Hemodynamics and Hemodynamic Measurements - Quiz 4 Flashcards

(55 cards)

1
Q

How to measure Blood Flow

A

Velocity x Cross Sectional Area

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2
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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3
Q

What is Blood Pressure

A

The force exerted by blood against the vessel wall

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4
Q

1 mmHg = ? cm-H2O

A

1 mmHg = 1.36 cm-H2O

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5
Q

What is Cerebral Perfusion Pressure

A

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

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6
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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7
Q

What is Resistance

A

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

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8
Q

SVR Formula

A

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

Normal: 700-1600

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9
Q

PVR Formula

A

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

Normal: 100 - 300

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10
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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11
Q

Calculating blood vessel resistance in Parallel Arrangement?

A

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

Paralell Arrangement allows for Local Blood Flow Regulation

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12
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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13
Q

What is Laminar Flow

A

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

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14
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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15
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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16
Q

Relationship of Hematocrit to Blood Viscosity?

A

Increasing Hematocrit increases Viscosity

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17
Q

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

A

As opposed to the arterial blood flow, an increase in venous blood pressure increases flow because the vessels become more rounded and lowers resistance –> increases venous return.

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18
Q

What is the mechanism that drives blood flow?

A

The difference in total energy between two points

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19
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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20
Q

Vessel resistance is ______ proportional to vessel length and blood viscosity

A

Directly Proportional

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21
Q

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

A

Inversely proportional

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22
Q

What is the basis of Bernoulli’s Principle?

A

Kinetic Energy and Pressure Energy can be interconverted so that total energy remains the same.

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23
Q

How does pulsatility effect flow resistance?

A

Increases flow resistance

24
Q

Cororany Perfusion Pressure =

A

Diastolic Pressure - LVEDP

25
NR \< 2000 = ? NR: 2000-3000 = ? NR \> 3000 = ?
NR \< 2000 = **usually laminar** NR: 2000-3000 = **variable** NR \> 3000 = **usually turbulent**
26
For non-Newtonian fluids, like blood, a decrease in flow _____ viscosity
Increases viscosity
27
What is the most important monitor in the OR?
Eyes, Hands, and Ears of the Anesthetist
28
Return-To-Flow Techniques for measuring BP
Palpation Pulse Oximeter (Plethysmographic Waveform) Arterial Catheter
29
Insertion Sites for Art Lines
Radial Brachial Ulnar Axillary Femoral Dorsalis Pedis
30
What happens to pulse pressure in the leg relative to the proximal aorta?
SBP rises and DBP falls, increasing pulse pressure d/t vessel branching and decreased arterial compliance
31
What is damping in an arterial line tracing?
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.
32
What is an overdamped art line?
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
33
What is an underdamped art line
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
34
3 Waves of CVP
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)
35
What does a huge V-Wave on a CVP tracing suggest?
Triscuspid Regurgitation
36
What are the waveforms seen when inserting a Swan-Ganz
1. Right Ventricular Pressure 2. Pulmonary Artery Pressure 3. Wedge Pressure
37
What info can be Directly gathered from a Swan?
CVP Right Side Heart Pressures Pulmonary Arterial Pressure Pulmonary Capillary Occulsion Pressure/Wedge Pressure Cardiac Output Mix Venous Oxyhemoglobin Saturation (SvO2)
38
What info can be Indirectly gathered by a Swan?
SVR PVR CI SVI Left Ventricular Stroke Work Index (LVSWI) RVSWI Oxygen Delivery (DO2) Oxygen Uptake (VO2)
39
Steps to inflating wedge?
??? Dont inflate wedge \> 15 seonds Dont Inflate with more than 1.5 mL of air
40
Steps to Zeroing Tranducer
1. Establish standard reference value, ambien atm. pressure = 0 mmHg 2. Place transducer at verticle height relative to patient's position * upper most blood level in measured chamber * 5 cm below left sternal border at 4 ICS
41
Fick's Principle
Cardiac Output = O2 per minute absorbed by lungs (ml/min) / Arteriovenous O2 difference (mL/L blood)
42
Thermodilution Method for measure Cardiac Output
Inject room temp solution, and measuring temperature over time.
43
What is Pulsus Paradoxus?
A drop in BP \> 10 mmHg on inspiration The Reverse happens with Positive-Pressure Ventilation - treat with fluid
44
What is the Natural Resonant Freqency in an art line?
How fast the system vibrates in response to a pressure signal
45
What is the x-descent of the CVP tracing?
Downward movement of Right Ventricle as it contracts (Happens before T-Wave)
46
What is the y-descent on a CVP tracing?
Pulse pressure decrease due to opening of tricuspid valve (Happens before P-wave)
47
What does a loss of y-descent suggest?
Tamponade - restriction to RV filling
48
Large area under thermodilution curve = ?
Low Cardiac Output Vice Versa
49
What is the most widely used method to determine Cardiac Output?
Thermodilution
50
What is the most common problem obtaining accurate Cardiac Output measurement?
Improper Injectate Adminstration
51
How to else to measure Cardiac Output other than Thermodilution?
* Ultrasound methods - Esophageal Doppler * Bioimpedance * Partial CO2 Rebreathing Fick method * Lithium Dilution * Pulse Countour
52
Poiseuille's Equation
Flow inversely related : (radius4 x Change in Pressure) / (Viscosity x Length of Vessel)
53
Flow is ______ proportional to the Pressure Gradient
Directly Proportional
54
Flow is ________ proportional to Length of the Tube
Inversely Proportional
55
Pulmonary Artery Catheter Waves