Arousal-level determining apparatus and arousal-level determining method

• US 9,801,579 B2
• Filed: 09/08/2014
• Issued: 10/31/2017
• Est. Priority Date: 03/19/2012
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Masuda, Yuta, Sano, Satoshi, Odagiri, Junichi
• Primary Examiner(s): Layno, Carl H
• Assistant Examiner(s): Piateski, Erin M
• Application Number:
  US14/479,488
• Publication Number:
  US 20140378857A1
• Time in Patent Office: 1,149 Days
• Field of Search: 600519
• CPC Class Codes: A61B 2503/22 Motor vehicles operators, e.g. drivers, pilots, captains
• 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 5/18 for vehicle drivers or machine operators
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/347 Detecting the frequency distribution of signals
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6893 Cars
• CPC Class Codes: A61B 5/6898 Portable consumer electronic devices, e.g. music players, telephones, tablet computers
• CPC Class Codes: A61B 5/7257 using Fourier transforms

Abstract

An arousal-level determining apparatus includes a generating unit, a calculating unit, an identifying unit, and a determining unit. The generating unit generates heartbeat-interval variation data, which indicates changes in heartbeat interval, on the basis of heartbeat signals indicating subject'"'"'s heartbeats. The calculating unit applies a band-pass filter, which allows passage of a certain range of frequencies, to each frequency band in the heartbeat-interval variation data while changing the frequency band, and calculates spectral density with respect to each frequency band applied with the band-pass filter. The identifying unit identifies a feature point corresponding to a spectral density peak in the calculated spectral densities in the frequency bands. The determining unit determines subject'"'"'s arousal level on the basis of the identified feature point.

Claims

1. An arousal-level determining apparatus comprising:

a memory; and

a processor coupled to the memory executes a process configured to;

receive heartbeat signals for a subject;

generate heartbeat-interval variation data, which indicates changes in heartbeat intervals, on a basis of the heartbeat signals indicating the subject'"'"'s heartbeats;

apply a plurality of times a band-pass filter, which allows passage of a frequency band of a certain range of frequencies, to the heartbeat-interval variation data, the frequency band being changed for each of the plurality of times, and calculate spectral densities with respect to each frequency band, by overlapping a range of frequencies within a first frequency band of the band-pass filter with a second frequency band of the band-pass filter that is nearest to the first frequency band, to detect peaks respectively of the calculated spectral densities;

identify as a feature point a peak in the calculated spectral densities based on the detected peaks; and

determine the arousal level of the subject on a basis of a spectral density and a frequency of the identified feature point, the arousal level inversely indicating a degree of sleepiness of the subject.

2. The arousal-level determining apparatus according to claim 1, wherein

the process is configured to apply the band-pass filter that allows passage of a range of frequencies in which the feature point shifts with respect to a change in arousal level of the subject.

3. The arousal-level determining apparatus according to claim 1, wherein

the process is configured to apply the band-pass filter to the heartbeat-interval variation data within a frequency range of a HF component.

4. The arousal-level determining apparatus according to claim 1, wherein

the process is configured to calculate spectral densities from the heartbeat-interval variation data, and, when no local maximum point exists in the calculated spectral densities, apply the band-pass filter to the heartbeat-interval variation data.

5. The arousal-level determining apparatus according to claim 1, wherein

the determining includes determining a change in the arousal level based on a change in a spectral density and a frequency of the identified feature point and in a width of a pulse made up of the detected peaks, and determining a risk level based on the determined arousal level and change therein;

and

the process is further configured to output information or an operation to alert the subject to the determined risk level, the information or operation including a message displayed on a display unit or an alarm.

6. A non-transitory computer-readable recording medium having stored therein an arousal-level determining program causing a computer to execute a process comprising:

receiving heartbeat signals for a subject;

generating heartbeat-interval variation data, which indicates changes in heartbeat intervals, on a basis of the heartbeat signals indicating the subject'"'"'s heartbeats;

applying a plurality of times a band-pass filter, which allows passage of a frequency band of a certain range of frequencies, to the heartbeat-interval variation data, the frequency band being changed for each of the plurality of times, and calculating spectral densities with respect to each frequency band, by overlapping a range of frequencies within a first frequency band of the band-pass filter with a second frequency band of the band-pass filter that is nearest to the first frequency band, to detect peaks respectively of the calculated spectral densities;

identifying as a feature point a peak in the calculated spectral densities based on the detected peaks; and

determining the arousal level of the subject on a basis of a spectral density and a frequency of the identified feature point, the arousal level inversely indicating a degree of sleepiness of the subject.

7. An arousal-level determining method by a computer, the arousal-level determining method comprising:

receiving heartbeat signals for a subject;

generating heartbeat-interval variation data, which indicates changes in heartbeat intervals, on a basis of the heartbeat signals indicating the subject'"'"'s heartbeats;

applying a plurality of times a band-pass filter, which allows passage of a frequency band of a certain range of frequencies, to the heartbeat-interval variation data, the frequency band being changed for each of the plurality of times, and calculating spectral densities with respect to each frequency band, by overlapping a range of frequencies within a first frequency band of the band-pass filter with a second frequency band of the band-pass filter that is nearest to the first frequency band, to detect peaks respectively of the calculated spectral densities;

identifying as a feature point a peak in the calculated spectral densities based on the detected peaks; and

determining the arousal level of the subject on a basis of a spectral density and a frequency of the identified feature point, the arousal level inversely indicating a degree of sleepiness of the subject.

8. An arousal-level determining apparatus comprising:

a processor; and

a memory, wherein the processor executes a process comprising;

receiving heartbeat signals for a subject;

generating heartbeat-interval variation data, which indicates changes in heartbeat intervals, on a basis of the heartbeat signals indicating the subject'"'"'s heartbeats;

storing the heartbeat-interval variation data in the memory;

applying a plurality of times a band-pass filter, which allows passage of a frequency band of a certain range of frequencies, to the heartbeat-interval variation data in the memory, the frequency band being changed for each of the plurality of times, and calculating spectral densities with respect to each frequency band, by overlapping a range of frequencies within a first frequency band of the band-pass filter with a second frequency band of the band-pass filter that is nearest to the first frequency band, to detect peaks respectively of the calculated spectral densities;

identifying as a feature point a peak in the calculated spectral densities based on the detected peaks; and

determining the arousal level of the subject on a basis of a spectral density and a frequency of the identified feature point, the arousal level inversely indicating a degree of sleepiness of the subject.