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From: oconnor@nuke.steinmetz (Dennis M. O'Connor)
Newsgroups: sci.med,sci.physics,sci.electronics
Subject: Re: Biomedical Measurement "Challenge": Cardiac Output
Keywords: biomedical measurements, cardiac output, instrumentation
Message-ID: <13175@steinmetz.ge.com>
Date: 17 Feb 89 18:52:26 GMT
Sender: news@steinmetz.ge.com
Reply-To: oconnor%sungod@steinmetz.UUCP
Organization: GE Corporate R&D Center
Lines: 49

An article by larry@kitty.UUCP (Larry Lippman) says:
] 	Now the problem: how can we measure cardiac output without
] major surgery to expose the aorta and attach a flowmeter?

Well, you could :
Inject the subject with a technicium bound into a pyrophosphate compound
and place the subject in front of a gamma-ray camera. Record the amount
of gamma-rays ( = k*amount of technicium = K*amount of blood ) in the
heart using a timescale much finer than a single heartbeat. Calculate
the difference beteen the maximum amount of blood in the ventricle
during a heartbeat and the minimum amount. Multiply by beats/time-unit
to obtain a flow rate. This technique assumes all the valves in the
heart are functioning correctly.

Or, you could :
Use doppler ultrasound on the aorta to measure the velocity, and use
an NMR or CAT scan to determine the cross-section, and multiply to
obtain the flow rate.

Or you could :
Inject a VERY small transmitter ( about the size of a red blood cell
would be nice, even though that will get stuck in the capillaries ) into
a major vein that broadcast a long pseudo-random number and track it
using multiple ( at least three ) recievers, using the delay to each
receiver to precisely locate the unit, and measure it change in position
as it flows through the aorta, then use an NMR or CAT scan to determine
the cross-section, and multiply to obtain the flow rate.

Or you could :
Use bolus injection of a radioisotope and see how quickly it moves to
and through the aorta using a gamma-camera, then compute the flow
as you did for the radio transmitter.

Or you could :
Compute the velocity of the flow out through the valve by analysis of
the noise it makes as it passes through, then proceed as abover to get
the volume of material going thrnough.

I thought of heating a section of the aorta with microwaves or
a particle accelorator and measuring the cooling rate, monitoring
the temperture with a fiber-optic thermometer ( we could use
the same fiber to heat it with a laser, come to think of it ) or
monitoring the temperature with NMR sensors, but this seems a bit
invasive to me ( although not as bad as inserting a flowmeter ).


--
 Dennis O'Connor   oconnor%sungod@steinmetz.UUCP  ARPA: OCONNORDM@ge-crd.arpa
  "...the bastard got away. God always fights on the side of the bad man"