Sleep stage determination apparatus

• US 7,427,270 B2
• Filed: 03/31/2006
• Issued: 09/23/2008
• Est. Priority Date: 04/01/2005
• Status: Expired due to Fees

• Current Assignee: Tanita Corporation (Tanita)
• Original Assignee: Tanita Corporation (Tanita)
• Inventors: Sasaki, Toshiaki, Izumi, Shuichi
• Primary Examiner(s): Marmor, II; Charles A.
• Assistant Examiner(s): Natnithithadha; Navin
• Application Number:
  US11/393,668
• Publication Number:
  US 20060169282A1
• Time in Patent Office: 907 Days
• Field of Search: 600529-543, 600/300, 600/301, 600/595
• US Class Current: 600/534
• CPC Class Codes: A61B 2562/168 Fluid filled sensor housings
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/4812 Detecting sleep stages or cycles
• CPC Class Codes: A61B 5/6892 Mats

Abstract

Disclosed is a sleep stage determination apparatus which comprises respiratory-signal detection means for detecting a variation of a respiratory signal from the body of a human subject, and sleep-stage determination means for determining a plurality of sleep stages using only the respiratory-signal variation. The sleep stage determination apparatus of the present invention can eliminate the need for detecting a plurality of biological signals and have simplified sensor and circuit configurations designed to detect only the respiratory signal variation which is relatively easily detectable. This makes it possible to reduce a detection error and achieve enhanced determination accuracy or creditability.

Claims

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.

2. The sleep stage determination apparatus as defined in claim 1, wherein said wake determination means is operable to discriminate one of a wake state, an unsteady state and a steady state, based on a variation of the body movement state within a given time period.

3. The sleep stage determination apparatus as defined in claim 1, wherein said intervening-wake determination means is operable, when the body movement continues for a given time period or more at a given level or more, to discriminate said given time period of wake state.

4. The sleep stage determination apparatus as defined in claim 1, wherein said sleep-initiation determination means is operable to discriminate the wake state based on a transition pattern of an initial wake state and a variation pattern of the respiratory signal in a region around sleep initiation of the subject, to determine said sleep initiation state.

5. The sleep stage determination apparatus as defined in claim 1, wherein said sleep-initiation determination means includes deep-sleep determination means for determining a deep sleep state, and REM-sleep/light-sleep determination means for determining a REM-sleep state and a light-sleep state.

6. The sleep stage determination apparatus as defined in claim 5, wherein said deep-sleep determination means is operable, when each of a respiratory rate within a given time period, a fluctuation of the respiratory rate and a fluctuation of a respiratory cycle is equal to or less than a given threshold, and there is no body movement within a given time period, to discriminate said deep sleep state.

7. The sleep stage determination apparatus as defined in claim 5, wherein said REM-sleep/light-sleep determination means is operable to make a determination based on comparing between a respiratory rate within a given time period and an average respiratory rate of the entire sleep states and counting a successive number of said given time periods, and a determination based on whether an apneic state is present or absent within said given time period, so as to discriminate said REM-sleep state and said light-sleep state in accordance with said determination results.

8. The sleep stage determination apparatus as defined in claim 1, wherein said wake-up determination means is operable, when no wake state appears before a given time period elapses from a time of the last determination of the wake state, to discriminate that said wake-up state occurs at said time of the last determination of the wake state.

9. The sleep stage determination apparatus as defined in claim 1, which further includes:

heartbeat signal detection means for detecting a heartbeat-related parameter; and

correction means for correcting said sleep stages using said detected heartbeat-related parameter.