System Overview Flashcards
Fetal circulatory modifications increase/minimize: pulmonary blood flow
minimize
What blood is preferentially vented to the left atrium via the foramen ovale in fetal circulation?
umbilical vein blood (more oxygenated and goes to the brain) vs. svc blood which goes through the rv, pulmonary artery, ductus arteriosus to the descending aorta
4 circulatory changes at birth
- decrease in pulmonary vascular resistance
- increased venous return from lungs
- closure of ductus arteriosus
- increased RV compliance
What stimulates closure of the ductus arteriosus?
increased o2 concentration and withdrawal of pge2
What is the importance of increased venous return from lungs in the days after birth?
left heart filling opposes flow across foramen ovale
Which cardiac parameter? volume of blood/unit time
cardiac output
Which cardiac parameter? cardiac output normalized to body size by dividing by body surface area
cardiac index (2.5-3.5 is normal)
Which cardiac parameter? volume of blood ejected during each heart beat
stroke volume (100 ml/beat is normal)
Which cardiac parameter? pressure in arterial system
systemic arterial pressure
Which cardiac parameter? resistance to flow through vascular system
vascular resistance
Which cardiac parameter? percent of blood volume in left ventricle at end diastole that is ejected during systole
left ventricular ejection fraction/LVEF = crude measure of left ventricle contractile performance (normal = 55-70%)
Which cardiac parameter? axial pressure difference in a vessel or series of vessels
driving pressure
Which cardiac parameter? radial pressure difference
transmural pressure
Which cardiac parameter? pressure due to gravitational effect
hydrostatic pressure
2 parameters that affect flow resistance
- vessel radius
2. blood viscosity
Which cardiac parameter? relationship between pressure distending a structure and its volume
compliance (dV/dP)
Rigid structures have high/low compliance
low
Highly/non compliant structures distend easily
highly
What physical phenomenon describes the change in force required to maintain constant compliance as vessel size increases?
laplace relationship
Which physical principle? relationship between pressure gradient/driving pressure and flow velocity
bernoulli –> change in pressure is quadratically related to velocity (c = p +.5pv^2) –> enables you to determine severity of obstruction caused by diseased valve or severity of stenosis
Which physical principle? relationship between transmural pressure, radius, and wall force
laplace –> larger radius chambers require greater wall force to generate a given pressure (t = p * radius) –> risk of rupture for aneurysms and determines contractile performance of pathologically enlarged hearts
Which physical principle? relationship between pressure drop/driving pressure and flow of fluid in a tube in relation to viscosity and tube diameter/length
poiseulle –> pressure regulated by changing flow resistance via modulation of arteriolar diameter (flow = change in pressure * pi * r^4/9nl) –> increased blood viscosity impairs circulatory performance
Which physical principle? relationship between flow velocity, blood viscosity, vessel diameter, and flow turbulence
reynolds (v=Kn/pr) –> determines laminarity/turbulence in generation of cardiac murmurs and bruits
Which physical principle? relationship between voltage, resistance, and current flow in a DC circuit
current = voltage/resistance –> flow (q) = pressure/resistance
