Cardio Equations

Question 1

velocity of blood flow in a given vessel

Answer 1

v=Q/A. Velocity equals output over cross-sectional area

Question 2

Ohm’s law: cadiac output

Answer 2

Q=deltaP/R. Output equals change in pressure over resistance

Question 3

Law of Laplace: wall stress

Answer 3

T=Pr/2H. Wall stress equals pressure time radius over two times wall thickness

Question 4

Poiseuille’s: resistance to flow

Answer 4

R=8nl/pi*r^4. Resistance equals eight times viscosity times vessel length over pi times radius to the fourth.

Question 5

calculation for caridac output

Answer 5

CO=(MAP-RAP)/TPR. Output equals mean arterial pressure minus right atrial pressure over total peripheral resistance

Question 6

calculate mean arterial pressure

Answer 6

MAP=(SBP+2DBP)/3=DBP+1/3PP. Mean arterial pressure equals systolic plus two times diastolic over three, or diastole plus one-third of peripheral pressure.

Question 7

calculate oxygen consumption

Answer 7

CO=(O2consumed)/(O2PA-O2PV). Assume consumption is 250 mL/min, so output equals 250 over pulmonary artery oxygen content minus pulmonary vein oxygen content

Question 8

convert mmHg min/L to dynes

Answer 8

multiply by 80

Question 9

Normal TPR

Answer 9

700-1600 dynes, 9-20 mmHg min/L

Question 10

Normal O2 consumption

Answer 10

250 mL/min

Question 11

PVR

Answer 11

PVR=(MPAP-PCWP)/CO

Question 12

Stroke Volume

Answer 12

SV=EDV-ESV
Stroke volume equals end-diastolic volume minus end-systolic volume

Question 13

ejection fraction

Answer 13

EF=SV/EDV

ejection fraction equals stroke volume over end diastolic volume

Question 14

cardiac output from stroke volume

Answer 14

CO=HR*SV

cardiac output equals heart rate times stroke volume

Question 15

stroke volume from PV loop

Answer 15

distance between ESV (left) and EDV (right)

Question 16

Compliance

Answer 16

C=V/P

change in volume for a relative change in pressure
corresponds inversely to EDPVR

Question 17

Slope of ESPVR corresponds to

Answer 17

contractility

Question 18

the load on the ventricle after diastole

Answer 18

preload

Question 19

important measures of preload

Answer 19

end-diastolic pressure, end-diastolic volume

Question 20

load on the ventricle after ejection, determined by arterial system

Answer 20

afterload

Question 21

important measures of afterload

Answer 21

aortic pressure, total peripheral resistance