title: Spatial orientation and mechanical properties of the human trachea: a computed tomography study.
abstract: 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.
authors.affiliation: Dipartimento di Scienze della Salute, Università di Milano-Bicocca, Ospedale San Gerardo Nuovo dei Tintori, Monza, Italy. National Institutes of Health, National Heart, Lung, and Blood Institute, Bethesda, Maryland. zanella.alb@gmail.com.
authors.forename: Alberto
authors.initials: A
authors.lastname: Zanella
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy. National Institutes of Health, National Heart, Lung, and Blood Institute, Bethesda, Maryland.
authors.forename: Massimo
authors.initials: M
authors.lastname: Cressoni
authors.affiliation: Dipartimento di Scienze della Salute, Università di Milano-Bicocca, Ospedale San Gerardo Nuovo dei Tintori, Monza, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Ferlicca
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Chiurazzi
authors.affiliation: National Institutes of Health, National Heart, Lung, and Blood Institute, Bethesda, Maryland.
authors.forename: Myra
authors.initials: M
authors.lastname: Epp
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Rovati
authors.affiliation: Dipartimento di Anestesia, Rianimazione (Intensiva e Subintensiva) e Terapia del Dolore, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Chiumello
authors.affiliation: Dipartimento di Scienze della Salute, Università di Milano-Bicocca, Ospedale San Gerardo Nuovo dei Tintori, Monza, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pesenti
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy. Dipartimento di Anestesia, Rianimazione (Intensiva e Subintensiva) e Terapia del Dolore, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
authors.affiliation: National Institutes of Health, National Heart, Lung, and Blood Institute, Bethesda, Maryland.
authors.forename: Theodor
authors.initials: T
authors.lastname: Kolobow
mesh_terms: D000328:Adult; D000368:Aged; D001837:Body Weights and Measures; D005260:Female; D005931:Glottis; D006801:Humans; D007442:Intubation, Intratracheal; D055370:Lung Injury / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000503:physiopathology; D013249:Sternum; D014057:Tomography, X-Ray Computed; D014132:Trachea / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*
keywords: trachea anatomy; trachea orientation