How to work?
Most noninvasive blood pressure monitors use the oscillometric technique. The cuff is placed on the patient's arm, and the cuff bladder is inflated with air until the external pressure exceeds the intra-arterial systolic pressure and arterial flow past the cuff ceases. The cuff bladder pressure is slowly released.
How tight should a blood pressure cuff be?
Wrap the cuff around your arm so it's snug but not too tight. As a rule of thumb, you should be able to slip one finger under the cuff. Place the cuff against your skin, not over your clothing. Lloyd notes not to just push your sleeve up to the top of your arm — doing so forms a tight bend around the upper arm.