Xref: utzoo sci.med:8896 sci.physics:6035 sci.electronics:5229
Path: utzoo!attcan!utgpu!lharris
From: lharris@gpu.utcs.toronto.edu (Leonard Harris)
Newsgroups: sci.med,sci.physics,sci.electronics
Subject: Re: Biomedical Measurement "Challenge": Cardiac Output
Keywords: biomedical measurements, cardiac output, instrumentation
Message-ID: <1989Feb19.161324.2076@gpu.utcs.toronto.edu>
Date: 19 Feb 89 21:13:24 GMT
References: <13175@steinmetz.ge.com>
Reply-To: lharris@gpu.utcs.UUCP (Leonard Harris)
Organization: University of Toronto Computing Services
Lines: 56
Checksum: 59360

In article <13175@steinmetz.ge.com> oconnor%sungod@steinmetz.UUCP writes:
>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"

Get yourself a Swan-Ganz catheter - put it into the internal jugular or
subclavian and thread it into the left vatrium.  Inject saline or water of
a known temperature and measure the temp of the saline at the tip of the swan
ganz using the temperature probe incorporated.  The decay curve of temperature
gives the cardiac output.