Normal Blood Pressure

Normal blood pressure is not fixed but rather a continuously dynamic entity subject to many influencing factors both inside and outside the body. It constantly changes to suit the flow requirements of the various parts of the circulation and the circulation as a whole. Normal blood pressure also varies from person to person just as height does.

So how can you know what is normal for you? By taking lots of readings and consultation with your doctor. I do mean taking it yourself! You can learn and it's easy. See How to Take Blood Pressure

It also varies across the day being highest in the morning and lower towards evening and this is called the "diurnal variation." Some decrease should occur during sleep.

Other Factors That Influence Normal Blood Pressure:

    • Exercise/physical exertion
    • Smoking
    • Overweight
    • Diet
    • Stress/anxiety
    • Disease States
    • Substances:
      • Decongestants (some)
      • Alcohol to excess
      • Non-steroidal anti-inflammatory medication, i.e. ibuprofen
      • Cox-2 inhibitors, i.e. Vioxx, Celebrex, Bextra
      • Cocaine and amphetamine
      • Some adrenal steroids
      • Estrogen and testosterone (both sex hormones)

All of these are commonly encountered except the illicit drugs and abnormal adrenal steroids. Usually these factors effect the normal blood pressure temporarily, mostly raising it, and the effect usually dissipates when the factor is removed.

However, removal of some of these factors is quite difficult when you consider smoking (nicotine addiction), alcohol to excess (another addiction), obesity (another addiction?), stress/anxiety and disease states.

On the other hand these factors represent fertile ground for restoring your pressure to desirable in a very healthy manner--life-style changes rather than drugs.

Regulation of Normal Blood Pressure:

Blood pressure is regulated in a narrow range but is increased in response to demands and indeed to whatever pressure is necessary to insure adequate circulation to all parts of the body especially the brain.

Regulation of blood pressure occurs by four mechanisms:

1. Changing the heart rate or the force of the beat (or both) will change the blood pressure.

2. Expanding or contracting the size of the small veins causes a decrease or increase respectively in the pressure.

3. Expanding or contracting the size of the small arteries causes a decrease or increase respectively in the pressure.

4. Decreasing or increasing the amount of fluid (blood) in the blood vessels by the kidneys will decrease or increase pressure respectively.

The first three mechanisms cause a rapid response while the fourth responds rather slowly. Unfortunately in some people these mechanisms go awry for unknown reason and their blood pressure develops a sustained elevation called high blood pressure or hypertension.

Normal Blood Pressure Readings:

Now let's take up just what is a normal blood pressure in terms of the reading. Normal means what you find in 95% of the population but that is not necessarily the most desirable level. Lets change the term, normal, to a better term, desirable. A desirable blood pressure is one that delivers completely adequate circulation but which is not associated with any increased adverse events such as heart attacks, strokes, heart failure and kidney failure.

That level happens to be about 115 over 75. Good studies have shown that as a person's average blood pressure goes above that level one starts to observe a small increase in adverse events and the higher it goes the worse it gets.

Rule of thumb: For every 20 mm systolic increase and every 10 mm diastolic increase the risk doubles!

The range from 115 over 75 to 139 over 89 probably does not carry enough increased risk of adverse events to make it worth the risk of treating it with drugs.

However, it does represent a great opportunity to make oneself healthier by instituting life-style changes, which obviously carry no risk, such as smoking cessation, exercise, weight loss, salt restriction and alcohol restriction.

At 140 over 90 and above, the risk of adverse events is high enough to justify pharmaceutical and other means to bring the blood pressure to a more desirable level.

Blood Pressure Classification
Systolic Diastolic Class
115 75 Desirable
120-139 80-89 Prehypertension
140-159 90-99 Hypertension Stage 1
160 or over 100 or over Hypertension Stage 2

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