Biomedical Engineering Reference
In-Depth Information
by the growth due to increasing civilisation diseases in developed countries and
by the expansion of demanding and costly cardiac surgery in developing
countries.
The application of a long(er) term artificial lung is much more lively. Here a
device is needed that can oxygenate blood and remove carbon dioxide with as
reduced blood trauma as possible for many consecutive days. Such devices have
entered the market in the recent past years. Membranes with a dense outer skin,
such as the OXYPLUS
Õ
membrane from PMP, function for several weeks with
no breakdown, like the Novalung device.
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The obstacles to overcome here are
rather in the prevention haemolysis and that of clotting and deposition of, for
example, fibrin, then on the side of the membrane.
In the 1980s and 1990s, several mathematical models have been established
to describe mass transfer in oxygenators, e.g. by Mockros.
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With today's tools,
mathematical modelling of oxygenators is possible. Theoretically, today we can
calculate the ideal form of an oxygenator at the given parameters of volume,
shear stress, surface area, etc. However, although several such models are being
developed,
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differences between theory and experiment seem to prohibit the
widespread use of these approaches.
Alternative technologies such as bioartificial lungs with live cells are today
nothing but a dream. Research with live endothelial and alveolar cells is going
on, but it will take years, if not generations, of research to develop a live
alternative to the current artificial lungs.
The outlook for plasmapheresis similarly does not focus on the membranes,
as these are readily available. The technology to produce plasma separation
membranes is there, as is the technology to manufacture plasma separators out
of these. The field where we will see developments in the next few years is that
of clinical application. Evidence for the effectiveness and efficiency of plasma-
pheresis for various diseases will have to be collected and documented. In this
course, the consecutive steps after the separation of blood plasma and blood
cells will have to be improved. This will involve affinity and adsorption
techniques for the selective removal of pathogens from plasma. With this
evidence, plasma separation therapies can become more widespread.
1.6
Abbreviations
A
surface area
a
1
, a
2
activities
C
concentration
d
distance (of diffusion)
d
p
diameter of pore
EMO
extracorporeal membrane oxygenation
ETO
ethylene oxide
i.d.
inner diameter
