Sensors may lead to better sleep

IMEC and its research affiliate, Holst Centre, have demonstrated a wireless sleep staging system.

The miniaturised system allows patients to wear the device in their home, thus enabling early screening of abnormal sleep profiles outside clinics.

The sleep staging system has been validated in the sleep laboratory at the University Hospital Centre in Charleroi, André Vésale Hospital (Belgium), against a commercially available reference system.

With this validation, the technology is ready for product development, opening new prospects for remote and comfortable sleep monitoring.

Ten per cent of the population in the US is affected by sleep apneas and a billion people worldwide experience some kind of chronic nasal congestion during sleep. The lightweight staging system can increase the comfort of disorder tests.

The system consists of a headband with three sensor nodes measuring two EEG-channels (electroencephalogram) to monitor the brain activity, two EOG-channels (electro-oculogram) to monitor the eye activity and one EMG-channel (electromyogram) to monitor the chin muscle activity.

These five signals provide the required information for sleep staging. The sensor nodes integrate IMEC’s ultra-low-power biopotential read-out ASIC to amplify and filter the five ExG signals.

The measured signals are transmitted to the recording computer. No additional wires from the head to the body or from the head to the recording device are needed. The system is optimised for low power, resulting in 12 hours of operation.

The system has been validated in a controlled clinical environment and benchmarked with ambulatory monitoring equipment. Twelve healthy volunteers were enrolled in the study and were monitored for a night using the wireless and the reference systems set up in parallel.

At the end of the study, the signals were given to a sleep expert for blind scoring, leading to two hypnograms for each subject. From the hypnograms, sleep statistics such as percentage of sleep time in each stage were deducted and compared for the two systems.

Hypnograms were also compared directly for similarity and the analysis proved the potential of wireless sleep staging systems to replace the current monitoring systems.

Wireless sensor nodes in intelligent body area networks may provide more comfortable healthcare systems by enabling home monitoring of patients. Home monitoring does not only increase the comfort of the patient, it is also a cost-efficient solution for expensive and time-consuming monitoring in hospitals.

Moreover, wireless monitoring systems provide more natural daily-life monitoring results.