Cardiac Physiology 3 Flashcards
Equation for flow
Q=V/t (Flow=volume/time)
Equation relating velocity and flow
Velocity=flow/area, v=Q/A
Units of flow
mL/min or L/min
Formula for hydrostatic pressure
P=pxgxh (Where P=pressure in mmHg, p=density, g=gravitational constant, h=height)
What is the potential energy of a fluid?
Hydrostatic
What is the kinetic energy of a fluid?
Hydrodynamic
How does the pressure change in a smaller vessel compared to a larger vessel?
Total pressure remains the same but hydrostatic pressure decreases in the smaller vessel. Velocity is proportional to dynamic pressure.
Poiseuille’s Law equation for flow
Q= (Pi-P0)r^4/8nl where Pi-Po is the pressure difference, n=viscosity, l=length, r=radius
What is the equation for the sum of resistance in series?
Rt=R1+R2+R3…
What is the equation for the sum of resistance in parallel?
1/Rt=1/R1+1/R2+1/R3…
What happens to the resistance against blood between aorta to arterioles?
It rises because the radius drops and the subdivisions are not enough to increase the cross-sectional area.
What happens to the resistance against blood between arterioles and the capillaries?
It drops because the subdivision into so many capillaries to increase the total cross-sectional area overwhelms the decrease in radius.
Equation for Reynold’s number
Nr=pDv/μ where Nr=Reynold’s number, p=density, D=diameter, v=velocity, μ or n=viscosity
What is the value of Reynold’s number for laminar flow?
2000 or less
Definition of laminar fluid flow
Velocity of flow near the surface of the cylinder is zero and maximal in the center of the cylinder. Most effective and requires least energy and less work required to move the fluid vs turbulent flow.
How does anemia affect the viscosity and flow of the blood?
Reduces viscosity which increases turbulence. May create a murmur if passing through narrowed vessel or valve.
What ar Korotkoff sounds?
Pulse heard during BP measurement. Due to turbulent flow in brachial artery from artificial narrowing of the BP cuff.
What is the difference between a compliant and rigid aorta in systole and diastole?
Aorta stretches in systole and accommodates more volume with less changes in pressure in a compliant system and shrinks in diastole. In a rigid system it doesn’t move. A compliant system allows more continuous blood flow.
How does rigidity of the aorta affect O2 consumption?
More rigidity means more O2 consumption, directly proportional to stroke volume.
Pressure volume relationship in the aorta compared at different ages (graph)
Young aortas are capable of accommodating larger volumes with smaller increments in perssure and are more compliant. dV/dP is the compliance of the vessel and decreases with age.

Equation for elastic modulus/elastance
Ep=ΔP/(Da/Db) where Ep=elastic modulus, Da=max change in aortic diameter, Db=mean aortic diameter. Da/Db=ΔV
How does elastance relate to compliance?
They are reciprocals.
Elastic modulus definition
Measure of rigidity, measured by change in pressure vs fractional change in aortic diameter or another compliant vessel. Another way of looking at distensibility in a vessel.
Ohm’s law equation
Q=P/R, Qh=cardiac output, Qr=peripheral outflow, R=peripheral resistance.


