Bioimpedance Measurements Research Articles

Use of bioimpedance in prevention of sarcopenia in the elderly.

Physiological ageing is associated with major and progressive changes in body composition, particularly in the decline of fat-free mass, which puts older individuals at risk of geriatric syndromes such as sarcopenia and sarcopenic obesity. Bioimpedance analysis noninvasively allows the determination of body composition, thus being able to rapidly assess primary risk factors leading to sarcopenia prediction. We conducted a study of 180 probands, 120 females (66.7%) with a mean age of 76.23 (SD = 9.29) years and 60 males (33.3%) with a mean age of 74.01 (SD = 8.99) years in cooperation with facilities for the elderly and with the inpatient department of the clinics of J.A. Reimann Hospital in Prešov. Body height, body weight, hip circumference, and waist circumference were determined by the anthropometric method, from which the values of the body mass index and waist-to-hip ratio were calculated. Active body mass, total body water, extracellular body water, intracellular body water, cell mass, body mass fat, body fat index, fat-free mass index, impedance at frequencies of 50 kHz, resistance, reactance, and phase angle were determined using the Quadscan 4000 Touch bioimpedance instrument. Appendicular skeletal muscle mass (ASMM) and muscle mass (ASMM/Ht2) were calculated. The data obtained from anthropometric and bioimpedance measurements were processed in MS Excel 2000 and STATISTICA ver. 12. The difference of means in the studied groups was tested by the t-test. Presarcopenia was diagnosed in 12 (6.66%) probands out of 180 probands, of which were 3 (5%) men and 9 women (7.5%). Phase angle, ASMM and ASMM/Ht2 values were significantly lower (p < 0.001) in men and women with presarcopenia. By introducing bioimpedance measurements into practice, it is possible to obtain results in a non-invasive way revealing possible presarcopenia in the elderly.

Effectiveness of Complex Medical Rehabilitation of Patients with Postthrombophlebitic Syndrome of Lower Extremities and Obesity: a Randomized Clinical Study

INTRODUCTION. The relevance of the development of comprehensive rehabilitation programmes for patients with postthrombophlebitic syndrome (PTPS) is due to the high frequency of disability and a significant reduction in their quality of life. Since obesity and excessive body weight are proven risk factors for the development and progression of chronic vein diseases, weight reduction is one of the important tasks of rehabilitation measures in patients with PTPS and concomitant obesity.&#x0D; AIM. Comparative study of the influence of complex methods of medical rehabilitation, including various methods of laser blood irradiation (supravascular and intravenous), pulse magnetotherapy and dry carbon baths, on the dynamics of indicators of composite body composition according to bioimpedance measurements in patients with postthrombophlebitic syndrome of the lower extremities and obesity.&#x0D; MATERIALS AND METHODS. A randomized prospective study was conducted on the basis of the Department of Medical Rehabilitation of Patients with Somatic Diseases of National Medical Research Center of Rehabilitation and Balneology of the Ministry of Health of Russia. The study included 40 patients with PTS of the lower extremities and accompanying obesity, the average age of which was 58.3 [51.5; 68.0] year), randomized to two groups. The patients of the 1st group received Intravenous laser blood irradiation (ILIB) (“Lazmik”, Russia), impulse magnetotherapy and dry carbon baths, as well as therapeutic gymnastics in the hall. The patients of the 2nd group received a complex that included supravascular laser irradiation of blood (“Azor-2K”, Russia), pulse magnetic therapy, and dry carbon baths, as well as therapeutic gymnastics in the gym. Anthropometric measurements (body mass, malleolar volume) were used for the evaluation of anti-edema and lipolytic effects after a comprehensive course of medical rehabilitation, as well as bioimpedance measurement of body composition (“MEDASS”, Russia).&#x0D; RESULTS. In patients with PTS of the lower extremities and obesity, after carrying out a course of medical rehabilitation using preformed physical factors, including various methods of laser irradiation of the blood (supravascular and intravenous), a significant decrease in body weight indicators was observed (p 0.001), a decrease in BMI (p 0.001), total and extracellular fluid (p 0.001) without significant differences between groups. A significant decrease in the index of fat mass (kg) (p = 0.007) was found in patients of the main group.&#x0D; DISCUSSION. Maintaining a healthy body weight as well as combating obesity are first-line secondary prevention measures recommended for all patients with PTS of the lower extremities. For the control of the dynamics of the composite composition of the body, an effective and sensitive method is the method of bioimpedance measurement, which allows to estimate the reduction of extracellular fluid (anti-flow effect) and fat mass of the body (lipolytic effect).&#x0D; CONCLUSION. The method of bioimpedance measurement, used for the evaluation of the composite composition of the body, showed high sensitivity and allowed to establish the greater effectiveness of the developed complex, which includes ILIB with a wavelength of low-intensity laser radiation (NILI) of 635 nm in reducing fat mass.

The condition of the fluid compartments by the method of bioimpedancemetry in victims with a blast injury

BACKGROUND. According to the modern standards, in case of an acute blood loss, the pathogenetic provision of fluid therapy is based on the ROSE/D concept. According to this concept, after the initial emergency restoration of circulating blood volume, the fluid compartments should be optimized with further stabilization of the condition.&#x0D; OBJECTIVE. To study the fluid compartments in mine-explosive injuries victims.&#x0D; MATERIALS AND METHODS. 28 servicemen aged 20 to 51 years (average age 34.6±10.3 years) who were in the intensive care unit (ICU) with mine-explosive injuries of various localization (chest, abdomen, limbs) were examined. The victims were given fluid therapy in a restrictive mode. The condition of fluid compartments was determined by the method of bioimpedance measurement and calculation methods.&#x0D; RESULTS. On the first day of ICU stay, the total amount of water in the body exceeded the norm by 3 %. At the same time, the volume of intracellular water was significantly lower than normal by 22 %. On the second day, the total amount of water in the body normalized, but the indicator of intracellular water increased by 9.5 % of the reference.&#x0D; CONCLUSIONS. It is shown that despite the restoration of the circulating blood volume, there is an intracellular fluid deficit, which, even in the conditions of the restrictive fluid therapy, is replaced by a slight compensatory intracellular hyperhydration the next day when the intravascular volume of fluid is normalized.

HEALTH CONDITIONS, CONTROL BELIEFS, AND ATTITUDINAL BELIEFS OF USING TECHNOLOGY IN LOW-INCOME OLDER ADULTS

Abstract Integrating assistive technologies into fall prevention interventions could improve health outcomes, but older adults in low-income settings face greater challenges with technology use due to factors such as cost, access, and location. We examined the acceptance of technology in low-income older adults and the factors associated with their acceptance. In this cross-sectional study, 126 adults aged 60 years and older agreed to participate in the study. Three technologies, including a BTrack balance system (BBS), bioimpedance measurement device (InBody), and activity monitoring device (Actigraphs) were used to assess fall risk. The Senior Technology Acceptance (STA) was used to assess the acceptance of technology. STA consists of four domains with 14 items (1-10 rating scale). The Pearson correlation test was used to determine the correlation between STA scores, fall risk, and demographic factors. We found a significant correlation between STA and the CDC’s STEADI fall risk score (r = 0.3, p = 0.00075); between STA and education (r = 0.26, p = 0.0042); and between STA and age (r = -0.32, p = 0.00031). Participants had the highest mean STA scores to the lowest mean scores as follows: health conditions (41.9 ± 5.8), control beliefs (30.1 ± 8.1), attitudinal beliefs (20.9 ± 8.2), and gerontological anxiety (8.3 ± 5.7). The use of technology is acceptable to low-income older adults but fall risk, education, and age were associated with acceptance. They may benefit from technologically based fall prevention intervention since they have the potential to use technology with low fear expressed toward it.

Inflammation in Hypervolemic Hemodialysis Patients: The Roles of RelB and Caspase-4.

Hypervolemia is associated with inflammation in hemodialysis (HD) patients. How hypervolemia triggers inflammation is not entirely known. We initiated a cross-sectional study enrolling 40 hemodialysis patients who were categorized into normovolemic (N; 23) and hypervolemic (H; 17) groups by bioimpedance measurement. A caspase activity assay in combination with a specific caspase-4 inhibitor was used to detect caspase-4 activity in isolated peripheral blood mononuclear cells (PBMCs). Transcription factors RelA (pS529) and RelB (pS552) were analyzed by phospho-flow cytometry. Serum endotoxins were detected by an amebocyte lysate-based assay, and IL-6 (interleukin-6) and TNF-α (Tumor necrosis factor-α) gene expression were detected using the ELISA technique. Hypervolemic patients were older, more frequently had diabetes and showed increased CRP and IL-6 levels. Caspase-4 activity, which is linked to intracellular endotoxin detection, was significantly elevated in H patients. While the frequency of RelA-expressing immune cells and the expression density in these cells did not differ, the monocytic frequency of cells positively stained for RelB (pS552) was significantly decreased in H patients. Increased caspase-4 activity in H patients may indicate a cause of inflammation in H patients. The post-translational modification of RelB (pS552) is linked to downregulation of NF-kB activity and may indicate the resolution of inflammation, which is more distinct in N patients compared to H patients. Therefore, both higher inflammatory loads and lower inflammatory resolution capacities are characteristics of H patients.

Urinary Bladder Volume Reconstruction Based on Bioimpedance Measurements: Ex Vivo and In Vivo Validation Through Implanted Patch and Needle Electrodes

Urinary Bladder Volume Reconstruction Based on Bioimpedance Measurements: Ex Vivo and In Vivo Validation Through Implanted Patch and Needle Electrodes

Applied machine learning for stroke differentiation by electrical impedance tomography with realistic numerical models

Electrical impedance tomography (EIT) may have potential to overcome existing limitations in stroke differentiation, enabling low-cost, rapid, and mobile data collection. Combining bioimpedance measurement technologies such as EIT with machine learning classifiers to support decision-making can avoid commonly faced reconstruction challenges due to the nonlinear and ill-posed nature of EIT imaging. Therefore, in this work, we advance this field through a study integrating realistic head models with clinically relevant test scenarios, and a robust architecture consisting of nested cross-validation and principal component analysis. Specifically, realistic head models are designed which incorporate the highly conductive layers of cerebrospinal fluid in the subarachnoid space and ventricles. In total, 135 unique models are created to represent a large patient population, with normal, haemorrhagic, and ischemic brains. Simulated EIT voltage data generated from these models are used to assess the classification performance of support vector machines. Parameters explored include driving frequency, signal-to-noise ratio, kernel function, and composition of binary classes. Classifier accuracy at 60 dB signal-to-noise ratio, reported as mean and standard deviation, are (79.92% ± 10.82%) for lesion differentiation, (74.78% ± 3.79%) for lesion detection, (77.49% ± 15.90%) for bleed detection, and (60.31% ± 3.98%) for ischemia detection (after ruling out bleed). The results for each method were obtained with statistics from 3 independent runs with 17,280 observations, polynomial kernel functions, and feature reduction of 76% by PCA (from 208 to 50 features). While results of this study show promise for stroke differentiation using EIT data, our findings indicate that the achievable accuracy is highly dependent on the classification scenario and application-specific classifiers may be necessary to achieve acceptable accuracy.

Phase Angle as a Risk Factor for Mortality in Patients Undergoing Peritoneal Dialysis

Phase angle (PhA) is measured using bioimpedance analysis and calculated using body reactance and resistance in the waveform at 50 kHz. Further studies are necessary to clarify the predictive efficacy of PhA in the mortality of peritoneal dialysis (PD) patients. The objective of this study was to assess the utility of PhA for predicting patient mortality and technique failure and compare the predictability of PhA with other risk factors. Our study had a retrospective cohort design. Our center routinely evaluates bioimpedance measurements for all prevalent PD patients (n = 199). The PhA was measured using multifrequency bioimpedance analysis. Our study evaluated patient and technique survival. There were 66, 68, and 65 patients in the low, middle, and high tertiles of PhA, respectively. The PhA values of the low, middle, and high tertiles were 3.6° (3.4–3.9), 4.4° (4.2–4.7), and 5.5° (5.2–6.0), respectively. The 5-year patient survival rates for the high, middle, and low tertiles were 100%, 81.7%, 69.9%, respectively (p &lt; 0.001). The 5 year technique survival rates for the high, middle, and low tertiles were 91.9%, 74.8%, 63.7%, respectively (p = 0.004). Patient and technique survival increased as the PhA tertiles increased. Both univariate and multivariate Cox regression analyses demonstrated a consistent pattern. The prediction of patient or technique survival was better in PhA than in the other classical indicators. The present study demonstrated that PhA may be an effective indicator for predicting patient or technique survival in PD patients. Furthermore, it suggests that routine measurement of PhA and pre-emptive intervention to recover PhA according to causes of low PhA may help improve patient or technique survival in PD patients.

Differences in the swallowing process of newborns and healthy preterm infants: first results with a non-invasive bioimpedance and electromyography measurement system

PurposePreterm infants (PI) have difficulty coordinating sucking, swallowing and breathing, and there is a risk of aspiration. The causes of this are not yet sufficiently understood. The aim of this study was to test a novel measurement device to measure breathing and pharyngeal processes involved in swallowing externally in everyday life to identify possible differences in neonates (NB) and PI.MethodsForty healthy NB were studied at 4–8 weeks of age (mean: 6.7 weeks) and 20 healthy PI (mean gestational age 30.5 weeks) at postmenstrual age (PMA) 34/35 weeks (mean PMA 35.1 weeks) during a single feeding. Surface electrodes were used to measure bioimpedance and electromyography reflecting swallow-related changes in the pharynx and muscle activation of the tongue and submental muscles. A respiratory belt was combined with recording of the depth of chest movements and the occurrence of pauses in breathing.ResultsVelocity and extent of pharyngeal closure did not differ significantly across the feeding period (velocity: p=0.09, closure: p=0.17), but during the first two suck–swallow bursts PI had greater velocity (p<0.001*) and extent of pharyngeal closure (p=0.004*) than NB. The duration of swallowing phases was significantly longer in PIs (p<0.001*), their muscle activation decreased faster (p<0.001*), and they had more pauses in breathing than NBs.ConclusionsThe novel measurement device allowed, for the first time in everyday life, the measurement of factors influencing swallowing and breath–swallow coordination in NBs and PIs. PIs showed differences from NBs most likely due to differences in muscle strength and condition.

Is increased subjective thirst associated with greater interdialytic weight gains, extracellular fluid and dietary sodium intake?

Some previous studies have reported an effect of increasing subjective thirst and interdialytic weight gains (IDWG), and that this may be influenced by nonadherence to dietary sodium restrictions, whereas others reported no such association. As such we wished to review the effect of self-reported thirst on IDWGs and dietary sodium intake. Dialysis patients were asked to complete visual analogues thirst, distress thermometer (DT) scores and complete a sodium food frequency questionnaire (SFFQ). IDWG and pre and post dialysis volumes were measured with multifrequency bioelectrical impedance. One hundred and eleven patients completed the questionnaires and had bioimpedance measurements: 63% male, mean age 63.8 ± 16.1 years, 33% diabetic with a median thirst score 3 (0-5) and SFFQ 52.0 ± 18, and IDWG 2.1 ± 1.3%. Thirst was associated with DT (r = 0.28, p = 0.004) and negatively with age (r = -0.31, p < 0.001), but not SFFQ, IDWG, extracellular water, or dialysate sodium, or dialysate to plasma gradient. Patients with higher thirst scores were younger (58.0 ± 15.2 vs. 69.4 ± 15.0 years, p < 0.001) with higher DT scores (5 [2-7] vs. 2 [0-5], p < 0.001). On multivariate logistic analysis, only age was associated with self-reported thirst (odds ratio 0.95, 95% confidence limits 0.92-0.98, p < 0.001). We found that subjective thirst was greater for younger patients and those who reported higher levels of distress, but no association with IDWGs, dietary sodium intake, or dialysate sodium. However, most of our patients followed the dietary advice, as evidenced by the low SFFQ scores and % IDWGs. Whether thirst increases distress or distress increases subjective thirst remains to be determined.

A battery-less implantable glucose sensor based on electrical impedance spectroscopy

The ability to perform accurate continuous glucose monitoring without blood sampling has revolutionised the management of diabetes. Newer methods that can allow measurements during longer periods are necessary to substantially improve patients’ quality of life. This paper presents an alternative method for glucose monitoring which is based on electrical impedance spectroscopy. A battery-less implantable bioimpedance spectroscope was designed, built, and used in an in vivo study on pigs. After a recovery period of 14 days post surgery, a total of 236 subcutaneous bioimpedance measurements obtained from intravenous glucose tolerance tests, with glucose concentration ranges between 77.4 and 523.8 mg/dL, were analyzed. The results show that glucose concentrations estimated by subcutaneous bioimpedance measurements correlate very well to the blood glucose reference values. The pigs were clinically healthy throughout the study, and the postmortem examinations revealed no signs of adverse effects related to the sensor. The implantation of the sensor requires minor surgery. The implant, being externally powered, could in principle last indefinitely. These encouraging results demonstrate the potential of the bioimpedance method to be used in future continuous glucose monitoring systems.

Bio-impedance measurements for meat quality determination of pork loins under repeated freeze-thaw treatments

Evaluation of key quality traits in the cold chain is an important factor in ensuring meat safety. To meet the demands of consumers, development of non-destructive detection methods is essential for quality assessment of meat products. Electrical impedance spectroscopy (EIS) has emerged as one promising non-destructive technique in the food industry. In this study, EIS was developed to investigate the effects of freeze-thawing on quality parameters of porcine meat. Bioimpedance from 20 Hz to 200 kHz was collected from frozen-thawed meat, and the experimental impedance data were fitted to a Cole impedance model. The model fitting resulted in corresponding determination coefficient values of the resistance R and the reactance X, for needle electrodes (R2R=0.9683; R2X =0.9063) and plate electrodes (R2R=0.9442; R2X =0.8347). The Cole-impedance model well represented the collected bioimpedance datasets with standard deviations of 0.9611 Ω for needle electrodes and 0.9272 Ω for plate electrodes. Furthermore, there were significant differences in the Cole-impedance model parameters, which were attributed to the formation of ice crystals that implied cell membrane degeneration during freeze-thawing. Our results highlight the potential of bio-impedance measurements, gaining better insight on quality defects assessing in freeze-thawed meat.

Protective effect of MitoTEMPO against cardiac dysfunction caused by ischemia–reperfusion: MCAO stroke model study

Purpose Neurological impairments are the leading cause of post-stroke mortality, while stroke-related cardiovascular diseases rank second in significance. This study investigates the potential protective effects of MitoTEMPO (2,2,6,6-tetramethyl-4-[[2-(triphenylphosphonio) acetyl] amino]-1-piperidinyloxy, monochloride, monohydrate), a mitochondria-specific antioxidant, against cardiac and neurological complications following stroke. The objective is to assess whether MitoTEMPO can be utilized as a protective agent for individuals with a high risk of stroke. Materials and methods Seventeen-week-old male Wistar Albino rats were randomly assigned to three groups: SHAM, ischemia–reperfusion and MitoTEMPO + ischemia–reperfusion (MitoTEMPO injection 0.7 mg/kg/day for 14 days). The SHAM group underwent a sham operation, while the ischemia–reperfusion group underwent 1-h middle cerebral artery occlusion followed by three days of reperfusion. Afterwards, noninvasive thoracic electrical bioimpedance and electrocardiography measurements were taken, and sample collection was performed for histological and biochemical examinations. Results Our thoracic electrical bioimpedance and electrocardiography findings demonstrated that MitoTEMPO exhibited a protective effect on most parameters affected by ischemia–reperfusion compared to the SHAM group. Furthermore, our biochemical and histological data revealed a significant protective effect of MitoTEMPO against oxidative damage. Conclusions The findings suggest that both ischemia–reperfusion-induced cardiovascular abnormalities and the protective effect of MitoTEMPO may involve G-protein coupled receptor-mediated signaling mechanisms. This study was conducted with limitations including a single gender, a uniform age group, a specific stroke model limited to middle cerebral artery, and pre-scheduled only one ischemia–reperfusion period. In future studies, addressing these limitations may enable the implementation of preventive measures for individuals at high risk of stroke.

Technical aspects of a new approach to intraoperative pelvic neuromonitoring during robotic rectal surgery

It has been found that rectal surgery still leads to high rates of postoperative urinary, fecal, or sexual dysfunction, which is why nerve-sparing surgery has gained increasing importance. To improve functional outcomes, techniques to preserve pelvic autonomic nerves by identifying anatomic landmarks and implementing intraoperative neuromonitoring methods have been investigated. The objective of this study was to transfer a new approach to intraoperative pelvic neuromonitoring based on bioimpedance measurement to a clinical setting. Thirty patients (16 male, 14 female) involved in a prospective clinical investigation (German Clinical Trials Register DRKS00017437, date of first registration 31/03/2020) underwent nerve-sparing rectal surgery using a new approach to intraoperative pelvic neuromonitoring based on direct nerve stimulation and impedance measurement on target organs. Clinical feasibility of the method was outlined in 93.3% of the cases. Smooth muscle contraction of the urinary bladder and/ or the rectum in response to direct stimulation of innervating functional nerves correlated with a change in tissue impedance compared with the pre-contraction state. The mean amplitude (Amax) of positive signal responses was Amax = 3.8%, negative signal responses from a control tissue portion with no stimulation-induced impedance change had an amplitude variation of 0.4% on average. The amplitudes of positive and negative signal responses differed significantly (statistical analysis using two-sided t-test), allowing the nerves to be identified and preserved. The results indicate a reliable identification of pelvic autonomic nerves during rectal surgery.

Bioimpedance spectroscopy characterization of Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome (ME/CFS) peripheral blood mononuclear cells

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disabling and chronic disease, importantly related to the current COVID-19 pandemic. Currently, there are no specific laboratory tests to directly diagnose ME/CFS. In this work, the use of impedance spectroscopy is studied as a potential technique for the diagnosis of ME/CFS. A specific device for the electrical characterization of peripheral blood mononuclear cells was designed and implemented. Impedance spectroscopy measurements in the range from 1 Hz to 500 MHz were carried out after the osmotic stress of the samples with sodium chloride solution at 1M concentration. The evolution in time after the osmotic stress at two specific frequencies (1.36 kHz and 154 kHz) was analyzed. The device showed its sensitivity to the presence of cells and the evolution of the osmotic processes. Higher values of impedance (around 15% for both the real and imaginary part) were measured at 1.36 kHz in ME/CFS patients compared to control samples. No significant difference was found between patient samples and control samples at 154 kHz. Results help to further understand the diagnosis of ME/CFS patients and the relation of their blood samples with bioimpedance measurements.

Comparison of whole body versus thoracic bioimpedance in relation to ultrafiltration volume and systolic blood pressure during hemodialysis.

In contrast to whole body bioimpedance, which estimates fluid status at a single point in time, thoracic bioimpedance applied by a wearable device could enable continuous measurements. However, clinical experience with thoracic bioimpedance in patients on dialysis is limited. To test the reproducibility of whole body and thoracic bioimpedance measurements and to compare their relationship with hemodynamic changes during hemodialysis, these parameters were measured pre- and end-dialysis in 54 patients during two sessions. The resistance from both bioimpedance techniques was moderately reproducible between two dialysis sessions (intraclass correlations of pre- to end-dialysis whole body and thoracic resistance between session 1 and 2 were 0.711 [0.58-0.8] and 0.723 [0.6-0.81], respectively). There was a very high to high correlation between changes in ultrafiltration volume and changes in whole body thoracic resistance. Changes in systolic blood pressure negatively correlated to both bioimpedance techniques. Although the relationship between changes in ultrafiltration volume and changes in resistance was stronger for whole body bioimpedance, the relationship with changes in blood pressure was at least comparable for thoracic measurements. These results suggest that thoracic bioimpedance, measured by a wearable device, may serve as an interesting alternative to whole body measurements for continuous hemodynamic monitoring during hemodialysis.NEW & NOTEWORTHY We examined the role of whole body and thoracic bioimpedance in hemodynamic changes during hemodialysis. Whole body and thoracic bioimpedance signals were strongly related to ultrafiltration volume and moderately, negatively, to changes in blood pressure. This work supports the further development of a wearable device measuring thoracic bioimpedance longitudinally in patients on hemodialysis. As such, it may serve as an innovative tool for continuous hemodynamic monitoring during hemodialysis in hospital or in a home-based setting.

Dietary sodium restriction reduces blood pressure in patients with treatment resistant hypertension

PurposePatients with treatment resistant hypertension (TRH) are at particular risk of cardiovascular disease. Life style modification, including sodium restriction, is an important part of the treatment of these patients. We aimed to analyse if self-performed dietary sodium restriction could be implemented in patients with TRH and to evaluate the effect of this intervention on blood pressure (BP). Moreover, we aimed to examine if mechanisms involving nitric oxide, body water content and BNP, renal function and handling of sodium were involved in the effect on nocturnal and 24-h BP. Also, measurement of erythrocyte sodium sensitivity was included as a possible predictor for the effect of sodium restriction on BP levels.Patients and methodsTRH patients were included for this interventional four week study: two weeks on usual diet and two weeks on self-performed sodium restricted diet with supplementary handed out sodium-free bread. At the end of each period, 24-h BP and 24-h urine collections (sodium, potassium, ENaC) were performed, blood samples (BNP, NOx, salt blood test) were drawn, and bio impedance measurements were made.ResultsFifteen patients, 11 males, with a mean age of 59 years were included. After sodium restriction, urinary sodium excretion decreased from 186 (70) to 91 [51] mmol/24-h, and all but one reduced sodium excretion. Nocturnal and 24-h systolic BP were significantly reduced (− 8 and − 10 mmHg, respectively, p < 0.05). NOx increased, BNP and extracellular water content decreased, all significantly. Change in NOx correlated to the change in 24-h systolic BP. BP response after sodium restriction was not related to sodium sensitivity examined by salt blood test.ConclusionSelf-performed dietary sodium restriction was feasible in a population of patients with TRH, and BP was significantly reduced. Increased NOx synthesis may be involved in the BP lowering effect of sodium restriction.Trial registrationThe study was registered in Clinical trials with ID: NCT06022133.

Non-invasive monitoring of cardiac contractility: Trans-radial electrical bioimpedance velocimetry (TREV).

We describe methods and software resources for a bioimpedance measurement technique, 'trans-radial electrical bioimpedance velocimetry' (TREV) that allows for the non-invasive monitoring of relative cardiac contractility and stroke volume. After reviewing the relationship between the measurement and cardiac contractility, we describe the general recording methodology, which requires impedance measurements of the forearm. We provide open-source Jupyter-based software (operable on most computers) for deriving cardiac contractility from the impedance measurements. The software includes tools for removing variance associated with heart rate and respiration. We demonstrate the ability of this bioimpedance measurement for tracking beat-to-beat changes of contractility in a maximal grip force production task. Critically, the results demonstrate both a reactive increase in contractility with force production, and suggest there is a learned increase in contractility prior to grip onset, consistent with anticipatory allostatic autonomic regulation mediated by sympathetic inotropy. The method and software should be of broad utility for investigations of event-related cardiac dynamics in psychophysical studies.

Multifrequency bioimpedance device based on the Analog Discovery 2: performance and characterization

Abstract Bioimpedance spectroscopy can be used to investigate the composition and monitor the human body, organs, tissues, or cell cultures by measuring the voltage developed by the injection of small alternating currents at different frequencies. These currents are injected sequentially through a frequency sweep and a with a Howland current source or one of its modifications. However, the frequency sweep is not time efficient and introduces problems with data coherence in the case of bioinstability. On the other hand, the Howland current source requires high precision matching between its components. In this contribution we developed a custom-made device for bioimpedance measurements based on a multisine current waveform and on a negative-feedback topology for the current source. Measurements on passive elements showed that the device had less than 1Ω and 0.05∘ uncertainty in the frequency range between 500 Hz and 200 kHz for impedance between 1 kΩ and 10 kΩ. The measurements were affected by an inductive artifact connected with the limited common-mode rejection at high frequencies. Nevertheless, we could characterize the artifacts through a fitting procedure to recover the expected value of the targeted impedance.

A non-invasive, concealed electrocardiogram and bioimpedance measurement system for captive primates.

Captive housed non-human primates, specifically great apes such as chimpanzees (Pan troglodytes) are frequently reported to have died from or are diagnosed with potentially fatal heart conditions that require the monitoring of physiological signals such as electrocardiogram (ECG) or respiratory rate. ECG screening must be conducted after applying full anaesthesia, causing potential physical and emotional stress as well as risk for the animal. Here, we present an electronic system that simultaneously measures the ECG and the electrical bioimpedance for the early detection of abnormal cardiovascular activity. Modified gloves whose fingers are equipped with electrodes enable the caregiver to obtain three cardiovascular signals (ECG, pulse rate and respiratory rate) by placing the fingertips on specific parts of the non-human primate without needing any prior physical preparations. Validation (ECG and bioimpedance) was performed both on humans and on captive housed chimpanzees, where all the signals of interest were correctly acquired.