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UVMFLOWNET  May 2009

UVMFLOWNET May 2009

Subject:

Re: new subject - blood pressure

From:

Reinhard Volkmann <[log in to unmask]>

Reply-To:

UVM Flownet <[log in to unmask]>

Date:

Sat, 9 May 2009 04:42:28 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (94 lines)

We have noticed that too, Lisa, and it can be also be observed when
measuring intraarterial pressures invasively (especially when experimenting
with a cuff distally to the needle): There is often a pressure difference
between the first tiny flow signal and the first noticed Korotkoff tone of
about 5-10 mmHg. Making a stop flow condition with an inflated cuff to supra
arterial pressures increases the intravascular blood pressure to the static
level of the so called end-pressure value proximally to the cuff with about
10 mmHg. The artery proximal to the cuff behaves then like a static pressure
katheter. If a blood flow transient is sudddenly starting, there is an
energy loss making the lateral opening pressure to drop with those approx.
10 mmHg. So, decreasing the cuff pressure from a stop flow condition results
in a critical vessel opening just below the end-pressure level
(lateral-pressure = end-pressure during stop flow). The first flow transient
makes en energy drop by its dynamic pressure head and the corresponding
lateral pressure drop results in critical closing of the vessel (closing is
not evoked by the pressure drop through the cardiac circle - you would
observe this even in static d.c. pressure conditions). If you wait for the
new increase in static pressure, the vessel will open again shortly after a
while etc. But everybody decreases the cuff pressure by 5-10 mmHg resulting
in new flow transients at lower lateral pressures and corresponding
Korotkoff tones. So, I believe the difference you observed in your study is
the difference between the intravascular end (static) blood pressure and the
lateral critical opening (dynamic) pressure. The lateral dynamic pressure
values result in clear Korotkoff tones which are dependend on the cardiac
pump characteristics. 

Reinhard

On Fri, 8 May 2009 16:00:11 -0700, Lisa Mekenas <[log in to unmask]> wrote:

>Don,
>Many years ago, remembering that I was taught that Stethoscopes get the
pressure from the sound the blood makes when in enters the artery and exerts 
>Pressure on the wall vs with PW we get the pressure as it enters the artery.
>I did a study and took BP with a stethoscope and then with the PW.
>My prelim results were that the PW pressure was on the average 5-8 mmHg
greater than the stethoscope. That was using the first sound-not waveform
seen as this was with an older parks that you had to run the paper.
>
>I never compiled the results or took the average age,ect--just thought
>Who would be interested in something so not significant. I only did about
50-60 patients.Threw all that old stuff away last year when I cleaned out
the garage, getting ready to do another sweep this year.
>I've worked with techs who said they use the 2 or 3 beat on all pressures
and that since they did it that way it didn't matter because the ratio would
be the same??  Definitely not my way of thinking. I go by the sound still
and find the Parks correlates well with the waveform anyway.
>Lisa 
>
>
>-----Original Message-----
>From: UVM Flownet [mailto:[log in to unmask]] On Behalf Of Don Ridgway
>Sent: Friday, May 08, 2009 1:46 PM
>To: [log in to unmask]
>Subject: Re: new subject - blood pressure
>
>By "visual" do you mean the needle bouncing on the dial? Or a PPG tracing?
A digital strain gauge?? That would be very retro.
>
>Don Ridgway
>
>
>
>
>
>-----Original Message-----
>From: UVM Flownet on behalf of subscribe uvmflownet Elizabeth Gault
>Sent: Fri 5/8/2009 7:14 AM
>To: [log in to unmask]
>Subject: new subject - blood pressure
> 
>
>
>Got an interesting question today from an intern. If we do pressures for
ABI's and use the visual to pick the first beat and the Dr's office is using
a stethoscope and using the first audible beat is there a valuable
difference? The intern says the Diabetic association wants the BP under 120
and if we show it over and the Doc's office is under who is right?� thanks 
>
>
>
>To unsubscribe or search other topics on UVM Flownet link to:
>http://list.uvm.edu/archives/uvmflownet.html
>
>
>To unsubscribe or search other topics on UVM Flownet link to:
>http://list.uvm.edu/archives/uvmflownet.html
>
>To unsubscribe or search other topics on UVM Flownet link to:
>http://list.uvm.edu/archives/uvmflownet.html

To unsubscribe or search other topics on UVM Flownet link to:
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