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Taking a
blood pressure
Area of Science: Biological Sciences
Meant for at least Grade 7-9 (age 11-13).
This experiment is inedible.
An adult should be present.
Overview:
Take a blood pressure.. correlate the blood pressure to the
heart's pumping of blood.
Equipment:
1. Sphygmomanometer (blood pressure cuff).. avail from the
school nurse?? A "child's cuff" should be used to allow more
accurate readings for children.
2. Stethoscope.
It would be helpful if someone who knows how to take a blood
pressure is present to supervise, as the technique requires
some practice. Also you want to avoid keeping the cuff
inflated on someone's arm for too long.
Safety:
Don't put the cuff around your friend's neck.. :).
How to do the experiment:
1. Deflate the bladder of the cuff and place it around the
upper arm so it fits snugly, but not too tightly. If you're
right handed, you should hold the bulb/pump in your left hand
to inflate the cuff. Hold it in the palm so your fingers can
easily reach the valve at the top to open/close the outlet to
the air bladder wrapped around the person's arm.
2. Put the head of the stethoscope just under the edge of the
cuff, a little above the crease of the person's elbow. Hold it
there firmly with the thumb, or with a few fingers of your
right hand. Put the ear pieces of the stethoscope in your
ears.
3. Inflate the cuff with brisk squeezes of the bulb. Watch the
pressure gage as you do it. For most kids, you shouldn't need
to go over 150 (the markings indicate "pressure" in mm Hg or
mercury).
4. At 150, slightly open the valve on the air pump (held in
your left hand, as above). This part takes practice.. It's
important that you don't let the air out too suddenly.
Likewise, your friend will be quite irritated with you if you
let it out too slowly.
5. Now, pay attention *very carefully* to what you hear
through the stethoscope as the needle on the pressure gage
falls. You will be listening for a slight "blrrpp" or a
something that sounds like "prrpshh." The first time you hear
this sound, note what the reading was on the pressure gage.
This value represents the systolic blood
pressure (described below).
6. The sounds should continue and become louder in intensity.
Note the pressure reading when you hear the sound for the last
time. This value represents the
diastolic blood pressure.
7. Afterwards, open the air valve completely to release any
remaining pressure.
In adults, hypertension is defined as regular BP readings >
140/90. However, kids should have BP lower than the normal
values for adults.
Here's a quiz to test your knowledge: (the answers are at
the bottom)
- What is the
life span of red blood cells?________
- The main
function of ________________ is to defend the body against
infection.
- What is the
name of the process that generates new red blood
cells?____________
- _________ play
an essential role in the blood clotting process.
- How many blood
cells in the human body die each second?_____________
- What blood
cells carry oxygen to tissues through out the
body?__________
Answers:
- 80 to 120 days
- White Blood
Cells
- Erythropoiesis
- Platelets
- 2 Million
- Red Blood
Cells
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