Blood Pressure Information

What is Blood Pressure?

Blood pressure is the force created by the heart as it pushes blood into the arteries and the circulatory system. When the heart pumps, it causes blood to flow through the arteries and into the arterioles.  As the blood goes through the arterioles, the arterioles either contract or expand altering both the amount of blood flow and the resistance to blood flow. If the arterioles remain in a contracted form, they create high blood pressure.  The heart must then pump harder because the arterioles are exerting a greater resistance to blood flow.  

High blood pressure is often called the "silent killer". It is called this because there are usually no symptoms. Very high blood pressure can also cause arteries to bulge (aneurysm) or burst (hemorrhage).

Blood Pressure and Heart Disease

High blood pressure is a risk for both heart disease and stroke.  Unfortunately, high blood pressure usually has no specific symptoms and no early warning signs. It directly increases the risk of heart disease.  High blood pressure is a risk for heart disease because the heart is working harder than normal thus putting the heart and the arteries under a greater strain.  When the heart is forced to work harder for long periods of time, the heart becomes enlarged.  A heart that is slightly enlarged may function okay but a severely enlarged heart has a hard time pumping a sufficient amount of blood.  Given this, blood pressure is also a risk for strokes.  

It is estimated that over 60 million Americans have high blood pressure.  Of this 60 million, about 35 percent don't know they have it.

Blood pressure and Kidney disease

High blood pressure and kidney disease are closely related. High blood pressure is a common cause of kidney failure in Australia. One mechanism for this is the production of a hormone called 'renin' by the kidneys. If the kidneys aren't functioning properly, renin can be produced inappropriately, raising the blood pressure.

If high blood pressure is left unchecked, it can cause blood vessels in the kidneys to become thickened and narrowed, possibly leading to reduced blood supply and reduced kidney function. For more information about kidneys, click here.

Blood Pressure as a Tool

Blood pressure is an important diagnostic index, especially of circulatory function. It is an important diagnostic index for many reasons.  Firstly, any condition that dilates or contracts the blood vessels or affects their elasticity, affects the blood pressure.  Secondly, any disease of the heart that interferes with its pumping power, affects the blood pressure. In a healthy animal, the blood pressure normal for its species is maintained within a certain range with great constancy.  Thus if blood pressure is abnormally low or high, it usually indicates that greater health problems are present.  

How is it Measured?

Blood pressure is measured at two point, a high point and a low point.  The high point is the point at which the heart contracts to empty its blood into the circulation, called systole.  The low point is the point at which the heart relaxes to fill with blood returned by the circulation, called diastole. Pressure is measured in millimeters (mm) of mercury by an instrument called a sphygmomanometer.

In humans, blood pressure doesn't vary greatly.  In healthy persons, blood pressure increases from about 80/45 in infants, to about 120/80 at age 30, to about 140/85 at age 40 and over.  Blood pressure increases with age because the arteries loose elasticity.  

Abnormally high blood pressure (hypertension) is considered a contributory cause of arteriosclerosis. Abnormally low blood pressure (hypotension) is observed in infectious and wasting diseases, hemorrhage, and persons who have collapsed. 

Causes of High Blood Pressure?

In about 10 percent of patients, the disease can be traced to specific causes: heredity, kidney abnormalities, adrenal gland tumors, diabetes, chronic kidney disease, hormone abnormalities, use of birth control pills, pregnancy or a congenital narrowing of the aorta. This is called secondary hypertension. In the other 90 percent of patients, the cause is unknown and is referred to essential hypertension.  

Does Blood Pressure stay the same?

No. Your blood pressure varies all the time to meet your body's needs. The pressure will be different when you get up in the morning, to when you are relaxing, exercising or sleeping. Blood pressure is usually at its highest when we exercise, and lowest when we sleep. It can also rise due to anxiety, excitement, activity or nervousness. In general, blood pressure remains fairly constant throughout the day.

How to Decrease Blood Pressure

There are many ways to decrease blood pressure.  Blood pressure can be decreased if a person exercises, doesn't smoke, limits salt intake, limits alcohol intake and if obese, looses weight.  Individuals who are very active have a lower risk of getting high blood pressure (20 to 50 percent) than people who are not active. 

Medications for Blood pressure

Please note: Medications for blood pressure should be prescribed by and taken under the direction of a doctor.  

Diuretics: Commonly called "water pills," they lower blood pressure by reducing the body's sodium and water volume

Vasodilators: These drugs relax the muscles in the blood vessel walls, causing them to dilate, or widen

How is it controlled?

Blood pressure is regulated largely by the nervous system.  Hemoglobin, the iron-protein compound that gives blood its red color, also plays a role in regulating blood pressure.  However, hemoblobin's affect is usually localized and is not very useful when trying to control blood pressure on a large scale.  Hemoglobin contains nitric oxide, a gas that relaxes the blood vessel walls, thus increasing blood flow.  It controls the expansion and contraction of blood vessels, and thus blood pressure, by regulating the amount of nitric oxide to which the vessels are exposed.

Individuals with high blood pressure can be given medication to lower their blood pressure. Mild cases of blood pressure can be treated through behavior modification like changing diet and increasing exercise. More severe cases of hypertension require medications like diuretics and beta blockers. Diuretics rid the body of excess fluids and salt. Beta blockers reduce the heart rate and the heart's output of blood.

Blood Pressure in the News

May is National High Blood pressure Month in the United States

Blood Pressure Statistics

• As many as 50 million Americans aged 6 and older have high blood pressure.
• One in five Americans (and one in four adults) has high blood pressure.
• Of those people with high blood pressure, 31.6 percent don't know they have it.
• People with lower educational and income levels also tend to have higher levels of blood pressure.
• Non-Hispanic blacks and Mexican Americans are more likely to suffer from high blood pressure than are non-Hispanic whites.

Who is at risk?

In the early and middle adult years, men have high blood pressure more often than women. But as men and women age, the reverse is true.  Unfortunately, more than half of all Americans over age 65 have high blood pressure.