Earlier the country physicians had their system of knowing whether the person's BP is higher or not. However, it was only in 1733 that an Englishman named Stephan Hales who devised a method of clinically measuring the BP of a horse. He measured its blood pressure by inserting a brass tube into the artery of its leg. The height to which the blood rose inside his tube was the BP of the horse.



Obviously this system was unsuitable for clinical use either in animals or in man. It was later observed that if an artery is pressed from outside, till the pressure just stops the blood flowing through it then the outside pressure is equal to the pressure of blood inside the artery. This outside pressure is then measured and we get what we know now as the systolic pressure. The outside pressure is measured by an instrument known as Sphygmomanometer which is described below.

Sphygmomanometer

It is one of the two instruments needed to measure the BP, the other one being a stethoscope. This instrument, sphygmomanometer, prime facie appears to follow the principle that action is equal to reaction for example. we take a syringe and fill it with some liquid and then press the liquid out.



The pressure, with which it is pressed in, will he equal to the pressure with which the liquid inside is pressed out. This pressure is now calculated on the graduated scale through which mercury or Hg moves. Working on this principle this instrument was devised.

This instrument used in calculating the blood pressure consists of an inflatable cuff via rubber tubes. One of the tubes is connected to a column of mercury with a graduated scale or to numbered gauge. The other tube is connected to the bulb which is used to inflate the cut off. Slightly above the bulb is the circular air-release valve for releasing air out of the cuff.

Another instrument used in calculating the blood pressure is stethescopes. By this instrument the doctor 'hears' the sound of the pulse. When the pulse has ceased to sound it means that blood pressure has stopped flowing through the artery they are applying pressure to.

The process of measuring blood pressure starts with wrapping cuff around a forearm keeping centre of bladder over the artery located at the armpit. The cuff should be secured in such a way that it be neither too tight nor too lose. Having done so, now locate pulse of the artery with thumbo inside front of elbow. Now place the stethoscope end piece over the artery and inflate cuff to 30 ml. of mercury above disappearance of pulse sounds. Now turn valve to deflate cuff slowly and listen for sound of pulse returning. This reading will indicate the systolic pressure. Now continue deflating until pulse sounds disappear, the reading at this point indicates diastolic pressure. The reading to recorded nearest to 2mm Hg. Although it is not advisable for normal persons to try to record their own blood pressure by using these instruments, yet if one is chronic patient, one may record it. Why normal persons are forbidden to do so? It is because such a practice may lead to hypochondria i.e. their getting over concerned about a nonexistent problem. If a normal person measures his BP. repeatedly he might get wrong picture at times. Because, as discussed earlier, during extreme tense moment, a normal person may have his blood pressure shooting very high. If such reading is recorded the person might start thinking him to be a patient. It has been recorded by medical tests that during the academic examination period a healthy normal boy of 20 years may have his BP touching the 200 mark.

In case you are a chronic patient of high blood pressure then you must maintain a chart in the following manner.

                                   B.P. Recording Chart