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561 - Perfusion Technology > Exam 2 - Topic 3 - Pumps For The ECC > Flashcards

Exam 2 - Topic 3 - Pumps For The ECC Flashcards

1
Q

Methods for moving fluids

A
  • Volumetric displacement (mechanically or with other fluids)
    Ex. Positive displacement roller pump - mechanical
  • Centrifugal force (Centrifugal/rotary pump - suck and push)
  • Gravity (Drain the Veins)
  • Relative vacuum (Drain the Veins)
  • Kinetic assist (Ex. Centrifugal pump) (Drain the Veins)
  • Mechanical impulse (some old VADs)
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2
Q

Kinetic assists method

A
  • Example is Centrifugal pump
  • Pro: Can create a vacuum for great suction
    Safer than roller pumps as it is harder for them to push air
  • Con: Can make big air bubbles into small micro air bubbles
    Can implode reservoir if no vacuum release
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3
Q

Heart as a pump

A
  • generates blood flow and blood pressure
  • blood carried to body via vascular system
  • valves of heart ensure one way flow
  • controlled by neural innervation, hormones, and volume status
  • pumping rate controlled by internal “pacemaker”
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4
Q

Arterial pump (vs. Heart as pump)

A
  • Also generates blood flow and blood pressure
  • Blood carried to body via arterial lines and arterial cannula -> then carried to tissues via vascular system
  • Tubing of ECC ensures one way flow (need to clamp when coming off CPB when using centrifugal pump… Otherwise back flow)
  • Pump is controlled by perfusionist
  • Pumping rate controlled by perfusionist (RPMs and tube diameter)
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5
Q

Cardiac output (aka blood flow)

A
  • CO = (SV)(HR)
  • Determinants:
    Preload - venous return / blood volume (amt into heart)
    Afterload - Aortic Diastolic pressure / SVR
    -> what is it pumping against / size of tubing
    Contractility - Starling curve / neural / hormonal
    HR - intrinsic / neural / hormonal
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6
Q

Starling Curve

A
  • Relationship between fill and CO
    - > Fill on X axis….CO on Y
  • Parabolic shape
  • increase in fill…increase in CO until max fill reached
    • > anything after max fill reduces CO due to over stretching
    • > if too overstretched…muscle can never contract back…kills heart
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7
Q

Arterial pump CO

A
  • What is read on machine if calibrated correctly
  • Amount of blood pumped per minute
  • PF = (SV)(RPM)
    - > SV = pir^2l*2
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8
Q

Physiological factors affecting Perfusion flow

A
  • Preload: venous return to venous cannula / blood volume / venous return gradient (siphon or augmented)
  • Afterload: resistance of tubing, heat exchanger, oxygenator, arterial line filter, and patients SVR
  • Contractility: pump type / tubing size / fixed?
  • HR: RPMs
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9
Q

Characteristics of Ideal Blood Pump

A
  • Flow rate of at least 7 L/min against 500mmHg
  • Flow independent of afterload and preload
  • Controllable SV and pulse rate
  • Flow proportional to pulse rate
  • Exact and reproducible calibration of pump flow
  • Minimal transfer of energy to blood (not damage blood too much)
  • Parts in contact w/ blood should be:
    - disposable
    - smooth
    - free of stagnation, turbulence, cavitation
    - biocompatible on surface
  • Have battery / manual backup
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10
Q

Positive displacement pump examples

A
  • Reciprocating: chamber is alternately filled and emptied

- Roller: most common (what we use)

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11
Q

Reciprocating pump

A
  • Creates pulsatile flow
  • Actuator used to expel bloop from pump chamber
    - > either in contact with blood or separated by diaphragm
  • Needs valves to ensure no back flow
  • Used for long term assistance
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12
Q

Roller pumps

A
  • Output depends on pump speed & volume displaced/rotation
  • Has a semi-circular “raceway”
  • Volume displaced/rotation based on tubing size & length of raceway
  • Can be single, dual, or multiple (dual most common)
  • DeBakey a leader in field (stopped tube creeping with new design)
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13
Q

Creepage

A

1 - tubing creeping through raceway as roller turns

2 - moving clamp down the tube to compensate for blood pressure

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14
Q

Ideal characteristics of boot tubing

A
  • transparent
  • resilient
  • flexible and kink-resistant
  • crack proof
  • minimal spallation
  • biocompatibility
  • tolerate temperature extremes (15-42)
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15
Q

Types of tubing

A
  • Silicone rubber: most biocompatible / most spallation
  • Latex: not used in USA
  • PVC: most common now / blend of PVC, organic oils, organo-metal soaps
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16
Q

Durometer

A
  • How hard the tube is
  • higher # is higher tubing
  • ECC tubing is 65-72 / IV tubing is 80
  • Temp affects hardness
  • Hardness affects: tubing memory, fatigue life, spallation
17
Q

Spallation

A
  • Release of micro particles from inner wall of tubing
  • can cause embolic potential
  • majority of it happens first 2-4 hours (hence pre-bypass filter)
  • What affects spallation
    - pump RPMs / tubing durometer / age of tubing
18
Q

Optimal Occlusion

A
  • just barely occlusive
  • occlusion must be set on all pump heads for every procedure
    • > every time
  • Always TIGHTEN to occlusion
19
Q

Gold standard of occlusion

A
  • raise tubing so meniscus is 30 in above raceway
  • meniscus drops 1 cm every 1 min
  • not really used
20
Q

Dynamic Occlusion

A
  • goal is to get fluid column to stop moving at 200-250 mmHg
    - > why? It will match the typical afterload resistance in CPB
  • clamp distal to outlet
  • let pressure settle to 250-300 mmHg
21
Q

Characteristics of Pump Occlusion

A
  • Occlusion can vary due to temp and fluid composition
  • Over occlusion -> hemolysis, increased tubing wear/stress
  • Under occlusion -> back flow / turbulence / inaccurate flow calibration / hemolysis
    - Turbulence measured by Reynolds # ( >2000 is bad)
22
Q

Afterload and preload dependence (Roller)

A
  • positive displacement pumps are after/preload independent
  • doesn’t matter pressure after or before pump….volume displacement is constant at a given RPM
  • Consequences: - excessive distal pressure (can blow circuit)
    - can generate negative pressure if inlet is clamped
    - can pump large volumes of air very fast to patient
23
Q

Roller pump complications

A
  • Malocclusion
  • Miscalibration
  • Fracture / rupture tubing
  • “Runaway” pump head
  • Loss of power
  • Spallation
  • Can pump gross volume of air
  • Can blow up circuit if arterial line is clamped or occluded
  • can pull air out of solution if negative pressure introduced
24
Q

Types of Centrifugal pumps

A
  • Axial: Archimedean screw / small prime volume and weak power / most expensive / not used for bypass
  • Diagonal: centrifugal / large prime volume / mid power / disposable
  • Radial: centrifugal / large prime volume / high power / disposable
25
Q

Rotary / Axial Centrifugal pump

A
  • 2.5 - 5L/min
  • Very high RPM….can only be used for short time otherwise hemolysis
  • placed in Cath lab
26
Q

Diagonal/Radial centrifugal pumps

A
  • came about in 1973 by Biomedicus
  • requires drive console, disposable pump head, and flow meter
  • two types of pump heads: concentric and impellers (fins)
  • creates pressure gradient between inlet and outlet via vortex
27
Q

Flow generation formula of Centrifugal pump

A

Blood flow (Q) = (Po - Pi) / R

Po = outlet pressure
Pi = inlet pressure
R = resistance
28
Q

Centrifugal Force Generation formula

A

F = m*v^2 / r

So….if air gets into pump…force = 0 (air has no mass)…pump will stop
-> have to reprime but it is safer
Also shows us the larger the diameter…the more efficient (more force)

29
Q

Max positive and negative pressures of Cent. Pumps

A

-Maximum positive outlet pressure = 700 - 900 mmHg
>900….BOOM
- Maximum negative inlet pressure = -400 - -500 mmHg

30
Q

Constants for each pump type

A
  • Roller - constant flow
  • Centrifugal - dependent on inlet/outlet pressure
  • Heart - constant pressure
31
Q

Centrifugal pump afterload/preload dependency

A
  • They are dependent on them
  • Inversely related to afterload
    - if afterload pressure>outlet pressure -> no flow
  • Directly related to preload
    - if too low preload…cavitation possible and line chatter
  • So…flow rate not constant at any given RPM…need flow meter!
32
Q

Complications of Centrifugal pumps

A
  • Retrograde flow possible when coming off bypass
    - Must clamp when coming off
  • Pump failure
  • Speed surges
33
Q

Safety devices

A
  • Low level sensors
  • Bubble detectors
  • high/low pressure sensors
  • one way valves
  • battery and flashlight that works
  • hand cranks

561 - Perfusion Technology (12 decks)

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