Blood Pressure: What controls blood pressure, and should we be attempting to change it?

blood-pressureCommon medical wisdom will go after any blood pressure over 120/80. This may not be the best thing to do.

Actually, this is currently somewhat up in the air. Some studies say throw enough pills at it to bring it down to 120/80 and others say leave it alone if it is 150 or lower. But control has possible severe consequences.

The best treatment, as we all well know, is proper diet, proper exercise, adequate sleep, and quality “down” time. Of course, most doctors believe many won’t do this, and they are right about that.

When and if blood pressure should be treated is a different topic altogether, and one of great confusion.

What is the reason for high blood pressure?

Believe it or not, this is not fully understood, which, given the medical obsession with blood pressure, is quite an amazing thing. Many things influence blood pressure and blood pressure can be altered by medically meddling with them. This is frequently done with no consideration as to why a particular patient might need his blood pressure at, say, 145/90.

Blood pressure is regulated

The body, no matter what its condition, is capable of producing any blood pressure it wants, from lethally low (shock) to lethally high (organ damage, stroke). Clearly if it’s producing a potentially fatal pressure, low or high, emergency measures are necessary. But suppose someone has a blood pressure of 155/90. What then? Does the doctor know best or does the body know best?

If blood pressure is regulated (which it obviously is) what is doing the regulation? The main player here is the good ol’ hypothalamus. It regulates almost everything that circulates, so why not. It has control over several hormones and chemicals that can alter it.

The kidneys and brain are major blood hogs. The kidneys need adequate blood flow at adequate pressure to work properly. They have a neural hotline to the hypothalamus for just this reason.

(Snipping or disabling this nerve is a current treatment for hypertension. We find this completely appalling, and, no doubt, so do the kidneys.)

The brain (well the hypothalamus is a brain, thank you, but we mean the big gray-matter one) will also demand blood, and if it can’t get it, things are not going to function well.

There are many other neurons feeding into the region of the hypothalamus that control blood pressure, so we suppose that quite a few bodily parts might have hands on the handlebars.

Blood pressure is a result of the power and speed of the heart pump and the resistance of the arteries and veins. Either one can be varied, and there are a variety of means to do so.

Beta blockers (a very bad idea, more here) are widely prescribed to lower blood pressure. They do lower it, although the exact mechanism is, amazingly, unknown. It is thought, though, that they interfere with some of the neural signaling, especially from the kidneys and decrease the force of contraction and rate of pumping of the heart and thus blood output, all of which decrease the blood pressure.

The astute reader will no doubt have noticed that we have in no way answered the question we posed, though central control is certainly a key. The main point, though, is that blood pressure regulation is very elaborate, and we would surely assume, very critical. As usual, we believe the body knows best and absent any major reason, it shouldn’t be tampered with.

Is it OK to starve the brain and kidneys? This would be a tough call for a doctor to have to make. Unfortunately, many doctors don’t see it this way, and see blood pressure itself as the disease and prescribe away. But blood pressure is not the disease. It is the body’s compensation to some other disease, most often atherosclerosis—the pipes are clogged. The cure is lifestyle change.

The Mayo Clinic says…

The Mayo Clinic appears to be in no hurry to throw pills at high blood pressure. Their current guidelines are:

  • If your blood pressure is below 120/80, fine.
  • If above 120/80, but below 140/90, it’s “Pre-hypertension,” and drugs are not recommended.
  • Above that, but below 160/100, it’s “Stage 1 Hypertension.” Try to reduce it with a lifestyle change and failing that, consider drugs.
  • Above that, do a lifestyle change and “discuss” taking medication with your doctor.

What blood pressure numbers to even believe…

Oddly, there is no clear consensus about how to measure blood pressure; or at least which measurements matter. For decades, the standard number that doctors treated were the ones obtained in the office when seeing the doctor for any reason whatsoever. Go see the doc, rush from train to bus to office and your pressure is high; then that is what gets treated. You go see the doc and you are having a nervous breakdown – obviously, this is somewhat apocryphal – and your pressure is too high, then they will treat that number. Thus, an unrepresentative pressure is being treated, therefor, under less stressful conditions, you are being over-treated. By the time you have been told ‘you could die’ because of your blood pressure, every time you see the doctor, or the nurse, approaching you with a blood pressure measuring device, your pressure will be too high, whether or not it is at any other time in your life.

So, what pressure do you treat and under what conditions do you have a number that warrants treatment?

The short answer, for now, for this blog, is that the doctor’s office-based pressures are the worst ones to treat. More reliable numbers to treat are home-based measurements, repeated three times at each testing occasion, and pressures measured on different days of the week and at various times of the day. A good home-based, daily diary is a good guide to treating, or not treating, blood pressure numbers.

Better even than home-based, multiple testing occasion diaries is true 24-hour ambulatory blood pressure monitoring. This is done with a special device that more and more physician’s offices have available. This type of device, gives you insight into your day and night time variance in pressures. Sometimes this diurnal variance is more important than any particular number, so try to get such information before acceding to blood pressure medications.

In future posts we will explore the most effective lifestyle changes to make to improve blood pressure.

  4 comments for “Blood Pressure: What controls blood pressure, and should we be attempting to change it?

  1. Jim
    December 4, 2016 at 12:08 pm

    In our local grocery store we have a blood pressure measuring station. When I use it I routinely get 115 – 120 / 65 – 70. It also tells me my heart rate is low ( i usually run at ~57 – 61). Do you feel the home machines are accurate?

  2. Jim
    December 4, 2016 at 6:12 pm

    Been using a good home monitor for nearly a year – over 1000 measurements. Pressures are close to normal (120/80), but standard deviations are 11/6. Than means ~32 % of the measurements are either over 131/86 or under 109/74. so much for “the” blood pressure.

    • Jim
      December 5, 2016 at 7:17 am

      How are you determining standard deviation – from repeated measures taken in one sitting or from the overall sample collected over time since the start of use.

  3. delma weldon
    December 12, 2016 at 3:09 am

    eating grains raises my blood pressure to dangerous levels, two slices of bread will take my blood pressure from 110 to 170 within 15 minutes

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