Blood Pressure

Meaning and Definitions

Blood pressure is the pressure exerted by the circulating blood against the inner arterial walls. As a result of each heartbeat, blood keeps gushing from the heart to all other body parts, and the intensity of gushing is termed as BP. Blood pressure is essential for normal blood flow through each and every cell of the body. Blood pressure is influenced by variables such as the age, general well-being,  time of the day, any stressors faced by an individual and the presence of systemic illness that is closely linked with the cardiac system. In a normal case, the blood pressure within the arterial walls is directly linked with the rate of heartbeat, the volume of blood per beat, peripheral resistance, and viscosity of the blood.


Systolic and diastolic pressure

Scientifically, blood pressure is written as a ratio between the systolic pressure and the diastolic pressure. Systolic pressure is the pressure as a result of ventricular contraction and the diastolic is the result of atrial relaxation. During the contraction ( systole), blood is ejected out of ventricles whereas the diastole will allow atrial refilling. The blood pressure of a healthy adult range from 100 to 60 to 140/90 mm of Hg, I,e the average of 120/80 mm Hg. However, if the blood pressure rise beyond 150/100 mm of Hg, it is called hypertension Similarly, if the pressure drops well-below  100/60 mm Hg, it is the hypotension. Blood pressure is essentially one of the important biological phenomenon help to maintain the internal balance within our body, however, rapid fluctuation of blood pressure is risky. The rate, rhythm, volume, quality and the nature of heartbeat vary between different age-groups,  The table below depicts how heart rate and BP vary according to the age. 


Blood Pressure and the heart rate


Normal BP

Normal heart rate (bpm)

From birth  to 11 months

90/60 mm hg

80 to 160

From 1 to 2 years

100/70 mm Hg

80 to 130

From 3 to 4 years

100/80 mm Hg

80 to 120

From 5 to 6 years

110/80 mm Hg

75 to 115

From 7 to 9 years

120/80 mm Hg

70 to 110

Over 10 years

120/80 mm Hg

60 to 100



Measuring blood pressure


A number of devices are being used to measure the blood pressure, but the most widely used equipment is the sphygmomanometer. A sphygmomanometer has a manometer indicating 0 to 300 units. The BP cuffs are used to inflate while it is applied over the upper arm. The air must be removed completely (deflated) before applying them on the forearm. For the fair reading, the patient must be in a stable position, ideally sitting on a chair by resting the arm on a table. Make sure the manometer is held exactly at the level of the chest , this will ensure the correct reading. The patient should be given enough explanation of the procedure to avoid unnecessary fear and anxiety ( anxiety might result in more BP ). On inflation of the cuffs, the patient feels pressure, the inflation must be slowly raised until the reading touches the level of  150 or more. The knob must be slowly released to deflate it. As the cuffs are released, you will hear a loud heartbeat and the first beat is recorded as the systolic pressure, the last loud beat is the diastolic pressure.



What determines the blood pressure?

Blood pressure is influenced by a number of factors such as the person`s age, lifestyle, general health status, gender, body weight, cardiac health, food habits, family history of BP. It is also important to understand that the intake of stimulants such as caffeine before measuring the BP, stress levels and emotional stability can depict in an increase in the reading.  In some individuals, it is pretty evident that the individual`s posture while recording the BP can result in the increase or decrease of values, this is especially true when a person assumes a standing posture. Such condition is known as the Postural (orthostatic) hypotension. Orthostatic hypertension occurs when the BP of a person drops significantly soon after the patient assumes the upright posture. Patients with orthostatic hypotension may experience dizziness, light headedness and syncope, and he must be consulted for further diagnosis.



Causes of increased blood pressure (hypertension)

  1. Smoking and drinking too much alcohol

  2. Being overweight or obesity with  excess of BMI (Body mass index).

  3. Systemic disorders linked with heart and blood vessles.

  4. Excessive intake of salt and  spices.

  5. Inability to cope with stress.

  6. Age beyond 50 is of moderate-risk and above 60 is a high-risk factor.

  7. Genetic tendency or familial history of hypertension.


Causes of decreased blood pressure (hypotension)

  1. Pregnancy

  2. Anaemia and weakness

  3. Heart problems

  4. Endocrine disorders

  5. Severe dehydration

  6. Chronic Blood loss

  7. Severe infections

  8. Severe allergic reaction (anaphylaxis).

  9. Poor nutrition 


Further reading


Blood vessels in human beings


Blood and circulatory system


Anatomy of human heart


  Blood groups                    



  1. What is blood pressure? Explain the mechanism of blood pressure due to blood flow.

  2. What is the difference between systolic and diastolic pressure?

  3. Why blood pressure is essential ?

  4. What is hypertension and what are the causes?




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