G3v: Describe and explain cardiac output curves, vascular function curves and their correlation

Vascular function curves (VR vs RAP) & Cardiac function curves (CO vs RAP) are used to demonstrate how systemic vascular function affects systemic blood flow

Vascular Function Curve

Vascular Fn Curve
  • Affected by 3 factors:

Factors

Normally

MSFP

7mmHg

RAP

0mmHg

Resistance to VR

1.4mmHg

  • These normal values give VR = 5L/min → gives CO = 5L/min

Cardiac Function Curve

  • According to F – S → ↑RAP = ↑CO
  • Cardiac function curve is similar to the other F – S curve (SV vs LVEDP)
  • Cardiac function curves are a family, there is no single curve → the change depending on the dependent variables

CO = HR x SV (preL/C/afterL)

∴Dependent variables = HR, preL, afterL, C

NB: RAP = THE INDEPENDENT VARIABLE

  • Normal cardiac function curve: CO = 5L/min & RAP 0mmHg
  • ↑HR, ↑preL, ↑C, ↓afterL → ↑CO
    • ∴cardiac function curve shifts up & LEFT

Interaction: Of Vascular Function Curves & Cardiac Function Curves

  • Superimposing the 2 curves → KA COUPLING between the Heart & peripheral circulation
  • The point where 2 curves cross → KA EQUILIBRIUM POINT, which defines at what CO & RAP the cardiovascular system is operating