Everything you need to know about sphygmomanometers

One of the tricky ways of figuring out what’s going on inside the body without cutting it open to have a look, we can quite easily gauge our internal temperature by putting a thermometer in our mouth, get an idea of how often our hearts are beating by taking our pulse, but what about the other classic, the blood pressure?

The force exerted by the blood on the wall of a blood vessel is called the blood pressure. Blood pressure is measure by an instrument called sphygmomanometer. This pressure is greater in the arteries than the veins.  The pressure in the artery during ventricular contraction is called systolic pressure and the pressure in the artery during ventricular relaxation is called diastolic pressure. The normal systolic pressure is 120 mm of Hg and diastolic pressure is 80 mm of Hg.

The first real blood pressure measurements were taken in 1733 by an English clergymen, he stuffed a glass tube into an artery of his own horse, where he noticed that the blood level went up and down to the beat of the horses heart, that method seemed obviously dangerous and he thought that there got to be something else he can make that will do the job, but he was facing problems finding the right solution.

In the 1800’s an Italian doctor realized that he could measure the blood pressure without having to create an open wound. Dr. Scipione Riva-Rocci was the first person to design an inflatable cuff that would fit the patient’s arm and he attempted to build his original sphygmomanometer out of everyday objects. His theory was that the pressure required to cut off the blood flow in an artery would be the same as the maximum blood pressure in that artery, that certainly cuts off the blood supply, he thought that now he just needs to attach the instrument he designed to a sensitive gauge to figure out what pressure that is.


There are couple of types of sphygmomanometers, manual and digital.


  • Manual sphygmomanometers are used in conjunction with a stethoscope. Some manual sphygmomanometers contain mercury. Manual Sphygmomanometer is the more conventional home blood pressure unit and it detects the blood pressure through the arteries in the arm. 
  • There is also another type of sphygmomanometer called Aneroid sphygmomanometer, which has a manual pump to pump the patient’s blood pressure cuff. 
  • Digital sphygmomanometer use batteries and they all have LCD screens that display the patient’s blood pressure.


These are the basic steps of measuring the blood pressure using a stethoscope and sphygmomanometer.

This is an introduction into the use of the basic diagnostic equipment, which can be commonly found in the clinical setting. For the examination of the cardiovascular system, we shall describe the use of the stethoscope and sphygmomanometer. Before using both devices you must ensure that you are familiar and competent in the use of the diagnostic equipment before examining the patient. You must check that all your medical equipment is functioning properly and that you the necessary spare or disposable components. Ensure that the equipment is clean and that the components are changed the moment you finish examining the patient.

Manual, digital or aneroid sphygmomanometer equipment includes a cuff, attached pump, stethoscope and a gauge. This type of equipment requires coordination and it can sometimes be difficult to use if you have a hearing or visual problem or even if you are unable to perform the hand movements needed to squeeze the bulb and inflate the cuff. When you are ready to take your blood, pressure sit quietly for three to five minutes before hand. To begin place the cuff on patient’s bare upper arm one inch above the bend of the elbow. Pull the end of the cuff so that it’s evenly tight around patient’s arm. You should place it tight enough so that you can only slip two fingertips under the top edge of the cuff. Make sure your skin doesn’t pinch when the cuff inflates. Once the cuff is on, place the disc of the stethoscope face down under the cuff just to the inner side of the patient’s upper arm. Next you need to place the stethoscope earpieces in your ears with the earpieces facing forward pointing toward the tip of your nose.

Next you need to rest the gauge in the open palm of the hand of your cuffed arm, so that you can clearly see it, then squeeze the pump of the sphygmomanometer rapidly with your hand until the gauge reads 30 points above the patient’s usual systolic blood pressure. After you reach this point, stop squeezing and turn the knob on the pump toward you to let the air out slowly. Let the blood pressure fall 2mm or lines on the dial per second while listening for the patient’s heart sounds. Note the reading when you first hear the heartbeat. This is the patient’s systolic pressure. Note when you no longer hear the beating sounds. This is the diastolic pressure. Ask the patient to rest quietly, before taking another measurement. Record the numbers by writing the information down or by entering the information into electronic personal health record.