ENDOTRACHEAL TUBES FOR CRITICALLY ILL PATIENTS: AN IN-VIVO ANALYSIS OF ASSOCIATED TRACHEAL INJURY, MUCOCILIARY CLEARANCE AND SEALING EFFICACY.

Improvements in the design of the endotracheal tube (ETT) have been achieved in recent years. We evaluated tracheal injury associated with ETTs with novel high-volume low-pressure (HVLP) cuffs and subglottic secretions aspiration (SSA) and the effects on mucociliary clearance (MCC).Twenty-nine pigs were intubated with ETTs comprising cylindrical or tapered cuffs and made of polyvinylchloride or polyurethane. In specific ETTs, every 2 h SSA was performed. Following 76 h of mechanical ventilation, pigs were weaned and extubated. Images of the tracheal wall were recorded before intubation, extubation and 24 and 96h thereafter, through a fluorescence bronchoscope. We computed the red-to-green intensity ratio (R/G) -an index of tracheal injury- and the green-plus-blue (G+B) intensity -an index of normalcy- of the most injured tracheal regions. MCC was assessed through fluoroscopic tracking of radio-opaque markers. After 96h from extubation, pigs were sacrificed, and a pathologist scored injury.Cylindrical cuffs presented smaller increase in R/G vs. tapered cuffs (p=0.011). Additionally, cuffs made of polyurethane produced a minor increase in R/G (p=0.012) and less G+B intensity decline (p=0.022), vs. polyvinylchloride cuffs. Particularly, a cuff made of polyurethane and with smaller outer diameter outperformed all cuffs. SSA-related histological injury ranged from cilia loss to subepithelial inflammation. MCC was 0.9±1.8 and 0.4±0.9 mm/min for polyurethane and polyvinylchloride cuffs, respectively (p<0.001).HVLP cuffs and SSA produce tracheal injury, and the recovery is incomplete up to 96h following extubation. Small, cylindrical-shaped cuffs made of polyurethane cause less injury. MCC decline is reduced with polyurethane cuffs.