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Electrophysiology
Published in A. Bakiya, K. Kamalanand, R. L. J. De Britto, Mechano-Electric Correlations in the Human Physiological System, 2021
A. Bakiya, K. Kamalanand, R. L. J. De Britto
In an electrophysiological signal acquisition, electrode performance is extremely dependent on the impedance of the electrode–skin interface. The impact of the high electrode–skin impedance in the measurement of biological signals leads to poor signal quality, low signal-to-noise ratio and low signal amplitude (Albulbul, 2016). The proper selection of electrodes that have low electrode–skin impedance is necessary for biological measurements. Figure 3.8 shows the equivalent circuit model for the electrode–skin interface.
Indirect noninvasive venous testing
Published in Joseph A. Zygmunt, Venous Ultrasound, 2020
Impedance plethysmography (IPG) has its basis in electronics and impedance of a current across a segment. By measuring the voltage of a microcurrent across a segment of the limb and comparing this to known standards, assumptions can be made about the electrical current over the segment. Although blood, bone, and all subcutaneous tissue have impedance, with an assumption that only blood flow changes over time of the test duration, then the measurement of this voltage is proportional to VV in the limb. Although revolutionary when it was first developed, these devices can be a technically challenging to use. With the advent of duplex ultrasound, this technique has fallen out of favor.
Uterine Contraction Monitoring
Published in Sujoy K. Guba, Bioengineering in Reproductive Medicine, 2020
Concept of bioelectrical impedance has already been introduced in Chapter 2 under the section “Electrical Impedance of the Vaginal Wall”. Similar principles apply to uterine contraction monitoring. Kornmesser and Nyboer7 had reported observing changes in the electrical impedance during labor. Electrical impedance is a bulk tissue measurement approach in which the abdominal wall, uterus, fetus as well as other pelvic and abdominal organs figure. Theoretical basis for a possible correlation between uterine activity and electrical impedance change is that during labor the variation in the uterus is the most dominant change that occurs. The other organs and structures are forced to assume altered shapes mainly on account of the uterine activity. Thus any contribution to the change in impedance due to these other structures also in a way reflect uterine activity. In an uterine contraction there is a fundai dominance and the uterine wall becomes thicker in specific regions. As a consequence the electrical impedance will change. Finally the uterine wall is closer to the skin surface than other organs and will have a greater effect on the impedance than other deeper structures. Whether these factors are indeed operative has not yet been demonstrated by well controlled experiments, but that there are changes in the abdominal electrical impedance during labor is accepted.
Effect of bioelectrical impedance technology on the prognosis of dialysis patients: a meta-analysis of randomized controlled trials
Published in Renal Failure, 2023
Kaibi Yang, Shujun Pan, Nan Yang, Juan Wu, Yueming Liu, Qiang He
Bioelectrical impedance monitoring may allow better management of the dry weight in dialysis patients than other techniques provide [10]. Bioelectrical impedance technology is currently divided into two types: bioelectrical impedance spectroscopy (BIS) and bioelectrical impedance analysis (BIA). Both types analyze the body’s resistance and reactance by measuring the current applied to distant electrodes on the body’s surface to estimate the composition of the body, including systemic water, extracellular water (ECW), and intracellular water (ICW) [11]. Bioelectrical impedance technology has proven to be a practical body fluid volume measurement tool. Moreover, a large retrospective trial revealed that chronic fluid overload assessed by bioelectrical impedance technology is an independent risk factor for patient mortality [12]. On the other hand, previously conducted trials have shown inconsistent results on whether bioelectrical impedance technology can reduce mortality in dialysis patients.
Neighbourhood deprivation in childhood and adulthood and risk of arterial stiffness: the Cardiovascular Risk in Young Finns study
Published in Blood Pressure, 2023
Erika Kähönen, Satu Korpimäki, Markus Juonala, Mika Kähönen, Terho Lehtimäki, Nina Hutri-Kähönen, Olli T. Raitakari, Mika Kivimäki, Jussi Vahtera
Measurements of arterial PWV were performed in 2007 with a whole-body impedance cardiography device (CircMonR, JR Medical Ltd, Tallinn, Estonia). The method includes whole-body impedance cardiography, distal impedance plethysmography, and an ECG channel. Standard electrodes were placed on the body surface: for the whole-body impedance measurement a pair of current electrodes on the wrist and ankles, and a pair of voltage electrodes 5 cm proximal to the aforementioned current electrodes, and for the distal impedance plethysmography measurement the active electrode on the lateral side of the knee joint and reference electrode about 20 cm distal to it on the calf. The method registers continuous changes in body electrical impedance during a cardiac cycle. The whole-body impedance decreases when the pulse pressure wave enters the aortic arch and popliteal artery impedance decreases when the pulse pressure wave later enters the lower limb. The aortic-popliteal PWV can be calculated by the CircMonR device software from the pulse transit time and the approximate distance between the aortic arch and the popliteal artery. The measurement method and its validation procedure have been introduced in detail earlier (Aatola et al. 2010; Kööbi et al. 2003). This method has been detected to have good repeatability and reproducibility values and measurements have excellent correlation (r = 0.82) with tonometric PWV method measurements (Tahvanainen et al. 2009; Wilenius et al. 2016).
Increased thoracic fluid content is associated with higher risk for pneumonia in patients undergoing maintenance hemodialysis
Published in Renal Failure, 2023
Lijuan Yan, Yumei Qiu, Jin Liu, Jining Wu, Junwei Yang, Weichun He
With the development of new hardware and computational algorithms, impedance cardiography (ICG) is becoming more accurate and may provide a noninvasive alternative to hemodynamic monitoring [5,6]. Among the parameters monitored by ICG, thoracic fluid content (TFC) is an indicator for the assessment of changes in chest fluid volume [7]. Although a TFC value cannot be used to distinguish the location of excess fluid, it helps to indicate potential fluid overload, allowing further examination to localize fluid, such as pulmonary edema or pleural effusion. In most individuals, changes in the TFC values reflect altered fluid volume in the pulmonary intravascular and interstitial spaces [8]. Continuous monitoring of TFC has been used clinically to guide the regulation of fluid clearance during continuous renal replacement therapy.