Method and system for contactless monitoring and evaluation of sleep states of a user

• US 7,164,941 B2
• Filed: 12/22/2004
• Issued: 01/16/2007
• Est. Priority Date: 01/06/2004
• Status: Active Grant

• Current Assignee: Dale Julian Misczynski, Vladislav Bukhman
• Original Assignee: Dale Julian Misczynski, Vladislav Bukhman
• Inventors: Bukhman, Vladislav, Misczynski, Dale Julian
• Primary Examiner(s): Pezzuto; Robert
• Assistant Examiner(s): LEE, YUN H
• Application Number:
  US11/020,784
• Publication Number:
  US 20050148893A1
• Time in Patent Office: 755 Days
• Field of Search: 600/9, 600/13, 600/407, 600/411, 600/421, 600/422, 600/481, 600/483, 600/513
• US Class Current: 600/513
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/242 Detecting biomagnetic fields, e.g. magnetic fields produced by bioelectric currents
• CPC Class Codes: A61B 5/4809 Sleep detection, i.e. determining whether a subject is asleep or not
• CPC Class Codes: A61B 5/4812 Detecting sleep stages or cycles
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/6892 Mats
• CPC Class Codes: A61B 5/7257 using Fourier transforms

Abstract

The invention relates to a method and device for contactless monitoring and evaluation of sleep states of a user. The invention comprises a seamless continuous evaluation of cardiac activity variability and uses these data as an input for evaluation and quantitative assessment of sympathetic and parasympathetic activity of autonomic nervous system, which are reliable markers of physiological condition of a user. The device is embedded within two thin mattress pad layers, eliminating any direct contact between electrodes and a user'"'"'s body. The invention enables remote monitoring and evaluation of sleep states without involvement of trained professionals.

Claims

1. A method for contactless monitoring and evaluation of sleep states of a user comprising:

a) providing a contactless sleep monitoring device made in a form of a small mattress pad;

b) providing an electromagnetic inductance device embedded into said small mattress pad and connected to a processor;

c) passing an alternating current through an excitation coil;

d) measuring and processing at least one induced current waveform associated with changes in eddy current losses in the torso region of the user which is derived from a receiver coil;

e) determining sleep stages based on said changes in said eddy current.

2. The method of claim 1, wherein the act of processing said at least one induced current waveform comprises evaluation of a respiratory component and a cardiac activity component of said waveform.

3. The method of claim 2, wherein said respiratory component is smoothed using a cubic spline approximation method.

4. The method of claim 3, wherein said respiratory component is removed from said waveform to obtain said cardiac activity component.

5. The method of claim 2, wherein a duration of a cardiac cycle is determined using a width of a wave of said cardiac activity component, wherein the cardiac cycle is defined as:

$H<br><br><br><br>R_i=\frac{60}{W_i}*1000$

Where;

HR_i=heart rate of cardiac cycle i in beat/min;

W_i=width of wave i of said cardiac activity component in ms.

6. The method of claim 2, wherein a stroke volume is determined using a magnitude of a wave of said cardiac activity component and a cumulative cardiac activity index is determined using an area Q_i below a wave of said cardiac activity component.

7. The method of claim 6, wherein said area Q_i is determined by computing the integral of a wave of said cardiac activity component.

8. The method of claim 7, wherein the cardiac activity component signal is discrete and said area Q_i is determined by computing the sum of the amplitudes of each sample within a wave of said cardiac activity component.

9. The method of claim 6, wherein said cumulative cardiac activity index is calculated as follows:

CA_i=k×

Q_in.u.

Where;

k is a normalizing factor for converting the value of Q_i into a meaningful value;

Q_i=area of wave i;

n.u. stands for normalized unit.

10. The method of claim 1, wherein power spectrum analysis is used for determining said sleep stages.

11. The method of claim 10, wherein a Fast Fourier Transform algorithm is applied for calculation of a low frequency activity, reflecting both sympathetic and parasympathetic activities, and a high frequency activity, reflecting parasympathetic activity.

12. The method of claim 11, wherein a total power, a low frequency activity power, and a high frequency activity power are calculated for the first 5 minutes of processing using said Fast Fourier Transform algorithm.

13. The method of claim 12, wherein in order to determine said sleep stages a current wakefulness level is compared with a wakefulness signature level.

14. The method of claim 13, wherein if said current wakefulness level is less than or equal to 75% of said wakefulness signature level, then the user is determined to be in a Non-Rapid Eye Movement sleep state.

15. The method of claim 13, wherein if said current wakefulness level increases by more than 15% and said low frequency activity power doesn'"'"'t change and a previous record shows that the user was in a Non-Rapid Eye Movement stage, then the user is determined to be in a Rapid Eye Movement state.

16. The method of claim 13, wherein if said current wakefulness level increases by more than 15% and said low frequency activity power increases and a previous record shows that the user was in a Non-Rapid Eye Movement or Rapid Eye Movement sleep, then the user is determined to be in an after-sleep wakefulness state.

17. The method of claim 10, wherein a wakefulness signature level W_s is calculated as follows:

$W_s=\frac{{\mathrm{LP}}_s}{{\mathrm{HP}}_s}$

Where;

W_s=wakefulness signature level;

LP_s=signature sympathetic activity power;

HP_s=signature parasympathetic activity power.

18. The method of claim 10, wherein a current wakefulness level W_c is calculated in a 5 minute interval shifted by 30 seconds as follows:

$W_c=\frac{{\mathrm{LP}}_c}{{\mathrm{HP}}_c}$

Where;

W_c=current wakefulness level;

LP_s=current sympathetic activity power;

HP_s=current parasympathetic activity power.

19. A system for contactless monitoring and evaluation of sleep states of a user comprising:

a contactless sleep monitoring device made in a form of a small mattress pad;

an electromagnetic inductance device embedded into said small mattress pad and connected to a processor;

an excitation coil capable of inducing a magnetic field;

a sensing coil capable of acquiring signals representing changes of stroke volume and heart rate;

a power amplifier providing AC current to the excitation coil;

an amplifier capable of reducing an effect of residue voltage;

a lock-in amplifier for driving the excitation coil; and

a personal computer for controlling the lock-in amplifier, preprocessing digital waveform data, storing intermediate and sleep history data, calculations, graphic display and communication;

wherein the personal computer is configured to process at least one induced current waveform derived from the sensing coil associated with changes in eddy current losses in the torso region of the user and determine sleep stages based on the changes in said eddy current.

20. The system of claim 19, wherein said excitation coil is made from flexible plastic-type material using metal lines and providing a strong and relatively uniform induction field.