Stroke volume obtained by electrical interrogation of the brachial artery: transbrachial electrical bioimpedance velocimetry

Abstract

The goal of this study is to measure left ventricular stroke volume (SV) from the brachial artery (BA) using electrical bioimpedance. Doppler-derived SV was used for comparison. Twenty-nine healthy adults were recruited for study. Doppler echocardiographic-derived SV was obtained from the product of distal left ventricular outflow tract cross-sectional area and systolic velocity integral. SV from the BA was obtained by transbrachial electrical bioimpedance velocimetry (TBEV). Application of a current field across the left brachium was effected by injection of a constant magnitude, high frequency, low amperage, alternating current. Therein, a static voltage (U(0)) and pulsatile voltage change (ΔU(t)) were measured and converted to their corresponding impedances, Z(0) and ΔZ(t). TBEV-derived SV was obtained by multiplying a square root value of the normalized, acceleration-based, peak first time derivative of ΔZ(t) by a volume conductor and systolic flow time. Inter-method agreement was determined by the Bland-Altman method. To assess the contribution of blood resistivity variations to ΔZ(t), BA diameters were measured at end-diastole and peak systolic expansion. Results indicate that since the BA demonstrates parabolic, laminar flow, with minimal diameter changes, blood resistivity variations are likely responsible for the derived impedance changes. Bland-Altman analysis shows that SV is obtainable by TBEV from healthy humans at rest.

Validation of stroke volume and cardiac output by electrical interrogation of the brachial artery in normals: assessment of strengths, limitations, and sources of error

“…By history, physical examination, electrocardiography, echocardiography, and magnetic resonance imaging, the subjects showed no demonstrable evidence of heart disease. Since cMRI is considered the absolute gold standard for measurement of ventricular volumes [ 16 , 17 ], SV obtained from that technique was compared to SV determined by TBEV [ 15 ]. In order to obtain a wide spectrum of SV and CO, subjects were recruited with a broad range of heights, weights, and body mass indices (BMI).…”

“…IZ = U). The proximal assembly houses the upper voltage sensor and current driver, and the distal assembly houses the electronic circuit board into which the lower voltage sensor and current driver are integrated [ 15 ]. Figure 1 b is a photograph of a human volunteer wearing the TBEV montage.…”

“…This study in normal humans concerns the validation of a new noninvasive, velocimetric-based, pulsatile SV technique, known as transbrachial electrical bioimpedance velocimetry (TBEV) [ 15 ]. As compared to ICG implemented transthoracically, TBEV is, in theory and method, an ICG equivalent, but operationally signal acquisition is obtained from the upper arm.…”

Textrode-enabled transthoracic electrical bioimpedance measurements – towards wearable applications of impedance cardiography

“…This inefficiency in the correlation between curves and estimated variables suggest a lack of robustness in the equation models to estimate SV and a low sensitivity and specificity of the impedance signal acquisition in some medical conditions. In addition to this, a necessary consensus on whether the physiological origin of dZ/dt comes predominantly from volume changes as traditionally believed or from blood resistivity changes in the vessels as more recent evidence presented by Bernstein et al [16,21] indicates must still be arrived at.…”

Simultaneous Recording of ICG and ECG Using Z-RPI Device with Minimum Number of Electrodes

“…Electrical bioimpedance (EBI) is a sensing technology that has been used for several decades for various applications [3], utilizing different measurement techniques, e.g., segmental and/or total body [4], spectroscopy [5,6], tomography [7], and impedance plethysmography [8] with its most common application which is impedance cardiography (ICG). Using a single channel with single frequency continuously, the ICG was introduced as a noninvasive method and its waveform has been used for the assessment of certain hemodynamic parameters describing the mechanical function of the heart like the cardiac output (CO), stroke volume (SV), and systolic time intervals, e.g., left ventricular ejection time (LVET noted also ET), preejection period (PEP), and systolic time ratio (STR) [9][10][11].…”