1 Foundations of Hemodynamics Free Online FlashCards

What does hemodynamics study?

Hemodynamics is the study of blood flow and the forces that move blood through the heart and blood vessels.

What is the pulmonary circulation?

The right ventricle pumps blood through the lungs to take up oxygen and back to the left heart. This circuit normally has lower pressure and resistance.

How is cardiac output calculated?

Cardiac output is heart rate multiplied by stroke volume: $\mathrm{CO}=\mathrm{HR}\times\mathrm{SV}$.

How is stroke volume calculated?

Stroke volume is end-diastolic volume minus end-systolic volume: $\mathrm{SV}=\mathrm{EDV}-\mathrm{ESV}$.

How are systemic flow, MAP, CVP, and SVR related?

Systemic flow is approximated by $\mathrm{CO}\approx\frac{\mathrm{MAP}-\mathrm{CVP}}{\mathrm{SVR}}$. When CVP is small relative to MAP, this is often simplified to $\mathrm{MAP}\approx\mathrm{CO}\times\mathrm{SVR}$.

How does vessel radius affect resistance?

Narrowing small arteries and arterioles increases resistance; widening them decreases it. Even modest diameter changes can substantially affect flow and pressure.

What do systolic and diastolic blood pressure represent?

Systolic blood pressure is arterial pressure during ventricular contraction; diastolic blood pressure is arterial pressure during ventricular relaxation.

What is preload, and how can it affect stroke volume?

Preload is ventricular muscle stretch at the end of filling. Within the heart's functional range, greater filling can stretch fibers and strengthen contraction, increasing stroke volume; this is the Frank–Starling mechanism.

What is the systemic circulation?

The left ventricle pumps blood to the body's tissues; blood returns through the veins to the right heart. This is normally a higher-pressure circuit.

How do right and left ventricular outputs compare in a steady state?

In a steady state, the right and left ventricles pump approximately the same blood volume over time.

What does mean arterial pressure represent?

Mean arterial pressure is the average arterial pressure over one cardiac cycle.

How can MAP be estimated from systolic and diastolic pressure?

At a typical heart rate, $\mathrm{MAP}\approx\mathrm{DBP}+\frac{1}{3}(\mathrm{SBP}-\mathrm{DBP})$. This estimate is less reliable when heart rate or systolic duration is unusual.