Andreas Schrempf, Thomas Minarik Upper Austria University of Applied Sciences Medical Engineering Linz, Austria An interactive activity- monitoring device for use in home- rehabilitation

Upper Austria University of Applied Sciences 4th International Conference MRH | Pilsen June 30th 2011 Page 2

Upper Austria University of Applied Sciences 4th International Conference MRH | Pilsen June 30th 2011 Page 3

Faculty of Applied Health and Social Sciences 4th International Conference MRH | Pilsen June 30th 2011 Page 4 Education: Applied Health and Social Sciences Research: - Medical Engineering - Assisting Technologies and Processes for the Elderly Campus Linz... Emergency Hospital Linz Emergency Hospital Linz Rehab. Amb. Linz Rehab. Amb. Linz General Hospital Linz General Hospital Linz Pediadric and Gynecological Clinic Linz Pediadric and Gynecological Clinic Linz GKK-OOE Health Ins. Comp. GKK-OOE Health Ins. Comp. Hospital Diakonissen Hospital Diakonissen Neurological Clinic Wagner Jauregg Linz Neurological Clinic Wagner Jauregg Linz Most of the medical partners are within a square km. University of Applied Sciences Campus Linz University of Applied Sciences Campus Linz

Activity Measurement Application Areas Application and Benefits : – preventive care – measures taken to prevent diseases – motivation factor – therapy evaluation – objective measures of the therapy progress – Documentation – assessment – therapy control – compare exercise measurement data against golden reference – adjust intensity according progress, – provide feedback 4th International Conference MRH | Pilsen June 30th 2011 Page 5

Device Development Actilab – Features developed in cooperation with g.tec medical engineering – Device development – g.tec medical engineering – Algorithm development – FH-OOE Mobile system – duration, intensity, frequency of activity Intended to become a medical device Triaxial accelerometer – measuring range: ±18g – Resolution: ~ 6.25mg Barometric pressure sensor – Measurement range kPa – Resolution: ~10cm GSM module 4th International Conference MRH | Pilsen June 30th 2011 Page 6

Device Development NEON – Features developed in cooperation with spantec GmbH Triaxial accelerometer – measuring range: ±8g – Resolution: ~ 3.9mg Barometric pressure sensor – 30 kPa kPa measuring range – Resolution: 1.5 Pa ( 10cm at s.l.) GPS module – accuracy position: 5m CEP (Circular error probable) – accuracy velocity: 0.1m/s – update rate: 1Hz 4th International Conference MRH | Pilsen June 30th 2011 Page 7

Device Development NEON – Features 4th International Conference MRH | Pilsen June 30th 2011 Page 8 mini USB connector LEDs ANT module

Device Development NEON – Features Compatible with all ANT(+) devices – e.g. Garmin HRM1G micro SD-card – 2 GB data memory UART connection to local PC ANT module – 2.4GHz wireless networking protocol designed for wireless sensor networks – network (internet) connection possible (bridging) 4th International Conference MRH | Pilsen June 30th 2011 Page 9

Device Development Communication Concepts 4th International Conference MRH | Pilsen June 30th 2011 Page 10 Actilab NEON

Accelerometry COM moves during Walking 4th International Conference MRH | Pilsen June 30th 2011 Page 11 Center Of Mass (COM) moves during walking according to the different phases of the walking cycle

Accelerometry COM moves during Walking 4th International Conference MRH | Pilsen June 30th 2011 Page 12 Frequency and amplitudes change depending on walking speed

Accelerometry COM moves during Walking 4th International Conference MRH | Pilsen June 30th 2011 Page 13 Putting an activity measurement device near to the COM allows to measure these movements in terms of the accelerations. vertical acceleration:

Accelerometry PA - Energy Expenditure 4th International Conference MRH | Pilsen June 30th 2011 Page 14 Total Energy Expenditure (TEE) TEE = BMR + DIT + PA BMR: basal metabolic rate BMR DIT: diet induced thermogenesis PA: physical activity Physical activity level (according to WHO) (1.2 sitting, walking)

Accelerometry PA - Energy Expenditure 4th International Conference MRH | Pilsen June 30th 2011 Page 15 Estimation ( modified Goldman equation) T: terrain factor : overall efficiency m: body mass v: walking speed a(v): total average acceleration, depends on walking speed dh/dt: change of elevation per time unit g: gravity constant conditionT asphalt1.0 gravel1.4 soft underground1.8 loose sand2.1 deep snow (25cm)3.3

Accelerometry PA - Energy Expenditure 4th International Conference MRH | Pilsen June 30th 2011 Page 16 estimation based on mean acceleration (indoor/outdoor) measured by GPS (outdoor) measured by acceleration sensors measured by barometric pressure sensor (indoor/outdoor) measured by GPS (outdoor) overall efficiency, depends on age, fitness level, gender, …

Accelerometry PA - Energy Expenditure 4th International Conference MRH | Pilsen June 30th 2011 Page 17 mean total body acceleration High-pass filtering (offset, artefacts) rectifying (power) Low-pass filtering (mean acceleration) distinguishing between no activity, walking and running estimation of walking speed a(t)LP|. |HP walking running

Accelerometry PA - Energy Expenditure 4th International Conference MRH | Pilsen June 30th 2011 Page 18 Estimation of walking speed (based only on accelerations) walking running

Accelerometry PA - Energy Expenditure 4th International Conference MRH | Pilsen June 30th 2011 Page 19 heart-rate measurements allows to estimate the EE: depends on age, depends on fitness level, depends on gender, different for walking and running, hysteresis, direct measurement of the energy expenditure (allows to quantify the efficiency) HR [bpm] dE/dt [kcal/min/kg]

Accelerometry Accuracy Assessment 4th International Conference MRH | Pilsen June 30th 2011 Page 20 altitude: GPS vs. pressure sensor pressure sensor requires stable weather conditions, GPS accuracy limited, when low signal quality GPS may loose signal, does not work indoor forest (low GPS signal quality)

Accelerometry Accuracy Assessment 4th International Conference MRH | Pilsen June 30th 2011 Page 21 walking speed: GPS vs. barometric press. sensor pressure sensor requires stable weather conditions, GPS may loose signal, does not work indoor --> sensor fusion stairs down altitude GPS (low signal quality) round trip stairs up, then down altitude barometer walking speed GPS walking speed prediction by accelerometer (problem: up and down)

Accelerometry Sensorfusion/Autom. Calibration 4th International Conference MRH | Pilsen June 30th 2011 Page 22 Problems: GPS signal only available outdoor GPS: altitude low accuracy, especially for small altitude differences barometric height measurement only valid for short time or during stable weather conditions Speed prediction by accelerometer not accurate enough when going up or down Efficiency not constant varies between different subjects (depending on age, fitness level or pathology)V Solutions: Sensor fusion combining GPS and barometric pressure sensor. Weighting of signal depends on signal quality and/or availability Individual calibration of speed prediction algorithm, during good GPS-signal quality Individual calibration of efficiency using heart-rate monitor