram bins.