11 – Blood Pressure and Vascular Resistance

Question 1

What is the best way to maintain perfusion?

Answer 1

-regulating MAP
>CO x SVR
*need to have a pressure gradient to get unidirectional flow

Question 2

Blood pressure is the:

Answer 2

-force of blood exerted on wall of blood vessels
*critical for maintaining organ perfusion/blood flow

Question 3

SBP:

Answer 3

-systolic blood pressure
-ejection phase

Question 4

DBP:

Answer 4

-diastolic blood pressure
-relaxation phase

Question 5

Pulse pressure equals:

Answer 5

SBP - DBP
*proxy for SV
-indirect assessment of vascular compliance

Question 6

Pulse pressure increases:

Answer 6

-with greater LV ejection
-in stiffer, non-compliant arteries (increase SBP)

Question 7

Mean arterial pressure (MAP):

Answer 7

-average pressure in arteries during 1 cardiac cycle (includes SBP and DBP)
-indicator of organ perfusion

Question 8

MAP equation 1:

Answer 8

MAP=DBP + 1/3 (pulse pressure)

Question 9

MAP equation 3:

Answer 9

MAP=CO x SVR
>can remove the +CVP as it is often 0

Question 10

SVR:

Answer 10

-systemic vascular resistance
-influenced by vascular volume of small arteries
-inversely related to vascular volume

Question 11

CVP:

Answer 11

-central venous pressure
-pressure in vena cava near right atrium
-often close to 0

Question 12

Cardiac output and MAP relationship:

Answer 12

-linear
-as Q increases, MAP increases
*if increase SVR=increase pressure at the same cardiac output

Question 13

CPR and BP:

Answer 13

-dropped
-pulse pressure has decreased due to reduction in SV
>CPR is not as good as a beating heart, but contraction number isn’t changing
-cerebral perfusion during diastole is decreased (not as much blood going into aorta)

Question 14

Various tools of the trade to measure BP:

Answer 14

-stethoscope
-ECG or arterial palpation
-doppler or sphygmomanometer
-capillary refill time
-jugular vein distension (pulse)

Question 15

Doppler:

Answer 15

-indirect way to measure BP
1. inflate cuff above systolic pressure=no blood getting past
2. As deflate cuff=hear a spike as blood is now flowing
3. Normal sound returns=diastolic pressure (hard to determine)
*often just rely on systolic pressure

Question 16

Capillary refill time (CRT):

Answer 16

-1.5-2s
-slow vs. fast

Question 17

Slow CRT:

Answer 17

-discoloured (grey, white)
-indicator of poor circulation
-common with heart problems

Question 18

Slow CRT may indicate:

Answer 18

-low BP
-hypovolemia
-dehydration
-shock
-low or high pulse rate (arrhythmia)
-anemia
-capillary rarefaction

Question 19

Fast CRT:

Answer 19

-discoloured (red)
-uncommon
-indicator of over perfusion

Question 20

High CRT may indicate:

Answer 20

-high BP
-high pulse rate
-local inflammation

Question 21

Jugular vein distension (JVD) occurs when:

Answer 21

-central venous pressure is above normal healthy value
>blood can back up into the veins causing them to bulge (and pulse)

Question 22

Various reasons for JVD:

Answer 22

-cardiac tamponade or pericarditis
-vena cava obstruction
-tricuspid valve stenosis
-right sided heart failure or pulmonary hypertension

Question 23

Cardiac tamponade or pericarditis:

Answer 23

-restricted filling

Question 24

Vena cava obstruction:

Answer 24

-tumor in chest preventing blood from entering atria

Question 25

Tricuspid valve stenosis:

Answer 25

-valve can be stiff
>entry of blood from atria to ventricle is impeded

Question 26

Right sided heart failure or pulmonary hypertension:

Answer 26

-right ventricle does not empty during systole (increased afterload)

Question 27

Length of artery and resistance:

Answer 27

-longer=more resistances

Question 28

Viscosity of blood and resistance:

Answer 28

-increased viscosity=increased resistance

Question 29

Radius of artery and resistance:

Answer 29

-larger=less resistance
*effects are exponential to the power of 4

Question 30

Vascular tone:

Answer 30

-amount of vasoconstriction experienced by a blood vessel relative to its maximally relaxed or dilated state
*increased=more constricted

Question 31

Tunica media:

Answer 31

-middle layer of blood vessel
-contains vascular smooth muscle that can contract or relax
-always exhibits some level of contraction in basal state
>so you can constrict more or dilate

Question 32

Vascular tone of the whole arterial system is a primary determinant of:

Answer 32

-systemic vascular resistance

Question 33

Vascular tone, vascular resistance and blood flow are:

Answer 33

-organ dependent
*degree of vascular tone by any artery is dependent on the organ it supplies

Question 34

Arteries to heart and skeletal muscle:

Answer 34

-have a huge capacity to dilate

Question 35

Arteries to kidney or brain:

Answer 35

-don’t have a huge capacity to dilate
>don’t want to increase volume in brain too much=headache

Question 36

Vasoconstriction and vasodilation factors:

Answer 36

-extrinsic
-intrinsic

Question 37

Extrinsic factors:

Answer 37

-serve to maintain systemic BP
Ex. neurohumoral factors

Question 38

Intrinsic factors:

Answer 38

-important for blood flow regulation within an organ

Question 39

Examples of intrinsic factors:

Answer 39

-myogenic
-endothelial
-local substances
-metabolic by-products
-hypoxia

Question 40

Change in cardiac output from at rest to exercise:

Answer 40

-5 to 18L/min
-brain: remained the same
>redistribution to active areas
-reduced blood to renal
-increased blood to skeletal muscle

Question 41

Increased blood to skeletal muscle during exercise:

Answer 41

-factors that cause dilation
>hypoxia
>CO2
>shear
>ACh spillover
>H+
>ATP
*if pathway was impaired: would get increased pressure!