Blood pressure

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Blood pressure 1
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Outline for today

• Review midterm
• Temperature Review
• Blood pressure basics
• Visit by Dr. Anthony Viera
• Measure your own blood pressure
• List problems and possible errors
• Blood Pressure measuring instruments

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Blood Pressure Basics

• Definition Pressure Force/Area
• At 0 deg C and standard gravity 981 cm/sec2
• Corrected for atmospheric changes
• Units
• 1 torr
• 1 mm Hg
• 1328 dynes/cm2
• 13.6 mm H20
• 13.1 mm saline
• 12.9 mm blood

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Occlusive Cuff Methods Sphygmomanometer

• Apply cuff to upper arm
• Position stethoscope over artery at elbow
• Inflate cuff to high (180 mmHg) pressure
• Release pressure slowly (10 mmHg/sec)
• Listen for Korotkoff Sound at each heart beat
• Appearance of first sound is systolic pressure
• Disappearance of sound is diastolic pressure

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Cuff measurement
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Korotkoff Sounds - description
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Normal Systolic and Diastolic pressures
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Heart Sounds
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Blood pressure questions

• Where is the highest blood pressure in the body?
• Where is the lowest blood pressure?
• What is the minimum pressure needed to survive?
• Why is your heart located in the chest?
• How does a giraffe pump blood to its head?
• What is your blood pressure in Denver compared to
  sea level?
• Where are the pressure sensors in your body?

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Where is the heart?
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Blood Pressure questions cont

• How is blood pressure regulated?
• What is the relationship between heart rate and
  body size?
• What is the relationship between heart rate and
  respiration?
• How do you measure blood pressure in the
  capillaries?
• What is your blood pressure in Denver compared to
  sea level?
• Does blood pressure have to be pulsitile?
• Does the pulse reach all the body at once?
• What is origin of Korotkoff sounds?

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Sources of Error-velocity effect
Total Energy Pressure energy velocity energy
height energy
E Ps Mgh (1/2)mv2 Where Ps Static
Pressure M mass ggravitational accelleration
Vvelocity
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Bernoulli effect
In this example of a fluid flowing initially in a
large cylinder and then flowing in a small
cylinder before returning to the large cylinder,
note that the velocity in the middle must
increase. Since the Total Energy must be the
same, the increased velocity means more kinetic
energy, the resulting static pressure must be
less
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Velocity/pressure errors in body