Group 3 Alternative Devices

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Group 3 Alternative Devices

• Ekaterini Malliari,
• Malik Alrawashdeh, Siddig Omer, Angelo Fernandes,
  Mamta Naik,
• David Hughes

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Hattler Catheter

• Design and Transfer Rates
• Ekaterini Malliari
• Operational Limitations
•  Malik Alrawashdeh

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DESIGN
Hattlers device involves a simple catheter to
witch about a thousand tiny fiber membranes have
been attached. A vacuum outside the patients
body pumps pure oxygen into the catheter. When
the O2 reaches the fibers, it is forced out into
the bloodstream by a balloon. CO2 is absorbed and
cleared by the fibers semipermable membranes.
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HOW DOES IT WORK?

• The Hattler catheter
• Is placed within the central venous blood stream,
• Contains a cylindrical bundle of micro porous
  hollow fiber membranes that are manifolded to gas
  flow pathways in the catheter itself, enabling
  the flow of pure O2 gas from a console outside
  the patient through the hollow fibers of the
  catheter and into the vena cava.

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HOW DOES IT WORK?

• The diffusion of O2 is allowed by the fiber
  membranes into the
• bloodstream, while CO2 diffuses out of the
  bloodstream, into
• the fibers, and is removed through a second
  gas pathway
• leading out to the external console.

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GAS RATES

• The active mixing of blood provided by the
  balloon pulsation augments gas exchange
  significantly, so that each fiber provides 2 to 3
  times more gas exchange than the fibers in
  conventional extracorporeal blood oxygenators.
• Over 30 catheters placed in 18 calves have
  demonstrated the Hattler catheter is capable of
  consistently providing 30-40 of the patients O2
  supply and CO2 removal requirements.
• In vitro performance demonstrates an O2 delivery
  of 140 /- 8.9 ml/min/m2 and a CO2 removal of 240
  /- 6.1 ml/min/m2. While in vivo we have a
  maximum CO2 consumption of 378 /- 11.2
  ml/min/m2.

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OPERATION REQUIRMENTS AND LIMITATIONS

• The delivery system has three main functions
• To supply oxygen to the fiber bundle
• To remove the oxygen and carbon dioxide exhaust
  gases from the fibre bundle
• To allow the delivery of an oscillating flow of
  helium to actuate the balloon

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For maximal oxygen exchange

• For optimum operation the pressure losses before
  the fibre bundle should be minimised because
• Any loss of pressure before the fiber bundle will
  detract from the driving gradient for oxygen
  exchange.
• The pressure losses after the fiber bundle should
  also be as small as possible to reduce the load
  on the driving system.

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Limitation regarding Balloon drive system and
cardiac output

• To ensure full filling and emptying of the
  balloon, a low resistance helium pathway is
  required.
• Balloon fails to fully inflate and deflate the
  balloon above a beat rate 180 beat per min (
  increasing the rate limitation)
• Size of the balloon limitation
• Also reduction in cardiac output

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MicroOxygenators

• Introduction to MicroOxygenators
• Siddig Omer
• Operational Limitations
• Agnelo Fernades

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The design

• A sandwich design.
• Metal sheets with channel and a membrane
• Membrane allow O2 CO2through.
• TS a2/c2
• 303025cm?human transfer surface(90m2)

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• Channel height and is width 100 µm, sheet
  height 200µm, Membrane height 35.
• Mice-Micro-Oxygenator.

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Optimisation

• Better sealing, more robust house.
• Add heating function.
• enlarge oxygen exchange / saturation value.

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• Problem membrane does not always closes off the
  blood or gas
• chambers at the resp. inlet and outlet sides.
• Gluing the membranes to the resp. sheets
  guarantees no overspill.

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MICRO-OXYGENATORS LIMITATIONS
Priming volume (ml) v/s Transfer surface (m 2)
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Research Work

• Better priming volume / transfer surface ratio
• Sealing of blood chamber
• Better Geometry design
• Cost effective sheet production

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Clinical Trials

• Hattler Catheter
• David Hughes
• MicroOxygenation System
• Mamta Naik

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Hattler CatheterTransfer Rates

• Natural Rate
• 240 ml/min for O2
• 200 ml/min for CO2
• Federspiel, Golob, Hattler et al 2000
• 250-350 ml/min/m2 for both O2 and CO2
• Potential increase of 500
• Increase of rate with active area increase

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Hattler catheterMortality

• Quarter of clinical trial patients had adverse
  complications
• 4 out of 64 died as a result of the catheter
• Less than a fifth of catheters were mechanically
  faulty
• Overall a good therapeutic index

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MicroOxygenator Clinical Trials

• Clinical trials on humans not yet done
• Micro- oxygenator used mainly for the mice
  application

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• An important performance index for the
• artificial lungs is the ratio of the priming
• volume to the transfer ratio
• The lower the better

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Questions?