Edmund Oswald, age 13, of Nashville, Tenn., for his question:
WHAT IS HIGH BLOOD PRESSURE?
Blood pressure that is normal for one person may well be higher or lower than another person's normal pressure. And the same person may vary in blood pressure from day to day or even from hour to hour. So you can't say that high blood pressure is just any pressure above a so called norm.
Doctors call high blood pressure "essential hypertension" when its cause is unknown.
Many factors, however, can make a person's blood pressure rise. It is affected by the health of the body's organs and tissues, particularly the heart, arteries, kidneys and the ductless glands such as the adrenal gland. Blood pressure also is affected by the contractive pumping action of the heart's left ventricle, the volume of blood thrust into the aorta by the heart, the condition of the blood (including thickness or viscosity) and the resistance of the arteries to the volume of blood delivered to them.
Blood pressure readings include two numbers, one "over" the other, as in 120/80. The first number refers to systolic pressure, the second to diastolic pressure. Systolic pressure is the force with which the heart pumps blood during contraction. Diastolic pressure is the force with which blood is pumped during heart relaxation.
Normal systolic blood pressure for adults is about 120 millimeters. Pressures over 150 are considered high by medical authorities.
Doctors also say that diastolic pressure over 90 millimeters is high.
Blood pressure usually rises with age because the arteries become less elastic and slow the flow of blood. High blood pressure can cause heart failure, strokes or kidney failure.
Treatment diet control, although sometimes medications are prescribed.
Low blood pressure is called hypotension. It rarely indicates serious disease and generally requires no special medical attention.
Sometimes hypotension can be caused by some disease. It can be a symptom of tuberculosis, some types of cancer, rheumatism and conditions lowering the secretions of the adrenal glands.
Doctors use an instrument called a sphygmomanometer to measure blood pressure. The instrument includes a glass tube with mercury, a cuff or wide rubber band that can be filled with air and hollow rubber ball which pumps air into the cuff.
Blood pressure is the pressure that blood exerts against the walls of the arteries. The amount of pressure depends upon the strength and rate of the heart's contraction, the elasticity of the arteries and the volume of the blood in the circulatory system.