Bio-impedance System Research Articles

IMPACT OF ADVANCED HEMODYNAMIC MONITORING ON MYOCARDIAL REVASCULARIZATION SURGERY IN HIGH-RISK PATIENTS

Coronary artery bypass grafting is a critical procedure for patients with advanced coronary disease, especially those classified as high risk due to comorbidities such as heart failure, hypertension and diabetes. Advanced hemodynamic monitoring has proved essential in this context, allowing continuous and accurate surveillance of cardiac and vascular parameters, which can reduce intra- and post-operative complications. This abstract aims to assess the impact of advanced hemodynamic monitoring during coronary artery bypass graft surgery in high-risk patients. The aim is to explore the advantages of this type of monitoring, the technologies used and the benefits in terms of clinical outcomes and reduction of complications. This is a literature review with a qualitative approach, carried out in the PubMed, SciELO, LILACS, BVS and Google Scholar databases. In order to optimize the search, descriptors such as Hemodynamic Monitoring, Cardiac Surgery, High Risk Patients and Fluid Management were used. For time delimitation, the research considered publications between the years 2019 and 2022, a period that reflects the latest advances in hemodynamic monitoring technologies in high-risk cardiac surgeries. Advanced hemodynamic monitoring includes the use of devices such as the pulmonary artery catheter and non-invasive bioimpedance systems, which provide real-time data on cardiac output, blood pressure, oxygen saturation and systemic vascular resistance. In high-risk patients, these devices allow for precise adjustments in the administration of fluids and vasoactive drugs, promoting better hemodynamic stability. Studies indicate that this approach reduces the incidence of serious complications, such as cardiogenic shock and arrhythmias, optimizing post-operative recovery. Therefore, advanced hemodynamic monitoring is a crucial tool in CABG surgeries, especially for high-risk patients. Its implementation improves intraoperative management, reducing the risk of complications and promoting better clinical outcomes. Therefore, its use should be considered an integral part of strategies for complex cardiac surgeries.

Body composition in a pediatric population with type-1 diabetes – The importance of planned physical exercise

Objective and methodsThis study aimed to assess the body composition of pediatric patients with type-1 diabetes (T1D) in a Portuguese pediatric endocrinology/diabetic clinic, using the InBody 570 bioimpedance system. Preschool children (<6 years) and those recently diagnosed (<6 months) were excluded. ResultsThe study included 78 patients (53% female). Median age at assessment was 14 years, with 81% pubertal children. Eighty-seven percent were using continuous subcutaneous insulin infusion (CSII), 25% with an automated closed-loop model. Median HbA1c was 7.3%. Most had an adequate body mass index (BMI) standard deviation score (62%) and 48% engaged in regular physical exercise (PE) outside of school. Median percentage body fat (PBF) was 21.5% and was abnormal in 48%, with median visceral adiposity of 4. Despite adequate BMI, 11% had excessive PBF. PBF was significantly associated with visceral fat (r=0.79; P<0.001), female gender (P<0.001) and PE performed out of school (P=0.005). PE was associated with lower PBF (P=0.005), lower visceral fat (P=0.002), and higher muscle-to-fat ratio (P=0.006). ConclusionEngaging in physical exercise out of school correlated significantly with improved body composition, characterized by reduced PBF and diminished visceral adiposity. Considering the known benefits of physical exercise for metabolic and glycemic control, this study highlights the importance of promoting regular physical exercise in T1D patients.

Total body water percentage and 3rd space water are novel risk factors for training-related lower extremity muscle injuries in young males

PurposeTo identify the risk factors for training-related lower extremity muscle injuries in young males by a non-invasive method of body composition analysis. MethodsA total of 282 healthy young male volunteers aged 18 – 20 years participated in this cohort study. Injury location, degree, and injury rate were adjusted by a questionnaire based on the overuse injury assessment methods used in epidemiological studies of sports injuries. The occurrence of training injuries is monitored and diagnosed by physicians and treated accordingly. The body composition was measured using the BodyStat QuadScan 4000 multifrequency Bio-impedance system at 5, 50, 100 and 200 kHz to obtain 4 impedance values. The Shapiro-Wilk test was used to check whether the data conformed to a normal distribution. Data of normal distribution were shown as mean ± SD and analyzed by t-test, while those of non-normal distribution were shown as median (Q1, Q3) and analyzed by Wilcoxon rank sum test. The receiver operator characteristic curve and logistic regression analysis were performed to investigate risk factors for developing training-related lower extremity injuries and accuracy. ResultsAmong the 282 subjects, 78 (27.7%) developed training injuries. Lower extremity training injuries revealed the highest incidence, accounting for 23.4% (66 cases). These patients showed higher percentages of lean body mass (p = 0.001), total body water (TBW, p = 0.006), extracellular water (p = 0.020) and intracellular water (p = 0.010) as well as a larger ratio of basal metabolic rate/total weight (p = 0.006), compared with those without lower extremity muscle injuries. On the contrary, the percentage of body fat (p = 0.001) and body fat mass index (p = 0.002) were lower. Logistic regression analysis showed that TBW percentage > 65.35% (p = 0.050, odds ratio = 3.114) and 3rd space water > 0.95% (p = 0.045, odds ratio = 2.342) were independent risk factors for lower extremity muscle injuries. ConclusionTBW percentage and 3rd space water measured with bio-impedance method are potential risk factors for predicting the incidence of lower extremity muscle injuries in young males following training.

Wearable and Noninvasive Device for Integral Congestive Heart Failure Management in the IoMT Paradigm.

Noninvasive remote monitoring of hemodynamic variables is essential in optimizing treatment opportunities and predicting rehospitalization in patients with congestive heart failure. The objective of this study is to develop a wearable bioimpedance-based device, which can provide continuous measurement of cardiac output and stroke volume, as well as other physiological parameters for a greater prognosis and prevention of congestive heart failure. The bioimpedance system, which is based on a robust and cost-effective measuring principle, was implemented in a CMOS application specific integrated circuit, and operates as the analog front-end of the device, which has been provided with a radio-frequency section for wireless communication. The operating parameters of the proposed wearable device are remotely configured through a graphical user interface to measure the magnitude and the phase of complex impedances over a bandwidth of 1 kHz to 1 MHz. As a result of this study, a cardiac activity monitor was implemented, and its accuracy was evaluated in 33 patients with different heart diseases, ages, and genders. The proposed device was compared with a well-established technique such as Doppler echocardiography, and the results showed that the two instruments are clinically equivalent.

Fundamentals of Skin Bioimpedances.

The bioimpedances of tissues beyond the stratum corneum, which is the outermost layer of skin, contain crucial clinical information. Nevertheless, bioimpedance measurements of both the viable skin and the adipose tissue, though easy and innocuous, are not widely used, mainly because of the complex multi-layered skin structure and of the electrically insulating nature of the stratum corneum. Here, first, we establish a theoretical framework for analyzing the impedances of multi-layered tissues and apply it to skin. Afterwards, we determine strategies for the system-level design of electrodes and electronics which minimize 4-wire (or tetrapolar) measurement errors even in presence of a top insulating tissue, thus enabling non-invasive characterizations of tissues beyond the stratum corneum. As an example, we demonstrate non-invasive measurements of bioimpedances of living tissues which are beyond orders-of-magnitude (e.g., up to 350 times) higher stratum corneum impedances independently on extreme variations of the barrier (tape stripping) or of the skin-electrodes contact impedances (sweat). Our results can advance the development of bioimpedance systems enabling the characterization of viable skin and adipose tissues for several applications, including transdermal drug delivery and the assessment of skin cancer, obesity, dehydration, type 2 diabetes mellitus, cardiovascular risk and multipotent adult stem cells. This article is protected by copyright. All rights reserved.

Smart needle electrical bioimpedance to provide information on needle tip relationship to target nerve prior to local anesthetic deposition in peripheral nerve block (USgPNB) procedures.

Ultrasound guided peripheral nerve block (USgPNB) refers to anaesthetic techniques to deposit local anesthetic next to nerves, permitting painful surgery without necessitating general anesthesia. Needle tip position prior to local anesthetic deposition is a key determinant of block success and safety. Nerve puncture and intra-neural injection of local anesthetic can cause permanent nerve injury. Currently ultrasound guidance is not sufficiently sensitive to reliably detect needle to nerve proximity. Feedback with bioimpedance data from the smart needle tip might provide the anesthetist with information as to the relationship between the needle tip and the target nerve prior to local anesthetic deposition. Bioimpedance using a smart needle integrated with a two-electrode impedance sensor has been developed to determine needle to nerve proximity during USgPNB. Having obtained all necessary ethical and regulatory approvals, in vivo data on brachial plexus, vagus, femoral and sciatic nerves were obtained from seven pig models using the smart needle bioimpedance system. The excision and histological analysis of above peripheral nerves and observation of the architecture and structure of nerves by means of histology allow the calculation of the ratios of connective tissue to neural tissue to determine the influence of this variable on absolute impedance. The ratio results give extra clinical data and explain the hetrogeneity of impedance data in the pig models and the hypothesis that connective tissue with intra-neural fat has higher impedance than neural tissue.

A Portable Band-shaped Bioimpedance System to Monitor the Body Fat and Fasting Glucose Level.

With better quality of life, obesity is becoming a worldwide disease due to over-eating and sedentary lifestyle. Therefore, daily monitoring of the glucose and body fat percentage (%) is vital to keep track of one's health. Currently, separated devices are required to monitor each parameter at home and some are still invasive to measure the glucose level. In this study, a portable band-shaped bioimpedance system is proposed to measure both parameters. The system is battery run with two main modules: the current source and the voltage recording, with minimal design to fit into a band of 150 mm x 40 mm in dimension. The impedance is measured at the frequency of 1 kHz at 30 kHz sampling frequency and in 1000 signal cycles to flatten noises. The final average impedance is calculated and evaluated in correlation with the body fat and the fasting glucose. The system was tested on 21 volunteers and 4 locations were picked for the impedance measurement: the arm under the triceps, the side of the belly, the back on one side and the thigh under the bicep femoris. The results show promising results with the arm being the best location for predicting the body fat (correlation coefficient: 0.89, 95% CI: 0.73-0.95), while the thigh impedance best correlated with the fasting glucose (correlation coefficient: 0.92, 95% CI: 0.81-0.97). These preliminary results indicate the feasibility and capacity of the proposed system as a home-based, portable and convenient system in monitoring the body fat and glucose. The system's performance will be verified and replicated in a future larger study.

Bioimpedance and Dual-Energy X-ray Absorptiometry Are Not Equivalent Technologies: Comparing Fat Mass and Fat-Free Mass.

Bioimpedance (BIA) is the most frequently used technology for body composition assessment at a daily clinical level, mostly due to its low price and user-friendly operation. However, many doubts persist regarding its physiological meaning and applicability. The present study aimed to compare one BIA system and the Dual-Energy X-ray Absorptiometry (DXA) for the characterization of body composition in a previously selected cohort of healthy adult participants. A descriptive observational cross-sectional study included a final sample of 121 participants, 93 women and 28 men, with a mean age of 28.26 ± 9.72 years old and a mean body mass index (BMI) of 22.68 ± 3.13 kg/m2. Statistics involved paired t-tests and agreement analysis by the Bland-Altman method. BIA underestimated the percent body fat (%BF) by 5.56% and overestimated Fat-Free Mass (FFM) by 2.90 kg. A strong positive correlation between both technologies was found for FFM (r = 0.980) and the %BF (r = 0.932), but the disagreement was statistically significant (p < 0.001). Although DXA and BIA seem to correlate, these technologies are not congruent. Therefore, the risk of (mis)interpretation and bias is clear with BIA, potentially impacting the nutritional planning of clinical dietitians and the further results of its patients.

Arterial Pulse Localization with Varying Electrode Sizes and Spacings in Wrist-Worn Bioimpedance Sensing.

Bioimpedance has emerged as a promising modality to continuously monitor hemodynamic and respiratory physiological parameters through a non-invasive skin-contact approach. Bioimpedance sensors placed at the radial zone of the volar wrist provide sensitive operation to the blood flow of the underlying radial artery. The translation of bioimpedance systems into medical-grade settings for continuous hemodynamic monitoring, however, presents challenges when constraining the necessary sensing components to a minimal form factor while maintaining sufficient accuracy and precision of measurements. Thus, it is important to understand the effects of electrode configuration on bioimpedance signals when reducing them to a wearable form factor. Previous work regarding electrode configurations in bioimpedance does not address wearable constraints, nor do they focus on electrodes viable for wearable applications. In this study, we present empirical evidence of the effects of dry silver electrode sizes and spacings on the specificity and sensitivity of a wrist-worn bioimpedance sensor array. We found that wrist-worn bioimpedance systems for hemodynamic monitoring would benefit from reduced injection electrode spacings (up to a 392% increase in signal amplitude with a 50% decrease in spacing), increased sensing electrode spacings, and decreased electrode surface areas. Clinical Relevance - The work directly contributes towards the development of cuffless continuous blood pressure monitors with applications in clinical and ambulatory settings.

Blood Pressure Estimation using a Single Channel Bio-Impedance Ring Sensor.

The demand for non-obtrusive, accurate, and continuous blood pressure (BP) monitoring systems is becoming more prevalent with the realization of its significance in preventable cardiovascular disease (CVD) globally. Current cuff-based standards are bulky, uncomfortable, and are limited to discrete recording periods. Wearable sensor technologies such as those using optical photoplethysmography (PPG) have been used to develop blood pressure estimation models through a variety of methods. However, this technology falls short as optical based systems have bias favoring lighter skin tones and lower body fat compositions. Bioimpedance (Bio-Z) is a capable modality of sensing arterial blood flow without implicit inadvertent bias towards individuals. In this paper we propose a ring-based bioimpedance system to capture arterial blood flow from the digital artery of the finger. The ring design provides a more compact wearable device utilizing only a single Bio-Z channel, making it a familiar fit to individuals. Post-processing the acquired Bio-Z signals, we extracted 9 frequency domain features from windowed beat cycles to train subject specific regression models. Results indicate the average mean absolute errors for systolic/diastolic BP to be 4.38/3.63mmHg, consistent with AAMI standards.

P4: REDIEM: Renal Extremity Device to Measure Impedance, Edema, Movement

Purpose: Advanced and end-stage renal disease (ESRD), is a leading cause of morbidity and mortality. Beyond internal biochemical abnormalities, patients are externally symptomatic of water and electrolyte abnormalities with excess fluid retention, e.g. leg edema; and uncontrolled leg movement, as restless leg syndrome (RLS). Limited methods exist to quantitatively follow leg edema and RLS in patients out of hospital and at home. We report on development of an integrated device capable of monitoring: 1. leg edema, 2. water content/dry weight, and 3. leg movement. Methods: An impedance-edema sensor, with incorporated accelerometer was designed. All components were integrated into a comfortable wearable band, with iOS applicability for ready interpretation (Fig 1). For initial assessment, tissue edema, and leg movement, were measured using facsimiles. Sensor band was placed on hydrated pork belly (leg edema facsimile), current applied (< 10 uA), resistance and impedance determined, and edema and tissue water content calculated via algorithm. Measurements were compared to those made with standardized bioimpedance system. For leg motion, band was placed on limb facsimile oscillated at defined frequency. Results: Initial sensor was able to measure differences in impedance correlating with differing degree of test tissue hydration. Measurements obtained via algorithm correlated closely with standardized bioimpedance system determinations (Fig 2.1, 2.2). The edema algorithm, compared to actual test absorbance, differed on average by 3.4%. Motion sensor was able to detect jerking RLS-like motions with an average of 8.3% error. Slower motion detection was found to be less accurate and is being currently addressed via system design evolution. Conclusion: Combining impedance measuring technology with motion sensing allows for fabrication of a wearable system able to measure leg edema and motion. Use of this system in Renal patients will allow optimization of management as related to water excess/dry weight and RLS and on a serial outpatient basis.

System Performance and User Feedback Regarding Wearable Bioimpedance System for Multi-Site Knee Tissue Monitoring: Free-Living Pilot Study With Healthy Adults.

Knee-focused wearable devices have the potential to support personalized rehabilitation therapies by monitoring localized tissue alterations related to activities that reduce functional symptoms and pain. However, supporting these applications requires reported data to be reliable and accurate which can be challenging in the unsupervised free-living conditions that wearable devices are deployed. This pilot study has assessed a knee-focused wearable sensor system to quantify 1) system performance (operation, rates of data artifacts, environment impacts) to estimate realistic targets for reliable data with this system and 2) user experiences (comfort, fit, usability) to help inform future designs to increase usability and adoption of knee-focused wearables. Study data was collected from five healthy adult participants over 2 days, with 84.5 and 35.9% of artifact free data for longitudinal and transverse electrode configurations. Small to moderate positive correlations were also identified between changes in resistance, temperature, and humidity with respect to acceleration to highlight how this system can be used to explore relationships between knee tissues and environmental/activity context.

Intelligent Bio-Impedance System for Personalized Continuous Blood Pressure Measurement.

Continuous blood pressure (BP) measurement is crucial for long-term cardiovascular monitoring, especially for prompt hypertension detection. However, most of the continuous BP measurements rely on the pulse transit time (PTT) from multiple-channel physiological acquisition systems that impede wearable applications. Recently, wearable and smart health electronics have become significant for next-generation personalized healthcare progress. This study proposes an intelligent single-channel bio-impedance system for personalized BP monitoring. Compared to the PTT-based methods, the proposed sensing configuration greatly reduces the hardware complexity, which is beneficial for wearable applications. Most of all, the proposed system can extract the significant BP features hidden from the measured bio-impedance signals by an ultra-lightweight AI algorithm, implemented to further establish a tailored BP model for personalized healthcare. In the human trial, the proposed system demonstrates the BP accuracy in terms of the mean error (ME) and the mean absolute error (MAE) within 1.7 ± 3.4 mmHg and 2.7 ± 2.6 mmHg, respectively, which agrees with the criteria of the Association for the Advancement of Medical Instrumentation (AAMI). In conclusion, this work presents a proof-of-concept for an AI-based single-channel bio-impedance BP system. The new wearable smart system is expected to accelerate the artificial intelligence of things (AIoT) technology for personalized BP healthcare in the future.

Multi-Channel Bioimpedance System for Detecting Vascular Tone in Human Limbs: An Approach.

Vascular tone plays a vital role in regulating blood pressure and coronary circulation, and it determines the peripheral vascular resistance. Vascular tone is dually regulated by the perivascular nerves and the cells in the inside lining of blood vessels (endothelial cells). Only a few methods for measuring vascular tone are available. Because of this, determining vascular tone in different arteries of the human body and monitoring tone changes is a vital challenge. This work presents an approach for determining vascular tone in human extremities based on multi-channel bioimpedance measurements. Detailed steps for processing the bioimpedance signals and extracting the main parameters from them have been presented. A graphical interface has been designed and implemented to display the vascular tone type in all channels with the phase of breathing during each cardiac cycle. This study is a key step towards understanding the way vascular tone changes in the extremities and how the nervous system regulates these changes. Future studies based on records of healthy and diseased people will contribute to increasing the possibility of early diagnosis of cardiovascular diseases.

A Novel Hypertension Management Algorithm Guided by Hemodynamic Data

A Novel Hypertension Management Algorithm Guided by Hemodynamic Data

A woven electrode with convex structure for electrical impedance tomography

We developed a silver/silver chloride (Ag/AgCl) woven electrode, which was woven in a convex high-density structure. The convex structure can decrease the motion artifacts caused by the slippage between human skin and the electrode. The high density can reduce the noise caused by the change of contact resistance. The model of the electrode–skin interface was proposed, and its equivalent circuit model was built, which can present an intuitive understanding of electrode design principles. Furthermore, AgCl particles were electrochemically deposited on the Ag electrode in terms of 23 schemes to optimize the deposition uniformity. The effects of deposition time, electrolyte concentration, and current/voltage magnitude were investigated. According to the result, the best combination is a constant current method, with the current at 0.01 A, the deposition time set to 300 s, and the electrolyte concentration as 0.05 M. The resistances of the deposited electrodes are qualified for impedance monitoring due to their small resistance. A bioimpedance system was assembled followed by the electrical impedance tomography mechanism. The frequency response and bioimpedance–time relationship were measured and analyzed in our bioimpedance system. The result reveals that the frequency response from [Formula: see text] to[Formula: see text] Hz presents a stable state for the convex woven electrode. The woven electrode system has a wider stable frequency band than the wet electrode. The bioimpedance of wet electrodes is stable in the initial time, whereas that of woven electrodes decreases with time. However, the wet electrode bioimpedance increases with time after 3 h, and the woven electrode bioimpedance is stable after 3 h. Both the interface capacitance and resistance have very important roles in the bioimpedance system. The woven electrode is better in long-term monitoring than the wet electrode. In addition, convex electrode bioimpedance presents less noise than the plain electrode. Therefore, the convex electrode is the best choice for the bioimpedance monitoring system.

Accuracy and reliability of the InBody 270 multi-frequency body composition analyser in 10-12-year-old children.

The aim of this study was at examining the validity and reliability of a marketed bioimpedance (BIA) scale for body composition assessment, in children engaged in an educational football project (FIFA 11 for Health). One-hundred and twenty-seven children (70 boys and 57 girls; age 10.7±0.5 years, body mass 41.2±9.0 kg, Body mass index 18.5±3.3 kg·m-2 and stature 149±7 cm) were evaluated for total body mass, lean body mass, muscle mass, using BIA (InBody 270, Biospace, California, USA) and dual-energy X-ray absorptiometry (DEXA, Lunar Prodigy, GE Medical Systems, Madison, Wisconsin, USA), at baseline conditions. Data analyses were carried out separately for girls and boys. Nearly perfect associations (r = 0.97−0.99) and excellent absolute (TEM = 0.04−1.9%) and relative (ICC = 0.98−1.00) inter-device reliability were found between DEXA and BIA variables. Fat and lean body mass bias (p < .0001) were practically relevant both for the boys (2.56 and 11.22 kg, respectively) and the girls (2.33 and 10.49 kg, respectively). Muscle mass and body fat were underestimated and overestimated, respectively, for the boys and girls. InBody 270 is a valid BIA system for estimating body composition with an excellent inter-device relative and absolute reliability. However, the remarkable measurements bias of BIA fat and muscle mass values discourage its use for clinical prescription. The BIA body composition biases were sex dependent.

Classification Accuracy of Body Mass Index for Excessive Body Fatness in Kuwaiti Adolescent Girls and Young Adult Women.

PurposeAdolescent obesity, as defined by BMI, is amongst the highest in the world in Kuwait. This study aimed to determine the extent to which BMI might be underestimating obesity as defined by excessive fatness in Kuwaiti female adolescents and young adults.MethodsA total of 400 apparently healthy Kuwaiti female university students (mean age 18.0 years, SD 0.6) were recruited. Excessive fatness was defined as body fat percentage ≥30, measured using the Tanita model TBF-310 Bio-impedance system with the manufacturer’s equation. Obesity was defined as recommended by the WHO in adult participants – those aged ≥19.1 years – as BMI≥30 kg/m2. In the adolescent participants (age <19.1 years) obesity was defined as recommended by the WHO as a BMI-for-age Z score of ≥2.00. The accuracy of BMI-defined obesity to identify excessively fat individuals was determined by estimating the prevalence of obesity using high BMI and prevalence of excessive fatness, and by calculating sensitivity and specificity and predictive values.ResultsMedian BMI was 27.8 kg/m2 (range 15.1–51.2) and median body fat percentage was 32.0 (range 5.0–54.0). The prevalence of excessive fatness was 62% (247/400 individuals were excessively fat), while the prevalence of obesity according to BMI was 42% (169/400 individuals were obese according to their BMI). The sensitivity of BMI to identify the excessively fat individuals was moderate (66%) but specificity was high (96%). The positive predictive value of BMI was 96% and the negative predictive value was 64%.ConclusionBMI-based measures substantially underestimate the prevalence of excessive fatness in Kuwaiti adolescent females. Obesity is even more prevalent, and requires more urgent attention, than is apparent from BMI-based measures used in most research and national surveys. BMI may also be too crude for use as an exposure or outcome variable in many epidemiological studies of Arab adolescent girls and adult women.

Frequency Dependences of the Rhinological Parameters of Electrical Bioimpedance in the Area of the Paranasal and Nasal Sinuses

Introduction. Possibilities of three-frequency broadband electrical bioimpedanceometry of the nasal and paranasal regions were investigated.Research methodology and equipment. The studies were performed experimentally non-invasively using a three-frequency wideband bioimpedance system TOR-M-1, adapted to the conditions and requirements of rhinological studies. The TOR-M-1 system provides the measurement of the module Z and the phase angle φ of the impedance of the human body sections at three frequencies of 20 kHz, 100 kHz and 500 kHz with programmatic calculation of active R, reactive X components of the impedance at these frequencies. Non-invasive impedance parameters were measured using a tetrapolar technique using paired stainless steel active electrodes connected to the human body in the area between the cheek and the hand.Results and Discussion. It is established that the values ​​of the module, phase angle, active and reactive components of the impedance at these frequencies are individually individual for a particular person and change dynamically in the presence of rhinological diseases. The most characteristic features that characterize the normal and abnormal conditions of the nasal and paranasal tissues, are concentrated in the frequency dependences of the phase angle.Conclusions. Cole diagrams for groups of patients with certain phase-to-angle ratios at three frequencies show the possibility of determining different functional states of patients: the normal state, the presence of residual phenomena of rhinological diseases, while the subjective person feels normal and active disease. The results of impedance frequency parameters dynamics during respiratory disease are presented.

Non-invasive hemodynamic profiling of patients undergoing hemodialysis - a multicenter observational cohort study

BackgroundIntradialytic blood pressure (BP) measurement is currently the main parameter used for monitoring hemodynamics during hemodialysis (HD). Since BP is dependent on cardiac output and total peripheral resistance, knowledge of these parameters throughout the HD treatment would potentially be valuable.MethodsThe use of a novel non-invasive monitoring system for profiling hemodynamic response patterns during HD was explored: a whole-body bio-impedance system was used to assess cardiac index (CI), total peripheral resistance index (TPRI), cardiac power index (CPI) among other parameters in chronic HD patients from 4 medical centers. Measurements were made pre, during and post dialysis. Patients were grouped into 5 hemodynamic profiles based on their main hemodynamic response during dialysis i.e. high TPRI; high CPI; low CPI; low TPRI and those with normal hemodynamics. Comparisons were made between the groups for baseline characteristics and 1-year mortality.ResultsIn 144 patients with mean age of 67.3 ± 12.1 years pre-dialysis hemodynamic measurements were within normal limits in 35.4% but only 6.9% overall remained hemodynamically stable during dialysis. Intradialytic BP decreased in 65 (45.1%) in whom, low CPI (47 (72.3%)) and low TPRI (18 (27.7%) were recorded. At 1-year follow-up, mortality rates were highest in patients with low CPI (23.4%) and low TPRI (22.2%).ConclusionsNon-invasive assessment of patients’ response to HD provides relevant hemodynamic information that exceeds that provided by currently used BP measurements. Use of these online analyses could potentially improve the safety and performance standards of dialysis by guiding appropriate interventions, particularly in responding to hypertension and hypotension.