Equations and Laws Flashcards
What does the Law of Laplace show?
What is the equation?
When pressure within cylinder is constant, tensioin on its walls increases with increasing radius.
T = PR T = PR/h
What is stroke work?
Equation + Units
Work done by heart to eject blood under pressure into aorta and pulmonary artery.
SW = SV x P
(ml/m^2)
What is the equation for minute ventilation + units?
MV (L/min) = Tidal Volume (L) x Breathing frequency (breaths/min)
Gas entering and leaving the lungs.
What is the equation for alveolar ventilation + units?
AV (L/min) = (TV (L) - Dead space (L)) x Breathing frequency (breaths/min)
What is transmural pressure?
Pressure inside the compartment relative to the pressure outside the compartment.
How do you calculate transmural pressure?
Ptran = Pinside - Poutside
cmH20
What is Dalton’s law and give an equation?
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)
What is Fick’s Law and give an equation?
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
What is Henry’s Law and give an equation?
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)
What is Boyle’s Law and give an equation?
At constant temp. the volume of gas is inversely proportional to the pressure of that gas.
PGas ∝ 1/VGas
kPa or mmHg
What is Charles’ Law and give an equation?
At constant pressure, the volume of a gas is proportional to the temperature of that gas.
VGas ∝ TGas (ml or L)
What is the Frank-Starling relationship?
Diastolic fibre length ∝ Ventricular contraction
This can be due to changes in number of myofilament cross bridges interacting or Ca2+ sensitivity
What is Poiseuille’s Law and give the equation?
Relatively small changes in vascular tone can produce large changes in flow.
Resistance = 8nl/πr^4 (mmHg min/ml)
What is Darcy’s Law? Give the equation.
Average pressure in a patient’s arteries during one cardiac cycle.
ΔP (mmHg) = Q x TPR
MAP = DBP + 1/3 PP
What is Cardiac Output?
Q (ml/min) = HR x SV
Amount of blood the heart pumps in 1 minute.