HEMODYNAMICS Flashcards
poiseuille equation
- relationship of flow, pressure and resistance
- single vessel, organ
poiseuille equation
- flow= to pressure gradient/resistance
- P1 upstream pressure
- P2 pressure at the end of segment/circuit
- R resistance of vessel bet. P1 and P2
resistance is inverse to
- flow
- radius
the most important factor determining resistance of a vessel
- vessel radius
resistance is proportional ….
to but inversely proportional to flow
- viscosity
- polycythemia vera (increase viscosity and resistance, decrease flow leading to thrombosis)
- anemia (decrease viscosity and resistance, increase flow hyper dynamic flow fast rush of blood bruit)
50% occlusion of the left anterior descending artery
- 16x decrease in flow (r4)
polycythemia vera
increase viscosity and resistance,
decrease flow leading to thrombosis
an increase in hematocrit, increase in viscosity
turbulent flow
- murmurs
- bruits
- severe stenosis
- more resistance
- > 2000 flow
laminar flow
- least resistance
- good flow
- ## away from the wall towards the vessel
reynolds number
- diameter x velocity x density/ viscosity
resistance
series
parallel
series
- flow is dependent flow must be equal at all points
- resistance to the total series is equal to the sum of individual system
- equal flow
- Rt > Ri
- with in organs
parallel
- flow is independent to each other
- flow is not equal
- Rt
the total resistance(Rt) is always
- less than any of the individual resistance (Ri)
organ donor (Kidney) parallel
- as we add total becomes less
- subtract resistances the total resistance increase
- increase resistance
- flow is decrease
- CO decrease to compensate for increase BP
- HR decrease to decrease BP
- bradycardia normal for donor
- wt gain
- increase TPR, MAP
CO
= mean arterial pressure/TPR
mean arterial pressure
= CO x TPR
CO
= HR x SV
LaPlace relationship (wall tension)
- T- wall tension
- P- pressure
- r- radius
- dysfunction can lead to aneurysm
aorta
- is the artery with the greatest wall tension (greatest pressure while lying down and RADIUS)
- reason for aorta predispose to aneurysm
- causing dissecting aneurysm
increase in radius and pressure
- increase in tension agains the wall
- increase pooling of blood causing less blood goes to the heart
compliance
- change in volume/ change in pressure
- vessel is easily stretched
- 60 y/o has more compliance in his lung
- aging loose elasticity
elasticity
- inverse to compliance
- recoil
- more elasticity less compliance
VEINS
- 20x more compliant than arteries
- 70% of systemic blood volume
- major blood reservoir
- less elasticity(to have more compliance, has the ability to change volume) due to less muscles in the walls
- no recoil
- small change in pressure will cause a large change in volume
- have high compliance
veins pathophysiology
- in hemorrhage
- venous pressure decreases
- causing passive constriction of veins
- decrease blood storage
- blood is removed from the vein to the arteries to increase CO to compensate to hemorrhage
- SYMPATHETIC INNERVATION causing VASOCONTRICTION alpha 1
artery
- decrease in compliance
- increase radius increase flow
venodilator (nitrates)
- decrease in venous return
- decrease preload
- decrease flow
arteriolar dilator
- increase flow
- decrease in pressure in the system
- decrease TPR arteries
volume loading
- increase venous pressure which causes passive dissension of veins
hemorrhage affected VEINS
- decrease volume
- decrease pressure
- sympathetic response
- alpha 1
- constriction
- decrease pooling
fluid infusion, fluid overload
- increase pressure
- increase pooling of blood
- by distention of the vein
- less blood will go to the heart
- decreasing the venous return in the heart
- will cause massive dilation of the veins
