Know your Blood Pressure

Know your Blood Pressure

PKGhatak,MD

If you have normal blood pressure and you are middle-aged or older you have a good chance of living well beyond the lifespan of an average person. It is therefore important to know your blood pressure. You should have your Blood Pressure (BP) checked whenever you visit your doctor or a pharmacy. If your BP is normal then check it again in a year or two. BP tends to go up with increasing age, so you do not want to be surprised at a later date when someone tells you –“your BP is high.”

A BP of 110/ 70 mmHg is considered normal pressure irrespective of age – children and pregnant women excluded. Most medical practitioners will call you Hypertensive if your BP is 140/ 90. By the time the pressure rises from 110 / 70 to 140 / 90 many adverse things have taken place in the arteries and the wall of the heart. These changes are still reversible but require lifelong commitments to diet, exercise and lifestyle changes. It is so much better not to have a high BP than to deal with the consequences of hypertension.

The heart is a muscular organ and functions as a circulatory pump. As the blood is pushed out of the heart in the main vessels (Aorta) the pressure of outgoing blood must overcome the resistance of the empty blood vessels in order to flow forward. That pressure at the point of the onward journey of the blood is the first number of the BP reading say 110 mmHg of a BP of 110 / 70. It is called Systolic BP. The elasticity of the wall of the aorta helps to accommodate blood and generates a wave that spreads along the rest of the vessels (Arteries). That wave felt at the wrist is the Pulse. The blood follows the pulse wave in its outward journey. As soon as the heart stops pumping blood the pressure begins to fall. That point on the scale of the decreasing pressure, determined by listening over the artery, is known as the Diastolic BP, here 70 mmHg of a BP of 110 / 70.

A healthy heart beats 72 times every minute. So, each heartbeat lasts only 0.08 seconds (60/70=. 08). Of the 0.08 seconds, the heart pumps 0.03 seconds and relaxes and receives blood from the rest of the body for 0.05 seconds. As a result, the BP fluctuates up and down 72 times a minute as the heart pumps and relaxes. This is the reason two numbers are given in a BP reading; one at the point of maximum pressure called the Systolic BP and the other as the resting pressure known as the Diastolic BP.

Often you wondered which of the two numbers is more important. The systolic BP is a measure of the pumping function of the heart. A failing heart is unable to raise systolic BP, as seen in heart failure and in shock. Diastolic BP is the resistance generated by the walls of the blood vessels. As the elasticity of the blood vessels decreases with advancing age and from the hardening of arteries (atherosclerosis) the diastolic BP rises. In order to pump blood out into circulation, the heart must overcome the resistive pressure by increasing its systolic BP. That produces a strain on the muscles of the heart wall and in the course of time, the muscles thicken and use up more oxygen to do the same work. You must be aware that coronary blood vessels supply the heart muscles with blood, oxygen, and other nutrients. These coronary vessels are pinched as the heart wall thickens and ultimately damages the coronary blood vessels. So, both numbers are important.

Any stress or anxiety can raise the BP but these are temporary causes. Even if one has persistent stress the BP should not be allowed to reach 140 / 90.
Kidney diseases and hormonal imbalances can cause hypertension. The exact cause of hypertension remains unknown in the vast majority of cases. In medicine, if the cause of a disease is unknown it is called Essential and hence elevated BP is called Essential Hypertension. 

Blood Pressure measuring instruments are simple machines. A cuff, made of non-stretchable linen that goes around the arm, has a smaller rectangular rubber bag inside with two tubes attached to it. The end of the short tube is attached to a pressure gauge. The longer tube has a rubber bulb at the end. The rubber bulb has a one-way valve at one end and a release valve near the other end. The cuffs come as small, standard and large sizes. It is important to wrap the cuff around the arm of the person suitable for his size and to place the rubber bag squarely over the artery of the arm. One should easily find the artery by feeling the pulse on the inner side of the arm just above the elbow joint.
The person having his BP taken may be seated or lying on the examination table. The arm of the person should be brought to the level of his heart and kept there. The cuff is then wrapped correctly around the arm, the examiner should feel the pulse with his fingers placed over an artery at the elbow joint. Then squeeze the bulb and raise the pressure to 200 mm Hg. The examiner should note that the pulse is obliterated at this point; if not, he should raise the pressure further and make sure the pulse is cut off. Then release the cuff pressure slowly turning the release valve. As the pressure is lowered the pulse will return and the pressure is read off the pressure gaze. That pressure is systolic pressure. At this point release the pressure completely. And then repeat the process; this time, however, he should place the Bell End of the stethoscope over the artery at the elbow joint and listen for sounds. When the pressure is high enough to cut off the pulse there should be no sound. A" thud" like sound will return as the pressure is lowered. The pressure reading obtained by listening should be almost the same as obtained by feeling a pulse, if not, the reading detected by the pulse is the correct systolic pressure.
The diastolic pressure is detected by sounds only. As the pressure is lowered by turning the release valve the sound at the elbow becomes louder and louder, then suddenly sounds become muffled and then disappear completely. The point at the sound becomes inaudible is the diastolic pressure. There are cases where sound continues to be heard even with pressure at zero, in such cases the point where sounds transit from audible to muffle is noted. This is the diastolic BP
Measuring BP appears a simple task but like many other situations, an accurate reading depends upon the experience of the person.
A careful doctor will take your BP on both left and right arms, and then ask you to stand up and record BP again. There are various reasons for that. Abnormalities of the aorta, effects of certain medications and disease processes can cause alteration of the BP from one side to the other or by a change of posture.
If your primary reason for going to a doctor is checking your BP and the doctor is not checking your pressure himself and delegated that task to his newly hired office assistant, then you are not getting your money’s worth. You may as well buy a digital-readout BP instrument and begin monitoring your own pressure at home. However, you must know these BP instruments are not as accurate as the one described above. But once you have found out how good or bad your instrument is then you can easily correct the instrument readings.

 

revised 2020.