A Wearable, Multi-Frequency Device to Measure Muscle Activity Combining Simultaneous Electromyography and Electrical Impedance Myography.

The detection of muscle contraction and the estimation of muscle force are essential tasks in robot-assisted rehabilitation systems. The most commonly used method to investigate muscle contraction is surface electromyography (EMG), which, however, shows considerable disadvantages in predicting the muscle force, since unpredictable factors may influence the detected force but not necessarily the EMG data. Electrical impedance myography (EIM) investigates the change in electrical impedance during muscle activities and is another promising technique to investigate muscle functions. This paper introduces the design, development, and evaluation of a device that performs EMG and EIM simultaneously for more robust measurement of muscle conditions subject to artifacts. The device is light, wearable, and wireless and has a modular design, in which the EMG, EIM, micro-controller, and communication modules are stacked and interconnected through connectors. As a result, the EIM module measures the bioimpedance between 20 and 200 Ω with an error of less than 5% at 140 SPS. The settling time during the calibration phase of this module is less than 1000 ms. The EMG module captures the spectrum of the EMG signal between 20-150 Hz at 1 kSPS with an SNR of 67 dB. The micro-controller and communication module builds an ARM-Cortex M3 micro-controller which reads and transfers the captured data every 1 ms over RF (868 Mhz) with a baud rate of 500 kbps to a receptor connected to a PC. Preliminary measurements on a volunteer during leg extension, walking, and sit-to-stand showed the potential of the system to investigate muscle function by combining simultaneous EMG and EIM.

Evaluation and Application of a Customizable Wireless Platform: A Body Sensor Network for Unobtrusive Gait Analysis in Everyday Life.

Body sensor networks (BSNs) represent an important research tool for exploring novel diagnostic or therapeutic approaches. They allow for integrating different measurement techniques into body-worn sensors organized in a network structure. In 2011, the first Integrated Posture and Activity Network by MedIT Aachen (IPANEMA) was introduced. In this work, we present a recently developed platform for a wireless body sensor network with customizable applications based on a proprietary 868MHz communication interface. In particular, we present a sensor setup for gait analysis during everyday life monitoring. The arrangement consists of three identical inertial measurement sensors attached at the wrist, thigh, and chest. We additionally introduce a force-sensitive resistor integrated insole for measurement of ground reaction forces (GRFs), to enhance the assessment possibilities and generate ground truth data for inertial measurement sensors. Since the 868MHz is not strongly represented in existing BSN implementations, we validate the proposed system concerning an application in gait analysis and use this as a representative demonstration of realizability. Hence, there are three key aspects of this project. The system is evaluated with respect to (I) accurate timing, (II) received signal quality, and (III) measurement capabilities of the insole pressure nodes. In addition to the demonstration of feasibility, we achieved promising results regarding the extractions of gait parameters (stride detection accuracy: 99.6±0.8%, Root-Mean-Square Deviation (RMSE) of mean stride time: 5ms, RMSE of percentage stance time: 2.3%). Conclusion: With the satisfactory technical performance in laboratory and application environment and the convincing accuracy of the gait parameter extraction, the presented system offers a solid basis for a gait monitoring system in everyday life.

Neurogeriatrics-a vision for improved care and research for geriatric patients with predominating neurological disabilities.

Geriatric medicine is a rapidly evolving field that addresses diagnostic, therapeutic and care aspects of older adults. Some disabilities and disorders affecting cognition (e.g. dementia), motor function (e.g. stroke, Parkinson's disease, neuropathies), mood (e.g. depression), behavior (e.g. delirium) and chronic pain disorders are particularly frequent in old subjects. As knowledge about these age-associated conditions and disabilities is steadily increasing, the integral implementation of neurogeriatric knowledge in geriatric medicine and specific neurogeriatric research is essential to develop the field. This article discusses how neurological know-how could be integrated in academic geriatric medicine to improve care of neurogeriatric patients, to foster neurogeriatric research and training concepts and to provide innovative care concepts for geriatric patients with predominant neurological conditions and disabilities.

Balance and mobility in geriatric patients : Assessment and treatment of neurological aspects.

BACKGROUND: Personal autonomy in advanced age critically depends on mobility in the environment. Geriatric patients are often not able to walk safely with sufficient velocity. In many cases, multiple factors contribute to the deficit. Diagnostic identification of single components enables a specific treatment. OBJECTIVE: This article describes the most common neurological causes of imbalance and impaired gait that are relevant for a pragmatic approach for the assessment of deficits in clinical and natural environments taking into account the physiology of balance and gait control, typical morbidities in older people and the potential of innovative assessment technologies. MATERIAL AND METHODS: Expert opinion based on a narrative review of the literature and with reference to selected research topics. RESULTS AND DISCUSSION: Common neurological causes of impaired balance and mobility are sensory deficits (reduced vision, peripheral neuropathy, vestibulopathy), neurodegeneration in disorders with an impact on movement control and motoric functions (Parkinsonian syndromes, cerebellar ataxia, vascular encephalopathy) and functional (psychogenic) disorders, particularly a fear of falling. Clinical tests and scores in laboratory environments are complemented by the assessment in the natural environment. Wearable sensors, mobile smartphone-based assessment of symptoms and functions and adopted strategies for analysis are currently emerging. Use of these data enables a personalized treatment. Furthermore, sensor-based assessment ensures that effects are measured objectively.

Principles of the prolactin/vasoinhibin axis.

The hormonal family of vasoinhibins, which derive from the anterior pituitary hormone prolactin, are known for their inhibiting effects on blood vessel growth, vasopermeability, and vasodilation. As pleiotropic hormones, vasoinhibins act in multiple target organs and tissues. The generation, secretion, and regulation of vasoinhibins are embedded into the organizational principle of an axis, which integrates the hypothalamus, the pituitary, and the target tissue microenvironment. This axis is designated as the prolactin/vasoinhibin axis. Disturbances of the prolactin/vasoinhibin axis are associated with the pathogenesis of retinal and cardiac diseases and with diseases occurring during pregnancy. New phylogenetical, physiological, and clinical implications are discussed.

C-terminal agrin fragment (CAF) reflects renal function in patients suffering from severe sepsis or septic shock.

BACKGROUND: One of the main causes of acute kidney injury (AKI) in patients treated on an intensive care unit (ICU) is sepsis. The identification of new biomarkers indicating the early development and future course of AKI are of utmost medical interest. The C-terminal agrin fragment (CAF) is measurable in blood serum and might reflect kidney function. Therefore, this study evaluates CAF in patients presenting to an internal ICU with severe sepsis or septic shock. Serum levels of CAF are correlated with biomarkers of kidney function, markers of systemic inflammation, and the presence of AKI and renal replacement therapy (RRT). METHODS: 61 patients suffering from severe sepsis or septic shock were included during the first 24 hours of ICU treatment and blood samples for biomarker measurements, i.e., CAF, creatinine, cystatin C, procalcitonin (PCT), interleukin 6, C reactive protein (CRP), and white blood cells (WBC) were collected on the first day of intensive care treatment. The number of RRT days and the incidence of AKI were documented. RESULTS: 13% of the patients (8/61) suffered from SIRS/sepsis, 20% (12/61) from severe sepsis, and 67% (41/61) from septic shock. Serum levels of CAF significantly correlated with creatinine (r = 0.623, p < 0.001) and cystatin C (r = 0.578, p < 0.001). Multiple linear regression analyses adjusting CAF for inflammatory parameters (i.e., WBC, CRP, interleukin 6, PCT), age, and gender showed a strong correlation between CAF and creatinine (r = 0.643, p < 0.001). Serum levels of CAF were significantly associated with the need of RRT (area under the curve (AUC) = 0.772, 95% CI: 0.641-0.903, p = 0.002) and the incidence of AKI (AUC = 0.721, 95% CI: 591-0.850, p = 0.004) as indicated by ROC analysis. CONCLUSIONS: In patients suffering from severe sepsis and septic shock, serum levels of CAF were significantly associated with kidney function and RRT and were not influenced by severe septic conditions.

C-reactive protein and the acute phase reaction in geriatric patients.

The C-reactive protein (CRP), first described as a serum component capable of precipitating the C-polysaccharide of pneumococci, is one of the most important proteins because the serum concentration rises in the acute phase reaction. The acute phase reaction is the nonspecific reaction of the body to noxious stimuli of the most varied kinds, such as infections, burns, neoplasms and tissue trauma. The CRP is synthesized in liver parenchymal cells by cytokines which are derived from stimulated leucocytes and released into the circulation. Because of its molecular structure and in synergy with the complement system, it is able to precipitate and/or lyse microorganisms, thereby rendering them harmless. Measurement of the serum CRP concentration can provide important information with respect to the diagnosis and monitoring of treatment. Due to immunosenescence in geriatric patients the synthesis of CRP appears to be limited to inflammatory stimuli; however, this phenomenon does not appear to be of major clinical relevance. Despite the introduction of new parameters of the acute phase reaction, sometimes with better performance, such as interleukin-6, procalcitonin and the soluble endotoxin receptor sCD14, measurement of CRP for diagnosis and treatment monitoring is still justified even in geriatric patients as testing is rapid, economic and nearly ubiquitously available round the clock. Biochemical markers of the acute phase reaction should always be interpreted together with the clinical picture and their specific limitations.

Vitamin d deficiency reduces the immune response, phagocytosis rate, and intracellular killing rate of microglial cells.

Meningitis and meningoencephalitis caused by Escherichia coli are associated with high rates of mortality and neurological sequelae. A high prevalence of neurological disorders has been observed in geriatric populations at risk of hypovitaminosis D. Vitamin D has potent effects on human immunity, including induction of antimicrobial peptides (AMPs) and suppression of T-cell proliferation, but its influence on microglial cells is unknown. The purpose of the present study was to determine the effects of vitamin D deficiency on the phagocytosis rate, intracellular killing, and immune response of murine microglial cultures after stimulation with the Toll-like receptor (TLR) agonists tripalmitoyl-S-glyceryl-cysteine (TLR1/2), poly(I·C) (TLR3), lipopolysaccharide (TLR4), and CpG oligodeoxynucleotide (TLR9). Upon stimulation with high concentrations of TLR agonists, the release of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) was decreased in vitamin D-deficient compared to that in vitamin D-sufficient microglial cultures. Phagocytosis of E. coli K1 after stimulation of microglial cells with high concentrations of TLR3, -4, and -9 agonists and intracellular killing of E. coli K1 after stimulation with high concentrations of all TLR agonists were lower in vitamin D-deficient microglial cells than in the respective control cells. Our observations suggest that vitamin D deficiency may impair the resistance of the brain against bacterial infections.

[Geriatric patient with neurological symptoms and prolonged aPTT]. / Geriatrischer Patient mit neurologischer Symptomatik und verlängerter aPTT.

A 73-year-old man with dementia was referred to our clinic with hypernatremia and volume depletion. New-onset neurogenic dysphagia was likely the reason for both. The patient had chronic embolic strokes on the computed tomography (CT) images. Documentation from previous hospitalizations in different hospitals revealed a repeatedly prolonged activated partial thromboplastin time (aPTT); 5 years prior, antiphospholipid antibody syndrome had already been suspected, but the necessary workup was never completed. We diagnosed the patient with primary antiphospholipid antibody syndrome and initiated therapy with vitamin K antagonists (phenprocoumon) and aspirin.

Does listening to audiobooks affect gait behavior?

BACKGROUND: The effect of listening to audiobooks, podcasts, and other audio files while walking on gait performance has not been well studied. Although the number of audio users is growing annually. Evidence suggests that a posture-first strategy contributes to gait stability in healthy individuals during dual-task conditions, but this effect may be diminished when the cognitive task is consciously prioritized. OBJECTIVES: To study the effect of listening to an audiobook while walking, as a daily life-like dual-task, on spatiotemporal gait parameters. METHODS: Forty young healthy (24.05 ± 3.66) subjects participated in the study. Spatiotemporal gait parameters were measured for 5 min on a treadmill once without (single-task) and once while listening to an audiobook through over-ear headphones (dual-task). Measured parameters included spatiotemporal parameters, gait phases, maximum pressure, and dual-task cost. Data were statistically analyzed using SPSS software. RESULTS: There were no significant differences in any of the studied parameters between the single- and dual-task conditions, even though the subjective cognitive load of listening to audiobooks while walking was high. However, participants with different habits had significant differences in gait phases and maximum pressure. Rare listeners had a shorter stance phase, a longer swing phase, and a higher maximum pressure on the dominant heel. They also had significant differences in dual-task costs. CONCLUSION: No differences in the spatiotemporal gait parameters for walking with and without listening to audiobooks, as a daily life-like dual-task, were observed. However, the difference between participants who listened rarely and participants who listened often may confirm the "posture first" strategy in young healthy people. TRIAL REGISTRATION: DRKS00025837, retrospectively registered on 23.11.2021.

Estimation of Step Length With Wearable Thigh Sensor Using an Unscented Kalman Filter.

The determination of step length, an important gait parameter, has been a challenging task. Although unobtrusive sensors (inertial measurement units) have been developed recently, they cannot facilitate the automatic estimation of step length. In this article, we use a model-based technique to determine the step length using the Unscented Kalman Filter with angular velocity from a gyroscope inside the thigh pocket. We then propose a novel covariance estimation algorithm based on a screening technique that performs a search for the optimal Process Noise Covariance matrix. Upon implementing the Unscented Kalman Filter, the step length is found using the horizontal position of the foot relative to the hip using a patient-independent robust peak detection algorithm. This research article paves the way for algorithms that are computationally much faster than black box methods, with more scope for the development of better algorithms for covariance estimation using the one proposed in this article as a foundation.

Step Length Estimation with Wearable Wrist Sensor using ANN.

Step Length is an important metric that can be used for the analysis and assessment of the gait. Proper dynamical models are not available in current literature associated with the wrist that can adequately determine the step length using recursive estimation techniques. This study presents a method to estimate the step length using angular velocity data from the wrist sensor. The technique maps the dynamical region corresponding to periods of activity of the gait manifested in angular velocity from the inertial measurement unit located at the wrist to that of the thigh using an artificial neural network, upon which an unscented Kalman filter is used to determine the horizontal position of the foot relative to the hip, and consequently, determine step length. The results for Step Length indicate an average accuracy of 81.8% and 91.1% for the young and elderly, respectively, when compared to a reference system, which, in our study, is data from a treadmill.

Noncontact Monitoring of Heart Rate and Heart Rate Variability in Geriatric Patients Using Photoplethysmography Imaging.

OBJECTIVE: Geriatric patients, especially those with dementia or in a delirious state, do not accept conventional contact-based monitoring. Therefore, we propose to measure heart rate (HR) and heart rate variability (HRV) of geriatric patients in a noncontact and unobtrusive way using photoplethysmography imaging (PPGI). METHODS: PPGI video sequences were recorded from 10 geriatric patients and 10 healthy elderly people using a monochrome camera operating in the near-infrared spectrum and a colour camera operating in the visible spectrum. PPGI waveforms were extracted from both cameras using superpixel-based regions of interests (ROI). A classifier based on bagged trees was trained to automatically select artefact-free ROIs for HR estimation. HRV was calculated in the time-domain and frequency-domain. RESULTS: an RMSE of 1.03 bpm and a correlation of 0.8 with the reference was achieved using the NIR camera for HR estimation. Using the RGB camera, RMSE and correlation improved to 0.48 bpm and 0.95, respectively. Correlation for HRV in the frequency-domain (LF/HF-ratio) was 0.50 using the NIR camera and 0.70 using the RGB camera. CONCLUSION: We were able to demonstrate that PPGI is very suitable to measure HR and HRV in geriatric patients. We strongly believe that PPGI will become clinically relevant in monitoring of geriatric patients. SIGNIFICANCE: we are the first group to measure both HR and HRV in awake geriatric patients using PPGI. Moreover, we systematically evaluate the effects of the spectrum (near-infrared vs. visible), ROI, and additional motion artefact reduction algorithms on the accuracy of estimated HR and HRV.

Model-Based Step Length Estimation Using a Pendant-Integrated Mobility Sensor.

The step length is an important parameter in gait analysis. Long-term monitoring applications for gait analysis are often based on inertial measurement units (IMUs) due to their low-cost and unobtrusive nature. Spatial gait parameters, such as step or stride length, are therefore not directly accessible. In this contribution, we focus on model-based algorithms for step length estimation based on a pendant-integrated IMU during slow walking speeds. We present a model-based approach to estimate the step length, which is divided into two successive steps. As the first part of our approach, we present an algorithm for estimation of the vertical displacement of the center of mass (CoM) during gait. Based on this estimate, we present a novel approach to estimate the step length, which we have deduced from a previously published, simplified gait model. The algorithm is compared to a commonly known approach for accelometry-based step length prediction and validated against reference data obtained from a force plate-integrated treadmill for gait analysis during a clinical study with ten healthy subjects. Due to the applicability to gait stability assessment in elderly or gait impaired patients, we focus on slow walking speeds (1-4 km h-1). The presented algorithms outperform the existing approach and the proposed model calculations provide a more accurate prediction. For the vertical displacement, we achieved a precision of 9.3% (CoV) with an RMSE of 1.5 mm in terms of the trajectory amplitude during normal gait patterns. The step length estimation yields satisfying results with a relative prediction error of lower than 10% for walking speeds of 2-4kmh-1.

Hypoglycemia in Older Adults: Time Trends and Treatment Differences in Patients Aged ≥75 Years With Type 2 Diabetes.

OBJECTIVES: Hypoglycemia is a potentially life-threatening drug event under antidiabetic treatment. The aim of the study was to examine time trends in severe hypoglycemia in older adults with type 2 diabetes mellitus (T2DM) and antidiabetic treatment. DESIGN: Multicenter prospective diabetes patient follow-up registry (DPV). SETTING AND PARTICIPANTS: Patients aged ≥75 years with T2DM and documented treatment between 2005 and 2019. METHODS: Outcomes of interest were rates of severe hypoglycemia, diabetes therapy, body mass index, HbA1c, and estimated glomerular filtration rate. Time trends of outcomes were analyzed in the whole cohort and compared between age groups (75-<80, 80-<85, ≥85 years). RESULTS: A total of 136,931 patients from 188 diabetes centers were included. The adjusted HbA1c decreased from 7.3% (95% confidence interval 7.3-7.4) in 2005 to 7.2% (7.2-7.2) in 2019 (P < .001), with no significant difference between age groups (P = .47). Rates of severe hypoglycemia decreased from 6.7 (6.0-7.4) to 4.1 of 100 person-years (3.7-4.5) (P < .001) in the entire population. Patients aged ≥85 years had constantly lower HbA1c levels compared with younger groups (P < .001). Although severe hypoglycemia decreased the most in the ≥85 age group (P < .001), severe hypoglycemia remained consistently higher in this group compared with the 75 to <80 years group (P < .001). CONCLUSIONS AND IMPLICATIONS: During the analyzed time, the risk for severe hypoglycemia decreased. Although drugs with intrinsic risk for hypoglycemia were used less frequently, antidiabetic treatment in older adults should be further improved to continue reducing severe hypoglycemia in this age group, potentially accepting less strict metabolic control and age-specific target ranges.

Estimation of Stride Time Variability in Unobtrusive Long-Term Monitoring Using Inertial Measurement Sensors.

Stride time variability is an important indicator for the assessment of gait stability. An accurate extraction of the stride intervals is essential for determining stride time variability. Peak detection is a commonly used method for gait segmentation and stride time estimation. Standard peak detection algorithms often fail due to additional movement components and measurement noise. A novel algorithm for robust peak detection in inertial sensor signals was proposed in a previous contribution. In this work, we present a novel approach for estimation of stride time variability based on the formerly proposed peak detection algorithm applied to an unobtrusive sensor setup for motion monitoring. The unobtrusive sensor setup includes a wrist sensor, a pocket or belt sensor, and a necklace sensor, all equipped with both accelerometer and gyroscope. The goal of this work is to implement a generalized approach for accurate and robust stride interval determining algorithm for different sensor locations. Therefore, treadmill and level ground walking experiments were conducted with ten healthy subjects at increasing walking speeds and an age-simulating suit. With the proposed algorithm, we achieved a RMSE of 0.07 s for the stride interval estimation during treadmill walking experiments. The results give promising indications that detection of variation of stride time variability is possible using the proposed unobtrusive sensor setup.

Fatty acid-induced induction of Toll-like receptor-4/nuclear factor-kappaB pathway in adipocytes links nutritional signalling with innate immunity.

To study the effects of fatty acids and the involvement of the Toll-like receptor-4/nuclear factor-kappaB (TLR-4/NF-kappaB) pathway with respect to the secretion of adipokines from adipocytes 3T3-L1 adipocytes were stimulated with increasing doses of fatty acids. The secretion of adiponectin, resistin and monocyte chemoattractant protein-1 (MCP-1) was measured by enzyme-linked immunosorbent assay. The NF-kappaB p65 nuclear translocation and TLR-4 expression were investigated by Western blot. The effects mediated by NF-kappaB were tested using a specific NF-kappaB-inhibitor and TLR-4-induced effects were analysed with a neutralizing TLR-4 antibody. Binding of (14)C-labelled fatty acids to TLR-4/MD-2 was investigated using a FLAG-tagged extracellular part of TLR-4 fused to full-length MD-2 via a linker (lipopolysaccharide-Trap). The messenger RNA (mRNA) expression of adipokines in abdominal adipose tissue of rats fed a standard chow or a high-fat diet was investigated by reverse transcription-polymerase chain reaction. The TLR-4 is induced during adipocyte differentiation and its expression is enhanced following fatty acid stimulation. The stimulatory effects of stearic and palmitic acids on MCP-1 secretion and of palmitoleic acid on resistin secretion are mediated via NF-kappaB. The stimulatory effects of stearic, palmitic and palmitoleic acids on resistin secretion and the stimulatory effect of stearic acid on MCP-1 secretion are mediated via TLR-4. Fatty acid-mediated effects are caused by an endogenous ligand because fatty acids were shown not to bind directly to TLR-4/MD-2. Adipose tissue mRNA expression and serum levels of adipokines did not differ in rats fed a high-fat diet. These data provide a new molecular mechanism by which fatty acids can link nutrition with innate immunity.

Using a Motion Capture System as Reference for Motion Tracking in Photoplethysmography Imaging.

Photoplethysmography Imaging (PPGI) is a camera-based and non-contact technology for measurement of physiological signals. It has been shown that important physiological parameters such as heart rate, heart rate variability and respiratory rate can be derived from PPGI. However, as is the case with most non-contact measurement techniques, motion artefacts present a major challenge. Various algorithms for application to both the 2D PPGI video frames as well as the resulting 1D PPGI waveforms have been developed in order to enhance robustness against motion. In this paper, we focus on the aspect of feature point tracking in the 2D PPGI video sequences. We present an experimental setup, where we used a motion capture system in order to obtain a reference for motion during the recording of PPGI video sequences. In a laboratory experiment, PPGI video sequences were recorded from ten healthy volunteers, who were asked to perform various movements during the recording. The KLT tracking algorithm was applied to the recorded sequences and results compared with the reference values from the motion capture system. The results indicate, that tracking of measurement regions in PPGI video sequences is only one element towards motion robust PPGI. In most scenarios, tracking is not sufficiently precise, requiring further processing of the PPGI waveforms in order to reduce motion artefacts in PPGI signals. These indications were confirmed by further analysis when we looked into the effects of tracking on PPGI heart rate extraction.

Walking with rollator: a systematic review of gait parameters in older persons.

BACKGROUND: The aging population increasingly needs assistive technologies, such as rollators, to function and live less dependently. Rollators are designed to decrease the risk of falls by improving the gait mechanics of their users. However, data on the biomechanics of rollator assisted gait of older adults are limited, or mostly derived from experiments with younger adults. METHODS AND RESULTS: This review summarises the data from 18 independent studies on the kinematic and kinetic gait parameters of assisted gait of older persons. All of these studies evaluated spatio-temporal parameters, but not joint angles or moments. CONCLUSION: Due to the limited research on rollator supported gait in older adults, the number of parameters that could be analysed in this systematic review was restricted. Further research in the analysis of spatio-temporal parameters and a higher standardisation in clinical research will be necessary.