Cardiac Monitor
The basic method of assessing heart function is thermodilution,
a procedure that involves insertion of a catheter into the pulmonary
artery and is demanding in terms of cost, equipment and skilled
personnel time. For monitoring astronauts in flight, NASA needed
a system that was non-invasive and considerably less complex.
The IQ-Connect interface electronically measures impedance
changes across the thorax to reflect heart function.
In 1965, Johnson Space Center contracted with the University
of Minnesota to explore the then-known but little-developed concept
of impedance cardiography (ICG) as a means of astronaut monitoring.
A five-year program led to the development of the Minnesota Impedance
Cardiograph (MIC), an electronic system for measuring impedance
changes across the thorax that would be reflective of cardiac
function and blood flow from the heart's left ventricle into
the aorta. NASA separately contracted with Space Labs, Inc.,
Van Nuys, California for construction of space qualified miniaturized
impedance units based on the MIC technology. The system was introduced
to service aboard Space Shuttle flight STS-8 in 1983.
ICG clearly had broad potential for hospital applications
but further development and refinement was needed. A number of
research institutions and medical equipment companies launched
development of their own ICGs, using the MIC technology as a
departure point. Among them were Renaissance Technologies, Inc.,
Newtown, Pennsylvania and Drexel University of Philadelphia,
who jointly developed the IQ System®. The system provides
a simple, repeatable, non-invasive way of assessing cardiac function
at dramatically reduced cost; Renaissance states that the cost
of the thermodilution technique runs five to 17 times that of
IQ monitoring. The IQ System is in wide use in hospital Intensive
Care Units, emergency rooms, operating rooms and laboratories
in the U.S. and abroad.
A monitor calculates and displays cardiac output values.
IQ has two basic elements: the non-invasive, disposable patient
interface known as IQ-Connect and the touch screen monitor, which
calculates and displays cardiac output values and trends. The
hardware design of the original MIC was retained but IQ has advanced
automated software that features the signal processing technology
known as TFD (Time Frequency Distribution). TFD provides three-dimensional
distribution of the hemodynamic (blood circulation force) signals
being measured, enabling "visualization of the changes in
power, frequency and time." This clinically proven capability
allows IQ to measure all cardiac events without using estimation
techniques required in some earlier systems.
®IQ System is a registered trademark of
Renaissance Technologies, Inc.
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