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When the heart relaxes blood is sucked into the heart from the veins, like air filling the balloon when you relax your hand. A series of valves makes the blood flow in one direction, so blood won't flow backwards into the heart from the arteries (like air does in the balloon example). When your heart relaxes, the pressure drops to a low point called the the diastolic (die-a-STALL-ik) pressure.

These two pressures specify your blood pressure, which is expressed as systolic "over" diastolic, like "120 over 80".

Why Hypertension is Bad
Hypertension makes you more likely to have a heart attack or stroke. That is, it's a "risk factor" for two of the top killers in America. Like water in a hose, blood puts pressure on the vessels. Excessive pressure can cause various things to fail, like blood vessels, kidneys, and other organs.

Hypertension doesn't have direct symptoms. You only know you have it if you measure your blood pressure.

Causes of Hypertension
"In about 90% of people with high blood pressure, the cause isn't known." {Merck} This type of hypertension is called "essential" or "primary" hypertension. If the cause is known, it is called "secondary" hypertension.
 
 

The study is formally called: The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7).

An "Express" version of the study has been released before the detailed version. This Express version is 52-pages long and available from http://www.nhlbi.nih.gov/guidelines/hypertension/index.htm.
 

If your doctor is quoting you information from this table, he/she is not up with the latest information. Visit the National Institutes of Health web site and print a copy of the 52-page JNC 7 "Express" report for your doctor. (Many doctors are overworked and can't keep up with EVERY new study as soon as it comes out.)
 

You Must Relax!
Regardless of the device, it's important that you be relaxed before the reading is taken. You can't leave your car in a "No Parking" zone as you run into the pharmacy to get a quick BP reading off their machine. Some sources say you should sit or lie still for five minutes before taking a reading.

Stress can temporarily raise blood pressure. The stress of just being in a doctor's office can cause "white coat hypertension", where someone with normal BP shows a temporarily high reading.

Since several factors can cause blood pressure to rise temporarily, multiple readings should be taken spread over days. Don't let one high reading give you a heart attack.

Basic Measurement Process
Your blood pressure is expressed as two numbers, a high number "over" a low number. Both numbers are pressures. Your pulse is often taken at the same time, so you may have a third number somewhere. Your pulse is simply how many times your heart beats per minute.

BP is measured by listening to blood flow through an artery. A cuff is placed around an artery and is inflated while listening to the blood. The cuff is inflated until you hear the blood stop flowing.

Systolic (high number): The cuff is now slowly relaxed until you hear blood just start to flow.That's the high (systolic) number.

Diastolic (low number): At the systolic pressure the blood flow sounds "funny" because the artery is still mostly squished. The cuff is relaxed further until the blood flow sounds normal. That's the low (diastolic) number.

A human can listen to blood flow using a stethoscope. A machine uses a small microphone in the cuff.

Machines in Stores
You can use one of those machines in the pharmacy section of some stores to get an idea of your blood pressure. Though not "doctor's office accurate", they can alert you to pressures you should ask your doctor about. If possible, try to relax a bit before taking the reading (since you were probably rushing around before stopping at the machine).

Home Monitors
Home monitors are rated in Consumer Reports June, 2003  p. 22-24
.

Automatic Arm Monitors
These were rated the highest. The cuff is automaticallly inflated and deflated, and the readings appear in a digital display. These run on batteries or an AC adapter that plugs in the wall. Prices range from $45-$85.

Manual (Semi-automatic) Arm Monitors
The cuff is controlled by a bulb you squeeze yourself while the machine listens and displays the readings. Said to be the hardest to use. Prices range from $35-$50.

Wrist Monitors
The lowest rated and most expensive. The cuff goes around your wrist instead of your arm. Prices range from $70-$125.

Fingertip Monitors
These were not tested in this report.

Two studies were done to see if blood pressure (BP) could be lowered by diet alone.

The first DASH study ignored sodium (salt). The resulting "DASH" diet lowered blood pressure by 5.5 points (systolic) over 3.0 points (diastolic) in eight weeks.

The second DASH study took the diet from the first study and looked only at the effect salt had on BP. The resulting DASH-2 diet (limiting sale intake) lowered blood pressure by 8.9 points over 4.5 points.

The latest DASH diet recommendations came out in May, 2003, and be found at the National Institutes of Health web site: The DASH Eating Plan (Updated May 2003)
(http://www.nhlbi.nih.gov/health/public/heart/hbp/dash/index.htm)

DASH Study Details
In 1997 a study was conducted to learn more about an odd observation: People who ate food rich in potassium, calcium, magnesium, protein and fiber had low blood pressure. When given supplements of those nutrients, only potassium had any effect. It appeared something in the food had an effect beyond the isolated nutrients (trace nutrients?). That is, taking supplements was less effective than eating the right foods.

But what were the right foods? The DASH study used the following diet:
 

Blood pressure fell with decreased sodium intake. The lowest sodium group (1,500 mg) lowered their blood pressure by 8.9 points (systolic) over 4.5 points (diastolic).

Put another way, subjects with Stage 1 hypertension dropped blood pressure as much or more than any anti-hypertensive drug had done.

To make your own DASH-2 Diet, take the Original DASH Diet and limit sodium to 1,500 mg per day. This can be helped greatly by limiting intake of processed food. Read the labels to see Sodium contents.

The contribution of sodium to hypertension has apparently been settled with the DASH-2 study: Sodium can increase hypertension. However you feel about that study, UC Berkeley wisely observed: "A high-sodium diet has no advantages and many disadvantages."

(Author's Aside: If you automatically salt your food before tasting it, stop it! Not only does it piss off the chef who so carefully seasoned it already, it shows you aren't thinking but running on habit - an unhealthy habit at that.)

Caffeine
Caffeine can raise blood pressure, but this appears to be a temporary rise. Caffeine is not known to cause hypertension. {UCB}
 

Age
As people get older, the arteries tend to be less flexible (from build-up of plaque). The reduced flexibility can increase blood pressure. (So stop eating foods that add plaque to your arteries!)

Smoking
Of course smoking increases blood pressure. Even one cigarette can raise your blood pressure. There is NOthing physically beneficial about smoking. In your heart, literally, you know it's bad. Stop it.

The cuff is inflated until the artery is squeezed closed (hear the blood stop flowing). The cuff is slowly deflated while listening for blood flow to resume. When you first hear flow start, that's the systolic pressure.

Although blood is flowing, it sounds turbulent (noisy). Cuff pressure is slowly reduced until the flow sounds smooth. This is the diastolic pressure.

The units of measurements are millimeters (abbreviated "mm") of mercury (symbol "Hg").

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