Optimierung und Weiterentwicklung von dOFM-Setztechnik und dOFM-Kathetern

During drug approvals, the dermal open-flow microperfusion (dOFM) can be used as an alternative to microdialysis, to quantify pharmacokinetics and pharmacodynamics of large-molecular substances in the dermis. Therefore a braid catheter is implanted into the dermis, possibly causing trauma and immune reactions. The aim of this thesis was the development of verification concepts for the optimization of the existing implantation and explantation process, also in respect of new polymer catheters.
Penetration forces of needles and cannulae during implantation were determined in-vitro in synthetic skin and in-vivo in pig skin. In addition, different needles and cannulae were subjectively evaluated during insertion by a physician regarding their insertion comfort. For evaluation of the explantation and risk assessment, necessary forces during explantation of the dOFM catheters and their tensile strength have been determined.
The majority of the tested needles and cannulae showed lower forces than the current standard cannula during the implantation process. Accordance between insertion force
and comfort could not be found. The braid catheters, compared to PEEK catheters, showed doubled tensile strength, being determined by size of exchange area and catheter diameter.
Tested alternative needles and cannulae showed reduced insertion forces accompanied by insufficient stability. Therefore to reduce trauma, a change of the standard
cannula used is unlikely in the near future. New PEEK catheters showed a 2- to 4-fold reduced tensile strength compared to braid catheters. For this reason, it would be necessary to examine other geometries, insertion gadgets or alternative materials and coatings.