It is believed that blood pressure was measured for the first time, in animals by an Englishman called Stephen Hales in 1733. He measured the blood pressure in a horse by inserting a brass tube into the artery of its leg. The height to which the blood rose inside this tube was the blood pressure of the horse. Obviously, this method is 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 call the systolic blood-pressure. The outside pressure is measured by an instrument known as Sphygmomanometer or simply high blood pressure measuring instrument.
Use of the Sphygmomanometer:
For the measurement of blood pressure one requires two instruments – a sphygmomanometer and a stehoscope. Sphygmomanometer, an instrument for measuring blood pressure, consists of an inflatable cuff connected via rubber tubes – one to a column of mercury with a graduated scale or to a numbered gauge and the other to the bulb which is used to inflate the cuff. Just above the bulb is the circular air-release valve for deflating the cuff.
How to Measure Your Blood Pressure:
” Place sphygmomanometer on table. Sit beside it and place arm on table at heart level.
” Wrap cuff around forearm keeping centre of bladder over the artery located at the arm pit. Secure cuff so it is not too tight or loose. It can be put on over a shirt sleeve which should not be rolled into a tight band.
” Locate pulse of the artery with thumb inside front of elbow.
” Place stethoscope endpiece over artery and inflate cuff to 30 millimetres of mercury above disappearance of pulse sounds.
Turn valve to deflate cuff slowly and listen for sound of pulse returning. Continue deflating until pulse sounds disappear, the reading at this point indicates diastolic pressure. Occasionally the sounds do not disappear, in which case, the point at which sounds take on a different, muffled quality indicates diastolic pressure. Record pressures to nearest 2 mmHg. Always deflate cuff completely before repeating measurement.
Monitoring Your Blood Pressure:
physicians generally do not recommend that people whose blood pressure is within a normal range monitor their own pressure regularly. Such practice, they say, may lead to hypochondria i.e., overconcern abort a non-existent problem.
But those who are suffering from high blood pressure may benefit themselves by taking their own blood pressure at different times of the day to determine their average reading. One can avoid the tension one might feel in the physician’s clinic by relaxing at home before one takes one’s blood pressure. One can take it everyday or several times a day if one is advised by the doctor to do so, and report one’s physician any changes one observes in the entire pattern of blood pressure recordings. Another advantage is that self-monitoring will serve as a reminder to take one’s medication or to adhere closely to the diet and exercise routine recommended by the doctor.
Special Tests to Diagnose Primary Causes of High Blood Pressure:
Usually, measuring the blood pressure along with other clinical examinations may be enough for your doctor to treat you in case of a blood pressure problem. At other times the physician may need more information and he may ask for certain special tests in order to obtain information on the possibility of any primary cause for the hypertension. In such cases, tests may have to be carried out to check:
” Enlargement of heart through X-ray and ECG.
” Kidney function through pyelogram
” Adrenal Glands involvement
The information obtained will make it possible to treat the primary cause if present and thus enable the doctor to effectively control your high blood pressure.
Tests for Kidney Function:
Sometimes, in the case of secondary high blood pressure, kidney involvement may be suspected and hence a kidney function test is generally called for. In some kidney diseases, the blood supply, to the kidney may be reduced. The kidney thus deprived of blood, secretes a chemical substance in the blood which raises the blood pressure. Examination of blood and urine can often indicate the condition of a person’s kidneys e.g. when protein leaks into the urine, it is an early indication of kidney damage. Again, if the kidneys are not functioning properly, waste products begin to build up in the blood and can be detected by chemical analysis.
The kidney can also be X-rayed using a special technique called Intra-venous Pyelography. In this test an iodine-based dye is injected into a vein of the patient. This dye is rapidly removed from the blood by the kidneys. As the dye is opaque to X-rays, the position and size of the kidneys show up well in the X-rays, thus clearly showing abnormalities, if any, in the kidneys.
Tests for Enlargement of Heart and the Condition of the Heart:
When a person has high blood pressure and it goes undetected for a long time, the heart comes under increasing strain and the muscle of the heart begins to thicken and enlarge. The enlargement of the heart can often be detected by an X-ray of the chest. A more accurate test would be an electrocardiogram or ECG which is nothing but a recording of the electrical activity of the heart by a machine.
In extremely rare case, a benign tumour of one of the endocrine glands may lead to high blood pressure. The gland in question is mainly the adrenal gland which secretes Adrenaline, a blood pressure raising substance. The tumour acts by producing excessive amounts of Adrenaline and thus leads to high blood pressure. Tests for detecting this condition consists in collecting the patient’s urine for a full 24 hours in a special bottle. Subsequently the amount of Adrenaline in the urine is measured and in this way an adrenaline-secreting tumour is detected.
Electrocardiogram (ECG) is a recording of the electrical activity of the heart on a moving graph paper strip. The ECG tracing is recorded by means of an apparatus called an electrocardiograph. It aids in the diagnosis of heart disease. The physicians diagnose the heart disease by seeing the characteristic changes in the ECG.
The ECG machine with all its wires and leads may look scary to the layman, when he first makes its acquaintance. In real fact, it is simply a machine to record the electrical activity of the heart in order to obtain a comprehensive picture of the condition of the heart.
Electrodes connected to the recording apparatus, i.e ECG machine, are placed on the skin of the four limbs and the chest wall.
The contraction of any muscle is associated with electrical changes which can be detected by electrodes attached to different points on the surface of the body. The purpose of recording the ECG from several different leads is to electrically look at the heart from many different directions. For taking an ECG, metallic electrodes which are held in contact by rubber straps, are placed on the forearms, legs and over the chest of the patient. A complete ECG may have 6 standard leads “looking at” the heart in a vertical plane and 6 more leads which “look” at the heart in a horizontal plane from the front and the left side.
Consequences of High Blood Pressure:
High blood pressure may or may not give rise to the tell-tale symptoms described for such as headache, dizziness, tiredness, palpitation of the heart etc. But high blood pressure is far more important from the clinical point of view because of its consequences. Chronic high blood pressure, when left untreated, may prove fatal and sometimes causes serious complications. The frequency of these complications will depend upon the length of time and severity of high blood pressure. The complications caused by high blood pressure are irreversible changes produced in the small blood vessels of the heart, brain, kidneys, eyes and the arteries of the limbs particularly the legs. These, in turn may lead to – stroke, paralysis, coronary heart disease, heart failure, kidneys failure, blindness, rupture of the blood vessels and claudication.
The effects of high blood pressure on organs such as the brain, the kidney and the heart are the direct result of 1. complete obstruction of the blood-supplying vessel, 2. diminished blood supply to the organs and 3. sustained involuntary muscular contraction, i.e. spasm of the blood vessel which in its own special way diminishes or temporarily cuts off the blood supply.
Effects of High Blood Pressure on Heart:
- Myocardial Infarction
In medical science it is considered to be the most serious condition often resulting from untreated or prolonged high blood pressure. It is referred to generally as a ‘heart attack’. In ordinary language it means death of a segment of heart muscle, which follows interruption of its blood supply. When the lack of blood is prolonged as happens when there is a clot or thrombus in the coronary artery, the duration of pain is quite long. If the clot moves on or if circulation of blood from surrounding areas is adequate then the attack subsides. If however, the pain and deprivation of blood prolongs, then, a part of the heart muscle dies. Later, scar tissue is formed and the scar remains on the heart for the rest of its life. Thus heart attack occurs when the arteries carrying blood to the heart muscle are closed or blocked.
Myocardial infarction is usually confined to the left ventricle. The patient experiences sudden, severe chest pain, which may spread to the arms and throat. The main danger is that of a rapid and chaotic beating of the many individual muscle fibres of the heart, which is consequently unable to maintain effective synchronous contraction. The effected part of the heart then ceases to pump blood. It affects the artria and ventricles independently. At the stage the heart stops beating. This condition is called ventricular fibrillation which accounts for most of the fatalities.
- Angina Pectoris
It is a Latin term meaning sensation in the breast or chest which all sufferers complain of. Nowadays doctors do not like to use the term angina pectoris because it connotes sudden death. They prefer to use the term ischaemic heart disease, meaning that the heart is not receiving adequate amount of blood and oxygen.
In other words pains in the chest i.e. angina pectoris occur when one of the coronary arteries which supply blood and oxygen to the heart is blocked. There are various factors which predispose the arteries to ‘hardening’ or ‘blocking’. when such blockage occurs, the heart is starved of oxygen and blood and during strenuous exertion or emotional stress, when the heart muscle demands even more blood, a heart attack is precipated. The patient feel a constriction or a ‘squeezing’ pain in the chest which is called “angina” and it is due to lack of blood and oxygen to the heart.
- Hypertensive Heart Diseases
Disorder of the heart in which the left ventricle gets enlarged and thickened is referred as hypertensive heart disease. When the left ventricle gets enlarged the coronary arteries which supply blood to the heart are unable to cover and supply the blood to the enlarged heart. Consequently the enlarged heart does not get proper nutrients for its normal functioning. This leads failure of the left ventricle. This is often followed by the failure of the right ventricle. This failure of the both left and right ventricle is called by ventricular failure of congestive failure.
In this, the blood supply to the left ventricle is substantially choked off or reduced. This is called acute failure of the left ventricle or cardiac asthma. The hypertensive patient gets up usually in the night gasping for air. He opens the window to get fresh air. Blood pressure is high. Breathing is difficult, there is superadded bronchial spasm. The bases of the lungs get wet and he coughs bringing out white and later foul smelling cough. If the condition worsens the patient’s lungs get wetter and he virtually drowns in his own secretions and dies.
The treatment is prompt surgical opening of vein in order to remove blood i.e., venesectism. A 15mg injection of morphine sulphate is given subcutaneously and injection of 0.5 mg of aminophylline into the muscles.