Understanding Blood Pressure – An Introduction

While most of us have a basic understanding of what blood pressure is, it’s surprising how few fully grasp what it tells us, how it works or what ‘good blood pressure’ should look like. Blood pressure is one of those things that doesn’t really get explained to us at school and that we subsequently might not take the time to learn. So when your doctor tells you that yours is 105/100 you don’t know whether to smile or not (you shouldn’t be smiling).

This article then will serve as a short primer to help bring you up to speed if you aren’t familiar with what blood pressure is really all about.

What Is Blood Pressure?

To begin, let’s start by asking this basic question: what is blood pressure?

Essentially, blood pressure refers to the amount of pressure our heart is providing our blood with in order to move it along. This works in just the same way as pressure in your boiler system and it basically means that the fluid is so tightly packed into the veins/pipes, that a small push will cause it all to move.

Having low blood pressure is actually dangerous too then, as this can make it hard for your blood to reach your brain resulting in you feeling light-headed and dizzy very easily.

Likewise though, if your blood is packed in too tightly, this can also cause problems as the heart may no longer be able to pump it around. This can then result in a heart attack, a stroke or other issues.

So what causes blood pressure to be high or low? This comes down to a number of things, including physical fitness (which impacts on how hard the heart needs to beat), vasodilation (the width or the veins) and the viscosity of the blood. Blood viscosity in turn can be affected by our diet through cholesterol, as well as by medication such as decongestants and statins. Even hydration affects blood pressure, as can stress which causes the heart to beat vaster and the veins to dilate while the blood thickens.

One thing that’s key to keep in mind here is that your blood pressure varies throughout the day. Contrary to popular belief, you do not have ‘one’ blood pressure reading and it instead can change just as rapidly as your heart rate can change. For this reason, a good doctor will always take at least three measurements of your blood pressure and then use the average. If they are concerned, then they will normally ask you to undergo continuous blood pressure monitoring for 24 hours or longer in order to get a more complete picture of your blood pressure.

What Do the Numbers Mean?

So with all that in mind, how do you go about understanding blood pressure and what the numbers are telling you?

If you do go to the doctor and get your blood pressure measured, you’ll find you’re given not one but two numbers with one being written ‘over’ the other.

The first number is your systolic blood pressure. This is the highest pressure that your blood reaches when your heart beats. The second number is your diastolic blood pressure, which is the lowest level of your blood pressure in between beats.

This is important because it shows not only how tightly packed your blood is in your veins but also how effective your heart is at driving that blood around your body.

High diastolic blood pressure is the biggest problem as this means that even when your heart is resting, your blood is still packed in tightly. Being fit shouldn’t mean your systolic levels are super high though either – as even if your heart is stronger it shouldn’t be working too much when you’re resting.

What Is Ideal Blood Pressure?

Ideal blood pressure is generally considered to be 120/80. However, the average individual is likely to have blood pressure higher than this all the way up to 140/90. While 140/90 is not considered abnormally high, it is still important to take steps to try and lower it if your blood pressure is around this level. The reason for this is that even small differences can have relatively profound effects on your health. Did you know for instance that someone with a blood pressure of 135/85 is twice as likely to have a stroke or heart attack as someone with blood pressure of 115/75?

How Blood Pressure Monitors Work

So when you go to the doctor and they put that inflatable armband on you, how is this telling them the state of the blood inside your veins? This can seem a little bit like black magic but actually there’s a simple explanation.

The proper term for a blood pressure monitor is actually ‘oscillatory device’. Here, the cuff is fed over the arm and then inflated to prevent blood flow through the artery. Specifically, the cuff is inflated to reach 20mm Hg over the individual’s systolic blood pressure at which point the heart will no longer be able to force the blood through. Once this is then allowed to deflate, the blood will begin flowing through the artery again forcefully, thus creating slight vibrations in the arterial wall. Eventually, the cuff will fall lower than the patient’s diastolic pressure and this will then allow blood to flow more smoothly through the artery again, causing the vibrations to cease.

But looking at when the blood stops flowing and when it starts flowing smoothly again, it is thus possible to deduce the systolic and diastolic pressure! A transducer is used to detect the subtle vibrations through the arterial wall and this is then displayed on a small monitor.

How to Lower Your Blood Pressure

That’s all good and well but now that you know your blood pressure is abnormally high, how do you go about lowering it and getting it back down to normal?

There are a few things you can do here.

One is to eat a diet designed to help improve your blood pressure. There is some disagreement on what a ‘low blood pressure diet’ should look like. Interestingly, lowering salt intake seems to lower blood pressure but doesn’t seem to reduce the risk of heart problems (1).

Likewise, the role of fat has also been called into question. It is recently coming to light that saturated fat does not lead to high cholesterol and blood pressure (2) though not everyone agrees.

What we can agree on is that processed foods filled with trans fats are bad for blood pressure. Sugar also appears to cause problems via inflammation and the use of decongestants and statins can lower very high pressure. Drinking more water also improves blood pressure simply by diluting it and some foods that act as vasodilators can widen the veins and arteries to positive effect. Smoking and drinking alcohol are both activities that are universally recognized as being bad for the heart and the blood pressure.

Meanwhile, exercising regularly can improve your heart health and this too will lead to better blood pressure and overall cardiovascular well-being.

Now you know, there’s no excuse! And if you currently have no idea what your blood pressure is, consider taking a trip to your GP to find out.

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