Use of siliconised infant endotracheal tubes reduces work of breathing under turbulent flow

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The high resistance of an infant endotracheal tube (ETT) can markedly impair ventilation and gas exchange. Since some manufacturers cover the inner surface of their ETTs with a silicon layer in order to diminish deposition and ease mucous evacuation from airway, via surface roughness decrease, we assessed whether the silicon layer may affect tube resistance, work of breathing and other parameters of ventilation.We compared SUMI (Poland) non-siliconised and siliconised polyvinyl chloride ETTs (2.5, 3.0 and 4.0mm ID), twenty of each type and size combination. Simulating volume-controlled ventilation with the hybrid (numerical–physical) lung models of a premature infant and a 3-month-old baby peak inspiratory pressure (PIP), peak inspiratory and expiratory flow (PIF, PEF), (patient+ETT) inspiratory and expiratory airway resistance (Rins, Rexp) and work of breathing by ventilator (WOBvt) were measured. Additionally, images of the both type surfaces were taken using Hitachi TM-1000 electron microscope.When 2.5 and 3.0mm ID ETTs were examined, laminar flow (Re <2300) across the tube was observed, and there were no clinically significant differences in the ventilation parameters between non-siliconised and siliconised tubes. Whereas, when 4mm ID ETTs were tested, turbulent flow was observed, and PIP, Rins, Rexp and WOBvt were significantly lower (5%, 17%, 17%, and 7%, respectively) (P<0.05), but PIF and PEF were significantly higher (8%, 14%) (P<0.05). Thus, the silicone inner surface of ETT offers less resistance and WOBvt in presence of turbulent flow. However, artifacts observed on the surface of non-siliconised and siliconised ETTs can potentially impair ventilation.