112/05/03

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

Vincent Vincent Verhaert, Bart Haex, , Tom De Wilde,Daniel Berckmans,,Marie Vandekerckhove,Johan Verbraecken, , and Jos Vander Sloten

IEEE IEEE TRANSACTIONS ON ON INFORMATION TECHNOLOGY IN IN BIOMEDICINE, , VOL. . 15, , NO. 5, . 5, SEPTEMBER 2011

Presenter : : Kun-Han JhanAdvisor : : Dr. . Chun-Ju HouDate : : 2013.03.27

OutlineIntroductionMaterials and MethodsResultsDiscussionConclusion

112/05/03

Introduction

112/05/03

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

Introduction

112/05/03

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

Introduction

112/05/03

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

Introduction

112/05/03

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

Introduction

112/05/03

The assessment of body movements and posture shifts during the night◦Polysomnography (PSG)◦Actigraphy◦Video analysis

Literatures ReviewLiteratures ReviewRecently, 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

112/05/03

Literatures ReviewLiteratures 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

112/05/03

Literatures ReviewLiteratures 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

112/05/03

Literatures ReviewLiteratures Review Chan and coworkers◦ Infrared motion sensors ◦System was capable of monitoring activity in

bed and out of bedResults◦It could not discriminate between a person in

bed and a person near the bed

112/05/03

Purpose

112/05/03

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

Materials and MethodsMaterials and Methods

112/05/03

Data CollectionAnalysis of Bed MeasurementsAnalysis of Motor Patterns

Materials and MethodsMaterials and Methods

112/05/03

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

Materials and MethodsMaterials and Methods

112/05/03

Fifteen normal subjects (age 17 ~34years)◦Nine males◦Six females◦Body mass indices (BMI): between18.4 and 29.4

kg/m2

Materials and MethodsMaterials and Methods

112/05/03

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

Materials and Materials and MethodsMethods

112/05/03

Detection of Body Movements

◦ Zi : potentiometer output

Materials and Materials and MethodsMethods

112/05/03

Classification of Sleep PostureThe indentation measurements into four distinct classes

Prone Supine Left lateral Right lateral

Support vector machines (SVMs)

Materials and Materials and MethodsMethods

112/05/03

Classification of Sleep Posture Features

Shoulder–hip ratio Knee–hip ratio Total indentation Lateral asymmetry index (LAI) Lower leg indentation

Materials and Materials and MethodsMethods

112/05/03

Validationgraphical user interface

Materials and Materials and MethodsMethods

112/05/03

All recorded nights for motor patterns based on the following parameters

◦ Body movements(BM)◦ Postural immobility

ResultsResults- Performance- Performance

112/05/03

Movement Detection◦ Higher sensitivity for movement detection based on

bed measurements

ResultsResults- Performance- Performance

112/05/03

Posture Recognition◦ A training set :139 indentation samples

16 prone 36 Supine:low LAI 44 left lateral:negative asymmetry index 43 right lateral:positive asymmetry index

ResultsResults- Performance- Performance

112/05/03

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)

Results-Analysis of Motor Patterns

112/05/03

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 body movements and sleep

postures

DiscussionDiscussion

112/05/03

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

ConclusionConclusion

112/05/03

The sensors in sleep systems to provide accurate on motor patterns during sleep

The knowledge on adopted sleep postures is important

Might be used to advise people on how to change their sleep system settings if their sleep habits change