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Author(s): Herbert Spapen [sup.1], Walter Moeyersons [sup.1], Wim Stiers [sup.1], Geert Desmet [sup.1], Emiel Suys [sup.1] Author Affiliations: (1) grid.8767.e, 0000000122908069, Intensive Care Department, University Hospital, Vrije Universiteit Brussels, , [...], Within continuously controlled limits of cuff pressure, an endotracheal tube cuff made of polyurethane (PU) prevents secretion inflow better than a conventional polyvinylchloride cuff. However, the temperature difference between ventilator gas and the air inside a PU cuff produces condensation droplets that accumulate in the cuff inflation canal. We investigated whether condensation influenced continuous cuff pressure monitoring. A PU-cuffed tube was placed into an artificial trachea and connected to a ventilator and test lung. An additional line was inserted at the distal cuff end to directly measure pressure inside the cuff. Methylene blue instillation via the inflation line mimicked condensation. Inspiratory (Pinsp) and expiratory (Pexp) pressures were continuously recorded. Six consecutive experiments were performed comparing pressures at baseline (T0) and at 24 h (T24). Shortly after dye instillation, pressures recorded at the inflation canal became permanently fixed at 25 cmH.sub.2O. In contrast, pressures measured directly in the cuff progressively decreased (mean Pinsp 30 ± 3 vs. 20 ± 2 cmH.sub.2O and mean Pexp 25 ± 0 vs. 12 ± 2 cmH.sub.2O, T0 vs. T24, both P < 0.05). Thus, condensation in the inflation line of a PU-cuffed tube renders continuous cuff pressure monitoring unreliable, thereby increasing the risk for microaspiration.

Background: No currently used tracheal tube offers full protection against aspiration of oropharyngeal secretions into the lower airways.Objective: We developed a tracheal tube equipped with two polyvinylchloride (PVC) cuffs with a supplementary port opening between the cuffs through which a continuous positive pressure of 5 cmH2O is provided [double-cuffed PVC (PVCdc)]. We compared this PVCdc with four different cuff types (cylindrical PVC, conical PVC, cylindrical polyurethane and conical polyurethane).Design: A comparison study using an in-vitro benchtop model of an artificial rigid trachea.Interventions: Tracheal tubes were placed in the artificial trachea. Both cuffs were kept inflated at 25 cmH2O. Total 3 ml dyed water was placed above the cuff and leakage recorded under static and dynamic [5 cmH2O positive end-expiratory pressure (PEEP) alone or positive pressure ventilation plus 5 cmH2O PEEP] conditions. At the end of the dynamic experiments, PEEP was zeroed (PEEP alone) or the tracheal tubes were disconnected from the ventilator (positive pressure ventilation plus PEEP).Results: In the static model, leakage flows [medians (range)] were 9.8 (6.2 to 20) for the cylindrical PVC, 1.3 (0.2 to 3.8) for the conical PVC, 0.03 (0.007 to 0.1) for the cylindrical polyurethane, 0.04 (0.003 to 0.2) for the conical polyurethane and 0.0 (0.0 to 0.0) ml min for the PVCdc cuff (P < 0.001, PVCdc vs. all other cuffs). In the dynamic setting, no leakage was detected for up to 60 min with any of the cuffs studied. Loss of PEEP or tracheal tube disconnection resulted in dye inflow alongside all cuffs except for the PVCdc (P < 0.001, PVCdc vs. all other cuffs).Conclusion: A 'pressure seal' incorporated in a double-cuffed tracheal tube prevented fluid passage into the lower airways. Clinically, this may translate into absence of inflow of bacteriologically contaminated secretions into the lungs and thus a lower incidence of ventilator-associated infection. [ABSTRACT FROM AUTHOR]