While the NICE recommendations include general principles for taking blood pressure they do not go into detail about how the BP test should be conducted. Instead, the key guidance on how to conduct a BP test is set out by the BIHS which covers automated and manual measurements separately.^5,9

For automated devices, BIHS says:⁹

• The person should be seated for at least five minutes with the feet on the floor and the back supported, and for the person to be relaxed and not speaking.
• Check the pulse to see that it is regular – if it is not, then use a manual device.
• Support the arm at the level of the heart using a cushion, pillow or arm rest.
• Make sure there is no restrictive clothing on the arm.
• Place the cuff around the upper arm, 2cm above the brachial artery and aligning the artery mark.
• Use the cuff size recommended by the device’s manufacturer.
• The air bladder should encircle at least 80% of the arm, but not overlap on itself.
• Advise the person whether you will do a series of single readings or whether the machine will automatically inflate and reinflate.
• Take an initial reading from each arm and then use the arm that gave the higher reading to take three separate readings.

For a manual BP reading, once the cuff is fitted, the estimated systolic pressure should be found first. This involves feeling for the brachial artery, inflating the cuff until the pulsation disappears and then deflating the cuff.⁹

To measure the BP, reinflate the cuff to 30mmHg more than the estimated systolic pressure, and then put the stethoscope diaphragm over the brachial artery. Deflate the cuff at around 2-3mmHg per second while listening for regular tapping sounds. The systolic pressure when the sound appears and the diastolic pressure when the sound disappears should be measured to the nearest 2mmHg.

For people with very large upper arms where a cuff bladder is not able to cover at least 80% of the arm, the device manufacturer may be able to supply a larger cuff. Alternatively, a wrist BP measurement, with the wrist supported at the level of the heart may be the best alternative.