Vital Signs Series: What is blood pressure?

In honor of my graduating nursing school, and in an effort to help myself not only retain information, but also learn more new information... and to share with those who are interested, I've decided to do series on vital signs - covering blood pressure, heart rate, temperature and oxygen saturation/respirations.

I find most people that I talk to may have somewhat of an understanding of what a high temperature, or what a high or low heart rate is, but they don't understand the meaning or significance behind it. You may know that you have a fever, but what does that really mean?

So if you're the type of person who is interested in learning about the very basics of how your body functions and keeps you alive, then you're in the right place. Also for the sake of simplicity, this series will be relevant to adult health. Infants, children and adolescents vital signs can vary from adults and I don't want to open that can of worms right now. So without further ado....

Today is the first part in the series, and I'm going to cover blood pressure. Blood pressure not only affects your elderly grandparents, but can also affect and complicate pregnancy. Just because you may be young doesn't mean you get a 'get out of jail free' card. High or low blood pressure can and does affect young adults as well, and it is important that you understand the consequences of each.

What is blood pressure?

I want you all to pretend we're plumbers now. Imagine your heart is a big huge pump, and all the veins and arteries in your body are pipes that are all connected to your heart. Some of the pipes (arteries) deliver blood to your body and other pipes (veins) deliver blood back to your heart (the pump). 

Now you probably are all aware there are two numbers in a blood pressure reading... 120/80 for example. The first number represents the amount of pressure exerted on the walls of your arteries (pipes) by the blood when it is pumped from your heart (the pump). The second reading is representative of the amount of pressure exerted on the walls of your arteries (pipes) when the heart (the pump) is at rest.

Your heart pumps, then rests "or resets" and the pumps again, the rests again, over and over and over and over until you eventually die!

So again, the top or first number, is the amount of pressure on the walls of your arteries when the heart pumps the blood (we call this systole), and the second reading is the pressure on the walls of your arteries when the heart is 'resting' (we call this diastole).

Have I lost you all yet?

All the tissues in your body MUST have oxygen and nutrients to survive. Without it, stuff starts to die, case closed. The blood is what transports all this oxygen and nutrients to your tissues, picks up all the wastes (C02) and then goes back up to your heart and lungs to be reoxygenated, only to be sent on the journey again and again.... and again... In order for all of this to occur, you have to have not only a blood pressure, but a blood pressure that has sufficient power to deliver the blood to all the places of your body: your organs, your hands, your toes, etc.

The danger we run into with a low blood pressure is that the blood is not able to get to all the far reaching places of the body to oxygenate it. If this is sustained for any lengthy period of time then your tissues die and your organs shut down, and then you too, eventually die.

The danger with a high blood pressure is it can actually weaken and damage your arteries and various organs, leading to increased risk of blindness, heart attack, stroke, heart failure and kidney disease. Imagine you're watering a plant with a hose, at a normal amount of pressure you simply dampen the dirt and water the plant, if you turn the pressure up to high you cause all the dirt to spray everywhere, exposing roots and ripping off leaves and petals.

Now that you understand in a nutshell the effects of high and low blood pressure let's establish what a normal blood pressure reading would be for an adult.

NORMAL SYSTOLIC: 90-120

NORMAL DIASTOLIC: 60-80

*below 90/60 your blood pressure is considered too low*

A systolic of 120-139 or a diastolic of 80-89 is what we consider 'prehypertensive' or an 'at risk' stage for developing high blood pressure (or what we medical folk call hypertension). 

Hypertension (high blood pressure) is considered a systolic above 140 or a diastolic above 90. If your blood pressure is above 140/90, it is considered high. There are different stages to high blood pressure (hypertension) but we won't get into that.

----------------------------------------------------------

I could go on forever and ever, but I won't. So thus concludes this first part of my vital signs series! Stay tuned for the next installment in which we will talk about the causes of high and low blood pressure and what we can do to change our risk factors!

References: Nursing a Concept Based Approach to Learning, Volume 1, Pages 1162-1176