08 Respiration and Circulation - part 15 - Blood pressure (B. P.)

 


08 Respiration and Circulation - part 15 - Blood pressure (B. P.)


Blood pressure (B. P.):
  • The pressure exerted by blood on the wall of the blood vessels is called blood pressure.
  • Measured by the sphygmomanometer. 
  • Usually measured from the arteries.
Arterial Blood Pressure:
  • Pressure exerted by blood on the wall of artery is arterial blood pressure. 
  • Pressure on arterial wall during ventricular contraction (systole) is systolic pressure (SP). 
  • For a normal healthy adult the average value is 120 mmHg.
  • Pressure on arterial wall during relaxation of ventricles is diastolic pressure (DP). 
  • For a normal healthy adult it is 80 mmHg. B P = SP / DP = 120/80 mmHg
  • Blood pressure is normally written as 120/80 mmHg. 
  • Difference between systolic and diastolic pressure is called pulse pressure.Normally, it is      40 mmHg.
  • Deviations from normal blood pressure value indicate malfunctioning of heart. 
  • It may be due to -  
  1. High or low blood volume, arterial inelasticity or hardening of arteries (arteriosclerosis), 
  2. Deposition of fats like cholesterol in the arteries (atherosclerosis),
  3. Renal diseases 
  4. Emotion induced hormonal changes
  5. Obesity, etc. 
  • Blood pressure lower than normal i.e. below 90/60 mmHg is called hypotension and blood pressure higher than normal i.e. above 140/90 mmHg is hypertension.
  • Various factors that affect the blood pressure are  - 
  1. cardiac output, peripheral resistance, 
  2. blood volume, length and diameter of blood vessels, 
  3. viscosity of blood, age, gender, 
  4. venous return, sleep, emotions, exercise, anxiety, etc.
  • Normal cardiac output is 5 lit/min.
  • Increase in cardiac output increases systolic pressure. 
  • Peripheral resistance depends upon the diameter of blood vessels. 
  • Decrease in diameter of arterioles and capillaries under the effect of vasoconstrictors like vasopressin or ADH cause increase in peripheral resistance and thereby increase in blood pressure. 
  • Blood loss in accidents decreases blood volume and thus the blood pressure. 
  • Blood pressure is directly proportional to Viscosity of blood.
  • Blood pressure increases with age due to increase in inelasticity of blood vessels. 
  • Amount of blood brought to the heart via the veins per unit time is called the venous return and it is directly proportional to blood pressure. 
  • Blood pressure is also directly proportional to the total length of the blood vessel. 
  • Blood pressure can also be affected by vaso constriction or vaso dilation. 
  • Females have slightly lower BP than males her age before menopause. 
  • However, the risk of high B. P. increases in the females after menopause sets in.
Measurement of blood pressure:

  • Blood pressure is measured with the help of an instrument called sphygmomanometer.
  • This instrument consists of inflatable rubber bag cuff covered by a cotton cloth. 
  • It is connected with the help of tubes to a mercury manometer on one side and a rubber bulb on the other side. 
  • During measurement, the person is asked to lie in a sleeping position. 
  • The instrument is placed at the level of heart and the cuff is tightly wrapped around upper arm. 
  • The cuff is inflated till the brachial artery is blocked due to external pressure. 
  • Then pressure in the cuff is slowly lowered till the first pulsatile sound is heard.
  • At this moment, pressure indicated in manometer is systolic pressure. 
  • Sounds heard during measurement of blood pressure are called as Korotkoff sounds. 
  • Pressure in the cuff is further lowered till any pulsatile sound cannot be heard due to smooth blood flow. 
  • At this moment, pressure indicated in manometer is diastolic pressure. 
  • An optimal blood presure (normal) level reads 120/80 mmHg.
Hypertension :
  • Persistently raised blood pressure higher than the normal is called hypertension. 
  • 140/90 mmHg is called as threshold of hypertension and the 180/120 mmHg and higher readings are dangerous to the health. 
  • It may damage the heart, brain and kidneys.
  • Under the condition of hypertension,heart uses more energy for pumping which causes angina pectoris- the chest pains due to lowered blood supply to cardiac muscles and may lead to myocardial infarction. 
  • Thereare more chances of brain hemorrhage due to hypertension as arteries in brain are less protected by surrounding tissues as compared to other organs. 
  • In kidney, hypertension may cause kidney failure.
Coronary Artery Disease (CAD) :- 
  • It is also known as atherosclerosis. 
  • In this, calcium, fat cholesterol and fibrous tissues gets deposited in blood vessels suppling blood to the heart muscles making the lumen narrow.
Angina Pectoris :
  • It is the pain in the chest resulting from a reduction in the blood supply to the cardiac muscles because of atherosclerosis or arteriosclerosis. 
  • It is charactarized by severe pain and heaviness in the chest. 
  • The pain may spread to the neck, lower jaw, left arm and left shoulder. 
  • The pain usually results from exertion, when there is more demand of oxygen by the heart, but the supply does not meet the requirement.
Angiography :
  • X-ray imaging of the cardiac blood vessels to locate the position of blockagess called angiography. 
  • Depending upon the degree of blockage, remedial procedures like angioplasty or by-pass surgery are performed.
  • In angioplasty, a stent is inserted at the site of blockage to restore the blood supply. 
  • In by-pass surgery, the atherosclerotic region is by-passed with part of vein or artery taken from any other suitable part of the body, like hands or legs.
Heart Transplant :
  • Replacement of severely damaged heart by normal heart from brain-dead or recently dead donor is called heart transplant. 
  • Heart transplant is necessary in case of patients with end-stage heart failure and severe coronary arterial disease.
Silent Heart Attack :
  • Silent heart attack, also known as silent myocardial infarction is a type of heart attack that lacks the general symptoms of -  
  1. Classic heart attack like extreme chest pain
  2. Hypertension
  3. Shortness of breath, 
  4. Sweating and 
  5. Dizziness.
  • Symptoms of silent heart attack are so mild that a person often confuses it for regular discomfort and thereby ignores it. 
  • It has been studied that men are more affected by silent heart attack than women.
know the scientists :
Akash manoj :
  • A teenager from chennai invented the non-invasive technique to predict the possibility of a silent heart attack.
  • Interestingly, he invented this technique when he was in class-X.
  • For his innovation, he had been invited to the Rashtrapati Bhavan as a guest of the President of India under the Innovation Scholars In-Residence Programme.
  • His innovative kit analyses the level of FABP3 (Fatty Acid Binding Protein-3) with the help of UV light. 
  • It is the smallest protein in the blood.

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