Hi John,
The SI Brouchure (8th edition) has a section "Non-SI units accepted for use with the SI, and units based on fundamental constants" which can be found at http://www.bipm.org/en/si/si_brochure/chapter4/4-1.html. This leads into Table 8 of the brochure where the use of "mm Hg" for the measurement of blood pressure is specifically catalogued as being a permitted deviation from "pure SI". The underlying reason is that this unit of measure is used across the entire globe. If the Australian medical profession were to go it alone and use kPa for measuring blood pressure, and Australian medical staff were dispatched to help in a disaster zone, they would have problems communicating with their colleagues from other countries. Air pressure is a different thing - bars convert to kPa by moving a decimal point. _____ From: [email protected] [mailto:[email protected]] On Behalf Of John Candido Sent: 25 August 2011 03:15 To: U.S. Metric Association Subject: [USMA:51014] Millimetres of Mercury & Millibars of air pressure. Hi, I live in Australia and we are predominantly a metric nation. However, we have not been consistent with things such as the measurement of blood pressure in medicine and air pressure in meteorology. The measurement of blood pressure in millimetres of mercury instead of kPa (kilopascals) is a prime example of this inconsistency. A normal blood pressure reading for an adult in millimetres of mercury is 120 on 80, and its equivalent in kPa is 16 on 10. In addition, what about the measurement of air pressure in millibars, which is the current method? Will this be converted to hectopascals of air pressure in the future? Thank you. Sincerely yours, John Candido.
