Study objectives: To evaluate the influence of silver-coated endotracheal tubes on the lung bacterial burden of mechanically ventilated dogs.
Design: Randomized, double-blinded, controlled experiment.
Setting: Animal research facility of a regional medical university.
Patients or participants: Eleven healthy adult dogs.
Interventions: The dogs were intubated either with cuffed, noncoated endotracheal tubes or with endotracheal tubes having a novel antimicrobial silver hydrogel coating and were challenged with buccal administration of Pseudomonas aeruginosa.
Measurements and results: The silver coating delayed the appearance of bacteria on the inner surface of the endotracheal tubes ([mean ± SD] duration of mechanical ventilation before appearance of bacteria, 3.2 ± 0.8 days; mean duration of mechanical ventilation, 1.8 ± 0.4 days; p = 0.016). The mean total aerobic bacterial burden in the lung parenchyma was statistically lower among the dogs receiving the silver-coated endotracheal tubes compared to those not receiving them (4.8 ± 0.8 vs 5.4 ± 0.9 log cfu/g lung tissue, respectively; p = 0.010). Pronounced differences were seen in the gross and histologic assessments of inflammation in the lung. Using an increasing severity scale of 0 to 12 to assess four components of histology (ie, hyperemia, edema, cellular infiltration, and bacterial presence), dogs receiving noncoated endotracheal tubes had statistically greater histology scores compared to dogs receiving silver-coated endotracheal tubes (7.1 ± 1.6 vs 2.8 ± 1.2, respectively; p < 0.001).
Conclusion: These results suggest that the silver coating of endotracheal tubes may delay the onset of and decrease the severity of lung colonization by aerobic bacteria. Based on these results, clinical studies are planned to determine the safety and clinical efficacy of silver-coated endotracheal tubes in patients requiring mechanical ventilation in the ICU setting.