Equations and Laws Flashcards

1
Q

What does the Law of Laplace show?

What is the equation?

A

When pressure within cylinder is constant, tensioin on its walls increases with increasing radius.

T = PR 
T = PR/h
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2
Q

What is stroke work?

Equation + Units

A

Work done by heart to eject blood under pressure into aorta and pulmonary artery.

SW = SV x P
(ml/m^2)

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3
Q

What is the equation for minute ventilation + units?

A

MV (L/min) = Tidal Volume (L) x Breathing frequency (breaths/min)

Gas entering and leaving the lungs.

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4
Q

What is the equation for alveolar ventilation + units?

A

AV (L/min) = (TV (L) - Dead space (L)) x Breathing frequency (breaths/min)

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5
Q

What is transmural pressure?

A

Pressure inside the compartment relative to the pressure outside the compartment.

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6
Q

How do you calculate transmural pressure?

A

Ptran = Pinside - Poutside

cmH20

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7
Q

What is Dalton’s law and give an equation?

A

Pressure of gas mixture is equal to the sum of the partial pressures of gases in that mixture.

PGasMixture = PGas1 + PGas2 +…+ PGasn (kPa or mmHg)

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8
Q

What is Fick’s Law and give an equation?

A

Molecules diffuse from high to low concentration gradient at rate proportional to concentration graident, exchange SA and diffusion capacity of gas and inversely proportional to thickness of exchange surface.

VGas = (A/T) x D x (P1- P2) ml or L

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9
Q

What is Henry’s Law and give an equation?

A

At constant temp. the amount of gas that dissolves in given time and volume of liquid is directly proportional to partial pressure of gas in equilibrium with liquid.

CDGas = aGas x PGas (ml)

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10
Q

What is Boyle’s Law and give an equation?

A

At constant temp. the volume of gas is inversely proportional to the pressure of that gas.

PGas ∝ 1/VGas
kPa or mmHg

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11
Q

What is Charles’ Law and give an equation?

A

At constant pressure, the volume of a gas is proportional to the temperature of that gas.

VGas ∝ TGas (ml or L)

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12
Q

What is the Frank-Starling relationship?

A

Diastolic fibre length ∝ Ventricular contraction

This can be due to changes in number of myofilament cross bridges interacting or Ca2+ sensitivity

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13
Q

What is Poiseuille’s Law and give the equation?

A

Relatively small changes in vascular tone can produce large changes in flow.

Resistance = 8nl/πr^4 (mmHg min/ml)

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14
Q

What is Darcy’s Law? Give the equation.

A

Average pressure in a patient’s arteries during one cardiac cycle.

ΔP (mmHg) = Q x TPR
MAP = DBP + 1/3 PP

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15
Q

What is Cardiac Output?

A

Q (ml/min) = HR x SV

Amount of blood the heart pumps in 1 minute.

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16
Q

How can you calculate pulse pressure?

A

PP (mmHg) = SBP - DBP

17
Q

What is compliance and how can you calculate it?

A

Tendency to distort under pressure.

ΔV/ΔP (μm/mmHg)

18
Q

What is elastance and how can you calculate it?

A

Tendency to recoil to its original volume.

ΔP/ΔV (mmHg/μm)

19
Q

Define flow rate.

What is the equation for it?

A

Volume of blood passing through a vessel per unit time.

Q = ΔP/R (mmHg/min)