Re: [USMA:37948] RE: Australia's blood pressures measured in kilopascalsPat, in
the healthcare world, a blood pressure of 117/75 is instantly understood,
despite the lack of metrological integrity.
Here in the U.S., you would also cringe to hear the symbol for square meter to
be uttered as "meters squared," but I hear people do it all the time. They see
a letter "m" with the exponent, and won't announce it as "square meters."
This is the land of the inchified centimeter (grin).
----- Original Message -----
From: Pat Naughtin
To: U.S. Metric Association
Sent: 07 Feb 13,Tuesday 23:49
Subject: [USMA:37960] RE: Australia's blood pressures measured in kilopascals
Dear Bill,
I have interspersed some remarks in blue.
On 2007 02 14 6:15 AM, "Bill Hooper" <[EMAIL PROTECTED]> wrote:
On 2007 Feb 13 , at 11:45 AM, Pierre Abbat wrote:
What is 120/80, or whatever else anyone
has? Is it a gauge pressure ... ?
Yes, it is "gauge pressure", that is, pressure above the surrounding
pressure (atmospheric pressure). It is in mmHg and the two values usually
quoted are systolic and diastolic. Systolic is the pressure of the impulse when
the heart contracts, forcing blood through the blood vessels. Diastolic is the
pressure between beats, when the heart relaxes.
And care needs to be taken that the blood pressure is taken at the same
height as your heart. This is why you have the cuff placed around your upper
arm at heart level. I believe that blood pressure can also be taken on any part
of your arm or even your leg if you are lying down - when that blood pressure
cuff is still placed level with your heart.
The gauge pressure is the only meaningful pressure, here. If the heart does
not beat at all (if you're dead), the pressure is 760 mmHg because the body is
subjected to atmospheric pressure (equal to 101.3 kPa).
So an actual (rounded) pressure in your blood might be 760 mmHg plus 10 kPa =
111 kPa
One cmHg equals 1.333 kPa, so 1 mmHg = 0.1333 kPa.
(Millimetres of mercury (Hg) may be preferred but
cmHg has an easier to remember conversion factor to kPa,
namely one and a third, or 4/3.)
I try to avoid making conversions easy. I think that the only future
following a conversion is continual conversions back and forth between the
various values. I am watching the world's political leaders try to come to
terms with global warming at the same time as the various energy factions
(coal, nuclear, oil, solar, wind, etc) all clamor for lobbying attention as
they scream their own peculiar energy units (tons or short tons of coal, atomic
energy units of nucular energy, barrels of oil, and kilowatt-hours of solar or
wind energy).
My blood pressure, taken just now, is 117/75 (in mmHg) as given by my blood
pressure gauge.
(It is commonly written with the systolic and diastolic pressures separated
by a slash.
The slash does not imply division.)
Those figures above convert to:
What a muddle! If I am told that 'your blood pressure is 117 over 75', I then
have to know:
a.. that the unit used to measure blood pressure is a millimetre of mercury
b.. that two blood pressures have been measured: systolic blood pressure
and diastolic blood pressure
c.. that these are gauge pressures and not an absolute or real pressures
d.. that these two pressures are commonly written separated by a slash
e.. that the slash used does not imply division, it is simply used a
separator of the two different pressures
15.6 kPa / 10.0 kPa.
My doctor says my blood pressure is fine.
Bill Hooper
1810 mm tall
BP 15.6/10.0 kPa
Fernandina Beach, Florida, USA
I would rewrite this to read:
My doctor says my blood pressure is fine. He says my systolic pressure is 16
kilopascals and my diastolic pressure is 10 kilopascals.
(Note the use of direct metrication without any reference to conversion,
without fractions or decimals, and without any of the confusion brought about
by deliberate obfuscation.)
Cheers,
Pat Naughtin
PO Box 305 Belmont 3216
Geelong, Australia
61 3 5241 2008
Pat Naughtin is manager of http://www.metricationmatters.com an internet
website that focuses on the many issues, methods and processes that
individuals, groups, companies, and nations use when upgrading to the metric
system. Contact Pat Naughtin at [EMAIL PROTECTED]
