Unobtrusive Assessment of Motor Patterns During Sleep Based on Mattress Indentation Measurements

1. UnobtrusiveAssessment of Motor Patterns During Sleep Based on Mattress Indentation Measurements Vincent Verhaert, Bart Haex, Tom De Wilde,DanielBerckmans,MarieVandekerckhove,JohanVerbraecken, andJos Vander Sloten IEEE TRANSACTIONS ON INFORMATIONTECHNOLOGY IN BIOMEDICINE, VOL. 15, NO. 5, SEPTEMBER2011 Presenter : Kun-HanJhan Advisor : Dr. Chun-JuHou Date : 2013.03.27

2. Outline • Introduction • Materials and Methods • Results • Discussion • Conclusion

3. Introduction • Inadequate sleep is generally considered as one of the most compelling problems in the industrialized world • Performance • Health • Quality of life • Sleep disturbance • Associated with cognitive and emotional stress, or physical discomfort

4. Introduction • Sleep system • Mattress, supporting structure • The main function of sleep systems • To support the human body in a way that allow the muscles and intervertebral discs to recover from nearly continuous loading by day. • The shape of the spine • A slightly flattened lumbar lordosis

5. Introduction • The mechanical characteristics of a sleep system should be optimized concerning • Body contour • Weight distribution • Healthy sleep requires the presence of various posture shifts per night • Posture changes • Body movements

6. Introduction • The relationship between sleep disorders and specific movement and posture • Arousal and sleep fragmentation • Much movement during sleep • Restless legs syndrome during sleep • Periodic limb movements during sleep • Obstructive sleep apnea syndrome(OSAS) • Body posture: supine

7. Introduction • The assessment of body movements and posture shifts during the night • Polysomnography (PSG) • Actigraphy • Video analysis

8. Literatures Review • Recently, interest in instrumenting the bed has grown to study body movements and monitor sleep. • The advantage of this approach • No equipment has to be mounted on the subjects themselves

9. Literatures Review • Lu et al. and Tamura et al. • Assessed changes in bed temperature as an index of body movement • Results • Leg movements were detected more accurately than torso movements • The inherently long reaction time of temperature sensors • making it impossible to discriminate between short movements

10. Literatures Review • Van der Loos • 54 resistive temperature devices with an array of 54 force sensitive resistors • Breathing rate and temperature overnight • Results • Slept in a supine posture during the entire night

11. Literatures Review • Chan and coworkers • Infrared motion sensors • System was capable of monitoring activity in bed and out of bed • Results • It could not discriminate between a person in bed and a person near the bed

12. Purpose • This paper focuses on mattress indentation measurements for the unobtrusive assessment of both body movement and adopted sleep posture during the night.

13. Materials and Methods • Data Collection • Analysis of Bed Measurements • Analysis of Motor Patterns

14. Materials and Methods • Sleep systems • Measure the perpendicular indentation of the mattress surface in a 2-D grid of 170 points at a sampling rate of 0.5 Hz mm

15. Materials and Methods • Fifteen normal subjects (age 17 ~34years) • Nine males • Six females • Body mass indices (BMI): between18.4 and 29.4 kg/m2

16. Materials and Methods • The experial process • Registered by the sleep systems • Activation graphic recordings • sampling rate of 32 Hz • The subjects were asked in the morning • Polysomnographic and video recordings served as a gold standard

17. Materials and Methods • Detection of Body Movements Zi : potentiometer output

18. Materials and Methods • Classification of Sleep Posture • The indentation measurements into four distinct classes • Prone • Supine • Left lateral • Right lateral • Support vector machines (SVMs)

19. Materials and Methods • Classification of Sleep Posture • Features • Shoulder–hip ratio • Knee–hip ratio • Total indentation • Lateral asymmetry index (LAI) • Lower leg indentation

20. Materials and Methods • Validation • graphical user interface

21. Materials and Methods • All recorded nights for motor patterns based on the following parameters • Body movements(BM) • Postural immobility

22. Results- Performance • Movement Detection • Higher sensitivity for movement detection based on bed measurements

23. Results- Performance • Posture Recognition • A training set:139indentation samples • 16 prone • 36 Supine:low LAI • 44 left lateral:negative asymmetry index • 43 right lateral:positive asymmetry index

24. Results- Performance • Posture Recognition • The test set consisted of 30 fully recorded nights • Mattress indentation, video, and PSG recording • 10 different persons(six males and four females)

25. Results-Analysis of Motor Patterns • Analysis of Motor Patterns • A total of 60 nights • 15 persons(9 males and 6 females,aged 26.1 ± 8.8 years) • Recorded and analyzed for bodymovements and sleep postures

26. Discussion • Mattress indentation measurements are useful for the assessment of during sleep • It does not place any burden • It captures movements of the entire body • Complete set of motion related parameters is provided

27. Conclusion • The sensors in sleep systems to provide accurate on motor patterns during sleep • The knowledge on adoptedsleep postures is important • Might be used to advise people on how to change their sleepsystem settings if their sleep habits change