We discovered that impulse-radio ultra-wideband (IR-UWB) radar could recognize cardiac motions in a non-contact fashion. Therefore, we measured the heart rate (HR) and rhythms using an IR-UWB radar sensor and evaluated the validity and reliability of the measurements in comparison to electrocardiography. The heart beats were measured in 6 healthy volunteers (18 samples) with normal sinus rhythm (NSR) and 16 patients (36 samples) with atrial fibrillation (AF) using both an IR-UWB radar sensor and electrocardiography simultaneously. The participants hold their breath for 20 seconds during the data acquisition. In subjects with NSR, there was excellent agreement of HR (intraclass correlation coefficient [ICC] 0.856), average R-R interval (ICC 0.997) and individual R-R intervals between the two methods (ICC 0.803). In subjects with AF, HR (ICC 0.871) and average R-R interval (ICC 0.925) from the radar sensor also agreed well with those from electrocardiography, though there was a small disagreement in the individual R-R intervals between the two methods (ICC 0.697). The rhythms computed by the signal-processing algorithm showed good agreement between the two methods (Cohen’s Kappa 0.922). The IR-UWB radar sensor is precise and accurate for assessing HR and rhythms in a non-contact fashion.

While full-night polysomnography is the gold standard for the diagnosis of obstructive sleep apnea, its limitations include a high cost and first-night effects. This study developed an algorithm for the detection of respiratory events based on impulse-radio ultra-wideband radar and verified its feasibility for the diagnosis of obstructive sleep apnea. A total of 94 subjects were enrolled in this study (23 controls and 24, 14, and 33 with mild, moderate, and severe obstructive sleep apnea, respectively). Abnormal breathing detected by impulse-radio ultra-wideband radar was defined as a drop in the peak radar signal by ≥30% from that in the pre-event baseline. We compared the abnormal breathing index obtained from impulse-radio ultra-wideband radar and apnea–hypopnea index (AHI) measured from polysomnography. There was an excellent agreement between the Abnormal Breathing Index and AHI (intraclass correlation coefficient = 0.927). The overall agreements of the impulse-radio ultra-wideband radar were 0.93 for Model 1 (AHI ≥ 5), 0.91 for Model 2 (AHI ≥ 15), and 1 for Model 3 (AHI ≥ 30). Impulse-radio ultra-wideband radar accurately detected respiratory events (apneas and hypopneas) during sleep without subject contact. Therefore, impulse-radio ultra-wideband radar may be used as a screening tool for obstructive sleep apnea.

This study aimed to investigate the sex-specific effects of anthropometric profiles on the occurrence and severity of obstructive sleep apnea (OSA). We evaluated 151 patients with suspected OSA undergoing polysomnography and anthropometric measurements such as body mass index (BMI), neck and waist circumference (NC and WC), and waist–hip ratio (WHR). In men, NC (P = .006), WC (P = .035), and WHR (P = .003) were significantly increased in OSA and all were significantly correlated with apnea hypopnea index (AHI). However, in female OSA patients, BMI (P = .05), WC (P = .008), and WHR (P = .001) were elevated, but only WHR was significantly correlated with AHI. Correlation analyses showed significant correlations between NC and other anthropometric indexes in men but not in women. The receiver operating characteristic curves revealed that NC and WHR in men, and WHR in women, were significant in both model 1 (AHI ≥ 5) and model 2 (AHI ≥ 15). Waist–hip ratio is the most reliable correlate of OSA in both sexes. Neck circumference is an independent risk factor for male, but not for female, OSA patients. These different aspects of obesity may contribute to the pathogenesis of OSA and provide helpful guidance in the screening of OSA.