BLOOD PRESSURE
- Is the result of the sum of
(i) Osmotic colloidal pressure of blood
(ii) Elastic recoil of blood vessel's wall.
(iii) Pumping force of heart.
- First measured by British physiologist Stephan Hales (1733) in carotid artery of mare (female horse).
- In human it was first measured by Vaivre (1856) using Ludwig mercury manometer.
- Riva Rocci (1896) discovered sphygmomanometer, the instrument to measure B.P. 120
- Normal range of B.P. is 80 mm Hg., (120 mm Hg = systolic pressure; 80 mmHg = diastolic pressure)
- The differences between systolic and diastolic pressure is called pulse pressure (40 mmHg) 80 mmHg + age in years
- It is is calculated as : B.P. = 50 mmHg + age in years
- But, in any age it shouldn't exceed 150/100 mmHg and shouldn't be below 80/50 mmHg.
- The abnormal rise in B.P. (hypertension) occurs due to defect of any of the above three components with increasing age the rigidity of arterial wall causes high B.P.
- Hypotension (low B.P.) may be due to chronic vasodilation, anemia, blood loss and improper heart action.
- B.P. is slightly lower in female than male until the menopause.
- During sleep the pressure falls by 20-30 mmHg and may reach 180-200 during exercise.