Friday, October 5, 2007

Apple #270: Blood Pressure

About a week ago, I donated blood. Then a few days later, I went to the doctor to ask them to tell me whether my broken toe was healing properly (it is, it's just taking a long time). Then another few days later, I had a "health assessment" done so I could get $10 off per month of my health insurance. In all three events, somebody tested my blood pressure.

They always tell me the numbers, and they always tell me it's good. But in truth, I have no idea what the numbers mean. I asked two of the three nurses who took my blood pressure to explain it to me, but they both said, "the first number is the systolic, and the second number is the diastolic." Totally unhelpful.

Time for the Apple Lady to get helpful.

  • When someone "takes your blood pressure," they're getting a measurement of the force of the blood as it hits your artery walls. It's a way of seeing how well your heart is working, if it's pumping too hard or if it's not pumping hard enough, and also how much room there is in your arteries for the blood to get through.
  • In most people, your heart beats about 60-70 times a minute when you're not exercising.

Measuring your pulse means you're counting the number of times your heart pumps per minute.
(Image from Oregon Health & Science University)

  • When your heart pumps, the blood rushes faster through your arteries. When it relaxes or contracts, the blood slows in your arteries.
  • Blood pressure measures those two extremes: the point of highest pressure when the heart is pumping, and the point of lowest pressure when the heart is relaxing.
  • The high pressure measurement is called the systolic pressure (the first of the two numbers), and the low pressure measurement is the diastolic pressure (the second).
  • There are all sorts of ways that medical people can measure blood pressure. But the most common method is to strap a cuff around your arm, secure it with Velcro, and inflate the cuff.

This is the cuff, with the pump that inflates it, the gauge that measures pressure, and the stethoscope the nurse uses to listen to your blood sounds. You can order this one for adults from Gould's Discount Medical for $48.

  • Here's what's happening when they're using that blood pressure cuff:
      • The nurse inflates that cuff until it literally stops the circulation in your arm.
      • Then the nurse releases the valve that allows air to escape the cuff slowly, thus relaxing the cuff and allowing the blood flow to begin flowing again into your arm
      • As the blood begins filling your arteries again, the nurse listens with a stethoscope to your arm near the cuff, in order to hear the sounds the blood is making as it re-enters your arteries.
      • The sound the blood makes changes as more blood flows in. At first, it makes a distinct tapping. The moment the nurse hears this initial tapping, whatever the number is on the cuff's gauge represents the systolic number.

This man is having his blood pressure taken. Apparently he's also told a joke or something that the nurse doesn't find that funny. It's nice that he's having a good time, but she's probably trying to listen to his blood sounds and would rather hear the joke when she's done.
(Photo from Independent Health Care Plan)

      • As the air continues to escape the cuff, the sounds get softer but the tapping or pulsing lasts longer, then for some reason the sounds get louder again and more distinct, and then the sounds grow muffled again, and finally they become completely indistinct.
      • The moment when the last sound is heard, the nurse records the number on the gauge as the diastolic number.
      • When the nurse is finished with the measurement, he or she will tell you, in a shorthand fashion, your systolic and diastolic pressure readings. For example, the last time my blood pressure was taken, the nurse told me, "It's 115 over 68. That's good."
  • Here is what the American Heart Association defines as healthy blood pressure ranges and what's problematic:




below 120

below 80




Stage 1 hypertension



Stage 2 hypertension

160 +

100 +

  • Of course these numbers are not absolute. Your blood pressure changes all the time, depending on whether you've just exercised, what you recently ate, if you're taking any medications, if you're sitting or standing, even what your mood is like that day.
  • Other factors that can affect your blood pressure reading more dramatically include:
      • As people get older, their systolic pressure gets higher while the diastolic gets lower.
      • Young children who are in the midst of a big growth spurt can have very high systolic numbers.
      • Some people also "test" high when in the presence of a doctor or a nurse because they're nervous. This is referred to as "white coat hypertension."
      • Some medications can also inflate your blood pressure. Sometimes that effect goes away when you stop the medication; in other cases it doesn't.
  • So if your blood pressure numbers are a little high on one occasion, that might not be a sign of a problem.
  • But if your blood pressure tests often enough in one of the other categories, you should talk to your doctor.

When there's less space for the blood to flow through, the pressure will be higher. So if your blood pressure readings are high, this might be happening inside your arteries.
(Diagram from Physical

  • In general, here's what the "problematic" categories mean:
      • Pre-hypertensive: it would be a good idea to improve your diet by doing things like reducing your salt intake, increasing the amount of leafy greens and whole grains you eat, and increasing the amount that you exercise.
      • Stage 1 hypertension: you and your doctor should monitor your blood pressure regularly, you'll want to make some fairly extensive changes to your diet, quit smoking, drink less alcohol, exercise more, etc. Your doctor might also prescribe you a medication to help reduce your blood pressure.
      • Stage 2 hypertension: your doctor will prescribe something to reduce your blood pressure as soon as possible. You'll also need to make radical changes in your lifestyle.

This blood pressure monitor is one of several available for people to test themselves at home. This one has an audio feature that reads the results aloud, and includes a jack for headphones if you want to keep those numbers private. It's avilable from QuickMedical for $120.

And here's something else that I feel like medical people don't say but should: if you don't test "normal," that doesn't mean you're a bad, bad person who needs to reform or just get it over with and die already (actually, I think it's the insurance companies who are responsible for that implication).

What it means is that, if you want to improve your the way your body works and how feels to move around in your body -- and maybe you don't -- you can do some things to improve your body's function. Though in some cases, you can't really help what's happening, so you'll want to find a way to live with what's going on the best that you can.

We're all human, our bodies get stuff wrong with them over time, the flesh gets tired. That's the way it goes. You can't give anybody bad marks for simply being alive.

American Heart Association, Blood Pressure
American Heart Association, Recommendations for Blood Pressure Measurement in Humans, December 20, 2004
Medline Plus, Blood pressure, July 21, 2006
Life Clinic, What is Blood Pressure?
ehealthMD, How is High Blood Pressure Treated? October 2004
Health A to Z, Hypertension


  1. Thank you for this, Applelady. I also have asked to have this explained to me and have gotten no good have solved an eternal mystery. Thank you.

  2. You're welcome, anonymous.

    Since I wrote this entry, I've had that diagram of gunk-lined arteries on my mind. Makes me wonder what's on the insides of my arteries. Yech.


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