Oxygenators Bruce's Final Exam Flashcards
What
is
an
oxygenator?
• Gas Exchanger: –Removes CO2
–AddO2
–Adds Other gases
(anesthe)cs)
The Ideal Oxygenator should ?
• Oxygenate venous blood • Cause minimal blood trauma • Minimal priming volume • Designed formaximum safety
3oxygenator designs?
- Film oxygenators
- Bubble
- Membrane
“True” Membrane oxygenators were made of ___ .
-Provide a complete barrier between the gas and the blood phase so that gas transfer depends totally on ___.
- Silicone
- Diffusion
Microporous membrane was made of ?
• Polypropylene
• Polymethylpentene
- Flat Plate
- Hollow Fiber
3 Disadvantages of film oxygenators ?
–Huge prime
volumes
–Huge surface area
–Lots of blood trauma
2 Pros for bubble oxygenators?
- Inexpensive
- Low prime volume
3 Cons for Bubble Oxygenators ?
– Massive air
interface
– Huge surface area
– Air embolus
2 types of Types of membrane oxygenators?
- True Membrane
- Microporous
membrane
3 Pros for “True Membrane” Oxygenators?
– Silocone envelope
– No blood to gas interface
– Approved for long termuse
2 Cons for “True Membrane” Oxygenators?
– High resistance
– Large priming
volume
Microporous Membrane
Pore size=
Thickness=
Pore size = 0.5-1 um
Thickness= 25-50 um
Microporous
Membrane
flat sheet surface area ?
.5 - 4.5 M^2
Hollow fiber mat
diameter =
Length =
diameter = 200 - 250 um Length = 10 - 15 cm
2 pros of microporous membrane which increased efficiency ?
- Reduced Surface Area
- Reduced priming volume
4 pros of microporous membrane
- Transient gas interface
- Pore Wetting
- Pulmonary Edema
- Short term use <6hrs
2 styles of futuristic membrane implantations ?
- In series
- In parallel
Passive Diffusion through an oxygenator formula.
=(A/T) (D) (P1-P2)
A: Surface Area
D: Diffusion Coefficient
P: Pressure Gradient
Surface area M^2
Oxygenator =
Lung =
Oxygenator = .5-4 Lung = 70
Blood path width/length
Oxygenator =
Lung =
Oxygenator = 200 /250,00 Lung = 8 /200
Membrane thickness
Oxygenator =
Lung =
Oxygenator = 150 Lung = .5
Max O2 transfer
Oxygenator =
Lung =
Oxygenator = 400 - 600 Lung = 2000
Design issues of artificial lungs
- Diffusion coefficient
- Transit time
- Boundary Layer
What happens with O2 as distance increases from the membrane?
decreases
2 fluid characteristics of Laminar flow closest to the wall?
- Highest sheer force
- lowest velocity
As laminar flow continues ?
The layer becomes progressively thicker
True or false
Is there a cell free layer of plasma on the membrane?
True
Secondary flow through cross fibers and integral screens creates?
Turbulent flow
What was the solution to boundary layer problems?
Induction Secondary flows
Blood phase
Blood path through the oxygenator
Gas phase
Gas path through the oxygenator
Blood path through the oxygenator is referred to as the blood phase. What is the blood path in the lung?
Capillary
Gas Path through the oxygenator is referred to as the Gas phase. What is the Gas path in the lung?
Alveoli
The Gas phase pressure must never exceed what ?
the Blood phase pressure
Microporous oxygenators have numerous vents on the exit of the gas phase to protect against what ?
Pressurization
Formula for blood phase oxygen transfer?
VO2= (Q) (CaO2 - CvO2)
C.O. Formula based on the Oxygen transfer formula.
C.O. = VO2 / (CaO2 - CvO2)
100 ml blood =
Vol %
Average value of VO2 fro the anesthetized adult?
120 ml/min/^M2
Oxygen transfer across the membrane is dependent upon 5 variables including*:
- Driving gradient
- Blood flow rate
- Blood path thickness
- Membrane surface
area - Membrane diffusion
characteristics
FiO2 is plotted on the Y-axis and total Oxygen transfer is plotted on the X-axis. the area of the chart ABOVE the normal line represents what?
oxygenator performance that is worse than predicted
FiO2 is plotted on the Y-axis and total Oxygen transfer is plotted on the X-axis. the area of the chart BELOW the normal line represents what?
oxygenator performance that is better than predicted
