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HSF Block 2 > Physio - Cardio Circuitry + Hemodynamics > Flashcards

Physio - Cardio Circuitry + Hemodynamics Flashcards

1
Q

What is cardiac output?

A

Basics:

  • Cardiac output of the left heart = cardiac output of the right heart.

Right Side:

  • Pulmonary blood flow
    • Cardiac output from the right side of the heart

Left Side:

  • Systemic blood flow
    • Cardiac output from the left side of the heart
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2
Q

What are the 9 steps that explain the direction of blood flow?

A
  1. Lungs –> left atrium via the pulmonary vein
  2. Left atrium –> left ventricle via the mitral valve
  3. Left ventricle –> aorta via the aortic valve
  4. Aorta –> systemic arteries & systemic tissues (i.e., cerebral, coronary, renal, splanchnic, skeletal muscle, and skin)
  5. Tissues –> systemic veins & vena cava
  6. Vena cava (mixed venous blood) –> right atrium
  7. Right atrium –> right ventricle via the tricuspid valve
  8. Right ventricle –> pulmonary artery via the pulmonic valve
  9. Pulmonary artery –> lungs for oxygenation
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3
Q

What are the patient signs and clinical signs of Left Ventricular Failure?

A

Patient signs:

  • Cough
    • pulmonary edema
    • lung crackles, dullness on percussion
  • Difficulty sleeping
    • orthopnea/paroxymal noctunal dyspnea
  • Shortness of breath, fatigue, weakness

Clinical Signs:

  • ↑ Left Atrial Pressure (LAP)
    • measureed by pulmonary cap wedge pressure (↑PCWP)
  • Irregular or Rapid Pulse; Palpitations
    • sympathetic response
  • ECG changes
    • S3 gallop
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4
Q

What are the patient and clinical signs for Right Ventricular Failure?

A

Patient Signs:

  • Leg edema, ascites
    • back-up in the large veins, peripheral edema
  • Nocturia
    • increase venous return w/ leg elevation
  • Shortness of breath, fatigue, weakness
    • mechanical impingment on diaphragm

Clinical Signs:

  • ↑ Central Venous Pressure (CVP)
    • ↓ pulmonary capillar wedge pressure (PCWP)
  • Irregular or rapid pulse, palpatations
    • sympathetic response
  • Congestive Heart Failure
    • _​_back up of fluid in the heart

Note:

  • B/c closed system, left heart failure will eventually lead to right heart failure + vice versa
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5
Q

What is the relationship of Volume & Pressure related to

Mean Systemic Pressure?

A

Basics:

  • All forces exerted by the individual blood molecules in motion added together = make up the fluid, or blood pressure.

Mean Circulatory Filling Pressure (Mean Systemic Pressure (MSP):

  • If you stopped the heart & let pressure in CV system equalize
    • Measure fluid pressure ~7mmHg

Adding/Removing Volume:

  • (+) volume = ↑ pressure
    • Volume overload = PCWP ↑, CVP ↑
  • (-) volume = ↓ pressure
    • Hypovolemia = PCWP ↓, CVP ↓

Applying force:

  • (+) force = ↑ pressure
    • SV↑ = arterial Ps ↑

Note:

  • Volume and Pressure = directly proportional
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6
Q

How does Blood Volume distributed throughout the CV system?

A

Basics:

  • Blood volume in arteries = “Stressed”
  • Blood volume in veins = “Unstressed”

Distribution of Blood Volume:

  • Heart = 8 - 11%
  • Lungs = 10 - 12 %
  • Systemic arteries = 10 - 12 %
  • Capillaries = 4 - 5 %
  • Systemic veins = 60 - 68 %
    • ** accomodate a lot of blood!**
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7
Q

What is blood flow and how is it calculated?

A

Basics:

  • Blood Flow (Q) aka Rate
    • Amount of fluid passing per time interval
  • Blood flow depends on pressure difference!__​
    • flows DOWN a pressure gradient
  • Equation:
    • Q ~ change in P

Clinically:

  • Blood flow (Q) across the circuitry = Cardiac Output (CO)
    • CO ~ mean aortic/arterial pressure
    • Proportional average of systolic & diastolic
      • systolic = short (1/3)
      • diastolic = long (2/3)
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8
Q

How do we calculate Velocity of Blood Flow?

A

Basics:

  • Velocity is dependent on area & blood flow
    • As vessel diameter (A) ↑, blood flow (Q) ↓

Equation:

  • v = Q/A
    • Q = blood flow
    • A = cross-sectional area (πr2)

Aorta:

  • Small area + high velocity = fast delivery of blood
    • ↓ A, ↑ Q = FAST

All Capillaries:

  • High area + low velocity = slow; time for exchange
    • ↑A, ↓ Q = SLOW

Note:

  • Structure helps w/ function and efficiency
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9
Q

How do we calculate Resistance to Blood Flow?

A

Basics:

  • Blood flow is dependent on change in pressure & resistance

Equations:

  • R = change in P / Q
    • ​P = Pressure
    • R = Resistance
  • TPR = (MAP - RAP)/CO
    • MAP = Mean arterial pressure
    • RAP = Right artrial pressure
    • TPR = Total Peripheral Resistance

Systemic Distribution:

  • Aorta/large arteries/long arterial branches = 19% TPR
  • Terminal arteries & arterioles = 47% TPR
    • ​**HIGHEST amount of resistance here**
    • **Greatest pressure drop!**
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10
Q

How to calculate Organ Resistance?

A

Equation

  • R = change in P / Q
  • Organ Resistance = (P(organ artery) - P(organ vein)) / CO
    • Derived from: TPR = MAP - RAP/ CO

Clinical Relevance:

  • Cirrhotic/carcinogenic liver
    • ↑ intrahepatic R –> fluid backup –> leg edema
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11
Q

What is Poiseuille’s Law?

A

Poiseuille’s Law:

  • Resistance = INVERSELY proportional to Blood Flow

Equation:

  • R = 8nL/πr4
    • ​Derived from… R = change in P/ Q
      • Q = πr4(change in P)/(8nL)
  • n = viscosity
    • viscosity of blood ~ 3x of water
  • L = length
  • r = radius
    • ** by far the most influential!

Assumptions:

  1. Steady flow
    • non-pulsatile
  2. Uniform flow
    • long vessel w/ constant CSA
  3. Newtonian fluid
    • consetant viscosity
  4. Laminar flow
    • non-turbulent
  5. No-slip condition
    • velocity near wall = very low

Note:

  • None of these assumption are present in the body…but it nevertheless gives us a good estimation
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12
Q

How does vessel arrangement influence TPR?

A

Basics:

  • TPR depends on vessel arrangement

Series Resistance:

  • Resistance = INCREASING (additive)
  • Rtotal = Rartery + Rarterioles + Rcapillaries + Rvenules + Rvein
    • total blood flow at each level = same
      • ↑ R = ↓ Pressure (Q = P/R)

Parallel Resistance:

  • Resistance = DECREASING
  • 1/Rtotal = 1/Ra + 1Rb + … + 1/Rn
    • ​total blood flow thru each organ = fraction of total flow
  • ADDING a resistance = DECREASES Rtotal
    • ie: opening a traffic lane
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13
Q

What is the differece between Laminar Flow and Turbulent Flow?

A

Laminar Flow:

  • Quiet
  • Flow in layers, along streamlines
  • Reynolds #: NR < 2000

Turbulent Flow:

  • Noisy
  • Random 3D fluid motion
  • Reynolds #: NR > 3000

Murmurs:

  • Blowing, gurgling, whooshing, rasping sounds
  • Produced by turbulent flow thru heart valves or carotid sinus

Bruits:

  • Vascular murmurs

Clinical relevance:

  • ↑ NR (turbulent flow) can be caused by:
    • blood clot/stenotic valve
      • ↑ velocity
    • anemia
      • ↓ viscosity
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14
Q

What is Shear?

A

Intravascular:

  • Highest shear stress = at Vessel Wall
    • velocity difference btw adjacent blood layers & wall = greatest

Intervascular:

  • Highest shear stress = Arterioles & Capillaries
    • greatest ratio of wall:blood
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15
Q

How does Compliance differ in blood vessels?

A

Basics:

  • At low pressure, veins = more compliant than arteries
  • At high pressure, pressure is similar in both

Equation:

  • Cv = change in V/ change in P

At a given change in volume:

  • the higher the compliance, the smaller the pressure change
    • adding blood to veins does not add much to MSP
    • veins act as a low pressure reservoir

At a given change in pressure:

  • the lower the compliance, the less volume the vessel can hold
    • arteries do not hold much blood, but have a high pressure
    • adding blood significantly changes MSP
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16
Q

How can physiologic variation effect compliance?

A

Sympathetic activation:

  • Decreases compliance
    • most relavent for veins = will hold less blood
    • volume then shifted from “unstressed” –> “stressed”

Aging:

  • Decrease compliance
    • most relavent for arteries = will have higher pressure to hold same blood volume
    • older people have higher BP
17
Q

Elastic Recoil of Blood Vessels

A

Basics:

  • arteries expand somewhat during ventricular systole
  • portion of SV = stored in elastic wall of aorta to be moved forward in diastole
    • function of elastic fibers in TUNICA MEDIA
18
Q

Pressure in the CV System

A

Basics:

  • Pressure is highest exiting the heart
  • Pressure is lowers entering the heart

Pulsatile:

  • Cardiac output
    • low compliance of large arteries
  • High elastic recoil

Non-Pulsatile:

  • High resistance
    • arterioles
  • Frictional resistance/Filtration into tissue
    • capillaries

Note:

  • Pulmonary vasculature follows same pattern at MUCH lower pressure
19
Q

What are the two Pulsatile Arterial Pressures?

A

Systolic Pressure (Ps)

  • Ps is MAINLY function of SV & compliance
    • ↑ volume of blood pumped (SV) = ↑ pressure
  • In old people/arteriosclerosis
    • Compliance is low & Ps is high

Diastolic Pressure (Pd)

  • Pd is MAINLY a function of HR & peripheral arteriolar resistance
    • ​↑ peripheral arteriolar resistance = Pd is ↑
      • amt of blood held in arterial sys while heart is filling is increased
  • In athletes w/ low HR
    • Pd↓ b/c of more time for pressure to drop off btw fillings

Pulse Pressure:

  • Difference btw Ps & Pd

Mean Arterial Pressure (MAP or Pa):

  • MAP = Diastolic Pressure + 1/3 of Pulse Pressure
  • MAP = 1/3 Systolic pressure + 2/3 of Diastolic Pressure
20
Q

What are Non-pulsatile Venous Pressures?

A

Basics:

  • Continuous Flow = no pulse of arterial origin

Pressure Fluctuations:

  • in the main branches of the veins due to transmission of an arterial pressure pulse
    • happens when anatomical veins & arteries lie side by side
      • pronounced in great veins nearing the right heart

HSF Block 2 (24 decks)

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