What is Blood Pressure?
Part 1 on blood pressure. What is blood pressure, and why is it important?
Chronic high blood pressure, or hypertension, is responsible for a huge amount of death and disease, affecting nearly 60 million people in the US. It is the #1 reason for visits to the doctor and the #1 reason people need prescription drugs. Despite all that attention, blood pressure is poorly understood and is often poorly controlled, resulting in a multitude of problems. It’s a huge topic, and (predictably) impossible for me to cover in a single article, so I will once again split it up into two. Today I’ll try to explain what blood pressure is, and next week I’ll explain the consequences of high blood pressure.
What is Blood Pressure?
Your blood pressure is the pressure used to get the blood to where it is needed. Have you ever gotten into the shower in the morning only to find out that there isn’t any water pressure? It’s not a fun thing. It not only can make you really grumpy, it can cause those around you to be grumpy about the smell you emanate. Blood pressure is much the same. The bloodstream carries oxygen and food to cells in the body, and it carries away waste products. Insufficient blood flow, then, results in cells suffocating, starving, and not getting rid of potentially toxic waste. That not only makes the cells pretty grumpy, it can kill them.
What is Needed for Good Blood Pressure?
Two things are essential to maintain good blood pressure: good pipes and a good pump. Blood vessels are the pipes in your body. The arteries are like the water pipes, requiring higher pressure to bring the essential fluid to where it is needed. The veins are the pipes that bring back the used blood, much like the sewer system, and don’t require as much pressure. When we talk about blood pressure, we are really talking about the pressure in the arteries.
How are Your Heart and Blood Pressure Related?
The pump in your body is, of course, the heart. The heart is a hollow muscle that squeezes blood out to the body. There are two chambers, called ventricles, that do the pumping:
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Right ventricle:Â The right ventricle pumps blood to the lungs so it can get oxygen.
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Left ventricle: The larger left ventricle pumps blood to the rest of the body.
The two parts of the heart’s pumping cycle are important because they coincide with the two important blood pressure numbers.
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Systolic pressure:, Systolic pressure happens when the heart squeezes, and
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Diastolic pressure: Diastolic pressure is the lowest pressure in the cycle, which happens when the heart relaxes.
So when a blood pressure cuff is inflated, the highest pressure at which the person listening with the stethoscope hears a “thunk” is the systolic pressure. The lowest pressure in the cycle, or the diastolic pressure, is signified by when the “thunk” sound goes away. Here’s why both are important.
What Happens When Systolic Blood Pressure Gets too Low?
The systolic pressure is essential to get blood to the brain. Just like the shower upstairs, a low pressure in the pipes will make the pressure to a person’s upstairs inadequate. It’s pretty important that the brain doesn’t stop functioning, so inadequate blood flow to the brain is not tolerated. If the pressure in the pipes isn’t adequate, the body takes drastic measures to make sure the brain gets enough blood: it passes out. The exchange goes something like this:
Your brain says, “Hey, I need more blood! I am starving and can’t breathe!”
“I am trying as hard as I can!” the heart responds. I’m even beating faster!”Â
“It’s not enough,” gasps the brain. “I need food and oxygen. I need it now!”
“I just can’t get blood up there. You are too high up! Can you make my job easier?” the heart begs.
“No problem” says the brain, and passes out, causing the body to lie on the ground.
“Much better!” responds the heart. Now I can get you all the blood you need.
Pretty cool isn’t it? You don’t get that kind of drama on the Grammar Girl podcast.
Low systolic blood pressure is an immediate problem; if it gets too low, you can’t live. A high systolic pressure isn’t that big of a deal in the short run, in fact, it’s the diastolic number we focus on more for treatment. That’s because the diastolic pressure causes more harm in the long-run.
What Should Your Blood Pressure Be?
What’s a good blood pressure? It depends on the age and size of the individual. Little kids don’t have as much gravity to deal with, so they don’t require as high of a blood pressure. For adults, the normal range for systolic blood pressure (which is the first number in the reading) is between 100 and 130 millimeters of mercury. Millimeters mercury expresses the amount of pressure in terms of how high it can push a column of mercury – which is a real heavy liquid. You probably noticed that silver stuff in some blood pressure measuring devices? That’s mercury.Â
Systolic pressures in the 90’s are OK as long as there is no fainting or dizziness, but below that is usually the sign of trouble.
The diastolic pressure should ideally be below 80. There is no official number for a low diastolic blood pressure and there are few conditions that cause it to be low without also bringing down the systolic.
Quick and Dirty Tips for Blood Pressure
I’ll stop here now, giving you a few quick and dirty tips regarding your blood pressure. My next article will specifically cover the issue of high blood pressure.
Tip 1: Get your blood pressure checked.
A good goal to shoot for is 120/70. Since high blood pressure doesn’t usually have symptoms, you need to get it checked regularly.
Tip 2:Â If you want to know when to worry about your blood pressure, read my next article.
If you have questions you want answered, send them to housecalldoctor@quickanddirtytips.comcreate new email. You can find me on Twitter as @housecalldoc and on Facebook under “House Call Doctor.”
Let me remind you that this article is for informational purposes only. My goal is to add to your medical knowledge and translate some of the weird medical stuff you hear, so when you do go to your doctor, your visits will be more fruitful. I don’t intend to replace your doctor; he or she is the one you should always consult about your own medical condition.
Catch you next time! Stay Healthy!
Blood Pressure image courtesy Shutterstock