From: "Steve Harris" <sbharris@ix.RETICULATEDOBJECTcom.com>
Newsgroups: sci.med
Subject: Re: Distensibility of artery
Date: Fri, 1 Feb 2002 19:23:26 -0700
Message-ID: <a3fitr$kuj$1@slb4.atl.mindspring.net>

"Ares" <kwchan@ee.cuhk.edu.hk> wrote in message
news:a33iu4$s99$1@justice.csc.cuhk.edu.hk...
> Dear all,
>             I would like to know what is the relationship between
> distensibility of artery and the blood pressure in artery? Can I say
> "Distensibility is increased, Blood pressure, including diastolic and
> systolic,  is also increased?
>             Thank you very much!
> Wayne

Distensability and elasticity act to store energy from the pumping of the
heart, so that if they increase, then systolic pressure decreases and pulse
pressure (systolic minus diastolic) narrows. It's exactly the same as what
happens when you put a capacitor across the output of  a DC rectifier in a
power supply.

SBH

From: "Steve Harris" <sbharris@ix.RETICULATEDOBJECTcom.com>
Newsgroups: sci.med
Subject: Re: relationship between heart rate and blood pressure
Date: Tue, 4 Jun 2002 10:34:19 -0600
Message-ID: <adiqia$8q4$1@slb5.atl.mindspring.net>

> "Mark" <mlowry3@bellsouth.net> ?????
> > In a very general sense, yes, there is a relationship between HR and
> > BP.
> >
> > In order to maintain perfusion of tissue, when blood pressure falls,
> > heart rate will rise.  That's why you'll see a compensatory rise in
> > heart rate in a patient with blood loss;  their BP is falling, and
> > their heart attempts to make up for failing perfusion by increasing
> > it's output.

But that depends on how much bloodloss and the age of the patient. Younger
patients with good reserves are famous for maintaining their blood pressure
at the beginning of hypovolemic shock, even though heart rate is going up.


> > To be honest, I don't know if the obverse is true.  I don't believe
> > that a decreased HR necessarily equates to an increased BP.

Again, that depends on the physical shape of the patient.  At SOME low value
of heart rate, BP has to fall for everyone. But before that point, it
depends on how good your heart is, and how well your vascular system
responds by changing resistance.



> > As a
> > matter of fact, I know that particular scenario is not valid.  There
> > are athletes who have both low BP and HR due to increased stroke
> > volume/cardiac output.
> > Mark, MD


Of course. And in people in reasonable cardiovascular shape blood pressure
actually falls as heart rate increases early in an excersize session, due to
the fact that decreased in total resistance in the circulatory system (more
parallel routes opening up in muscles) more than makes up for the increased
cardiac output.

So the final answer is that the body defends a particular blood pressure
across a wide variety of heart rates, but the range of that depends on
cardiovascular fitness (and age), and it's never quite perfect.  At very,
very low heart rates, BP must fall, of course (though some elite atheletes
get down to 30 bpm at night without going into shock).  At very, very high
heart rates, BP can be anything (high, low, or normal) depending on
efficiency of the pump, whether or not it has anything to pump, and vascular
resistance. I've seen young people with normal blood volume, great hearts,
and very high heart rates lying in bed dying from septic shock. They had
cardiac outputs 3 times normal, and might as well have been jogging. The
problem was in their vascular resistance.

SBH

From: David Rind <drind@caregroup.harvard.edu>
Newsgroups: sci.med,alt.health
Subject: Re: Hypertension question
Date: Sat, 22 Mar 2003 11:16:20 -0500
Message-ID: <b5i28r$m4f$1@reader2.panix.com>

dryer_ wrote:
> I have a question I am hoping can be answered by a knowledgeable person
> about hypertension. When I go to my General Practitioner (2 minute drive,
> no wait) my BP was last measured at 106/86. Other times it is usually
> 116/82, 120/80, etc. It generally just doesn't go above 12x/8x when it's
> taken.
>
> I went to a specialist I was referred to for another problem*. I drove one
> hour in heavy traffic, got lost three times, spent time doing the "find a
> parking space" thing. I go in and a med tech takes my BP and it's 136/96.

> I see the doc and she says it's high. I explain the circumstances. She says
> it's still high, even considering that my hourlong drive in heavy traffic.
> I asked if some minor stressor like knowing you're going to get a prostate
> exam would raise it. She said that so-called White Coat Hypertension is a
> myth. Arguing? No, apparently that wouldn't either. I came away with the
> impression that she would have me believe that almost nothing should cause
> BP to rise like that. Is this right?
>
> I have asked EMS personnel (Intermediates, Paramedics) and they said that
> this must be some sort of new finding, because not only does this run
> contrary to what they were taught, it runs contrary to their field
> experience picking up patients, where all sorts of things like a motor
> vehicle accident without any injuries elevates BP.
>
>
> Any insight is appreciated.

1) A single isolated high blood pressure reading on seeing a new
doctor is common. This does not count as what is usually defined
as "white coat hypertension" although that phrase is sometimes
used as shorthand for even a single high reading if a patient is
anxious.

2) White coat hypertension (repeatedly abnormal readings in a
doctor's office with normal readings on home or ambulatory monitoring)
does exist and is not a myth. The exact implications for health
are not completely known, but people with it seem to have risks
for vascular disease somewhat worse than people with normal office
BP readings but better than those with true hypertension.

3) Situational elevations in BP are common and can certainly occur
if someone is anxious or upset.

4) Misreadings of BP in specialists' offices are also common in
my experience. Many specialists do not seem to have larger size
BP cuffs, and so may use a cuff that is too small for the individual
patient. This can lead to falsely high readings.

--
David Rind
drind@caregroup.harvard.edu