What is occlusion and how can it be set?
compression of the silicone tube by means of a roller pumps cylindrical rolls. for an optimal occlusion the caused blood damage is the lowest.
can be modified by changing the pump rotors radius by means of a wheel in the middle
Describe the principle of a roller pump.
- displacement pump
- silicone tube compressed by rolls (occlusion)
- rotation of the pumps head transports the blood further
- tube is held in place by inserts of different sizes as well as by guiding pens
List the pro/contra of roller pump.
\+ simple technology \+ only pump segment has to be changed \+ l/r mode \+ no backflow if stop \+ pulsatility
- can pump air
- no air elimination
- blood damage (occlusion)
- no high pressure safety
- spalation
Why do you need a pressure shut off for roller pumps?
roller pumps have no high pressure safety. if the pressure at the pump outlet rises for any given reason, the pump will continue to pump until the tube explodes. therefore, a pressure sensor is needed to shut of the pump if the pressure gets to high
Can the right setup avoid air suction of the roller pump?
yes, macrobubbles can be avoided, microbubbles however cannot
What are the dangers for to high/low occlusion?
high: spalation of tube material due to the high compression of the tube
low: backflow -> vortices behind the rolls -> shear stress -> hemolysis
Describe the principle of the centrifugal pump.
- axial inlet with tangential outlet
- blood accelerated by the pump heads rotation -> adhesion to the surface -> centrifugal acceleration
- magnetic coupling of the rotor with motor
List pro/contra for centrifugal pumps.
\+ no air pumping \+ air elimination \+ less heparin \+ media separation \+ high pressure safety
- high cost
- replace entire head
- flow sensor
- no pulsatile flow
- high heat
What is the danger when centrifugal pump stops?
since there is no occlusion, the blood will flow back through the arterial line to the reservoir if the pump stops
What precautions have to be considered for centrifugal pumps?
a flow sensor with clip is needed to stop a blood backflow if rpm is too low for example
How can air in the centrifugal pump be avoided?
the blood inlet has to be on top
Explain the blood flow inside a centrifugal pump with coni.
the rotors blades are curved, reducing the amount of vortices behind them -> less shear stress and less damaged erythrocytes
Explain the function principle of the intra-aortal ballon pump.
- mechanical device that increases myocardial oxygen perfusion while at the same time increasing cardiac output
- situated in the aorta, 2cm to the left subclavia
- deflation during systole -> increasing forward blood flow due to a vacuum effect
- inflation during diastole -> increased coronary perfusion -> increased myocard oxygen supply
