he electric capacitance of biological tissues serves as the basis for numerous medical technologies. For example, dielectric spectroscopy glucose reading (DSGR) is a noninvasive diagnostic technique that uses the electric capacitance of blood to estimate blood glucose levels.
A DSGR device records the electric current that results from applying a voltage source to the skin and underlying blood vessels. DSGR can be modeled by the circuit shown in Figure 1, in which V represents the applied potential, CB represents the capacitance of the blood, and RE, RD, and RB represent the electrical resistances of the epidermis, the dermis, and the blood, respectively.
Figure 1 DSGR circuit model including skin and superficial blood vessel
The capacitance of charged blood may be explained by red blood cell membranes acting as physical barriers that separate electrons introduced into the blood from positively charged ions in the red blood cell cytoplasm. The dielectric constant k of red blood cell membranes varies with glucose concentration (Figure 2) because glucose uptake by red blood cells alters the activity of membrane-bound proteins that regulate the flow of ions into and out of the cell.
Figure 2 Blood dielectric constant vs blood glucose concentration
DSGR readings vary with blood glucose concentration because the time needed to fully charge the blood is related to total blood capacitance. However, interpreting DSGR readings may be complicated by changes in biological variables other than blood capacitance. For example, the resistivity of blood varies in accordance with osmolarity such that changes in diet or hydration status influence the current measured by DSGR devices.
Assume that the average radial artery has a cross-sectional area A of 0.2 cm2 and a length L of 30 cm. What is the total resistance R of the radial artery? (Note: The resistivity of blood is 200 Ω-cm)
he electric capacitance of biological tissues serves as the basis for numerous medical technologies. For example,...
he electric capacitance of biological tissues
serves as the basis for numerous medical technologies. For example,
dielectric spectroscopy glucose reading (DSGR) is
a noninvasive diagnostic technique that uses the electric
capacitance of blood to estimate blood glucose levels.
A DSGR device records the electric current that results from
applying a voltage source to the skin and underlying blood vessels.
DSGR can be modeled by the circuit shown in Figure 1, in which V
represents the applied potential, CB represents the...
he electric capacitance of biological tissues
serves as the basis for numerous medical technologies. For example,
dielectric spectroscopy glucose reading (DSGR) is
a noninvasive diagnostic technique that uses the electric
capacitance of blood to estimate blood glucose levels.
A DSGR device records the electric current that results from
applying a voltage source to the skin and underlying blood vessels.
DSGR can be modeled by the circuit shown in Figure 1, in which V
represents the applied potential, CB represents the...
The electric capacitance of biological tissues
serves as the basis for numerous medical technologies. For example,
dielectric spectroscopy glucose reading (DSGR) is
a noninvasive diagnostic technique that uses the electric
capacitance of blood to estimate blood glucose levels.
A DSGR device records the electric current that results from
applying a voltage source to the skin and underlying blood vessels.
DSGR can be modeled by the circuit shown in Figure 1, in which V
represents the applied potential, CB represents the...
The electric
capacitance of biological tissues serves as the basis for
numerous medical technologies. For example, dielectric
spectroscopy glucose reading (DSGR) is a noninvasive
diagnostic technique that uses the electric capacitance of blood to
estimate blood glucose levels.
A DSGR device records
the electric current that results from applying a voltage source to
the skin and underlying blood vessels. DSGR can be modeled by the
circuit shown in Figure 1, in which V represents the applied
potential, CB represents the...
The electric
capacitance of biological tissues serves as the basis for
numerous medical technologies. For example, dielectric
spectroscopy glucose reading (DSGR) is a noninvasive
diagnostic technique that uses the electric capacitance of blood to
estimate blood glucose levels.
A DSGR device records
the electric current that results from applying a voltage source to
the skin and underlying blood vessels. DSGR can be modeled by the
circuit shown in Figure 1, in which V represents the applied
potential, CB represents the...