An Individual Barrier Enclosure Actively Removing Aerosols for Airborne Isolation: A Vacuum Tent.

BACKGROUND: Aerosol barrier enclosure systems have been designed to prevent airborne contamination, but their safety has been questioned. A vacuum tent was designed with active continuous suctioning to minimize risks of aerosol dispersion. We tested its efficacy, risk of rebreathing, and usability on a bench, in healthy volunteers, and in an ergonomic clinical assessment study. METHODS: First, a manikin with airway connected to a breathing simulator was placed inside the vacuum tent to generate active breathing, cough, and CO2 production; high-flow nasal cannula (HFNC) was applied in the manikin's nares. Negative pressure was applied in the vacuum tent's apex port using wall suction. Fluorescent microparticles were aerosolized in the vacuum tent for qualitative assessment. To quantify particles inside and around vacuum tent (aerosol retention), an airtight aerosol chamber with aerosolized latex microparticles was used. The vacuum tent was tested on healthy volunteers breathing with and without HFNC. Last, its usability was assessed in 5 subjects by 5 different anesthesiologists for delivery of full anesthesia, including intubation and extubation. RESULTS: The vacuum tent was adjusted until no leak was visualized using fluorescent particles. The efficacy in retaining microparticles was confirmed quantitatively. CO2 accumulation inside the vacuum tent showed an inverse correlation with the suction flow in all conditions (normal breathing and HFNC 30 or 60 L/min) in bench and healthy volunteers. Particle removal efficacy and safe breathing conditions (CO2, temperature) were reached when suctioning was at least 60 L/min or 20 L/min > HFNC flow. Five subjects were successfully intubated and anesthetized without ergonomic difficulties and with minimal interference with workflow and an excellent overall assessment by the anesthesiologists. CONCLUSIONS: The vacuum tent effectively minimized aerosol dispersion. Its continuous suction system set at a high suction flow was crucial to avoid the spread of aerosol particles and CO2 rebreathing.

Sequential Functionalization of a Natural Crosslinker Leads to Designer Silicone Networks.

Precise silicone networks are difficult to prepare from multiple starting materials because of poor spatial control over crosslink location, competing side reactions, and incompatible catalysts among other reasons. We demonstrate that cure processes catalyzed by B(C6 F5 )3 (the Piers-Rubinsztajn reaction) and platinum-catalyzed hydrosilylation are perfectly compatible, and can be used in either order. It is possible to perform three different, selective, sequential reactions in the same pot using H-terminated silicones as chain extenders in all cases to give explicit networks. Eugenol, a readily available aromatic compound, acts as a trifunctional crosslinker (HO, MeO, HC=CH2 ), each functional group of which can be induced to undergo selective reaction. With platinum catalysis, the reaction of SiH groups with alkenes is fastest, while B(C6 F5 )3 catalyzes reaction at phenols much faster than methoxybenzene. Thus, a variety of H-terminated telechelic siloxanes can be used to form chain extended polymers or elastomers or foams in which the morphology of the material and its constituent parts can be manipulated at will.