Sleepiness assessment apparatus

• US 8,979,761 B2
• Filed: 05/26/2010
• Issued: 03/17/2015
• Est. Priority Date: 06/08/2009
• Status: Active Grant

• Current Assignee: Public University Corporation Nagoya City University
• Original Assignee: Public University Corporation Nagoya City University
• Inventors: Yokoyama, Kiyoko, Takahashi, Issei, Ohashi, Hayato, Tabata, Genki
• Primary Examiner(s): Natnithithadha, Navin
• Assistant Examiner(s): WEARE, MEREDITH H
• Application Number:
  US13/376,719
• Publication Number:
  US 20120078122A1
• Time in Patent Office: 1,756 Days
• Field of Search: 600/484, 600/529, 600/500, 600/509
• US Class Current: 600/484
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/18 for vehicle drivers or machine operators
• CPC Class Codes: A61B 5/6887 mounted on external non-worn devices, e.g. non-medical devices
• CPC Class Codes: B60K 28/02 responsive to conditions relating to the driver
• CPC Class Codes: B60K 28/066 actuating a signalling device B60K28/063 takes precedence
• CPC Class Codes: B60W 2040/0827 due to sleepiness
• CPC Class Codes: B60W 2540/22 Psychological state; Stress level or workload
• CPC Class Codes: B60Y 2400/902 giving haptic or tactile signals

Abstract

A sleepiness assessment value P1 is set to be an average heart rate HR (S130). A sleepiness assessment value P2 is set to be a standard deviation σ of a respiration interval RespI for one minute (S150). A sleepiness assessment value P3 is set to be a value that is obtained by dividing, by one minute, an integrated value of a square of an average heartbeat interval RRIavg in a case where a variation in which a heartbeat interval RRI increases occurs (in a case where an RRI count value Xi is a value of one) (S190). A sleepiness assessment value P4 is set to a value that is obtained by averaging a variation ratio in a case where a variation in which the respiration interval RespI increases occurs (in a case where an RRI count value Yi is a value of one) (S210). A sleepiness assessment value P is set to be a value obtained by summing values that are obtained by multiplying the individual sleepiness assessment values P1 to P4 by weight coefficients a to d, each of which is set for a corresponding one of the sleepiness assessment values P1 to P4 (S220). When the sleepiness assessment value P is smaller than a value of zero, it is determined that a person is highly alert (S240), and, when the sleepiness assessment value P is equal to or larger than the value of zero, it is determined that the person is less alert (S250).

Claims

1. A sleepiness assessment apparatus for determining whether or not a subject is sleepy, the sleepiness assessment apparatus comprising:

a respiration-interval acquisition unit configured to acquire a plurality of respiration intervals of the subject;

a heartbeat-interval acquisition unit configured to acquire a plurality of heartbeat intervals of the subject;

a sleepiness assessment unit configured to;

determine whether a variation occurs in which the acquired respiration intervals increase, calculate a degree of the variation in a case where the variation occurs, and set a first sleepiness parameter based on the calculated degree of the variation,

calculate an average value of the plurality of acquired heartbeat intervals, determine whether a variation occurs in which the acquired heartbeat intervals decrease, calculate a frequency of the variation in a case where the variation occurs and set a second sleepiness assessment parameter based on the calculated frequency of the variation and the calculated average value of the heartbeat intervals, and

determine whether or not the subject is sleepy based on the first sleepiness assessment parameter and the second sleepiness assessment parameter; and

an actuator configured to apply a stimulus to the subject for improving the subject'"'"'s degree of arousal based on whether or not the subject is sleepy.

2. The sleepiness assessment apparatus according to claim 1,

wherein the sleepiness assessment unit is configured to, in the case where the variation occurs in which the acquired respiration intervals increase, calculate a ratio of the variation, and set the first sleepiness assessment parameter based on the calculated ratio obtained by the variation.

3. The sleepiness assessment apparatus according to claim 1,

wherein the sleepiness assessment unit is configured to set a third sleepiness assessment parameter based on a standard deviation of the acquired respiration intervals, and is configured to determine whether or not the subject is sleepy based on the first sleepiness assessment parameter, the second sleepiness assessment parameter, and the third sleepiness assessment parameter.

4. The sleepiness assessment apparatus according to claim 1,

wherein the sleepiness assessment parameter includes a plurality of sleepiness assessment parameters, and the sleepiness assessment unit determines, by using the plurality of sleepiness assessment parameters and weights, whether or not the subject is sleepy, each of the weights being set for a corresponding one of the plurality of sleepiness assessment parameters.

5. The sleepiness assessment apparatus according to claim 1,

wherein the sleepiness assessment unit is configured to set the second sleepiness assessment parameter based on the calculated frequency of the variation and the calculated average value of the heartbeat intervals by integrating the calculated average value of the heartbeat intervals every time the variation occurs in which the acquired heartbeat intervals decrease and dividing the integrated value by the number of heartbeats per unit time.

6. The sleepiness assessment apparatus according to claim 5,

wherein the sleepiness assessment unit is configured to set the second sleepiness assessment parameter based on the calculated frequency of the variation and the calculated average value of the heartbeat intervals by integrating a square of the calculated average value of the heartbeat intervals to obtain an integrated value every time the variation occurs in which the acquired heartbeat intervals decrease, and dividing the integrated value by a unit time.