Blood Pressure

1
Chapter 15

• Blood Pressure

2
Pulse

• The rapid pressure increase that occurs when the
  left ventricle pushes blood into the aorta can be
  felt as a pulse or pressure wave transmitted
  through the fluid filled arteries of the
  cardiovascular system.

3
Blood Pressure

• Blood pressure is highest in the arteries and
  falls continuously as blood flows through the
  circulatory system.
• Energy is lost due to resistance of the vessels
  to blood flow, and friction between blood cells

4
Blood Pressure

• In systemic circulation the highest blood
  pressure occurs in the aorta, and reflects the
  pressure generated by the ventricular systole
• 120 mmHg systolic pressure

5
Blood Pressure

• Aortic pressure falls steadily to a low of 80
  mmHg during ventricular diastole (diastolic
  pressure).
• Pressure in the ventricle falls to nearly 0 mm
  Hg, however the diastolic pressure in the large
  arteries remains high due to the ability of these
  vessels to capture and store energy in their
  elastic walls

6
Blood Pressure

• Estimate of aortic pressure
• Measured through brachial artery
• Systolic over diastolic pressure (mmHg)

7
Korotkoff sound

• As blood squeezes through the compressed artery,
  the Korotkoff sound can be heard through a
  stethoscope with each heartbeat as long as the
  artery is compressed.
• The pressure at which blood flow is first heard
  represents the highest pressure in the artery
  systolic pressure
• The point when all sounds disappears is the
  diastolic pressure

8
Sphygmomanometer

• Pressure cuff is inflated until it exerts
  pressure higher than the systolic pressure
  driving arterial blood
• Blood flow into the lower arm stops
• Pressure is releasedwhen cuff pressure falls
  below systolic arterial blood pressure, blood
  begins to flow again.

9
Figure 15-7
When the cuff is inflated so that It stops
arterial blood flow, no Sound can be heard
through a Stethoscope placed over the Brachial
artery distal to the cuff.
10
Korotkoff sounds are created by Pulsatile blood
flow through the Partially compressed artery
11
Blood flow is silent when the Artery is no longer
compressed.
12
Pulse pressure

• Measure of the strength of the pressure wave
• Systolic pressure diastolic pressure pulse
  pressure

13
Mean Arterial Pressure

• Average aortic pressure during the cardiac cycle
• Arterial blood pressure reflects the driving
  pressure created by the ventriclecloser to DP
  because diastole lasts twice as long as systole
• Mean arterial pressure diastolic pressure 1/3
  (pulse pressure)
• MAP Diastolic pressure 1/3 (systolic pressure
  diastolic pressure)

14
Blood Pressure

• Blood flow into the aorta is equal to the cardiac
  output of the left ventricle
• Blood flow out of the arteries is influenced by
  the resistance of the arterioles (peripheral
  resistance
• MAP ? CO x R arterioles

15
Figure 15-9
16
Figure 15-10
17
Figure 15-21
18
Figure 15-22
19
Figure 15-23