Cardio physiology equations

Question 1

What determines blood flow velocity?

Answer 1

V = Q/A

V = velocity (cm/sec)
Q = Flow rate (mL/sec)
A = Area (cm^2)

Question 2

What is the equation for blood flow?

Answer 2

Q = Pressure difference/ Resistence

Q = blood flow.

Question 3

What determines the resistance to blood flow in a vessel (Poiseuille equation)?

Answer 3

R = 8nl/(pi)r^4

R = resistance
n = viscosity
l = length of vessel
r^4 = radius to the 4th power

Question 4

What is the significance of Reynold’s number?

Answer 4

Reynold’s number (Nr) predicts whether blood flow will be turbulent or laminar. Nr less than 2000 will be laminar flow, Nr greater than 2000 is likely turbulent, and Nr greater than 3000 is always turbulent.

Question 5

What is the equation for Reynold’s number?

Answer 5

Nr = pdv/n

Nr = Reynold's number
p = density of blood
d = diameter of vessel
v = velocity of blood
n = viscosity of blood

Question 6

What is the equation for the capcitance or compliance of a vessel?

Answer 6

C = V/P

C = capacitance or compliance
V = volume
P = pressure

Question 7

How is stroke volume determined?

Answer 7

SV = EDV - ESV

SV = stroke volume
EDV = end diastolic volume
ESV = end systolic volume

Question 8

How is the ejection fraction determined?

Answer 8

Ej fraction = SV/EDV

SV = stroke volume
EDV = end diastolic volume

Question 9

What is the law of Laplace?

Answer 9

P = 2HT/r

P = pressure
H = thickness
T = tension
r = radius

Question 10

What is the relationship between tension pressure and radius?

Answer 10

T = P x r

T = tension
P = pressure
r = radius

Question 11

How is cardiac output determined?

Answer 11

CO = HR x TPR

CO = Cardiac output
HR = heart rate
TPR = total peripheral resistance

Question 12

What determines mean arterial pressure?

Answer 12

MAP = CO x TPR

MAP = mean arterial pressure
CO = Cardiac output
TPR = total peripheral resistance