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Understanding Blood Pressure

Blood pressure is the force of blood against the walls of the arteries as it moves through the body. Each and every time the heart beats (or contracts) it squeezes the blood that is inside it.

This blood then rushes out through a valve in the heart and into the arteries. Arteries are those blood vessels that move blood away from the heart.

The blood comes out with a lot of force… or pressure. Now blood pressure in general is a good thing. It is what moves the blood through the body supplying oxygen and nutrients essential for life.

Blood Pressure and Pulse

So when blood is pushed out of the heart during a heart beat, there is pressure exerted on the arteries which forces the arteries to expand. This expansion of the arteries can be felt.. It is your pulse. When you check your pulse you are in fact feeling your arteries expand in response to an increase in blood pressure caused by the heart contracting. 

This “pulse” of high blood pressure is also known as systolic blood pressure. So, to restate it, systolic blood pressure is defined as the highest pressure your blood vessels are exposed to during a normal heart beat.

After your heart contracts, it will then take a break for a moment and relax. During this relaxation period it fills up again with blood. At the same time the arteries shrink back to normal size due to a drop in pressure. This “low pressure” phase is known as diastolic blood pressure. So diastolic blood pressure is the lowest pressure the arteries experience as the heart is relaxing. 

As you can see the arteries are constantly being punished by the heart. Every time the heart beats the arteries expand due to the pressure of blood flowing though them. This occurs about 70 times a minute when someone is at rest. This translates to about 100 000 times a day. Talk about torture.  To make matters worse, if you have high blood pressure, your arteries are stressed out even more because each and every one of those heart beats exposes your arteries to an “above normal” spike in pressure. Not a good thing at all and all the more reason to do everything you can to keep your blood pressure in a normal range. 

What is normal blood pressure?

First of all blood pressure is measured in mmHg. This term refers to the height to which a column of mercury is raised by an equivalent pressure. Today’s blood pressure machines use newer technology to measure blood pressure, but the units of measurement remains. Using this measurement, normal blood pressure is anything less than 120/80 mmHg. 

I have seen blood pressure numbers plenty of times, but while working on this article I started to wonder. What exactly does that mean? How does that relate to something I can actually understand? So I started looking at other units of measurements for pressure and the psi (pounds per square inch) seemed to make more sense. 

An Interesting Perspective on Blood Pressure

PSI is the force in pounds for every square inch of surface area. So a pressure of 1 psi is like having a one pound weight resting on a square inch of surface. So 120mmHg is equivalent to 2.32 psi. Imagine your blood vessels have to hold back a force of 2.32 pounds for every square inch of surface area. This doesn’t sound like much so let’s put this in perspective.

Think about this. The average human body has about 2700 square inches of skin covering it. Imagine each square inch of skin having to support 2.32 pounds of pressure. That would be 6264 total pounds! And your arteries withstand that amount of pressure 100 000 times a day during normal conditions. Absolutely amazing! 

OK, back to blood pressure numbers. What happens if one one or both of those numbers is higher than normal? Then your blood pressure is referred to as elevated. 

Elevated Blood Pressure

Elevated blood pressure is any reading between 120-129 systolic and less than 80 diastolic. And that’s in mmHg. It is that middle of the road place when your blood pressure is too high to be labeled as normal and at the same time not high enough to be considered hypertension or high blood pressure. It was a term that came about to indicate that numbers in this range need to be take seriously because elevated blood pressure, if left untreated, will usually progress to hypertension. 

Stage 1 hypertension?

This is the first stage of high blood pressure and is sometimes referred to as mild high blood pressure. Don’t let the label mild fool you. Any time your blood pressure is elevated, damage is being done to your body. Stage 1 hypertension is any reading that is between 130 – 139 / 80 – 99 mmHg. Blood pressure in this range is usually treated with medication and lifestyle changes. 

Stage 2 Hypertension 

Next we have stage 2 hypertension. It is defined as any reading that is 140/90 or higher. Stage 2 hypertension is a serious condition and requires aggressive treatment. Doctors will often start people with stage 2 hypertension on 2 medications in addition to lifestyle changes. 

Hypertensive Crisis 

Finally we have blood pressure that is over 180/120 mmHg. This stage is called hypertensive crisis and you can tell just from the name that it requires emergency care.

Keep in mind that in general blood pressure will rise over time. Many people will ignore blood pressure that is just a little high. The problem is even a mild elevation In blood pressure is damaging the body. This damage is slow and progressive and you cannot feel it happening.

Since over time blood pressure has this tendency to rise, before you know it you have progressed to the next stage. Any blood pressure reading above normal should be taken seriously and treated appropriately.