Geek Out: The Highs And Lows Of Blood Pressure.

mmHg/understanding these numbers:

okay, let’s talk about these units because they are rather strange! In full, they stand for millimeters of mercury and the date back a couple of hundred years to when people were measuring pressures according to high high up a column of mercury would stand.

None the wiser (me neither ) but to give a context to this, atmospheric pressure (at sea level) is typically around 760mmHg so our blood pressure is considerably less than that.

Apart from blood pressure, I can’t think of a time where we’re going to see these units but if you’re keen to properly get to grips with them (and I applaud that) then click here :)

Long winding pathway/back to the heart:

We really have two circulations and two pumps to consider, the right hand side of the heart pumps blood into the pulmonary circulation - a series of vessels that take the blood to the lungs to pick up oxygen and the return it to the left hand side of the heart.  The left side of the heart, our second pump, ejects blood into the systemic circulation - a series of vessels that take blood to the many corners of the body, everywhere EXCEPT the lungs in fact.  Systemic vessels deliver oxygen rich, nutrient rich blood to your body so that your cells get everything they need to survive and carry out their appropriate functions.

When we talk about blood pressure it’s assumed that we’re talking about systemic pressure. Pulmonary pressures are just as important but are not easily measured and definitely not in the supermarket or with a home measurement system.

(We talked more about the actual role and route blood takes in a previous post “the most valuable liquid on earth”, click here to check it out.)

Brilliantly convenient:

It is possible to actually measure the pressures in the heart but this is definitely not something that could be done at home or even in a doctor’s office as it involved involves placing catheters in the heart or major blood vessels!

Spackle:

Spackle is a very popular US brand of filler used to repair cracks in walls, the Brits favored brand is Polyfilla

Hypotension:

There’s some funky math that might be useful here, the medical profession will talk about mean arterial pressure (MAP), which they calculate using the following equation (DP = diastolic pressure and SP = systolic pressure):

MAP = DP + 1/3 (SP-DP)

MAP needs to be 60mmHg or above to keep blood flowing though the body. Even if you’re right at the bottom of that normal range (90/60mmHg) then your MAP = 60 + 1/3 (90-60) = 60 + 10 = 70mmHg.

If our pressure gets much lower than that though, it’s likely that we’re not walking around not knowing our situation, we’re much more likely to already be under the care of the medical profession, and quite likely in hospital (it does vary a little, I have had teeny, tiny female students with blood pressure’s down this low who were perfectly healthy, but a 6’2'“ male rugby player with a BP of 90/60mmHg is almost certainly in a bit of a pickle).

One of the biggest issues for people whose BP is on the low side is that when they stand up quickly, the blood flow to their brain might not be quite sufficient to keep them upright and down they go. Ordinarily our brain and nervous system work together in situations such as this to bring our blood pressure rapidly back up and get that blood up to our brain. Like many processes, that’s one that tends to work less well as we age and is one of the reasons why the elderly are at greater risk of falls.