A Smart Flexible Vital Signs and Sleep Monitoring Belt Based on MEMS Triaxial Accelerometer and Pressure Sensor

People spend about one third of their lifetime in sleep, and sleep quality has a great impact on people’s health. Therefore, vital signs and sleep quality monitoring are more and more important. In this article, a novel smart flexible sleep monitoring belt with MEMS triaxial accelerometer and pressure sensor is developed to detect vital signs, snore events, and sleep stages. Besides, the related algorithms and methods for data preprocessing, heart and respiration rates detection, snoring recognition, and sleep stages classification are proposed in detail. Then, a series of sleep experiments is performed based on the experimental platform for the smart flexible belt, and the test results measured by PolySomnoGraphy are used as the golden standards for comparison. The experimental results demonstrate that the detection accuracies of heart rate and respiration rate of the belt are about 1.5 and 0.7 bpm, respectively. The accuracy of 97.2% is achieved by the proposed snoring recognition method. In addition, as for 2-stage analysis, the sensitivities of awake and asleep stages are 90.2% and 100%, respectively; meanwhile, the corresponding accuracy of sleep stages prediction is as high as 95.1%. However, as for 4-stage analysis, the sensitivities of awake, rapid eye movement, light sleep, and deep sleep stages are 90.2%, 77.1%, 78.1%, and 73.5%, respectively; meanwhile, the corresponding accuracy of sleep stages prediction decreases to 79.7%. In general, the test results indicate that vital signs detection, snoring recognition, and sleep stages classification based on the sleep monitoring belt are feasible and effective. Hence, this smart flexible belt can be widely used for sleep monitoring at home due to low cost and high performance.

I. Introduction

Recently, there are more and more people with sleep disorders, and the decline of sleep quality makes most people disturbed and anxious [1]. Obtrusive sleep apnea (OSA) is one of the most important sleep disorders, which has a great impact on the sleep quality [2]. Sleep quality is related to age [3], cardiovascular, neurological, and psychosomatic conditions, which reflects the homeostasis status of autonomic nervous system (ANS) organization and circadian rhythms [4]. ANS is composed of the sympathetic and the parasympathetic nervous systems. Sleep stages mainly include rapid eye movement (REM) and various non-REM stages (NREM). NREM stages comprise awake, light sleep, and deep sleep stages [5]. Given that it is of great significance to evaluate the sleep quality, more and more research institutes pay attention to it and have proposed some effective and feasible methods of Internet of Things (IoT), including contact and noncontact, wearable, and nonwearable sleep monitoring schemes.