Critical Care |

Condensation of Humidified Air in the Inflation Line of a Polyurethane-Cuffed Endotracheal Tube During Mechanical Ventilation Causes False Continuous Cuff Pressure Readings FREE TO VIEW

Herbert Spapen, PhD; Walter Moeyersons, RN; Wim Stiers; Emiel Suys, RN
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University Hospital Brussels, Brussels, Belgium

Chest. 2014;145(3_MeetingAbstracts):175A. doi:10.1378/chest.1782961
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SESSION TITLE: Critical Care Posters II

SESSION TYPE: Poster Presentations

PRESENTED ON: Saturday, March 22, 2014 at 01:15 PM - 02:15 PM

PURPOSE: Adequate tracheal sealing is imperative to avoid leakage of subglottic secretions into the lower airways during mechanical ventilation and thus to prevent ventilator-associated pneumonia (VAP). Within acceptable upper limits of cuff pressure (i.e. 25cmH2O), an endotracheal tube (ETT) cuff made of ultrathin polyurethane prevents secretion inflow better than a conventional polyvinylchloride cuff. However, the temperature difference between ventilator gas and air inside a polyurethane cuff has been shown to produce condensation drops which may occlude the inflation line. We investigated whether this condensation process affected continuous cuff pressure monitoring and adjustment.

METHODS: A polyurethane-cuffed ETT was inserted in an artificial trachea and connected to a ventilator and test lung. The cuff inflation line was connected to a device that continuously measured and automatically adjusted cuff pressure. An additional line was artificially inserted at the distal end of the cuff. Both the inflation and additional lumen were connected to a pressure transducer for direct independent pressure registration. Cuff pressure was set at 25cmH2O and positive pressure ventilation initiated. Aspiration of 5cc air from the additional line (i.e. mimicking cuff deflation) resulted in immediate automatic correction of intracuff pressure to 25cmH2O. Subsequently, a methylene blue drip was started via the inflation line to mimic condensation (T0). Inspiratory (Pinsp) and expiratory (Pexp) cuff pressures were recorded for 24h (T24). Five consecutive experiments were performed.

RESULTS: From onset of dye instillation, in- and expiratory cuff pressures recorded at the inflation canal became permanently fixed at 25cmH2O. In contrast, pressures measured directly in the cuff progressively decreased over time (Pinsp 30 ± 3 vs. 20 ± 2 cmH2O and Pexp 25 ± 0 vs. 12 ± 2 cmH2O, T0 vs T24, both P<0.05).

CONCLUSIONS: Condensation in the inflation line of a polyurethane-cuffed ETT caused significant overestimation of true intracuff pressure and impeded automatic cuff pressure adjustment.

CLINICAL IMPLICATIONS: Unsuspected cuff deflation may expose ICU patients intubated with a polyurethane-cuffed ETT to VAP and promote accidental extubation.

DISCLOSURE: The following authors have nothing to disclose: Herbert Spapen, Walter Moeyersons, Wim Stiers, Emiel Suys

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