One Nation Under Pressure

Each time the heart beats, it sends a blood pressure pulse down the arm. The force of this pulse generates the systolic blood pressure. The systolic measurement is the "top number" of the blood pressure reading. After each heart beat, the heart rests for a fraction of a second. The pressure in the blood vessel during this resting phase drops, and is called the "diastolic pressure." It is measured by the "bottom number" of the blood pressure reading.

Blood pressure is relatively simple to determine. You can measure it yourself with a device called a sphygmomanometer ("sphyg" for short, pronounced "sfig"). The sphyg is made up of a heavy duty balloon or air chamber that lies inside a band of cloth called the "cuff." The cuff is wrapped around the upper arm and the balloon is filled with air. The increasing pressure in the balloon compresses the artery until blood flow to the lower arm is completely shut off. You then gradually decrease the cuff pressure. During this time you are listening over the artery with a stethoscope and watching a scale that records the amount of pressure in the balloon. As you decrease the cuff pressure to the systolic pressure level, you will begin to hear the pulsing sound of the heart beat. This indicates the return of blood flow in the artery. The number on the measurement gauge at that instant is recorded as the systolic blood pressure. As you continue to slowly reduce the pressure in the cuff, the pulsing sound continues until it suddenly cannot be heard. The pressure at which these sounds disappear is recorded as the diastolic pressure.

Arteries are muscular organs that can both contract and expand. Excessive contraction or stiffening of the artery walls raises blood pressure. Hormones can also raise blood pressure. Some organs such as the kidneys and adrenal glands are especially important to the hormonal regulation of our pressure. However, the major cause of high blood pressure is a less than optimal lifestyle. Most people have some tendency to high blood pressure; whether they develop the problem and how soon they do, is largely a function of their everyday decisions.

Blood pressure is measured in millimeters (mm) of mercury. This dates back to the days when all sphygmomanometers used a column of mercury to record the pressure. The medical world today divides blood pressure readings into four levels of risk as shown in figure.

Notice that the safest blood pressure range is characterized by an average systolic pressure of 120 mm of mercury or lower, and an average diastolic pressure of 80 mm or lower, at rest. Every person should strive to get his or her resting blood pressure into this "120/80 mm or less" range. Higher pressures carry increased risks of disease and premature death. However, the most careful research suggests that lowering the diastolic blood pressure below 80 further lowers one´s risk of heart attack and stroke. In fact, there is no threshold at which further lowering of diastolic blood pressure (DBP) does not give further lowering of risk of both heart disease and stroke. For example, a DBP of 70 is better than 80. A diastolic reading of 60 is better still.

Control of blood pressure begins with knowing what your blood pressure is. Do not assume that just because you feel fine you are free of a blood pressure problem. High blood pressure is indeed called "the silent killer." It has this name because serious disability or death is often the very first symptom of hypertension. Many people will never realize that their blood pressure is high unless they get it checked by a doctor, go to a screening program, or get a blood pressure instrument and check it themselves. In fact, it is common for people to feel fine with blood pressures of 200/100 or even higher. Indeed, you may feel great while being unwittingly on the verge of a disaster such as a sudden stroke or heart attack, or gradual kidney damage with resulting renal failure down the road.

The National Institute of Health sponsored a study that demonstrated the power of lifestyle changes to lower blood pressure. Over 900 subjects (men and women, black and white) with mild hypertension were enrolled in a lifestyle change program. Specifically, program participants initially had diastolic blood pressures in the 85-99 range (average 90.5). Systolic blood pressures averaged 140.4.26 Some of the subjects were put on a lifestyle change regimen, while the remaining ones were treated with a single blood pressure medication. The reductions in blood pressure for the group treated with lifestyle change alone are shown in figure.

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- Proof Positive by Neil Nedley