Hello jat
The search of material on this topic is complicated by large
number of repetitive articles explaining hypertension disease,
information for patients, recommended remedies
Sorting out those articles, that we find some basic description of physics
From simple explanation, which explains how big the swing
(from systolic to diastolic) is, and what is being measured:
http://courses.science.fau.edu/~rjordan/rev_notes/blood.htm
To more technical overviews:
HUMAN BLOOD FLOW MEASUREMENT AND MODELING
... Blood vessels provide a tubular network to channel the blood to every
This model for flow rate in elastic tubes provides ...
www.math.uwaterloo.ca/~kpwilkie/bloodflow.pdf
and finally complex technical articles,
many describing computer models of the
hydrodynamic flow of a fluid (blood) in elthe astic channels.
For your purpose, most suitable may be these articles:
Readings from Scientific American -bibliography
http://oak.cats.ohiou.edu/~piccard/scientam/
in particular these two:
1/59 54
The Microcirculation of the Blood." The mechanisms that regulate blood flow.
1/68
The Venous System." Wood; deals with pressure and fluid flow dynamics
of the cardiovascular system.
which would be available in the library. They probably can be
purchased for on-line delivery., more info at
http://www.sciam.com/article.cfm?articleID=0001D598-F071-1CB8-B4A8809EC588EEDF&sc=I100322
I will provide a list of additional references bellow,
as they may be of possible interest, but first I want
to address your specific questions:
>> loss of flexibility can markedly impact the mmHg reading for systole
Yes. The comin references above, measures sum of two effects:
1)blood pressure and 2)elasticity of the blood vessel.
The second factor is much smaller and is neglected in common procedure.
It is small for both young and healthy tissue
and for aged, sclerotic veins and arteries.
The typical blood pressure of about 120 mm Hg
is more then pressure needed to flex (an empty) typical blood vessel.
How much less - that's a whole field of research:
Examples:
1) In one experiment, effect of 250 MAG of caffeine which causes
stiffening is 11/8 mm Hg
http://my.webmd.com/content/article/16/1817_50966
2) Cross-sectional studies have shown that aortic and carotid
stiffness (evaluated by the pulse wave velocity
increase with age by approximately 10% to 15% during a period of 10 years
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12460708&dopt=Abstract
So, two efffects exist. 1) The usual, non-invasive measurement,
measures blood pressure with stiffness of the
vessel added, and 2) As arteries harden (with age,..) the
higher pressure is needed to deliver the blood, being the second
cause, next to narowing of the channel.
The affect of narrowing of arteries is stronger, and localized
narrowing you mention, will increase pressure on the whole section.
The pressure gets lower as we progress from larger vessels to
the capillaries. There is more on this on the more technical
publications listed below.
ADDITIONAL REFERENCES
Here are some additional references to material available on the net:
history - theory and details of measurement
http://homepages.uel.ac.uk/M.S.Meah/bs250page4clec3.htm
http://hypertextbook.com/physics/matter/pressure-fluid/
Effect of wall elasticity and other factors that Affect Blood Pressure
... Factors Affecting Blood Pressure Vessel Elasticity Blood Volume
Cardiac Output Blood Vessel Diameter ...
http://education.adam.com/products/ipie/iguide/ Fact_Aff_Blood_Pressure.pdf -
50 pages report of conference on measurement techniques - not
too relevant but gives
measurement errors (+/- 8 mm HG) p14
www.nhlbi.nih.gov/health/prof/heart/hbp/bpmeasu.pdf - Similar pages
simulation - complex math model
... was also considered in an elastic pipe and simulations ..
. assessment of lattice Boltzmann hydrodynamics and boundary
... Analysis of 3D transient blood flow passing
...
www.maths.strath.ac.uk/~aas99101/reports/pisapaper.doc -
symposium
http://www.eps.org/aps/meet/DFD03/baps/abs/S1090.html
the shape of the blood vessel becomes unstable at high blood
pressure if the inner radius of the vessel becomes perturbed.
http://physicsweb.org/article/news/2/10/11
Model -advanced math (describes pressure as function time )
http://arxiv.org/abs/physics/9806032
Search Terms: Hydrodynamics (physics) blood pressure
channel flow, elastic flow, blood
hedgie |
Clarification of Answer by
hedgie-ga
on
26 May 2004 05:39 PDT
1) The numbers refer to a bibliography - list of papers on this page:
http://oak.cats.ohiou.edu/~piccard/scientam/fluids.html
titled
Readings from Scientific American
List was compiled by a professor Richard D. Piccard who says:
" This list of articles has grown from one that was
originally compiled by the Spring, 1979, class of Medical Physics at
Kalamazoo College. It is
indexed
into 13 categories, with the articles listed in chronological order
within each group. The 13 topics, listed above, were chosen with an
eye to the organization of the
text used in that course (Medical Physics, by Cameron and Skofronick),
but with the hope that they would prove useful in other contexts. The
listing is substantially
complete from 1952 through 1981, and includes some more recent refrences.
If you do not have access to a library with back issues of the
magazine, I would suggest that you contact the publisher:
http://www.scientificamerican.com/ "
I assume that first number is year/month and second a page in that
issue of the Scientific American magazine.
Sometimes it takes some clicking around to find these details,
I should have included that, not assume that you will find that.
2) I apologize about the
"comin references" that is some strange
misprint, perhaps induced by spellchecker, which I did not catch,
not a typo for 'comming' .
What I meant is this:
According to the explanation in the references above, the instrument
measures pressure at which the blood stops flowing (as determined by
listening to the sound).
That happens when the channel in the artery is squeezed to zero clearance.
For that:
1) the wall of the artery has to be flexed againt it's own resistance
2) the pressure of the liquid inside the channel has to be overcome
The two forces do add. Im a more rigid pipe, e.g. metal) the force
needed to deform the pipe could exceed the resitance of the fluid.
In case of the artery, even aged artery, the force needed to flex the
'pipe' is much less then resistance of the fluid (the actual blood
pressure).
difference is neglected. The net blood pressure can be determined by the
invasive measurement, the force needed to flex an empty artery can be measured
(e.g. during an autopsy) - which is how we know the seond is much smaller
(10 vs 120 mm Hg).
Please do ask for additional explanation as needed.
I will be more carefull with my typing.
hedgie
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