Lecture 4 Arterial Blood Pressure

From Iusmphysiology

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Revision as of 14:55, 21 January 2011

• continued here from [Lecture 3 Cardiac Mechanics] on 01/21/11 at 9:32AM

Contents 1 Objectives 2 Slide 2 3 Diastolic arterial pressure 4 Flow chart 5 Translation of the mechanical properties of large arteriels to cyclic systolic and diastolic arterial pressure 6 Long term changes in vascular distensibility and capacitance... 7 Measuring blood pressure 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84

Objectives

• Not many objectives but they are important.

Slide 2

Diastolic arterial pressure

• All the arteries get stretched, not just the aorta.

Flow chart

• When elasticity goes down, the diastolic pressure drops dramatically.
• Pulse pressure is the difference in the two pressurs. Usually about 40 mmHb.
  • Be suspicious if it gets higher.
  • There is usually something wrong with disensibility.

Translation of the mechanical properties of large arteriels to cyclic systolic and diastolic arterial pressure

• Capacitance is the volumne held in the vessel under a certain pressure.
  • One point in the curve.
• Compliance is the slope of the curve at a given point.
• Diastolic pressure depends on the relationship of distensibility and capacitance.
• Systolic pressure depends on the relationship between distensibility and capacity of the volume caused by cardiac pumping.

What's the difference here?

Long term changes in vascular distensibility and capacitance...

• When distensibility goes down, then when the heart stops pumping the pressure goes down so diastolic pressure goes down becauase there is no energy in the distenstion to keep the pressure up.
  • This is why there can be a widening of systolic and diasstolic pressure.
  • this is also why left ventricles get larger.
• If atherosclerosis is appartent in large arteries, it is considered to be plentiful in the smaller arteries.
  • This gets bad when coronary arteries are clogged but heart wants to use more and more oxygen for more and more vent tissue.

Measuring blood pressure

• Oliver Whendel Holmes brought BP measurement to the US, then became a supreme court judge.
• Recall the laploss relationship.
• Pinside (pressure inside the pressure) - poutside (pressure outside the vessel) = wall tention / radius.
• Once the vessel is closed with the balloon you can release the pressure.
• At some point the pinside will be higher than the poutside (the balloon pressure).
  • Blood will squirt through the artery and we can hear it with the stethoscope.
  • As the poutside is continued to lower, the sound will get louder and will last longer.
• Then the sound becomes muffled
  • This depends on the equipment and the hearing of the measurer.
• Then the pressure is lowered and the sound goes away because there is no turbulance.
  • When it disappears you're at the diastolic pressure.

• stopped here at 10AM on 01/21/11.
• started here at 11AM on 01/21/11.