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The most comprehensive academic health center in Texas, The University of Texas Health Science Center at Houston (UTHealth) is home to six schools devoted to medicine, nursing, public health, dentistry, health informatics and graduate studies in biomedical science. UTHealth, founded in 1972, is part of The University of Texas System. It is a state-supported health institution whose state funding is supplemented by competitive research grants, patient fees and private philanthropy.

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Blood Pressure 101STORY BY

Karen Krakower Kaplan
with S. Ward Casscells, MD

 

Blood Pressure 101

High blood pressure. Such common words for Americans. So common that 60 million of us have it, ignore it, lie about it, or don’t know it.

In fact, if you ask any of us how we’re feeling, we’ll say just swell, thank you. Which is weird for three such alarming words: High. Blood. Pressure.

Its other moniker is even more bell-ringing: hypertension. And that’s the perfect name for it: something inside of us is, well, really tense.

And, 120 over 80? Bupkus. Our health providers are not impressed. (As if we even know what 120 over 80 means.)

So let’s find out

  1. what those numbers mean
  2. where they get those numbers
  3. (and why ’sphygmomanometer’ is never uttered out loud.)

Blood Pressure: 101

Blood pressure is cool. It’s something you want. In fact, It’s a necessary thing. If our bodies had no blood pressure, we couldn’t stand up. We would just ooze around; gravity would have the better of us.

Measuring pressure of any kind—from pleasing your boss, remembering your anniversary, to putting air in your tires—is expressed through this S.A.T. equation: Pressure equals Force divided by the Unit Area.

So, blood pressure is the amount of force that is exerted by our blood against the artery walls as it’s being pumped through the body.

Each time your heart beats, it is pumping out about 2-3 ounces of blood into the major arteries—our personal garden hoses—that lead to our organs. Between beats, the heart, essentially a pump, refills with blood. That blood will then be pumped out and moved along with the next beat.

When the arteries are smooth and clear—with no plaque or narrowed places, no barriers or speed bumps—the blood will flow freely. It will have plenty of room. The pressure of the blood against the arterial walls will be "normal."

Measuring blood pressure

The two numbers involved in a blood pressure reading represent the two stages of the pumping system: the pushing out of blood (systole) and the refilling of the heart (diastole.) In other words, it is when the heart is working (systole) and then resting (diastole); pumping out blood (systole) and then refilling (diastole).

The systole is the upper and higher number; the diastole is the lower and smaller number.

A reading of 110mmHg over 70mmHg means that your beating pressure and highest arterial pressure is 110 and your between-beat pressure and lowest arterial pressure is that of 70. (The actual numbers have to do with mercury units in the blood pressure monitor—millimeters of mercury—not the number of heart beats you’re recording or the number of blood cells coursing by, or the moons your astrological sign bears.)

The brachial artery in the arm happens to be a good and convenient representative artery with which to measure pressure.

And this is where that word comes in: the mysterious contraption that grips your arm is called a sphygmomanometer. The act of recording blood pressure is not nearly as complicated as the word. Here’s how it works:

  1. Extend your arm and keep it level to your heart. (Some health care professionals place the arm out straight; some bend the arm at the elbow.)
  2. The cuff is wrapped snugly around your upper arm, about an inch above your elbow while a stethoscope searches out the pulse of the brachial artery.
  3. The person taking your pressure will close a valve on the bottom of a bulb that, when squeezed rapidly, inflates the cuff. The cuff around the arm tightens until a dial or column of mercury reads about 30mmHg (millimeters of mercury) higher than your usual systolic pressure. If the doctor doesn’t know your usual systolic pressure, the cuff is inflated a little above 200 mmHg. It is at this point that no pulse sound is heard through the stethoscope.
  4. Here’s the fun part: now the doctor opens the valve slightly, letting the pressure fall slowly. As the pressure falls, the number on the mercury dial or column that corresponds to the very first pulse heard through the stethoscope is your systolic (top) pressure.
  5. Air continues to escape through the valve, and the moment pulse sounds disappear again you have your diastolic (bottom) pressure.

What’s normal these days?

In the old days, 140/90 was considered the upper limits of normal.
That kind of ’normal’ doesn’t live here anymore. Blood pressure reclassifications from the National Heart, Lung, Blood Institute are as follows:

But it’s only high in the doctor’s office

Your blood pressure changes every, single minute. A cough, a sneeze, a thought, a stomp on your brakes during traffic raises your pressure so that your body has enough umph to respond to the stimulus.

You want your pressure “to rise to the occasion.” Otherwise you wouldn’t be able to stomp on the brakes, make it up the stairs, make love!

But you don’t want it to rise for no occasion at all.

The best way to calculate it is to get an official reading at your doctor’s office.

Sure, you say, but that white coat is what raises your blood pressure. Your physician is accustomed to this warm greeting and will take this into account by doing repeat readings several minutes apart. In the past few years, cardiologists and neurologists have realized that a "normal" blood pressure of 120/80 in the office means 100/70 in the more relaxed environment of the home.

Once you have an official baseline reading, your doctor will make any necessary recommendations. This may include medication, dietary changes and exercise regimens.

It may also mean a watch-and-see: monitoring your own blood pressure for several weeks at various times of the day in order to obtain an accurate record of your blood pressure.

The damage done

When blood pressure rises and remains high, the increased force on vessel walls can damage those vessels as well as the heart, kidneys, eyes and brain. Enter the garden hose metaphor: ever tried to water your lawn while you’re standing on the hose? Have you ever seen your hose split down the seams and rupture?

Hypertension is the basis of most strokes, both directly and indirectly. It is a risk factor for heart attacks and a cause of cardiovascular death and also a common cause of renal failure.

Hypertension affects the kidney because the kidney has to regulate its blood flow very precisely, like the brain does. Increased blood pressure induces changes in the kidney's regulation of blood flow. Eventually damage to the small vessels in the kidneys disrupts blood flow and injures the entire organ. People with diabetes can suffer the double-whammy: sugar causes negative changes in the filtering process of the kidneys.

There are three types of hypertension:

Men seem to develop hypertension earlier than women, though women aren’t far behind these days. After menopause, women catch up. About 1 in 5 adults in the U.S. has high blood pressure. African Americans develop hypertension almost twice as often as Caucasians. Essential hypertension makes up 90 percent of the cases in persons over 45.

Self-monitoring, self-help

Take control of your health: get several blood pressure readings over a 3-6 month period. If the numbers do not go down, make an appointment with your health care provider.

For those who want to check their own pressure at home with a monitor, remember, the numbers can be reliable, but be sure to bring the monitor into the doctor's office and ask the staff to check it against their monitor. If the two agree, home monitoring is a good way to go.

If you are relying on monitors stationed in drugstores, malls, grocery stores, remember two things:

Also, remember that the monitor—especially the digital variety—is very sensitive. Stay completely still while you are checking your pressure. If you move, sneeze, laugh, talk, it will register higher.

Hypertension is a complicated condition which anyone can have, even the very calm, the very active and the very thin.

Other factors associated with hypertension are:

If you have hypertension, be sure to have your blood pressure checked regularly (your doctor will tell you how often), stop smoking; avoid excessive salt intake (no more than 2400 mg a day, about a teaspoon’s worth); eat more fruits and vegetables as well as foods high in fiber; reduce stress on and off the job through yoga, meditation, lifestyle changes; drink moderately (no more than one drink per day for women, two for men); exercise regularly (bare minimum, 30 minutes per day of moderately strenuous activity); and keep weight within normal limits. (Ah, yes, so easy to do...)

Hypertension is a controllable condition, in many cases, with simply lifestyle changes and simple, inexpensive medications. Just knowing the basics of your body’s mechanics puts you in better control of your health.

Now it’s time to do something about it.

Oh yes, as promised: why is sphygmomanometer never uttered out loud? Because no one, including your doctor, can pronounce it.

For more information on maintaining healthy blood pressure, go to:
The National Heart, Lung, Blood Institute
The American Heart Association
The American Stroke Association

Last Updated Last Updated: 2-24-2010

 

The most comprehensive academic health center in Texas, The University of Texas Health Science Center at Houston (UTHealth) is home to six schools devoted to medicine, nursing, public health, dentistry, health informatics and graduate studies in biomedical science. UTHealth, founded in 1972, is part of The University of Texas System. It is a state-supported health institution whose state funding is supplemented by competitive research grants, patient fees and private philanthropy.