Variables affecting leakage past endotracheal tube cuffs: a bench study

Leakage of oral secretions past endotracheal tubes (ETT) has been implicated in ventilator associated pneumonia. The aim of this bench study was to compare the ability of current generation ETT cuffs to prevent fluid leakage and to determine the specific mechanical ventilator settings that affect movement of fluid across an inflated ETT cuff.

Using a 2.3-cm internal diameter (ID) tracheal model and simulated ventilatory support, we evaluated the impact of cuff pressure (20 and 30 cmH(2)O), positive end-expiratory pressure/continuous positive airway pressure (PEEP/CPAP, 0-15 cmH(2)O), peak inspiratory pressure (PIP, 15-45 cmH(2)O), and mode of ventilation (volume control, volume assist/control, pressure control, pressure assist/control, and CPAP) on leakage of fluid past the ETT cuffs of 16 ETTs. The tracheal model was configured in the vertical position with 35 ml of vitaminwater(®) on top of the inflated ETT cuff and mechanically ventilated. Fluid leakage past the cuff was determined by calculating the volume change in the tracheal model after each 30-min ventilation period. Initially five 8.0-mm-ID ETTs of each manufacturer type were evaluated at baseline ventilator settings. Tubes allowing a consistent leak within two SD of the mean leakage for the five tubes were numbered in consecutive order. A single tube from this group was then randomly selected for detailed evaluation.

Cuff leakage varied among ETT types (p < 0.0001); median leak volume 6.0 ml (0.6-15.1) across all tubes under all conditions. Cuff leakage was inversely related to PEEP level, cuff pressure, and PIP except when PEEP was set at 15 cmH(2)O (all p < 0.0001). In addition, cuff leak varied among modes (p = 0.035).

Cuff leakage varies greatly among ETT types and is affected by cuff pressure, PEEP, PIP, and mode.