Biomedical Engineering Reference
In-Depth Information
1.8 Membrane makeup to a cross-wound knitted mat.
formance can be achieved. Examples for such a technique today are the RX
series oxygenators by Terumo or the Affinity
Õ
model by Medtronic. For such a
technique, quite large amounts of membrane are lost at the edges of the wound
body, where the capillaries change their direction. These are embedded in the
potting material and cut away.
Another method is to make up the membranes on a knitting machine
according to Fig. 1.8, a unique technology by Membrana GmbH, Germany. For
this, the capillaries are knitted to a mat with the parallel capillaries being fixed
with warp threads that are fixed with a knot to the capillary. These mats are cut
to customer-specified widths and then angled, so that warp thread and capillaries
are no longer perpendicular to each other. Two such mats are then superimposed
on each other, so that the capillaries lie X-shaped over each other. This double
layer mat roll can then easily be incorporated into the final device by the
manufacturer. The high packing density and well-defined distances and angles
and the arrangement of the warp threads ensure an ideal mixing of blood around
the capillaries and thus full utilisation of the incorporated surface with
consecutive maximum performance. Oxygenators available with this make-up
technique include those from Sorin, Nipro and the Medos Group.
A similar method is employed by Maquet for their Quadrox
Õ
oxygenators:
these incorporate mat segments that are stacked to a pile in which the mats lie
rectangular to their adjacent layers.
1.2.7 Biocompatibility
For oxygenators used in cardiac surgery, biocompatibility is not as much of an
issue as it is, for example, in haemodialysis: a patient will use an oxygenator
