K-band Doppler radar for contact-less overnight sleep marker assessment: a pilot validation study

Abstract

An estimated 45 million persons in Europe are annually subjected to sleep-wake disorders. State-of-the-art polysomnography provides sophisticated insights into sleep (patho)physiology. A drawback of the method, however, is the obtrusive setting dependent on a clinical-based sleep laboratory with high operational costs. A contact-less prototype was developed to monitor limb movements and vital signs during sleep. A dual channel K-band Doppler radar transceiver captured limb movements and periodic chest wall motion due to respiration and heart activity. A wavelet transform based multi-resolution analysis (MRA) approach isolated limb movements, respiration, and heart rate from the demodulated signal. A test bench setup characterized the prototype simulating near physiological chest wall motions caused by periodic respiration and heartbeats in humans. Single- and multi-tone test bench simulations showed extremely low relative percentage errors of the prototype for respiratory and heart rate within -2 and 1%. The performance of the prototype was validated in overnight comparative studies, involving two healthy volunteers, with polysomnography as the reference. The prototype has successfully classified limb movements, with a sensitivity and specificity of 88.9 and 76.8% respectively, and has achieved accurate respiratory and heart rate measurement performance with overall absolute errors of 1 breath per minute for respiration and 3 beats per minute for heart rate. This pilot study shows that K-band Doppler radar and wavelet transform MRA seem to be valid for overnight sleep marker assessment. The contact-less approach might offer a promising solution for home-based sleep monitoring and assessment.

Nocturnal Respiratory Rate Dynamics Enable Early Recognition of Impending Hospitalizations

“…Additionally, NRR is an attractive biomarker because it can be measured by many different sensors. Adherenceindependent strategies can be based on strain gauges placed under the bed (20), mattress sensors (21)(22)(23)(24), or ultrawideband radar systems (25,26). For highly engaged patients, there are many wearables and smartphone apps capable of measuring respiratory rates (27)(28)(29).…”

Small Motion Detection and Non-Contact Vital Signs Monitoring with Continuous Wave Doppler Radars

“…On this basis, many different studies have been put forward a few different radar types [4]- [7]. Radar noncontact measurements are performed in cases such as sleep apnea problem [8], [9], sudden infant death syndromes [10], elderly and patient home care [11], [12], detection of lives under the earthquake debris [13], through wall live detection [14], [15], and surveillance of the target [16]. The success of the studies is very promising for the future and it has been shown that in the cases the rate of intervention can be increased.…”

Estimation of Arterial Pulse Wave Velocity from Doppler Radar Measurements: a Feasibility Study

“…The Doppler radar prototypes used in this study as well as the related signal processing have been described in detail in one of our earlier works [9].…”

“…Doppler radar has emerged as a promising technology for contact-less monitoring and assessment of physiological parameters. Contact-less estimation of respiration, limb movements as well as heart activity using Doppler radar have been demonstrated [8][9][10]. In this study, we aimed at: i) as a first step, assessing the feasibility of measuring arterial pulse waves at the femoral region using the Doppler radar technology, and consequently, ii) estimating the PTT between the heart-femoral regions as well as between the carotid-femoral regions using simultaneous Doppler radar measurements.…”