Hemodynamics I and II Flashcards
What’s the order of blood flow in the CVS, starting from the Pulmonary veins?
Pulmonary vv >> LA >> LV >> Aorta >> arterioles >> capillaries >> venules >> veins >> SVC/IVC >> RA >> RV>> Pulmonary aa >> arterioles >> capillaries >> venules >> veins >> Pulmonary vv
What is the conduction pathway from the SA node throughout the heart?
What is the point of least oxygenated blood in vascular flow?
Pulmonary arteries
Which vessels can be described as resistance/capacitance/conduit/exchange vessels? Why?
Arterioles: resistance vessels; they have a smaller diameter, thus less room through which blood can flow
Veins: capacitance vessels; blood storage (b/c more room since they don’t have that huge elastin layer that arteries have, have valves to direct blood flow
Arteries/Aorta: conduit vessels; they can accomodate flow at high pressure thanks to their elasticity (contract in systole and recoil during diastole)
Capillaries: exchange vessels; have single endothelial layer and don’t have any pulsatile flow
Define mean arterial pressure. How do you calculate it?
Mean Arterial Pressure: pressure in your arteries during one cardiac cycle
Formula: MAP = 1/3 systolic + 2/3 diastolic blood pressure
Define cardiac output. How do you calculate it?
Cardiac output = basically how much blood is being pumped/how well the heart is pumping
CO = SV x HR
What are the differences between dynamic and hydrostatic pressure? For a given vessel with a height h and the density of blood, how would you find the hydrostatic pressure?
Dynamic BP: force of the heart’s contraction on the blood
Hydrostatic BP: force of gravity on blood
Hydrostatic pressure: P = p*g*h (where p is the density of blood and g is gravitational acceleration)
For a given blood vessel, what is the relationship between pressure, flow and resistance?
Pressure = Flow x Resistance
Describe the relationship between the velocity of blood flow and the flow in a blood vessel. Would the speed of blood flow be higher in arteries vs capillaries? Why or why not?
Flow (aka Cardiac Output) = velocity * Cross sectional area of the vessel
Velocity of flow would be lower in the capillaries b/c even though individually they’re smaller, their total cross sectional area is greater than that of major vessels. Thus, the velocity will be lower.
What relationship does Poiseuille’s equation describe? If you were looking for a catheter for a procedure, what kind of parameters would you look for? (i.e. short and wide or long and narrow?)
Still describing the relationship between flow, pressure and resistance, excpet now we’re taking into account the length of the blood vessel, the radius of the blood vessel, and the viscosity of blood
Short and wide. Based on the equation, you’d get a higher flow rate with a short and wide tube.
How would you find the resistance for vessels in series (e.g. the major arterial branches)? What about the pressure drop? How is flow affected in vessels connected in series?
Flow for vessels in series is the same per vessel.
The pressure drop is the sum total of the pressure gradients between vessels
Resistance is the sum total of the resistance across each vessel. The resistance will be greater than that of any individual resitance.
How would you find the resistance for vessels in parallel? What about the pressure drop? How does flow change with each vessel, if it changes at all?
1/Rtotal = 1/R1 + 1/R2 + 1/R3
Flow splits at each vessel
Pressure = same for each vessel
Compare the blood pressure in the systemic circulation with the blood pressure in the pulmonary circulation. How would you calculate these? What are the highest points of pressure in either system? What are the lowest points of pressure?
Systemic circulation blood pressure: highest between LV and aorta (during systole) and lowest upon return from the vena cavas into the right atrium.
Pi-Po = MAP - MRAP
Pulmonary circulation blood pressure: highest in pulmonary arteries, lowest upon return to left atrium.
Pi-Po = MPAP - MLAP
What is the difference between total peripheral resistance and pulmonary vascular resistance?
TPR = total resistance of the systemic circulation
PVR = total resistance of the pulmonary circulation
Define compliance. What is the significance of compliance as it relates to blood pressure and volume? Which vessel, an artery or a vein, is more compliant? What does that mean for blood storage?
Compliance = how distensible a vessel is/how well a vessel can expand and take up more volume w/increasing pressure
Compliance = change in volume/change in pressure (reciprocal = stiffness)
Veins are more compliant than arteries, which explains why they are the capacitance vessels i.e. they store more blood
Explain the concept of wall tension (in words + using the Law of Laplace). Use this concept to explain why thinner vessels are more likely to rupture. What would cause a thicker vessel, like the aorta, to rupture?
Wall tension/wall stress is the amount of tension that’s exerted on the walls of a blood vessel.
WT = (Pressure x Radius)/2 *wall thickness
Thinner vessels are more likely to rupture b/c their walls aren’t strong enough to withstand high tension. An aorta or another big artery could rupture probably b/c high pressure and maybe the larger the wall gets as an aneurysm gets bigger, the weaker it gets, the more likely it is to rupture.
