The Highs And Lows Of Blood Pressure.
We need pressure like we need sunshine and chocolate – not too much or too little, but just enough!
If we don’t pinch an egg with enough pressure we’ll drop it, but squeeze too hard and ..
We might need the pressure of a deadline to get that tedious work task done but constant pressure from a bad boss …
…is much less helpful.
Blood pressure works the same way – we need enough to make our blood flow but not so much that, well, it kills us.
And the “right amount” of blood pressure (BP)?
That’s somewhere between 90/60mmHg and 120/80mmHg, a piece of information that’s about as useful as a chocolate teapot if we don’t understand these numbers.
Sam’s blood pressure’s going to be useful here:
(Actually, I don’t know the generous soul who made their BP data freely available. I’ve named them Sam in homage to Samuel Von Basch, the brilliant scientist who, in 1881, invented the first blood pressure monitor.)
Understanding these numbers starts with a heartbeat, a heartbeat that pushes blood into the circulation at a high enough pressure to make it through the thousands of miles of blood vessels and back to the heart. If blood doesn’t leave the heart at a high enough pressure, it won’t have the energy to complete that marathon journey.
And we won’t survive.
Imagine using a straw to make bubbles in a drink.
Making bubbles is easy with a short, straight straw but we’ll have to blow much harder to see any bubbles if we use a fun, curly, straw.
Like breath and a curly straw, blood journeys through a long, winding pathway back to the heart and it’ll only make it if our heart pumps it out with sufficient oomph.
The blood in our arm still has around about the same pressure as when it was pumped into the circulation - brilliantly convenient because although it’s being measured in in the arm, that first BP number tells us how forcefully our heart’s contracting.
This first number is our “systolic pressure” as back in the mists of time, insecure scientists and physicians thought they sounded smarter if they used Latin and Greek, and the Greek for “contraction” is “systole”.
The second number?
In between contractions, our heart relaxes while it fills with the blood to be pumped out by the next beat. This relaxed, filling period is “diastole” (yup, more Greek) and because our blood vessels are also relaxed whilst awaiting the next blood delivery, the pressure in them is lower too – this is the bottom number, the diastolic pressure.
Between them, these numbers are giving our healthcare professionals intelligence on how hard our heart’s working (systolic pressure) and how relaxed (or not!) our blood vessels are (diastolic pressure).
That might make those numbers even more important than our bank account (or even bank balance) number!
Back to Sam.
Comparing his numbers (146/88mmHg) with those in the healthy range (90/60mmHg to 120/80mmHg) suggests Sam’s one of the 30% of adults worldwide with hypertension (high blood pressure).
Dubbed the “silent killer” because it’s frequently symptom free, every year hypertension disables and kills millions of people through often unexpected strokes, heart attacks and kidney failure.
Even though he might feel in tip top health, knowing his numbers gives Sam the chance to make lifestyle changes and/or take medication to reduce his BP and risk of these health disasters.
Knowledge truly is power.
Which is why, at least in the US, it’s standard practice for BP to be checked at EVERY healthcare visit, even if the original appointment was for an earache or funny- looking mole.
(The British NHS, brilliant in very many ways, doesn’t routinely measure BP. Surely this would be an easy, almost cost-free way to find more of the 30% before disaster strikes?)
Not only does Sam’s high systolic pressure flag that his heart is being overworked but it also sounds the alarm for both the immediate and long-term well-being of his blood vessels.
If he has a weak spot or two in a blood vessel wall (sometimes we’re born with these, sometimes we do things like smoke that help to make them!) then at any moment, his hypertension could cause that fragile vessel wall to rupture.
But even if he inherited wonderfully robust vessels and has never seen the appeal of cigarettes, his vessel walls will be damaged by the constant high-pressure bombardment. They’ll become cracked and although Sam’s body will patch the beaten-up walls, it won’t be to a craftsman’s standard. The cracks will be filled in with a cholesterol-laden spackle (plaque to cardiologists) and over time, as his high-pressure blood continues to damage his vessel walls, more and more uneven layers of cholesterol spackle will be spread across them.
Sam’s situation may now worsen as layers of cholesterol narrow the space inside his blood vessels making it harder for blood to get through. Blood will only be able to continue flowing through these constricted passageways if Sam’s heart gives it a more forceful push at the start of its journey – in other words, his blood needs to leave his heart at yup, a greater pressure.
And that means more work for his heart, further damage to his blood vessel walls, and more cholesterol patching. His heart will have to pump blood out at an even greater pressure, there will be more vessel damage and so on it goes.
As if that wasn’t depressing, pieces of the cholesterol patches can break off and float downstream to block a blood vessel. If that vessel’s in the brain, that blockage could reduce or even stop the supply of vital oxygen to that brain region and the cells there will die - this is a type of stroke. An obstruction in a vessel in the heart muscle can be the cause of a heart attack (myocardial infarction if we’re being fancy) and we all know that’s not a desirable event!
For all the reasons we’ve talked about, the medical profession has primarily worried about high systolic pressure, but research now shows that Sam should be concerned about his diastolic value of 88mmHg too.
That relatively high figure (remember, the upper end of the healthy range was 120/80mmHg) means Sam’s blood vessels are not relaxing as much as they should.
Like going on vacation but taking our laptop to the beach to keep on top of our e-mail - it’s not as stressful as being in work, but we’re not fully unwinding either.
Blood vessels, like the humans that own them, need quality down time and if they’re not relaxing enough, there are really big consequences. The American Heart Association states that whilst for every 20mmHg increase in our systolic pressure our likelihood of dying from heart disease doubles, it only takes an increase of 10mmHg in our diastolic pressure to get the same increased risk.
Yikes.
Happily, it’s never too late to improve our blood pressure. It might be more exercise (of the right type, lifting big weights is not a good idea!) or eating fewer of those salty snacks, but first things first, we need to know our numbers and talk with the professionals.
I had to leave so much out of this post - there’s not much here about about low blood pressure (head to the Geek Notes for a couple of thoughts on hypotension) or the amazing work our nervous system and kidneys do in helping us to manage our blood pressure.
Another post perhaps?
Stay curious,
