Xref: utzoo sci.med:8950 sci.physics:6080 sci.electronics:5316
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From: sac@conrad.UUCP (Steven A. Conrad)
Newsgroups: sci.med,sci.physics,sci.electronics
Subject: Re: Biomedical Measurement "Challenge": Cardiac Output
Keywords: biomedical measurements, cardiac output, instrumentation
Message-ID: <157@conrad.UUCP>
Date: 23 Feb 89 01:52:30 GMT
References: <13175@steinmetz.ge.com> <156@conrad.UUCP>
Reply-To: sac@conrad.UUCP (Steven A. Conrad)
Distribution: usa
Organization: Louisiana State University Medical Center, Shreveport
Lines: 22

In my previously submitted article, I neglected to mention a method
which has recently hit the market, thoracic bioimpedance.  The
method involves running a constant current through the chest by
means of electrodes placed at the neck and base of the thorax, and
measuring voltage changes.  A sufficiently high frequency is used
so as not to intefere with biological function.  Equations have been
worked out for relating the rate of change of impedence with each
stroke of the heart to the volume ejected by the heart (stroke volume).
Multiply this by heart rate and you have cardiac output.

We have evaluated this instrument and found it to be of sufficient
accuracy for clinical uses.  It perhaps best supplements, not replaces
the pulmonary artery catheter, since the catheter has other important
functions.  Several investigators have reported reasonable correlations
with thermodilution.

	Steve
-- 
Steven A. Conrad,  Department of Medicine (Critical Care)
Louisiana State University Medical Center, Shreveport, LA
UUCP: sac@conrad.UUCP,   Internet: conrad@manta.pha.pa.us
"Silence  is the only  successful  substitute for brains"