Abstract
Vital signs monitoring in physical activity (PA) is of great significance in daily healthcare. Impulse Radio Ultra-WideBand (IR-UWB) radar provides a contactless vital signs detection approach with advantages in range resolution and penetration. Several researches have verified the feasibility of IR-UWB radar monitoring when the target keeps still. However, various body movements are induced by PA, which lead to severe signal distortion and interfere vital signs extraction. To address this challenge, a novel joint chest–abdomen cardiopulmonary signal estimation approach is proposed to detect breath and heartbeat simultaneously using IR-UWB radars. The movements of target chest and abdomen are detected by two IR-UWB radars, respectively. Considering the signal overlapping of vital signs and body motion artifacts, Empirical Wavelet Transform (EWT) is applied on received radar signals to remove clutter and mitigate movement interference. Moreover, improved EWT with frequency segmentation refinement is applied on each radar to decompose vital signals of target chest and abdomen to vital sign-related sub-signals, respectively. After that, based on the thoracoabdominal movement correlation, cross-correlation functions are calculated among chest and abdomen sub-signals to estimate breath and heartbeat. The experiments are conducted under three kinds of PA situations and two general body movements, the results of which indicate the effectiveness and superiority of the proposed approach.
Highlights
Physical activity (PA) is of great significance in daily healthcare; it improves the level of both mental and physiological health and reduces the risk of several medical illnesses.It is reported that the ratio of sudden cardiac death is approximately 1 in 50,000 athleteyears for the young athletes, and even reaches 1 in 5000 for risky groups [1]
In order to further evaluate the performance of movement interference alleviation based on Empirical Wavelet Transform (EWT), moving average filtering (MAF) [29], and Singular Value Decomposition (SVD) [43] are introduced as comparisons
Compared with the proposed approach applying on the upper radar, the average accuracy improves 5.3% using two radars simultaneously, which illustrates the superiority for heartbeat estimation using two radars simultaneously
Summary
Physical activity (PA) is of great significance in daily healthcare; it improves the level of both mental and physiological health and reduces the risk of several medical illnesses.It is reported that the ratio of sudden cardiac death is approximately 1 in 50,000 athleteyears for the young athletes, and even reaches 1 in 5000 for risky groups [1]. Conventional vital signs monitoring methods during exercising are based on wearable devices, such as plethysmography (PPG) sensors [2] and piezoresistive sensors [3]. These devices are attached to human body directly, which lead to body swelling and discomfort when wearing overtime. The usage of vision-based sensors is strictly limited by lighting condition, let alone the inevitable privacy issues. Thermalbased sensors provide another solution for physiological signal detection and analysis [5]
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