Gas leakage around cuffed endotracheal tubes and the effect of gel lubrication: in vitro and ex vivo models.

OBJECTIVE

To determine whether inflating high-volume, low-pressure (HVLP) endotracheal tube (ETT) cuffs to 30 cmH2O prevents significant gas leakage (>5 mL) during intermittent positive-pressure ventilation (IPPV) in rigid in vitro and ex vivo porcine tracheal models, and whether ETT cuff lubrication reduces the pressure needed for an effective airway seal.

STUDY

DESIGN

Prospective, randomised, crossover design.

ANIMALS: A group of 20 porcine excised tracheae.

METHODS

Phase 1: In a rigid in vitro tracheal model (PVC tube, 22 mm inner diameter, 30 ° incline) connected to a 1 L test lung delivering IPPV (peak inspiratory pressure 10 cmH2O, 12 breaths minute-1, inspiratory:expiratory ratio 1:3), randomly selected HVLP ETTs (five per size, 7.0-10.0 mm inner diameter) were inserted and cuffs inflated to 30 cmH2O. Gas leakage during IPPV, determined as inspiratory-expiratory volume difference (ΔI-E), was measured 12 times per ETT, before and after water-soluble gel lubrication. Phase 2 replicated the experiments using 20 ex vivo porcine tracheae [20 mm ± 2 mm inner diameter (mean ± standard deviation)]. Finally, minimum cuff pressures required to achieve negligible leakage (≤5 mL) were determined before and after lubrication. Statistical analyses included t-tests, Wilcoxon signed-rank, and Kruskal-Wallis tests, with Conover-Iman post hoc and Bonferroni corrections.

RESULTS

In vitro, median ΔI-E before lubrication was 155 mL (7.0 mm), 77 mL (8.0 mm), 27 mL (9.0 mm), and 20 mL (10.0 mm). Lubrication reduced leakage (p < 0.0001) and cuff pressures by 8.7 ± 10.4 to 22 ± 4.2 cmH2O. Ex vivo, median ΔI-E before lubrication was 22 mL (7.0 mm), 20 mL (8.0 mm), 19 mL (9.0 mm), and 12 mL (10.0 mm). Lubrication reduced leakage (p < 0.0001) and cuff pressures by 3.4 ± 1.5 to 12 ± 9.5 cmH2O. Leakage differed significantly between sizes before and after lubrication (p < 0.0001).

CONCLUSIONS

Inflating HVLP ETT cuffs to 30 cmH2O alone did not reliably prevent gas leakage, but lubrication significantly reduced leakage and the cuff pressure required for an effective airway seal, particularly in smaller ETTs.