Hemodynamics Flashcards
Flow =
vol./time
Velocity of Flow =
dist./time
laminar blood flow
- blood flows in concentric layers
- each layer of blood flows at a different velocity
- no sound production can be heard by stethoscope
laminar vs turbulent blood flow:
- laminar provided max amount of flow for a given pressure
- velocity is front square (inefficient) for turbulent and parabolic for laminar
- turbulent flow can be auscultated with stethoscope = sound production
Measuring arterial BP:
- cuff pressure is inflated to a point which exceeds systolic pressure.
- The cuff is slowly deflated. When cuff pressure is slightly below systolic blood pressure, turbulence, and hence, an audible (Korotkoff) sound is produced. This turbulence results from blood “squirting” under the cuff and “crashing” into stationary blood downstream.
- At that initial turbulent point, the cuff is continuously deflated to a point where audible turbulence disappears. This second point corresponds to diastolic pressure.
Laminar flow is more likely with:
high viscosity, low density, small diameter, and low velocity
relationship between pressure and flow for laminar flow
linear - inc pressure = inc flow
Anomalous Viscosity
viscosity refers to the observation that as blood flow decreases, viscosity increases
Law of Laplace
addresses the effect of increased chamber size on ventricular wall tension.
-wall tension inc will inc compression on arteries in that wall
tension in the wall of the ventricular chamber is proportional to…
its radius and pressure.
blood distribution?
75% venous, 20% arteries, 5% capillaries
Factors that govern blood flow
a. viscosity of blood
b. length of vessels
c. radius of vessels
d. pressure gradients
renolds number:
tendency for turbulence - large if high velocity, diamter or density and smaller is more viscous
venous system is what kind of system?
capacitance
arteriole system is what kind of system?
resistance
increase in surface area does what to velocity?
Decrease
POISEULLE’S LAW on flow
- vessel radius has greatest effect on flow
- ex) if radius is doubled you get 16 times increase in flow
isssue with large/dialated hearts?
-larger hearts mess up coronary perfusion
flow is directly proportional and indirectly proportional to?
dir to pressure and indir to resistance
Pulmonary circuit resistnace compared to peripheral circuit resistance?
pulmonary has about 1/10 the resistance of the peripheral
