Patent ID: 7427270
Filing Date: 2008-09-23
Classification: A61B

Abstract:
1. A sleep stage determination apparatus comprising: respiratory-signal detection means for detecting a variation in a respiratory signal from the body of a human subject; and sleep-stage determination means for determining a plurality of sleep stages with respect to each of a plurality of unit zones defined by segmenting said respiratory-signal variation on a given time period basis, said sleep-stage determination means including: in-bed/out-of-bed determination means for determining between an in-bed state and an out-of bed state, based on said respiratory-signal variation; body-movement determination means for determining the presence and level of a body movement, based on said respiratory-signal variation; wake determination means and intervening-wake determination means for determining between a wake state and a sleep state, based on a determination result of said body-movement determination means; sleep-initiation determination means for determining a sleep-initiation state having a transition from the wake state to the sleep state, based on said respiratory-signal variation, and the respective determination results of said in-bed/out-of-bed and wake determination means; sleep determination means for determining a depth of sleep based on said respiratory-signal variation, and respective determination results of said in-bed/out-of-bed, body-movement, sleep-initiation and wake determination means; and wake-up determination means for determining a wake-up state based on said respiratory-signal variation, and respective determination results of said in-bed/out-of-bed, body-movement, sleep-initiation, wake and sleep determination means; wherein said in-bed/out-of-bed determination means is operable, when said respiratory signal continues for a given time period or more at an amplitude equal to or greater than a given threshold value, to discriminate said in-bed state; wherein said body-movement determination means is operable to discriminate one of a gross body movement state, a fine body movement state and a no body movement state, based on a plurality of threshold values assigned, respectively, to an amplitude fluctuation and amplitude level of said respiratory signal and a cycle of said respiratory signal; and wherein said threshold value assigned to the amplitude fluctuation of said respiratory signal is compared to a standard deviation of amplitudes of three consecutive respiratory signals.