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Z. CV FINAL > Hemodynamics and Hemodynamic Measurements - Quiz 4 > Flashcards

Hemodynamics and Hemodynamic Measurements - Quiz 4 Flashcards

1
Q

Velocity

A

distance per unit of time

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2
Q

Velocity is ___________ related to the cross-sectional area

A

Inversely

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3
Q

Flow

A

volume per unit of time

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4
Q

How to measure Blood Flow

A

Velocity x Cross Sectional Area

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5
Q

In Ohm’s Law, what 2 factors determine blood flow through a vessel?

A

1) Difference in Pressure

2) Resistance

Flow (Q) = (PA - PV) / R

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6
Q

What is Blood Pressure

A

The force exerted by blood against the vessel wall

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7
Q

1 mmHg = ? cm-H2O

A

1 mmHg = 1.36 cm-H2O

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8
Q

What is Poiseuille’s Law?

A

Poiseuille’s Law
 Flow is directly proportional to the pressure gradient
 Flow varies directly as the fourth power of the radius
o Doubling the radius of a tube causes a 16-fold increase in flow
 Flow is inversely proportional to the viscosity of the fluid
 Flow is inversely proportional to the length of the tube

Resistance = the impediment to blood flow in a vessel and cannot be measured by any direct means

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9
Q

What is Cerebral Perfusion Pressure

A

Cerebral Perfusion Pressure = MAP - CVP or ICP (whichever higher)

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10
Q

What has greatest impact on rate of bloow flow through a vessel wall regarding Poiseuille’s Law?

A

Diameter of Blood Vessel

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11
Q

What is Resistance?

A

The impediment of blood flow in a vessel - cannot be directly measured

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12
Q

SVR Formula

A

SVR = [(MAP - CVP) / CO] X 80

Normal: 700-1600

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13
Q

PVR Formula

A

PVR = [(MPAP - PCWP) / CO] x 80

Normal: 100 - 300

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14
Q

Calculating resistance in blood vessels arranged in a series

A

Total Resistance = Sum of Resistance of Each Vessel

Rt = R1 + R2 + R3 + R4

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15
Q

Calculating blood vessel resistance in Parallel Arrangement?

A

1/Rt = 1/R1 + 1/R2 + 1/R3

Parallel Arrangement allows for Local Blood Flow Regulation

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16
Q

What happens to total resistance if you added another blood vessel in a parallel arrangement?

A

Total resistance would decreases - another channel for blood to flow through

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17
Q

What is Laminar Flow

A

Fluid particles following moving in smooth paths in layers in a parallel

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18
Q

What is Turbulent flow?

A

Turbulent flow occurs when it fluids make sharp turn or passes over rough surface, becoming disorderly.

Blood flows crosswise in vessel and form local eddies, increasing flow resistance due to friction.

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19
Q

Formula used to predict laminar vs turbulent flow

A

Reynold’s Number (NR)

NR = pDv / n

p = density
D = tube diameter
v = velocity
n = viscosity
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20
Q

Relationship of Hematocrit to Blood Viscosity?

A

Increasing Hematocrit increases Viscosity

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21
Q

Why does an increase in Blood Pressure cause a much greater increase in Blood Flow

A

Autoregulation. It is the intrinsic ability of an organ to maintain a constant blood flow despite changes in perfusion pressure.

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22
Q

What is the mechanism that drives blood flow?

A

The difference in total energy between two points

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23
Q

What are the three primary factors that determine blood flow resistance in a single vessel?

A
  1. Vessel Diameter - most important
  2. Vessel Length
  3. Viscosity of Blood
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24
Q

Vessel resistance is ______ proportional to vessel length and blood viscosity

A

Directly Proportional

25
Q

Vessel Resistance is _______ proportional to the radius to the fourth power

A

Inversely proportional

26
Q

How does pulsatility effect flow resistance?

A

Increases flow resistance

27
Q

Cororany Perfusion Pressure =

A

Diastolic Pressure - LVEDP

28
Q

NR < 2000 = ?

NR: 2000-3000 = ?

NR > 3000 = ?

A

NR < 2000 = usually laminar

NR: 2000-3000 = variable

NR > 3000 = usually turbulent

29
Q

For non-Newtonian fluids, like blood, a decrease in flow _____ viscosity

A

Increases viscosity

30
Q

What is the most important monitor in the OR?

A

Eyes, Hands, and Ears of the Anesthetist

31
Q

Return-To-Flow Techniques for measuring BP (3)

A

Palpation

Pulse Oximeter (Plethysmographic Waveform)

Arterial Catheter

32
Q

Insertion Sites for Art Lines (6)

A
  1. Radial
  2. Brachial
  3. Ulnar
  4. Axillary
  5. Femoral
  6. Dorsalis Pedis
33
Q

What happens to pulse pressure in the leg relative to the proximal aorta?

A

SBP rises and DBP falls, increasing pulse pressure

d/t

vessel branching and decreased arterial compliance

34
Q

What is damping in an arterial line tracing?

A

The transducer is exposed to a high signal from the pressure bag by flushing, causing transducer to vibrate.

Damping is the speed at which the vibration stops and returns to normal transduction.

35
Q

What is an overdamped art line?

A

Underestimation of SBP & overestimation of DBP (same MAP) due to frictional forces impeding wave form - wide, slurred wave

EX: Air bubbles, kink, stretchy tubing, low pressure bag, clots

36
Q

What is an underdamped art line

A

Overestimation of SBP and underestimation of DBP (same MAP) due to reverberation in the tubing - Peak, narrow waves

EX: Long stiff tube, increased vascular resistance

37
Q

3 Waves of CVP

A

A-Wave: Right Atrial Contraction (P-Wave on ECG)

C-Wave: Cusp of triscuspid valve - Right Ventricle Contraction (end of QRS)

V-Wave: Right Atrial Filling hitting triscuspid valve (After t-wave on ECG)

38
Q

What does a huge V-Wave on a CVP tracing suggest?

A

Triscuspid Regurgitation

39
Q

What are the waveforms seen when inserting a Swan-Ganz

A
  1. Right Ventricular Pressure
  2. Pulmonary Artery Pressure
  3. Wedge Pressure
40
Q

What info can be Directly gathered from a Swan? (6)

A
  1. CVP
  2. Right Side Heart Pressures
  3. Pulmonary Arterial Pressure (PAP)
  4. Pulmonary Capillary Occlusion Pressure/Wedge Pressure
  5. Cardiac Output
  6. Mix Venous Oxyhemoglobin Saturation (SvO2)
41
Q

What info can be Indirectly gathered by a Swan? (8)

A
  1. SVR
  2. PVR
  3. CI
  4. SVI
  5. Left Ventricular Stroke Work Index (LVSWI)
  6. RVSWI
  7. Oxygen Delivery (DO2)
  8. Oxygen Uptake (VO2)
42
Q

Steps to inflating wedge?

A

Don’t inflate wedge > 15 seconds

Don’t Inflate with more than 1.5 mL of air

43
Q

Steps to Zeroing Tranducer (4)

A
  1. Establish standard reference value, ambient atm. pressure = 0 mmHg
  2. Place transducer at vertical height relative to patient’s position
    • upper most blood level in measured chamber
    • 5 cm below left sternal border at the 4th intercostal space
44
Q

Fick’s Principle

A

Cardiac Output =

O2 per minute absorbed by lungs (ml/min) / Arteriovenous O2 difference (mL/L blood)

45
Q

Thermodilution Method for measure Cardiac Output

A

Inject room temp solution into right atrium, and measuring temperature over time at the tip of the catheter. The change over time is expressed as the area under the curve and is used to calculate cardiac output.

46
Q

What is Pulsus Paradoxus?

A

A drop in BP > 10 mmHg on inspiration

The Reverse happens with Positive-Pressure Ventilation - treat with fluid

47
Q

What is the Natural Resonant Freqency in an art line?

A

How fast the system vibrates in response to a pressure signal

48
Q

What is the x-descent of the CVP tracing?

A

Downward movement of Right Ventricle as it contracts

(Happens before T-Wave)

49
Q

What is the y-descent on a CVP tracing?

A

Pulse pressure decrease due to opening of tricuspid valve

(Happens before P-wave)

50
Q

What does a loss of y-descent suggest?

A

Tamponade - restriction to RV filling

51
Q

Large area under thermodilution curve = ?

A

Low Cardiac Output

Vice Versa

52
Q

What is the most widely used method to determine Cardiac Output?

A

Thermodilution

53
Q

What is the most common problem obtaining accurate Cardiac Output measurement?

A

Improper Injectate Adminstration

54
Q

How to else to measure Cardiac Output other than Thermodilution?

A
  • Ultrasound methods - Esophageal Doppler
  • Bioimpedance
  • Partial CO2 Rebreathing Fick method
  • Lithium Dilution
  • Pulse Countour
55
Q

Poiseuille’s Equation

A

Flow inversely related : (radius4 x Change in Pressure) / (Viscosity x Length of Vessel)

56
Q

Flow is ______ proportional to the Pressure Gradient

A

Directly Proportional

57
Q

Flow is ________ proportional to Length of the Tube

A

Inversely Proportional

58
Q

Pulmonary Artery Catheter Waves

A
59
Q

What is Poiseuille’s Law?

A

the velocity of the steady flow of a fluid through a narrow tube (as a blood vessel or a catheter) varies directly as the pressure and the fourth power of the radius of the tube and inversely as the length of the tube and the coefficient of viscosity

Z. CV FINAL (11 decks)

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