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CPR Exam 1 > Circulation and Hemodynamics > Flashcards

Circulation and Hemodynamics Flashcards

1
Q

What are the relative pressures of the following vessels:

Arteries

Arterioles

Capillaries

Veins

A

high pressure

moderate pressure, Sm.M can moderate

large XS area (low velocity, low pressure)

low pressure, large volume

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2
Q

how do you calculate velocity of blood flow?

A

V=Q(flow)/A(area)

can be calculated for a single vessel knowing its XS area and flow

OR

knowing total summed XS area of parallel circuits and flow

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3
Q
A
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4
Q

What is the relationship between flow, pressure, and resistance?

A

Q=change in P/R

can be determined through individual vessel or segment of vessel or through entire system

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5
Q

What is the equation for cardiac output?

A

CO=Arterial pressure-venous pressure/TPR

Or CO=BP/TPR

or CO=HRxSV

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6
Q

What is Poiseuille’s law equation for resistance?

What is the relationship between the constants?

A

R=(8nl)/pir^4)

n=viscosity (dehydration can increase, anemia can decrease)

l=length of vessel (can increase or decrease with body habitus)

pi=is pi

r=radius (vasoconstriction decreases radius, increases resistance, vasodilation increases radius, decreases resistance) *Most significant determinant*

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7
Q

Adding resistance beds in series does what?

Adding resistance beds in parallel does what?

A

increases resistance (series=R1+R2+R3…)

decreases total resistance (parallel=1/r1+1/r2+1/r3…)

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8
Q

When does blood flow become turbulent?

A

when velocity is high

when XS area is large

when density is heavy

and/or

when viscosity is low

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9
Q

What equation can predict turbulence?

A

Reynolds number

Nr=pdv/n

p-denisity, d-diameter, v-velocity, n-viscosity

if greater than 2000, then considered to transition from laminar to turbulent flow

leads to bruit and arteriosclerosis

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10
Q

What is blood vessel compliance?

A

describes how easy it is to cause a vessel to expand

how much does the vessel expand in response to a given change in lumen hydrostatic pressure

compliance =change in volume/change in pressure

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11
Q

How do you change compliance?

A

Smooth muscle contraction causes a shift in compliance, moving blood to arterial side and increasing pressure

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12
Q

Describe the pressure changes in the cardiovascular system

A

pressure gradually drops through the systemic circulation

pulsatile in nature at aortic end due to compliance and distension during ejection and recoil during diastole, lost by arterioles.

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13
Q

What is clinically reported as systolic pressure?

What is clinically reported diastolic pressure?

A

greatest pressure reached in a large artery

lowest pressure reached in large artery

(120/80, pulse pressure is systolic-diastolic=40, mean pressure = diastolic+1/3 pulse pressure=80+(40/3) = 93.3

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14
Q

Since pulse pressure is dependent on the arterial compliance, what happens when you decrease compliance?

A

Pulse pressure increases

systolic pressure increases

diastolic pressure stays the same or decreases

How would increased SV or increased R effect this?

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15
Q

What are the three features of venous pressure?

A

Low pressure, high compliance, large volume

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16
Q

What are the features of atrial pressure?

A

low and estimated by pulmonary wedge pressure

since the measurement site is a little upstream from the atrium, it is a few mmHg higher than the actual left atrial pressure

This is important because it can be used to determine if someone has heart failure/to what extent

17
Q

What is the arterial pressure change in the following conditions:

Arteriosclerosis

Aortic Stenosis

A

Increase arterial pressure

decrease arterial pressure

18
Q

If you change resistance only and nothing else (no change in compliance) what is the result?

A

No change in pulse pressure

(not typically seen in nature)

19
Q

What makes up microcirculation?

A

arterioles with Sm. M wall

metarterioles with limited Sm. M walls

capillaries with precap. sphincters

20
Q

How does exchange occur across the capillary wall?

A

Via clefts

these clefts allow water soluble substances such as glucose, electrolytes etc, through (small in brain, large in liver/gut)

lipid soluble substances such as O2 and CO2 pass thru cell wall and larger things pass through in vesicles

21
Q

What does the Starling Equation calculate?

Know the equation

A

flow of water out of the capillary (+) or into the capillary

(-)

based on hydrostatic pressure (BP)

Osmotic pressure (pi)

Jv=Kf (Pc-Pi)-(pic-pii)

Pc-Pi is the HSP

pic-pii is the Osm. P

22
Q

What can alter hydrostatic pressure or osmotic pressure

A

edema

Pc can change by elevated venous pressure (heart failure)

Pi can change by restriced lymphatic flow or increased driving force out of capillary

pic can change by decrease in albumin (starvation, liver failure)

pii can change by restricted lymph flow or inflammation

23
Q

How much lymph is made per day?

A

about 2-3 liters per day reenters at the subclavian vein

24
Q

How can tissues “break” from central control in times where one tissue needs more perfusion than another?

A

local beds can break away from central control when local needs become greater

this does no significantly alter the TPR or other tissues will compensate by further constriction to maintain BP constant in the face of some tissues “breaking” from central control

25
Q

Describe myogenic control (reflex)

A

if the blood pressure is elevated, which would otherwise deliver more blood than necessary, arterial walls become stretched and that causes vasoconstriction

the opposite occurs when blood pressure drops (vasodilate as a result)

26
Q

Describe metabolic control.?

A

Short: High metabolism stimulates vasodilation, increasing blood flow to area in need

Long: active hyperemia is increasing interstitial concetration of metabolites such as CO2, H, K, lactate and adenosine or decrease in O2 due to increasing metabolism causes smooth muscle of arterioles, metarterioles, and pre-cap. sphincters to relax increasing flow through the area

27
Q

What is reactive hyperemia?

A

when vascular obstruction causes build-up of metabolites leading to vasodilation therefore if the obstruction is removed the area is flooded with blood

ex: sitting on your hand for a few minutes and then moving it

28
Q

What is shear (in terms of local control)

A

if a vascular bed dilates due to metabolic demand, the flow through upstream arterioles and small arteries would increase

this would increase the shear or wall friction leading to the release of NO which would cause vasodilation and augment the downstream metabolic effect

29
Q

Histamine and Bradykinin effect blood flow how?

A

arteriolar vasodilation

increases capillary porosity (Kf) allowing escape of large molecules

causes edema in response to tissue damage

30
Q

How does serotonin effect blood flow

A

vasoconstricition in response to tissue damage

31
Q

What has “mixed” effects on blood flow?

A

prostaglandin

32
Q

Describe coronary circulation

A
  • mostly under metabolic control
  • left ventricular contraction causes constriction of vasculature msot notably near the endocardial surface
  • CA blood flow is lowest during ventricular contraction
33
Q

What controls cerebral circulation?

A

mostly metabolic control

34
Q

Describe Pulmonary circulation

A
  • highest pressures of the pulmonary vascular system are found in the RV and pulmonary artery
  • the pressure in the RV varies from 24mmHg to 0-4mmHg
  • pressure changes are less in the pulmonary A. (24 to 10-16)
  • Avg pressures in the Pulmonary A. is 20mmHg
35
Q

Is resistance high or low in the pulmonary system?

A

Resistance is very low in the pulmonary system

36
Q

How is pulmonary blood flow regulated?

A

vasoconstriction (alveolar hypoxia)

little sympathetic influence

compliant arterial system, meaning that small changes in mean pressure will dilate arteries, reduce resistance and help maintain pressure low in the face of large changes in flow

37
Q

How does alpha receptors and beta receptors play a role in blood flow at rest and during f/f responses?

A

at rest-NE binds alpha receptors

flight/fight-adrenal glands secrete EPI that binds to B2 and cause vasodilation

38
Q

What is a right to left shunt?

What is a left to right shunt?

A

blood passing from system veins to systemic arteries without passing through functional lung tissue

blood passing from systemic arteries to systemic veins without passing through a capillary bed for substance exchange

CPR Exam 1 (31 decks)

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