Control of cardiac output and hemodynamic measurements

what is the formula for cardiac output

CO = SV x HR

what factors determine stroke volume

preload, afterload, contractility

what is preload

increased venous return stretches ventricular fibers, increases end-diastolic volume, increases force of contraction and SV

what is afterload

ventricular outflow resistance, affected by MAP, MPAP, PVR, SVR, blood pressure, and vessel diameter

what is contractility and ejection fraction

heart’s response to preload and afterload changes, EF = 60% edv, exercise can increase EF to 90%

what are inotropic factors

factors that affect contraction force

what vascular factors affect CO

venous return, blood volume, vascular resistance, arteriolar resistance, size of vascular space

what is the role of venous return

incoming venous flow dictates how much the heart must pump, thus venous return dictates cardiac output

what is the coupling of the heart and vasculature

pressure gradient between systemic capillaries and RAP, venous return and CO superimposed, changes in contractility, blood volume, and afterload affect CO

what happens with increased contractility

decreased RAP, increased venous return gradient, increased CO

what happens with increased blood volume

increased pressure, increased CO

what happens with increased peripheral arteriolar resistance

increased afterload, increased end-systolic volume, increased preload

what occurs in acute uncompensated heart failure

sudden loss of contractility, CO compromised

what is a pulmonary artery catheter

a catheter inserted percutaneously via IJ, subclavian, femoral, basilic, or cubital vein with ports connected to transducers to measure hemodynamics

what does the proximal port of a PAC measure

RA and RV preload

what does the distal port of a PAC measure

pulmonary artery pressure and PCWP, an indicator of LV filling

how much is the PAC balloon inflated

1.5 ml

why are pressure waveforms important in PAC insertion

aid in catheter placement

what is normal PCWP

6-12 mmHg

what PCWP indicates early pulmonary edema

> 18 mmHg

what PCWP indicates obvious pulmonary edema

> 25 mmHg

what does PCWP reflect regarding LV

LV preload, LAP, LVEDP, LVEDV, left ventricular end-diastolic pressure and volume