Blood pressure means the lateral pressure of the circulating blood on the vessel wall of the arterial blood channels. The blood pressure essentially depends on two factors—
(i) force of contraction of the heart and
(ii) the resistance in the peripheral blood vessels.
The average normal blood pressure in an adult is Systolic/ Diastolic 120/80 m.m. of Hg. (Mercury).
But the blood pressure varies from person to person (and in different physical or mental conditions). The range of normal blood pressure is as follows :
Systolic upper limit being 140 and the lower limit 100 mm. of Hg. Diastolic upper limit 90 and the lower limit 60 mm. of mg. For a particular person the B.P. should be steady, within the normal range and there should be no symptoms.
(Conventionally, more importance is attached to the level of the Diastolic pressure. But at present Systolic pressure is considered not less important than the Diastolic pressure from the points of clinical assessment and prognosis. Currently, the recommended safe upper limits for the people suffering from hypertension is 140/85 mm. of mg. and that for the diabetic person is 135/80 mm. Hg. Moreover, it is also stressed that the elderly people (between 60 and 80 years) should be put on appropriate anti-hypertensive drugs [e.g., ‘Thiazide diuretic’ or ‘Beta-blocker’) if the Systolic B.P. is found to be above 160.]