DINAMAP (Device for Indirect Non-invasive Automated MAP measurement) uses a single cuff wrapped around the patient’s arm and a pneumatic pump to inflate the cuff to a level assumed to be greater than systolic pressure. The cuff is deflated gradually through a solenoid valve. A sensor then measures the tiny oscillations in the pressure of the cuff caused by the pulse. Systolic BP is taken to be when the oscillations start, mean pressure is when they are maximal, and diastolic is when they disappear. A microprocessor controls the pump and solenoid valve. The microprocessor displays the systolic, mean and diastolic pressure and the heart rate.

For the first reading, the cuff is inflated to a suitable high value (around 160 mm Hg), and for the subsequent reading the cuff is inflated to a value about 25 mm Hg above the previous reading. If the initial blood pressure is too high or too low, the device may inflate and deflate repeatedly without displaying the blood pressure. In such a situation, similar to when using manual sphygmomanometer, an estimate of systolic pressure can be obtained by palpating the pulse during cuff inflation or deflation.

Some of the devices measure only systolic and mean pressure, and calculate the diastolic pressure. The microprocessor uses an inbuilt algorithm to calculate the diastolic pressure from the measured systolic and mean arterial pressure, as shown below:

Mean BP = diastolic BP + 1/3 (systolic BP - diastolic BP)