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Cardiac
Hemodynamics
| Question | Answer |
|---|---|
| hemodynamics | study of blood flow & interrelationships of BP, blood flow, & the physical properties of blood |
| Newtonian fluid | a fluid with a constant viscosity at any given temperature (i.e. water) |
| Non-Newtonian fluid | a fluid that can change viscosity (i.e. blood, suspensions) |
| blood flow | the volume of blood that passes a given point in a given period of time; pressure/resistance |
| What factors effect blood viscosity? | vessel diameter, temperature, & chemical composition |
| Law of Hemodynamics | blood flows from a proximal area of higher pressure to a distal area of lower pressure |
| What factors determine resistance? | radius of a vessel, length of a vessel, & viscosity of blood; smaller radius=increased resistance, longer vessel=increased resistance, higher viscosity=increased resistance |
| change in pressure= | P1-P2 (proximal pressure-distal pressure) |
| Poiseuille's Law | shows relationship between pressure gradient & volumetric flow |
| average blood flow moved by heart per minute | 5L/min |
| The biggest contributor to vascular resistance is? | vessel diameter (ex. doubling the radius of a vessel decreases the resistance by a factor of 16) |
| hematocrit | the fraction of blood which is formed elements |
| high hematocrit= | higher viscosity |
| low hematocrit= | lower viscosity |
| cardiac output= | stoke volume x heart rate |
| stroke volume= | end diastolic volume - end systolic volume |
| laminar flow | stable flow that occurs in fairly straight, unobstructed vessels |
| plug/flat flow | occurs when all blood cells travel at the same velocity |
| parabolic flow | has a bullet shape due to friction at the vessel walls |
| turbulence | disturbed flow occurring when blood flow exceeds a certain critical velocity; chaotic flow patterns |
| eddy currents | appear as small hurricane-like swirling patterns |
| vortex shed distance | laminar flow proceeding as a high velocity, narrow jet past an obstruction over a short distance |
| vena contracta/effective orifice area | narrowest point of the jet distal to the obstruction |
| actual orifice area/AOA | area at the opening of the valve |
| Reynold's number | describes the tendency for turbulent flow |
| Reynold's number < 2000= | trend for laminar flow |
| Reynold's number > 2000= | trend for turbulent flow |
| Bernoulli's equation | shows relationship between blood flow velocity & the pressure gradient across an obstruction; 4 times velocity squared |
| Venturi effect | the velocity of the fluid increases as the cross sectional area decreases, while a pressure drop occurs |
| continuity equation | proximal flow = distal flow |
| pressure half time | the time taken for the maximum pressure gradient to be halved, as the pressure drops distal to the obstruction |
| What measurements are needed to obtain SV through the LVOT? | LVOT diameter (measured in early to mid systole) & LVOT VTI |
| How do we calculate LVOT area? | 0.785 x LVOT d squared x LVOT VTI |
| Where do we obtain LVOT diameter? | PLAX |
| Where do we PW to get LVOT VTI? | Apical 5 |
| Where do we CW to trace AV VTI? | Apical 5 or Apical 3 |
| When determining RVSP, what do you have to remember to add to Bernoulli's equation? | right atrial pressure |
| What is the RA pressure value for normal RA size & IVC collapse w/inspiration? | 3mmHg |
| What is the RA pressure value if the RA is large & IVC collapse is <50%? | 8mmHg |
| What is the RA pressure value if there is a lack of IVC collapse? | 15mmHg |
Created by:
ginaliane
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