sometimes called the Impedance Cardiography (ICG)

**B. Bo Sramek, Ph.D.**

(For explanation of terms new to you, go to Glossary of Terms)

A new generation of TEB technology, discussed below, is an accepted, main stream
technology for noninvasive, continuous measurement of **global blood flow** (Cardiac
Index, CI - the global blood flow per minute, and Stroke Index, SI - the global blood
flow per beat)**,** **respiration and a host of cardiodynamic parameters.
** The

The **TEB level **(the Base Impedance, )[]
is **indirectly **proportional to **total **content of thoracic fluids, however,
it cannot identify individual conductance contributions of the intravascular, intra-alveolar
and interstitial compartements. Instead of ,
TEBCO^{®}, therefore, measures and displays its inverted value, i.e., the **Thoracic
Fluid Conductivity, TFC [**1**/],**
which is then **directly proportional to the total thoracic fluids content.**

The
**TEB variations and changes** (Z)
are produced by:

**slow changes of fluid levels**in all thoracic compartments - a result of postural changes or, for instance, pulmonary edema,**tidal changes of venous and pulmonary blood volume caused by respiration**(from these changes TEBCO^{®}measures and displays the**Respiratory Rate, RR**),**volumetric**(plethysmographic)**and velocity**(alignment of planes of erythrocytes as a function of blood velocity) changes of**aortic blood**produced by the**heart's pumping**(cardiodynamic)**activity.**

The **rate of cardiovascular TEB changes** over time (dZ/dt) [i.e., the first
derivative of Z]
is an image of the **aortic blood flow.** Its **maximum value, [(dZ/dt) _{max}],**
is proportional to the

The **maximum rate of the second derivative of Z [(dZ/dt)max],**
is, therefore, an image of the **maximum acceleration of aortic blood flow** -
a true measure of inotropic state, essentially independent of preload and afterload
*(a detailed discussion and physiologic explanation of these phenomena can be found
in the Chapter 7, Hemodynamics of the cardiovascular system, in the textbook
Biomechanics
of the Cardiovascular System*

The timing landmarks on ECG (specifically the Q-time of the QRS complex) and on
the dZ/dt signal enable measurement of the **Systolic Time Intervals,** namely
the **Ventricular Ejection Time, VET,** and the **Pre-Ejection Period, PEP.**

The TEBCO^{®}-measured parameters, i.e., the TFC, VET, EPCI, in conjunction
with the **Volume of Electrically Participating Tissues, VEPT** (a function of
patient's gender, height and weight), are used to calculate the **Stroke Volume,
SV,** according to **Sramek's Equation:**

Note 1:This equation reflects the physiologic basis of SV determination: (a) SV is directly proportional to the physical size of a patient (i.e., to VEPT - body habitus scaling constant), (b) SV is directly proportional to duration of delivery of blood into the aorta (i.e., to VET), and (c) SV is directly proportional to the peak aortic blood flow (i.e., to EPCI).Note 2:This equation corrected most of the deficiencies associated with the original TEB Kubicek's equation, used in the '70s.

The **Systolic Time Intervals** are then used to calculate an **estimate of**
**Ejection Fraction, EF,** as

When SV is normalized by the** Body Surface Area, BSA, **the **hemodynamically-significant
blood flow** parameter called the **Stroke Index, SI,** is calculated as

**BSA** [m]
is a complex function of a patient's height and weight, calculated by TEBCO** ^{®}**
from the DuBois & DuBois formula:

The **perfusion significant blood flow** - the **Cardiac Index, CI,** is
then calculated as

Please view the**
TEBCO data presentation** to see the four processed analog waveforms, the list of 10
measured cardiodynamic parameters and their physical dimensions.

Click here for the **List of scientific papers related to new
TEB** utilizing the Sramek's equation.