title: Upper airway modifications in head extension during development.
abstract: BACKGROUND
  One of the requirements of laryngoscopy is to determine which head position will result in optimal visualization. Our hypothesis was that parameters derived from magnetic resonance imaging (MRI) can help quantify the effect of age on airway modifications due to head extension during development.
  
  
  METHODS
  In children undergoing planned MRI, additional sequences on the upper airways were performed: one in a near-neutral position, the other with the head extended at 35°. The axis of the face, the pharynx, the larynx, the trachea, and the line of glottic visualization were determined. The following angles were calculated: the Visu-Lar angle, formed by the line of glottic visualization and the laryngeal axis, and the Phar-Lar angle, formed by the pharyngeal and laryngeal axes.
  
  
  RESULTS
  One hundred and fifty-five patients (1 to 222 months of age [25-145] months) were included and 54% were under general anaesthesia. Age had no effect on the variation in the Visu-Lar angle, which diminished as a function of head extension, nor on the variation in the Phar-Lar angle, which was minimal in the neutral position. During extension, anatomical axes rotated similarly, and the visualization axis rotated the most, followed by the pharyngeal and laryngeal axes. These results were not correlated with general anaesthesia.
  
  
  CONCLUSIONS
  Regardless of age, head extension diminished the Visu-Lar angle, and increased the Phar-Lar angle. This study supports that, as in adults, head extension is probably the key factor for good visualization conditions during laryngoscopy on children, but clinical data is needed to confirm this result.
authors.affiliation: Department of Anesthesia and Intensive Care, Hôpital d'Instruction des Armées Laveran, 34, boulevard Laveran, 13013 Marseille, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Bécret
authors.affiliation: Department of Anesthesia and Intensive Care, Pediatric and Neonatal Intensive Care Unit, Hôpital Nord, Assistance-Publique des Hôpitaux de Marseille, chemin des Bourrely, 13015 Marseille, France. Electronic address: renaud.vialet@ap-hm.fr.
authors.forename: Renaud
authors.initials: R
authors.lastname: Vialet
authors.affiliation: Medical Imaging Department, Hôpital Nord, Assistance-Publique des Hôpitaux de Marseille, chemin des Bourrely, 13015 Marseille, France.
authors.forename: Kathia
authors.initials: K
authors.lastname: Chaumoitre
authors.affiliation: Public Health Department, Self-Perceived Health Assessment Research Unit, School of Medicine, 27, boulevard Jean-Moulin, 13005 Marseille, France.
authors.forename: Anderson
authors.initials: A
authors.lastname: Loundou
authors.affiliation: Clinical Investigations Center, Hôpital Nord, Assistance-Publique des Hôpitaux de Marseille, chemin des Bourrely, 13015 Marseille, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lesavre
authors.affiliation: Department of Anesthesia and Intensive Care, Pediatric and Neonatal Intensive Care Unit, Hôpital Nord, Assistance-Publique des Hôpitaux de Marseille, chemin des Bourrely, 13015 Marseille, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Michel
mesh_terms: D000375:Aging; D058109:Airway Management / Q000379:methods*; D000768:Anesthesia, General; D002648:Child; D002675:Child, Preschool; D005260:Female; D006257:Head; D006801:Humans; D007442:Intubation, Intratracheal; D007828:Laryngoscopy / Q000379:methods; D007830:Larynx / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D056888:Patient Positioning / Q000379:methods*; D010614:Pharynx / Q000033:anatomy & histology; D012137:Respiratory System / Q000033:anatomy & histology* / Q000254:growth & development*
keywords: Anaesthesiology; Growth variation; Intubation; Magnetic resonance