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561 - Perfusion Technology > Exam 3 - Oxygenators > Flashcards

Exam 3 - Oxygenators Flashcards

1
Q

Actions of Real Lung

A
  • Gas Exchange (O2 and CO2)
  • Filtration (small capillary diameter and heparin in lining)
  • Immune Function (Macrophages: Innate / Lymphocytes: adaptive)
  • Biochemical function (metabolism of drugs)
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2
Q

Oxygenator vs Lung Surface Area

A

Lungs: 70m^2
Oxygenator: 1.8m^2

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3
Q

Function of artificial lung

A
  • Gas Exchange
  • Filtration
  • Drug delivery
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4
Q

Factors that affect diffusion rate in Oxygenators

A
  • Pressure gradient: increases / changed by perfusionist
  • Surface Area: increases / set my manufacturer
  • Solubility: increases / usually constant (increase with increase temp)
  • Distance: decreases rate / set by manufacturer
  • Sqrt of MW: decrease rate / pretty constant in perfusion
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5
Q

Transfer of O2 and CO2 in blood

A
  • O2: hemoglobin
  • CO2: bicarb
  • Diffusion of CO2 is much faster than O2 but conversion of CO2 to bicarb and back in RBC takes much longer….
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6
Q

Natural vs Artificial Lung Capillary

A

Diameter: 7-8um vs 150-250um (25x)

Surface Area: 70m2 vs 1.8 m2 (2.5% of)

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7
Q

How to maintain Natural lung O2 in Artificial Lung

A

1 - Dwell time
2 - Secondary flow (make blood swirl toward edges)
3 - O2 Pressure gradient (much higher in Artificial…110-680 vs 65)
-CO2 pressure gradient also higher (5 vs 45)
4 - Decrease metabolic demand of patient (cool down/anesthesia)

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8
Q

Cardiac Surgery History

A
  • Began in 40’s without CPB

- 50’s had high mortality rates with ASD surgeries (17/18 died)

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9
Q

Early artificial oxygenation

A
  • Isolated monkey lungs
  • Film oxygenators (1/4 survived….Gibbon)
  • Rotating disc oxygenators (Kay-Cross…50’s)
  • Cross circulation
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10
Q

Father of Heart Surgery

A
  • C. Walton Lillehei

- 1954

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11
Q

Richard De Wall

A
  • First perfusionist
  • Made Dewall-Lillehei Bubble oxygenator in 1955
  • Replaced cross circulation
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12
Q

Parts of bubble oxygenator

A
  • Gas Sparger (bubble size)
  • Mixing column
  • De-foaming/de-bubbling area (steel wool, silicone, poly foam)
  • Heat exchanger (also a secondary place for gas exchange)
  • Arterial reservoir
  • Resistance usually low so had a low pressure drop
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13
Q

Bubble O2 bubble size

A
  • Small (high SA:V ratio, high O2 exchange, low CO2 exchange, high GME potential)
  • Large (low SA:V, low O2 exchange, high CO2 exchange, low GME)
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14
Q

Bubble O2 gas flow vs. FiO2

A
  • FiO2 always 100% (did not want N2 mixed into blood)
  • Flow rate determined # of bubbles
    • usually start 1:1 gas flow to blood flow ratio
    • low ratio: transfer of O2/CO2 decrease -> PO2a down, PCO2a up)
    • high ratio: opposite
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15
Q

Bubble Oxygenators facts

A
  • Balanced O2 / CO2 transfer difficult to achieve
  • GME
  • Increased foreign surface exposure and turbulence increases immune responses
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16
Q

Oxygenator Useage

A
  • By 1986…more membrane Oxygenators in use than bubble

- By 2000…no more bubble Oxygenators in use

17
Q

Types of membranes in membrane Oxygenator

A
  • Capillary: made of Polypropylene/Polymethylpentene (PMP)
  • Flat plate folds: made of silicone
  • Coils: made of silicone
  • Silicone and PMP are not porous aka “true membrane”
  • Polypropylene is porous
18
Q

Prime volume comparison

A

Hollow fibers

19
Q

True Membrane advantages

A
  • More efficient gas exchange
  • More balanced gas exchange (high O2 across and low CO2)
  • Minimal GME
  • Imrpoved blood flow path
  • No direct blood:gas interaction (better biocompatibility)
20
Q

Membrane Oxygenator induced turbulence

A
  • Small jagged wall in membrane capillary to:
    - Induce turbulence (better gas exchange)
    - Decrease distance (higher diffusion rate)
21
Q

Bubble vs Membrane

A
  • Independent CO2/O2 control: Yes M / No B
  • FiO2: Variable for M / 100% for B
  • Gas:Blood flow ratio: affects PaO2/PaCO2 for B / Just PaCO2 for M
    - Increase flow -> more CO2 transfer
  • Also can add 100% CO2 to gas flow in Bubble
  • Type of system: Open for B / Open or closed for M
22
Q

Hollow Fiber Oxygenation

A
  • Made of PMP
  • Blood flow can be extraluminal or intraluminal
    - Intraluminal is not used anymore (high R, less SA, high prime)
23
Q

True membrane vs porous membrane Oxygenators

A
  • True can last 14 days and is selectively permeable

- Porous lasts 6 hrs and is not selectively permeable (relies only on pressure gradients)

24
Q

Blood phase pressure vs Gas phase pressure

A
  • Need to keep higher blood phase pressure otherwise gas moves into blood in the oxygenator and air gets into system
  • Higher blood phase pressure allows blood to keep higher surface tension over holes in hollow fibers
25
Q

Wetting of membrane surface in hollow fiber Oxygenators

A
  • Prolonged use leads to this
  • Get plasma leakage through pores
  • Bubbles form on Oxygenator
  • Very bad
26
Q

Hollow fiber oxygenators

A
  • Good but still 2-8x less efficient than natural lungs
    (Still need dwell time, pressure gradient, decrease metabolism)
  • Primary limitation to exchange is diffusion into blood phase
    (Blood to viscous to push through single file)
27
Q

Minimum and Maximum O2 levels in blood

A

Min: 21%
Max: 100%

28
Q

Blood gas control

A
  • O2 too low….Increase FiO2
  • O2 too high….Decrease FiO2
  • CO2 too low….Decrease Gas:Blood flow ratio
  • CO2 too high….Increase Gas:Blood flow ratio
  • SvO2 too low….Increase Blood flow (60-80%)
29
Q

How to tell a failing Oxygenator

A
  • PO2 drops even with increase in FiO2
  • PCO2 increase even with increase in blood flow (sweep rate)
  • Rising pressure gradient across Oxygenator
30
Q

What to do before an Oxygenator change out

A
  • Check all gas tubing, lines, connections
  • Consult with Anesthesiologist that patient is knocked out
  • Draw A and V blood gases
  • Check Hbg/Hct
  • Calculate O2 transfer rate
    [ 1.34 * (X gm Hgb / 100) * (Art sat - Ven sat) * ml/min ]
    • If lower than IFU recommended rate, could be failing
31
Q

Rated Blood Flow

A
  • Max flow at which you get 95% O2 in A and 65% O2 in V
32
Q

CO2 Reference Blood Flow

A
  • Flow rate in which CO2 content is decreased by 38 mL per Liter of flow
33
Q

O2 Reference Blood Flow

A
  • Flow rate in which O2 is increased by 45mL per Liter of blood flow
34
Q

Reference Blood Flow

A
  • Lowest O2/CO2 Reference flow, manufacturers recommended flow, or 8 L/min
35
Q

Index of Hemolysis

A
  • Mg of plasma free Hgb generated per 100 L of blood pumped through Oxygenator
36
Q

Initial Priming Volume

A
  • Volume needed to fill Oxygenator and heat exchanger to minimal reservoir volume (set by manufacturer)
37
Q

Oxygenator Thrombosis

A
  • Random increase in Oxygenator inlet pressure of up to 900mmHg within 10-15 min of starting CPB despite adequate anticoagulation
  • 1 in 230 cases
  • Can prime with Albumin to minimize this
  • Can cool slower
  • Can cause oxygenator change out

561 - Perfusion Technology (12 decks)

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