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Enteral nutrition
Published in David Westaby, Martin Lombard, Therapeutic Gastrointestinal Endoscopy A problem-oriented approach, 2019
A bewildering variety of tubes have arrived on the market in recent years, but they differ from one another in only a few important respects: tube diameter, the materials from which they are made, the external fixing device and, most important, the type of internal retention device used. In general, thinner diameter tubes (down to 9 F) have a similar blockage rate to larger ones and are preferred for their better tolerability. The choice of material is chiefly between silicone elastomers and polyurethane. The former is softer, but such a tube has a larger external diameter in relation to its lumen. Both materials are durable; polyurethane tends to split if left kinked for long periods, whereas silicon can become stretched and distorted with time. Experience with polyurethane tubes indicates that they can last up to 6 years. External fixation is achieved with either a simple disc or a more sophisticated device which positions the tube at a 90° angle, keeping it flat against the abdominal wall.
Oils
Published in Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters, Cosmetic Formulation, 2019
Fabricio Almeida de Sousa, Vânia Rodrigues Leite-Silva
Volatile silicones provide transient effects characterised by slight lubricity, a light texture, fast spreading, and good distribution of the product application, while leaving no residual effects. They are often included in formulations to remove the greasy or oily feel of hydrocarbon-based emollients and are the basis for ‘oil free’–type claims (De Backer and Ghirardi, 1993). Silicone elastomers are used to give a dry, powdery feel to skin care formulations (Van Reeth and Starch, 2003).
Operative venous thrombectomy
Published in Sachinder Singh Hans, Alexander D Shepard, Mitchell R Weaver, Paul G Bove, Graham W Long, Endovascular and Open Vascular Reconstruction, 2017
Anthony J. Comerota, Rodrigo Ruiz-Gamboa
If the infrainguinal thrombus persists, one option for thrombus removal is to use an over-the-wire balloon thrombectomy catheter. First, a hydrophilic guidewire needs to be advanced antegrade through the valves and down to the tibial veins. If a guidewire cannot be passed through the infrainguinal valves, a cutdown is performed to expose the distal posterior tibial vein (PTV). Alternatively, this can also be done by cannulating the tibial vein under US guidance. A No. 3 Fogarty catheter is advanced from the distal PTV to and through the CFV venotomy. The silicone elastomer stem of an intravenous catheter (12-14 G) is amputated from its hub and slid halfway onto the balloon catheter. Another balloon catheter (No. 4 Fogarty) is placed at the opposite end of the silicone elastomer sheath (Figure 58.1a). Pressure is applied to the two balloons by a single operating surgeon to ensure that the catheters remain secure inside the sheath. The No. 4 Fogarty balloon catheter is guided distally through the thrombosed venous valves and clotted veins (Figure 58.1b) to the level of the posterior tibial venotomy (Figure 58.1c). Thrombectomy is performed and repeated as necessary. Alternatively, if an over-the-wire balloon thrombectomy catheter is available, a guidewire can be passed proximally from the distal PTV and the infrainguinal thrombectomy is performed (Figure 58.1d,e).
Implantable medical devices for tendon and ligament repair: a review of patents and commercial products
Published in Expert Review of Medical Devices, 2022
Marco Civera, Ester Devietti Goggia, Matteo De Ros, Vito Burgio, Federica Bergamin, Mariana Rodriguez Reinoso, Cecilia Surace
Another key component is silicone. Silicones are highly versatile materials, suitable for various industries and applications, due to their high elasticity, biocompatibility, easy processability and chemical inertness [64]. They are synthetic polymers, commonly obtained in the form of a linear chain made of polydimethylsiloxane (PDMS). Highly crosslinked silicones or gel-like silicones are nowadays used in medical implants. Silicone elastomers are considered as a material of choice for orthopaedic prostheses and finger joints [64]. Nevertheless, they are insufficiently exploited for use inside the human body, especially for long-term implantation of prostheses, valves etc. The risk of rupture of a silicone implant is associated with degradation processes, as a consequence of multiple causes: autoimmune response due to the microorganisms present in the implantpenetration of lipids into the polymer networkmechanical loading during daily activities
Protocol with non-toxic chemicals to control biofilm in dental unit waterlines: physical, chemical, mechanical and biological perspective
Published in Biofouling, 2022
Rachel Maciel Monteiro, Viviane de Cassia Oliveira, Rodrigo Galo, Denise de Andrade, Ana Maria Razaboni, Evandro Watanabe
The observed increase in microhardness and surface roughness of the polyurethane samples could be implicated in a reduction of waterline natural flexibility and durability and in facilitating bacterial adhesion (Goiato et al. 2012; Ammar et al. 2015). The scientific literature is not conclusive regarding the effect of repeated cycles of chemical disinfection on polyurethane surfaces. On resin acrylic surfaces, the repeated application of cleansers caused an increase in surface roughness and microhardness and reduction of flexural strength (Paranhos et al. 2013; Rocha et al. 2021). In agreement with the findings reported here, Goiato et al. (2012) demonstrated that chemical disinfection increased the Shore A microhardness of a silicone elastomer. These results support the periodical replacement, of dental unit waterlines, as repeated disinfection can damage the waterline and favor biofilm formation. Furthermore, these typical dental unit water systems do not allow mechanical cleaning with a brush, for example, due to the very small internal diameters of about 0.5 mm and high lengths of 10 m or more (Mills 2003).
The development of a silicone vaginal ring with a prostaglandin analogue for potential use in the treatment of canine reproductive disorders
Published in Pharmaceutical Development and Technology, 2019
Veronika Nováková Tkadlečková, Jakub Vysloužil, Kateřina Kubová, Jan Elbl, Darja Bučková, Jan Muselík, David Vetchý, Robert Novotný, Pavel Proks, Josef Jančář, Petr Poláček
To investigate in vitro release behaviour of sparingly soluble model drug CA (Agyemang-Yeboah and Oppong 2013) from the matrix-type VR in the presence of various channel-forming substances for achieving the 72-h in vitro dissolution profile, silicone flat discs containing 100 mg of CA (particle size of 125–250 µm) were prepared from model silicone Sylgard® 164 (two-part silicone elastomer, mixed 1:1). The base of the silicone elastomer was mixed with CA or the mixture of CA and channel-forming excipient. After the addition of the catalyst, the mixture was poured into the cylindrical plastic mould prepared on the Rebel II 3 D printer (diameter 30 mm, height 2.3 mm, approx. weight of discs 2300 mg) and the discs were cured for 15 min at room temperature (the curing time was recommended by the producer). The composition of the flat discs (the set SYL) is shown in Table 1. Each composition was tested for weight uniformity according to Ph. Eur. 9 (the deviation ± 5% was chosen as acceptable and in accordance with the deviation used for vaginal pessaries, which have a comparable weight).