[Wearable devices: Perspectives on assessing and monitoring human physiological status].

This review article aims to explore the major challenges that the healthcare system is currently facing and propose a new paradigm shift that harnesses the potential of wearable devices and novel theoretical frameworks on health and disease. Lifestyle-induced diseases currently account for a significant portion of all healthcare spending, with this proportion projected to increase with population aging. Wearable devices have emerged as a key technology for implementing large-scale healthcare systems focused on disease prevention and management. Advancements in miniaturized sensors, system integration, the Internet of Things, artificial intelligence, 5G, and other technologies have enabled wearable devices to perform high-quality measurements comparable to medical devices. Through various physical, chemical, and biological sensors, wearable devices can continuously monitor physiological status information in a non-invasive or minimally invasive way, including electrocardiography, electroencephalography, respiration, blood oxygen, blood pressure, blood glucose, activity, and more. Furthermore, by combining concepts and methods from complex systems and nonlinear dynamics, we developed a novel theory of continuous dynamic physiological signal analysis-dynamical complexity. The results of dynamic signal analyses can provide crucial information for disease prevention, diagnosis, treatment, and management. Wearable devices can also serve as an important bridge connecting doctors and patients by tracking, storing, and sharing patient data with medical institutions, enabling remote or real-time health assessments of patients, and providing a basis for precision medicine and personalized treatment. Wearable devices have a promising future in the healthcare field and will be an important driving force for the transformation of the healthcare system, while also improving the health experience for individuals.

Development of a quantitative measurement on visual clutter in see through display.

Objective: With the wide use of transmission displays to improve operation performance, the display information highlights clutter because of the contradiction between the massive amount of information and limited display area. Our study aimed to develop a quantitative measurement for declutter design and appraisal. Methods: Using the ergonomics research system of characters and symbols in a see-through cockpit display, we set the simulated flight task interface at four pixel scale levels by enlarging all the display elements in a certain ratio. Flight task videos of 12 clutter degrees were recorded using each flight interface matched with three flight scene complexity levels. A total of 60 pilots completed the visual search tasks in the flight task video while the eye tracker was used to record the view path in real time. Visual search performance was analyzed to study the effect of various clutter factors and levels on pilots' performance in visual search tasks, and acquire quantitative clutter measure parameters. Results: GLM univariate test revealed that there were significant differences among the fixation time in areas of interest (AOI), total Fixation point number, total fixation time at four pixel scale levels, and three flight scene complexity levels (P < 0.05). Visual search performance declined after the cutoff point, while the clutter degree increased. According to the visual search performance data, the recommend feature congestion upper pixel number limit in a 600*800 display was 18,576, and the pixel ratio was 3.87%. Conclusion: A quantitative measurement for declutter design and appraisal of cockpit displays was developed, which can be used to support see-through display design.

Motor Imagery-Related Changes of Neural Oscillation in Unilateral Lower Limb Amputation.

An amputation is known to seriously affect patient quality of life. This study aimed to investigate changes in neural activity in amputees during the postoperative period using neural electrophysiological techniques. In total, 14 patients with left lower limb amputation and 18 healthy participants were included in our study. All participants were required to perform motor imagery paradigm tasks while electroencephalogram (EEG) data were recorded. Data analysis results indicated that the beta frequency band showed significantly decreased oscillatory activity in motor imaging-related brain regions such as the frontal lobe and the precentral and postcentral gyri in amputees. Furthermore, the functional independent component analysis (fICA) value of neural oscillation negatively correlated with the C4 electrode power value of the motor imagery task in amputees (p < 0.05). Therefore, changes in neural oscillations and beta frequency band in motor imagery regions may be related to brain remodeling in amputees.

[Design and preliminary validation of a ubiquitous and wearable physiological monitoring system].

To achieve continuously physiological monitoring on hospital inpatients, a ubiquitous and wearable physiological monitoring system SensEcho was developed. The whole system consists of three parts: a wearable physiological monitoring unit, a wireless network and communication unit and a central monitoring system. The wearable physiological monitoring unit is an elastic shirt with respiratory inductive plethysmography sensor and textile electrocardiogram (ECG) electrodes embedded in, to collect physiological signals of ECG, respiration and posture/activity continuously and ubiquitously. The wireless network and communication unit is based on WiFi networking technology to transmit data from each physiological monitoring unit to the central monitoring system. A protocol of multiple data re-transmission and data integrity verification was implemented to reduce packet dropouts during the wireless communication. The central monitoring system displays data collected by the wearable system from each inpatient and monitors the status of each patient. An architecture of data server and algorithm server was established, supporting further data mining and analysis for big medical data. The performance of the whole system was validated. Three kinds of tests were conducted: validation of physiological monitoring algorithms, reliability of the monitoring system on volunteers, and reliability of data transmission. The results show that the whole system can achieve good performance in both physiological monitoring and wireless data transmission. The application of this system in clinical settings has the potential to establish a new model for individualized hospital inpatients monitoring, and provide more precision medicine to the patients with information derived from the continuously collected physiological parameters.

A pilot application of Korotkoff sound delay time in evaluating cardiovascular status.

BACKGROUND: Korotkoff sounds have been used to measure systolic and diastolic arterial blood pressures noninvasively for over 100 years. However, most of the research concerning the Korotkoff sound were focused on the origin and frequency component analyzing the Korotkoff sound signal. OBJECTIVE: To show that the occurrence time of the Korotkoff sounds for each cardiac cycle demonstrates a characteristic value during the cuff deflating process of blood pressure measurement. METHODS: The Korotkoff sound delay time (KDT) decreases as the cuff pressure P deflates and KDT is a function of arterial transmural pressure. In the present research, an experiment system was established to explore the relationship between the KDT and the cuff pressure in different subjects. RESULTS: A pilot experiment was conducted to obtain different subjects' KDTs and investigate the relationship between KDT and cuff pressure. CONCLUSION: The relationship between KDT and invasive blood pressure was also studied and its potential application in detection of cardiovascular status was discussed.

Detection of genioglossus myoelectric activity using ICA of multi-channel mandible sEMG.

BACKGROUND: Genioglossus myoelectric activity is of great significance in evaluating clinical respiratory function. However, there is a tradeoff in genioglossus EMG measurement with respect to accuracy versus convenience. OBJECTIVE: This paper presents a way to separate the characteristics of genioglossus myoelectric activity from multi-channel mandible sEMG through independent component analysis. METHODS: First, intra-oral genioglossus EMGgenioglossus EMG and three-channel mandible sEMG were recorded simultaneously. The FastICA algorithm was applied to three independent components from the sEMG signals. Then the independent components with the intra-oral genioglossus EMG were compared by calculating the Pearson correlation coefficient between them. RESULTS: An examination of 60 EMG samples showed that the FastICA algorithm was effective in separating the characteristics of genioglossus myoelectric activity from multi-channel mandible sEMG. The results of analysis were coincident with clinical diagnosis through intra-oral electrodes. CONCLUSIONS: Genioglossus myoelectric activity can be evaluated accurately by multi-channel mandible sEMG, which is non-invasive and easy to record.

Reflective oxygen saturation monitoring at hypothenar and its validation by human hypoxia experiment.

BACKGROUND: Pulse oxygen saturation (SpO2) is an important parameter for healthcare, and wearable sensors and systems for SpO2 monitoring have become increasingly popular. The aim of this paper is to develop a novel SpO2 monitoring system, which detects photoplethysmographic (PPG) signals at hypothenar with a reflection-mode sensor embedded into a glove. METHODS: A special photo-detector section was designed with two photodiodes arranged symmetrically to the red and infrared light-emitting diodes (LED) to enhance the signal quality. The reflective sensor was placed in a soft silicon substrate sewn in a glove to fit the surface of the hypothenar. To lower the power consumption, the LED driving current was reduced and energy-efficient electronic components were applied. The performance for PPG signal detection and SpO2 monitoring was evaluated by human hypoxia experiments. Accelerometer-based adaptive noise cancellation (ANC) methods applying the least mean squares (LMS) and recursive least squares (RLS) algorithms were studied to suppress motion artifact. RESULTS: A total of 20 subjects participated in the hypoxia experiment. The degree of comfort for wearing this system was accepted by them. The PPG signals were detected effectively at SpO2 levels from about 100-70%. The experiment validated the accuracy of the system was 2.34%, compared to the invasive measurements. Both the LMS and RLS algorithms improved the performance during motion. The total current consumed by the system was only 8 mA. CONCLUSIONS: It is feasible to detect PPG signal and monitor SpO2 at the location of hypothenar. This novel system can achieve reliable SpO2 measurements at different SpO2 levels and on different individuals. The system is light-weighted, easy to wear and power-saving. It has the potential to be a solution for wearable monitoring, although more work should be conducted to improve the motion-resistant performance significantly.

Linear and nonlinear dynamics of heart rate variability in the process of exposure to 3600 m in 10 min.

Acute hypoxia activates several autonomic mechanisms, mainly in cardiovascular system and respiratory system. The influence of acute hypoxia on linear and nonlinear heart rate variability (HRV) has been studied, but the parameters in the process of hypoxia are still unclear. Although the changes of HRV in frequency domain are related to autonomic responses, how nonlinear dynamics change with the decrease of ambient atmospheric pressure is unknown either. Eight healthy male subjects were exposed to simulated altitude from sea level to 3600 m in 10 min. HRV parameters in frequency domain were analyzed by wavelet packet transform (Daubechies 4, 4 level) followed by Hilbert transform to assess the spectral power of modified low frequency (0.0625-0.1875 Hz, LFmod), modified high frequency (0.1875-0.4375 Hz, HFmod), and the LFmod/HFmod ratio in every 1 min. Nonlinear parameters were also quantified by sample entropy (SampEn) and short term fractal correlation exponent (α1) in the process. Hypoxia was associated with the depression of both LFmod and HFmod component. They were significantly lower than that at sea level at 3600 m and 2880 m respectively (both p < 0.05). The LFmod/HFmod ratio was acutely increased at 3600 m (p < 0.05). SampEn was significantly declined at 2880 m (p < 0.05). Although the value of α1 was close to 1, it changed not significantly in the whole process. These results indicated hypoxia gradually attenuated both spectral HRV parameters and SampEn. The balance of sympathovagal shifted towards sympathetic dominance at a certain altitude. Monitoring linear and nonlinear HRV parameters continuously in the process of hypoxia would be an effective way to evaluate the different regulatory mechanisms of autonomic nervous system.

A simplified computer model of cardiovascular system with an arm branch.

Non-invasive pressure simulators that regenerate oscillometric waveforms promise an alternative to expensive clinical trials for validating oscillometric noninvasive blood pressure devices. However, existing simulators only provide oscillometric pressure in cuff and thus have a limited accuracy. It is promising to build a physical simulator that contains a synthetic arm with a built-in brachial artery and an affiliated hydraulic model of cardiovascular system. To guide the construction of this kind of simulator, this paper presents a computer model of cardiovascular system with a relatively simple structure, where the distribution of pressures and flows in aorta root and brachial artery can be simulated, and the produced waves are accordant with the physical data. This model can be used to provide the parameters and structure that will be needed to build the new simulator.

Effects of acute hypoxia on heart rate variability, sample entropy and cardiorespiratory phase synchronization.

BACKGROUND: Investigating the responses of autonomic nervous system (ANS) in hypoxia may provide some knowledge about the mechanism of neural control and rhythmic adjustment. The integrated cardiac and respiratory system display complicated dynamics that are affected by intrinsic feedback mechanisms controlling their interaction. To probe how the cardiac and respiratory system adjust their rhythms in different simulated altitudes, we studied heart rate variability (HRV) in frequency domain, the complexity of heartbeat series and cardiorespiratory phase synchronization (CRPS) between heartbeat intervals and respiratory cycles. METHODS: In this study, twelve male subjects were exposed to simulated altitude of sea level, 3000 m and 4000 m in a hypobaric chamber. HRV was assessed by power spectral analysis. The complexity of heartbeat series was quantified by sample entropy (SampEn). CRPS was determined by cardiorespiratory synchrogram. RESULTS: The power spectral HRV indices at all frequency bands depressed according to the increase of altitude. The SampEn of heartbeat series increased significantly with the altitude (P < 0.01). The duration of CRPS epochs at 3000 m was not significantly different from that at sea level. However, it was significantly longer at 4000 m (P < 0.01). CONCLUSIONS: Our results suggest the phenomenon of CRPS exists in normal subjects when they expose to acute hypoxia. Further, the autonomic regulation has a significantly stronger influence on CRPS in acute hypoxia. The changes of CRPS and HRV parameters revealed the different regulatory mechanisms of the cardiac and respiratory system at high altitude.

Determination of delay time in individual transfer function for central aortic pressure reconstruction.

In previous research, time-delay (Δt) was a more important parameter than the reflection coefficient in the individual transfer function of central aortic pressure reconstruction. The Δt can be obtained by electrocardiography (ECG) or phonocardiography (PCG). Because the pre-ejection period remains an uncertain factor, the present study used ECG and PCG to define the delay time and analyzed the accuracy of the reconstruction results. The Δt pre is the actual delay time derived from the aorta to the carotid pressure wave, Δt PCG is the time delay between the aortic valve component of the second heart sound and the dicrotic incisura of the carotid pressure wave, and Δt ECG represents the delay from the interval of the ECG R-peak to the foot of the carotid pressure wave. Compared with the measured aortic pressure, the reconstruction result obtained by Δt=Δt PCG slightly differed from the best result estimated by Δt=Δt pre. However, the differences between the result obtained by Δt=Δt ECG and the best result were significant in terms of the diastolic blood pressure, and pulse pressure, and especially in terms of the augmentation index and root-mean-square-error. Thus, the Δt should be determined by PCG for central aortic pressure reconstruction in practice.

[Efficient method for analyzing absorbed ingredients of traditional Chinese medicine genitana macrophyllae radix].

In present study, a method for analyzing the absorbed ingredients of traditional Chinese medicine QinJiao has been developed. A rat everted gut sac (EGS) model has been established, and the transporting capacity of gut sacs was identified by histological examinations. The ingredients including loganic acid, sweroside, gentiopicroside, and swertiamarian in serosal solution absorbed by active transport of rat everted ileum and jejunum from Qinjiao extraction were determined using an HPLC method. Histological integrality of the gut sacs remains perfect and the active transport activity of them is normal within 45 min of the experiment. The HPLC method employed in this study presents high specificity and good correlation. The relative standard deviation of precision of this method is less than 5.5%. Extraction recovery of samples is more than 90%. And stability of the samples in room temperature is perfect. Eight ingredients of Qinjiao absorbed in serosal solution are identified. Furthermore, concentration of Qinjiao extraction significantly affects accumulated absorption and absorption coefficient of the ingredients. However, there is no significant impact on the accumulated absorption and absorption coefficient by diverse of everted gut sections. From above, the EGS techniques might be an efficient method, which can be employed for investigation of absorbed ingredients of Traditional Chinese Medicines.

Noninvasive measurement of beat-to-beat arterial blood pressure by the Korotkoff sound delay time.

OBJECTIVE: To propose a novel noninvasive beat-to-beat arterial blood pressure measurement method based on the Korotkoff sound delay time (KDT) and evaluate its accuracy in preliminary experiments. METHODS: KDT decreases as the cuff pressure P deflates, which can be described by a function KDT=f (P). Actually, KDT is a function of arterial transmural pressure. Therefore, the variation in blood pressure can be obtained by the transmural pressure, which is estimated by the KDT. Holding the cuff pressure at an approximate constant pressure between systolic pressure and diastolic pressure, the variation in blood pressure ΔEBP between successive heartbeats can be estimated according to KDT and f'(p), which represents the variation of KDT corresponding to unit pressure. Then the blood pressure for each heartbeat can be obtained by accumulating the ΔEBP. Invasive and noninvasive blood pressure values of six participants were measured simultaneously to evaluate the method. RESULTS: The average of the correlation coefficients between the invasive mean arterial pressure (MAP) and the KDT for six participants was -0.91. The average of the correlation coefficients between the invasive MAP and the estimated mean blood pressure (EBP) was 0.92. The mean difference between EBP and MAP was 0.51 mmHg, and the SD was 2.65 mmHg. The mean blood pressure estimated by the KDT is consistent with the invasive MAP. CONCLUSION: The beat-to-beat blood pressure estimated by KDT provides an accurate estimate of MAP in the preliminary experiments and represents a potential acceptable alternative to invasive blood pressure monitoring during laboratory studies.

[Research, design and application of model NSE-1 neck muscle training machine for pilots].

Pain in the cervical region of air force pilots, who are exposed to high G-forces, is a specifically occupational health problem. To minimize neck problems, the cervical muscles need specific strength exercise. It is important that the training for the neck must be carried out with optimal resistance in exercises. The model NSE-1 neck training machine for pilots was designed for neck strengthening exercises under safe and effective conditions. In order to realize the functions of changeable velocity and resistant (CVR) training and neck isometric contractive exercises, the techniques of adaptive hydraulics, sensor, optic and auditory biological feedback, and signal processing were applied to this machine. The training system mainly consists of mechanical parts (including the chair of flexion and extension, the chair of right and left lateral flexion, the components of hydraulics and torque transformer, etc.), and the software of signal processing and biological feedback. Eleven volunteers were selected for the experiments of neck isometric contractive exercises, three times a week for 6 weeks, where CVR training (flexion, extension, right, left lateral flexion) one time a week. The increase in relative strength of the neck (flexion, extension, left and right lateral flexion) was 70.8%, 83.7%, 78.6% and 75.2%, respectively after training. Results show that the strength of the neck can be increased safely, effectively and rapidly with NSE-1 neck training machine to perform neck training.

Improving auscultatory blood pressure measurement with electronic and computer technology: the visual auscultation method.

BACKGROUND: The auscultatory method is used as the reference standard in all prevalent protocols for validation of noninvasive blood pressure measuring devices, and a validation study is essentially based on the comparison between the device and observer measurements. Thus, the objectivity and accuracy of observer measurements are crucial to the validation result. METHODS: To provide observers with more objective information about an auscultatory measurement so that sufficient information to make measurements with greater potential objectivity and accuracy can be available, a computerized data acquisition and analysis system has been developed. It cannot only acquire and store Korotkoff sound, cuff pressure, and oscillometric pulse signals, as well as the sphygmomanometer image, but it also can display the waveforms of the three signals and the sphygmomanometer video while playing the synchronous Korotkoff sounds. With this system, observers can make their measurements via the visual auscultation method, that is to say, by watching those waveforms, instead of the sphygmomanometer, while listening for synchronized Korotkoff sounds. The system was validated according to the International Protocol (IP). RESULTS: The result showed that all the differences between system measurements by the visual auscultation method and observer measurements by the conventional auscultatory method were within 4 mm Hg. CONCLUSIONS: The visual auscultation method achieved a high degree of accuracy, and human observers can be replaced by the system in the validation study of blood pressure measuring devices.

[Detecting sleep apnea/hypopnea events with a wearable respiratory inductive plethysmograph system].

The wearable respiratory inductive plethysmograph(RIP) system is a non-intrusive respiratory monitoring system. Sleep monitoring was performed on 9 human subjects suspected of having sleep apnea hypersomnolence syndrome (SAHS) and 7 healthy volunteers using both the wearable RIP system and the conventional polysomnography(PSG), and the sensitivity and specificity of the wearable RIP system were analyzed by comparison with the PSG results. According to the characteristic of the wearable RIP system in detecting sleep apnea/hypopnea event, the diagnostic criteria of sleep apnea/hypopnea event were put forward. All subjects with SAHS diagnosed by the wearable RIP were confirmed by PSG,the sensitivity and specificity of the wearable RIP system for detecting sleep apnea/hypopnea events were 99.0% and 94.6% respectively. The wearable RIP system can be used reliably in detecting sleep apnea/hypopnea events. This system can be used at home for detecting the sleep apnea/hypopnea events non-intrusively.

[Review of driver fatigue/drowsiness detection methods].

Driver fatigue/drowsiness is one of the important causes of serious traffic accidents and results in so many people deaths or injuries, but also substantial directly and indirectly economic expenses. Therefore, many countries make great effort on how to detect drowsiness during driving. In this paper, we introduce the recent developments of driver fatigue/drowsiness detection technology of world wide and try to classify the existing methods into several kinds according to different features measured, and analyzed. Finally, the challenges faced to fatigue/drowsiness detection technology and the development trend are presented.

[Correlation between oral airflow ratio and craniofacial, airway and dental morphology].

OBJECTIVE: To investigate the correlation between airflow ratio and craniofacial, airway and dental morphology. METHODS: Seventy-two subjects aged 11 to 14 years were selected. The airflow ratio was measured by the system for the simultaneous measurement of oral and nasal respiration. Eighty-six variables of craniofacial, airway and dental morphology were acquired based on cephalometric films and models, from which 16 significant variables were selected. Multiple regression analysis (backward) and linear regression analysis were carried out in order to acquire morphological variables that had closer correlation with the airflow ratio. RESULTS: Four variables were found to have closer correlated association with the airflow ratio (P < 0.05), which were ANS-Me/N-Me, Ar-Go-Me, P-T, SHJK orderly and the coefficients were 3.359, 0.012, -0.013 and -0.021, respectively. CONCLUSIONS: Craniofacial morphology was related to the respiratory mode.