Hemodynamics Flashcards
What is the Poiseuille’s Law equation?
Q=(P1-P0)/R
Q=Flow of fluid through a rigid tube
P1=Upstream Pressure
P0=Downstream Pressure
R=Resistance
How is resistance calculated?
8*L*n/πr4
L=Length of the tube
n=Viscosity of the fluid
r=radius of the tube
How would changes in viscosity present?
A patient with polycythemia or who lives at high altitude would have more viscous blood; an anemic patient would have thinner blood
Which variable is the most important in determining resistance?
The radius of the tube, which can be affected by vasoconstrictors and vasodilators
How can one calculate the blood flow in a given organ?
Organ blood flow = Mean Arterial Pressure/Organ vascular resistance
What are the approximate normal values of heart rate, stroke volume, cardiac output, and mean arterial pressure for a 70 kg male?
HR = 55-80 beats/min
SV = 70-80 mL/beat
CO=4.0-5.0 L/min
MAP = 85-95 mm Hg
How is a resistance in series calculated and what is the relationship between the total resistance and the individual components?
Total = R1+R2+R3+R4
The Total resistance is greater than each individual part
How is a resistance in parallel calculated and what is the relationship between the total resistance and the individual components?
1/Total=1/R1+1/R2+1/R3
The total resistance is less than the individual resistances; most of the body is set up this way, so total peripheral resistance is less than resistance within one organ
How is laminar flow defined?
streamlined, regular, orderly flow of parallel layers of fluid through
a tube or blood vessel
Where might turbulent flow occur and how would it manifest acoustically?
-Areas with high fluid velocities (aorta and pulmonary artery)
- Arterial branch points
- Distal to a stenosis
-Stenotic heart vessels have murmurs; stenotic vessels have bruits
