Reliable sensing of movement, breathing rate and heart rate
Within the BedSense project a newly developed, extremely sensitive pressure sensor is placed under the mattress to monitor even the smallest change in pressure. This contactless bed sensor is used to detect:
- Breathing rate
- Heart rate reliably
The bed sensor is placed under the mattress
Benefit of placing the sensor under the mattress is that the existing mattress can be used and that users, also after months of use, do not feel the sensor at all.
Raw information is stored in high-resolution on SD-card. At the moment the functional prototype is validated at Kempenhaeghe, the leading sleep centre in the Netherlands for sleep disorders and epilepsy. BedSense bed sensor measurements are compared to the golden standard: the Kempenhaeghe polysomnography system.
These measurements will help to refine the various signal processing algorithms for automatic feature extraction for specific diseases and patient groups.
Application areas – home monitoring of OSA, COPD & sleep disorders
Current focus is on three use cases: effectiveness of sleep interventions in the home environment (like OSA), sleep quality for Parkinson patients and epilepsy detection.
- Accurate & medically validated sleep monitoring.
- Contactless, placed under the mattress
- Presence, movements, breathing, heart rate
- Medical research, clinical and home applications
The BedSense system exists of the following components:
- BedSense datalogger, functions:
- Store measurements of upto 3 sensors in raw format for later signal analysis
- Live data-feed in Matlab for real-time testing of features (via USB interface)
- 1-3 BedSense contactless bedsensor’s
- Power supply (5V)
- Micro SD card + adapter card
- External sync: TTL, 3.5mm jack cable
- Remote control: start/stop recordings and check recording status when the BedSense system is placed under a hospital bed.
- Sensors: 1 to 3 sensors
- Sampling Rate: 100 Hz
- Sampling Rate Drift: 0.021% / ºC
- ADC Resolution: 24 bit (20bit effective)
- External synchronization
- Sync Pulse: K x 0.5 seconds with K=1-144
- Sync Amplitude: 0 volt (off) – 3 volt (on)
- Sync Frequency: 10 minutes (first pulse; K=1 at t=0 sec)
- Sync Interface: 3.5mm mono jack plug
- Power: 5V power adapter and internal battery powered (upto 10 hours)
- Recordings: max 100 files
- Storage: 32Gb micro SD card
Stored data files can be exported to BDF format with the supplied BDF convertor. BDF is the 24-bits version of the EDF file. BDF files can be viewed with multiple (open source) software packages like EDFBrowser. The BDF file contains 3 data signals per each connected sensor channel XX:
- ChXX: 24 bit sensor data
- ChXX_Syncpulse: Sensor synchronization pulses
- ChXX_Temperature: Sensor temperature (updated every 0.5sec)
So when all 3 sensors were connected, the BDF file holds 9 signals in total.
122 complete night recordings have been made at Kempenhaeghe which are currently analyzed and used for creation of new algorithms. BedSense is available as a research evaluation prototype for detailed monitoring of people and patients. Besides additional technical and medical research we are investigating the possibilities for embedding the technology into existing and new applications. Date: 06-03-2018