Blood Pressure.

Blood pressure (BP) is very important as a difference in pressure is what drives blood to move around the body. Although the heart does the pumping of blood, the ultimate difference in pressure is important for the movement of blood.

When BP drops, people can experience a sensation of lightheadedness. This is because less blood is traveling to the brain, and thus the brain is receiving less oxygen. Without a good supply of oxygen, we tend to feel light in the head and can even black-out.

Measuring BP is clinically important as it gives hints as to how the blood is traveling through the body and about the quantity of the blood. For instance, if you are dehydrated, you'll have less blood, and a lower BP.

In conjunction with taking someone's BP, his or her pulse is also measured. People often think that the pulse is the heart beating. The pulse is actually a pressure wave that is resulting from the beating of the heart.

A higher BP is generally considered unhealthy. With that being said, if you were to take my BP before I wrote my Bell-Ringer exam on Wednesday, my BP would probably be pretty high even though I am a pretty healthy individual. That is because our BP tends to fluctuate all day long depending on mood, circumstances, hydration, etc. When we are stressed, our BP will rise. However, it only takes two heartbeats to bring our BP back to normal levels, so it is really only those with chronic high BP that are at risk.

BP is measured using a sphygmomanometer. Below are the basic steps to reading someone's BP. (***Note: these steps are very general (I was taught the proper way in class, but I am including only a summarized version). If you want to learn how to properly take someone's BP, you should consult other sources than this blog alone and consult a health care practitioner).

1) Place the cuff of the sphygmomanometer right above the crease of the elbow, which is right above the brachial artery.
2) Place two fingers on the brachial artery. Inflate the cuff until you can no longer feel the radial pulse.
3) On the dial of the sphygmomanometer, read the value when the pulse is not felt.
4) Now, ask the patient to raise hand above head and squeeze his or her hand 10 times. This stimulates his or her muscles, allowing them to contract. Then ask him or her to bring his or her hand down; now when the hand is down, blood should flow normally.
5) Pump the sphygmomanometer 30 values above the value recorded previously (the point where blood flow stopped), then start to deflate the cuff.
6) Listen to the BP sounds (note: there are 5 phases of sound, but I won't discuss them now) and record the the value at the end of hearing Phase 4.


  1. aaah - it is true if you are dehydrated you have very little blood flow?

    I was to have blood drawn once and the tech couldn't get a good flow and questionned my hydration.Maybe I was a little dehydrated???


  2. That could have been the case! Humans are 80% water, with a lot being in our blood!


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