Cardiac Formulas Flashcards
Cardiac Output and Average for Adults
HR x SV
Ave = 5.25 L/min
Stroke Volume
EDV - ESV
Velocity of Blood Flow Related to Volume and Cross Sectional Area
V = Q/A
V = Velocity of BF (cm/sec)
Qdot = volume flow (ml/sec)
A= cross sectional area (cm2)
Reynolds Number
What is it for and what is the critical value?
NR= pdV/n
p = density of blood
d = diameter of BV
V = velocity of BF
n = viscosity of blood
The value will determine if blood flow is turbulent or laminar. Anything over 1160 is considered turbulent.
Blood Flow related to Blood Pressure and Resistance
Qdot = triangleP/R
Qdot = flow (ml/min)
triangleP = pp. diff (mmHg) (Gradient)
R = resistance (mmHg/ml/mm)
Poiseuille Equation
What is the biggest take away?
R = 8n l/πr4
R = resistance
n = viscosity of blood
l = length of BV
πr4= cross sectional area of BV
Resistance is inversely proportional to the 4th power of the cross sectional area.
i.e. increase of diameter by 16 causes decrease of resistance by 2.
Types of Resistance
Series = Rtotal = Rartery + Rarteriole + Rcap + Rvenule + Rvein
Parallel = 1/Rtotal = 1/R1 + 1/R2 + 1/R3 + 1/R4 + 1/R5
E.g. the braches off the aorta, to ensure there is no pressure loss between major distributing arteries.
Laplaces Law
T = pr
T = tension
p = pressure
r = radius
Vascular Distensibility
Vas Dis =
increase in volume/(increased pp x original volume)
Vascular Compliance
What does it express?
C = V/P
C = compliance (mmHg/ml)
V = volume (ml)
P = pressure (mmHg)
The volume of blood a vessel can hold at a specific pressure.
Frank Starlings Law of the Heart
Provides a relationship between stroke volume and end diastolic pressure. The law states that the stroke volume of the heart increases if the volume (thus pressure) in the ventricles is also increased, assuming all other factors are unchanged.
Calculating MAP when Give SBP/DBP
MAP = (SBP + 2DBP)/3
