Equations To Know Flashcards

0
Q

Compliance

A

Change in EDV/change in EDP

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1
Q

The law of Laplace?

A

Wall tension = pressure X radius/ 2 X wall thickness

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2
Q

What does negative pleural pressure do to cardiac output and ventricular emptying?

A

It will increase cardiac output by increasing preload

It will impede ventricular emptying by opposing the inward contraction of the ventricle

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3
Q

What is pulsus paradoxus?

A

When bp drops greater than 15 mmHg during inspiration. Means that the pleural pressure is pulling the ventricle outward when it should be going inward

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4
Q

What does positive pleural pressure do to ventricular emptying?

A

Enhances it because it facilitates the inward movement of the ventricle

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5
Q

What is vascular impedance?

A

It is the force that opposes pulsatile flow

Expressed in the proximal arteries such as the aorta

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6
Q

What is the principal afterload source of the LV.

A

Vascular impedance in the ascending aorta

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7
Q

What is the principal afterload force in the right ventricle?

A

The pulmonary arteries

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8
Q

What is vascular resistance?

A

The force that opposes steady flow

Expressed in the small terminal vessels

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9
Q

What is the equation for vascular resistance?

A

R= Pin-Pout/ Q

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10
Q

What is the equation for SVR?

A

SVR = MAP - RAP/ CO

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11
Q

What is the equation for pulmonary vascular resistance?

A

PulmVR= PAP - LAP/ CO

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12
Q

What is the Hagen-Poiseuille equation?

A

Q = change in pressure X (pi r4/8ul)

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13
Q

What does the Hagen-Poiseuille equation represent?

A

Steady flow through small rigid tubes

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14
Q

What is the resistance equation derived from the Hagen-Poiseuille equation?

A

R = 8ul/pi r4

This shows that radius is the single most important factor in determine resistance to steady flow in the peripheral circulation

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15
Q

What is the principal determination of the viscosity of blood?

A

The concentration of erythrocytes (hematocrit)

16
Q

What is shear thinning?

A

The velocity of blood flow increases through small vessels causing an increase in plasma volume and decrease in blood viscosity

17
Q

What is the relationship between blood viscosity and cardiac output?

A

Inverse - as blood viscosity decreases, cardiac output increases (disproportionately)

18
Q

Why will cardiac output increases disproportionately?

A

Because as the flow rate increases as the viscosity drops, the viscosity gets even lower in response to the hemodilution

19
Q

What is the equation for SO2?

A

Oxygenated Hb/total Hb

20
Q

What is the equation for SvO2?

A

1- VO2/DO2

21
Q

What is the equation for VO2?

A

CO X (CaO2-CvO2) X 10

22
Q

What is the equation for CaO2?

A

1.34 X Hgb X SaO2

23
Q

What is the equation for MAP.

A

map = CO X SVR/80 - CVP

24
Q

What is the equation for calculating the amount of bicarbonate needing to normalize the ph?

A

0.2 X patients weight X base excess