The most accurate way to compare devices is to take two readings at the same time. However, most
people and doctor’s offices do not have the equipment necessary to measure blood pressure from
two devices simultaneously. To take sequential measurements properly requires a pair of initial
measurements to determine the subjects blood pressure level: first with the reference equipment,
followed by 60 seconds, then with the monitor-under-test. The actual accuracy test requires three
pairs of measurements with 60 seconds between measurements. These measurements are averaged
and a comparison can be made. Since most people tend to relax and their blood pressure falls with
subsequent measurements, following this protocol reduces these natural changes in Blood Pressure
levels. The standard technical error of both consumer and professional devices is normally ±3 mmHg, so
a discrepancy of 6 mmHg is acceptable even when the devices are working within their specifications.
Any comparisons without a known “reference device” and not following the procedures described above
will yield unreliable results. In addition, to do an accuracy test properly the reference device must also be
tested to a known reference to confirm its accuracy, prior to being used as the reference for comparisons.
1.2D Calibration
Digital blood pressure monitors do not require regular recalibration, unless the product has been dropped
and internal parts have been damaged. If the unit turns on and does not display an error code, the product
is working properly. In extremely rare cases, the cuff may have developed a pin-hole leak, or the gasket
where the cuff connector enters the monitor may not have a proper seal; both of these leaking air issues
will potentially cause errors in accuracy, but otherwise the product will work accurately without drifting
out of calibration.
1.3 What do your Numbers Mean?
Blood pressures is the pressure in your blood vessels while blood circulates throughout your body.
High blood pressure or “Hypertension” is the pressure at which ones normal average blood pressure
is considered too high and other health risks including: heart attack, stroke, dementia, kidney failure,
heart disease and erectile dysfunction may occur. It is expressed as two numbers: systolic/diastolic
120 mmHg/80 mmHg (mmHg = millimeters of mercury). “Systolic” numbers refer to the pressure on the
walls of your arteries while the heart is contracting and pushing blood. “Diastolic” pressure is the lower
number when the heart is at rest and relaxed. A simple way to understand this is to picture a garden
hose. When the tap is turned on, the immediate pressure on the walls of the hose is the “systolic” value,
and when the tap is turned off it is the “diastolic” number.
There are many different causes of high blood pressure. We differentiate between common primary
(essential) hypertension, and secondary hypertension. The latter group can be ascribed to specific organic
malfunctions. Please consult your doctor for information about the possible origins of your own increased
blood pressure values.
