As I understand the situation there is no defined method of determining the point at which B.P. readings are recorded. Each manufacturer uses their own algorithm (obviously designed to give a similar result to a manual method). This means that different manufacturers instruments may give different results when measuring the same dynamic situation, e.g. B.P. simulator (which also has its own assumed calibration). Automatic machines should give good repeatable results from a source and show trends very accurateley (which is what they were initially developed to do) Also of course the static pressure readings during calibration should be accurate within a few mmHG.
What I think is most alarming is the way that "observations" are carried out by automatic machines operated by people who often do not have the qualifications/experience to observe a patients condition.
There is a useful trend at the moment to do initial/clinical evaluations using the old manometer/stethoscope method to assess the patient before resorting to the automatic machine to show the patients progress/response to treatment, over time.
