Bioimpedance analysis as a tool for hemodynamic monitoring: overview, methods and challenges

Abstract

Recent advances in hemodynamic monitoring have seen the advent of non-invasive methods which offer ease of application and improve patient comfort. Bioimpedance Analysis or BIA is one of the currently employed non-invasive techniques for hemodynamic monitoring. Impedance Cardiography (ICG), one of the implementations of BIA, is widely used as a non-invasive procedure for estimating hemodynamic parameters such as stroke volume (SV) and cardiac output (CO). Even though BIA is not a new diagnostic technique, it has failed to gain consensus as a reliable measure of hemodynamic parameters. Several devices have emerged for estimating CO using ICG which are based on evolving methodologies and techniques to calculate SV. However, the calculations are generally dependent on the electrode configurations (whole body, segmental or localised) as well as the accuracy of different techniques in tracking blood flow changes. Blood volume changes, concentration of red blood cells, pulsatile velocity profile and ambient temperature contribute to the overall conductivity of blood and hence its impedance response during flow. There is a growing interest in investigating limbs for localised BIA to estimate hemodynamic parameters such as pulse wave velocity. As such, this paper summarises the current state of hemodynamic monitoring through BIA in terms of different configurations and devices in the market. The conductivity of blood flow has been emphasized with contributions from both volume and velocity changes during flow. Recommendations for using BIA in hemodynamic monitoring have been mentioned highlighting the suitable range of frequencies (1 kHz–1 MHz) as well as safety considerations for a BIA setup. Finally, current challenges in using BIA such as geometry assumption and inaccuracies have been discussed while mentioning potential advantages of a multi-frequency analysis to cover all the major contributors to blood’s impedance response during flow.

Electrical impedance plethysmography versus tonometry to measure the pulse wave velocity in peripheral arteries in young healthy volunteers: a pilot study

“…A possible explanation for this is that the bioimpedance is more sensitive to various changes in the blood vessel compared to the tonometer. The bioimpedance is affected by changes in blood volume, blood velocity and blood composition (haematocrit, the ratio of volume of red blood cells to the total volume of the blood), while the tonometer is only dependent on the pressure difference ( 23 , 24 ). The signal of the tonometer shows two peaks, the first peak is a result from the ejection of the left ventricle and the second peak from the wave reflections from the peripheral arteries ( 25 ).…”

The Efficacy and Safety of Phase I Cardiac Rehabilitation in Patients Hospitalized in Cardiac Intensive Care Unit With Acute Decompensated Heart Failure: A Study Protocol for a Randomized, Controlled, Clinical Trial

“…In control group, subjects without contraindications will receive air pressure therapy to prevent deep vein thrombosis. The impedance cardiography (ICG) is a reliable, repeatable and non-invasive method to monitor cardiodynamic data including stroke volume (SV), end diastolic filling rate (EDFR) and peripheral vascular resistance (SVR) ( 20 , 21 ). Passive Leg Raising (PLR) test, a reversible fluid-loading procedure to test fluid responsiveness, is used to ensure the safety of phase I cardiac rehabilitation ( 22 , 23 ).…”

Determination of the Geometric Parameters of Electrode Systems for Electrical Impedance Myography: A Preliminary Study

“…Figure 1 shows that the individual mechanisms contribution for the EI signal conditioning described above may differ depending on the ES sizes, which sometimes leads to obtaining different results of EI studies. So, for example, at large interelectrode distances, the EI signal conditioning is mainly associated with the muscle’s resistance change and blood filling, and with an ES size comparable to the limb characteristic dimensions, with a change in the skin-fat layer thickness [ 22 ].…”

“…Figure 1 shows that the individual mechanisms contribution for the EI signal conditioning described above may differ depending on the ES sizes, which sometimes leads to obtaining different results of EI studies. So, for example, at large interelectrode distances, the EI signal conditioning is mainly associated with the muscle's resistance change and blood filling, and with an ES size comparable to the limb characteristic dimensions, with a change in the skin-fat layer thickness [22]. In this work, we consider two main contributions that affect EI signal conditioning when the small size ES (Figure 1, left) is located in the muscle projection area or forearm In this work, we consider two main contributions that affect EI signal conditioning when the small size ES (Figure 1, left) is located in the muscle projection area or forearm muscle group, which are active during the motion: a change in the skin-fat layer thickness and muscle resistivity.…”