Blood pressure is a pressure which blood has on the blood vessel wall or, in other words, the excess liquid pressure in the circulatory system over atmospheric. It is one of the vital signs and biomarkers. With each heart beat blood pressure fluctuates between the smallest (diastolic from the Latin diastole - depression) and the highest (systolic from the Latin sustole - contraction).
Blood pressure is one of the most important parameters that characterize the work of the circulatory system. Blood pressure is determined by the volume of blood pumped by the heart per unit of time and vascular resistance. As blood moves under the influence of a pressure gradient in the vessels produced by the heart, the highest blood pressure is the output of blood from the heart (left ventricle), a somewhat lower pressure is in the arteries, lower in the capillaries, and the lowest in the veins and the inlet heart (right atrial). The outlet pressure of the heart, in the aorta and large arteries differ slightly (5-10 mm Hg) because of the large diameter of these vessels hydrodynamic resistance is small. Similarly pressure in the major veins and in the right atrium is slightly different. The highest blood pressure drop occurs in small vessels: arterioles, capillaries and venules.
Variation in blood pressure in normal and pathological conditions
Persistent elevation of blood pressure above 140/90 mm Hg (hypertension) or persistent lowering blood pressure below 90/50 (hypotension) can be symptoms of various diseases (in the simplest case of hypertension and hypotension, accordingly).
Physiological blood pressure depending on the age determined by the formula for the healthy people aged from 17 to 79 years, as follows:
systolic blood pressure = 109 + (0,5 × age) + (0,1 × weight);
diastolic blood pressure = 63 + (0,1 × age) + (0,15 × weight).
The data in the past were characterized as "the ideal pressure" in view of "normal" load age-related diseases. But according to modern concepts in all age groups over 17 years ideal pressure is below 120/80 (optimal).
For teens of 14-16 years with normal physical development the upper limit of normal should be considered as systolic pressure of 129 mm Hg, diastolic of 69 mm Hg.
For people over age 50, systolic blood pressure above 140 mm Hg is an important factor of risk of cardiovascular disease.
People with systolic blood pressure 120-139 mm Hg or diastolic blood pressure of 80-89 mm Hg should be treated as people with "prehypertension."
Since blood pressure 115/75 mm Hg with an increase in blood pressure every 20/10 mm Hg risk of cardiovascular disease increases.
For the prevention of cardiovascular disease they need to have a lifestyle change, improving health status. Previously it was thought that the most dangerous in terms of cardiovascular events increase in diastolic blood pressure, but it turned out that this risk is associated with renal disease, and isolated systolic hypertension was often considered as a variant of the norm, "the ideal pressure." Now these view have refused.