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.
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).
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.)
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:
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
