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BACKGROUND: The literature generally describes the trachea as oriented toward the right and back, but there is very little detailed characterization. Therefore, the aim of this study was to precisely determine the spatial orientation and to better characterize the physical properties of the human trachea. METHODS: We analyzed lung computed tomography scans of 68 intubated and mechanically ventilated subjects suffering from acute lung injury/ARDS at airway pressures (Paw) of 5, 15, and 45 cm H2O. At each Paw, the inner edge of the trachea from the subglottal space to the carina was captured. Tracheal length and diameter were measured. Tracheal orientation and compliance were estimated from processing barycenter and surface tracheal sections. RESULTS: Tracheal orientation at a Paw of 5 cm H2O showed a 4.2 ± 5.3° angle toward the right and a 20.6 ± 6.9° angle downward toward the back, which decreased significantly while increasing Paw (19.4 ± 6.9° at 15 cm H2O and 17.1 ± 6.8° at 45 cm H2O, P < .001). Tracheal compliance was 0.0113 ± 0.0131 mL/cm H2O/cm of trachea length from 5 to 15 cm H2O and 0.004 ± 0.0041 mL/cm H2O/cm of trachea length from 15 to 45 cm H2O (P < .001). Tracheal diameter was 19.6 ± 3.4 mm on the medial-lateral axis and 21.0 ± 4.3 mm on the sternal-vertebral axis. CONCLUSIONS: The trachea is oriented downward toward the back at a 20.6 ± 6.9° angle and slightly toward the right at a 4.2 ± 5.3° angle. Understanding tracheal orientation may help in enhancing postural drainage and respiratory physiotherapy, and knowing the physical properties of the trachea may aid in endotracheal tube cuff design. [ABSTRACT FROM AUTHOR]

BACKGROUND: A high-volume low-pressure endotracheal tube (ETT) cuff forms folds along its contact with the trachea, allowing mucus leakage into the lungs. We developed a thin-walled ETT cuff made of Lycra polyurethane. METHODS: In vitro, we tested 6 of each of the new prototype Lycra cuff, the Mallinkrodt Hi-Lo ETT (polyvinyl chloride cuff), and the Kimberly-Clark Microcuff ETT (polyurethane cuff), for leakage, in an acrylic mock trachea (inner diameter 20-mm), with a cuff inflation pressure of 20 cm H2O. We poured 15 mL of methylene-blue colored water into the acrylic tube above the cuff and observed for leakage for 24 hours. RESULTS: The Lycra cuffs had no folds upon inflation in the mock trachea and completely prevented fluid leakage for 24 hours (P<.001 vs the Hi-Lo and the Microcuff). The average leakage past the Hi-Lo was 1,182 ± 1,321 mL/h. The average leakage past the Microcuff was 1.2 ± 0.4 mL/h (P < .001 vs the Hi-Lo). CONCLUSIONS: Our Lycra cuff provided complete tracheal sealing in vitro. [ABSTRACT FROM AUTHOR]