Prevention of Lung Bacterial Colonization With a Leak-Proof Endotracheal Tube Cuff: An Experimental Animal Study

Abstract

Background: Endotracheal tubes with standard polyvinyl chloride cuffs create folds on inflation into the trachea, which lead to potential leakage of subglottic secretions into the lower airways and cause lung colonization and pneumonia. The use of a double-layer prototype leak-proof cuff has shown effective prevention of the fluid leakage across the cuff. We hypothesized that the use of such a leak-proof cuff could prevent lung bacterial colonization in vivo.

Methods: To simulate patients in the ICU, 13 pigs were placed in the semirecumbent position, intubated, and mechanically ventilated for 72 h. Five animals were prospectively intubated with an endotracheal tube with a leak-proof cuff (leak-proof cuff group). Data from 8 animals previously intubated with an endotracheal tube with a standard polyvinyl chloride cuff (standard cuff group) were retrospectively analyzed. Leakage of tracheal secretions across the leak-proof cuff was tested by the macroscopic methylene blue evaluation. Arterial blood gas exchanges and microbiology were tested in all the pigs at necropsy.

Results: In the standard cuff group, all the pigs showed heavy bacterial colonization of the lungs after 72 h of mechanical ventilation, with an overall proportion of colonized lung lobes of 92% (44/48 lobes, 8/8 animals) compared with 27% (8/30 lobes, 5/5 animals) in the leak-proof cuff group (P < .001). These results were strengthened by the absence of methylene blue in the tracheal secretions below the leak-proof cuff. Furthermore, no hypoxemia was demonstrated in the pigs in the leak-proof cuff group after the 72-h experiment (P_aO2 /F_IO2 change from baseline, leak-proof cuff group vs standard cuff group; median difference 332, 95% CI 41-389 mm Hg; P = .030).

Conclusions: A new leak-proof cuff for endotracheal intubation prevented macroscopic leakage of subglottic secretions along the airways. This mechanism led to the reduction of lung bacterial colonization, which could contribute to the prevention of hypoxemia in the pigs on mechanical ventilation while in the semirecumbent position.

Keywords: acute hypoxemic respiratory failure; bacterial colonization; endotracheal tube cuff; ventilator-associated pneumonia.

Fig. 1.

Prototype experimental leak-proof cuff. A layer of highly compliant guayule latex (dotted line) is draped around a standard high-volume low-pressure polyvinyl chloride cuff (dashed line). A sterile gel was added between the 2 cuffs.

Fig. 2.

Study design.

Fig. 3.

Description of the 6 sampling sites for microbiologic evaluation along the lungs.

Fig. 4.

Blood gas analysis and physiologic variables changes over time (from baseline to 72 h) among the standard cuff group and leak-proof cuff group. A: P_aO2/ F_IO2. B: P_aCO2. C: Arterial pH. D: Respiratory system plateau pressure (Ppl,rs). E: Breathing frequency. F: Mean arterial pressure. Continuous variables are graphically expressed as individual data (dots), box plots (median [interquartile range]) with whiskers (range, minimum-maximum). P values (2-tailed) compared groups on the mean change from baseline and were calculated with 2-way analysis of variance for repeated measurements over time.

Fig. 5.

Median of bacterial colonization (CFU/g) in the standard cuff group (A) and in the leak-proof cuff group (B) by location into the lung lobes.