PubMed Health⌕ Search

Biomedical subjects

W Lemm

Publications and source records attributed to W Lemm.

4 recordsLinked to original sources
PubMed1991

A new in vitro thrombogenicity test for medical tubes.

Basic information on the affected coagulation behaviour of healthy human blood passing foreign artificial surfaces is of immense importance for a safe clinical therapy. An in vitro screening method is presented which tests the thrombogenicity of medical tubes, applying the clinically already established resonance thrombography (RTG). Several medical tubes with various types and contents of plasticizers are tested and compared with materials free of additives. The effect of the release of ingredients is indicated by this procedures, as well as the influence of a sterilizing treatment with gamma-radiation on the physical surface properties, such as smoothness. In all cases, the modified RTG method proves its suitability and sensitivity. In addition, this method allows accurate adjustment of the extrusion parameters for tube manufacturers.

Blood Coagulation Tests↗
PubMed1989

Biostability of polyurethanes.

Aside from the medical requirements a material has to fulfill to qualify as biocompatible, for the bioengineer, who is involved in the design, construction and fabrication of prosthetic devices, the mechanical, physical and chemical properties of the material as well as its possible manufacturing procedures and, last but not least, its biostability are of the same importance. In the very aggressive biological environment, the material should behave inertly, showing no surface erosions, molecular chain disruptions, uptake of low molecular weight biological materials, local chemical imbalances, tendency to calcification or negative changes of mechanical properties. With regard to this aspect, different polyurethanes have been evaluated in-vitro and in-vivo as basic materials and already fabricated devices (blood pumps and heart valves). The comparison of the results stresses the necessity of further efforts to achieve a standardized test protocol for the prove of the biostability of polymers, containing appropriate, well-defined in-vitro and in-vivo test methods to establish the necessary data basa for the materials' clinical approval.

Animals↗