Sputtering of micro-carbon-silver film (µC-Ag) for endotracheal tubes to mitigate respiratory infections.

Polyurethane (PU) substrates are biocompatible materials widely used to manufacture endotracheal tubes. However, in common with other biomedical materials, they are liable to the formation of microbial films. The occurrence of pneumonia in intubated patients treated at intensive care units often takes the form of ventilator-associated pneumonia (VAP). The issue relates to the translocation of pathogenic microorganisms that colonize the oropharyngeal mucosa, dental plaque, stomach, and sinuses. New protective materials can provide a more effective therapeutic approach to mitigating bacterial films. This work concerns microcrystalline carbon film containing dispersed silver nanoparticles (µC-Ag) deposited on PU substrates using a physical vapor deposition sputtering process. For the first time, carbon paper was used to produce a carbon target with holes exposing a silver disk positioned under the carbon paper, forming a single target for use in the sputtering system. The silver nanoparticles were well distributed in the carbon film. The adherence characteristics of the µC-Ag film were evaluated using a tape test technique, and electron dispersive x-ray mapping was performed to analyze the residual particles after the tape test. The microbicidal effect of the thin film was also investigated using speciesS. aureus, a pathogenic microorganism responsible for most infections of the lower respiratory tract involving VAP and ventilator-associated tracheobronchitis (VAT). The results demonstrated that µC-Ag films on PU substrates are promising materials for mitigating pathogenic microorganisms on endotracheal tubes.

In vitro 2D PIV measurements and related aperture areas of tricuspid bioprosthetic mitral valves at the beginning of diastole.

PURPOSE: Besides ventricular parameters, the design and angular orientation of a prosthetic heart valve induce a specific flow field. The aim of this study was to know the inflow characteristics of a left ventricular model (LVM), investigating the behavior of tricuspid bioprosthetic mitral valves in terms of velocity profiles and related valve aperture areas at the beginning of diastole, under different conditions. METHODS: 3 heart rates (HRs) were established in the LVM and each mitral bioprosthesis (27 and 31 mm diameter) was installed in 2 orientations, rotated by 180° . For each experimental setup, 2-dimensional particle image velocimetry (2D PIV) measurements and simultaneous mitral valve (MV) area detection were obtained from 50 samples. RESULTS: The results from the velocity profiles immediately downstream of mitral bioprostheses showed the influence of valve orientation for moderate HRs, although for a similar magnitude of mean velocity vectors. The geometries of MV open areas for each HR were similar regardless of valve orientation, except for the 27-mm valve at 90 beats per minute (bpm), and for the 31-mm valve at 60 bpm. Moreover, for each HR, similar percentages of valve open area were obtained regardless of MV nominal diameters. CONCLUSIONS: In conclusion, the experimental setup for the 2D PIV measurements synchronized with the MV area detection was a useful tool for knowing the inflow characteristics of the LVM.