Cardio IV Flashcards

1
Q

Describe the pattern of pressures within pulmonary and systemic circulation and how they are similar or differ from one another.

A

Systemic pressures always < pulmonary pressures

Both follow the same pattern of large oscillations (systolic to diastolic) that damp out as you move from arteries to capillaries to veins.

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2
Q

How does the difference in pulmonary vs systemic circulation pressure affect the structure of the heart?

A

Because the systemic pressure is always higher than the pulmonary pressure, the left ventricle (which feeds into the systemic circulation) is larger than the right ventricle.

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3
Q

What is hydrostatic pressure?

A

The pressure exerted by a fluid at equilibrium at a given point within the fluid due to the force of gravity.

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4
Q

What is the formula for hydrostatic pressure? Describe each variable.

A

P = rho x g x h
Where rho is the density of the fluid
g is gravitational force
h is the height of the fluid at the point of interest

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5
Q

What is the conversion between cm H2O and pascals?

A

1 cm H2O = 90 Pa

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6
Q

What is the conversion between cm H2O and mm Hg?

A

1 cm Hg = 14 cm H2O

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7
Q

What is the difference between a direct and an indirect method of blood pressure measurement?

A

A direct method involves puncturing the arteries, while an indirect method does not.

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8
Q

What was the first indirect blood pressure measurement? How did it work?

A

The mercury sphygmomanometer. It involved wrapping a cuff around the arm and pumping, which would pump a column of mercury.

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9
Q

Convert 1 mm Hg into kPa.

A

1 mm Hg = 14 mm H2O = 1.4 cm H2O = 0.13 kPa

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10
Q

How was central venous pressure/right atrial pressure originally measured?

A

Place tip of catheter into right atrium and release saline into the heart. The pressure will be measured with a manometer and will stop moving when the pressure of the saline = central venous pressure.

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11
Q

What is the typical central venous pressure/right atrial pressure?

A

5-10 cm H2O

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12
Q

What is perfusion pressure?

A

Perfusion pressure is the pressure of the blood that flows through an organ or through a vessel. It is the pressure that governs blood flow.

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13
Q

What is the formula for perfusion pressure?

A

Perfusion pressure = arterial pressure - venous pressure
However, since arterial pressure&raquo_space; venous pressure (100 mm Hg to 5 mm Hg), we ignore venous pressure.

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14
Q

What happens if there is no perfusion pressure? When might this occur?

A

If there is no perfusion pressure, there is no pressure gradient and thus no blood flow. This occurs when the individual is dead.

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15
Q

What are the two factors that affect blood flow? Write the formula expressing their relationship.

A

Flow = perfusion pressure / resistance

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16
Q

How do you measure resistance?

A

Resistance can’t be measured directly. The flow and the perfusion pressure must be measured so that we can do R = perfusion pressure / flow

17
Q

Blood flow in vessels can be described as […] flow

A

laminar or parabolic

18
Q

Explain why blood undergoes laminar or parabolic flow.

A

If you measure the velocities at the central line in the vessel, you will have a large velocity. As you move towards the walls, the velocity approaches zero. So, there is a parabolic shape to the velocities.

The blood flow can also be conceptualized as laminar because the blood can be thought of as being made up of many layers (laminae). The ones towards the center flow faster than those that reach out towards the sides because there is frictional loss of energy from the sliding of laminae over each other.

19
Q

What is Poiseuille’s law and what is the formula? State the variables.

A

Resistance = 8 v L / pi r^4
Where v = viscosity of fluid
L = length of vessel
r = radius of vessel

20
Q

For what situations is Poiseuille’s law valid?

A

In laminar/parabolic flow ONLY.

21
Q

Name the 4 major controls of vessel resistance.

A
  1. Local metabolites
  2. Innervation
  3. Hormones
  4. Endothelial control
22
Q

What is the relationship between vessel radius and resistance? What are the implications of this?

A

Radius is inversely proportional to radius ^ 4
This means that small changes in radius will have a big effect on the resistance.

23
Q

What is the formula for combined resistance for vessels or organs in series? What is the consequence on functionality?

A

R = R1 + R2, so R > R1 or R2
When you put vessels in series, you’re increasing the resistance. This is why branching is useful; if we didn’t have it, there would be much more resistance in the vessels.

24
Q

What is the formula for vessels or organs in parallel? What is the consequence on functionality?

A

1/R = 1/R1 + 1/R2, so R < R1 or R2
The combined resistance falls when you puts things in parallel, meaning that you need a smaller pressure to get flow.

25
Q

How does the pressure drop across vessels in parallel compare to the pressure down across vessels in series?

A

In parallel, the pressure drop across vessels is identical.